U.S. patent application number 17/083582 was filed with the patent office on 2022-08-04 for canister apparatus and/or fuel rack for storing and/or transporting spent nuclear fuel.
The applicant listed for this patent is Holtec International. Invention is credited to Stephen J. AGACE, Krishna P. SINGH.
Application Number | 20220246321 17/083582 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-04 |
United States Patent
Application |
20220246321 |
Kind Code |
A9 |
SINGH; Krishna P. ; et
al. |
August 4, 2022 |
CANISTER APPARATUS AND/OR FUEL RACK FOR STORING AND/OR TRANSPORTING
SPENT NUCLEAR FUEL
Abstract
An apparatus for supporting radioactive fuel assemblies, such as
spent nuclear fuel. In one aspect, the apparatus is in the form of
a fuel rack having adjustable height pedestals. In another aspect,
the apparatus is a canister including a first pressure vessel
forming a first cavity and a second pressure vessel forming a
second cavity, the first pressure vessel located in the second
cavity of the second pressure vessel. An inner surface of the
second pressure vessel may be in continuous surface contact with an
outer surface of the first pressure vessel to form a dual-walled
canister.
Inventors: |
SINGH; Krishna P.; (Jupiter,
FL) ; AGACE; Stephen J.; (Voorhees, NJ) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Holtec International |
Camden |
NJ |
US |
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20210225540 A1 |
July 22, 2021 |
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Appl. No.: |
17/083582 |
Filed: |
October 29, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16002325 |
Jun 7, 2018 |
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17083582 |
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14590506 |
Jan 6, 2015 |
10026514 |
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16002325 |
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13418930 |
Mar 13, 2012 |
8929504 |
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14590506 |
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11851352 |
Sep 6, 2007 |
8135107 |
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13418930 |
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15671830 |
Aug 8, 2017 |
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11851352 |
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14072672 |
Nov 5, 2013 |
9728284 |
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15671830 |
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12260914 |
Oct 29, 2008 |
8576976 |
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14072672 |
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16442892 |
Jun 17, 2019 |
10939787 |
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12260914 |
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15642826 |
Jul 6, 2017 |
10446285 |
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16442892 |
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13731803 |
Dec 31, 2012 |
9728286 |
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15642826 |
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12024071 |
Jan 31, 2008 |
8345813 |
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13731803 |
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60842868 |
Sep 6, 2006 |
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60983566 |
Oct 29, 2007 |
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61038525 |
Mar 21, 2008 |
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60887505 |
Jan 31, 2007 |
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International
Class: |
G21F 5/012 20060101
G21F005/012; G21F 5/005 20060101 G21F005/005; G21F 5/008 20060101
G21F005/008; G21F 5/10 20060101 G21F005/10; G21F 5/00 20060101
G21F005/00; G21F 5/12 20060101 G21F005/12 |
Claims
1.-110. (canceled)
111. A fuel rack for supporting spent nuclear fuel assemblies
comprising: a base plate having a top surface; a fuel rack body
extending upward from the base plate and comprising a plurality of
cells, each of the cells having an open top end and being
configured to receive a spent nuclear fuel assembly, and wherein
for each of the cells, a portion of an upper surface of the base
plate forms a floor of the cell; a plurality of adjustable height
pedestals connected to a bottom surface of the base plate, each of
the adjustable height pedestals comprising: a block having a hole
defined by a threaded inner surface, the block fixedly coupled to
the base plate; a peg having a threaded outer surface, the threaded
outer surface of the peg threadily engaged to the threaded inner
surface of the block; an engagement element in a top surface of the
peg; and wherein upon a tool engaging the engagement element and
rotating the peg, the extent the peg protrudes from a bottom
surface of the block is adjusted; and wherein for each of the
adjustable height pedestals, the adjustable height pedestal is
coupled to the base plate so that the engagement element is aligned
with and is accessible via a hole in the floor of one of the
cells.
112. The fuel rack of claim 111 wherein the engagement element
comprises a non-circular depression.
113. The fuel rack of claim 111 wherein the fuel rack body
comprises a plurality of cutouts adjacent the base plate that
provide lateral passageways into the cells.
114. A canister apparatus for storing and/or transporting spent
nuclear fuel rods comprising: a first pressure vessel comprising a
first shell forming a first cavity for receiving spent nuclear fuel
rods, a first plate connected to the first shell so as to enclose a
first end of the first cavity, and a first lid connected to the
first shell so as to enclose a second end of the first cavity; a
second pressure vessel comprising a second shell forming a second
cavity, a second plate connected to the second shell so as to
enclose a first end of the second cavity, and a second lid
connected to the second shell so as to enclose a second end of the
second cavity; and the first pressure vessel located within the
second cavity so that an inner surface of the second shell is in
substantially continuous surface contact with an outer surface of
the first shell.
115. The canister apparatus of claim 114 further comprising a fuel
basket positioned within the first cavity for supporting a
plurality of spent nuclear fuel rods.
116. The canister apparatus of claim 114 wherein the first shell
and the second shell are constructed of a metal.
117. The canister apparatus of claim 116 wherein the substantially
continuous surface contact is achieved by an explosive joining, a
cladding process, a roller bonding process, a mechanical
compression process, or a combination thereof.
118. The canister apparatus of claim 116 wherein the first shell is
made of a metal having a first coefficient of thermal expansion and
the second shell is made of a metal having a second coefficient of
thermal expansion, wherein the first coefficient of thermal
expansion is equal to or greater than the second coefficient of
thermal expansion.
119. The canister apparatus of claim 114 further comprising: an
inner surface of the second plate being in substantially continuous
surface contact with an outer surface of the first plate; and an
inner surface of the second lid being in substantially continuous
surface contact with an outer surface of the first lid.
120. The canister apparatus of claim 114 further comprising: the
first shell, the first plate, the first lid, the second shell, the
second plate and the second lid constructed of a metal; and all
connections between the first shell, the first plate and the first
lid are accomplished via through-thickness welds; and all
connections between the second shell, the second plate and the
second lid are accomplished via through-thickness welds.
121. The canister apparatus of claim 114 further comprising: the
first pressure vessel having an outer surface and the second
pressure vessel having an inner Surface; and wherein the entirety
of the outer surface of the first pressure vessel is in
substantially continuous surface contact the inner surface of the
second pressure vessel.
122. The canister apparatus of claim 114 further comprising: the
first shell having a first edge, a second edge and a first axial
length; the second shell having a first edge, a second edge and a
second axial length that is greater than the first axial length;
and the first pressure vessel positioned within the second cavity
so that the first and second edges of the second shell extend
beyond the first and second edges of the first shell
respectively.
123. The canister apparatus of claim 114 further comprising: a
plurality of elongated tubes located within the first cavity; and
each of the elongated tubes comprising a tubular body forming a
space for receiving spent nuclear fuel rods and a ventilated cap
having at least one hole forming a passageway from the first cavity
into the space.
124. The canister apparatus of claim 114 further comprising a
plurality of poison rods located within the first cavity between
the elongated tubes.
125. The canister apparatus of claim 114 wherein the first and
second shells are cylindrical and constructed of metal.
126. The canister apparatus of claim 114 wherein the first cavity
comprises an inert gas atmosphere.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] The present application is a continuation-in-part of U.S.
patent application Ser. No. 16/002,325, filed Jun. 7, 2018, which
is a divisional of U.S. patent application Ser. No. 14/590,506
filed Jan. 6, 2015, now U.S. Pat. No. 10,026,514, which is a
divisional of U.S. patent application Ser. No. 13/418,930, filed
Mar. 13, 2012, now U.S. Pat. No. 8,929,504, which is a divisional
of U.S. patent application Ser. No. 11/851,352, filed Sep. 6, 2007,
now U.S. Pat. No. 8,135,107, which claims priority to U.S.
Provisional Patent Application Ser. No. 60/842,868, filed Sep. 6,
2006.
[0002] The present application is a continuation-in-part of U.S.
patent application Ser. No. 15/671,830, filed Aug. 8, 2017, which
is a continuation application of U.S. patent application Ser. No.
14/072,672, filed Nov. 5, 2013, now U.S. Pat. No. 9,728,284, which
in turn is a continuation application of U.S. patent application
Ser. No. 12/260,914, filed Oct. 29, 2008, now U.S. Pat. No.
8,576,976, which in turn claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/983,566, filed Oct. 29, 2007 and
U.S. Provisional Patent Application Ser. No. 61/038,525, filed Mar.
21, 2008.
[0003] The present application is a continuation-in-part of U.S.
patent application Ser. No. 16/442,892, filed Jun. 17, 2019, which
is a continuation of U.S. patent application Ser. No. 15/642,846
filed Jul. 6, 2017, now U.S. Pat. No. 10,446,285, which is a
continuation of U.S. patent application Ser. No. 13/731,803 filed
Dec. 31, 2012, now U.S. Pat. No. 9,728,286, which is a continuation
of U.S. patent application Ser. No. 12/024,071, filed Jan. 31,
2008, now U.S. Pat. No. 8,345,813, which in turn claims the benefit
of U.S. Provisional patent Application Ser. No. 60/887,505, filed
Jan. 31, 2007.
[0004] The aforementioned priority applications are incorporated
herein by reference in their entireties.
BACKGROUND OF THE INVENTION
[0005] In the operation of nuclear reactors, hollow zircaloy tubes
filled with enriched uranium, known as fuel assemblies, are burned
up inside the nuclear reactor core. It is necessary to remove these
fuel assemblies from the reactor after their energy has been
depleted to a predetermined level. Upon depletion and subsequent
removal from the reactor, these spent nuclear fuel ("SNF") rods are
still highly radioactive and produce considerable heat, requiring
that great care be taken in their subsequent packaging,
transporting, and storing. Specifically, the SNF emits extremely
dangerous neutrons and gamma photons. It is imperative that these
neutrons and gamma photons be contained at all times subsequent to
removal from the reactor core.
[0006] It is necessary that the neutron and gamma radiation emitted
from the spent fuel assemblies be adequately contained at all times
upon being removed from the reactor. It is also necessary that the
spent fuel assemblies be cooled. Because water is an excellent
radiation absorber, spent fuel assemblies are typically submerged
under water in a pool promptly after being removed from the
reactor. The pool water also serves to cool the spent fuel
assemblies by drawing the heat load away from the fuel assemblies.
The water may also contain a dissolved neutron shielding
substance.
[0007] The submerged fuel assemblies are typically supported in the
fuel pools in a generally upright orientation in rack structures,
commonly referred to as fuel racks. It is well known that neutronic
interaction between fuel assemblies increases when the distance
between the fuel assemblies is reduced. Thus, in order to avoid
criticality (or the danger thereof) that can result from the mutual
inter-reaction of adjacent fuel assemblies in the racks, it is
necessary that the fuel racks support the fuel assemblies in a
spaced manner that allows sufficient neutron absorbing material to
exist between adjacent fuel assemblies. The neutron absorbing
material can be the pool water, a structure containing a neutron
absorbing material, or combinations thereof.
[0008] Fuel racks for high density storage of fuel assemblies are
commonly of cellular construction with neutron absorbing plate
structures (i.e., shields) placed between the cells in the form of
solid sheets. The cells are usually long vertical square tubes
which are open at the top through which the fuel elements are
inserted. The cells are sometimes with double walls that
encapsulate the neutron shield sheets to protect the neutron shield
from corrosion or other deterioration resulting from contact with
water.
[0009] Each fuel assembly is placed in a separate cell so that the
fuel assemblies are shielded from one another. An example of a
typical existing fuel rack is described in U.S. Pat. No. 4,382,060,
to Maurice Holtz et al., issued May 3, 1983, the entirety of which
is hereby incorporated by reference. The Holtz rack is comprised of
structural elements including elements which are hollow and
cruciform in section. Each leg of the cruciform structural element
includes a neutron shield therein. The free end of the legs of the
cruciform structural element converge so as to have an included
angle of approximately 90 degrees. The rack is comprised of such
cruciform elements as well as cooperating elements which are
generally T and L shaped in section.
[0010] In certain regions of the world, the fuel assemblies used in
the nuclear reactors do not have a rectangular horizontal
cross-section. Instead, the fuel assemblies have a horizontal
cross-section that is generally hexagonal. In such instances,
existing racks having cells with rectangular horizontal
cross-sections are less than optimal.
[0011] Even after removal from the pool, the fuel assemblies still
emit extremely dangerous neutrons (i.e., neutron radiation) and
gamma photons (i.e., gamma radiation) and it is thus still
imperative that these neutrons and gamma photons be contained at
all times during transfer and storage. It also imperative that the
residual heat emanating from the fuel assemblies be lead away and
escape from the fuel assemblies. Thus, containers used to transfer
and/or store fuel assemblies must not only safely enclose and
absorb the radioactivity of the fuel assemblies, they must also
allow for adequate cooling. In the art, there are two type of
container systems used to transport and/or store fuel assemblies,
canister-based systems and cask-based systems.
[0012] Generally speaking, there are two types of casks used for
the transportation and/or storage of SNF, ventilated vertical
overpacks ("VVOs") and thermally conductive casks. VVOs typically
utilized in conjunction with a sealable canister that is loaded
with the fuel assemblies and positioned within a cavity of the VVO.
Such canisters, which are often multi-purpose canisters, often
contain a fuel basket for receiving the fuel assemblies. An example
of a canister and basket assembly designed for use with a VVO is
disclosed in U.S. Pat. No. 5,898,747 (Singh), issued Apr. 27, 1999,
the entirety of which is hereby incorporated by reference. The
second type of casks are thermally conductive casks. In a typical
thermally conductive cask, the fuel assemblies are loaded directly
into a cavity formed by the cask body. A basket assembly is
typically provided within the cavity itself to provide support for
the fuel assemblies.
[0013] The fuel basket generally acts in conjunction with the cask
to support the fuel in a particular pattern, minimize load transfer
to the fuel, transfer heat to the cask and control criticality.
[0014] In defueling a nuclear reactor, the SNF is removed from the
reactor and placed under water, in what is generally known as a
spent fuel pool or pond storage. The pool water facilitates cooling
of the SNF and provides adequate radiation shielding. The SNF is
stored in the pool for a period of time that allows the heat and
radiation to decay to a sufficiently low level so that the SNF can
be transported with safety. However, because of safety, space, and
economic concerns, use of the pool alone is not satisfactory where
the SNF needs to be stored for any considerable length of time.
Thus, when long-term storage of SNF is required, it is standard
practice in the nuclear industry to store the SNF in a dry state
subsequent to a brief storage period in the spent fuel pool. Dry
storage of SNF typically comprises storing the SNF in a dry inert
gas atmosphere encased within a structure that provides adequate
radiation shielding.
[0015] Systems that are used to store SNF for long periods of time
in the dry state typically utilize a hermetically sealable and
transportable canister or similar structure that serves as a vessel
for the transfer and storage of the SNF. One such canister, known
as a multi-purpose canister ("MPC"), is described in U.S. Pat. No.
5,898,747, to Krishna P. Singh, issued Apr. 27, 1999, the entirety
of which is hereby incorporated by reference. Typically, the SNF is
loaded into an open canister that is submerged under water in a
fuel pool. Once loaded with SNF, the canister is removed from the
pool, placed in a staging area, dewatered, dried, hermetically
sealed and transported to a storage facility. An example of a
canister drying method can be found in U.S. Pat. No. 7,096,600, to
Krishna P. Singh, issued Aug. 29, 2006, the entirety of which is
hereby incorporated by reference. Because a typical canister does
not by itself provide the necessary radiation shielding properties,
canisters are often positioned within large storage containers
known as casks/overpacks during all stages of transportation and/or
storage. An example of a canister transfer and storage operation
can be found in U.S. Pat. No. 6,625,246, to Krishna P. Singh,
issued Sep. 23, 2003, the entirety of which is hereby incorporated
by reference.
