U.S. patent application number 14/528123 was filed with the patent office on 2018-01-25 for seismic attenuation system for a nuclear reactor.
The applicant listed for this patent is NuScale Power, LLC. Invention is credited to Seth Cadell, Tamas LISZKAI.
Application Number | 20180025795 14/528123 |
Document ID | / |
Family ID | 52273472 |
Filed Date | 2018-01-25 |
United States Patent
Application |
20180025795 |
Kind Code |
A9 |
LISZKAI; Tamas ; et
al. |
January 25, 2018 |
SEISMIC ATTENUATION SYSTEM FOR A NUCLEAR REACTOR
Abstract
A system for attenuating seismic forces includes a reactor
pressure vessel containing nuclear fuel and a containment vessel
that houses the reactor pressure vessel. Both the reactor pressure
vessel and the containment vessel may include a bottom head.
Additionally, the system may include a base support that is
configured to contact a support surface on which the containment
vessel is positioned in a substantially vertical orientation. An
attenuation device may be located between the bottom head of the
reactor pressure vessel and the bottom head of the containment
vessel. Seismic forces that travel from the base support to the
reactor pressure vessel via the containment vessel may be
attenuated by the attenuation device in a direction that is
substantially lateral to the vertical orientation of the
containment vessel.
Inventors: |
LISZKAI; Tamas; (Corvallis,
OR) ; Cadell; Seth; (Corvallis, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NuScale Power, LLC |
Corvallis |
OR |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20160125964 A1 |
May 5, 2016 |
|
|
Family ID: |
52273472 |
Appl. No.: |
14/528123 |
Filed: |
October 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61922541 |
Dec 31, 2013 |
|
|
|
Current U.S.
Class: |
376/277 |
Current CPC
Class: |
G21C 1/32 20130101; Y02E
30/30 20130101; G21C 1/322 20130101; Y02E 30/00 20130101; G21C 9/04
20130101; G21C 5/10 20130101; G21C 9/00 20130101; G21C 13/024
20130101; G21D 1/00 20130101; G21D 3/04 20130101; G21C 13/04
20130101; G21C 13/032 20130101 |
International
Class: |
G21C 9/04 20060101
G21C009/04 |
Goverment Interests
GOVERNMENT INTEREST
[0002] This invention was made with Government support under
Contract No. DE-NE0000633 awarded by the Department of Energy. The
Government has certain rights in this invention.
Claims
1. A system for attenuating seismic forces in a reactor assembly
comprising: a containment vessel configured to be located above a
support surface; a reactor pressure vessel mounted within the
containment vessel; and an attenuation device located along a
longitudinal centerline of the reactor pressure vessel and
configured to attenuate seismic forces which are transmitted from
the support surface to the reactor pressure vessel via the
containment vessel, wherein the seismic forces are attenuated by
the attenuation device in a substantially transverse direction to
the longitudinal centerline.
2. The system of claim 1, wherein the attenuation device is
configured to provide for a thermal expansion of the reactor
pressure vessel within the containment vessel.
3. The system of claim 2, wherein the attenuation device comprises
a substantially vertical protrusion that extends within an adjacent
vessel recess, and wherein the vessel recess comprises a vertical
clearance to account for the thermal expansion of the reactor
pressure vessel along the longitudinal centerline.
4. The system of claim 3, wherein the vertical protrusion comprises
a diameter, and wherein the vessel recess further comprises an
annular-shaped clearance to account for the thermal expansion of
the diameter of the vertical protrusion.
5. The system of claim 1, further comprising a support structure
located in an upper half of the containment vessel and configured
to support the reactor pressure vessel within the containment
vessel, wherein the attenuation device is located in the bottom
half of the containment vessel.
6. The system of claim 5, wherein a majority of reactor pressure
weight is supported by the support structure, and wherein
substantially none of the reactor pressure weight is supported by
the attenuation device.
7. The system of claim 1, wherein the containment vessel comprises
a cylindrical-shaped support skirt that contacts the support
surface, wherein a bottom head of the containment vessel is located
some distance above the support surface, and wherein the support
skirt comprises through-holes configured to allow coolant to flow
through the support skirt and contact the bottom head.
8. A system for attenuating seismic forces comprising: a reactor
pressure vessel containing nuclear fuel, wherein the reactor
pressure vessel comprises a bottom head; a containment vessel that
houses the reactor pressure vessel, wherein the containment vessel
comprises a bottom head; a base support that is configured to
contact a support surface on which the containment vessel is
positioned in a substantially vertical orientation; and an
attenuation device located between the bottom head of the reactor
pressure vessel and the bottom head of the containment vessel,
wherein seismic forces that travel from the base support to the
reactor pressure vessel via the containment vessel are attenuated
by the attenuation device in a direction that is substantially
lateral to the vertical orientation of the containment vessel.
9. The system of claim 8, further comprising a support structure
located in an upper half of the containment vessel and configured
to support a majority of reactor pressure weight, wherein
substantially none of the reactor pressure weight is supported by
the attenuation device.
10. The system of claim 9 wherein the attenuation device comprises
a vertical post located along a longitudinal centerline of the
reactor pressure vessel, wherein the vertical post is inserted into
an adjacent vessel recess.
11. The system of claim 10, wherein the vertical post extends
downward from the bottom head of the reactor pressure vessel into
the adjacent vessel recess of the containment vessel.
12. The system of claim 10, wherein the vertical post extends
upward from the bottom head of the containment vessel into the
adjacent vessel recess of the reactor pressure vessel.
13. The system of claim 9, wherein the reactor pressure vessel and
the containment vessel are spaced apart from each other by an
annular containment volume, and wherein the attenuation device
comprises one or more bumpers located within the annular
containment volume.
14. The system of claim 9, wherein the reactor pressure vessel and
the containment vessel are spaced apart from each other by an
annular containment volume, and wherein the attenuation device
comprises: one or more radial posts projecting outwardly from the
reactor pressure vessel and located within the annular containment
volume; and one or more sets of brackets configured to restrain the
one or more radial posts in a circumferential direction.
15. An apparatus, comprising: means for transmitting a seismic
force to a containment vessel, wherein the containment vessel
houses a reactor pressure vessel that is spaced apart from the
containment vessel by an annular containment volume; means for
supporting a weight of the reactor pressure vessel within the
containment vessel, wherein the means for supporting passes through
the annular containment volume; and means for attenuating the
seismic force that is received by the reactor pressure vessel,
wherein the means for attenuating does not support the weight of
the reactor pressure vessel.
16. The apparatus of claim 15, wherein the means for attenuating
passes through the annular containment volume.
17. The apparatus of claim 15, wherein the means for attenuating is
located along a longitudinal centerline of the containment
vessel.
18. The apparatus of claim 15, wherein the means for attenuating
forms part of a seismic force attenuation path which transfers the
seismic force from the containment vessel to the reactor pressure
vessel.
19. The apparatus of claim 18, wherein the seismic force
attenuation path comprises a vertical portion that passes through
the means for transmitting, and wherein the means for attenuating
comprises means for attenuating the seismic force in a direction
that is substantially transverse to the vertical portion of the
seismic force attenuation path.
20. A method, comprising: supporting, with a support structure, a
weight of a reactor pressure vessel housed within a containment
vessel, wherein the reactor pressure vessel is spaced apart from
the containment vessel by an annular containment volume, and
wherein the support structure passes through the annular
containment volume; transmitting a seismic force through the
containment vessel; and attenuating, with an attenuation device
located along a longitudinal centerline of the reactor pressure
vessel, the seismic force that is received from the containment
vessel by the reactor pressure vessel, wherein the attenuation
device attenuates the seismic force in a direction transverse to
the longitudinal centerline, and wherein the attenuation device
does not support the weight of the reactor pressure vessel.
Description
STATEMENT OF RELATED MATTERS
[0001] This application claims priority to U.S. Provisional
Application No. 61/922,541 entitled MANAGING DYNAMIC FORCES ON A
NUCLEAR REACTOR SYSTEM and filed on Dec. 31, 2013, which is herein
incorporated by reference in its entirety.
TECHNICAL FIELD
[0003] This disclosure generally relates to systems, devices and
methods for attenuating dynamic forces and/or seismic forces on a
nuclear reactor system or other structure.
BACKGROUND
[0004] Seismic isolation may be utilized to control or reduce the
response of a component or structure to vertical and horizontal
ground-input motions or accelerations. Seismic isolation may
accomplish this by decoupling the motion of the component/structure
from the driving motion of the substructure. In some instances,
hardware (e.g., springs) may be positioned between the substructure
and superstructure. Use of such hardware may minimize the dynamic
response of the structure by increasing the fundamental period of
vibration for the component or structure, resulting in lower
in-structure accelerations and forces. To further reduce spectral
response amplitudes (e.g., deflections, forces, etc.), other
mechanisms may be employed that effectively reduce the peak
amplitude to manageable levels.
[0005] Piping and other connections may be provided between a
nuclear reactor and a secondary cooling system or other systems in
the power generation facility. In the event of an earthquake or
other seismic activity, significant forces or vibration may be
transferred to, or by, the connections, which can place great
stress on the connections. Forces resulting from thermal expansion
also place stress on the connections. Maintaining integrity of
these connections helps discourage the inadvertent release of
radioactive or other materials from the various systems, and
reduces maintenance or damage that might otherwise occur if one or
more of the connections fail.
[0006] During a seismic event, dynamic and/or seismic forces may be
transmitted from the ground, support surface, or surrounding
containment building to a reactor module. The seismic forces which
are transferred to the reactor module may experience a cumulative
increase and/or amplification in amplitude and/or frequency
depending on the number and/or length of intervening structures
and/or systems that the seismic forces travel in reaching the
reactor module. If the seismic forces become large enough, the
reactor core and/or fuel elements may be damaged.
[0007] The present invention addresses these and other
problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIGS. 1A-1B provide a side view and top view, respectively,
of a block diagram illustrating an example nuclear reactor system
that includes one or more seismic isolation assemblies.
[0009] FIGS. 2A-2B illustrate an example implementation of a
seismic isolation assembly.
[0010] FIGS. 3A-3B illustrate portions of example implementations
of a seismic isolation assembly.
[0011] FIG. 4 illustrates an example implementation of a seismic
isolation assembly.
[0012] FIG. 5 illustrates a force-deflection diagram for an example
implementation of a seismic isolation assembly.
[0013] FIG. 6 illustrates an example power module assembly
comprising a support structure.
[0014] FIG. 7 illustrates a side view of the power module assembly
of FIG. 6.
[0015] FIG. 8 illustrates a partial view of an example support
structure for a power module assembly comprising a seismically
isolated containment vessel.
[0016] FIG. 9 illustrates a partial view of an example support
structure for a seismically isolated containment vessel comprising
multiple elastic damping devices.
[0017] FIG. 10 illustrates a partial view of an example elastic
damping and retaining structure.
[0018] FIG. 11 illustrates a partial view of the elastic damping
and retaining structure of FIG. 10 responsive to a longitudinal
force.
[0019] FIG. 12 illustrates a partial view of the elastic damping
and retaining structure of FIG. 10 responsive to a transverse
force.
[0020] FIG. 13 illustrates a partial view of an example elastic
damping and retaining structure for a seismically isolated power
module.
[0021] FIG. 14 illustrates an example system for seismically
isolating a power module.
[0022] FIG. 15 illustrates an example reactor pressure vessel.
[0023] FIG. 16 illustrates a partial cut-away view of an example
reactor module comprising a containment vessel and a reactor
pressure vessel assembly.
[0024] FIG. 17 illustrates a cross-sectional view of an example
reactor module comprising a reactor pressure vessel and a
containment vessel.
[0025] FIG. 18 illustrates an example system comprising radial
keys.
[0026] FIG. 19 illustrates an example system comprising radial
bumpers.
