U.S. patent application number 16/554264 was filed with the patent office on 2021-01-21 for thorium molten salt system using internally generated proton-induced neutrons.
This patent application is currently assigned to Texas Thorium, LLC. The applicant listed for this patent is Texas Thorium, LLC. Invention is credited to Yassin A. Hassan, Lin Shao.
Application Number | 20210020323 16/554264 |
Document ID | / |
Family ID | 1000004366947 |
Filed Date | 2021-01-21 |
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United States Patent
Application |
20210020323 |
Kind Code |
A1 |
Shao; Lin ; et al. |
January 21, 2021 |
Thorium Molten Salt System Using Internally Generated
Proton-Induced Neutrons
Abstract
A method of generating power using a Thorium-containing molten
salt fuel is disclosed. One example includes the steps of providing
a vessel containing a molten salt fuel, generating a proton beam
externally to the vessel, where the externally generated proton
beam being of an energy level sufficient to interact with the salt
in the vessel to produce a (p, n) reaction resulting in the
generation of a neutron at the first energy level. Neutrons
generated within the vessel through the (p, n) reactions caused by
the externally generated proton's interaction with the at least one
salt are utilized to produce a fission reaction where the fission
reaction increases the heat content of the molten salt within the
vessel. In the example, a heat exchanger is used to extract heat
from the molten salt within the vessel and power is generated from
the extracted heat.
Inventors: |
Shao; Lin; (College Station,
TX) ; Hassan; Yassin A.; (College Station,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Texas Thorium, LLC |
Houston |
TX |
US |
|
|
Assignee: |
Texas Thorium, LLC
Houston
TX
|
Family ID: |
1000004366947 |
Appl. No.: |
16/554264 |
Filed: |
August 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16517195 |
Jul 19, 2019 |
10755830 |
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16554264 |
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16517096 |
Jul 19, 2019 |
10748670 |
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16517195 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05H 2007/222 20130101;
H05H 7/22 20130101; H05H 2007/225 20130101; G21G 1/08 20130101;
G21G 1/10 20130101; G21C 3/58 20130101; G21C 5/12 20130101 |
International
Class: |
G21G 1/08 20060101
G21G001/08; G21G 1/10 20060101 G21G001/10; G21C 5/12 20060101
G21C005/12; G21C 3/58 20060101 G21C003/58; H05H 7/22 20060101
H05H007/22 |
Claims
1. A method of generating power using a Thorium-containing molten
salt fuel, the method comprising the steps of: providing a vessel
containing a molten salt fuel, the molten salt fuel comprising
Thorium and at least one salt containing an atom capable of
interacting with a proton of sufficient energy to produce a (p, n)
reaction resulting in the generation of a neutron at a first energy
level; providing a lid to the vessel, the lid comprising a top and
a bottom with at least one opening through the lid containing an
impeller pump assembly configured to recirculate the molten salt
fuel in the vessel, at least two openings through the lid
containing input and output piping for a sealed heat exchanger coil
positioned adjacent the bottom of the lid, and at least one opening
through which is a window configured to permit the passage of
protons; attaching the lid to the vessel; generating a proton beam
externally to the vessel, the externally generated proton beam
being of an energy level sufficient to interact with the at least
one salt in the vessel to produce a (p, n) reaction resulting in
the generation of a neutron at the first energy level; directing
the externally generated proton beam into the vessel such that at
least some protons forming the beam will interact with the atom in
the at least one salt contained in the vessel; causing interaction
between the externally generated proton beam and the at least one
salt contained in the vessel to produce (p, n) reactions resulting
in the generation of neutrons within the vessel; utilizing neutrons
generated within the vessel through the (p, n) reactions caused by
the externally generated proton's interaction with the at least one
salt to produce an absorption reaction involving the generated
neutrons and Thorium within the vessel; utilizing neutrons
generated from the absorption reaction to produce a fission
reaction, the fission reaction increasing the heat content of the
molten salt fuel within the vessel; utilizing a heat exchanger to
extract heat from the molten salt fuel within the vessel; and
generating power from the extracted heat.
2. The method of claim 1 wherein the step of providing a vessel
containing a molten salt fuel comprises the step of providing a
molten salt comprising at least one Lithium salt.
3. The method of claim 1 wherein the step of generating a proton
beam externally to the vessel comprises the step of operating a
vacuum accelerator assembly.
4. The method of claim 3 wherein the step of generating a proton
beam externally to the vessel comprises the step of controlling the
vacuum accelerator assembly to vary the intensity of the externally
generated proton beam.
5. The method of claim 1 wherein the step of directing the
externally generated proton beam into the vessel involves the step
of passing the externally generated proton beam through the at
least one window opening.
6. The method of claim 1 wherein the step of directing the
externally generated proton beam into the vessel involves the step
of passing the externally generated proton beam through the at
least one window opening comprising titanium.
7-14. (canceled)
15. A method of generating power comprising the steps of: providing
a vessel having only one opening containing a molten salt fuel, the
molten salt fuel comprising Thorium and at least one salt;
providing a lid to the vessel, the lid comprising openings that are
sealed by at least one impeller assembly, at least two pipes
configured to attach to a heat exchanger, and at least one window;
securing the lid to the vessel thereby sealing the one opening of
the vessel; generating a proton beam having an energy level
sufficient to interact with the at least one salt in the vessel to
generate neutrons; directing the externally generated proton beam
into the molten salt fuel, such that the protons comprising the
proton beam interact with the at least one salt to produce
neutrons; utilizing neutrons generated within the vessel to produce
a fission reaction within the vessel, the fission reaction
generating heat; utilizing a heat exchanger to extract heat from
the vessel; and generating power from the extracted heat.
16. The method of claim 15 wherein the at least one salt is a
Fluoride salt.
17. The method of claim 15 wherein the at least one salt includes
Lithium.
18. The method of claim 15 wherein the step of directing the
externally generated proton beam into the molten salt fuel
comprises the step of directing the proton beam through the
lid.
19. The method of claim 15 wherein the fission reaction involves
the fissioning of Uranium.
20. The method of claim 15 wherein the step of generating a proton
beam having an energy level sufficient to interact with the at
least one salt in the vessel to generate neutrons comprises the
step of generating a proton beam having an energy level of at least
10 MeV.
Description
[0001] CROSS REFERENCE TO RELATED APPLICATIONS
[0002] This application is a Continuation of U.S. patent
application Ser. No. 16/517,195, titled, "Thorium Molten Salt
System for Energy Generation," filed on Jul. 19, 2019, which is a
Continuation of U.S. patent application Ser. No. 16/517,096,
titled, "Thorium Molten Salt Assembly for Energy Generation," also
filed on Jul. 19, 2019.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] Not applicable.
REFERENCE TO APPENDIX
[0004] Not applicable.
BACKGROUND OF THE INVENTION
[0005] Field of the Invention. The inventions disclosed and taught
herein relate generally to a system for generating power using a
Thorium-containing liquid molten salt fuel and, more specifically,
an accelerator-driven Thorium molten salt system for generating
process heat and/or electricity resulting from nuclear fission
reactions.
Description of the Related Art
[0006] Attempts have been made to provide an accelerator-driven
system for the generation of energy using fuel material containing
Thorium. To date, such systems have primarily been focused on the
use of a solid or molten lead (or other heavy metal) spallation
target to generate neutrons used to initiate or sustain nuclear
fission reaction and fuel initially comprising of mixtures of
Plutonium and Thorium. Examples of such systems are discussed
below.
[0007] Ashley, Coats et. al, "The accelerator-driven Thorium
reactor power station," Energy, Vol. 164, Issue EN3 at 127-135
(August 2011 Issue) discusses an accelerator-driven Thorium reactor
in which a particle accelerator injects high-energy particles into
a molten lead target to release neutrons via the spallation
process. The article indicates that a fissile starter, such as
Plutonium from spent fuel, is required, and that the core of the
system includes a series of fuel pins, each containing mixed-oxide
pellets comprised of Plutonium and Thorium. A similar system is
disclosed in Ludewig and Aronson, "Study of Multi-Beam Accelerator
Driven Thorium Reactor" (March 2011).
[0008] U.S. Patent Application Publication No. US2013/0051508,
"Accelerator Driven Sub-Critical Core" purports to disclose "a
fission power generator [that] includes a sub-critical core and a
plurality of proton beam generators" where the generated proton
beams "via spallation" generate neutrons for use in the system.
[0009] The use of heavy metal spallation targets poses several
challenges as does the use of fuel initially containing Plutonium
or Uranium.
[0010] The present inventions are directed to providing an enhanced
system for energy generation providing benefits over, and
overcoming shortcomings of, the systems and methods discussed in
the materials referenced above, and other existing systems.
BRIEF SUMMARY OF THE INVENTION
[0011] A brief non-limiting summary of one of the many possible
embodiments of the present invention is:
[0012] A method of generating power using a Thorium-containing
molten salt fuel, the method including the steps of: providing a
vessel containing a molten salt fuel, the molten salt fuel
comprising Thorium and at least one salt containing a nucleus
capable of interacting with a proton of sufficient energy to
produce a (p, n) reaction resulting in the generation of a neutron
at a first energy level; generating a proton beam externally to the
vessel, the externally generated proton beam being of an energy
level sufficient to interact with the at least one salt in the
vessel to produce a (p, n) reaction resulting in the generation of
a neutron at the first energy level; directing the externally
generated proton beam into the vessel such that at least some
protons forming the beam will interact with the nucleus forming a
part of the at least one salt contained in the vessel; causing
interaction between the externally generated proton beam and the at
least one salt contained in the vessel to produce (p, n) reactions
resulting in the generation of neutrons within the vessel;
utilizing neutrons generated within the vessel through the (p, n)
reactions caused by the externally generated proton's interaction
with the at least one salt to produce an absorption reaction
involving the generated neutrons and Thorium within the vessel;
utilizing neutrons generated within the vessel through the (p, n)
reactions caused by the externally generated proton's interaction
with the at least one salt to produce a fission reaction involving
the generated neutrons, the fission reaction increasing the heat
content of the molten salt within the vessel; utilizing a heat
exchanger to extract heat from the molten salt within the vessel;
and generating power from the extracted heat
[0013] Additionally, or alternatively, a method in accordance of
with the present disclosure may include the steps of: producing a
proton beam, wherein an average energy level of the protons
comprising the proton beam is at least 2.4 MeV; providing a molten
salt assembly comprising a main body, a lid, a tubular member
positioned inside the main body, and a quantity of
Thorium-containing molten salt within the main body; generating a
proton beam having an average energy level of at least 2.4 MeV;
directing the proton beam through the lid of the molten salt
assembly into the molten salt within the main body to induce (p, n)
reactions between protons forming the proton beam and at least one
material within the molten salt, wherein the induced (p, n)
reactions result in the production of at least some neutrons having
an energy level of at least 0.7 MeV and wherein: at least some of
the produced neutrons interact with Thorium-232 atoms within the
molten salt to produce Thorium-233 atoms; at least some of the
produced neutrons interact with Uranium-233 atoms within the molten
salt to fission the Uranium-233 atoms; and the fissioning of the
Uranium-233 atoms produces heat.