[0016] A dry storage canister ("DSC") provides the confinement
boundary for the stored SNF. Thus, the structural and hermetic
integrity of the DSC is extremely important. An existing DSC is
sold in the United States by Transnuclear, Inc. of Columbia, Md.
under the tradename NUHOMS. The NUHOMS DSC is a single-walled
vessel with two top closure lids, including an inner top lid and an
outer top lid. The closure lids are welded to a canister body after
the SNF has been loaded into it. In the United States, the practice
of using two closure lids to create a double confinement barrier
only at the field welded closure location is motivated by the fact
that field welds are generally less sound than those made in the
factory.
[0017] However, in other countries, the creation of a double
confinement barrier only at the field welded closure does not meet
nuclear regulatory mandates. For example, Ukrainian regulatory
practice calls for a double confinement boundary all around the
SNF. To meet this dual-confinement requirement, the NUHOMS DSC
comprises a hermetically-sealed fuel tube in which SNF rods in the
form of a fuel bundle (half of a fuel assembly) is placed. These
fuel tubes are positioned within the main cavity of the NUHOMS DSC.
However, the body of the NUHOMS DSC remains a single-walled
cylindrical vessel. The fuel tube concept of the NUHOMS DSC meets
the basic Ukrainian regulation that a double confinement boundary
exist all around the SNF. However, as will be discussed in greater
detail below, it has been discovered that this design suffers from
a number of significant drawbacks and engineering design flaws.
[0018] To protect the environment from radiation exposure, spent
nuclear fuel is both transported and stored in large cylindrical
containers called casks. A transfer cask is used to transport spent
nuclear fuel between locations while a storage cask is used to
store spent nuclear fuel for a determined period of time. Casks are
typically designed to shield the environment from the dangerous
radiation in two ways. First, shielding of gamma radiation requires
large amounts of mass. Gamma rays are best absorbed by materials
with a high atomic number and a high density, such as concrete,
lead, and steel. The greater the density and thickness of the
blocking material, the better the absorption/shielding of the gamma
radiation. Second, shielding of neutron radiation requires a large
mass of hydrogen-rich material. One such material is water, which
can be further combined with boron for a more efficient absorption
of neutron radiation.
[0019] The transfer cask must perform the vital function of
providing adequate radiation shielding for both neutron and gamma
radiation emitted by the enclosed spent nuclear fuel. The transfer
cask must also be designed to provide adequate heat transfer.
Guided by the shielding principles discussed above, transfer casks
are made of lead or a gamma absorbing material and contain a
neutron absorbing material as well. As stated previously, greater
radiation shielding is provided by increased thickness and density
of the gamma and neutron absorbing materials. The weight of a fully
loaded transfer cask is typically in the range of 100-125 tons.
[0020] Similarly, storage casks are designed to be large, heavy
structures made of steel, lead, concrete and an environmentally
suitable hydrogenous material. However, because storage casks are
not handled as much as transfer casks, the primary focus in
designing a storage cask is to provide adequate radiation shielding
for the long-term storage of spent nuclear fuel. Size and weight
are at best secondary considerations. As a result of maximizing the
thickness of radiation absorbing materials, the weight and size of
storage casks often cause problems associated with lifting and
handling. Typically, storage casks weigh approximately 150 tons and
have a height greater than 15 ft. A common problem is that storage
casks cannot be lifted by nuclear power plant cranes because their
weight exceed the rated capacity of the crane.
[0021] A common problem arises when the fully loaded transfer cask
must be transported to the storage cask for the canister transfer
procedure. Generally, the storage cask is located in a truck bay,
or other location outside of the staging area. To get to the
transfer cask, the storage cask may have to pass through a door of
a nuclear plant's truck bay. The doors are typically 17-24 feet
tall. The transfer casks are typically about 16 feet and 3 inches
tall. The need to move casks into and out of enclosed facilities
limits the size and shape of machines that can be used to move the
casks. For example, a low ceiling in such a facility makes it
impractical to use a boom or overhead crane to lift and transport
casks. Similarly, a doorway not much larger than the cask itself
limits the extent to which a lifting device can extend beyond the
sides, top or bottom of the cask. Thus, a need exists for a low
profile transporter that can withstand the weight of the storage
cask.
SUMMARY OF THE INVENTION
[0022] In one aspect, the invention can be a fuel rack having an
array of cells for holding fuel assemblies comprising: a base plate
having a top surface; a plurality of tubes, each tube having an
inner surface that forms one of the cells; and the tubes connected
to the top surface of the base plate in a substantially vertical
orientation and in a pattern so that one or more of the cells are
formed by outside surfaces of the adjacent tubes.
[0023] In another aspect, the invention can be a fuel rack for
supporting fuel assemblies comprising: a plurality of hexagonal
tubes having an internal cavity; a base plate having a top surface;
the hexagonal tubes connected to the top surface of the base plate
in a substantially vertical orientation and spaced from one another
so that a flux trap space exists between all adjacent hexagonal
tubes; and a plurality of spacers positioned in the flux trap
spaces for maintaining the existence of the flux trap spaces, the
spacers connected to the hexagonal tubes.
[0024] In yet another aspect, the invention can be a fuel rack
having an array of cells for holding fuel assemblies comprising a
plurality of slotted plates that are slidably interlocked with one
another to form the array of cells.
[0025] In another aspect, the invention can be a fuel basket having
a honeycomb-like grid that forms a plurality of substantially
vertically oriented elongated cells. Most preferably, the basket
assembly comprises one or more flux traps and is positioned within
the cavity. The basket assembly can be constructed of a metal
matrix composite material. In one embodiment, the basket assembly
may utilize variable flux traps to maximize packing density. In
such an embodiment, as the periphery of the basket assembly is
approached, the width of the flux traps may decrease. In another
embodiment, the basket assembly may utilize tubular elements of
varying heights in a vertically staggered formation so that no two
adjacent cells have interfaces which are vertically aligned.
[0026] In a further aspect, the invention can be an apparatus for
supporting radioactive fuel assemblies comprising: a grid of cells
for housing radioactive fuel assemblies, the grid formed by a
plurality of hexagonal tubes having an outer surface and an inner
surface that forms one of the cells, the plurality of hexagonal
tubes arranged in an adjacent manner and in a pattern so that one
or more of the cells is a resultant cell formed by the outside
surfaces of surrounding hexagonal tubes.
[0027] In a yet further aspect, the invention can be an apparatus
for supporting radioactive fuel assemblies comprising: a grid of
cells for housing radioactive fuel assemblies, the grid formed by a
plurality of tubes having inner surfaces that form the cells, the
tubes arranged in an axially aligned and adjacent manner; each of
the tubes formed by a plurality of tubular segments stacked in
axial alignment, an interface formed between the adjacent tubular
segments of each tube; and wherein the lengths of the tubular
segments and the pattern in which the tubes are arranged to form
the grid is such that none of the interfaces of adjacent tubes are
aligned with one another.
[0028] In a still further aspect, the invention can be an apparatus
for supporting radioactive fuel assemblies comprising: a bottom
section comprising a plurality of bottom tubular segments of
varying length, the bottom tubular segments arranged in an axially
adjacent manner and in a pattern so that no two adjacent bottom
tubular segments are the same length, the bottom edges of the
bottom tubular segments being aligned; at least one middle section
comprising a plurality of middle tubular segments of equal length,
the middle section stacked atop the bottom section so that the
middle tubular segments are axially aligned with the bottom tubular
segments and the bottom edges of the middle tubular segments abut
the top edges of the bottom tubular segments; and a top section
comprising a plurality of top tubular segments of varying length,
the top section stacked atop the middle section so that the top
tubular segments are axially aligned with the middle tubular
segments, the bottom edges of the top tubular segments abut the top
edges of the bottom tubular segments, and the top edges of the top
tubular segments are aligned.
[0029] In even another aspect, the invention can be a fuel rack
having a grid of cells for holding fuel assemblies comprising: a
base plate having a top surface; a plurality of hexagonal tubes,
each hexagonal tube having inner surfaces that forms one of the
cells; and the hexagonal tubes connected to the top surface of the
base plate in a substantially vertical orientation and in a pattern
so that one or more of the cells are formed by outside surfaces of
the adjacent hexagonal tubes.
[0030] In yet another aspect, the invention can be a fuel rack
having a grid of cells for holding fuel assemblies comprising: a
base plate having a top surface; a plurality of tubes, each tube
having an inner surface that forms one of the cells; and the tubes
connected to the top surface of the base plate in a substantially
vertical orientation and in a pattern so that one or more of the
cells are formed by outside surfaces of the adjacent tubes.
[0031] In still another aspect, the invention can be a fuel rack
for supporting fuel assemblies comprising: a plurality of hexagonal
tubes having an internal cavity; a base plate having a top surface;
the hexagonal tubes connected to the top surface of the base plate
in a substantially vertical orientation and spaced from one another
so that a flux trap space exists between all adjacent hexagonal
tubes; and a plurality of spacers positioned in the flux trap
spaces for maintaining the existence of the flux trap spaces, the
spacers connected to the hexagonal tubes.
[0032] In another aspect, the invention can be a fuel rack for
supporting fuel assemblies comprising: a plurality of tubes having
an internal cavity; a base plate having a top surface; the tubes
connected to the top surface of the base plate in a substantially
vertical orientation and spaced from one another so that a flux
trap space exists between all adjacent tubes; and a plurality of
spacers positioned in the flux trap spaces for maintaining the
existence of the flux trap spaces, the spacers connected to the
tubes.
[0033] In a still further aspect, the invention can be a fuel rack
having perimeter cells and non-perimeter cells for supporting fuel
assemblies comprising: a base plate having a top surface; a
plurality of hexagonal tubes, each hexagonal tube having inner
surfaces that form one of the perimeter cells or the non-perimeter
cells; and the hexagonal tubes connected to the top surface of the
base plate in a substantially vertical orientation and in a pattern
so that every third non-perimeter cell is formed by outside
surfaces of six surrounding hexagonal tubes.
[0034] In yet another aspect, the invention can be a fuel basket
for supporting radioactive fuel assemblies comprising: a plurality
of tubes having an internal cavity for receiving a radioactive fuel
assembly; the tubes arranged in a substantially vertical
orientation and spaced from one another so that a flux trap space
exists between all adjacent tubes, the tubes forming a storage grid
having a central axis and a perimeter; a plurality of spacers
positioned in the flux trap spaces for maintaining the existence of
the flux trap spaces; and wherein the width of the flux trap space
between adjacent tubes decreases with distance from the central
axis of the storage grid.
[0035] In an even further aspect, the invention can be a fuel rack
for supporting spent nuclear fuel assemblies comprising: a base
plate having a top surface; a fuel rack body extending upward from
the base plate and comprising a plurality of cells, each of the
cells having an open top end and being configured to receive a
spent nuclear fuel assembly, and wherein for each of the cells, a
portion of an upper surface of the base plate forms a floor of the
cell; a plurality of adjustable height pedestals connected to a
bottom surface of the base plate, each of the adjustable height
pedestals comprising: a block having a hole defined by a threaded
inner surface, the block fixedly coupled to the base plate; a peg
having a threaded outer surface, the threaded outer surface of the
peg threadily engaged to the threaded inner surface of the block;
an engagement element in a top surface of the peg; and wherein upon
a tool engaging the engagement element and rotating the peg, the
extent the peg protrudes from a bottom surface of the block is
adjusted; and wherein for each of the adjustable height pedestals,
the adjustable height pedestal is coupled to the base plate so that
the engagement element is aligned with and is accessible via a hole
in the floor of one of the cells.
[0036] In one aspect, the invention can be a canister for storing
and/or transporting spent nuclear fuel rods comprising: a first
shell forming a cavity for receiving spent nuclear fuel rods; a
first plate connected to the first shell so as to form a floor of
the cavity; a first lid enclosing the cavity; the first shell, the
first plate and the first lid forming a first hermetic containment
boundary about the cavity; a basket for supporting a plurality of
spent nuclear fuel rods positioned within the cavity; a second
shell surrounding the first shell so that an inner surface of the
second shell is in substantially continuous surface contact with an
outer surface of the first shell; a second plate connected to the
second shell; a second lid; and the second shell, the second plate
and the second lid forming a second hermetic containment boundary
that surrounds the first radiation containment boundary.
[0037] In another aspect, the invention can be a canister apparatus
for storing and/or transporting spent nuclear fuel rods comprising:
a first pressure vessel comprising a first shell forming a first
cavity for receiving spent nuclear fuel rods, a first plate
connected to the first shell so as to enclose a first end of the
first cavity, and a first lid connected to the first shell so as to
enclose a second end of the first cavity; a second pressure vessel
comprising a second shell forming a second cavity, a second plate
connected to the second shell so as to enclose a first end of the
second cavity, and a second lid connected to the second shell so as
to enclose a second end of the second cavity; and the first
pressure vessel located within the second cavity so that an inner
surface of the second shell is in substantially continuous surface
contact with an outer surface of the first shell.
[0038] In yet another aspect, the invention can be a canister
apparatus for storing and/or transporting spent nuclear fuel rods
comprising: a first metal pressure vessel having an outer surface
and forming a cavity for receiving spent nuclear fuel rods; a
second metal pressure vessel having an inner surface; and the first
pressure vessel located within the second pressure vessel so that a
substantial entirety of the outer surface of the first metal
pressure vessel is in substantially continuous surface contact with
the inner surface of the second metal pressure vessel.
[0039] In still another aspect, the invention can be a canister
apparatus for storing and/or transporting spent nuclear fuel rods
comprising: a first structural assembly forming a cavity for
receiving spent nuclear fuel rods, the first structural assembly
forming a first gas-tight containment boundary surrounding the
cavity; a second structural assembly surrounding the first
structural assembly, the second structural assembly forming a
second gas-tight containment boundary surrounding the cavity; and
wherein the first structural assembly and second structural
assembly are in substantially continuous surface contact with one
another.
[0040] In yet another aspect, the invention can be a basket
apparatus for supporting a plurality of spent nuclear fuel rods
within a containment structure comprising: a plurality of disk-like
grates, each disk-like grate having a plurality of cells formed by
a gridwork of beams; and means for supporting the disk-like grates
in a spaced arrangement with respect to one another and so that the
cells of the disk-like grates are aligned.
[0041] In a further aspect, the invention can be a basket apparatus
for supporting a plurality of spent nuclear fuel rods within a
containment structure comprising: a disk-like grate having a
ring-like structure encompassing a gridwork of beams; the gridwork
of beams comprising a first series of parallel beams, a second
series of parallel beams and a third series of parallel beams; and
wherein the first, second and third series of parallel beams are
arranged in the ring-like structures so as to intersect and form a
plurality of cells.
[0042] In another aspect, the invention can be a basket apparatus
for supporting a plurality of spent nuclear fuel rods within a
containment structure comprising: a disk-like grate having a
ring-like structure encompassing a gridwork of beams; and the
gridwork of beams forming a first set of cells having a first shape
and a second set of cells having a second shape.
[0043] In one aspect, the invention can be an apparatus for
translating a nuclear waste storage cask comprising: a body for
supporting a cask; and at least two rollers adapted to move between
a retracted position and an extended position, wherein when the
rollers are in the retracted position, the rollers do not contact a
ground surface.