[0027] FIG. 20 illustrates the example system of FIG. 19 together
with a reactor pressure vessel.
[0028] FIG. 21 illustrates an example system comprising a vertical
key.
[0029] FIG. 22 illustrates a further example system comprising a
vertical key.
[0030] FIG. 23 illustrates an example system comprising a vertical
key with an alternative force transmission path.
[0031] FIG. 24 illustrates a further example system comprising a
vertical key with an alternative force transmission path.
[0032] FIG. 25 illustrates an example system comprising an
integrated vertical key and lateral support.
[0033] FIG. 26 illustrates an example system comprising a conical
shaped key.
[0034] FIG. 27 illustrates an enlarged partial view of the example
system of FIG. 26 with the RPV undergoing thermal expansion.
[0035] FIG. 28 illustrates an enlarged partial view of the example
system of FIG. 26 in an expanded state.
[0036] FIG. 29 illustrates a further example system comprising a
conical shaped key.
[0037] FIG. 30 illustrates an example operation of the transmission
of dynamic or seismic force through a reactor module structure.
[0038] FIG. 31 illustrates an example system comprising a
stair-step shaped key.
[0039] FIG. 32 illustrates the example system of FIG. 31 in an
expanded state.
DETAILED DESCRIPTION
[0040] FIG. 1 is a block diagram illustrating a nuclear reactor
system 100 (e.g., a nuclear reactor) that includes one or more
seismic isolation assemblies 25. In some aspects, the nuclear
reactor system 100 is a commercial power pressurized water reactor
that utilizes natural circulation of a primary coolant to cool a
nuclear core and transfer heat from the core to a secondary coolant
through one or more heat exchangers. The secondary coolant (e.g.,
water), once heated (e.g., to steam, superheated steam or
otherwise), can drive power generation equipment, such as steam
turbines or otherwise, before being condensed and returned to the
one or more heat exchangers.
[0041] With respect to the nuclear reactor system 100, a reactor
core 20 is positioned at a bottom portion of a cylinder-shaped or
capsule-shaped reactor vessel 70. Reactor core 20 includes a
quantity of nuclear fuel assemblies, or rods (e.g., fissile
material that produces, in combination with control rods, a
controlled nuclear reaction), and optionally one or more control
rods (not shown). As noted above, in some implementations, nuclear
reactor system 100 is designed with passive operating systems
(e.g., without a circulation pump for the primary coolant)
employing the laws of physics to ensure that safe operation of the
nuclear reactor 100 is maintained during normal operation or even
in an emergency condition without operator intervention or
supervision, at least for some predefined period of time.
[0042] A cylinder-shaped or capsule-shaped containment vessel 10
surrounds reactor vessel 70 and may be partially or completely
submerged in a reactor pool, such as below waterline 90 (which may
be at or just below a top surface 35 of the bay 5), within reactor
bay 5. The volume between reactor vessel 70 and containment vessel
10 may be partially or completely evacuated to reduce heat transfer
from reactor vessel 70 to the reactor pool. However, in other
implementations, the volume between reactor vessel 70 and
containment vessel 10 may be at least partially filled with a gas
and/or a liquid that increases heat transfer between the reactor
and containment vessels.
[0043] In the illustrated implementation, reactor core 20 is
submerged within a liquid, such as water, which may include boron
or other additives, which rises into channel 30 after making
contact with a surface of the reactor core. The upward motion of
heated coolant is represented by arrows 40 (e.g., primary coolant
40) within channel 30 (e.g., riser 30). The coolant travels over
the top of heat exchangers 50 and 60 and is drawn downward by
density difference along the inner walls of reactor vessel 70 thus
allowing the coolant to impart heat to heat exchangers 50 and 60.
After reaching a bottom portion of the reactor vessel 70, contact
with reactor core 20 results in heating the coolant, which again
rises through channel 30. Although heat exchangers 50 and 60 are
shown as two distinct elements in FIG. 1, heat exchangers 50 and 60
may represent any number of helical (or other shape) coils that
wrap around at least a portion of channel 30.
[0044] Normal operation of the nuclear reactor module proceeds in a
manner wherein heated coolant rises through channel 30 and makes
contact with heat exchangers 50 and 60. After contacting heat
exchangers 50 and 60, the coolant sinks towards the bottom of
reactor vessel 70 in a manner that coolant within reactor vessel 70
remains at a pressure above atmospheric pressure, thus allowing the
coolant to maintain a high temperature without vaporizing (e.g.,
boiling).
[0045] As coolant within heat exchangers 50 and 60 increases in
temperature, the coolant may begin to boil. As the coolant within
heat exchangers 50 and 60 begins to boil, vaporized coolant, such
as steam, may be used to drive one or more turbines that convert
the thermal potential energy of steam into electrical energy. After
condensing, coolant is returned to locations near the base of heat
exchangers 50 and 60.
[0046] In the illustrated implementation, a downcomer region
between the reflector 15 and the reactor vessel 70 provides a fluid
path for the primary coolant 40 flowing in an annulus between the
riser 30 and the reactor vessel 70 from a top end of the vessel 70
(e.g., after passing over the heat exchangers 50, 60) and a bottom
end of the vessel 70 (e.g., below the core 20). The fluid path
channels primary coolant 40 that has yet to be recirculated through
the core 20 into convective contact with at least one surface of
the reflector 15 in order to cool the reflector 15.
[0047] As illustrated, the containment vessel 10 may be coupled to
the reactor bay 10 through one or more seismic isolation assemblies
25. As shown in FIG. 1B, each seismic isolation assembly 25 may be
mounted in or on an embedment 29 that extends from an interior
surface 27 of the reactor bay 5. Although four seismic isolation
assemblies 25 are shown in FIG. 1B (one per wall of the interior
surface 27 of the bay 5), there may be more or fewer seismic
isolation assemblies 25 to support the containment vessel 10, as
necessary. The containment vessel 10, in this implementation,
includes support lugs 33 that rest on the embedments 29 adjacent
the seismic isolation assemblies 25.
[0048] In some implementations, the seismic isolation assemblies
25, embedments 29, and support lugs 33 may be positioned at or near
an axis through the containment vessel 10 that intersects an
approximate center of gravity (CG), or slightly above the CG, of
the vessel 10. The containment vessel 10 (and components therein)
may be supported by the seismic isolation assemblies 25, embedments
29, and support lugs 33 in combination with a buoyancy force of the
pool of liquid 90 acting on the containment vessel 10.
[0049] Generally, the illustrated seismic isolation assemblies 25
(shown in more detail in FIGS. 2A-2B and 3A-3B) may include one or
more components that experience plastic deformation in response to
a seismic event (or other motion-causing event) that results in a
force on the containment vessel 10. For example, in the case of a
seismic event, seismic energy may be dissipated through one or more
portions of the assemblies 25 (e.g., a series of conical, or other
shapes bounded by convex surfaces, elements) by penetrating and
contracting such portions to plastically deform the one or more
portions of assemblies 25. Energy may be absorbed by plastic
deformation and friction between moving elements of the assemblies
25.
[0050] In some implementations, stiffness of the assembly 25 may be
controlled by sizing the plastically deformable elements. For
example, a multiple of cones, dies, and cylinders (as the
plastically deformable elements) can be arranged in an enclosure as
shown in more detail in FIGS. 3A-3B. The enclosure of the assembly
25 may move relative to the support lugs 29 (or other reactor bay
embedment). In the case of a seismic event such as an earthquake,
the seismic isolation assemblies 25 may contribute to a safe shut
down of the nuclear reactor system 100, while maintaining coolable
geometry. In some implementations, the seismic isolation assemblies
25 may be sized for a sliding force above forces associated with an
operating basis earthquake (OBE). An OBE may be typically one third
to one half of forces associated with a safe shutdown earthquake
(SSE). The SSE event is classified as a faulted condition, service
Level D. The OBE event is classified as an Upset condition, service
Level B.
[0051] When the reactor system 100 is subject to an earthquake
below the intensity of an OBE, operations may resume shortly after
the event without any major repairs or inspections. As a result,
during an OBE, the seismic isolation assemblies 25 may not undergo
any plastic deformation. For instance, if the seismic isolation
assemblies 25 may remain linear (e.g., experience no or negligible
plastic deformation) during an OBE, replacement of the isolation
assemblies 25 may not be necessary. When the reactor system 100 is
subject to an SSE, the isolation assemblies 25 may be plastically
exercised and may be removed and/or replaced. Replacement of the
seismic isolation assemblies 25, may be much less costly, however,
than replacement of other components (e.g., of the reactor system
100).
[0052] FIGS. 2A-2B illustrate an example implementation of a
seismic isolation assembly 200. In some aspects, the seismic
isolation assembly 200 may be used as the seismic isolation
assembly 25 shown in FIGS. 1A-1B. FIG. 2A shows an isometric view
of several seismic isolation assemblies 200 mounted in an embedment
29, while FIG. 2B shows a top view of the seism isolation
assemblies 200 mounted in the embedment 29, with several internal
components exposed for detail.
[0053] As shown in FIG. 2A, several (e.g., three) seismic isolation
assemblies 200 may be mounted against vertical surfaces of the
embedment 29, thereby defining a pocket (e.g., for receiving a
support lug of the containment vessel 10). Each seismic isolation
assembly 200 may affixed to one of the vertical surfaces or may
simply rest in the embedment 29 in contact with the vertical
surface. In this example implementation, an enclosure 205 of the
seismic isolation assembly 200 includes a rectangular cuboid
portion that has a tapered, or ramped, top portion. Other shapes
are contemplated by the present disclosure however. In some
aspects, one or more plastically deformable elements may be mounted
and/or contained, at least partially, within the cuboid portion
201.
[0054] FIG. 2B illustrates one or more internal components of each
seismic isolation assembly 200. As shown, each seismic isolation
assembly 200 may include a conical stretching element 210, a
contracting die 215, and a cylindrical plasticity element 220. In
some aspects, as illustrated in FIG. 2B, there may be several
(e.g., between two and five) sets of the conical stretching element
210, contracting die 215, and cylindrical plasticity element 220.
Other numbers of sets are also contemplated by the present
disclosure and may depend, at least in part, on a size (e.g.,
dimension in the x or z direction shown in FIG. 2A) of the
particular seismic isolation assembly 200.
[0055] In the illustrated implementation, a portion of the
cylindrical plasticity element 220 may extend from the enclosure
205 and attach (e.g., rigidly or semi-rigidly, for example, by
welding) to the embedment 29 (and by extension to the reactor bay
5). Thus, in some aspects, dynamic forces (e.g., seismic forces)
that transmit through the reactor bay 5 may be borne by the seismic
isolation assembly 200, through the cylindrical plasticity element
220.
[0056] In some aspects, an overall stiffness of each seismic
isolation assembly 200 may be based, at least in part on the number
of sets of the conical stretching element 210, contracting die 215,
and cylindrical plasticity element 220, as well as the relative
size of one or more of the conical stretching element 210,
contracting die 215, and cylindrical plasticity element 220 within
the enclosure 205. For example, turning briefly to FIG. 4, an
example idealized representation 400 of the example implementation
of the seismic isolation assembly 200.
[0057] As shown in FIG. 4, a spring-slider and damper are
positioned in parallel. Representation 400 includes an "I" node
that represents a reactor building wall embedment (e.g., the
embedment 29) and a "J" node that represents the enclosure 205 of
the seismic isolation assembly 200. The stiffness of the plasticity
elements (e.g., the conical stretching element 210, contracting die
215, and cylindrical plasticity element 220) is represented by K1
(shown as a resistance element).