[0014] Additionally, or alternatively, methods in accordance with
the present disclosure may comprising the step of providing a
molten salt within the assembly that includes a lithium salt,
and/or a Beryllium salt and/or varying the shape of the proton
beam.
[0015] Other potential aspects, variants and examples of the
disclosed technology will be apparent from a review of the
disclosure contained herein.
[0016] None of these brief summaries of the inventions is intended
to limit or otherwise affect the scope of the appended claims, and
nothing stated in this Brief Summary of the Invention is intended
as a definition of a claim term or phrase or as a disavowal or
disclaimer of claim scope.
DESCRIPTION OF THE VIEWS OF THE DRAWINGS
[0017] The following figures form part of the present specification
and are included to demonstrate further certain aspects of the
present invention. The invention may be better understood by
reference to one or more of these figures in combination with the
detailed description of specific embodiments presented herein.
[0018] While the inventions disclosed herein are susceptible to
various modifications and alternative forms, only a few specific
embodiments have been shown by way of example in the drawings and
are described in detail below. The figures and detailed
descriptions of these specific embodiments are not intended to
limit the breadth or scope of the inventive concepts or the
appended claims in any manner. Rather, the figures and detailed
written descriptions are provided to illustrate the inventive
concepts to a person of ordinary skill in the art and to enable
such person to make and use the inventive concepts.
[0019] FIGS. 1A and 1B illustrates an embodiment of an exemplary
accelerator-driven sub-critical Thorium molten salt system 1000 for
generating useful energy (for example in the form of process heat
and/or electricity) in accordance with certain teachings of
this
[0020] FIG. 2A provides details of the exemplary particle beam
source 200 of FIG. 1. disclosure.
[0021] FIG. 2B illustrates an exemplary vacuum accelerator assembly
204 that may be used to form the particle beam source 200 of FIG.
2A.
[0022] FIG. 2C generally illustrates the way the exemplary particle
beam source 200 may be operated to generate protons of a first
energy level.
[0023] FIG. 2D illustrates the way the particle beam source 200 of
FIG. 2A may be operated to produce a proton beam of a second energy
level, where the second energy level is less than the first energy
level discussed above.
[0024] FIGS. 2E1, 2E2, 2E3 and 2E4 illustrate exemplary first,
second, third and fourth beam shape and directional combinations
that may be generated using the exemplary electromagnetic forming
and steering assembly 208 of FIGS. 2A-2D.
[0025] FIGS. 3A-3H2 and 3J1-3J3 illustrate aspects of exemplary
Thorium molten salt assemblies 300 that may be used in connection
with the exemplary system 1000 of FIG. 1.
[0026] FIGS. 4A-4H3 and 4J1-4J2 illustrate examples of a novel
Thorium fuel rod structure and fuel rod assembly utilizing such
fuel rods constructed in accordance with certain teachings of this
disclosure.
[0027] FIG. 5 illustrates an exemplary shielding assembly 700 for
use with the exemplary systems 1000 disclosed herein to shield the
external environment from particles and rays potentially generated
through operation of the disclosed exemplary systems.
[0028] FIG. 6 provides a very crude, approximated, generalized
relative indication of the amounts of Thorium-232 and Uranium-233
that can exist for the system of FIGS. 1A and 1B over time if it is
assumed that the neutron source provides a relatively constant
supply of neutrons.
[0029] FIGS. 7A-7D provide JANIS-generated graph reflecting the
cross-sections of various isotopes that may exist within the molten
salt assembly 300 of FIGS. 1A-1B.
[0030] FIGS. 8A-8H generally illustrate how the particle beam
source 200 of FIGS. 1A and 1B may be used to generate particles,
such as protons, having first or second energy levels and the
direction of those particles to various locations within the molten
salt assembly 300 of FIGS. 1A and 1B.
[0031] FIG. 9A illustrates one exemplary method of operating a
system 1000 constructed in accordance with the teachings of the
present disclosure to initially promote the generation of fast
neutrons and fission of Thorium (Thorium-232) and thereafter to
promote the generation of thermal neutrons and the fission of
Uranium (Uranium-233).
[0032] FIG. 9B illustrates a method by which the exemplary system
1000 described above may be operated to reduce the amount of
undesirable waste in the system through a burn-down process.
[0033] FIG. 9C illustrates a method by which the exemplary system
1000 disclosed herein can be operated during the periods of high
energy demand to maximize production of energy though fission of
Uranium-233 and, during periods of low energy demand, operated to
promote the generation of fast neutrons to burn-up of undesirable
waste in the system.
[0034] FIG. 10 illustrates an alternate embodiment of the system
1000 of FIGS. 1A and 1B in which fast and/or thermal neutrons
desired for operation of the system are generated outside of the
molten salt assembly 300.
[0035] FIGS. 11A-11F illustrates exemplary neutron source targets
230 that may be used in connection with the embodiment of FIG.
10.
[0036] FIG. 12 generally illustrates the generated neutron flux
levels and energy levels when neutron generating targets such as
those illustrated in FIG. 11D are used and a Beryllium target is
bombarded with protons having energy levels of at least
approximately 4.5 MeV and a Lithium target is bombarded with
protons having energy levels of at least approximately 3.0 MeV.
DETAILED DESCRIPTION
[0037] FIGS. 1A and 1B illustrate, in block and rough schematic
form a first embodiment of an exemplary accelerator-driven
sub-critical Thorium molten salt system 1000 for generating useful
energy (for example in the form of process heat and/or electricity)
in accordance with certain teachings of this disclosure.
[0038] As reflected in FIG. 1A-1B, the exemplary system 1000
includes a particle beam source 200 for producing a particle
beam.
[0039] In the example of FIG. 1A-1B, the particle beam source 200
is adapted to vary the energy level of the produced particle beam
such that the energy of the particles comprising the proton beam
can vary between at least a first energy level and a second energy
level, where the first energy level is at least approximately 4.5
MeV (and potentially up to or above 6 MeV) and the second energy
level is at least 2.4 MeV.
[0040] As reflected in FIG. 1A the particle beam source 200
includes a power input 201 for receiving the power required to
drive the particle source.
[0041] FIG. 2A provides details of the exemplary particle beam
source 200 of FIG. 1. As reflected in FIG. 2, the exemplary
particle beam source 200 includes a particle generator 202 for
generating charged particles. In the example, of FIG. 2, the
charged particles may take the form of a negatively charged
hydrogen nucleus (for example, a neutral hydrogen atom with an
added electron). The use of a neutral hydrogen atom with an added
electron is exemplary for purposes of the present discussion and
other charged particles may be used without departing from the
teachings of the present disclosure. It should also be noted that
the use of negatively charged particles is exemplary as well. One
could implement the teachings of the present disclosure using
positively-charged particles, although the references to positive
and negative voltages in the discussion relating to how the
particles are accelerated should be considered reversed when
dealing with positively-charged particles (i.e., references to
negative voltage should be replaced with positive voltage and vice
versa).
[0042] In the example of FIG. 2A, the negatively charged generated
particles from the particle generator 202 are applied to a vacuum
accelerator assembly 204 that includes several individual vacuum
voltage chambers. The vacuum accelerator assembly 204 receives the
negatively charged particles from the particle generator 202 and
accelerates the generated particles to provide a high energy
particle beam at its output. The high energy output beam from the
vacuum accelerator assembly 204 is provided to an electromagnetic
forming and steering assembly 208 that converts the received
particle beam into an output particle beam having desired shape and
directional characteristics.
[0043] FIG. 2B illustrates an exemplary vacuum accelerator assembly
204 that may be used to form the particle beam source 200 of FIG.
2A. In the example of FIG. 2B, the vacuum accelerator assembly 204
is formed from ten individual vacuum voltage chambers 206a-206j.
Each of the vacuum voltage chambers is coupled to a vacuum source
and to a source of electrical power such that the voltage chamber
can be evacuated to provide a vacuum interior and such that a
relatively uniform electrical potential (voltage) level within the
chamber can be established. The vacuum voltage chambers may be
arranged in four groups, a first group comprising chambers
206a-206b, a second group comprising chambers 206c-206d a third
group comprising chambers 206g-206h and a fourth group comprising
chambers 206i and 206j. Chambers 206e-206f may collectively be used
to form a nitrogen stripping chamber as discussed in more detail
below.
[0044] FIG. 2C generally illustrates the way the exemplary particle
beam source 200 may be operated to generate particles having a
first energy level. Referring to the figure, in this mode, during
operation of the assembly 204, the first and second groups of
vacuum voltage chambers (i.e., each of the voltage chambers
206a-206d) is energized such that the voltage potential in these
chambers is positive, with the magnitude of the electrical
potential increasing from chamber 206a to 206d. Because the
particles generated by the particle generator 202 will have a
negative charge, the positive voltage potential within chambers
206a-206d, and the differential in the magnitude of the positive
voltage between chambers 206a-206d will cause the generate
particles to move into and accelerate through chamber 206a towards
chamber 206b, with the particles accelerating as they move through
the identified chambers as the result of the increasing voltage
potential from chamber 206a to 206b. The particles will move into
chamber 206b and be accelerated, in the same manner, towards and
into chamber 206c. The process will be repeated with the particles
continuing to accelerate, and gain energy, as they pass into and
through chamber 206d.