[0044] In another aspect the invention can be an apparatus for
translating a cask comprising: a body comprising a top surface, an
open top end and a cavity for receiving a cask, at least one
support member for supporting a cask close to a ground surface; and
rollers for translating the apparatus.
[0045] In a yet further aspect the invention can be A system for
translating spent nuclear fuel comprising: an apparatus for
supporting and translating a cask comprising: a body having an open
top end and a cavity for receiving a cask; and at least two rollers
adapted to move between a retracted position and an extended
position; a cask positioned in the cavity, wherein the cask is
supported close to a ground surface.
[0046] In another aspect the invention can be a method of
supporting and translating a storage cask comprising the steps of:
(a) providing an apparatus comprising: a body for supporting a
cask; and at least two rollers adapted to move between a retracted
position and an extended position. (b) placing a cask onto the body
of the apparatus; (c) loading spent nuclear fuel into the cask; (c)
moving the rollers of the apparatus into the extended position; and
(d) translating the apparatus.
[0047] In yet another aspect, the invention can be a system for
translating high level radioactive waste across a ground surface,
the system comprising: a cask loaded with high level radioactive
waste; an apparatus comprising: a body having a cavity having an
open top end; and a plurality of rollers coupled to the body to be
adjustable between: (1) an extended position in which the plurality
of rollers contact the ground surface and support the body above
the ground surface; and (2) a retracted position in which the
plurality of rollers do not contact the ground surface and the body
contacts the ground surface; and the cask positioned in the cavity,
the cask supported above the ground surface by the apparatus when
the plurality of rollers are in the extended position.
[0048] In still another embodiment, the invention can be a system
for translating high level radioactive waste across a ground
surface, the system comprising: a cask loaded with high level
radioactive waste; an apparatus comprising: a body having a cavity
having an open top end; a plurality of rollers coupled to the body;
and at least one contact member coupled to the body and extending
into the cavity; a lower portion of the cask positioned in the
cavity so that the cask rests atop the at least one contact member
and is above the ground surface, an upper portion of the cask
protruding from the open top end of the cavity.
[0049] In a further embodiment, the invention can be a system for
translating high level radioactive waste across a ground surface,
the system comprising: a cask loaded with high level radioactive
waste; an apparatus comprising: a body having a cavity having an
open top end; and a plurality of rollers coupled to the body; the
cask supported by the apparatus above the ground surface so that a
lower portion of the cask is positioned within the cavity and an
upper portion of the cask protrudes from the open top end of the
cavity
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The present invention will become more fully understood from
the detailed description and the accompanying drawings, wherein
like elements are labeled similarly and in which:
[0051] FIG. 1 is a top perspective view of a fuel rack according to
one embodiment of the invention.
[0052] FIG. 2 is a close up view of a top portion of the fuel rack
of FIG. 1.
[0053] FIG. 3 is a top view of the fuel rack of FIG. 1.
[0054] FIG. 4 is a bottom perspective view of the fuel rack of FIG.
1.
[0055] FIG. 5 is a close-up view of a bottom corner of the fuel
rack of FIG. 1.
[0056] FIG. 6A is a top perspective view of an adjustable height
pedestal removed from the fuel rack of FIG. 1.
[0057] FIG. 6B is a bottom perspective view of the adjustable
height pedestal of FIG. 6A.
[0058] FIG. 7 is a top perspective view of a fuel rack according to
a second embodiment of the invention that includes flux traps.
[0059] FIG. 8 is a close up view of a top portion of the fuel rack
of FIG. 7.
[0060] FIG. 9 is a top view of the fuel rack of FIG. 7.
[0061] FIG. 10 is a top perspective view of a fuel rack according
to one embodiment of the invention that is constructed of a slotted
plates.
[0062] FIG. 11A is a perspective view of first slotted plate used
in the construction of the fuel rack of FIG. 10.
[0063] FIG. 11B is a perspective view of a second slotted plate
used in the construction of the fuel rack of FIG. 10.
[0064] FIG. 11C is a perspective view of a third slotted plate used
in the construction of the fuel rack of FIG. 10.
[0065] FIG. 12 is a perspective view of a vertical section of
slotted plates of the fuel rack of FIG. 10.
[0066] FIG. 13 is a top perspective view of a storage grid portion
of a fuel basket according to an embodiment of the present
invention.
[0067] FIG. 14 is a top view of the area II-II of FIG. 13
illustrating a resultant cell according to one embodiment of the
present invention.
[0068] FIG. 15 is a perspective view of the bottom vertical
segments of the storage tubes of the fuel basket of FIG. 13
arranged in the desired pattern so that interfaces between segments
of adjacent storage tubes are not vertically aligned.
[0069] FIG. 16 is a top view of a fuel basket according to one
embodiment of the present invention, comprising the storage grid
portion of FIG. 13 and perimeter support tubes.
[0070] FIG. 17 is a perspective view of the supports tubes
according to one embodiment of the present invention.
[0071] FIG. 18 is a perspective view of the fuel basket of FIG.
16.
[0072] FIG. 19 is a perspective view of a fuel basket assembly
according to a second embodiment of the present invention.
[0073] FIG. 20 is a perspective view of a storage tube of the fuel
basket of FIG. 19.
[0074] FIG. 21 is a perspective view of the bottom vertical segment
of the storage grid portion of the fuel basket of FIG. 19.
[0075] FIG. 22 is a bottom perspective view of the storage grid
portion of the fuel basket of FIG. 19.
[0076] FIG. 23 is a top perspective view of the storage grid
portion of the fuel basket of FIG. 19.
[0077] FIG. 24 is a top view of the fuel basket of FIG. 19.
[0078] FIG. 25 is a top perspective view of a dual-walled DSC
according to one embodiment of the present invention having a
section cut-away.
[0079] FIG. 26 is an exploded view of the dual-walled DSC of FIG. 1
showing the inner and outer top lids removed from the inner and
outer shells.
[0080] FIG. 27 is a close-up view of the area XXVII of FIG. 25
[0081] FIG. 28 is a close-up view of the area XXVIII of FIG.
26.
[0082] FIG. 29 is a perspective view of the dual-walled DSC of FIG.
25 having a section cut-away and having a fuel basket according to
one embodiment of the present invention positioned within the
storage cavity.
[0083] FIG. 30 is a close-up view of area XXX of FIG. 29.
[0084] FIG. 31 is a top view of a portion of the dual-walled DSC of
FIG. 29 with the lid assembly removed and fuel basket positioned
therein.
[0085] FIG. 32 is a top perspective view of the disk-like grate
components of the fuel basket of FIG. 31 according to one
embodiment of the present invention.
[0086] FIG. 33 is a perspective view of the ventilated fuel tube
and the poison rod of the fuel basket assembly of FIG. 31 removed
therefrom according to one embodiment the present invention.
[0087] FIG. 34 is a top perspective view of a low profile
transporter according to one embodiment of the present
invention.
[0088] FIG. 35 is a bottom perspective view of the transporter of
FIG. 34 according to one embodiment of the present invention.
[0089] FIG. 36 is a top perspective view of the transporter of FIG.
4 with a cover plate removed on one side of the transporter
according to one embodiment of the present invention.
[0090] FIG. 37 is a close-up perspective view of section XXXVII of
FIG. 36 according to one embodiment of the present invention.
[0091] FIG. 38 is a perspective view of a roller assembly of the
low profile transporter according to one embodiment of the present
invention.
[0092] FIG. 39 is a bottom perspective view of the low profile
transporter of FIG. 34 and a cask positioned above the low profile
transporter according to one embodiment of the present
invention.
[0093] FIG. 40 is a bottom perspective view of the low profile
transporter and cask of FIG. 39 with the cask positioned in the low
profile transporter according to one embodiment of the present
invention.
[0094] FIG. 41 is a perspective view of the low profile transporter
and cask of FIG. 40 positioned on tracks of a ground surface
according to one embodiment of the present invention.
[0095] FIG. 42 is a perspective view of the low profile transporter
and cask of FIG. 40 translating under an over head door according
to one embodiment of the present invention.
[0096] All drawings are schematic and not necessarily to scale.
Parts shown and/or given a reference numerical designation in one
figure may be considered to be the same parts where they appear in
other figures without a numerical designation for brevity unless
specifically labeled with a different part number and described
herein. References herein to a whole figure number (e.g. FIG. 1)
shall be construed to be a reference to all subpart figures in the
group (e.g. FIGS. 1A, 1B, etc.) unless otherwise indicated.
DETAILED DESCRIPTION OF THE DRAWINGS
[0097] The features and benefits of the invention are illustrated
and described herein by reference to exemplary embodiments. This
description of exemplary embodiments is intended to be read in
connection with the accompanying drawings, which are to be
considered part of the entire written description. Accordingly, the
disclosure expressly should not be limited to such exemplary
embodiments illustrating some possible non-limiting combination of
features that may exist alone or in other combinations of
features.
[0098] In the description of embodiments disclosed herein, any
reference to direction or orientation is merely intended for
convenience of description and is not intended in any way to limit
the scope of the present invention. Relative terms such as "lower,"
"upper," "horizontal," "vertical,", "above," "below," "up," "down,"
"top" and "bottom" as well as derivatives thereof (e.g.,
"horizontally," "downwardly," "upwardly," etc.) should be construed
to refer to the orientation as then described or as shown in the
drawing under discussion. These relative terms are for convenience
of description only and do not require that the apparatus be
constructed or operated in a particular orientation. Terms such as
"attached," "affixed," "connected," "coupled," "interconnected,"
and similar refer to a relationship wherein structures are secured
or attached to one another either directly or indirectly through
intervening structures, as well as both movable or rigid
attachments or relationships, unless expressly described
otherwise.
[0099] As used throughout, any ranges disclosed herein are used as
shorthand for describing each and every value that is within the
range. Any value within the range can be selected as the terminus
of the range. In addition, all references cited herein are hereby
incorporated by reference in their entireties. In the event of a
conflict in a definition in the present disclosure and that of a
cited reference, the present disclosure controls.
[0100] Multiple inventive concepts are described herein and are
distinguished from one another using headers in the description
that follows. Specifically, FIGS. 1-24 are relevant to a first
inventive concept, FIGS. 25-33 are relevant to a second inventive
concept, and FIGS. 34-42 are relevant to a third inventive concept.
The first through third inventive concepts should be considered in
isolation from one another. It is possible that there may be
conflicting language or terms used in the description of the first
through third inventive concepts. For example, it is possible that
in the description of the first inventive concept a particular term
may be used to have one meaning or definition and that in the
description of the second inventive concept the same term may be
used to have a different meaning or definition. In the event of
such conflicting language, reference should be made to the
disclosure of the relevant inventive concept being discussed.
Similarly, the section of the description describing a particular
inventive concept being claimed should be used to interpret claim
language when necessary.
I. Inventive Concept 1
[0101] With reference to FIGS. 1-25, a first inventive concept will
be described.
I. Flux Trap Fuel Rack Embodiment
[0102] Referring to FIG. 1, a perspective view of a fuel rack 100
according to one embodiment of the present invention is disclosed.
The fuel rack 100 is a cellular, upright, prismatic module. The
illustrated embodiment of the fuel rack 100 is specifically
designed to accommodate hexagonal fuel assemblies, such as VVER
1000 fuel assemblies. To this extent, each cell 101 of the fuel
rack 100 is also generally hexagonal in shape (i.e., have a
hexagonal horizontal cross-section) so as to geometrically
accommodate a single hexagonal fuel assembly. However, it is to be
understood that the concepts of the present invention can be
modified to accommodate any shaped fuel assembly, including
rectangular, octagonal, round, etc.
[0103] In describing the fuel rack 100 and its component parts
below, relative terms such as top, bottom, above, below,
horizontal, vertical upper and lower will be used in relation to
the fuel rack 100 being in the illustrated substantially vertical
orientation of FIG. 1. Additionally, in order to avoid clutter in
the drawings, only a few of each component are numbered with the
understanding that the reader will be able to identify duplicate
elements.
[0104] The fuel rack 100 generally comprises a base plate 110, a
plurality of hexagonal tubes 120, and a plurality of spacing rods
130 (best visible in FIG. 2). The hexagonal tubes 120 are connected
to the top surface 111 of the base plate 110 in a substantially
vertical orientation. In this embodiment, the axis of each
hexagonal tube 120 is not only substantially vertical but also
substantially perpendicular to the top surface 111 of the base
plate 110. The connection between the hexagonal tubes 120 and the
base plate 110 is achieved by welding the bottom edge of the
hexagonal tubes 120 to the top surface of the base plate 110. Of
course, other connection techniques can be utilized with minor
modification, including mechanical connections such as bolting,
clamping, threading, etc.
[0105] The top ends of the hexagonal tubes 120 remain open so that
a fuel assembly can be slid into the internal cavity 101 (also
referred to as a cell) formed by the inner surfaces of the
hexagonal tubes 120. Each hexagonal tube 120 can be a single-part
tube that extends the entire desired height H.sub.1 or can be
constructed of multiple partial height tubes that together add up
to the desired height H.sub.1. It is preferred that the height
H.sub.1 be sufficient so that the entire height of the fuel
assembly is within the hexagonal tube 120
[0106] The hexagonal tubes 120 are connected to the rectangular
base plate 110 in an adjacent and spaced pattern to form a
honeycomb-like grid of the cells 101. The cells 101 are
substantially vertical elongated cavities for receiving the
radioactive fuel assemblies via their open top ends. While a
generally rectangular gridwork of cells 101 is illustrated, the
fuel rack 100 can be designed to take on any desired shape. The
geometric arrangement of the hexagonal tubes 120 will be discussed
in greater detail below with respect to FIGS. 2-3.
[0107] The hexagonal tubes 120 preferably constructed of a
metal-matrix composite material, and more preferably a
discontinuously reinforced aluminum/boron carbide metal matrix
composite material, and most preferably a boron impregnated
aluminum. One such suitable material is sold under the tradename
Metamic.TM.. The hexagonal tubes 120 perform the dual function of
reactivity control as well as structural support. The base plate
110 is preferably constructed of a metal that is metallurgically
compatible with the material of which the hexagonal tubes 120 are
constructed for welding.
[0108] Referring now to FIGS. 2-3 concurrently, each hexagonal tube
120 is arranged so as to be spaced from all adjacent hexagonal
tubes 120 so that a gap 140 exists between each hexagonal tube 120
and its immediately adjacent hexagonal tubes 120. The gap 140 acts
a neutron flux trap that decreases and/or eliminates the danger of
criticality. The flux trap space 140 can be designed to be any
desired width and the exact width will depend on the radiation
levels of the fuel assemblies to be stored, the material of
construction of the tubes 120, and properties of the pool water in
which the fuel rack 100 will be submerged. In one embodiment, the
flux trap spaces 140 will have a width between 30 and 50
millimeters and more preferably between 25 to 35 millimeters and
most preferably about 38 millimeters.
[0109] Spacers, which are in the form of spacing rods 130 in the
illustrated embodiment, are inserted into the flux trap spaces 140
so as to maintain the existence of the flux trap spaces 140 at the
desired width and to provide added structural stability. While the
spacers are illustrated as elongated rods 130 that extend the
entire height H.sub.1 of the hexagonal tubes 120, the spacers are
not so limited and can take on a wide variety of shapes and sizes.
For example, the spacers could be merely blocks or pins if desired
in some embodiments.