[0058] In some aspects, other "resistant" elements may also be
accounted for, as shown in FIG. 4. For example, a hydraulic damping
feature is represented by the damping coefficient, C. Additional
stiffness elements (e.g., springs, Belleville washers, or
otherwise) may also be used in the nuclear reactor system 100
(e.g., mounted within the enclosures 205 or mounted between the
enclosures 205 and the embedments 29) to dissipate seismic forces
(e.g., in parallel with the seismic isolation assembly 200) and are
generally represented by K2.
[0059] A gap is also shown that represents a space (e.g., filled
with a gas or fluid) between the seismic isolation assembly 200 and
the embedment 29 (e.g., between nodes J and I). The FSLIDE value,
as shown, represents an absolute value of a spring force that must
be exceeded before sliding occurs. This sliding force may result
from plastic deformation (e.g., of one or more of the conical
stretching element 210, contracting die 215, and cylindrical
plasticity element 220) and friction forces.
[0060] In some aspects, K1 may be chosen, and in some cases chosen
in parallel with K2 and/or C, to attain a particular FSLIDE. The
particular FSLIDE may be large enough so that seismic forces acting
at node I from an event (e.g., an OBE or SSE event, or other event)
do not exceed FSLIDE and, therefore, are completely or mostly borne
by the elastic deformation that occurs in K1 (as well as, in some
examples, spring and dampening of K2 and C, respectively).
[0061] Turning briefly to FIG. 5, a force-deflection diagram 500
illustrates the relationship (without effects of K2 and C) between
seismic force on the seismic isolation assembly 200 and deflection.
As illustrated, below the FSLIDE force, the system is linear
(assuming that there is no gap between the seismic isolation
assembly 200 and the embedment 29). When sliding occurs, the
absorbed energy is proportional to the sliding force times the
sliding distance.
[0062] In this illustration, the K1 and K2 springs are shown as
linear (proportional) springs, but it can be generalized to any
type of non-linear (inelastic, non-proportional) spring. For
example, in other representations, the number of
spring-damper-slider elements can be in any number and
combination.
[0063] Returning to FIG. 2A, the illustrated seismic isolation
assemblies 200 are attached to the embedment 29 through the
cylindrical plasticity elements 220. As illustrated, there may be
multiple sets of the conical stretching element 210, contracting
die 215, and cylindrical plasticity element 220 arranged vertically
within the enclosures 205. Contact between the embedment 29 and the
cylindrical plasticity elements 220 may drive the relative movement
of the enclosures 205 with respect to the bay 5 (and thus any
structure that contains and is in contact with the bay 5).
[0064] The number of plasticity mechanisms inside each enclosure
205 (e.g., sets of the conical stretching element 210, contracting
die 215, and cylindrical plasticity element 220) may be a function
of an amount of dissipative energy needed to achieve adequate
damping of the structure (e.g., the bay 5 or other structure)
during a seismic event. The size of the enclosure 205 may be
determined by an allowable relative displacement of the nuclear
reactor system 100 with respect to the structure (e.g., about 4
inches as a maximum allowable displacement). The size of each
isolation assembly 200 can be rather compact.
[0065] In some aspects, the conical stretching elements 210 and the
cylindrical plasticity elements 220 may work together to dissipate
forces in the X and Z directions as shown in FIG. 2A. For example,
the conical stretching elements 210 may dissipate energy by
plastically deforming the cylindrical plasticity elements 220
(e.g., by moving into the elements 210 toward the embedment 29) in
response to forces in the X and Z directions. In some aspects, the
contracting dies 215 may move with the movement of the conical
stretching elements 210. In other aspects, the contracting dies 215
may simply be bores in the enclosures 205 through which the
cylindrical plasticity elements 220 extend to contact the embedment
29, rather than separate components.
[0066] Based on a sufficient seismic force, movement of the conical
stretching elements 210 into the cylindrical plasticity elements
220 (e.g., into the bores 230 as shown in FIG. 3A) may result in
semi-permanent or permanent plastic deformation of the cylindrical
plasticity elements 220. Further, during (and after) plastic
deformation of the cylindrical plasticity elements 220, seismic
forces may also be dissipated through friction, and associated
heat, between the conical stretching elements 210 and the
cylindrical plasticity elements 220.
[0067] FIGS. 3A-3B illustrate portions of example implementations
of the seismic isolation assembly 200. FIG. 3A shows a close-up
view of the plastically deformable elements mounted in the
enclosure 205. As further shown in FIG. 3A, portions of the
enclosure 205 and the plastically deformable elements may be
surrounded by the pool of liquid 90 (e.g., water or other fluid).
As described above, the liquid 90 may be a hydraulic damping
feature (e.g., represented by the damping coefficient, C, in FIG.
4) that helps dissipate seismic forces, as well as heat generated
by frictional forces of the plastically deformable elements as they
slide/deform in response to the seismic forces.
[0068] In some aspects, a bore 230 of the cylindrical plasticity
element 220 may enclose a working fluid (e.g., a gas such as air,
or a liquid such as water). The working fluid may provide further
dissipative affects for any seismic forces received by the seismic
isolation assembly 200. For example, the working fluid may
dissipate some of the energy of the seismic event by compressing
within the bore 230 as the conical stretching element 210 is forced
into the bore 230 of the cylindrical plasticity element 220.
[0069] Turning to FIG. 3B, another implementation is shown that
includes a fluid orifice 225 that fluidly connects the bore 230 and
the reactor pool 90. In this aspect, the working fluid may be a
portion of the pool 90. The working fluid, in both implementations
shown in FIGS. 3A-3B, may provide further hydraulic damping to
dissipate the seismic forces and movement due to such forces. For
example, expelling the working fluid from the bore 230 during
movement of the conical stretching element 210 into the bore 230 of
the cylindrical plasticity element 220 may further dissipate
seismic energy through hydraulic damping.
[0070] A number of implementations related to FIGS. 1-5 have been
described. Nevertheless, it will be understood that various
modifications may be made. For example, the steps of the disclosed
techniques may be performed in a different sequence, components in
the disclosed systems may be combined in a different manner, and/or
the components may be replaced or supplemented by other components.
Accordingly, other implementations are within the scope of the
following examples.
[0071] A nuclear reactor seismic isolation assembly may include one
or more deformable elements that, in response to energy generated
by a seismic event and transmitted to the assembly through a
structure that houses a nuclear reactor containment vessel,
plastically deform to at least partially dissipate the seismic
energy. In some aspects, portions of the energy are dissipated
through the plastic deformation while other portions of the energy
are dissipated through friction between two or more components of
the assembly. In still other aspects, a working fluid may be
compressed within the assembly to dissipate some of the seismic
energy.
[0072] A nuclear reactor system may include one or more seismic
isolation assemblies according to the present disclosure may limit
a reaction force (or forces) on a structure (e.g., a containment
pool structure or building structure) to a sliding force. The
disclosed seismic isolation assemblies may be geographically
neutral and thus be used world-wide in nuclear reactor systems. As
another example, the seismic isolation assemblies may be passive
isolators rather than active isolators, thereby reducing
maintenance and inspection complexities (e.g., by limiting to
visual inspection or otherwise). As another example, the disclosed
seismic isolation assemblies may accommodate or promote a modular
building design for nuclear reactor system structures.
[0073] A nuclear reactor seismic isolation assembly may comprise an
enclosure that defines a volume and a plastically-deformable member
mounted, at least in part, within the volume. A stretching member
may be moveable within the enclosure to plastically-deform the
plastically deformable member in response to a dynamic force
exerted on the enclosure. The enclosure may be attachable to a
portion of a nuclear reactor containment vessel. The dynamic force
may comprise a seismically generated force.
[0074] In some examples, the plastically deformable member may
comprise a first portion mounted within the enclosure and a second
portion that extends through a die member to an exterior of the
enclosure. The second portion may comprise a weldable portion.
Additionally, the die member may be moveable with the stretching
member in response to the dynamic force exerted on the
enclosure.
[0075] The stretching member may be mounted within a portion of a
bore that extends through the plastically-deformable member. The
portion of the bore may comprise a first diameter approximately
equal to an outer dimension of the stretching member, the bore
comprising another portion that comprises a second diameter smaller
than the first diameter. Additionally, the second diameter may be
stretched to approximately equal the first diameter based on
movement of the stretching element through the bore in response to
the dynamic force exerted on the enclosure.
[0076] In some examples, the bore may at least partially enclose a
working fluid that dissipates at least a portion of energy
generated by the dynamic force exerted on the enclosure based on
movement of the stretching element through the bore in response to
the dynamic force exerted on the enclosure. The working fluid may
comprise a portion of a fluid enclosed in a nuclear reactor
bay.
[0077] A method for managing dynamic forces and/or for attenuating
seismic forces may comprise receiving a force on a seismic
isolation assembly in contact with a nuclear reactor pressure
vessel, wherein the force may be generated at least in part by a
seismic event. The received force may be transmitted through an
enclosure of the seismic isolation assembly to a stretching member,
and the stretching member may be moved within the enclosure based
on the received force.
[0078] The method may further comprise plastically deforming a
deformable member, that is at least partially enclosed in the
enclosure, with the stretching member, and dissipating at least a
portion of the received force based on plastically deforming the
deformable member.
[0079] Additionally, the method may comprise generating friction
between the deformable member and the stretching member based on
repeated movement of the stretching member into the deformable
member based on the received force, and dissipating another portion
of the received force based on the generated friction.
[0080] In some examples, a working fluid enclosed in a chamber of
the deformable element may be compressed based on movement of the
stretching member into the deformable member based on the received
force, and another portion of the received force may be dissipated
based on the compression of the working fluid. The working fluid
may be expelled to a reactor bay that encloses a liquid, through a
fluid passageway that fluidly couples the chamber and the reactor
bay. Additionally, another portion of the received force may be
dissipated through the liquid enclosed in the reactor bay.
[0081] One or more spring members may be compressed based on
movement of the stretching member into the deformable member based
on the received force, and another portion of the received force
may be dissipated based on the compression of the one or more
spring members. In some examples, the received force may be
transmitted through the deformable member that is in contact with a
structure that houses the nuclear reactor pressure vessel.
[0082] A nuclear reactor system may comprise a reactor bay that
encloses a liquid and a nuclear reactor containment vessel that is
mounted within the reactor bay with lugs positioned in embedments
of the reactor bay. Additionally, the system may comprise seismic
isolation assemblies mounted in the embedments and between the lugs
and walls of the embedments. Each of the seismic isolation
assemblies may comprise an enclosure that defines a volume, a
plastically-deformable member mounted, at least in part, within the
volume, and a stretching member moveable within the enclosure to
plastically-deform the plastically-deformable member in response to
a dynamic force exerted on the reactor bay.
[0083] The plastically-deformable member may comprise a first
portion mounted within the enclosure and a second portion that
extends through a die member to a wall of one of the embedments.
The second portion may be anchored to the wall. In some examples,
the die member may be moveable with the stretching member in
response to the dynamic force exerted on the reactor bay.
[0084] Additionally, the stretching member may be mounted within a
portion of a bore that extends through the plastically deformable
member. The portion of the bore may comprise a first diameter
approximately equal to an outer dimension of the stretching member,
and another portion that comprises a second diameter smaller than
the first diameter. In some examples, the second diameter may be
stretched to approximately equal the first diameter based on
movement of the stretching element through the bore in response to
the dynamic force exerted on the reactor bay.
[0085] The bore may at least partially enclose a working fluid that
dissipates at least a portion of energy generated by the dynamic
force exerted on the enclosure based on movement of the stretching
element through the bore in response to the dynamic force exerted
on the reactor bay. The nuclear reactor system may further comprise
a passage that fluidly couples the bore to a volume defined by the
reactor bay. The working fluid may comprise a portion of a fluid
enclosed in the volume.