[0045] In the illustrated example of FIG. 2C, during this first
mode of operation, vacuum voltage chambers 206e and 206f are
configured such that they have no net voltage potential. As a
result, the particle moving through these chambers will not be
accelerated but will--in essence--"coast" through the chambers 206e
and 206f as a result of the momentum created by the movement and
acceleration provided by chambers 206a-206d. In the illustrated
example, chambers 206e and 206f, while not maintained at a specific
voltage level, are filled with charged nitrogen gas to form a
nitrogen stripping chamber. This gas will tend to strip off
electrons from the particles traveling through chambers 206e and
206f, thus causing the moving particles to transition from
negatively charged particles to particles having a positive charge.
In the specific example under discussion, the stripping chamber
will strip off the two electrons associated with the negatively
charged hydrogen generated by particle accelerator to provide a
positively charged particle consisting of a single proton.
[0046] In the illustrated example of FIG. 2C, in the operating
mode, the vacuum voltage chambers in the third and fourth groups
(i.e., chambers 206g-206j) are activated such that the voltage
levels within the chambers are negative, with the magnitude of the
voltage levels within the chambers increasing from chamber
206g-206j. As a result of these established voltage levels, the
positively charged particles traveling through chamber 206f will be
attracted into chamber 206g and accelerated through chamber 206g to
chamber 206h where they will be further attracted toward, and
accelerated through, chambers 206i and 206j. Because of the
increasingly negative voltages created within chambers 206g-206j,
the particles passing through the chamber will continue to
accelerate as they pass through the identified chambers to and from
a high energy particle beam at the exit of vacuum accelerator
assembly 204.
[0047] In the example of FIG. 2B, the voltage levels of the
chambers 206a-206j are established such that the energy level of
the particles exiting the particle beam source 200 are at least on
the order of approximately 4.5 MeV.
[0048] FIG. 2D illustrates a second mode of operating the particle
beam source 200 of FIG. 2A may be operated to produce a proton beam
of a second energy level, where the second energy level is less
than the first energy level discussed above.
[0049] The operation reflected by FIG. 2C is like that discussed
above with respect to FIG. 2B except that, in the example of FIG.
2C, only the vacuum voltage chambers in the first and third groups
are activated such that no voltage potential is established within
chambers 206b, 206d, 206h or 206j. As such, the protons traveling
through the illustrated assembly will not be accelerated through
those chambers and the energy level of the traveling protons will
not increase as they pass through the chamber. As a result, the
energy level of the protons emitted by the particle beam source 200
will be at a reduced energy level which, in the example of FIG. 2C
is an energy level of at least about approximately 2.5 MeV and
below the first energy level.
[0050] While a specific exemplary proton generator was described
with respect to FIGS. 2A-2D, it should be accepted that other
particle beam sources may be used in the exemplary system 1000 of
FIG. 1 without departing from the teachings of this disclosure.
Additionally, while the exemplary particle beam source of FIG. 2A
was illustrated and described as using a vacuum accelerator
assembly having only ten voltage chambers, it should be understood
that particle beam sources having fewer or more chambers may be
used to carry out the teachings of this disclosure. Still further,
while the above example describes operation of a particle beam
generator to generate beams comprising particles having either a
first or a second energy level it will be appreciated that the
teachings of this disclosure can be used to provide a particle beam
source where the particles comprising the provided beam can have
multiple energy levels in excess of the two discussed herein and/or
where the energy levels of the particles comprising the provided
beam are well above the first energy level discussed herein, and/or
below the second discussed energy level. For example, embodiments
are envisioned wherein the first energy level exceeds about 10
MeV.
[0051] Referring to FIG. 2A, the particle beam generated by the
vacuum accelerator assembly 204 is provided to an electromagnetic
forming and steering assembly 208 that transforms the received
particle beam into an output beam having desired projection pattern
(i.e., a desired shape) and directional characteristics. In the
example of FIG. 2A, the electromagnetic forming and steering
assembly 208 may take the form of a beam focusing/defocusing
instrument. Such an instrument may, in some embodiments, take the
form of a quadrupole magnetic assembly that may be energized to
provide output beams having at least first and second shaped
characteristics and multiple directional characteristics.
[0052] FIGS. 2E1, 2E2, 2E3 and 2E4 illustrate exemplary first,
second, third, and fourth beam shapes that may be generated using
the exemplary electromagnetic forming and steering assembly 208 of
FIGS. 2A-2D.
[0053] As reflected in FIG. 2E1, the beam provided as an output of
the forming and steering assembly 208 may take the form of a
focused "spot" beam or a beam having a relatively small primary
point of focus. Through proper energization of the beam forming and
steering assembly 208, the spot beam may be directed to a single
point, to various points at different times or, in some
embodiments, to scan across a general area.
[0054] As reflected in FIG. 2E2, the forming and steering assembly
208 can adjust the overall size of the spot beam such that the
general diameter of the beam can be greater than the diameter of
the narrower spot beam reflected in FIG. 2E1. In addition to
providing spot beams of first and second diameters, as reflected in
FIG. 2E2, the forming and steering assembly 208 can also be used to
provide a spot beam that varies, smoothly or in steps, from a
first, relatively narrow spot, to a second, larger-diameter
spot.
[0055] FIG. 2E3 and 2E4 reflect operation of the forming and
steering assembly 208 in an alternate matter to generate a beam
that takes the general form of a ring, with FIG. 2E3 illustrating a
ring having a first inner and first outer diameter, and FIG. 2E4
illustrating a ring having a second inner and second outer
diameter, where the second inner diameter is greater than the first
inner diameter and where the second outer diameter is greater than
the first.
[0056] Although not illustrated in FIGS. 2E1-2E4, embodiments are
envisioned where rings of various inner and outer diameters can be
produced by assembly 208 and/or where rings of variable sizes may
be generated such that the beam can be varied from a spot to rings
of increasing inner and outer diameters until a maximum outer
diameter is reached, down again to a spot through rings of
progressively decreasing inner/outer diameters, and then have the
process repeated again in a cyclic fashion. This variation can be
accomplished by smoothly changing beam shapes or through steps.
During such cyclic operation, the amount of time the system is
maintained at the various shape and directional points can be
varied such that the system, for example, dwells at a spot point
for a first period of time, and then cycles through rings of
various sizes for a second period of time, where the first period
of time is longer than--and potentially multiples of--the second
period of time.
[0057] In addition to providing particle beams of varying shapes
and varying general energy levels, the particle beam source 200 of
the present example can be controlled to provide particle beams of
varying intensity (or current). This can be accomplished by
controlling the operation of the particle generator 202 to generate
fewer or more particles at any given time.
[0058] Referring to FIGS. 1A and 1B, in the exemplary system, the
particle beam generated by the particle beam source 200 is provided
to a Thorium molten salt assembly 300.
[0059] FIGS. 3A-3H2 and 3J1-3J3 illustrate aspects of exemplary
Thorium molten salt assemblies 300 that may be used in connection
with the exemplary system 1000 of FIG. 1.
[0060] Turning first to FIGS. 3A-3D, a first exemplary Thorium
molten salt assembly 300 is illustrated. As reflected in the
figure, the illustrated Thorium molten salt assembly 300 includes a
main body 302 in the form of a large, tub-like structure. The main
body 302 forms a vessel which may contain molten salt including
Thorium. In general, the main body 302 should be formed from a
substance that can withstand the environment that will exist within
and outside of the assembly 300. In particular, the main body 302
should be formed from a material that is generally resistant to the
chemical characteristics of the molten salt fluid that will be
contained within the assembly 300. While a variety of different
materials may be suitably utilized, nickel-based steel alloys, such
as Hastelloy-N, may be used to form the main body 302 and, indeed,
all components in contact with molten salts comprising the various
exemplary molten salt assemblies discussed herein. Other
potentially suitable materials include stainless steels or
Incolloy. Additionally, coatings can optionally be applied to the
identified (and other) materials to enhance their resistance to
corrosion.
[0061] As reflected in FIGS. 3A-3D the bottom of the main body 302
is generally rounded. This rounded bottom shape is believed to be
beneficial in promoting optional fluid circulation within the
assembly 300. The round bottom can also be of benefit in properly
locating the assembly 300 within a shielding structure, as
discussed in more detail below.
[0062] In the example of FIGS. 3A-3D the main body 302 is coupled
by, for example welding to a lower flange element 304. The lower
flange element 304 defines a lower flange surface that, in turn,
defines a plurality of bolt openings (unlabeled in FIGS.
3A-3B).
[0063] An upper lid assembly 306 is coupled to the lower flange
element 304. The outer portions of the upper lid assembly 306
define an upper flange section (not separately labeled) that is
arranged in general alignment with the lower flange element 304.
The upper flange section of the lid assembly 306 defines a
plurality of bolt holes where the bolt holes are preferably of the
same number and sized to align with the bolt openings of the lower
flange element 304.
[0064] While the number of bolt openings can vary, in preferred
embodiments at least eight bolt openings are provided. In the
example of FIGS. 3A-3B both the lower flange element 304 and the
upper flange section of lid 306 defines sixteen bolt openings.
Bolts 308 (only one of which is labeled in FIGS. 3A-3D are used to
couple the lid 306 to the lower flange element 304. The use of
bolts to couple the lid 306 to the lower flange element 304 is
exemplary and other forms of coupling may be used. For example,
screws, clamps and other mechanical assemblies may be use. In
embodiments where ready separation of the lid assembly from the
lower flange element 304 is undesirable, welding may be used. The
use of bolts in FIGS. 3A-3D permits ready attachment and separation
of the lower flange element 304 and the upper flange section of lid
306, simplifying the assembly and disassembly of the exemplary
molten salt assembly 300.
[0065] As illustrated in FIGS. 3A-3D, the bolt openings in the lid
assembly 306 and the lower flange element 304 are such that they
open outside the interior of the main body 302 in which the molten
salt will be located. As such, the bolt openings do not give rise
to any penetrations into the interior of the main body 302.
[0066] Referring to FIG. 3D, which shows a top-view of the lid
assembly 306, it may be seen that in the illustrated exemplary
embodiment (in addition to defining bolt openings 310, only four of
which are labeled in FIG. 3D) the lid assembly defines four
impeller openings 312a-312d that pass from the outside of the lid
assembly 306 into the interior of the main body. The lid 306
further defines two heat exchanger openings 314a and 314b that
provide openings that extend from the exterior of the main body 302
into the interior of the main body 302.