[0110] A spacing rod 130 is positioned at the juncture between the
edges of three adjacent hexagonal tubes 120. Thus, each spacing rod
130 (with the exception of those spacing rods 130 along the
perimeter) contacts three hexagonal tubes 120. For added integrity
and ease of construction, the spacing rods 130 have three axial
grooves along their length that act as nesting volumes for
receiving the edge of the hexagonal tubes 120. In the illustrated
embodiment, the spacing rods 130 have a horizontal cross-section
that is generally in the shape of a truncated triangle, wherein a
nesting groove is formed into each truncated apex. Of course, the
spacing rods 130 can take on other shapes with or without the
grooves.
[0111] The spacing rods 130 are preferably made of aluminum or a
metal matrix material, such as boron impregnated aluminum. The
spacing rods 130 are plug welded to the hexagonal tubes 120 in
which they are in contact with via elongated holes 121 located at
the edges/corners or the hexagonal tubes 120. The shape, location
and number of plug weld holes 120 will vary depending on design
considerations and is in no way limiting of the present invention.
The plug holes 121 are uniformly on each corner the hexagonal tubes
120 to facilitate uniform manufacture but this is not necessary.
The plug holes 121 can be formed by punching, cutting, or during a
molding process.
[0112] Referring now to FIGS. 3-4 concurrently, the base plate 110
also comprises a plurality of flow holes 115 extending through the
base plate 110 from its bottom surface 112 to its top surface 111.
Similarly, the base plate 110 also comprises four oblong holes 116
(second row in from the corners) for lifting and installing the
fuel rack 100 within the fuel pool. A special lifting beam with
four long reach rods is used to interact with the oblong holes 116
to grapple the fuel rack 100 and place it in the pool.
[0113] The flow holes 115 (and oblong holes 116) create passageways
from below the base plate 100 into the cells 101 formed by the
hexagonal tubes 120. Preferably, a single flow hole 115 is provided
for each cell 101. The flow holes 115 are provided as inlets to
facilitate natural thermosiphon flow of pool water through the
cells 101 when fuel assemblies having a heat load are positioned
therein. More specifically, when heated fuel assemblies are
positioned in the cells 101 in a submerged environment, the water
within the cells 101 surrounding the fuel assemblies becomes
heated, thereby rising due to increased buoyancy. As this heated
water rises and exist the cells 101 via their open top ends, cool
water is drawn into the bottom of the cells 101 via the flow holes
115. This heat induced water flow along the fuel assemblies then
continues naturally.
[0114] As can best be seen in FIG. 5, a plurality of auxiliary
cutouts/holes 121 are provided in the hexagonal tubes 120 at or
near their bottom edge. The auxiliary holes 121 act as additional
inlet openings for incoming pool water to facilitate the
thermosiphon flow during the cooling process. Moreover, as will be
described below, the flow holes 115 of certain cells 101 are
blocked by the attachment of adjustable height pedestals 150. The
auxiliary holes 121 of the hexagonal tubes 120 that form these
cells 101 are thus the sole source of incoming cool water for fuel
assemblies stored therein. While an auxiliary hole 121 is provide
din each face of each and every hexagonal tube 120 in the fuel rack
100, it is to be understood that this may not be necessary in all
instances.
[0115] As a side note, the flow holes 115 (and holes 116) perform
an additional function of providing an access-way into to the cells
101 for a "goose-neck welder" for welding the hexagonal tubes 120
to the top surface of the base plate 110.
[0116] Referring back to FIGS. 3-4, the base plate 110 also
comprises a plurality of adjustable height pedestals 150 connected
to the bottom surface 112 of the base plate 110. The adjustable
height pedestals 150 ensure that a space exists between the floor
of the fuel pool and the bottom surface 112 of the base plate 110,
thereby creating an inlet plenum for water to flow through the flow
holes 115.
[0117] The adjustable height pedestals 150 are spaced to provide
uniform support of the base plate 110 and thus the fuel rack 100.
Each pedestal 150 is individually adjustable to level and support
the rack on a non-uniform spent fuel pool floor. The pedestals 150
are bolted to the base plate 110. Of course, if desired, the
pedestals 150 can be attached top the base plate 110 by other
means, including welding or threading. In the event of welded
pedestal 15, an explosion-bonded stainless-Aluminum plate may be
used to make the transition. For a welded pedestal, the bolts and
bolt holes are eliminated.
[0118] Referring now to FIGS. 6A-6B, the construction details of
the adjustable height pedestals 150 will be described. Each of the
adjustable height pedestals 150 comprises a block 151 and a
cylindrical peg 152 that acts as the foot. The block 152 is
connected to the base plate 110 via bolts 155.
[0119] The block 151 comprises a central hole 153 which has a
threaded inner surface (not visible). Similarly, the outer surface
of a portion of the peg 151 is also threaded with corresponding
threads. The peg 152 is inserted into the hole 153 and threadably
engaged therein to the block 151.
[0120] The peg 152 also comprises a rectangular depression 154 in
its top surface for receiving a tool for turning the peg 152. Of
course, the depression can be any shape that will facilitate
rotational engagement with a tool. Moreover, other means for
engaging and turning the peg 152 can be sued including a tab, a
screw head, a bolt head, etc.
[0121] Because of the threaded connection between the peg 152 and
the block 151, turning the peg 152 via the depression 154 results
in increasing or decreasing the height the peg 152 protrudes from
the bottom surface of the block 151. Adjustment of the peg 152 is
facilitated by a long-handled tool that is inserted into the cell
101. The depression 154 of the peg 152 is accessible through the
flow hole 115 in that cell 101 (see FIG. 3).
[0122] The bottom portion of the peg 152 has a rounded edge to
prevent catching and tearing of the liner in a seismic-induced
slide of the fuel rack 100. A break in the liner means problems for
the site because of leakage. If desired, the bottom surface of the
peg 152 can be formed or covered with a low friction sliding
material.
II. Non-Flux Trap Fuel Rack Embodiment Incorporating Resultant
Cells
[0123] Referring now to FIGS. 7-10 concurrently, a second
embodiment of a fuel rack 200 is illustrated. Similar to the rack
above, the fuel rack 200 is a cellular, upright, prismatic module.
The illustrated embodiment of the fuel rack 200 is specifically
designed to accommodate hexagonal fuel assemblies, such as VVER
1000 fuel assemblies. Each cell 201 of the fuel rack 200 is also
generally hexagonal in shape (i.e., have a hexagonal horizontal
cross-section) so as to geometrically accommodate a single
hexagonal fuel assembly. However, it is to be understood that the
concepts of the present invention can be modified to accommodate
any shaped fuel assembly, including rectangular, octagonal, round,
etc.
[0124] In describing the fuel rack 200 and its component parts
below, relative terms such as top, bottom, above, below,
horizontal, vertical upper and lower will be used in relation to
the fuel rack 200 being in the illustrated substantially vertical
orientation of FIG. 7. Additionally, in order to avoid clutter in
the drawings, only a few of each component are numbered with the
understanding that the reader will be able to identify duplicate
elements.
[0125] The driving factor that leads to the structural differences
between fuel rack 100 (discussed above) and the fuel rack 200 is
that the fuel rack 200 is designed to be used with fuel assemblies
that do not require the presence of a neutron flux trap between
adjacent cells 201. Thus, the inclusion of neutron flux traps in
fuel racks when not needed is undesirable because valuable pool
floor area is unnecessarily wasted. Of course, both fuel rack types
100, 200 may be stored side by side in the same pool.
[0126] Because many of the structural and functional features of
the fuel rack 200 are identical to the fuel rack 100, only those
aspect of the fuel rack 200 that are different will be discussed
below with the understanding that the other concepts discussed
above with respect to fuel rack 100 are applicable.
[0127] The fuel rack 200 comprises a plurality of hexagonal tubes
220. The hexagonal tubes 220 are connected to the top surface 211
of the base plate 210 in a substantially vertical orientation. In
this embodiment, the axis of each hexagonal tube 220 is not only
substantially vertical but also substantially perpendicular to the
top surface 211 of the base plate 210. The connection between the
hexagonal tubes 220 and the base plate 210 is achieved by welding
the bottom edge of the hexagonal tubes 220 to the top surface of
the base plate 110. Of course, other connection techniques can be
utilized with minor modification, including mechanical connections
such as bolting, clamping, threading, etc.
[0128] The top ends of the hexagonal tubes 220 remain open so that
a fuel assembly can be slid into the internal cavity 201A (also
referred to as a cell) formed by the inner surfaces each hexagonal
tube 220. The hexagonal tubes 220 are connected atop the
rectangular base plate 110 in a special geometric arrangement so
that certain non-perimeter cells 201D are formed by the outside
surfaces of the surrounding hexagonal tubes 220. Additionally,
certain perimeter cells 201B-C are formed by the outside surfaces
of the surrounding hexagonal tubes 220 and an added plate, which
depending on the location is either a two-panel plate 225 or a
single panel plate 226.
[0129] In other words, the cells 201B-201D are not the internal
cavities of any tubular structures but are resultant cavities
formed by either (1) the outer surfaces of the surrounding
hexagonal tubes 220; or (2) the outer surfaces of the surrounding
hexagonal tubes 220 and an additional plate structure 225, 226. As
used herein, all three cell types 201B-201D will be referred to as
"resultant cells" or "developed cells."
[0130] Despite their different methods of formation, all of the
cells 201A-201D have a horizontal cross-section that is generally
hexagonal. Of course, the result cell concept can be applied to a
host of other geometries if desired. The special geometric
arrangement of the hexagonal tubes 220 and an additional plate
structure 225-226 atop the base plate 210 will now be
discussed.
[0131] As can best be seen in FIG. 9, the hexagonal tubes 220 are
geometrically arranged atop the base plate 210 in rows 1-11
(indicated numerically in a circle). Of course, any number of rows
or columns may be created for the fuel rack 200. The details of the
formation of three different kinds of resultant cells will be
described in reference to rows 1 through 3 with the understanding
that the certain patterns repeat and thus the entire fuel rack 200
can be constructed.
[0132] A. Formation of Perimeter Resultant Cells X
[0133] The formation of perimeter resultant cells formed by the
combination of outside surfaces of the hexagonal tubes and a
two-panel plate structure (referred to above as type 201C cells)
will now be described. For ease of reference and to avoid clutter,
all perimeter resultant cells formed by the combination of outside
surfaces of the hexagonal tubes and a two-panel plate structure are
marked with an X.
[0134] In row 1, the hexagonal tubes 220(1), 220(2) are arranged
atop the base plate 210 in the top left corner in an adjacent and
abutting manner so that the opposing outside surfaces of the
hexagonal tubes 220(1), 220(2) are in surface contact. The internal
cavities of the hexagonal tubes 220(1), 220(2) act as the first two
cells 201A (not marked). To reduce further clutter, all cells 201A
that are formed by the inner surfaces of a single hexagonal tube
220 are left blank in FIG. 9.
[0135] A second pair hexagonal tubes 220(3), 220(4) are arranged
atop the base plate 210 within row 1 and spaced from the first pair
of hexagonal tubes 220(1), 220(2). Similar to the first pair of
hexagonal tubes 220(1), 220(2), the second pair of hexagonal tubes
220(3), 220(4) are in arranged in an adjacent and abutting manner
so that the opposing outside surfaces of the hexagonal tubes
220(3), 220(4) are in surface contact. While the second pair of
hexagonal tubes 220(3), 220(4) are aligned with the first pair of
hexagonal tubes 220(1), 220(2) in row 1, they are also spaced so as
to leave room for a first perimeter resultant cell X.
[0136] A two-panel plate structure 225(1) is connected to the left
sides of the hexagonal tubes 220(3), 220(4) to enclose the open
lateral side of the perimeter resultant cell X. Specifically, the
two panel plate structure 225(1) is connected to the hexagonal tube
220(2) and the hexagonal tube 220(3) by welding or another
technique. The perimeter resultant cell X is completed by the
outside surfaces of the hexagonal tubes 220(8), 220(9) located in
row 2. Thus, a complete hexagonal resulting cell X is formed by the
cooperation of the outside surfaces of the hexagonal tubes 220(2),
220(3), 220(8), 220(9) and the plate structure 225(1). The
resultant cell X has a horizontal cross-sectional shape that
corresponds to the shape of all other cells in the fuel rack
200.
[0137] B. Formation of Resultant Perimeter Cells #
[0138] The formation of perimeter resultant cells formed by the
combination of outside surfaces of the hexagonal tubes and a
single-panel plate structure (referred to above as type 201B cells)
will now be described. For ease of reference and to avoid clutter,
all perimeter resultant cells formed by the combination of outside
surfaces of the hexagonal tubes and a single-panel plate structure
are marked with an #.
[0139] Turning now to row 2, the pair of hexagonal tubes 220(8),
220(9) are arranged atop the base plate 210 in an adjacent and
abutting manner with each other and the hexagonal tubes 220(2),
220(3) from row 1. When so arranged, the opposing outside surfaces
of the hexagonal tubes 220(8), 220(9) are in surface contact with
one another. The opposing outside surfaces of the hexagonal tubes
220(8), 220(2) are also in surface contact with one another. And,
the opposing outside surfaces of the hexagonal tubes 220(9), 220(3)
are in surface contact with one another.
[0140] The hexagonal tubes 220(14), 220(15) are arranged in row 3
atop the base plate 210 in an adjacent and abutting manner with
each other and so that the outside surface of the hexagonal tube
220(15) is in surface contact with the outside surface of the
hexagonal tube 220(8) from row 2. A single-panel plate structure
226(1) is connected to the hexagonal tubes 220(1), 220(14) to
enclose the open lateral side of the perimeter resultant cell #.
Specifically, the single-panel plate structure 226(1) is connected
to the hexagonal tube 220(1) and the hexagonal tube 220(14) by
welding or another technique. Thus, a complete hexagonal resulting
cell # is formed by the cooperation of the outside surfaces of the
hexagonal tubes 220(1), 220(2), 220(8), 220(14), 220(15) and the
single-panel plate structure 226(1). The resultant cell # has a
horizontal cross-sectional shape that corresponds to the shape of
all other cells in the fuel rack 200.
[0141] C. Formation of Resultant Perimeter Cells *
[0142] The formation of non-perimeter resultant cells formed
completely by the cooperation of outside surfaces of the
surrounding hexagonal tubes (referred to above as type 201D cells)
will now be described. For ease of reference and to avoid clutter,
all non-perimeter resultant cells formed by the cooperation of the
outside surfaces of the hexagonal tubes are marked with an *.
[0143] In order to avoid redundancy, the arrangement and
interaction of the hexagonal tubes atop the base plate will be
omitted with the understanding that the discussion above is
applicable. In row 2, a complete hexagonal resulting cell * is
formed by the cooperation of the outside surfaces of the hexagonal
tubes 220(3), 220(4), 220(9), 220(10), 220(16), 220(17). The
resultant cell * has a horizontal cross-sectional shape that
corresponds to the shape of all other cells in the fuel rack
200.
[0144] Turning back to the general manufacture and formation of the
fuel rack 200, all connections between the hexagonal tubes 220 and
the base plate 210 are accomplished as described above with respect
to the fuel rack 100. Additionally, connections between adjacent
the hexagonal tubes 220 can be accomplished via the plug holes
described above. Furthermore, in order to ensure that the resultant
cells 201B-D are properly sized, the fuel rack may be formed in the
following manner.