[0086] FIG. 6 illustrates an example power module assembly
comprising a containment vessel 624, reactor vessel 622 and a
support structure 620. The containment vessel 624 may be
cylindrical in shape, and may have ellipsoidal, domed or
hemispherical upper and lower ends 626, 628. The entire power
module assembly 625 may be submerged in a pool of liquid 636 (for
example, water) which serves as an effective heat sink. In other
examples, the power module assembly 625 may be partially submerged
in the pool of liquid 636. The pool of liquid 636 is retained in
reactor bay 627. The reactor bay 627 may be comprised of reinforced
concrete or other conventional materials. The pool of liquid 636
and the containment vessel 624 may further be located below ground
609. In some examples, the upper end 626 of the containment vessel
624 may be located completely below the surface of the pool of
liquid 636. The containment vessel 624 may be welded or otherwise
sealed to the environment, such that liquids and gas do not escape
from, or enter, the power module assembly 625.
[0087] The containment vessel 624 is shown suspended in the pool of
liquid 636 by one or more support structures 620, above a lower
surface of the reactor bay 627. The containment vessel 624 may be
made of stainless steel or carbon steel, and may include cladding.
The power module assembly 625 may be sized so that it can be
transported on a rail car. For example, the containment vessel 624
may be constructed to be approximately 4.3 meters in diameter and
17.7 meters in height (length). Refueling of a reactor core may be
performed by transporting the entire power module assembly 625 by
rail car or overseas, for example, and replacing it with a new or
refurbished power module assembly which has a fresh supply of fuel
rods.
[0088] The containment vessel 624 encapsulates and, in some
conditions, cools the reactor core. The containment vessel 624 is
relatively small, has a high strength and may be capable of
withstanding six or seven times the pressure of conventional
containment designs in part due to its smaller overall volume.
Given a break in the primary cooling system of the power module
assembly 625 no fission products are released into the
environment.
[0089] The power module assembly 625 and containment vessel 624 are
illustrated as being completely submerged in the pool of liquid
636. All sides, including the top and bottom, of the containment
vessel 624 are shown as being in contact with, and surrounded by,
the liquid 636. However in some examples, only a portion of
containment vessel 624 may be submerged in the pool of liquid 636.
The one or more support structures 620 are located at an
approximate midpoint of the containment vessel 624. In some
examples, the one or more support structures 620 are located at an
approximate center of gravity (CG), or slightly above the CG, of
the power module 625. The power module 625 is supported by the
support structure 620 in combination with a buoyancy force of the
pool of liquid 636 acting on the containment vessel 624. In some
examples, the power module assembly 625 is supported by two support
structures 620. The first support structure may be located on a
side of the power module assembly 625 opposite the second support
structure.
[0090] The one or more support structures 620 may be configured to
support both the containment vessel 624 and the reactor vessel 622.
In s, the one or more support structures 620 are located at an
approximate CG, or slightly above the CG, of the reactor vessel
622.
[0091] FIG. 7 illustrates a side view of the power module assembly
625 of FIG. 6. The containment vessel 624 as well as the reactor
vessel 622, may be configured to pivot about the support structure
620, due to a rotational force RF acting on the power module 625.
In some examples, the support structure 620 is located slightly
above the CG of the power module 625, so that the lower end 628
tends to return to a bottom facing position within the reactor bay
627 due to gravity after the rotational force RF has subsided. The
rotation of the containment vessel 624 also allows for greater
maneuverability during installation or removal of the power module
assembly 625 from the reactor bay 627. In some examples, the
containment vessel 624 may be rotated between a vertical and a
horizontal orientation or position of the power module assembly
625.
[0092] The power module 625 is further illustrated as comprising a
base support, such as a base skirt 730, located at the lower end
628 of the containment vessel 624. The base skirt 730 may be
rigidly mounted to, welded on, and/or form an integral part of, the
containment vessel 624. In some examples, the base skirt 730 may be
designed to support the weight of the power module 625 if the base
skirt 730 is placed on the ground, on a transport device, or in a
refueling station, for example. During normal operation (e.g. power
operation) of the power module 625, the base skirt 730 may be
suspended off the ground or positioned above the bottom of the
reactor bay 627, such that the base skirt 730 is not in contact
with any exterior component or surface.
[0093] When the power module 625 rotates about the support
structure 620, the lower end 628 of the containment vessel 625
tends to move in a lateral or transverse direction Lo. The base
skirt 730 may be configured to contact an alignment device 375
located in the pool of liquid 636 when the containment vessel 624
pivots a predetermined amount about the support structure 620. For
example, the alignment device 735 may be sized so that the power
module 625 is free to rotate within a range of motion or particular
angle of rotation.
[0094] The alignment device 735 may comprise an exterior diameter
that is smaller than an interior diameter of the base skirt 730.
The alignment device 735 may be sized to fit within the base skirt
730, such that the base skirt 730 does not contact the alignment
device 735 when the power module 625 is at rest. In some examples,
the base skirt 730 may be configured to contact the alignment
device 735 when the containment vessel 624 pivots about the support
structure 620. The base skirt 730 may not inhibit a vertical range
of motion of the containment vessel 623, in the event that a
vertical force acts upon the power module 625. The alignment device
735 may be rigidly mounted (e.g. bolted, welded or otherwise
attached) to the bottom of the reactor bay 627. In some examples,
one or more dampeners 638 are located between the base skirt 730
and the alignment device 735 to attenuate a contact force between
the base skirt 730 and the alignment device 735 when the power
module 625 pivots or rotates. The one or more dampeners 738 may be
mounted to or otherwise attached to either the alignment device 735
(as illustrated) or the base skirt 730.
[0095] FIG. 8 illustrates a partial view of an example support
structure 840 for a power module assembly comprising a seismically
isolated containment vessel 824. The support structure 840
comprises a support arm 845 and a mounting structure 847. The
support arm 845 may be located at an approximate midpoint of the
containment vessel 824. The mounting structure 847 may be submerged
in liquid (for example water). Additionally, the mounting structure
847 may be an extension of, mounted to, recessed in, or integral
with, the wall of the reactor bay 627 (FIG. 6).
[0096] A damping device 846 may be disposed between the support arm
845 and the mounting structure 847. At least a portion of the
weight of the containment vessel 824 may be transferred to the
support structure 847 through the damping device 846. Damping
device 846 may be elastic, resilient or deformable, and may
comprise a spring, pneumatic or hydraulic shock absorber, or other
vibration or force attenuating device known in the art. In some
examples, the damping device 846 comprises natural or synthetic
rubber. The damping device 846 may comprise an elastic material
that is manufactured from petroleum or other chemical compounds and
that is resistant to material breakdown when exposed to radiation
or humidity. In yet another example, the damping device 846
comprises soft deformable metal or corrugated metal.
[0097] The damping device 846 may be configured to attenuate
dynamic or seismic forces transferred by and between the support
arm 845 and the mounting structure 847. For example, a vertical or
longitudinal force FV, acting along a longitudinal or lengthwise
direction of the containment vessel 824, may act through the
damping device 846. Additionally, a horizontal or transverse force
FH may be exerted on the damping device 846 in any direction
perpendicular to the longitudinal force FV. Transverse force FH may
be understood to include a direction vector located in the plane
defined by the X and Z coordinates of illustrative coordinate
system 48, whereas the longitudinal force FV may be understood to
include a direction vector oriented in the Y coordinate, the Y
coordinate being perpendicular to the X-Z plane of the illustrative
coordinate system 848.
[0098] In some examples, by placing the support arm 845 at an
approximate center of gravity of the containment vessel 824, a
transverse force FH acting on the power module 625 tends to cause
the containment vessel 824 to slide rather than rotate. Locating
the support arm 845 on the containment vessel 824 at a particular
height or position provides for controllability for how the
containment vessel 824 will behave when it is subjected to one or
more forces FH, FV, or RF.
[0099] The damping device 846 may compress in a vertical direction
to absorb or attenuate the longitudinal force FV. In some examples,
the damping device 846 may be configured to compress or flex in a
horizontal direction to attenuate the transverse force FH.
Additionally, the damping device 846 may be configured to slide
along the mounting structure 847 within the X-Z plane during a
seismic activity, such as an earthquake or explosion. Forces FV and
FH may also be understood to result from thermal expansion of one
or more components of the power module 625, including containment
vessel 824, in any or all of the three dimensions X, Y, Z.
[0100] As a result of the compression or movement of the damping
device 846, less of the forces FV and FH are transferred from the
mounting structure 847 to the containment vessel 824, or from the
containment vessel 824 to the mounting structure 847. The
containment vessel 824 experiences less severe shock than what
might otherwise be transferred if the support arm 845 were rigidly
mounted to, or in direct contact with, the mounting structure 847.
The containment vessel 824 may be configured to rotate about the
horizontal axis X, due to a rotational force RF acting on the power
module 625 (FIG. 7).
[0101] Support arm 845 may be rigidly attached to the containment
vessel 824. The one or more elastic damping devices 846 may be
located between, and in contact with, both the support arm 845 and
the mounting structure 847 located in the liquid 636 (FIG. 6). The
elastic damping device 846 may provide a pivot point between the
support arm 845 and the support structure 847, wherein the
containment vessel 24 pivots or rotates about the elastic damping
device 846, similar to that illustrated by FIG. 7. The weight of
the containment vessel 824 may be supported, in part, by a buoyancy
force of the liquid 636. The surrounding liquid 636 (FIG. 6) also
serves to attenuate any of the transverse force FH, longitudinal
force FV, and rotational force RF acting on the containment vessel
824.
[0102] In some examples, the support arm 845 comprises a hollow
shaft 829. The hollow shaft 829 may be configured to provide a
through-passage for an auxiliary or secondary cooling system. For
example, piping may exit the containment vessel 824 via the hollow
shaft 829.
[0103] FIG. 9 illustrates a partial view of a support structure 950
for a seismically isolated containment vessel 924 comprising a
support arm 955 and multiple elastic damping devices 952, 954. The
first elastic damping device 952 may be located between the support
arm 955 and a lower mounting structure 957. The second elastic
damping device 954 may be located between the support arm 955 and
an upper mounting structure 958. In some examples, the first and
second elastic damping devices 952, 954 are mounted to or otherwise
attached to the support arm 955. In other examples, one or both of
the first and second elastic damping devices 952, 954 are mounted
to the lower and upper mounting structures 957, 958,
respectively.
[0104] At least a portion of the weight of the containment vessel
924 may be transferred to the lower support structure 957 through
the first elastic damping device 952. The first elastic damping
device 952 may be under compression when the containment vessel 924
is at rest. The first elastic damping device 952 may be understood
to attenuate longitudinal force acting between the support arm 955
and the lower mounting structure 957. The second elastic damping
device 952 may also be understood to attenuate longitudinal force
acting between the support arm 955 and the upper mounting structure
958. A longitudinal or vertical movement of the containment vessel
924 may be constrained by the lower and upper mounting structures
957, 958 as they come into contact with, or cause a compression of,
the first and second elastic damping devices 952, 954,
respectively. First and second elastic damping devices 952, 954 may
provide similar functionality as a snubber or pair of snubbers in a
conventional shock absorber.
[0105] In some examples, the lower mounting structure 957 comprises
a recess 956. The recess 956 may be sized such that it has an
interior dimension or diameter that is larger than an exterior
dimension or diameter of the first elastic damping device 952. The
first elastic damping device 952 is illustrated as being seated or
located in the recess 956. The recess 956 may operate to constrain
a movement of the containment vessel 924 in one or more lateral or
transverse directions. The first elastic damping device 952 may be
configured to compress or flex when it presses up against a wall of
the recess 956. In some examples, the recess 956 may restrict an
amount or distance that the first elastic damping device 952 is
allowed to slide on the lower mounting structure 957 when the
containment vessel 924 experiences lateral or transverse force.