[0067] As best reflected in FIG. 3D, the lid 306 is a two-piece
assembly that includes a generally ring-shaped main section of a
first thickness and an inner disc-element 316 of a second
thickness, where the second thickness is less than the first
thickness. The window element 316 is intended to provide a "window"
into the interior of the main body 302 through which certain types
of particles, specifically at least the particles provided by the
particle beam source 200 (and, potentially, neutrons) can pass. In
the example of FIGS. 3A-3D, the window 316 is formed from a disk of
any suitable material and may take the form of titanium, or
aluminum titanium, or any other suitable material that will pass
the particles provided by the particle beam source 200. The window
element 316 should have a thickness sufficient to pass particle
beams of the type necessary for operation of the systems described
in this disclosure.
[0068] The window element 316 maybe coupled to the ring-shaped
section of lid 306 in any suitable manner. In some embodiments, the
window element may be bolted onto, screwed onto, screwed into or
otherwise mechanically coupled to the ring-shaped section of lid
306. In other embodiments, the window element 316 may be welded to,
brazed to, integrally formed within or otherwise attached to the
ring-shaped section.
[0069] While the window element 316 is illustrated as being
circular in shape in FIG. 3D, it should be understood that the
window element 316 may take the form of other shapes such as, for
example, a square, oval, or pentagon. In still other alternative
embodiments, instead of a single large window element 316, multiple
window elements are provided where the collection of window
elements collectively define multiple passages through which high
energy protons can enter the main body 302.
[0070] As best shown in FIGS. 3A-3C, in the example under
discussion, a plurality of motor-driven impeller pumps 318a-318d
are provided. The general construction of each of the impeller
pumps is shown in FIGS. 3E1-3E2.
[0071] As reflected in FIGS. 3E1-3E2, in the exemplary embodiment
under discussion, each of the impeller pumps 318 includes a
variable speed motor 320 that is coupled to a shaft 330. The
variable speed motor may take the form of any suitable variable
speed motor such as a variable frequency induction motor, a
brushless permanent magnetic motor or a switched reluctance motor.
In the example of FIGS. 3E1-3E3, the variable speed motor 320 takes
the form of a variable frequency driven induction motor. Although
not illustrated, it will be understood that such a motor will
include a rotor and a stator with windings and the windings will be
coupled to a variable frequency drive that can provide power to the
motor 320 in such a manner that the rotational speed of the motor
can be controlled.
[0072] As shown in FIG. 3E3, the motor shaft 330 extends downward
from the motor and is coupled to an impeller element 332.
[0073] In the example under discussion, the pump further includes a
bearing assembly 322 through which the shaft 330 passes. As
described in more detail below, the bearing assembly 322 of each
impeller pump 318 in the example under discussion is positioned
within one of the impeller openings of the lid 306. Because the
impeller shaft has to pass through the top lid, the penetration
should include high temperature seals to prevent the leakage of
materials and gases from the interior of the main body 302 to the
exterior of the body.
[0074] The illustrated impeller pump 318 also include a pump body
324 that defines an upper fluid opening 326 and a lower fluid
opening 328.
[0075] The impeller pump 318 is designed such that, during
operation, activation of the motor 320 will result in rotation of
the shaft 330 and, therefore, rotation of the impeller element 332.
The rotation of impeller element 330 will create a pressure
differential across the inner chamber defined by the pump body 324
such that fluid will tend to be drawn into the upper fluid opening
326, flow through the chamber defined by pump body 324, and out the
lower fluid opening 328. The rotational speed of the motor can be
controlled to vary the pressure drop through the pump body 324 and,
thus, the extent of the fluid flow through the pump.
[0076] Referring to FIG. 3C it may be seen that the molten salt
assembly 300 also includes a tubular member 340 positioned within
the main body 302. The tubular member 340 includes openings at both
its top and bottom ends such that liquid, such as a
Thorium-containing molten salt, can flow into the bottom of the
tubular member 340, up through the tubular member, and out, over
the top of the tubular member 340. As best reflected in FIG. 3C,
the bottom of the tubular member 340 can define a lower ledge
structure.
[0077] In general, the tubular member 340 defines an interior space
within the main body 302 within which, and among, various
structures can be positioned and through which liquid can flow.
[0078] Referring to FIGS. 3B, 3C and 3F, it may be seen that the
tubular member 340 and the impeller pumps 318 are dimensioned such
that the upper fluid opening 326 opening of the pump body 324
includes a portion that extends below the top of the tubular member
340 and the lower fluid opening 328 of the tubular member 340 is
positioned above the bottom of the tubular member 340. As reflected
in the figures, the length of the tubular member 340 and the
impeller pump 318 are such that the bottom end of the tubular
member and the lower fluid opening 328 of the impeller pumps 318
are within the lower portion of the main body 302 such that an
adequate flow path (to the left in the figure) is provided. In the
specific example in the referenced figures, the lower fluid
openings of the impeller pumps are within the lower one-third of
the main body 302. The result of such positioning is that operation
of the impeller pumps 318 will tend to cause fluid to flow up and
out of the tubular member 340, over the top of the tubular member
340 and down through the main body 302 (and partially through the
pump body 324). Thus, operation of the impeller pumps 318a-318d
will tend to cause fluid flow within the main body 302 along the
path generally reflected by the arrows in FIG. 3F.
[0079] As will be appreciated, the fluid flow path depicted in FIG.
3F will exist for each of the four impeller pumps 318a-318d
illustrated in FIGS. 3A-3F. As such, operation of the impeller
pumps will tend to result in a circulating flow of fluid where
fluid flows through a circulation path whereby it initially
circulates into the bottom of the tubular member 340, flows up
through the tubular member 340, then out and over the top of the
tubular member 340, and down the outside of the tubular member 340,
where it circulates back up and into the bottom of the tubular
member and the cycle is repeated.
[0080] In the embodiment of the molten salt assembly 300 previously
described, and in all embodiments of the assembly 300 discussed
herein a Thorium containing molten salt will be held in the main
body 302. While the exact composition of the molten salt within the
main body 302 will vary, embodiments are envisioned where the
molten salt will contain at least a Lithium salt, a Beryllium salt
and a Thorium salt, such that Lithium, Beryllium and Thorium exist
within the molten salt. One suitable salt is a FLiBe salt
containing dissolved Thorium. Other embodiments are envisioned
wherein the molten salt does not include Beryllium but does include
Lithium. One such salt is FLiNaK. In general, the quantity of
molten salt within the main body 302 should be such that the upper
level of the molten salt is over the top of the tubular member 340.
Still further embodiments are possible where the molten salt is a
chloride salt that contains chlorine, as opposed to fluorine.
[0081] FIGS. 3G1 illustrates a cross-section of the main body 302
and includes a dashed line 342 reflecting the general level of
molten salt in the exemplary assembly 300. As reflected in FIG.
3G1, the upper level of the molten salt is both above the upper
surface of the tubular member 340 and below the lower surface of
the lid assembly 306. As such, an open region 346, not including
any molten salt, but capable of containing gases, exists between
the level of the molten salt and the lower surface of the lid 306
(and the lower surface of window element 317 for the interior
region of the illustrated assembly). This open region 346 is
further illustrated by the dark gray areas of FIG. 3G2. This open
region 346 may be used to store gases generated as a result of
fission processes that can occur within the main body 302. In
certain embodiments, the open region 346 can initially be filled
with an inert gas, such as argon, prior to the operation of the
system.
[0082] In the embodiment of FIGS. 3A-3F, impeller pumps 318a-318d
are used to circulate the fluid in the main body 302. Alternate
embodiments are envisioned wherein natural circulation is used to
provide a fluid flow, generally along the path described above with
respect to FIG. 3F. Such an alternate embodiment is depicted in
FIGS. 3J1, 3J2 and 3J3.
[0083] Referring to FIGS. 3J1 and 3J2, it may be noted that the
overall structure of the illustrated exemplary molten salt assembly
300' is like that described above in connection with FIGS. 3A-3F,
with the primary differences being that the main body 302' of the
embodiment of FIGS. 3J1 and 3J2 is taller and narrower than the
main body 302 of the first-described embodiment, the tubular member
340' is longer and narrower than the tubular member 340 in the
first-described embodiment and the helical heat exchanger assembly
500 (discussed in more detail) below is positioned about the upper
two-thirds of the tubular member 340' and not about the lower
one-third of the tubular member 340'. In general, this arrangement
creates a situation whereby the removal of heat through use of the
helical heat exchanger assembly 500 creates conditions where
natural circulation causes the fluid within the main body to flow
along the paths identified by the arrows in FIG. 3G2.
[0084] Advantages of the embodiment reflected in FIGS. 3J1-3J2,
include simplification of the design and construction of the
assembly 1000 through the elimination of the impeller pumps and the
need for equipment to control the pumps; elimination of the need
for impeller openings in the lid coupled to the main body 302',
thus reducing the number of penetrations that must be made into the
main body, and elimination of the need to provide energy for
operation of the motors driving the impeller pumps. The minimal
penetrations required for implementation of this embodiment is
reflected in FIG. 3J3, where only two penetrations 314a' and 314b'
into the main body are provided, one for the inflow of a heat
exchange fluid for the outflow of heat exchange fluid.
[0085] In certain embodiments of the molten salt assemblies 300
described previously one or more solid Thorium fuel rods will be
positioned and located within the interior of the tubular member
340 (or 340'). References herein to a solid Thorium fuel rod are
intended to indicate that the fuel rod contains solid Thorium (as
opposed to Thorium dissolved in a molten salt). As such, a solid
Thorium fuel rod, as that term is used herein, may define internal
openings or chambers.
[0086] In embodiments as described above, Thorium fuel will be
available within the interior of the tubular member 340 (or 340')
both in the form of solid Thorium within the Thorium fuel rod, but
also in the form of dissolved Thorium within the molten salt. FIGS.
4A-4E illustrate one example of a novel Thorium fuel rod 400
constructed in accordance with certain teachings of this
disclosure.
[0087] Referring to FIGS. 4A-4E a Thorium fuel rod 400, is
illustrated that includes an interior Beryllium core element 402
and an outer, solid Thorium-containing fuel element 404. In the
illustrated example, the Thorium containing fuel element 404 is
formed from a solid Thorium-containing material, such as
metallic
[0088] Thorium. Alternative embodiments are envisioned where the
element 404 is formed from a Thorium-containing solid material
(such as Thorium Dioxide) and an outer cladding
[0089] In the example of FIG. 4A-4E, the outer surface of the
Thorium fuel element 404 defines a series of fins that may be
twisted to form a generally spiral-like outer structure.