[0145] First, an array of hexagonal tubes 220 are arranged in the
desired geometric configuration so that all six outside surfaces of
all non-perimeter hexagonal tubes 220 are in contact with the
outside surface of the adjacent hexagonal tubes 220. In other
words, at this stage, the fuel rack 200 only comprises cells of the
type 201A that formed by the internal cavities of the hexagonal
tubes 220 themselves. However, due to pre-planning, the location of
those spots which are to be resultant cells 201B-D are noted. The
array of hexagonal tubes 220 are positioned atop the base plate 210
and the necessary welding is performed. However, any hexagonal
tubes 220 that are located in the spots where a resultant cell is
desired are not welded to either the base plate 210 or to the
adjacent hexagonal tubes 220. These hexagonal tubes 220 are then
slidably removed from the array, thereby leaving the resultant cell
201B-D. As necessary, the single-panel plates 226 and the two-panel
plates 225 are then connected to enclose the perimeter resultant
cells 220B-C.
[0146] Furthermore, if desired, neutron absorbing panels can be
added to the array as necessary. The fuel rack 200 does not contain
any flux traps.
III. Slotted-Plate Fuel Rack Embodiment
[0147] Referring now to FIG. 10, a fuel rack 300 that is formed
from a plurality of slotted-plates arranged in a self-interlocking
arrangement is illustrated. The fuel rack 300 is designed so as to
have flux traps 340 and rectangular cells 301. However, it is to be
understood that the slotted-plate concept described below can be
utilized to form non-flux trap fuel racks and can be utilized to
create fuel racks having any shaped cells, including without
limitation the fuel racks discussed above.
[0148] In describing the fuel rack 300 and its component parts
below, relative terms such as top, bottom, above, below,
horizontal, vertical upper and lower will be used in relation to
the fuel rack 300 being in the illustrated substantially vertical
orientation of FIG. 10. Additionally, in order to avoid clutter in
the drawings, only a few of each component are numbered with the
understanding that the reader will be able to identify duplicate
elements.
[0149] Because many of the structural and functional features of
the fuel rack 300 are identical to the fuel racks 100, 200 above,
only those aspect of the fuel rack 300 that are different will be
discussed below with the understanding that the other concepts and
structures discussed above with respect to the fuel racks 100, 200
are applicable.
[0150] The fuel rack 300 generally comprises an array of cells 301
that are formed by a gridwork of slotted plates 370-372 that are
slidably assembled in an interlocking rectilinear arrangement. The
gridwork of slotted plates 370-372 are positioned atop and
connected to a base plate 310. The entire fuel rack body is formed
out of three types of slotted plates, a middle plate 370, a top
plate 371 and a bottom plate 372. The bottom plate comprises the
auxiliary holes 321 as discussed above for facilitating
thermosiphon flow into the cells 301.
[0151] Referring now to FIGS. 11A-11C, one of the middle plates
370, top plates 371 and bottom plates 372 are illustrated
individually. As can be seen, the bottom plate 372 is merely a top
half of the middle plate 370 with the auxiliary holes 321 cutout at
its bottom edge. Similarly, the top plate 371 is merely a bottom
half of the middle plate 370. The bottom and top plates 372, 371
are only used at the bottom and top of the fuel rack body to cap
the middle body segments 380 (FIG. 12) formed from the middle
plates 370 so that the fuel rack body has a level top and bottom
edge.
[0152] Each of the plates 370-372 comprise a plurality of slots 374
and end tabs 375 strategically arranged to facilitate sliding
assembly to create the fuel rack body. The slots 374 are provided
in both the top and bottom edges of the plates 370-372. The slots
374 on the top edge of each plate 370-372 are aligned with the
slots 374 on the bottom edge of that same plate 370-372. The slots
374 extend through the plates 370-372 for one-fourth of the height
of the plates 370-372. The end tabs 375 extend from lateral edges
of the plates 370-372 and are preferably about one-half of the
height of the plates 370-372. The end tabs 375 slidably mate with
the indentations 376 in the lateral edges of adjacent plates
370-372 that naturally result from the existence of the tabs
375.
[0153] The plates 370-372 are preferably constructed of a
metal-matrix composite material, and more preferably a
discontinuously reinforced aluminum/boron carbide metal matrix
composite material, and most preferably a boron impregnated
aluminum. One such suitable material is sold under the tradename
Metamic.TM..
[0154] Referring now to FIG. 12, a single middle segment 380 of the
basket is illustrated. Each middle segment 380 of the fuel rack 300
comprises a gridwork of middle plates 370 arranged in a rectilinear
configuration so as to form a vertical portion of the cells 301 and
the flux traps 340. In creating a middle segment 380, a first
middle plates 370 is arranged vertically. A second middle plate 370
is then arranged above and at a generally 90 degree angle to the
first middle plate 370 so that its corresponding slots 374 are
aligned. The second middle plate 370 is then lowered onto the first
middle plate 370, thereby causing the slots 374 to interlock as
illustrated. This is repeated with all middle plates 370 until the
desired rectilinear configuration is created, thereby creating the
segment 380.
[0155] In creating the fuel rack body, the slots 374 and end tabs
375 of the segments 380 interlock the adjacent segments 380
together so as to prohibit relative horizontal and rotational
movement between the segments 380. The segments 380 intersect and
interlock with one another to form a stacked assembly that is the
fuel rack body. The fuel rack 300 preferably comprises at least
four of the segments 380, and more preferably at least ten segments
380. All of the segments 380 have substantially the same height and
configuration.
[0156] Therefore, the entire fuel rack 300 is formed of slotted
plates 370-372 having what is essentially a single configuration
which is the middle plate 370, with the exception that the top and
bottom plates 371, 372 have to be formed by cutting the middle
plate 370 and adding the cutouts 321.
[0157] Furthermore, as a result of the interlocking nature of the
slotted plates 370-372, spacers are not needed to maintain the flux
traps 340. Thus, in some embodiments, the fuel rack 300 will be
free of spacers in the flux traps 340.
IV. Non-Flux Trap Fuel Basket Embodiment
[0158] Referring to FIGS. 13-17, a fuel basket 1000 according an
embodiment of the present invention is illustrated. The complete
and assembled fuel basket 1000 is shown in FIGS. 15 and 17. While
the fuel basket 1000 (and its components) are described throughout
this specification in conjunction with storing and/or transporting
spent nuclear fuel assemblies having a hexagonally shaped
horizontal cross-sectional profile, the invention is in no way
limited by the type of high level radioactive waste it is use din
conjunction with. The fuel basket assembly 1000 (and its
components) can be used to transport and/or store any shape of fuel
assemblies.
[0159] Referring now to FIG. 13, a perspective view of the storage
grid portion 1001 of the fuel basket 1000 is illustrated. The
storage grid 1001 is a cellular structure comprising a plurality of
tubes 10 forming cells 20 for receiving and holding fuel
assemblies. The tubes 10 form a honeycomb-like grid of cells 20
arranged in a polar configuration. For ease of representation (and
in order to void clutter), only a few of the tubes 10 and the cells
20 are numerically identified in FIG. 13.
[0160] The tubes 10 have a horizontal cross-sectional profile that
is hexagonal in shape. The invention is not so limited however, and
the tubes 10 will have a horizontal cross-sectional profile that
corresponds with the shape of the fuel assembly to be stored within
the cavities 20. For example, other polygonal-shaped SNF assemblies
may be stored in the fuel basket 1000, in which case the tubes 10
will be of the appropriate horizontal cross-sectional shape. The
cells 20 are substantially vertically oriented elongate
spaces/cavities having a generally hexagonal horizontal
cross-sectional configuration. The horizontal cross-sectional
profile of the cells 20 is also not limited to hexagonal, and could
be any shape including other polygons. Each cell 20 is designed to
accommodate a single fuel assembly. The storage grid 1001 (and thus
the cells 20) has a height that is equal to or slightly greater
than the height of the fuel assembly for which the basket 1000 is
designed to accommodate. The fuel basket 1000 preferably comprises
85 cells 20 and has a weight of approximately 4800 lbs.
[0161] Each storage tube 10 comprises five plates 11 having an
inner surface 12 and an outer surface 13. The tubes 10 could have
less or more plates 11 depending upon the desired horizontal
cross-sectional profile. The inner surface 12 of the tubes 10 form
the cells 20. Preferably, the tubes 10 are bundled together in an
axially adjacent arrangement to form a honeycomb storage grid of
cells 20. The tubes 10 are formed by staking tubular segments
10A-10C so as to create cells 20 having a height equal to, or
greater than the height of the fuel assembly to be stored therein.
An interface/junction 21 is formed between the contacting edges of
the tubular segment 10A-10C in each vertical stack that forms the
tube 10. For ease of representation (and in order to void clutter),
only a few of the contact interfaces are numerically identified in
FIG. 13. As will be discussed in further detail below, the tubular
segments 10A-10C are of varying height so that the interfaces 21 of
adjacent tubes 10/cells 20 are not aligned. By ensuring that the
interfaces 21 are not aligned for adjacent tubes 10/cells 20, the
structural integrity of the fuel basket 1000 is enhanced.
[0162] Preferably, the tubes 10 (and tubular segments 10A-10C) are
made by extruding or forming plate stock followed by welding each
of the plates 11 at their lateral edges. The tubes 10 are made of a
material containing a neutron absorber isotope embedded in the
microstructure, such as elemental boron or boron carbide. Metamic,
produced by Metamic, LLC, made of an aluminum alloy matrix with
embedded boron carbide is an example of an acceptable material. In
some embodiments, however, the fuel basket 1000 and its components
can be constructed of alternate materials, such as steel or borated
stainless steel.
[0163] A plurality of cutouts 23 are provided in the plates 11 at
the bottom of the tubes 10. For ease of representation (and in
order to void clutter), only a few of the cut-outs 23 are
numerically identified in FIG. 13. The cutouts 23 form passageways
through the plates 11 so that all of the cells 20 are in spatial
communication. As a result, the cutouts 23 at or near the bottom of
the storage grid 1001 act as a bottom plenum that helps circulate
fluids (air or water) within the fuel basket 1000 (and the cells
20) to effectuate convective cooling of the stored fuel assemblies
during storage and/or transportation. This natural circulation of
air or water can be further facilitated by leaving one or more of
the cells 20 along the periphery of the basket 100 empty so that
they can act as downcomers (the support tubes 30A, 30B can also act
as downcomers if the cutouts are added). The cutouts 23 are
rectangular in shape in the illustrated embodiment but can take on
a wide variety of shapes.
[0164] Referring to FIGS. 13 and 15 concurrently, the storage grid
1001 is formed by a plurality of sections 150A-D of the tubular
segments 10A-10C that are arranged in a stacked assembly. The
sections 150A-D and the tubular segments 10A-C are joined with one
another to form the stacked assembly that is the storage grid 1001.
Each section 150A-D of the storage grid 1001 is a vertical portion
of the storage grid 1001 that itself comprises the honeycomb-like
grid of tubular segments 10A-C arranged in the polar configuration.
The tubular segments 10A-C are of three different heights, each
different height delineated by the letter A-C. A single bottom
section 150A of the storage grid 1001 is illustrated in FIG. 15,
the bottom section 150A having tubular segments 10A-C arranged in a
polar configuration. The bottom edges of the tubular segments 10A-C
are aligned at the same elevation. The two middle sections 150B-C
comprise tubular members 10C, all having the same height. The top
section 150D comprises tubular members 10A-C arranged so that the
top surfaces of the tubular members 10A-C are aligned at the same
elevation.
[0165] The tubular segments 10A have a height that is preferably
equal to one foot. The tubular segments 10B have a height that is
preferably equal to two feet. The tubular segments 10C have a
height that is preferably equal to three feet. The invention is not
so limited however, and the tubular segments 10A-C may be of any
height so long as the cells formed are at least equal to the height
of the fuel assembly. In order to ensure that the interfaces 21 of
adjacent tubes 10 are not aligned, it is preferable that no
adjacent tubular members 10A-C of the bottom section 150A be of the
same height. Thus, when assembling the bottom section 150A, the one
foot tubular segment 10A is surrounded by alternating tubular
members 10B and 10C.
[0166] Referring now to FIGS. 14 and 16, the fuel basket 1000
further comprises a plurality of resultant cells 20A that are
formed by the outer surface 13 of the walls 11 of six of the
tubular members 10. A single resultant cell 20A is illustrated in
FIG. 14. Where six tubular members are joined in a polar
configuration, a resultant cell 20A having a hexagonal horizontal
cross-sectional profile is formed therebetween. This arrangement
allows for less plates 11 (i.e., tubes 10) to be used to create the
same number of cells 20, thereby creating a lighter fuel basket
1000. In the illustrated embodiment there are a total of
twenty-nine resultant cells 20A. The invention is not so limited
however, and the number of resultant cells may vary. The resultant
cells 20A have about a 1/2 inch larger opening and thus can
accommodate fuel assemblies that are damaged or
dimensionally-deviant. Additionally, the resultant cells 20A allow
for the fuel basket 1000 to be fabricated using fillet welds
because the resultant cells provide easier access to the tubes
10.
[0167] As best seen in FIG. 16, some resultant cells 20A that are
located along the periphery of the fuel basket 1000 require the use
of a closure plate 15A-B to complete the cell. The closure plates
15A-B are par-hexagonal plates. The fuel basket assembly 1000
comprises two types of closure plates 15A-B depending on the
configuration of the resultant cell 20A. Some resultant cells 20A
require only a single panel to enclose the cell 20A, while other
resultant cells require two panels to enclose the resultant cell
20A. Where two panels are required, a closure plate 15A is formed
by bending a plate into two panels of equal length and attaching
the lateral edges of the closure plate 15A to the lateral edges of
the tubes 10 that are forming the applicable resultant cell
20A.
[0168] The basket assembly 1000 further comprises basket support
tubes 30A, B placed adjacent the storage grid 1001 along its
periphery. The basket support tubes 30A,B are used to provide
conformal contact with the container/vessel in which the basket
assembly 100 is to be used. The basket support tubes 30A, B
comprise a par-hexagonal plate 31A, B connected to the concave side
of a curved plate 32A, B. The curved plates 32A, 32B form a
substantially circular outer perimeter for the fuel basket 1000.
Because the basket support tubes 30A,B are not located at every
position on the periphery of the storage grid, the substantially
circular outer perimeter is circumferentially segmented.
[0169] For resultant cells 20A that require only a single panel to
form a six-walled cell (i.e., one side is open), the par-hexagonal
plate 31B of the support tubes 30B can also function as a closure
plate. The basket support tubes 30A can be used where there is no
resultant cell 20A, or where the resultant cell 20A is enclosed by
the closure plate 15A.
[0170] Referring now to FIG. 17, the basket support tubes 30A, B
are shown removed from the fuel basket assembly 1000. The basket
support tubes 30A,B are provided so that the basket assembly is
centered within the container (which can be a canister or a cask)
in which it is to be used.
[0171] Referring now to FIG. 18, the basket assembly 100 with the
basket supports 30A, B attached is illustrated. The basket supports
30A, B provide for a circular outer perimeter of the fuel basket
1000. The gaps 31 in the basket supports 30A,B do not have fuel
assemblies stored therein, thus they may improve the cooling of the
fuel assemblies stored in the cells 20.
V. Flux Trap Fuel Basket Embodiment
[0172] Referring now to FIG. 19, a fuel basket 2000 according to
another embodiment of the present invention is illustrated. The
design aspects of the fuel assembly 2000 are substantially similar
to those discussed above with respect to the fuel basket 1000. To
avoid redundancy, only those design aspects of the fuel basket 2000
that substantially differ from the fuel basket 1000 will be
discussed.