[0106] FIG. 10 illustrates a partial view of an elastic damping and
retaining structure 1060 for a seismically isolated containment
vessel 1024. The damping and retaining structure 1060 comprises a
deformable portion 1066. The deformable portion 1066 may be dome
shaped, elliptical or hemispherical in shape. Mounting structure
1067 may comprise a recess 1068, and the deformable portion 1066
may be seated or located in the recess 1068. The deformable portion
1066 and recess 1068 may be understood to function similarly as a
ball joint, wherein the deformable portion 1066 rotates or pivots
within the recess 1068.
[0107] The recess 1068 is illustrated as being concave in shape.
The mounting structure 1067 may be configured to constrain a
movement of the containment vessel 1024 as a result of transverse
force FH being applied in a lateral plane identified as the X-Z
plane in the illustrative coordinate system 1048. Additionally, the
mounting structure 1067 may be configured to constrain a
longitudinal movement of the containment vessel 1024 as a result of
a longitudinal force FV being applied in a direction Y
perpendicular to the X-Z plane. The containment vessel 1024 may be
configured to rotate about the horizontal axis X, due to a
rotational force RF acting on the power module 625 (FIG. 7). In
some examples, the recess 1068 forms a hemispherical, domed or
elliptical bowl. A base support, such as base skirt 630 (FIG. 6),
located at the bottom end of the containment vessel 1024 may be
configured to constrains a rotation of the containment vessel 1024
as the deformable portion 1066 pivots or rotates in the recess
1068.
[0108] The mounting structure 1067 may be configured to support
some or all of the weight of the power module. In some examples, a
buoyancy force of the liquid 636 supports substantially all of the
weight of the power module, such that the recess 1068 of the
mounting structure 1067 may primarily operate to center or maintain
a desired position of the power module.
[0109] FIG. 11 illustrates a partial view of the elastic damping
and retaining structure 1060 of FIG. 10 responsive to a
longitudinal force FV. The recess 1068 in the mounting structure
1067 may comprise a radius of curvature R2 that is greater than a
radius of curvature R1 of the deformable portion 1066 of the
damping and retaining structure 1060 when the containment vessel
1024 is at rest. Longitudinal force FV may be applied to support
arm 1065 (FIG. 10) as a result of vertical movement of the
containment vessel 1024, or as a result of force transmitted from
the mounting structure 1067 to the containment vessel 1024. The
longitudinal force may result from an earthquake or explosion for
example.
[0110] When a dynamic longitudinal force FV is applied to the
support arm 1065, the damping device may be configured to compress
from a static condition illustrated in solid lines by reference
number 1066, to a dynamic condition illustrated in dashed lines by
reference number 1066A. The radius of curvature of the deformable
portion 1066 temporarily approximates the radius of curvature R2 of
the recess 1068 in the dynamic condition 1066A. As the effective
radius of the deformable portion 1066 increases, this results in an
increased contact surface to form between the deformable portion
1066 and the recess 1068. As the contact surface increases, this
acts to resist or decrease additional compression of the deformable
hemispherical portion 1066, and attenuates the longitudinal force
FV. In some examples, the effective radius of curvature of the
deformable hemispherical portion 1066 increases with an increase in
longitudinal force FV. When the dynamic longitudinal force FV has
attenuated, the deformable portion 1066 may be configured to retain
its original radius of curvature R1.
[0111] FIG. 12 illustrates a partial view of the elastic damping
and retaining structure 1060 of FIG. 10 responsive to a transverse
force FH. The recess 1068 may be configured to constrain a movement
of the deformable portion 1066 in at least two degrees of freedom.
For example, the movement of the deformable portion 1066 may be
constrained in the X and Z directions of the illustrative
coordinate system 1048 of FIG. 10. The deformable portion 1066 may
be configured to compress or flex when it presses up against a wall
of the recess 1068. The compression or deformation of the
deformable portion 1066 attenuates the horizontal force FH. In some
examples, the recess 1068 may restrict an amount or distance that
the deformable portion 1066 is allowed to slide on the mounting
structure 1067 when the containment vessel 1024 experiences
transverse force FH. When a transverse force FH is applied to the
support arm 1065, the damping device moves or slides from the
static condition illustrated in solid lines by reference number
1066, to the dynamic condition illustrated in dashed lines by
reference number 1066B.
[0112] Whereas the recess 956, 1068 are illustrated in FIGS. 9 and
10 as being formed in the mounting structure 957, 1067, other
examples may include where the recess 956, 1068 is formed in the
support arm 955, 1065, and wherein the damping device 952, 1066 is
mounted to the mounting structure 957, 1067. These alternate
examples may otherwise operate similarly as the examples
illustrated in FIG. 9 or 10, to constrain movement of the
containment vessel 924, 1024 in one or both of the transverse and
longitudinal directions.
[0113] FIG. 13 illustrates a partial view of an elastic damping and
retaining structure 1370 for a seismically isolated power module
1380. The power module 1380 comprises a reactor vessel 1322 and a
containment vessel 1324. The elastic damping and retaining
structure 1370 comprises one or more support arms, or trunnions,
and one or more mounting structures. A first trunnion 1375,
protrudes or extends from the reactor vessel 1322. The reactor
vessel trunnion 1375 provides similar functionality as one or more
of the support arms described above with respect to FIGS. 6-10. A
second trunnion 1385 protrudes or extends from the containment
vessel 1324. The reactor vessel trunnion 1375 lies along the same,
single axis of rotation as the containment vessel trunnion 1385.
The axis of rotation X is shown in illustrative coordinate system
1348. One or both of the reactor vessel 1322 and containment vessel
1324 may rotate about the axis of rotation X when a rotational
force RF acts on the power module 1325. The reactor vessel 1322 and
containment vessel 1324 may rotate in the same or in opposite
rotational directions from each other.
[0114] Reactor vessel trunnion 1375 is shown supported on a first
mounting structure 1377. The mounting structure 1377 protrudes or
extends from the containment vessel 1324. The reactor vessel
trunnion 1375 may be configured to move or slide along the mounting
structure 1377 when horizontal force FH1 or FH2 acts on the power
module 1380. A first damping element 1376 may be configured to
attenuate or reduce the impact of horizontal force FH2 transmitted
by or between the reactor vessel 1322 and containment vessel 1324.
The first damping element 1376 also helps to center or maintain a
respective position or distance between the reactor vessel 1322 and
containment vessel 1324 when the power module 1380 is at rest or in
a static condition.
[0115] Containment vessel trunnion 1385 is shown supported on a
second mounting structure 1387. In some examples, the mounting
structure 1387 protrudes or extends from a reactor bay wall 1327.
The containment vessel trunnion 1385 may move or slide along the
mounting structure 1387 when horizontal force FH1 or FH2 acts on
the power module 1380. A second damping element 1386 may be
configured to attenuate or reduce the impact of horizontal force
FH1 transmitted by or between the containment vessel 1324 and the
reactor bay wall 1327. The second damping element 1386 also helps
to center or maintain a respective position or distance between the
containment vessel 1324 and the reactor bay wall 1327 when the
power module 1380 is at rest or in a static condition.
[0116] The first damping element 1376 is shown housed in the
reactor vessel trunnion 1375. A reactor vessel retaining pin 1390
is located in the reactor vessel trunnion 1375 to provide a contact
surface for the first damping element 1376. The reactor vessel
retaining pin 1390 may be an extension of the containment vessel
1324 or the containment vessel trunnion 1385, for example. In some
examples, the reactor vessel retaining pin 1390 is rigidly
connected to the containment vessel 1324. The reactor vessel
retaining pin 1390 may extend through both sides of the containment
vessel 1324.
[0117] Horizontal force FH2 may be transmitted by or between the
reactor vessel 1322 and the containment vessel 1324 via the reactor
vessel retaining pin 1390 and the first damping element 1376.
Vertical movement of the reactor vessel 1322 and containment vessel
may be constrained by the interaction between the reactor vessel
trunnion 1375, reactor vessel retaining pin 90, and the mounting
structure 1377. Vertical movement of the reactor vessel 1322 and
containment vessel 1324 may be further constrained by the
interaction between the containment vessel trunnion 1385 and the
mounting structure 1387.
[0118] The elastic damping and retaining structure 1370 may further
be configured to provide a thermal buffer for the power module
1380. In addition to attenuating, damping, or otherwise reducing
dynamic and seismic forces from being transferred to or between the
components of the power module 1380, the elastic damping and
retaining structure 1370 may reduce the thermal heat transfer
between the reactor vessel 1322 and the containment vessel 1324.
For example, one or both of the first and second mounting
structures 1377, 1387 may be lined with thermal insulation.
[0119] FIG. 14 illustrates an example process 1400 for seismically
isolating a power module. The system 1400 may be understood to
operate with, but not limited by, means illustrated or described
with respect to the various examples illustrated herein as FIGS.
1-13.
[0120] At operation 1410, a power module is supported on a support
structure. The support structure may be located at or slightly
above an approximate midpoint, or an approximate center of gravity,
of the power module.
[0121] At operation 1420, rotation of the power module is
constrained. The support structure may serve as a pivot for the
rotation.
[0122] At operation 1430, seismic forces transmitted through the
support structure to the power module are damped or attenuated. In
some examples, the seismic forces are attenuated by a damping
device comprising an elastic material.
[0123] At operation 1440, movement of the power module in one or
more transverse directions is constrained within a fixed range of
motion. Upon an attenuation of a transverse force, the power module
returns to its original at-rest position. In some examples, the
damping device comprises a rounded surface, and the support
structure comprises a rounded recess configured to house the
rounded surface.
[0124] At operation 1450, movement of the power module in a
longitudinal direction is constrained within a fixed range of
motion. Upon an attenuation of a longitudinal force, the power
module returns to its original at-rest position. The longitudinal
directional is perpendicular to the one or more transverse
directions of operation 1440.
[0125] A number of examples related to FIGS. 1-14 have been
described. Nevertheless, it will be understood that various
modifications may be made. For example, the steps of the disclosed
techniques may be performed in a different sequence, components in
the disclosed systems may be combined in a different manner, and/or
the components may be replaced or supplemented by other components.
Accordingly, other implementations are within the scope of the
following examples.
[0126] A power module may comprise a containment vessel completely
submerged in a pool of liquid, a reactor vessel housed in the
containment vessel, and a support structure that comprises support
arms coupled to opposed sides of the containment vessel. The pool
of liquid may be disposed below a terranean surface, i.e., the pool
may be subterranean. Additionally, the containment vessel may be
configured to slide in a substantially lateral direction in
response to a lateral force acting on the containment vessel.
[0127] The support structure may be located at an approximate
midpoint of the containment vessel and configured to rotate at
least one of the reactor vessel or the containment vessel about an
axis that extends between the support arms and through the
approximate midpoint of the containment vessel. Additionally, the
power module may be supported by the support structure in
combination with a buoyancy force of the pool of liquid acting on
the containment vessel.
[0128] The support structure may comprise a first support structure
disposed on a first side of the containment vessel, and the power
module may further comprise a second support structure disposed on
a second side of the containment vessel opposite the first
side.
[0129] In some examples, the support structure may be located at or
slightly above the approximate center of gravity of the power
module. In some examples, the support structure may comprise an
elastic damping device. The support arms may be rigidly attached to
the containment vessel. Additionally, the elastic damping device
may be located between and in contact with one of the support arms
and a mounting structure in the pool of liquid.
[0130] The elastic damping device may be configured to compress in
response to the support arm and the mounting structure being
pressed together. Additionally, the elastic damping device may be
configured to exert a reactionary force against at least one of the
support arm and the mounting structure in response to the support
arm and the mounting structure being pressed together
[0131] In some examples, the mounting structure may be rigidly
coupled to a reactor bay at least partially enclosing the pool of
liquid, and the mounting structure may extend from a substantially
vertical wall of the reactor bay to a location in the pool of
liquid between the substantially vertical wall and the containment
vessel. The support arm may comprise a hollow shaft. Additionally,
the mounting structure may comprise a recess configured to receive
a portion of the elastic damping device.