Alternative embodiments are envisioned wherein the fins on the
Thorium fuel element are straight or generally straight.
[0090] In the example of FIGS. 4A-4E, the Beryllium core element
402 is formed from a generally tubular element of
Beryllium-containing material, such as metallic Beryllium. The
generally tubular element is formed from a structure that defines
an interior cavity 408 that, at any given cross-sectional point,
defines an open cross section roughly in the form of a four-leaf
clover surrounding a central circular opening. In the illustrated
example, the Beryllium core element 402 has a length that is
greater than the length of the solid Thorium fuel element 404 such
that the Beryllium core element 402 extends out from the top of the
Thorium fuel element.
[0091] In one embodiment, the length of the Beryllium core element
402 is such that the solid Thorium fuel element 404 can be
completely submerged within the molten salt while the top of the
Beryllium core element is above the level of the molten salt. In
general, the length of the Beryllium core element 402 extends along
a majority of the length of the solid Thorium element 404, and
preferably along at least 75% of the length of the solid fuel
element 404. Embodiments are envisioned wherein the Beryllium core
element 404 extends along 100% of the length of the solid fuel
element 404.
[0092] The cross-section of the Beryllium core element 402 at a
given exemplary point is roughly reflected in FIG. 4E. As reflected
in FIG. 4E, at any given point along the Beryllium core element
402, four solid Beryllium projections (410a, 410b, 410c and 410d)
project into the interior of the core and define four lobe-shaped
openings 412a, 412b, 412c and 412d and a generally circular central
opening 414.
[0093] The construction of the Beryllium core element 402 is such
that, from the top of the element 402 to the bottom, the relative
position of the solid Beryllium projections 412a, 412b, 412c and
412d change such that they form a general spiral down the interior
of the core element 402. The result of such a construction is that
they define a central cavity 408 having a circular cross-section
that extends from the top of the core element 402 to approximately
the bottom of the element 402 and generally clover-leaf openings
412a-412d that have the characteristics described below. In the
illustrated example, the clover-leaf openings are such that, for
any particular cross-section, there is at least a portion of at
least one of four of the solid projections from a lower cross
section that extend into the openings. This means that particles
passing through the openings 408a-408d at any given cross-sectional
point will always have at least some solid Beryllium beneath the
openings upon which the particles may impinge. In general, the
specific pitch of the spiral and the size of the projections and
lobe-shaped openings will depend on the amount of power to be
generated, the energy of the incident protons, and other
factors.
[0094] As reflected in FIGS. 4A-4D, the length of the Beryllium
core element 402 is greater than the length of the Thorium fuel
element 404 such that the core element 402 extends from the top of
the solid Thorium fuel element 404.
[0095] In at least one embodiment of the present example, the
exemplary embodiment of FIG. 4A-4E the interior void space within
the Beryllium core will be subjected to a vacuum and the void space
of the Beryllium core sealed to maintain a vacuum. The sealing can
be done through any suitable end cap provided that the end cap is
formed of a material through which the particles provided by the
particle beam source 200 can pass. Alternate embodiments are
envisioned wherein the top ends of each Beryllium inner core are
left open and all the ends are coupled to a manifold assembly that
is attached to a vacuum pump to maintain a vacuum within the
interior void space of the Beryllium core.
[0096] In general, each of the Thorium fuel rods 400 is capable of
generating power through fission reaction that can be caused to
occur by directing a beam of energetic particles, such as protons
with an energy level on the order of above 4.2 MeV into the
interior of the Beryllium core. Particles in such a beam may pass
into the void space of the Beryllium core and travel until they
contact a Beryllium nucleus on one of the surfaces extending into
the core. The collision of the high-energy particle (in one
exemplary embodiment a proton) with the Beryllium nucleus can
result in a (p, n) reaction that produces a neutron having an
incident energy level on the order of 1 MeV or greater. One or more
of such generated "fast" neutrons can strike a Thorium nucleus
within the Thorium element 404 and cause a fission reaction in
which the Thorium nucleus undergoes nuclear fission and releases a
significant amount of energy.
[0097] Depending on the desired operating characteristics of the
assembly 1000 one or more of the Thorium fuel rods 400 may be
positioned within the tubular member 340. In certain embodiments,
the Thorium fuel rods to be positioned within the tubular member
340 are positioned between two support elements and the support
elements are configured to rest within the tubular element 340 in
such a manner that the solid Thorium fuel elements 404 in the fuel
rods 400 are submerged in the molten salt, and the top portions of
the Beryllium cores 402 within the fuel rods extend above the level
of the molten salt. In these embodiments, the top positions of the
fuel rods 400 are all positioned such they are under the window
element 316 such that particles from the particle beam provided by
particle beam source 200 can pass through the window 316 and into
the various Beryllium core elements.
[0098] FIGS. 4F1 and 4F2 illustrate an exemplary embodiment in
which a single Thorium fuel rod 400 is positioned within the
tubular member 340. In the illustrated example, as in the other
examples discussed below, the Thorium fuel rod (or rods) 400 are
positioned between an upper support element 430 and a lower support
element 432. FIG. 4F1 illustrates a top-down view, showing where
the Thorium control rod 400 is positioned within the window element
316. FIG. 4F2 provides a generally isometric view indicating the
positioning of the assembly containing the Thorium fuel rod 400
relative to the lid 406. In the isometric view of FIG. 4F2--and the
isometric views of the other Thorium rod structures discussed in
more detail below, the portion of the Beryllium core element 402
that extends out of and above the solid Thorium fuel element 404 is
not illustrated but should be understood to be present.
[0099] FIGS. 4G1 and 4G2, 4H1, 4H2 and 4H3 illustrate alternate
fuel arrangements that include either five Thorium fuel rods (FIGS.
4G1 and 4G2), thirteen Thorium fuel rods (FIGS. 4H1 and 4H2) or
seventeen Thorium fuel rods (FIG. 4H3). As reflected in FIGS. 4G1,
4G2, 4H1 and 4H2, in certain illustrated embodiments the Thorium
fuel rods to be used in the system are combined in a single solid
Modular Thorium fuel package that includes the solid Thorium fuel
rods (or rod) positioned between two support elements. The use of
such a solid Modular Thorium fuel package can permit efficient
refurbishing of the system 1000 described herein for subsequent
operations. In addition, the use of a Modular Thorium fuel package
as disclosed herein also permits the construction of systems of
different power levels through the use of one fuel package in place
of another.
[0100] As briefly discussed in the previously illustrated
embodiments, the Beryllium core elements are used to provide solid
targets upon which high energy protons can impinge to generate high
energy (for example over 0.7 MeV) neutrons that can strike Thorium
to induce a fission reaction within the Thorium nucleus, generating
additional high energy neutrons and energy. FIGS. 4G1 and 4G2
illustrate an alternative solid Modular Thorium fuel package in
which a different approach is used to generate high energy neutrons
for the fast fission of Thorium.
[0101] Referring to FIGS. 4J1 and 4J2, a solid Thorium fuel
assembly is illustrated that includes four solid Thorium rods
(FIGS. 460a-460d) surrounding a single, central solid Beryllium rod
462. In the illustrated embodiment, the central solid Beryllium rod
462 is used as a target in which the high energy particle beam from
the particle beam source 200 is projected. When such high energy
particles strike the Beryllium rod 462, high energy (fast) neutrons
can be generated which can exit the Beryllium rod and impact upon
Thorium in the solid Thorium rods (460a-460d) to cause fast Thorium
fission reaction.
[0102] In the embodiments of FIGS. 4J1 and 4J2 the central
Beryllium rod 462 is solid. As such, the particles impinging on the
rod from the particle beam source 200 may not penetrate the lower
portions of the Beryllium rod 462. To promote such penetration and
utilization of the entirety of the Beryllium rod to generate fast
neutrons, a Beryllium rod in the general form of the one described
above in connection with FIGS. 4D and 4E may be substituted for the
solid rod 462. In the embodiments discussed above in connection
with FIGS. 4A-4H3 and 4J1-4J2 the Beryllium within the Beryllium
rods may be in the form of solid Beryllium. Alternative embodiments
are envisioned wherein the Beryllium within the Beryllium rods
takes alternative forms, such as a Beryllium-containing salt (e.g.,
FLiBe). In such embodiments, the Beryllium-containing rods would
comprise a vessel capable of containing a molten
Beryllium-containing salt.
[0103] Referring to FIGS. 1A and 1B and 3H1 and 3H2 a primary heat
exchange assembly 500 is shown as extending around the central
tubular member 312. The illustrated exemplary primary heat
exchanger includes an input pipe 502 and an output pipe 504. The
input pipe 502 is coupled to an input manifold 506 (illustrated in
FIGS. 3H1-3H2) and the output pipe 504 is coupled to an output
manifold 508. Notably, the lengths of the input and output pipes
are sufficiently long so as to pass through the top level of the
Thorium-containing molten salt, into the gaseous head maintained
above the molten salt and potentially through the top lid of the
main body.
[0104] As reflected in the exemplary figures, a plurality of
helically formed coiled pipes 510, ten in the illustrated example,
have one end coupled to the input manifold 506 and another end
coupled to the output manifold 508. As reflected in the figures,
each of the helical pipes 510 winds downwardly around and back up
the tubular member 12 from the input manifold to the output
manifold 508. The illustrated number of helically formed coiled
pipes is exemplary only and a different number of pipes could be
used without departing from the teachings of the present
disclosure. In the embodiment of FIGS. 1A-1B the primary heat
exchange assembly includes a non-Thorium containing molten salt
within the pipes 510 and input and output manifolds 506 and 508. As
described in more detail below, this non-Thorium containing molten
salt is circulated through the primary heat exchanger to remove
heat from the Thorium molten salt assembly 300. Pumps (not
illustrated) may be used to circulate the non-Thorium containing
molten salt.