[0173] The basket assembly 2000 comprises a plurality of flux trap
spaces 50 that regulate the production of neutron radiation and
prevent reactivity in a flooded condition. The flux traps 50 are
small spaces that extend the height of the basket 2000. The flux
traps 50 are formed between two of the tubular members 210 that are
close to one another and substantially parallel. As will be
discussed below, the flux traps 50 are designed to be of variable
width to maximize the number of fuel assemblies that can be stored
in the fuel basket 2000 while maintaining a reactivity equal to or
less than 0.95. The flux traps 50 are formed between the outer
surface of the storage tubes 2210. The tubes 2210 have a plurality
of spacers 60 that maintain the spacing between tubular members 10
that forms the flux trap 50.
[0174] Referring now to FIG. 20, a single storage tube 2210 is
shown removed from the fuel basket 2000 so that it's design aspects
can be more clearly visible. The storage tube 2210 has a hexagonal
horizontal cross-sectional profile but can be any configuration.
Preferably, the cross-sectional profile will be determined by the
type of fuel assembly to be loaded and stored in the fuel basket
assembly 2000. The tube 2210 comprises a plurality of notches 2215.
The notches 2215 provide spaces through which the spacer 2260
(shown in FIG. 24) can be attached. Preferably, the spacers 60 are
initially tack welded to the tubes 2210 so that the fuel basket
2000 can be assembled. After the fuel basket 2000 is assembled it
is placed on its side and the spacers 2260 that are on the bottom
(closer to the ground surface on which the basket assembly 2000 is
resting) are plug welded to the storage tubes 2210. This allows for
gravity to aid in the welding procedure. The fuel basket 2000 is
rotated so that the next set of spacers 2260 is now closer to the
ground surface for welding to the tubes 2210. The rotating and
welding procedure is repeated for all of the spacers 2260 and tubes
2210.
[0175] Referring to FIGS. 21 and 22 concurrently, the fuel basket
2000 is formed by a plurality of sections 2250A-F of the tubular
segments 2210A-C that are arranged in a stacked assembly. The
sections 2250A-F and the tubular segments 2210A-C are joined with
one another to form the stacked assembly that is the fuel basket
2000. Each section 2250A-F of the fuel basket 2000 comprises a
honeycomb-like grid of tubular segments 2210A-C arranged in the
polar configuration. The tubular members 2210A-C of the basket
assembly 2000 are of three varying heights, each height delineated
by the letter A-C. A single bottom section 2250A of the basket 2000
is illustrated in FIG. 21, the bottom section 2250A has tubular
segments 2210A-C arranged in a polar configuration. The middle
sections 2250B-E comprise tubular segments 2210C, all having the
same height. The top section 2250F comprises tubular segments 210A
arranged so that the top surfaces of the tubular segments 2210A-C
are aligned at the same elevation.
[0176] The storage tubes 2210A have a height that is preferably
equal to one foot. The tubular segments 2210B have a height that is
preferably equal to two feet. The tubular segments 2210C have a
height that is preferably equal to three feet. The invention is not
so limited however, and the tubular segments 2210A-C may be of any
height so long as the cells formed are at least equal to the height
of the fuel assembly. In order that the interfaces 2221 are not
aligned, it is preferable that no adjacent tubular segments 2210A-C
of the bottom section 2250A be of the same height. Thus, when
assembling the bottom section 2250A, the one foot tubular segments
2210A are surrounded by alternating tubular segments 2210B and
2210C. The bottom edges of the tubular segments 2210A-C of the
bottom section 2250A are aligned.
[0177] Referring now to FIG. 23, a top perspective view of the fuel
basket assembly 2000 is illustrated. The basket assembly 2000
comprises three types of spacers 2260A-C that form flux traps 50
between the tubes 2210. The first type of spacer 2260A is a
unilateral triangle that maintains the largest gap between the
tubes 2210 located near the central axis of the basket 2000. In
other words, the spacer 2260A is used with the tubes 2210 that are
closest to the center of the basket 2000 because the neutrons
emitted by the fuel assemblies in the center of the basket 2000
cannot easily escape to the perimeter of the basket assembly 2000.
Thus, for maintaining a reactivity of less than 0.95, a larger flux
trap 50 is required. A second shape of spacer 2260B is used between
the storage tubes 2210 that are nearer the outer perimeter of the
fuel basket 2000. A rectangular spacer 2260C is used for the
storage tubes 2210 that are nearest to the outer perimeter formed
by basket supports 2230A,B.
[0178] The fuel baskets 1000, 2000 of the present invention are not
limited to use with any particular type of surrounding vessels. For
example, in one embodiment, the basket assemblies 1000, 2000 can be
incorporated into a hermetically sealable multi-purpose canister
for use in conjunction with VVO style containment systems. In such
an embodiment, the basket assemblies 1000, 2000 will be provided in
a cavity formed by a cylindrical metal shell. The metal shell will
encircle the basket assembly 1000, 2000 and a metal base plate may
be welded to the bottom of the metal shell. A metal closure plate
can be fitted on top of the cylinder formed by the metal shell,
thereby forming a canister. Thermally conductive casks can also be
used to house the fuel baskets 1000, 2000 directly.
II. Inventive Concept 2
[0179] With reference to FIGS. 25-33, a second inventive concept
will be described.
[0180] Referring to FIG. 25, a dual-walled DSC 3100 according to
one embodiment of the present invention is disclosed. The
dual-walled DSC 3100 and its components are illustrated and
described as an MPC style structure. However, it is to be
understood that the concepts and ideas disclosed herein can be
applied to other areas of high level radioactive waste storage,
transportation and support. Moreover, while the dual-walled DSC
3100 is described as being used in combination with a specially
designed fuel basket 3090 (which in of itself constitutes an
invention), the dual-walled DSC 3100 can be used with any style of
fuel basket, such as the one described in U.S. Pat. No. 5,898,747,
to Krishna P. Singh, issued Apr. 27, 1999. In fact, in some
instances it may be possible to use the dual-walled DSC 3100
without a fuel basket, depending on the intended function.
Furthermore, the dual-walled DSC 3100 can be used to store and/or
transport any type of high level radioactive waste and is not
limited to SNF.
[0181] As will become apparent from the structural description
below, the dual-walled DSC 3100 contains two independent
containment boundaries about the storage cavity 3030 that operate
to contain both fluidic (gas and liquid) and particulate
radiological matter within the cavity 3030. As a result, if one
containment boundary were to fail, the other containment boundary
will remain intact. While theoretically the same, the containment
boundaries formed by the dual-walled DSC 3100 about the cavity 3030
can be literalized in many ways, including without limitation a
gas-tight containment boundary, a pressure vessel, a hermetic
containment boundary, a radiological containment boundary, and a
containment boundary for fluidic and particulate matter. These
terms are used synonymously throughout this application. In one
instance, these terms generally refer to a type of boundary that
surrounds a space and prohibits all fluidic and particulate matter
from escaping from and/or entering into the space when subjected to
the required operating conditions, such as pressures, temperatures,
etc.
[0182] Finally, while the dual-walled DSC 3100 is illustrated and
described in a vertical orientation, it is to be understood that
the dual-walled DSC 3100 can be used to store and/or transport its
load in any desired orientation, including at an angle or
horizontally. Thus, use of all relative terms through this
specification, including without limitation "top," "bottom,"
"inner" and "outer," are used for convenience only and are not
intended to be limiting of the invention in such a manner.
[0183] The dual-walled DSC 3100 dispenses with the single-walled
body concept of the prior art DSCs. More specifically, the dual
walled DSC 3100 comprises a first shell that acts as an inner shell
3010 and a second shell that acts as an outer shell 3020. The inner
and outer shells 3010, 3020 are preferably cylindrical tubes and
are constructed of a metal. Of course, other shapes can be used if
desired. The inner shell 3010 is a tubular hollow shell that
comprises an inner surface 3011, an outer surface 3012, a top edge
3013 and a bottom edge 3014. The inner surface 3011 of the inner
shell 3010 forms a cavity/space 3030 for receiving and storing SNF.
The cavity 3030 is a cylindrical cavity formed about a central
axis.
[0184] The outer shell 3020 is also a tubular hollow shell that
comprises an inner surface 3021, an outer surface 3022, a top edge
3023 and a bottom edge 3024. The outer shell 3020 circumferentially
surrounds the inner shell 3010. The inner shell 3010 and the outer
shell 3020 are constructed so that the inner surface 3021 of the
outer shell 3020 is in substantially continuous surface contact
with the outer surface 3012 of the inner shell 3010. In other
words, the interface between the inner shell 3010 and the outer
shell 3020 is substantially free of gaps/voids and are in conformal
contact. This can be achieved through an explosive joining, a
cladding process, a roller bonding process and/or a mechanical
compression process that bonds the inner shell 3010 to the outer
shell 3020. The continuous surface contact at the interface between
the inner shell 3010 and the outer shell 3020 reduces the
resistance to the transmission of heat through the inner and outer
shells 3010, 3020 to a negligible value. Thus, heat emanating from
the SNF loaded within the cavity 3030 can efficiently and
effectively be conducted outward through the shells 3010, 3020
where it is removed from the outer surface 3022 of the outer shell
via convection.
[0185] The inner and outer shells 3010, 3020 are preferably both
made of a metal. As used herein, the term metal refers to both pure
metals and metal alloys. Suitable metals include without limitation
austenitic stainless steel and other alloys including Hastelloy.TM.
and Inconel.TM.. Of course, other materials can be utilized. The
thickness of each of the inner and outer shells 3010, 3020 is
preferably in the range of 5 mm to 25 mm. The outer diameter of the
outer shell 3020 is preferably in the range of 1700 mm to 2000 mm.
The inner diameter of the inner shell 3010 is preferably in the
range of 1700 mm to 1900 mm. The invention, however, is not limited
to any specific size and/or thickness of the shells 3010, 3020.
[0186] In some embodiments, it may be further preferable that the
inner shell 3010 be constructed of a metal that has a coefficient
of thermal expansion that is equal to or greater than the
coefficient of thermal expansion of the metal of which the outer
shell 20 is constructed. Thus, when the SNF that is stored in the
cavity 3030 emits heat, the outer shell 3020 will not expand away
from the inner shell 3010. This ensures that the continuous surface
contact between the outer surface 3012 of the inner shell 3010 and
the outer surface 3021 of the outer shell 3020 will be maintained
and gaps will not form under heat loading conditions.
[0187] The dual-walled DSC 3100 further comprises a first lid that
acts as an inner top lid 3060 for the inner shell 3010 and a second
lid that acts as an outer top lid 3070 for the outer shell 3020.
The inner and outer top lids 3060, 3070 are plate-like structures
that are preferably constructed of the same materials discussed
above with respect to the shells 3010, 3020. Preferably the
thickness of the inner top lid 3060 is in the range of 100 mm to
300 mm. The thickness of the outer top lid is preferably in the
range of 50 mm to 150 mm. The invention is not, however, limited to
any specific dimensions, which will be dictated on a case-by-case
basis and the radioactive levels of the SNF to be stored in the
cavity 3030.
[0188] Referring now to FIG. 26, the inner top lid 3060 comprises a
top surface 3061, a bottom surface 3062 and an outer lateral
surface/edge 3063. The outer top lid 3070 comprises a top surface
3071, a bottom surface 3072 and an outer lateral surface/edge 3073.
When fully assembled, the outer lid 3070 is positioned atop the
inner lid 3060 so that the bottom surface 3072 of the outer lid
3070 is in substantially continuous surface contact with the top
surface 3061 of the inner lid 3060.
[0189] During an SNF underwater loading procedure, the inner and
outer lids 3060, 3070 are removed. Once the cavity 3030 is loaded
with the SNF, the inner top lid 3060 is positioned so as to enclose
the top end of the cavity 3030 and rests atop the brackets 3015.
Once the inner top lid 3060 is in place and seal welded to the
inner shell 3010, the cavity 3030 is evacuated/dried via the
appropriate method and backfilled with nitrogen, helium or another
inert gas. The drying and backfilling process of the cavity 3030 is
achieved via the holes 3064 of the inner lid 3060 that form
passageways into the cavity 3030. Once the drying and backfilling
is complete, the holes 3061 are filled with a metal or other wise
plugged so as to hermetically seal the cavity 3030.
[0190] Referring now to FIGS. 25 and 27 concurrently, the outer
shell 3020 has an axial length L2 that is greater than the axial
length L1 of the inner shell 3010. As such, the top edge 3013 of
the inner shell 3010 extends beyond the top edge 3023 of the outer
shell 3020. Similarly, the bottom edge 3024 of the outer shell 3020
extends beyond the bottom edge 3013 of the inner shell 3010.
[0191] The offset between the top edges 3013, 3023 of the shells
3010, 3020 allows the top edge 3013 of the inner shell 3010 to act
as a ledge for receiving and supporting the outer top lid 3070.
When the inner lid 3060 is in place, the inner surface 3011 of the
inner shell 3010 extends over the outer lateral edges 3063. When
the outer lid 3070 is then positioned atop the inner lid 3060, the
inner surface 3021 of the outer shell 3020 extends over the outer
lateral edge 3073 of the outer top lid 3070. The top edge 3023 of
the outer shell 3020 is substantially flush with the top surface
3071 of the outer top lid 3070. The inner and outer top lids 3060,
3070 are welded to the inner and outer shells 3010, 3020
respectively after the fuel is loaded into the cavity 3030.
Conventional edge groove welds can be used. However, it is
preferred that all connections between the components of the
dual-walled DSC 3100 be through-thickness weld.
[0192] The dual-walled DSC 3100 further comprises a first plate
that acts as an inner base plate 3040 and a second plate that acts
as an outer base plate 3050. The inner and outer base plates 3040,
3050 are rigid plate-like structures having circular horizontal
cross-sections. The invention is not so limited, however, and the
shape and size of the base plates 3040, 3050 is dependent upon the
shape of the inner and outer shells 3010, 3020. The inner base
plate 3040 comprises a top surface 3041, a bottom surface 3042 and
an outer lateral surface/edge 3043. Similarly, the outer base plate
3050 comprises a top surface 3051, a bottom surface 3052 and an
outer lateral surface/edge 3053.
[0193] The top surface 3041 of the inner base plate 3040 forms the
floor of the cavity 3030. The inner base plate 3040 rests atop the
outer base plate 3050. Similar to the other corresponding
components of the dual-walled DSC 3100, the bottom surface 3042 of
the inner base plate 3040 is in substantially continuous surface
contact with the top surface 3051 of the outer base plate 3050. As
a result, the interface between the inner base plate 3040 and the
outer base plate 3050 is free of gaseous gaps/voids for thermal
conduction optimization. An explosive joining, a cladding process,
a roller bonding process and/or a mechanical compression process
can be used to effectuate the contact between the base plates 3040,
3050. Preferably, the thickness of the inner base plate 3040 is in
the range of 50 mm to 150 mm. The thickness of the outer base plate
3050 is preferably in the range of 100 mm to 200 mm. Preferably,
the length from the top surface of the outer top lid 3070 to the
bottom surface of the outer base plate 3050 is in the range of 4000
mm to 5000 mm, but the invention is in no way limited to any
specific dimensions.
[0194] The outer base plate 3050 may be equipped on its bottom
surface with a grapple ring (not shown) for handling purposes. The
thickness of the grapple ring is preferably between 50 mm and 150
mm. The outer diameter of the grapple ring is preferably between
350 mm and 450 mm.