[0132] A pivot may be located at an interface between the support
structure and the mounting structure. For example, the pivot may be
located at or near the elastic damping device, and the containment
vessel may be configured to rotate about the pivot in response to a
rotational force acting on the containment vessel.
[0133] The power module may further comprise a base support or a
base skirt located at a lower end of the containment vessel. The
containment vessel may be configured to pivot about the support
arm, and the base support may be configured to contact an alignment
device in the pool of liquid if the containment vessel pivots about
the support arm.
[0134] The base support may be rigidly coupled to the lower end of
the containment vessel around a circumference of an outer surface
of the containment vessel. The alignment device may extend into the
pool of liquid from a bottom surface of a reactor bay at least
partially enclosing the pool of liquid, and a top portion of the
alignment devices may be disposed within a volume defined by the
base support. Additionally, the power module may comprise at least
one dampener disposed between the top portion of the alignment
device and the base support, and within the volume of the base
support.
[0135] The dampener may be configured to compress in response to
contact between the alignment device and the base support, and the
dampener may be configured exert a reactionary force against at
least one of the alignment device or the base support, in response
to the contact.
[0136] The power module may further comprise a first damping device
interposed between the reactor vessel and the containment vessel,
and a second damping device interposed between the containment
vessel and a pool wall. The first and second damping devices may be
configured to attenuate a dynamic force and/or seismic force acting
on the power module.
[0137] FIG. 15 illustrates an example reactor pressure vessel (RPV)
1500 comprising a top head 1510 and a bottom head 1520 mounted on
either end of a substantially cylindrical shaped body 1550. Bottom
head 1520 may be removably attached to body 1550 during assembly,
installation, refueling, and/or other modes of operation of RPV
1500. Bottom head 1520 may be attached to body 1550 by a bolted
flange. Additionally, RPV 1500 may comprise one or more support
structures 1530 located about a circumference of body 1550. In some
examples, RPV 1500 comprises four support structures 1530 located
at ninety degree increments around body 1550.
[0138] Support structures 1530 may comprise a support member 1535
attached to RPV 1500 and one or more mounting bases 1532. Support
member 1535 may be configured to extend away from body 1550 at an
angle in order to provide a clearance between body 1550 and the one
or more mounting bases 1532. For example, the one or mounting bases
1532 may be positioned so that they are radially located farther
away from body 1550 than any other component of RPV 1500. Support
structures 1530 may be configured to support RPV 1500 in a
generally vertical, or longitudinal direction. In some examples,
support structure 1530 may also be configured to support RPV 1500
in a generally horizontal direction, transverse direction, radial
direction, and/or lateral direction.
[0139] Support structure 1530 may be configured to provide a
thermal "anchor" for RPV 1500. For example, during thermal
expansion of RPV 1500, there may be assumed to be no thermal
expansion at the portion of RPV 1500 adjacent to support structure
1530, at least in a vertical or longitudinal direction. Rather, RPV
1500 may be understood to expand in a generally longitudinal
direction as a function of the distance from support structure
1530. A top head of RPV 1500 may move upwards and a bottom head of
RPV 1500 may move downwards, with respect to support structure
1530.
[0140] One or more radial mounts 1540 may also be mounted to body
1550. In some examples, RPV 1500 may comprise four radial mounts
1540 located at ninety degree increments around body 1550. Radial
mounts 1540 may be configured to provide lateral and/or rotational
support of RPV 1500. In some examples, radial mounts 1540 may be
configured as radial links or lugs that project from body 1550.
Radial mounts 1540 may be made operable with one or more of the
seismic isolation and/or damping systems illustrated in FIGS.
1-14.
[0141] FIG. 16 illustrates a partial cut-away view of an example
reactor module 1650 comprising a containment vessel (CNV) 1600 and
an RPV assembly, such as RPV 1500 of FIG. 15. CNV 1600 may be
configured to support RPV 1500 at one or both of support structures
1530 and radial mounts 1540. CNV 1600 may comprise a platform 1630
which projects inward toward RPV 1500 and serves as a base for
support structures 1530 to rest on. Support structures 1530 may be
constrained in the vertical direction by platform 1630 and in the
transverse or radial direction by the inner wall of CNV 1600. In
other examples, a bolted interface may be used to transfer lateral
loads from support structure 1530 to platform 1630. CNV 1600 may be
configured to support the support structures 1530 of RPV 1500 at a
steam generator plenum level of CNV 1600.
[0142] CNV 1600 may comprise a top head 1610 and a bottom head
1620. In some examples, bottom head 1620 may be removably attached
to CNV 1600 at a bolted flange 1640. CNV 1600 may be configured to
support radial mounts 1540 of RPV 1500 near flange 1640. Radial
mounts 1540 may be constrained in a longitudinal direction, a
radial direction, and/or a circumferential direction within CNV
1600. Radial mounts 1540 may be configured to allow for thermal
expansion between RPV 1500 and CNV 1600. In some examples, radial
mounts 1540 may be horizontally pinned between RPV 1500 and CNV
1660, at the bottom half of RPV 1500.
[0143] The seismic and/or dynamic loadings experienced by reactor
module 1650 may result in fuel acceleration and/or fuel impact
loads. Fuel accelerations in particular may be significantly
decreased by the provision of supports, such as radial mounts 1540,
located at or near the bottom half of RPV 1500.
[0144] CNV 1600 may be configured to contain and support RPV 1500.
Additionally, CNV 1600 may house a reactor cooling system, internal
piping, internal valves, and other components of reactor module
1650. Support structures 1530, in combination with radial mounts
1540, may be configured within reactor module 1650 to withstand
loads due to thermal transients and expansion and to support
lateral loads due to seismic and other dynamic loadings. For
example, reactor module 1650 may be configured to withstand and/or
respond to at least two types of seismic conditions, including a
Safe Shutdown Earthquake (SSE) event and an Operating Basis
Earthquake (OBE) event, as previously discussed.
[0145] Bottom head 1620 may comprise and/or be attached to a base
support, such as a base skirt 1670. The base skirt 1670 may be
rigidly mounted to, welded on, and/or form an integral part of, the
CNV 1600. Base skirt 1670 may be configured to rest on the ground
and/or on a lower surface of a reactor bay. In some examples,
substantially all of the weight of reactor module 1650 may be
supported by base skirt 1670.
[0146] One or more radial mounts 1645 may be mounted to CNV 1600.
In some examples, CNV 1600 may comprise four radial mounts 1645
located at ninety degree increments. Radial mounts 1645 may be
configured to primarily provide lateral and/or rotational support
of CNV 1600. In some examples, radial mounts 1645 may be configured
as radial links or lugs that project from CNV 1600. Radial mounts
1645 may be made operable with one or more of the seismic isolation
and/or damping systems illustrated in FIGS. 1-14.
[0147] FIG. 17 illustrates a cross-sectional view of an example
reactor module 1700 comprising an RPV 1750 and a CNV 1760. RPV 1750
may be associated with a first diameter D1 and similarly CNV 1760
may be associated with a second diameter D2 larger than first
diameter D1. A bottom head 1755 of RPV 1750 may be separated or
spaced apart from bottom head 1765 of CNV by a distance 1790.
Distance 1790 may provide space for a thermal insulation to
substantially envelop RPV 1750. In some examples, the thermal
insulation may comprise a partial vacuum.
[0148] The space provided by distance 1790 may further be
configured to provide for thermal expansion and/or thermal
transients of RPV 1750 within CNV 1760. CNV 1760 may be at least
partially submerged in water, and the amount of thermal expansion
of RPV 1750 may be considerably larger than that of CNV 1760 based
on the differences in operating temperature. Additionally, distance
1790 may provide clearance between RPV 1750 and CNV 1760 during a
seismic event to keep the vessels from contacting each other.
[0149] A reactor core 1710 may be housed within RPV 1750. Reactor
core 1710 may be spaced apart from RPV 1750 by a distance 1720. The
space formed by distance 1720 may be configured to promote
circulation of coolant within RPV 1750 to pass through reactor core
1710. Additionally, distance 1720 may provide clearance between RPV
1750 and reactor core 1710 during a dynamic event or a seismic
event or to account for thermal expansion and/or thermal
transients.
[0150] During a seismic event, seismic forces generated from within
the ground 1775 and/or from below a support surface 1740, such as a
floor of a surrounding containment building, may be transmitted to
a base support, such as a base skirt 1770 of CNV 1760. The seismic
forces may follow up through the container wall of CNV 1760 through
a transmission path 1705 which may be transferred to RPV 1750 via
one or more points of attachment, such as support structures 1530
and/or radial mounts 1540 (FIG. 15). Transmission path 1705 may
represent at least a portion of an overall example path through
which the seismic forces are transmitted, beginning with the source
of the seismic forces and ultimately continuing on to the fuel
assemblies located within RPV 1750. Other components may experience
different example transmission paths.
[0151] A bottom surface 1730 of CNV 1760 may be located some
distance above the ground 1775 and/or support surface 1740. In some
examples, the space located between CNV 1760 and the support
surface 1740 may provide room for surrounding water to cool the
exterior surface of CNV 1760.
[0152] FIG. 18 illustrates an example system 1800 comprising
seismic attenuation devices configured as radial keys 1840. Radial
keys 1840 may comprise one or more posts that extend outwardly from
an RPV 1850 about its radius and engage one or more brackets, such
as a first bracket 1810 and a second bracket 1820. The brackets may
extend inwardly from a surrounding CNV 1860. Radial keys 1840 may
be located at or near a bottom head 1855 of RPV 1850. Each of the
radial keys 1840 may be inserted between a pair of brackets, such
as first bracket 1810 and second bracket 1820. The brackets may be
located at or near a bottom head 1865 of CNV 1860. In some
examples, three or more radial keys may be spaced about the
circumference of RPV 1850 to engage a corresponding number of
bracket pairs located within the periphery of CNV 1860.
[0153] Radial keys 1840 may be configured to stabilize, dampen,
attenuate, reduce, or otherwise mitigate any dynamic or seismic
force experienced by RPV 1850. During a seismic event, radial keys
1840 may be configured to contact one or both of first bracket 1810
and second bracket 1820, to limit or prohibit movement/rotation of
RPV 1850 in a circumferential direction 1830. Contact with one or
more of the brackets may also impart friction force to resist or
dampen movement of RPV 1650 in a transverse or radial direction
1880, e.g., towards the inner wall of CNV 1860. In some examples,
the inner wall of CNV 1860 may inhibit the movement of RPV 1850 in
the radial direction 1880.
[0154] A base support, such as a base skirt 1870 attached to the
bottom of CNV 1860, may be configured to support the weight of the
reactor module comprising CNV 1860 and RPV 850. During a seismic
event, seismic forces may be transmitted from base skirt 1870 up
through the container wall of CNV 1860 through a transmission path
1805 which may transfer the seismic forces to the radial keys 1840
of RPV 1850 via the one or more brackets, such as first bracket
1810 and/or second bracket 1820. Transmission path 1805 may
represent at least a portion of an overall example path through
which the seismic forces are transmitted, beginning with the source
of the seismic forces and ultimately continuing on to the fuel
assemblies located within RPV 1850.
[0155] By transmitting seismic forces to the RPV 1850 near the
bottom head, transmission path 1805 may be considerably shorter
than transmission path 1705 (FIG. 17). In some examples, decreasing
the transmission path may result in a smaller amount of dynamic
and/or seismic force that would otherwise be imparted to RPV 1750
and to any internal components, such as the reactor core and/or
fuel rods. The amplitude and/or size of the dynamic/seismic forces
may be amplified as a function of the length of the transmission
path as the forces are transmitted from the ground or support
surface to an RPV via one or more intermediate structures.
[0156] FIG. 19 illustrates an example system 1900 comprising
seismic attenuation devices configured as radial bumpers 1910.