[0105] Select details of an exemplary primary heat exchange
assembly 500 are shown in FIGS. 3H1 and 3H2. FIG. 3H2 reflects the
construction of an exemplary manifold 506. The illustrated manifold
construction may be used for both the input manifold and the output
manifold. Referring to FIGS. 3H1 in the illustrated example, the
manifold includes a box-like main manifold base 560 that defines a
single input (or output) opening 562 of a first diameter at the top
of the base 560 and a plurality of output (or input) openings 564
of a second diameter at the bottom of the base, only two of which
are labeled in the figure. In this embodiment, the second diameter
is less than the first diameter. In the illustrated example, the
input 562 is axially offset from each of the plurality of openings
564, such that there is no straight flow path through the first
opening 562 and any of the second openings 564. In the illustrated
example, there are twelve (12) openings 562. Each of the second
openings is coupled to a heat exchange coiled pipe 566.
[0106] Use of the exemplary manifold described above permits the
use of a plurality of lesser-diameter heat exchange coils (twelve
in the example) within the main body 502, while requiring only two
penetrations through the main body 502.
[0107] In the exemplary embodiment discussed herein, heat generated
within the main body 502 will be transferred to the molten salt
flowing through the primary heat exchange assembly 500. In the
illustrated example, that heat is transferred from the primary heat
assembly 500 to a secondary heat assembly 512.
[0108] Details of the secondary heat exchanger assembly 512 are
shown in FIG. 1B. As reflected in FIG. 1B a secondary heat exchange
path 516 is provided and arranged to absorb heat from the primary
heat exchange coil. In the example of FIG. 1B, a vapor-forming
liquid--such as water or carbon dioxide--is contained within the
secondary heat exchange path (or coil) 516 and the piping attached
to the secondary heat exchanged coil. A condenser 518 is also
provided in the illustrated system as is piping (not labeled) that
can transport liquid from the condenser 518 to the input of the
secondary heat exchange coil and steam from the output of the
secondary heat exchange coil to the input of the condenser.
[0109] Not illustrated in FIGS. 1A or 1B are pumps that can be used
to circulate non-Thorium containing molten salt through the primary
heat exchange loop and vapor-producing liquid (such as water or
carbon dioxide) through the secondary heat exchange loop.
[0110] In the example of FIG. 1, the energy transfer assembly 500
is used to transfer energy from the Thorium molten salt assembly
300 to a power generator assembly 600. High level details of such a
system may also be found in FIGS. 1A-1B which reflect the
application of the vapor generated by the heat exchange tank 512 to
a turbine assembly 602 which, in turn, is coupled to an electric
generator 604. In accordance with the general operation of
turbine-driven electrical generators, the vapor produced by the
energy transfer that occurs within the heat exchange tank 512 is
used to drive/turn turbine 602 which turns the rotor of the
electrical generator 604, producing electrical power at the output
606 of the electrical generator 604. In the illustrated system the
output 606 of the electrical generator 604 is provided to a
distribution element which distributes the generated electric power
such that the majority of the generated power is provided to a main
power output 608 and a portion of the generated power is provided
to the power input of the proton generator 201 to drive the
particle beam source 200.
[0111] Because the operating of the system 100 of FIGS. 1A and 1B
can generate nuclear particles and radiation emission, appropriate
shielding 700 is provided to block the transmission of undesired
particles and waves. FIG. 5 illustrates one exemplary way this
shielding may be provided. In the illustrated example of FIG. 5,
many of the components of the system 1000 are placed in a
containment system 700. In the exemplary embodiment, the
containment system 700 comprises a first containment structure 702
in which the particle generator 202 and the vacuum accelerator
assembly 204 are located. Vacuum tubes (unlabeled) are coupled to
the output of the vacuum accelerator assembly 204 and couple the
output of the vacuum accelerator 204 to the forming and steering
assembly 208, which is positioned in second containment structure
704. The molten salt assembly 300 is partially placed within the
ground under the second containment structure 704 such that the lid
of the molten salt assembly is accessible above ground. A third
containment structure 708 is provided below the molten salt
assembly 300. The space 706 between the molten salt assembly 300
and the third containment structure 708 may be filled with any
suitable material, such as soil, borated material, concrete, or any
other suitable material or blend of materials. Depending on the
particular application of the system 1000, and the extent to which
safety requirements dictate, the containment units 702, and 704 may
take the form of a simple metallic structure (if the earth, rock or
ground structure is capable of providing the desired shielding) or
a structure intended to block the transmission of radiation (e.g.,
lead-walls or a lead-brick structure). The structure 708 should be
formed of a material sufficient to contain molten salt in the
possibility that there is damage to the molten salt assembly.
Alternate embodiments are envisioned wherein the containment unit
700 comprises a structure having an internal dry core area into
which the components of system 1000 to be shielded are placed and
an external structure capable of holding water (or a water/chemical
mix (e.g., borated water) which acts as a shielding material. In
any or all the various embodiments of the containment unit 700 a
surface layer of shielding material 702 (e.g., a lead blanket) may
be used.
[0112] In operation, at a very high level, the system illustrated
in FIGS. 1A and 1B operates by powering the particle beam source
200 to generate a proton beam that is applied to the Thorium molten
salt assembly 300. One or more of the protons within the proton
beam may impact upon one or more of the atoms within the Thorium
molten salt assembly 300 to either: (a) produce neutrons or (b)
result in a nuclear fission reaction, which will generate heat and
further neutrons. These generated neutrons may, in turn, impact and
interact with other atoms within the Thorium molten salt assembly
300 to generate additional heat. The generated heat may be removed
through operation of the primary and secondary heat exchange
systems, and the removed energy may be converted to electric energy
through use of the electric generation system 600, described
above.
[0113] The exemplary system 1000 of FIGS. 1A and 1B may be arranged
to permit operation of the system in one of several alternative
operating modes.
[0114] In one operating mode, the proton beam provided by the
particle beam source 200 is shaped and aimed such that the proton
beam provided by the generator is directed through the window
element 316 primarily into the Thorium containing molten salt
within the tubular member 302 without a substantial number of the
protons (or any) impinging upon the Beryllium cores of the Thorium
fuel rods 400 positioned within the tubular member 340.
[0115] In this operating mode, one (or more) of the protons from
the proton beam from generator 200 may impact one (or more) of the
atoms within the Thorium containing molten salt. For example, one
or more of the protons from the proton beam may impact with a
Lithium nucleus forming part of the molten salt. This interaction
of the proton with the Lithium nucleus can cause a (p, n) reaction
under which the Lithium nucleus absorbs the incident proton and
emits a neutron. The neutrons emitted by such proton-Lithium
reactions may be of varying energy levels, the greatest number of
neutrons resulting from several such reactions would be at an
energy level of between 0.1 and 0.7 MeV. As another example, one or
more of the protons from the proton beam may impact with a
Beryllium nucleus forming part of the molten salt to cause a (p, n)
reaction in which the Beryllium nucleus may absorb the incident
proton and produce a neutron at a particular energy level. The
neutrons emitted by such proton-Lithium reactions may be of varying
energy levels, the greatest number of neutrons resulting from
several such reactions would be at an energy level of between 0.7
MeV and just over 1.0 MeV. Notably, the peak energy level of the
neutrons emitted by the described proton-Beryllium (p, n) reaction
will be greater than those emitted as a result of the described
proton-Lithium (p, n) reaction.
[0116] In a second operating mode, the proton beam provided by the
particle beam source 200 may be shaped and aimed such that all or a
substantial portion of the proton beam is directed through the
window assembly in such a manner that a substantial number of the
protons forming the proton beam are directed to one or more of the
Beryllium cores of the Thorium fuel rods within the tubular member
340. This may be accomplished by forming the proton beam into a
generally narrow beam shape and directing the narrow beam to the
Beryllium core of the central Thorium fuel rod. This may also be
accomplished by forming the proton beam into a ring and directing
the ring such that it covers either the first group of Thorium fuel
rods or the second group of fuel rods. Alternatively, the beam may
be formed such that it transitions from a beam directed to the
central Thorium fuel rod, to a first ring directed to the first
group of fuel rods to a second ring directed to the second group of
fuel rods. In general, forming and aiming the proton beam as
described in connection with the second operating mode will tend to
cause protons within the proton beam to strike Beryllium, thus
generating neutrons through the process described above.
[0117] In the embodiment of FIGS. 1A and 1B the average energy
levels of the protons within the proton beam generated by the
particle beam source 200 may be varied, depending on the operating
mode of the system to prefer proton-Lithium interactions, thus
producing neutrons with average energies below 0.7 MeV or to prefer
proton-Beryllium interactions, this producing neutrons with average
energies above 0.7 MeV.
[0118] For example, when the system is operated in accordance with
the first operating mode, the energy level of the protons provided
by the proton generator may be set to be on the order of at least
approximately 2.4 MeV and about 3.0 MeV. The size and form of the
proton beam, along with the energy level of the proton beam and the
fact that it is directed into the Thorium containing molten salt,
are such that operation of the system in the first operating mode
will tend to result in proton production of neutrons of an energy
level on the order of between 0.1 MeV and just over 1.0 MeV with
the peak energy level of the produced neutrons being on the order
of about 0.7 MeV.
[0119] In the same example, using the system described above in
connection with FIGS. 2A-2D, when the system is operated in
accordance with the second operating mode, the particle beam source
200 may be operated to produce a beam of protons where the protons
forming the beam have energy levels on the order of 4.5 MeV. The
size and form of the proton beam, along with the energy level of
the proton beam and the fact that it is directed into the Thorium
containing molten salt, are such that operation of the system in
the first operating mode will tend result in proton production of
neutrons of an energy level on the order of 0.1 MeV-1.2 MeV, with
the majority of the produced neutrons having energy levels on the
order of between 1.0-1.1 MeV.
[0120] The likelihood of the particles from the particle beam 200
interacting with one or more of the atoms within the main body 302
will vary depending on a large number of factors including, but not
limited to: the energy level of the particle provided by the
accelerator, the particular nucleus involved in the potential
interaction, and the other atoms within the body 302. The system
1000 takes advantage of some of these variables, and of the
different types of reactions that can occur within the main body
302 to provide a system that can be operated in various modes, to
provide various output characteristics.
[0121] To understand the various modes in which the exemplary
system of the present disclosure may be operated, it is helpful to
understand some of the operations that can occur within the body
302.