[0195] Referring now to FIGS. 26 and 28 concurrently, the inner
shell 3010 rests atop the inner base plate 3040 in a substantially
upright orientation. The bottom edge 3014 of the inner shell 3010
is connected to the top surface 3041 of the inner base plate 3040
by a through-thickness single groove (V or J shape) weld. The outer
surface 3012 of the inner shell 3010 is substantially flush with
the outer lateral edge 3043 of the inner base plate 3040. The outer
shell 3020, which circumferentially surrounds the inner shell 3010,
extends over the outer lateral edges 3043, 3053 of the inner and
outer base plates 3040, 3050 so that the bottom edge 3024 of the
outer shell 3020 is substantially flush with the bottom surface
3052 of the outer base plate 3050. The inner surface 3021 of the
outer shell 3020 is also connected to the outer base plate 3050
using a through-thickness edge weld. In an alternative embodiment,
the bottom edge 3024 of the outer shell 3020 could rest atop the
top surface 3051 of the outer base plate 3050 (rather than
extending over the outer later edge of the base plate 3050). In
that embodiment, the bottom edge 3024 of the outer shell 3020 could
be welded to the top surface 3051 of the outer base plate 3050.
[0196] When all of the seal welds discussed above are completed,
the combination of the inner shell 3010, the inner base plate 3040
and the inner top lid 3060 forms a first hermetically sealed
structure surrounding the cavity 3030, thereby creating a first
pressure vessel. Similarly, the combination of the outer shell
3020, the outer base plate 3050 and the outer top lid 3070 form a
second sealed structure about the first hermetically sealed
structure, thereby creating a second pressure vessel about the
first pressure vessel and the cavity 3030. Theoretically, the first
pressure vessel is located within the internal cavity of the second
pressure vessel. Each pressure vessel is engineered to autonomously
meet the stress limits of the ASME Code with significant
margins.
[0197] Unlike the prior art DSC, all of the SNF stored in the
cavity 3030 of the dual-walled DSC 3100 share a common confinement
space. The common confinement space (i.e., cavity 3030) is
protected by two independent gas-tight pressure retention
boundaries. Each of these boundaries can withstand both
sub-atmospheric supra-atmospheric pressures as needed, even when
subjected to the thermal load given off by the SNF within the
cavity 3030.
[0198] Referring now to FIG. 29, the dual-walled DSC 3100 is
illustrated having a fuel basket 3090 positioned within the cavity
3030 in a free-standing orientation. The fuel basket 3090 serves to
hold and support a plurality of SNF rods (which are located within
fuel tubes 3091) in the desired arrangement and maintains the
desired separate locality. The fuel basket 3090 comprises a
plurality of disk-like grates 3092 arranged in a stacked and spaced
orientation. The separation between the disk-like grates 3092 is
accomplished via a plurality of vertically oriented tie-rods that
pass through the cells of the disk-like grates 3092. Once the tie
rods are in place, one of the disk-like grates 3092 is slid into
position. Tubular sleeves that can not pass through the cells are
then placed over the tie-rods and above the disk-like grates 3092
in place. The next disk-like grates 3092 is then slid down the tie
rods. However, because the tubular sleeves can not pass through the
disk-like grates 3092, the two disk-like grates 3092 are maintained
in the spaced relation.
[0199] The grates 3092 are disc-like frames comprising a ring 3185
and a plurality of series of beams 3182, 3183, 3184. The outer
surface 3186 of the ring 3185 is in surface contact with the inner
surface 3011 of the inner shell 3010. The outer diameter of the
disk-like grate 3092 is preferably 1700 mm to 1900 mm. The outer
diameter, however, is dependent upon the size of the cavity
3030.
[0200] In the illustrated embodiment, the number of grates 3092 is
nine, and the thickness of each grate 3092 is preferably between 1
mm and 10 mm. However, the invention is not so limited, so long as
the SNF rods are adequately supported within the cavity 3030.
[0201] Referring now to FIGS. 29 and 30, concurrently, the fuel
basket 3090 further comprises a plurality of ventilate fuel tubes
3091. As will be discussed in greater detail below, when assembled,
the ventilated fuel tubes 3091 are inserted through the cells 3180
of the stack of grates 3092, which are aligned. The ventilated fuel
tubes 3091 form cylindrical cavities 3193 (FIG. 33) in which the
SNF rods will reside. Preferably, the fuel cells 3180 around the
outer perimeter of the grates 3092 (i.e. the slots 180 nearest to
the inner surface 3011 of the inner shell 3010) remain free of SNF
rods.
[0202] Referring now to FIG. 31, the grates 3092 also comprise a
plurality of smaller cells 3181 for slidably receiving poison rods
3093. The poison rods 3093 are provided between the loaded fuel
tubes 3091 to control reactivity in necessary cases. The number of
poison rods 3093 is selected to ensure that the computed k.sub.eff
of the SNF rods at maximum design basis initial enrichment, with no
credit for burn up, and with the inclusion of all uncertainties and
biases is less than 0.95. However, in some embodiments, the poison
rods 3093 may not be required at all.
[0203] The pitch P between each of the ventilated fuel tubes 3091
is between 100 mm and 150 mm. The invention is not so limited
however, and the pitch between the ventilated fuel tubes 3091 is
affected by both the size of the cavity 3030 and the number and
location of the poison rods 3093, and the radioactivity of the load
to be stored.
[0204] Referring now to FIG. 32, a top view of one of the grates
3092 is illustrated. The grate 3092 is a honey-comb grid like
structure. The grates 3092 comprise a ring structure 3185, a first
series of substantially parallel beams 3182, a second series of
substantially parallel beams 3183 and a third series of
substantially parallel beams 3184. The ring structure 185
encompasses the first, second and third series of substantially
parallel beams 3182-3184. The entire grate 3092 can be constructed
of a metal, such as steel or aluminum, or any of the materials
discussed above.
[0205] The first, second and third series of substantially parallel
beams 3182-3184 are arranged within the ring structure 3185 so that
each one of the series of beams 3182-3184 intersects with the other
two series of beams 3182-3184. The intersection of the series beams
3182-3184 forms a gridwork that results in an array of fuel cells
3180 and an array of poison rod cells 3181. More specifically, the
general outline of the fuel cells 3180 is created by the
intersection of the first and second series of beams 3182, 3183
while the poison rod cells 3181 are created by the intersection of
the third series of beams 3184 with the first and second series of
beams 3182, 3183. When assembled, the fuel cells 3180 receive the
fuel tubes 3091 while the poison rod cells 3181 receive the poison
rods 3093. As can be seen the poison rod cells 3181 are smaller and
of a different shape than the fuel cells 3180.
[0206] The relative arrangement of first, second and third series
of substantially parallel beams 3182-3184 with respect to one
another is specifically selected to create hexagonal shaped fuel
cells 3180 and triangular shaped poison cells 3181. Of course,
additional series of beams and/or arrangement can be used to create
cells that have different shapes, including octagonal, pentagonal,
circular, square, etc. The desired shape may be dictated by the
shape of the fuel tube and SNF fuel assembly to be stored.
[0207] The series of beams 3182, 3183, 3184 are rectangular strips
(i.e., elongated plates) having notches (not visible) strategically
located along their length to facilitate assembly. More
specifically, notches that extend into the edges of the beams for
at least 1/2 the height of the beams are provided. The notches are
arranged on the beams 3182-3184 so that when the beams 3182-3184
are arranged in the desired gridwork, the notches of the bottom
edge of some beams 3182-3184 are aligned with the notches on the
top edge of the remaining beams 3182-3184. The beams 3182-3184 can
then slidably mate with one another via the interaction between the
notches.
[0208] The beams 3182, 3183, 3184 are then welded to each other at
their intersecting points via tungsten inert gas process. While the
beams 3182-3184 are illustrated as strips, the invention is not so
limited and other structures may be used to form the gridwork, such
as rods.
[0209] Referring now to FIG. 33, the structure of the poison rods
3093 and the ventilated fuel tubes 3091 will be described. In the
illustrated embodiment, the poison rods 3093 are hollow tubular
members having a cavity 3196 for receiving a neutron absorbing
material. For example, the hollow tubular member can be constructed
of a stainless steel and filled with boron-carbide powder. In other
embodiment, the poison rods 3093 can be constructed of a monolithic
material, such as a metal matrix material, such as Metamic.TM..
[0210] The outer diameter of the poison rods 3093 is between 20 mm
and 40 mm and the inner diameter is between 10 mm and 40 mm. The
invention is not so limited, however. When assembled in the DSC
3100, the poison rods 3093 are of a sufficient length so as to
extend along the full height of the SNF rods stored within the fuel
tubes 3091.
[0211] Turning now to the fuel tubes 3091, the ventilated fuel
tubes 3091 are designed to allow for ventilation of heat emitted by
the SNF rods 3200 stored therein. The ventilated fuel tube 3091
comprises a tubular body portion 3191 and a ventilated cap portion
3192. The tubular body portion 3191 forms a cavity 3193 for
receiving the SNF rods 3200, e.g., in the form of fuel bundles
(half fuel assemblies). Preferably, the ventilated fuel tubes 3091
have a horizontal cross sectional profile such that the cavity 3193
accommodates no more than one fuel bundle. However, this is not
limiting of the invention. The outer and inner diameter of the
tubular body portion 3191 of the ventilated fuel tube 3091 is
preferably between 75 mm and 125 mm, but the invention is not so
limited.
[0212] The tubular body portion 3191 comprises a closed bottom end
3194 and open top end 3197. The closed bottom end 3197 is a tapered
and flat bottom. As will be discussed in further detail below, the
tapering of the closed bottom end 3197 allows for better air flow
through the dual walled DSC 3100. In an alternative embodiment, the
closed bottom end 3197 could further comprise holes and/or vents
for improved air flow and heat removal. The ventilated cap portion
3192 is connected to the open top end of the body portion 3191 once
the cavity 3193 is filled with the SNF rods 3200. The cap portion
3192 is a non-unitary structure with respect to the tubular body
3191 and removable therefrom. The caps 3192 prevent any of the
solid contents from spilling out during handling operations in the
processing facility.
[0213] The caps 3192 of the tubes 391 comprise one or more openings
3195 that provide passageways into the cavity 3193 from the cavity
3030. The openings 3195 are covered with fine-mesh screen (not
visible) so as to prevent any build-up of pressure in the fuel tube
3191 while containing any small debris within the cavity 3193 of
the tube 3091. It has been discovered that one inherent flaw in the
design of the NUHOMS DSC is that the hermetically sealed fuel tube
creates a mini-pressure vessel around the SNF rods stored therein.
Because of the small confinement space/volume available in the
hermetically sealed fuel tube of the NUHOMS DSC, even a small
amount of water or release of plenum gas from the inside of the SNF
rods can raise the internal pressure in the fuel tube steeply,
rendering it susceptible to bursting. As a result, the integrity of
the fuel tube of the NUHOMS DSC as a pressure vessel can not be
assured when used to store previously waterlogged SNF rods that
contain micro-cracks with a high level of confidence. The
ventilated fuel tubes 3091 of the present invention, on the other
hand, prevent pressure build-up by allowing ventilation with the
larger cavity 3030 via the opening 3195 in the cap 3192. The
openings 3195 are generally triangular in shape, but can be
circular, rectangular or any other shape, so long as the proper
venting is achieved.
[0214] Referring again to FIG. 29, when the ventilated fuel tubes
3092 are positioned in the dual walled DSC 3100, a plenum exists
between the top of the ventilated fuel tubes 3091 and the bottom
surface 3062 of the inner top lid 3060. As mentioned previously, it
is also preferable that the perimeter of the grid plate 3092 remain
free of fuel tubes 3091.
III. Inventive Concept 3
[0215] With reference to FIGS. 34-42, a third inventive concept
will be described.
[0216] FIG. 34 is a front perspective view of a low profile
transporter ("LPT") 4100. The LPT 4100 translates casks that are
used in the handling and storing of spent nuclear fuel, such as
storage casks used in the long-term dry storage of spent nuclear
fuel. The LPT 4100 is not limited to storage casks, however and
other types of casks and/or structures can be translated in the LPT
4100. The LPT 4100 supports and translates loads in excess of 200
tons and high overturning moments without deforming. As will be
discussed below, the LPT 4100 carries the cask close to the ground
while avoiding interference with the irregularities in the ground
surface. The LPT 4100 can either ride in tracks 4090 on the ground
surface 4006 (shown in FIG. 42) or move along the ground surface
4006 itself. Preferably, as will be discussed in greater detail
below, the LPT 4100 supports and translates a cask so that the top
surface of the cask is less than 24 feet from the ground.
Additionally, the LPT 4100 has a width W1 that allows it to fit
through standard over head door. The LPT 4100 is designed so that
its width W1 is smaller than its length.
[0217] Referring to FIGS. 34 and 35, the LPT 4100 generally
comprises a body 4010 and roller assemblies 4060. The body 4010 has
an open top end 4012 and a cavity 4023 for receiving a cask. The
cavity 4023 has a horizontal cross-sectional profile that is
circular. The diameter of the cavity 4023 is slightly larger than
the diameter of the cask 4200 (shown in FIG. 40) to be loaded
therein. Preferably, there is a small clearance between the cask
4200 (shown in FIG. 40) and the body 4010 equal to about 1/2 inch
to 1 inch. The invention is not so limited however, and the size
and shape of the cavity 4023 will vary depending upon the size and
shape of the cask to be positioned therein so long as the small
clearance is maintained between the cask and the body 10.
[0218] The roller assemblies 4060 include rollers 4061 that allow
for the translation of the LPT 4100. The roller assemblies are
positioned at opposite ends of the LPT 4100 so that the width W1 of
the LPT 4100 is minimized. When the LPT 4100 is in motion, the
rollers 4061 are at the lead and trail ends of the motion. This
makes it easier for the LPT 4100 to fit through narrow passageways
like overhead doors. Additionally, as will be discussed in further
detail below with reference to FIGS. 37 and 38, the roller
assemblies 4060 are designed so that the rollers 4061 can be
extended and retracted in the vertical direction between a fully
extended position and a fully retracted position. When the rollers
4061 are in the extended position, the rollers 4061 contact the
ground and support the full weight of the ZPT 4100 and its load.
When the rollers 4061 are in the retracted position, they are moved
in the vertical direction so as to be raised from the ground so
that the rollers no longer support the weight of the LPT 4100 or
its load. Preferably, when the rollers 4061 are in the fully
extended position, the height of the LPT 4100 is less than 37
inches.
[0219] The body 4010 comprises a ring 4020, an upper plate 4040 and
a lower plate 4050. The ring 4020 has an outer surface 4021, an
inner surface 4022, a top surface 4024 and a bottom surface 4025.
The ring 4020 is preferably made of steel between 2 and 4 inches in
thickness. The invention is not so limited, however, and other
materials, including but not limited to other metals, may be used.
The thickness of the ring 4020 will vary depending upon the
material used to form the ring 4020. The inner surface 4022 of the
ring 4020 forms the cavity 4023 for receiving a cask. The ring 4020
further comprises a plurality of notches 4026 at the bottom surface
4025. The notches 4026 are rectangular shaped cutouts that will be
discussed in more detail below.