Radial bumpers 1910 may extend from an inner wall of a CNV 1960. A
base support, such as a base skirt 1970 attached to the bottom of
CNV 1960, may be configured to support the weight of the reactor
module comprising CNV 1960. Radial bumpers 1910 may be attached to
CNV 1960 at or near a bottom head 1920 of CNV 1960. In some
examples, radial bumpers 1910 may be attached to a cylindrical wall
1950 of CNV 1960 located above base skirt 1970.
[0157] FIG. 20 illustrates the example system 1900 of FIG. 19
together with an RPV 2050. Radial bumpers 1910 may be configured to
stabilize, dampen, attenuate, reduce, or otherwise mitigate any
dynamic or seismic force experienced by RPV 1950. During a seismic
event, radial bumpers 1910 may be configured to contact the outer
surface of RPV 1950, and to limit or prohibit movement of RPV 1950
in a transverse or radial direction. Contact with one or more of
the bumpers 1910 may also impart friction force to resist or dampen
movement/rotation of RPV 1950 in a circumferential direction.
[0158] During a seismic event, seismic forces may be transmitted
from base skirt 1970 up through the container wall of CNV 1960
through a transmission path 2005 which may transfer the seismic
forces to RPV 2050 via the one of more radial bumpers 1910. In some
examples, radial bumpers 1910 and/or radial keys 1840 (FIG. 18) may
be configured to operate with and/or to comprise one or more of the
seismic isolation and/or damping systems illustrated in one or more
of FIGS. 1-14.
[0159] FIG. 21 illustrates an example system 2100 comprising a
seismic attenuation device configured as a vertical key 2155. In
some examples, vertical key 2155 may be configured as a round or
conical post located on the bottom head 2110 of an RPV 2150.
Vertical key 2155 may be configured to fit into a recess 2165
located at the bottom head 2120 of a CNV 2160. Recess 2165 may
comprise a round hole sized to receive vertical key 2155.
[0160] Vertical key 2155 may be configured to provide lateral
support of RPV 2150 in a transverse or radial direction 2135.
Additionally, a gap 2130 may be provided between vertical key 2155
and recess 2165 to allow for thermal expansion of RPV 2150 in a
longitudinal direction 2115. In some examples, gap 2130 may be
approximately four to six inches in the longitudinal direction.
During thermal expansion of RPV 2150, a larger portion of vertical
key 2155 may be inserted into recess 2165, and effectively decrease
gap 2130 by two or more inches. In some examples, RPV 2150 may
expand due to an increase in internal pressure. Vertical key 2155
may remain at least partially inserted within recess 2165 when RPV
150 is at ambient temperature, e.g., at some nominal operation
condition or at a minimum amount of thermal expansion.
[0161] The diameter associated with vertical key 2155 may be
sufficiently less than the diameter of recess 2165 to provide for a
clearance and/or tolerance during fit-up. In some examples, the
diameter of vertical key 2155 may be between one and two feet and
the clearance between vertical key 2155 and a contact point 2125
within recess 2165 may be approximately one eighth of an inch, one
sixteenth of an inch, or less. In still other examples, the
relative diameters may be only slightly different such that
vertical key 2155 may be pressure-fit into recess 2165 with
virtually no clearance.
[0162] The reactor module assembly may experience varying
differential thermal growth depending if the reactor module is in
shut down (i.e., cold) operating conditions, or in full power
(i.e., hot) operating conditions. Accordingly, one or more of the
seismic attenuation devices described above may be configured to
stabilize, dampen, attenuate, reduce, or otherwise mitigate any
dynamic or seismic force experienced by the RPV and/or the reactor
core in both the hot and cold operating conditions. A radial gap
and/or spacing between the one or more seismic attenuation devices
and the adjacent vessel surface may be provided to accommodate the
differential radial growth. In some examples, the radial gap
between vertical key 2155 and contact point 2125 may be provided to
allow for thermal expansion of vertical key 2155 in the radial
direction 2135. The distance of the radial gap may vary according
to the diameter of the vertical key.
[0163] Vertical key 2155 may be inserted and/or removed from recess
2165 during assembly, installation, refueling, and/or other modes
of operation. The system 2100 illustrated in FIG. 21 may be
configured to assemble RPV 2150 together with CNV 2160
independently of circumferential alignment. For example, vertical
key 2155 may be configured to be installed into recess 2165
regardless of the rotational orientation of RPV 2150. Additionally,
the lower corner(s) of vertical key 2155 may be tapered to
facilitate alignment and/or entry into recess 2165.
[0164] Vertical key 2155 may be configured to stabilize, dampen,
attenuate, reduce, or otherwise mitigate any dynamic or seismic
force experienced by RPV 2150. During a seismic event, vertical key
2155 may be configured to contact recess 2165 at one or more
lateral contact points 2125, to limit or prohibit movement/rotation
of RPV 2150 in the radial direction 2135. In some examples, contact
between vertical key 2155 and recess 2165 may also impart friction
force to resist rotational movement of RPV 2150 within CNV 2160
and/or to resist vertical movement of RPV 2150 in the longitudinal
direction 2115.
[0165] A base support, such as a base skirt 2170 attached to the
bottom of CNV 2160, may be configured to support the weight of the
reactor module comprising CNV 2160 and RPV 2150. During a seismic
event, seismic forces may be transmitted from base skirt 2170
through a transmission path 2105 which may transfer the seismic
forces to the vertical key 2155 of RPV 2150 via the one or more
lateral contact points 2125 within recess 2165.
[0166] Vertical key 2155 may extend downward from the RPV 2150 at
the longitudinal centerline of the bottom head 2110. The bottom
head 2120 of CNV 2160 may be reinforced, such as by adding material
or increasing the thickness of the wall of bottom head 2120. In
some examples, recess 2165 may be machined out of the inner surface
of the bottom head 2120 of CNV 2160.
[0167] Locating a seismic attenuation device, such as vertical key
2155, at the bottom head 2110 of RPV 2150 may significantly reduce
the seismic acceleration and impact load on the fuel assemblies
(e.g. by six times or more) as compared to using radial mounts 1540
as illustrated in FIG. 15. A relatively shorter transmission path
may effectively eliminate or lower the transmissibility of forces
as compared to a transmission path which passes through one or more
sub-systems that are located between the source (ground motion) and
the fuel assemblies.
[0168] In some examples, vertical key 2155 may be forged as an
integral part of the bottom head 2110 of RPV 2150. In examples
where vertical key 2155 is attached, e.g., welded, to bottom head
2110, vertical key 2155 may be made out of the same material as
bottom head 2110. For example, RPV 2150, bottom head 2110, and/or
vertical key 2155 may be made from SA-508, Grade 3, Class 1 steel
forgings or other suitable materials.
[0169] A suction line 2190 may be configured to remove fluid
located within recess 2165. In some examples, an annular space 2175
between RPV 2150 and CNV 2160 may be evacuated during operation of
the reactor module. The removal of fluid and/or gases through
suction line 2190 may facilitate creating and/or maintaining an
evacuation chamber which substantially surrounds RPV 2150.
[0170] FIG. 22 illustrates a further example system 2200 comprising
a seismic attenuation device configured as a vertical key or post
2265. In some examples, vertical key 2265 may be configured as a
round or conical post located on the bottom head 2220 of a CNV
2260. Vertical key 2265 may be configured to fit into a recess 2255
located at the bottom head 2210 of an adjacent RPV 2250. Recess
2255 may comprise a round hole sized to receive vertical key
2265.
[0171] Vertical key 2265 may be configured to provide lateral
support of RPV 2250 in a transverse or radial direction 2235.
Additionally, a gap 2230 may be provided between vertical key 2265
and recess 2255 to allow for thermal expansion of RPV 2250 in a
longitudinal direction 2215. The diameter associated with vertical
key 2265 may be sufficiently less than the diameter of recess 2255
to provide for a clearance and/or tolerance during fit-up. In some
examples, the clearance may be approximately one sixteenth of an
inch or less. In still other examples, the relative diameters may
be only slightly different such that vertical key 2265 may be
pressure-fit into recess 2255 with virtually no clearance.
[0172] Vertical key 2265 may be inserted and/or removed from recess
2255 during assembly, installation, refueling, and/or other modes
of operation. The system 2200 illustrated in FIG. 22 may be
configured to assemble RPV 2250 together with CNV 2260
independently of circumferential alignment. For example, vertical
key 2265 may be configured to be installed into recess 2255
regardless of the rotational orientation of RPV 2250. Additionally,
the lower corner(s) of vertical key 2265 may be tapered to
facilitate alignment and/or entry into recess 2255.
[0173] Vertical key 2265 may be configured to stabilize, dampen,
attenuate, reduce, or otherwise mitigate any dynamic or seismic
force experienced by RPV 2250. During a seismic event, vertical key
2265 may be configured to contact recess 2255 at one or more
lateral contact points 2225, to limit or prohibit movement/rotation
of RPV 2250 in the radial direction 2235. In some examples, contact
between vertical key 2265 and recess 2255 may also impart friction
force to resist rotational movement of RPV 2250 within CNV 2260
and/or to resist vertical movement of RPV 2250 in the longitudinal
direction 2215.
[0174] Vertical key 2230 may extend upward from CNV 2260 at a
longitudinal centerline 2290 of the bottom head 2220. The bottom
head 2210 of RPV 2250 may be reinforced, such as by adding material
or increasing the thickness of the wall of bottom head 2210. In
some examples, recess 2255 may be machined out of the outer surface
of the bottom head 2220 of RPV 2250.
[0175] A base support, such as a base skirt 2270 attached to the
bottom of CNV 2260, may be configured to support the weight of the
reactor module comprising CNV 2260 and RPV 2250. During a seismic
event, seismic forces may be transmitted from base skirt 2270
through bottom head 2220 to RPV 2250 via the transmission of forces
from vertical key 2230 to one or more lateral contact points 2225
within recess 2255.
[0176] Base skirt 2270 may rest on a floor 2240 comprising
reinforced concrete. Additionally, base skirt 2270 may comprise an
annular shaped structure connected to the circumference of bottom
head 2220. Base skirt 2270 may be configured to be placed next to
one or more stops 2280. In some examples, the one or more stops
2280 may comprise an annular ring-shaped structure attached to the
floor 2240. The one or more stops 2280 may be configured to align
RPV 2250 when it is placed on the floor 2240. Additionally, the one
or more stops 2280 may be configured to restrict and/or prohibit
lateral movement of CNV 2260 in the radial direction 2235.
[0177] The bottom head 2220 of CNV 2260 may be located some
distance 2245 above the floor 2240 upon which base skirt 2270 is
placed on. In some examples, distance 2245 may be between six
inches and one foot. The space located between CNV 2260 and the
floor 2240 may provide room for surrounding water to cool the
exterior surface of CNV 2260. Additionally, base skirt 2270 may
comprise one or more through holes 2275 to allow the water to enter
the space within base skirt 2270 in order to cool bottom head
2220.
[0178] In some examples, vertical key 2265 may be forged as an
integral part of the bottom head 2220 of CNV 2260. In examples
where vertical key 2265 is attached, e.g., welded, to bottom head
2220, vertical key 2265 may be made out of the same material as
bottom head 2220. For example, CNV 2260, bottom head 2220, and/or
vertical key 2255 may be made from SA-508, Grade 3, Class 1 steel
forgings, or other suitable materials.
[0179] Providing radial spacing and/or clearance about vertical key
2265 may provide for some slight lateral movement of RPV 2250
within CNV 2260 to provide a flexible, or non-rigid stability
system. While RPV 2250 may be allowed to move, it may nevertheless
be constrained by recess 2255 to limit the amount of lateral
movement. A flexible stability system may impart and/or transmit
less force than a rigidly connected system.