[0122] As briefly discussed above, in the system of FIGS. 1A and
1B, once neutrons are created within the main body 302 (e.g., by a
high energy proton provided by the proton beam colliding with a
Lithium nucleus or a Beryllium nucleus within the molten salt or as
a result of a fission reaction occurring within the main body and
producing resultant neutrons) some of the neutrons within the main
body 302 may collide with a Thorium nucleus in the molten salt
solution and cause a nuclear reaction. In the illustrated system,
the nuclear reaction caused by the described collision can be one
of at least two different types of reactions. In one type of
nuclear reaction, referred to as a "fission" reaction, the nucleus
of the involved Thorium atom will split into, typically two,
smaller nuclei. Such a fission reaction will release a very large
amount of energy and one or more neutrons. The energy released by
the fission reaction will tend to increase the amount of energy
stored in the molten salt within assembly 300 as heat. One or more
of the neutrons released by such fission reaction may interact a
Thorium nucleus within the molten salt fuel to cause further
Thorium fission reactions.
[0123] In a second type of nuclear reaction, known as "neutron
capture" (or "neutron absorption") the nucleus of the involved
Thorium nucleus will absorb the involved neutron to form an isotope
of Thorium, namely Thorium-233 (.sup.233TH). Thorium-233 is an
unstable isotope that will decay to Protactenium-233. The decay of
Thorium-233 to Protactinium occurs relatively quickly as the
half-life of Thorium-233 is about 22 minutes. Protactenium-233 is
an unstable element that will tend to decay to Uranium-233, with
the half-life of Protactinium-233 being approximately 27 days.
[0124] Uranium-233 is fissile material. As such, whenever
Uranium-233 exists within the molten salt and neutrons are
available--either from the particle beam source 200 or from the
fission of other atoms within the molten salt--there is the
potential that a neutron can strike a Uranium-233 nucleus causing a
fission reaction. The fission reaction will produce heat. As with
fission of the Thorium nucleus, fission of a Uranium-233 will
result in the release of substantial energy and several neutrons,
those neutrons may, in turn, interact with a Uranium-233 nucleus
within the molten salt to produce a secondary Uranium-233 fission
reaction, with a Thorium-232 nucleus to produce a Thorium-233
nucleus, or with other materials within the molten salt assembly
300. Some of the neutrons may pass through and escape the molten
salt assembly.
[0125] Once started and put into operation, the illustrated
embodiment of FIGS. 1A and 1B can be self-sustaining in the sense
that it can operate to provide usable energy without the addition
of any other external power or energy as long as the energy
generated by the system is sufficient to provide the power needed
to drive and operate the particle beam source 200.
[0126] Once the embodiment of FIGS. 1A and 1B begins to operate,
the constituent components comprising the molten salt solution will
change over time. At a high level, in certain embodiments, the
composition of the molten salt will initially include no, or
negligible, Protactinium and no, or negligible, Uranium. For
purposes of this disclosure a negligible amount of an element is
intended to refer to a substantially non-detectable amount of an
element that exists in the absence of any intentional inclusion or
addition of the element to the material. Alternate embodiments are
envisioned wherein the molten salt could initially contain at least
some Uranium.
[0127] FIG. 6 provides a very crude, approximated, generalized
relative indication of the amount of Thorium-232 and Uranium-233
that can exist for the system of FIG. 1 over time if it assumed
that the neutron source provides a relatively constant supply of
neutrons.
[0128] As reflected in FIG. 6, at a time T.sub.0, before the
application of any neutrons to the system, the quantity of Thorium
in the molten salt will be at its maximum level. As neutrons begin
to be applied to the system, some of the neutrons will interact
with the Thorium-233 causing one or more of the nuclear reactions
discussed above. These nuclear reactions will cause the quantity of
Thorium in the molten salt to decrease over time, as reflected by
the line .sup.232Th.
[0129] As also reflected in FIG. 6, by the time T.sub.1, some of
the Thorium that were subjected to a nuclear capture reaction will
have converted to Protactinium-233 and some of those
Protactinium-233 would have decayed to Uranium-233. As such, the
number of Uranium-233 in the molten salt will begin to increase
over time starting at time T.sub.1.
[0130] It should be appreciated that the representation in FIG. 6
is intended to be a very crude approximation of the relative number
of Thorium-232 and Uranium-233 in the molten salt and that the
actual shape of the represented curves will not necessarily be in
line with the specific curve characteristics illustrated in FIG. 6
(and can potentially be controlled as described below).
[0131] As those of ordinary skill will appreciate, the likelihood
of a nuclear reaction occurring when a specific nucleus is
bombarded with a beam of particles having a specific incident
energy level, is sometimes described by a concept known as the
nuclear cross-section. In general, a nuclear cross-section is a
quantity that expresses the extent to which neutrons interact with
particles of a given energy level. Nuclear cross-section
information may be obtained through consultation of JANIS (the Java
based Nuclear data Information System) provided by the Nuclear
Energy Agency and accessible at https://www.oecd-nea.org/janis/
[0132] FIGS. 7A-7D provide JANIS-generated graph reflecting the
cross-sections of various isotopes that may exist within the molten
salt assembly 300 of FIGS. 1A-1B.
[0133] Referring first to FIG. 7A, data reflecting the
cross-section of Thorium-232 as a function of the incident energy
is illustrated for both the absorption reaction, reflected by line
2, and for the fission reaction, reflected by line 4. Also
illustrated in FIG. 7A are the fission 6 and absorption 8
cross-sections for Uranium-233 as a function of incident energy. As
the graph indicates, for Thorium-232 and Uranium-233, the
cross-sections for the absorption and fission reactions vary as a
function of incident energy in such a manner that the cross-section
values may be considered to lie, for any incident energy level,
within one of four regions.
[0134] FIG. 7B illustrates the cross-sectional information of FIG.
3A divided into four regions. In the first region, designated by
Roman numeral I, the absorption cross-section of Thorium-232 is
comparatively large relative to the negligible fission cross
section and decreases in a relatively smooth manner with respect to
changes in the incident energy level. In that same region, the
fission and absorption cross-sections of Uranium-233 exceed the
absorption cross-section of Thorium-232. In the example of FIG. 3A,
Region I extends from neutron energy levels of roughly
1.times.10.sup.-11 to roughly 1.times.10.sup.-6 mega electron volts
(MeV).
[0135] Within the second region, designated by Roman numeral II,
the absorption and fission cross-sections of Thorium-233 and
Uranium-233 vary substantially in a resonate-like manner with
changes in the incident energy level. Over this region there are
specific energy levels where the absorption cross-section of
Thorium-232 exceeds both the fission and absorption cross-sections
of Uranium-233. It may be further noted that, over this region the
absorption cross-section of Thorium-232 reaches its maximum value.
In the example of FIG. 3A, Region II extends from neutron levels of
roughly 1.times.10.sup.-6 to roughly 0.007 MeV.
[0136] Within the third region, designated by Roman numeral III,
the absorption cross-section of Thorium-232 continues to remain
comparatively large relative to the negligible fission
cross-section of Thorium-232. Over that same region, the fission
cross-section of Uranium-233 exceeds both the absorption
cross-section of Thorium-232 and the absorption cross-section of
Uranium-233. In the example of FIG. 3A, Region III extends from
neutron levels of roughly 0.07 MeV to roughly 0.8 MeV.
[0137] Finally, within the fourth region, designated by Roman
numeral IV, the fission cross-section of Thorium-233 is
comparatively large relative to its absorption cross section, and
both the fission and absorption cross-sections of Thorium-232 vary
in a roughly smooth manner with variations in the incident energy
level. Over this same region, the fission cross-section of
Uranium-233 exceeds the fission cross-section of Thorium-233 and
the absorption cross-section of Uranium-233.
[0138] The system of FIGS. 1A and 1B takes advantage of the
different cross-sections of the various atoms that will exist
within the Thorium molten salt assembly 300 to implement a novel
operational and control scheme wherein the incident energy level of
the particles provided by the particle beam source 200 are varied
over time to adjust the operating state of the molten salt system
such that the energy provided by the system is predominantly
generated by fission of Thorium-232 at certain times, predominantly
by fission of Uranium-233 at other times, and--potentially--fission
of both Thorium-232 and Uranium-233 at other times. Examples of how
such a novel operating method may be implemented are generally
reflected in FIGS. 7A-7E.
[0139] At an initial time, the system of FIGS. 1A and 1B is
operated such that the incident energy level of the neutrons
provided by particle beam source causes operation of the system in
Region IV. This operating region is highlighted in FIG. 7C. This
will be accomplished by controlling the energy level of the
particles provided by the particle beam source 200 such that they
are at a sufficiently high level that interaction between such
particles and the Beryllium within the molten salt can result in
the generation of neutrons having energy levels within the level of
the neutrons within Region IV (i.e., over about 0.7 MeV). During
this period of operation, given the small quantity of Uranium-233
in the molten salt assembly 300, the energy generated by the system
1000 will be predominantly generated through fission of
Thorium-232. However, as reflected in FIG. 7C, such operation will
also result in a non-trivial number of absorption reactions
involving Thorium-232, which will ultimately result in the
formation and buildup of Uranium-233 in the system 300.
[0140] As the number of Uranium-233 atoms in the system increases,
a point will be reached where the level of Uranium-233 is such that
fission of Uranium-233 would be enough to provide the desired
output power. At that point, the system of FIGS. 1A and 1B1 can
transition to operate in Region II, by adjusting the incident
energy level of the provided proton beam to a level where it will
tend to cause interactions between the incident protons and the
Lithium within the molten salt assembly such that neutrons having
energy levels within Region III are generated by proton-Lithium (p,
n) reactions (i.e., neutrons with energy levels between about
1.times.10.sup.-6 to 0.007 MeV). Operation in this region, provides
neutrons wherein fission of Uranium-233 is possible, but the
fission of Thorium-232 as the result of neutrons generated as a
result of bombardment of particles from the particle beam source
200 is negligible. In that same region, the neutrons within the
molten salt assembly 300 will--in addition to causing fission
reactions of Uranium-233, also cause absorption reactions involving
Thorium-232, thus providing a source of Uranium-233 for sustained
operation. The system can then operate in Region III for a
sustained period of time, providing the desired power output until
the number of Uranium-233 atoms in the system is inadequate to
support the desired power output, or until other conditions warrant
a change in the operation of the system or system shut down.
Operation in this Region is reflected by the highlighted portion on
FIG. 7D.
[0141] FIGS. 8A-8H illustrated examples of how the particle beam
from the particle source 200 may be directed, shaped and controlled
to operate the exemplary systems described herein within the
various Regions discussed above in connection with FIGS. 7A-7D.