[0220] The upper plate 4040 and the lower plate 4050 are connected
to the outer surface 4021 of the ring 4020 and provide structural
robustness to the LPT 4100. The upper plate 4040 is connected to
the outer surface 4021 of the ring 4020 at or near the top surface
4024. The upper plate 4040 extends laterally from the outer surface
4021 of the ring 4020. The upper plate 4040 comprises a top surface
4041 and a bottom surface 4042. The ring 4020 is fitted into an
opening (not visible) in the upper plate 4040 and then the upper
plate 4040 and the ring 4020 are welded together along their
connection area. Other attachment means between the ring 4020 and
the upper plate 4040 may be used, such as bolts, fasteners and/or
fastening techniques, if desired. Alternatively, the ring 4020 and
the upper plate 4040 could be a unitary structure. The upper plate
4040 is preferably made of steel and/or other metals. Where the
upper plate 4040 is made of steel, it is preferably between 1 and 2
inches thick.
[0221] The lower plate 4050 is connected to the ring 4020 at or
near the bottom surface 4025 of the ring 4020. The lower plate 4050
comprises a top surface 4051 and a bottom surface 4052. The ring
4020 is fitted into an opening (not visible) in the lower plate
4050 and the ring 4020 and the lower plate 4050 are then welded
together along their contact area. Other attachment methods may be
used however including mechanical means like bolts, fasteners and
the like. The lower plate 4050 is preferably made of steel having a
thickness of between 1 and 2 inches. The invention is not so
limited, however, and other materials of various thicknesses may be
used.
[0222] The body 4010 of the LTP 4100 further comprises cover plates
4016. The cover plates 4016 are positioned spaced from the outer
surface 4021 of the ring 4020 and extend from the bottom surface
4042 of the upper plate 4040 to the top surface 4051 of the lower
plate 4050. The cover plates 4016 are preferably made of steel or
another metal. The invention is not so limited, however, and other
materials may be used. The cover plates are preferably welded to
the upper and lower plates 4040, 4050. Other attachment means may
be used however, including, mechanical means such as brackets,
bolts, fasteners and the like.
[0223] The upper plate 4040 and the lower plate 4050 protrude at
the front and rear end of the LPT 4100 so as to form the top and
bottom, respectively of two housings 4030 for the roller assemblies
4060. The housings 4030 for the roller assemblies 4060 are
positioned equidistant from each other, or 180 degrees apart. Each
housing 4030 comprises two outer plates 4031 and two inner plate
4032 that surround the roller assemblies 4060. The outer plates and
the inner plates 4031, 4032 extend laterally from the cover plate
4016 to the lateral edge of 4053 of the lower plate 4050. The outer
and inner plates 4031, 4032 additionally extend from the bottom
surface 4042 of the upper plate 4040 to the top surface 4051 of the
lower plate 4050. Preferably, the outer plates 4031 of the housing
4030 are welded to the cover plate 4016 and to the upper and lower
plates 4040, 4050. Other attachment means may be used, including
mechanical means such as fasteners, bolts, brackets and the like.
The inner and outer plates 4031, 4032 are preferably 2 to 4 inches
thick and made of steel. Other materials of different thicknesses
may be used however, including other metals, so long as the
robustness of the LPT 100 is maintained.
[0224] The housing 4030 further comprises a plurality of
reinforcement plates 4033 for structural stability. There are three
reinforcement plates 4033 positioned between the inner plates 4032
and extending from the top plate 4040 to the bottom plate 4050.
Preferably, the reinforcement plates 4033 are welded to the top
plate and the bottom plate 4050, but other attachment means may be
used. The reinforcement plates 4033 extend laterally from the cover
plate 4016 to the lateral edge 4053 of the lower plate 4050 and are
preferably welded to the cover plate 4016.
[0225] The LPT 4100 further comprises a plurality of support
members 4070. In the illustrated embodiment there are four support
members 4070. The invention is not so limited, however, and more or
less support members 4070 may be used so long as they can support
the weight of a fully loaded storage cask. In operation, the
support members 4070 contact a cask to be supported and translated
in the LPT 4100. Each one of the support members 4070 comprises a
contact plate 4072 and three support plates 4074. As will be
discussed in further detail with reference to FIG. 36, the support
plates 4074 are L-shaped plates having a portion which extends into
the cavity 4023 near the bottom of the cavity 4023. The support
plates 4074 extend through the notches 4026 in the ring 4020. The
notches 4026 are slightly larger than the support plates 4071 in
order provide a passageway for the support plates 4074 of the
support members 4070 to extend through the ring 4020 into the
cavity 4023. Preferably the support plates 4071 are welded to the
ring 4020 so that there is no movement between the support members
4070 and the ring 4020. The contact plate 4072 is connected with
the portion of support plate 4074 that extends into the cavity
4023. The contact plate 4072 also contacts and supports a shoulder
of the cask. The shoulder of the cask could either be an opening or
cutout in an outer surface of the cask or a ledge, ridge, flange or
other protrusion from the outer surface of the cask. The contact
plate 4072 is a rectangular plate made of two sections, a top
section 4075 and a bottom section 4076. The top section 4075 is in
surface contact with the cask and is therefore made of a softer
material so as to not damage the cask. The bottom section 4076 is
made of steel of another metal. The top section and bottom section
4075, 4076 of the contact plate 4072 are connected to each other
using either mechanical means, welding or gluing. The contact plate
4072 is positioned near the bottom of the cavity 4023 and is
sufficiently robust to support the weight of a cask loaded into
cavity 4023. Additionally, the contact plate 4072 could be a ring
rather than rectangular plates, additionally, the contact plate
4052 could be a bar extending the entire diameter of the body 4020,
so long as a surface that engages the cask is created.
[0226] Referring now to FIG. 36, the LPT 4100 is shown with a cover
plate 4016 removed on one side. The support plates 4074 of the
support members 4070 are attached to the outer surface 4022 of the
ring 4020. The support plates 4074 extend from the bottom surface
4042 of the upper plate 4040 and through slots in the bottom plate
4050 so that a bottom portion of the support plates 4074 extends
through the bottom plate 4050. The support plate 4074 additionally
extends laterally from the body 4020 to the cover plate 4016 (shown
in FIG. 35). The support plate 4074 is preferably welded to the
body 4020, but other attachment means may be used. Each support
member 4070 comprises three support plates 4074, but the invention
is not so limited, and more or less support plates 4074 may be used
so long as the support member 4070 is able to withstand the weight
of a fully loaded storage cask without deforming.
[0227] The LPT 4100 further comprises a plurality of reinforcement
plates 4045 attached to the outer surface 4021 of the ring 4020 to
provide structural integrity. The reinforcement plates 4045 are
arranged in series around the outer surface 4023 of the ring 4020.
FIG. 36 shows three reinforcement plates 4045. The invention is not
so limited however and there could be less or more reinforcement
plates 4045 per group, arranged closer or farther apart along the
ring 4020. The reinforcement plates 4045 are generally rectangular
in shape and preferably made of steel and/or other metals. The
invention is not so limited however, and the shape and material of
the reinforcement plates 4045 can vary. The reinforcement plates
4045 extend between the top and bottom plates 4040, 4050 and are
preferably attached to the top and bottom plates 4040, 4050 by
welding. Other attachment means may be used, such as bolts,
fasteners and/or fastening techniques, if desired.
[0228] Referring now to FIG. 37, a close-up view of section XXXVII
of FIG. 36 showing the roller assembly 4060 is illustrated so that
its various components and their interaction with one another is
more clearly visible. The roller assembly 4060 comprises rollers
4061, a horizontal beam 4062, a jack 4063, a locking ring 4064,
low-friction plates 4065 and base plate 4066. The jack 4063 is
designed to raise and lower the rollers 4061 between the fully
extended position (illustrated) and the fully retracted position
(not shown). When the rollers 4061 are in the fully retracted
position, they do not contact a ground surface.
[0229] As shown in FIG. 35, the LPT 4100 comprises four roller
assemblies each having a jack 4063. The four jacks 4063 are
hydraulic jacks having hydraulic hoses (not illustrated) extending
from a power skid unit (not illustrated) comprises controls for
operating the jacks 4063. The jacks 4063 are designed to work in
conjunction with each other so that no jack 4063 will lift or lower
the roller 4061 independent of the other jacks. This avoids the
tipping of the LPT 4100. Additionally, other means of controlling
the jacks 4063 may be used including via motors that powered
remotely of the LPT 4100. The locking ring 4064 is designed to keep
the jack 4063 from accidentally releasing and thereby dropping the
load in the LPT 4100. The locking ring 4064 is a metal ring that is
threaded on its inner surface. When the jack 4063 is powered so
that the rollers 4061 are in the extended position, the locking
ring is locked into place so that loss of hydraulic power to the
jack 4063 will not cause the load to be dropped. The rollers 4061
are bolted to the base plate 4066 which comprises an indentation
4068 (shown in FIG. 38) for the cylinder of the jack 4063. The
indentation 4068 keeps the jack 4063 from moving in the lateral
direction.
[0230] The base of the jack 4063 is connected to the horizontal
beam 4062. The horizontal beam 4062 is a steel I-beam that spans
between the inner plate 4031 and the outer plate 4032. The ends of
the horizontal beam 4063 extend through openings in the inner and
outer plates 4031, 4032. A cover is put on the end of the
horizontal beam 4063 that protrudes from the outer plate 4032. The
cover is bolted to the outer surface of the outer plate 4031.
[0231] The low-friction plates 4065 are rectangular shaped pads
made of nylon or another low-friction material having the
capability to withstand high compression loads. The low-friction
plates 4065 are positioned between a vertical beam 4069 and the
outer and inner plates 4031, 4032 of the housing 4030. When the
jack 4063 moves the rollers vertically, the low-friction plates
4065 move along the outer and inner plates 4031, 4032. The low
friction plates 4065 provide support for the roller assembly 4060
so that the rollers 4061 do not supinate or pronate, meaning the
roller assembly 4060 does not bend inwards or outwards
(horizontally) at any point from the moment forces caused by the
weight of the load in the LPT 4100. Rather the roller assembly 4060
moves only vertically.
[0232] The roller assembly 4060 further comprises a shim 4067. The
shim 4067 is preferably a rectangular thin metal plate, such as
steel or aluminum. The shim 4067 can be constructed of other
materials and in other shapes if desired. The shim 4067 provides a
simple way to change the overall height of the LPT 4100 because the
height of the shim 4067 can be easily varied. The shims 4067 are
positioned between the base plate 4066 and the rollers 4061. The
rollers 4061 are best illustrated in FIG. 38.
[0233] Referring to FIG. 38, a roller 4061 is illustrated removed
from the LPT 4100. Although a particular roller design is
illustrated, the rollers 4061 can be any kind of linear motion
device including devices commercially available. The rollers 4061
comprise wheels 4092, inner plate 4093 and outer plate 4094. The
inner and outer plates 4093, 4094 keep the wheels 4092 vertically
in line so that they do not supinate or pronate. The inner and
outer plates 4093, 4094 additionally act as a connection to a rail
of a track (shown in FIG. 41) in the ground surface that may be
used with the LPT 4100.
[0234] Referring now to FIG. 39, a cask 4200 is shown positioned
above the LPT 4100. A cutout 4210 can be seen in the bottom surface
4212 of the cask 4200. As stated previously, the cask 4200 could
have a ridge or lug extending outwardly to engage with support
members 4070. The cutout 4210 is aligned with the contact plate
4072 so that the cask 4200 can be lowered through the open top end
of the body 4020, into the cavity 4023 until the contact plate 4072
slides through the cutout 4210 and engages the cask 4200, as shown
in FIG. 40.
[0235] Referring now to FIG. 40, the cask 4200 is shown positioned
in the LPT 4100. The contact plates 4072 are positioned close to
the bottom plate 4050 of the LPT 4100 so that when the cask 4200
rests on the support members 4070, the cask 4200 can sit as close
to the ground floor 4006 as possible without the bottom surface
4212 engaging the irregularities in the floor surface 4006 (shown
in FIG. 41). Preferably the distance between the bottom surface
4212 of the cask 4200 and the surface of the ground floor 4006 is
between 0.1 and 6 inches, more preferably between 0.1 and 3 inches,
and most preferably between 0.1 and 1 inch.
[0236] Referring now to FIG. 41, the LPT 4100 is designed to glide
along rails 4090 of a ground floor 4006. More specifically rollers
4060 are designed to fit within rails 4090 so that the LPT 4100 can
be laterally moved (i.e. translated) along the floor 4006. The
bottom surface of container 4212 does not touch the floor 4006. The
LPT 4100 is designed so that the loaded container 4200 can be
transported underneath a doorway 4014 (shown in FIG. 42).
[0237] Referring to FIGS. 39 through 41, a method of supporting and
translating a storage cask 4200 will now be discussed. The LPT 4100
is positioned on the ground surface 4006. The cask 4200 is raised
using a transporter 4220 or any other crane like apparatus so that
the bottom surface 4212 of the cask 4200 clears the tops surface of
the upper plate 4040 of the LPT 4100. The cutouts 4210 in the
bottom surface 4212 of the cask 4200 are aligned with the contact
plates 4072 of the support members 4070. the cask is lowered
through the open top 4012 end of the body 4010 and into the cavity
4023 of the LPT 4100. The cask 4200 is lowered until the cutouts
4210 of the cask 4200 are resting on the contact plate 4072 of the
support members 4070. The rollers 4061 are vertically moved into
the extended position so that the rollers contact the ground
surface 4006. The LPT 4100 is translated along the rails 4090 (or
on a ground surface having no rails). The rollers 4061 are
vertically moved so as to be raised from the ground surface. The
support members 4074 contact the ground surface 4006 and the
rollers 4061 no longer support any weight of the LPT 4100 or cask
4200. Spent nuclear fuel is then loaded into the cask 4200 by means
known in the art. Such means of transferring spent nuclear fuel
into storage casks including by resting a transfer cask (not shown)
on top of the cask 4200 so that the spent nuclear fuel can be
transferred from the transfer cask into the storage cask. In such a
transfer method, the full weight of the transfer cask and the cask
4200 are supported by the LPT 4100. The transfer cask is then
removed from the cask 4200. The rollers 4061 of the LPT 4100 are
vertically moved into the extended position so that the rollers
contact the ground surface 4006. The LPT 4100 and the fully loaded
cask 4200 are then translated. The LPT 4100 and the cask 4200 may
be translated underneath overhead door 4014. The LPT 4100 can
engage with the cask transporter 4220 so that the cask 4200 can be
raised out of the cavity 4023 until the bottom surface 4210 of the
cask 4200 clears the top surface of the upper plate 4040. The LPT
4100 can be translated from underneath the cask 4200 and the cask
4200 lowered to the ground surface 4006.
[0238] While the foregoing description and drawings represent some
example systems, it will be understood that various additions,
modifications and substitutions may be made therein without
departing from the spirit and scope and range of equivalents of the
accompanying claims. In particular, it will be clear to those
skilled in the art that the present invention may be embodied in
other forms, structures, arrangements, proportions, sizes, and with
other elements, materials, and components, without departing from
the spirit or essential characteristics thereof. In addition,
numerous variations in the methods/processes described herein may
be made. One skilled in the art will further appreciate that the
invention may be used with many modifications of structure,
arrangement, proportions, sizes, materials, and components and
otherwise, used in the practice of the invention, which are
particularly adapted to specific environments and operative
requirements without departing from the principles of the present
invention. The presently disclosed embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being defined by the appended claims and
equivalents thereof, and not limited to the foregoing description
or embodiments. Rather, the appended claims should be construed
broadly, to include other variants and embodiments of the
invention, which may be made by those skilled in the art without
departing from the scope and range of equivalents of the
invention.
* * * * *