[0180] One or more of the a seismic attenuation devices described
above may be configured to stabilize, dampen, attenuate, reduce, or
otherwise mitigate any dynamic or seismic forces, such as in the
lateral or radial direction, without restraining the differential
thermal growth between the RPV and the CNV. For example, the
thermal growth of the RPV, such as RPV 2250, may be based on a
temperature change between ambient conditions and the design
temperature of the reactor module, which in some examples may be
approximately 650.degree. F. On the other hand, the thermal growth
of the CNV, such as CNV 2260 may be essentially non-existent when
the CNV is submerged in, or at least partially surrounded by, a
pool of water that is near ambient temperature.
[0181] By attaching vertical key 2265 to CNV 2260, the thermal
expansion of RPV 2250 may result in the internal diameter of recess
2230 increasing, whereas the external diameter of vertical key 2265
may remain essentially constant, independent of operating
temperatures within RPV 2250. Accordingly, the lateral clearance
between vertical key 2265 and recess 2230 could be made just large
enough to facilitate assembly and/or fit-up, but would not
necessarily need to account for thermal expansion of RPV 2250
and/or vertical key 2265 in the radial direction 2235. In some
examples, RPV 2250 and CNV 2260 may be considered essentially
thermally isolated from each other, regardless of any incidental
contact between vertical key 2265 and recess 2230.
[0182] FIG. 23 illustrates an example system 2300 comprising a
seismic attenuation device configured as a vertical key or post
2365 with an alternative force transmission path 2305. During a
seismic event, seismic forces may be transmitted from one or more
stops 2380 and/or the ground 2305 to a base support such as a base
skirt 2370. Laterally transmitted forces from the one or more stops
2305 to base skirt 2370 may travel through transmission path 2305
and continue along a bottom head 2320 of a CNV 2360 before being
transferred to RPV 2250 via the one or more lateral contact points
2325 between recess 2255 of RPV 2250 and the radial surface of
vertical key 2365.
[0183] By locating base skirt 2370 closer to a longitudinal
centerline 2390 of RPV 2250 and/or CNV 2360, where vertical key
2365 and or recess 2255 may be aligned, the transmission path 2305
between the one or more stops 2380 and RPV 2250 may be made shorter
as compared to a transmission path associated with system 2200
(FIG. 22).
[0184] FIG. 24 illustrates a further example system 2400 comprising
a seismic attenuation device configured as a vertical key or post
2465 with an alternative force transmission path 2405. During a
seismic event, lateral forces may be transmitted from one or more
stops 2470 to a base support such as a base skirt 2470.
Transmission path 2405 may continue from base skirt 2470 in a
substantially linear direction both through a bottom head 2420 of
CNV 2460 and through vertical key 2465 before being transferred to
RPV 2250 via the one or more lateral contact points 2425 between
recess 2255 of RPV 2250 and the radial surface of vertical key
2465.
[0185] By locating base skirt 2470 closer to a longitudinal
centerline 2490 of RPV 2250 and/or CNV 2460, the transmission path
2405 associated with system 2400 may be made shorter as compared to
the transmission path 2305 associated with system 2300 (FIG. 23).
In some examples, base skirt 2470 may be located directly below at
least a portion of radial key 2465. In other examples, base skirt
2470 may be located directly below at least a portion of recess
2255. Transmission path 2405 may be understood to provide an
essentially direct, linear path from the ground, or support
surface, to RPV 2250.
[0186] In some examples, recess 2255 may be formed in a boss 2450
which extends from bottom head 2210 into the interior of RPV 2250.
Boss 2450 may comprise one or more curved or sloped surfaces 2252
which are configured to direct coolant flow 2256 in an upward
direction to facilitate uniform mass flow distribution of coolant
entering the reactor core. In some examples, boss 2450 may be
configured to direct at least a portion of coolant flow 2256 to a
periphery of the reactor core.
[0187] FIG. 25 illustrates an example system 2500 comprising a
seismic attenuation device configured as an integrated vertical key
2565 and lateral support 2575. Vertical key 2565 may extend upward
in a substantially vertical direction from the inner surface of a
CNV 2560 into the adjacent recess 2255 of RPV 2250 contained within
CNV 2560. Lateral support 2575 may extend downward in a
substantially vertical direction from the outer surface of CNV 2560
towards a support surface 2540. In some examples, both vertical key
2565 and lateral support 2575 may be vertically aligned along a
longitudinal centerline 2590 of one of both of CNV 2560 and RPV
2250.
[0188] The weight of RPV 2250 may be primarily supported by a base
support such as base skirt 2570, similar to base skirt 1970 of FIG.
19. System 2500 may comprise a force transmission path 2505. During
a seismic event, lateral forces may be transmitted from one or more
stops 2580 to lateral support 2575. Transmission path 2505 may
continue from lateral support 2575 in a substantially linear
direction both through a bottom head 2520 of CNV 2560 and through
vertical key 2565 before being transferred to RPV 2250 via one or
more lateral contact points between recess 2255 of RPV 2250 and a
radial surface of vertical key 2565.
[0189] In some examples, lateral support 2575 may be located
directly below at least a portion of radial key 2565 and/or recess
2255. Transmission path 2505 may be understood to provide an
essentially direct, linear path from support surface 2540 to RPV
2250. Lateral support 2575 may be configured to contact the one or
more stops 2580 without directly contacting support surface 2540.
In some examples, neither vertical key 2565 nor lateral support
2575 are configured to support any of the weight of RPV 2250 or CNV
2560.
[0190] FIG. 26 illustrates an example system 2600 comprising an
attenuation device configured as a vertical key 2680 having a
conical shaped surface 2685. Key 2680 may be configured to fit
within a recess 2670 having a complimentary shaped conical inner
surface 2675. The sloped or angled contour of conical surfaces
2675, 2685 may provide for a lateral clearance 2690 between key
2680 and recess 2670. Additionally, the conical surfaces 2675, 2685
may facilitate fit-up and/or assembly of a reactor module
comprising an RPV 2650 and a surrounding CNV 2660. In some
examples, FIG. 26 may be considered as illustrating a reactor
module comprising RPV 2650 and/or CNV 2660 in a nominal or
non-expanded state.
[0191] FIG. 27 illustrates an enlarged partial view of the example
system 2600 of FIG. 26 with RPV 2650 undergoing thermal expansion.
The thermally expanding RPV 2750 is shown in dashed lines,
indicating thermal expansion in both a longitudinal direction and
radial direction. For example, a first length 2710 associated with
RPV 2650 may increase to a second length 2720 associated with
thermally expanding RPV 2750. Similarly, RPV 2650 may expand in the
radial direction as illustrated by the enlarged diameter 2730
associated with a thermally expanded recess 2770 including an
enlarged conical shaped surface 2775.
[0192] FIG. 28 illustrates an enlarged partial view of the example
system 2600 of FIG. 26 in an expanded state. The sloped or angled
contour of conical surfaces 2685, 2775 may provide for a lateral
clearance 2890 between key 2680 of CNV 2660 and thermally expanded
recess 2770. The lateral clearance 2890 associated with a thermally
expanded RPV 2750 may be approximately equal to the lateral
clearance 2690 associated with RPV 2650 (FIG. 26) in the nominal or
non-expanded state. In some examples, lateral clearance 2890 may be
approximately one sixteenth of an inch or less. In other examples,
lateral clearance 2890 may be approximately one eighth of an inch
or less. Other and/or larger dimensions are also contemplated
herein. Maintaining a lateral clearance at less than some
predetermined dimension may effectively make any lateral movement
between key 2680 and recess 2670 negligible with respect to
determining dynamic impact forces between RPV 2650 and CNV
2660.
[0193] FIG. 29 illustrates a further example system 2900 comprising
an attenuation device configured as a conical shaped key 2980
having a conical shaped surface 2985. Key 2980 may be configured to
fit within a recess 2970 having a complimentary shaped conical
inner surface 2975. Key 2980 may extend downward in a substantially
vertical direction from the outer surface of an RPV 2950 into the
adjacent recess 2970 of a surrounding CNV 2960. The sloped or
angled contour of conical surfaces 2975, 2985 may provide for a
lateral clearance 2990 between key 2980 and recess 2970.
Additionally, the conical surfaces 2975, 2985 may facilitate fit-up
and/or assembly of a reactor module comprising RPV 2950 and CNV
2960.
[0194] FIG. 30 illustrates an example operation 3000 for
transmitting dynamic or seismic forces through a reactor module
structure. The reactor module structure may comprise a containment
vessel that houses a reactor pressure vessel. The reactor vessel
may be spaced apart from the containment vessel by an annular
containment volume. In some examples, the annular containment
volume may be evacuated to provide thermal insulation between the
containment vessel and the reactor pressure vessel.
[0195] At operation 3010, some or substantially all of the weight
of the reactor pressure vessel within the containment vessel may be
supported by a support structure. The support structure may pass
through the annular containment volume.
[0196] At operation 3020, a seismic force may be transmitted to the
containment vessel. The containment vessel may be supported by a
base support located near a bottom head of the containment vessel.
In some examples, the base support may comprise a base skirt.
[0197] At operation 3030, the seismic force that is received by the
reactor pressure vessel may be attenuated by an attenuation device.
In some examples, the attenuation device may not be configured to
support any of the weight of the reactor pressure vessel. The
attenuation device may pass through the annular containment volume.
In some examples, the attenuation device may be located along a
longitudinal centerline of the reactor pressure vessel and/or a
longitudinal centerline of the containment vessel. The attenuation
device may be configured to attenuate the seismic force in a
direction transverse to the longitudinal centerline(s).
[0198] Additionally, the attenuation device may form part of a
seismic force attenuation path which transfers the seismic force
from the containment vessel to the reactor pressure vessel. The
seismic force attenuation path may comprise a vertical portion that
passes through a base support located near the bottom head of the
containment vessel. The attenuation device may be configured to
attenuate the seismic force in direction that is substantially
transverse to the vertical portion of the seismic force attenuation
path.
[0199] FIG. 31 illustrates an example system 3100 comprising an
attenuation device configured as a stair-step shaped key 3180. Key
3180 may be configured to fit within a recess 3170 having a
complimentary shaped stair-step inner surface. Key 3180 may extend
upward in a substantially vertical direction from the inner surface
of a CNV 3160 into the adjacent recess 3170 of an RPV 3150. The
stair-step shape of key 3180 may comprise a first step 3182 having
a first diameter and a second larger step 3184 having a second
diameter. In some examples, FIG. 31 may be considered as
illustrating a reactor module comprising RPV 3150 and/or CNV 3160
in a nominal or non-expanded state, in which a lateral clearance is
provided between first step 3182 and recess 3170.
[0200] FIG. 32 illustrates an enlarged partial view of the example
system 3100 of FIG. 31 with RPV 3150 in an enlarged or expanded
state. A lateral clearance 3250 between key 3180 and recess 3170 in
the expanded state may be approximately equal to the lateral
clearance associated with RPV 3150 in the nominal or non-expanded
state, as illustrated in FIG. 31.
[0201] Although at least some of the examples provided herein have
primarily described a pressurized water reactor and/or a light
water reactor, it should be apparent to one skilled in the art that
the examples may be applied to other types of power systems. For
example, one or more of the examples or variations thereof may also
be made operable with a boiling water reactor, sodium liquid metal
reactor, gas cooled reactor, pebble-bed reactor, and/or other types
of reactor designs.
[0202] It should be noted that examples are not limited to any
particular type of fuel employed to produce heat within or
associated with a nuclear reaction. Any rates and values described
herein are provided by way of example only. Other rates and values
may be determined through experimentation such as by construction
of full scale or scaled models of a nuclear reactor system.
[0203] Having described and illustrated various examples herein, it
should be apparent that other examples may be modified in
arrangement and detail. We claim all modifications and variations
coming within the spirit and scope of the following claims.
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