[0142] As described above, in the exemplary systems under
discussion particle beam source 200 may be used to generate
particles (such as protons) having incident energy levels of above
4.5 MeV when the generation of neutrons having energy levels of
above 0.7 MeV through a (p, n) reaction of the incident particles
and Beryllium, and the direct fission of Thorium, is desired.
[0143] FIG. 8A, illustrates an example of system 1000, from a
top-down perspective, that uses five Thorium fuel rods where of the
Thorium fuel rods includes a Beryllium core generally as described
above in connection with FIGS. 4A-4D. In the example of FIG. 8A,
the proton beam provided by the particle beam source 200 is a solid
beam spot concentrated on the Beryllium core of the central Thorium
fuel rod. As such the incident high energy protons will potentially
collide and interact with Beryllium within the Beryllium core,
producing a (p, n) reaction that results in the generation of
relatively high-energy (sometimes referred to as "fast" neutrons).
These generated "fast" neutrons can then interact with a Thorium
nucleus in the solid Thorium fuel element surrounding the Beryllium
core to cause a Thorium fission reaction to occur which, in turn,
will generate more fast neutrons that can cause further Thorium
fissions to occur.
[0144] FIG. 8B illustrates a similar situation, but this time with
the high energy proton beam from the proton beam source 200 being
directed to the Beryllium core of the Thorium fuel rod at the top
of the image. As will be appreciated, using the approach of FIGS.
8A and 8B, a beam spot of particles of the appropriate type and
energy level (e.g., protons with energy levels at or above about
4.5 MeV) provided by the proton beam source 200 and the proton beam
may be directed to the Beryllium cores of each of the Thorium fuel
rods in the system individually. Thus, by applying the beam for a
limited period to each of the Beryllium cores, a supply of fast
neutrons can be provided for each of the solid Thorium fuel
elements to maintain at least some level of Thorium fission within
the system. This energy released by such Thorium fissions can be
used to operate the system.
[0145] FIG. 8C reflects an alternate way the system 1000 can be
operated to provide fast neutrons and to produce Thorium fissions.
In the example of FIG. 8C, the high energy particle beam from the
particle beam source 200 is focused at a spot within the molten
salt within the molten salt assembly 300. Because at least some of
the particles from the beam will have energy levels in excess of
4.5 MeV, the particles can strike a Beryllium within the molten
salt, thus causing a (p, n) reaction and producing a fast neutron
that can, in turn strike a Thorium atom within the molten salt or
within a solid Thorium fuel element (if present) to cause a Thorium
fission reaction.
[0146] FIGS. 8D and 8E illustrate still other alternate approaches
for producing fast neutrons and inducing Thorium fission reactions.
In these examples, the beam size of the high energy particle beam
from the particle beam source 200 is adjusted such that some of the
particles comprising the high energy beam will impinge on both the
Beryllium core of one or more Thorium fuel rods (thus producing
fast neutrons and inducing Thorium fissions as generally described
in connection with FIGS. 8A and 8B) and others may impinge upon
Beryllium atoms within the molten salt in the assembly 300 (thus
inducing the generation of fast neutrons and Thorium fission as
described above in connection with FIG. 8C).
[0147] Still further alternate embodiments are envisioned wherein
the high energy particle beam provided by the particle beam source
200 is "strobed" from a small diameter beam spot (as generally
illustrated in FIG. 8A) to a larger diameter beam spot (as
generally illustrated in FIG. 8E) to vary the manner in which fast
neutrons are generated.
[0148] FIGS. 8F-8H illustrate yet another alternate mode of
generating fast neutrons. In this mode, the particle beam from the
particle beam source 200 is configured to a have a ring shape and
the dimension and direction of the provided ring is varied to
impinge upon the Beryllium cores of the Thorium fuel rods within
the system and/or the molten salt within the assembly 300.
[0149] It should be noted that, while the above discussion focused
on the manner in which fast neutrons may be generated and the fast
fission of Thorium induced, operation of the system as described
above will also result in a number of different nuclear reactions
including the generation of neutrons having lower energy levels
(sometimes referred to as "thermal" neutrons) and the fission of
any fissionable materials (Uranium-233 for example) that may exist
within the assembly. This is because the neutrons generated within
the assembly (either through reactions involving a particle from
the particle beam source 200 or as the result of fission reactions
within the assembly) will be of various energy levels, such
that--while proton-Beryllium (p, n) reactions, proton-Lithium (p,
n) reactions (generating neutrons with lower, potentially thermal,
energy levels) will be occurring, as will fission reactions of
Thorium and, likely, fission reactions of Uranium-233 (if present).
Absorption reactions will also be occurring, as will non-reactions
where some of the generated neutrons simply escape the assembly
without producing any nuclear reactions within the assembly.
Moreover, neutrons generated with "fast" energy levels will tend to
have their energy levels reduced as they pass through the materials
and elements within the assembly 300 (such as the molten salt) such
that they will become thermal neutrons that can be involved in a
Uranium-233 fission operation or a Thorium-232 absorption
operation.
[0150] Operation of the system as described above, however, to
direct high energy particles (specifically protons) at energy
levels sufficient to produce a Beryllium (p, n) reaction will tend
to promote the generation of fast neutrons and the direct fission
of Thorium within the assembly 300.
[0151] FIGS. 8A-8H (and primarily FIGS. 8C-8E) also illustrate how
the exemplary systems described herein may be operated to promote
the generation of thermal neutrons and Uranium-233 fission
reactions. By operating the particle beam source 200 to provide
particles (such as protons) with energy levels of between about 2.5
MeV and 4.5 MeV, a situation may be created wherein proton-Lithium
(p, n) reactions are promoted. These reactions will tend to produce
neutrons having an energy level below the fast neutrons generated
by a Beryllium (p, n) reactions.
[0152] These neutrons will typically be at a level below that
require for Thorium fission, but at a level where they can be
involved in both a fission reaction involving a Uranium-233
reaction, or an absorption reaction in which Thorium-232 is
ultimately converted into Uranium-233. Thus, by operating the
system 1000 in this manner, Uranium-233 fissions may be promoted.
Again, it should be noted however that, because any fission
reactions involving of Uranium-233 or Thorium-232 that occurs
during a time when the lower energy particles (such as protons)
from the particle beam source 200 are provided to the assembly 300
will produce fast neutrons that can result in a fission reaction
involving Thorium-232, such that fission reactions involving
Thorium-232 can occur within the assembly 300 alongside fission
reactions of Uranium-233.
[0153] Considering the above, it should be clear that the novel
system 100 described herein can, by adjustment of the energy level
of the particles provided by the particle beam source 200, and by
controlling the direction and shape of the provided particle beam,
be operated in manner to promote: (i) generation of fast neutrons
and the direct fission of Thorium (when high energy particles (such
as protons with energy levels above 0.7 MeV) are provided) and (ii)
generation of thermal neutrons with energy levels below 0.7 MeV and
the fission of Uranium-233.
[0154] FIG. 9A illustrates one exemplary method of operating a
system 1000 constructed in accordance with the teachings of the
present disclosure.
[0155] Over a first initial time period 902, the system will be
operated from an external power source (such as a diesel generator)
that will provide the input power to the particle source 200. Over
this time period, the system 1000 can be operated to promote the
generation of fast neutrons and the direct fission of Thorium
through the generation of a high energy particle beam and the
direction of that particle beam to the Beryllium cores of any
Thorium fuel assemblies within the system 1000.
[0156] Over this time period, the output energy level of the system
can be monitored at a step 904. Once it is determined that the
energy being produced by the system is adequate to provide power
necessary to power the particle beam source 200, the external power
source can be removed, and the system can begin to operate without
the addition of any external power.
[0157] After the system begins to operate without the provision of
external power, it can continue to operate in accordance with
Region IV, described above, where direct fission of Thorium is
promoted and used to provide a desired level of energy output. This
is reflected by operating step 906. As described above, over this
period, Uranium-233 will begin to be produced within the
assembly.
[0158] At step 908, the level of Uranium-233 in the assembly can be
monitored and, when it is determined that the quantity of
Uranium-233 in the assembly is sufficient to support the desired
energy level output through fission of Uranium-233, the operation
of the particle beam source 200 can be adjusted to provide
particles (such as protons) of a lower energy level to promote
Uranium-233 fission reactions in a Region II operation. Notably,
over this region, Uranium-233 will continue to be produced as the
result of the Thorium-232 absorption reaction occurring within the
system. Operation in this mode is reflected by step 910.
[0159] It is anticipated that the systems 1000 described herein can
be operated as described above for Step 910 for most of its
operating time, for example over a period of between 5-10
years.
[0160] Of note, in embodiments where the molten salt does not
include Beryllium (for example when the molten salt is FLiNaK, the
generation of fast neutrons through use of the particle beam source
200 will be through bombardment of the Beryllium cores within the
Thorium fuel rods.
[0161] In addition to producing desired energy (and generating
Uranium-233 for later use) operation of the system 1000 in
accordance with a Region IV moderation can beneficially reduce (or
"burn up") undesirable waste elements that could otherwise build up
within the assembly 300.
[0162] In general, nuclear fission reactions typically result in
the production of by-products generally known as fission products.
Certain fission reactions, such as the fission of Uranium-233 can
result in the production of fission products in the form of
actinides, including trans-uranium (TRU) actinides, and other
long-lived fission products. In general, such by-products are
undesirable because they typically emit relatively high amounts of
radiation and have relatively long-half-lives. The handling,
disposing and processing of such TRUs and long-lived fission
products is subject to various regulations and safe-handling
precautions that must be followed when dealing with such
materials.
[0163] Many TRU's and long-lived fission products can be broken
down into elements and isotopes that are less radioactive and/or
have substantially shorter half-lifes such that they are safer to
handle than the original fission products. Such TRUs and long-lived
fission products can be broken down though interactions with
neutrons having certain incident energy levels, typically those on
the order of the "fast" neutrons, whose generation can be promoted
through operation of the system as described above. Thus, operation
of the system in a manner where generation of "fast" neutrons is
promoted to reduce the amount of undesirable waste in the
system.
[0164] The exemplary system 1000 described above may be operated in
various ways to reduce the amount of undesirable waste in the
system. One exemplary operation is reflected in FIG. 9B. In this
operational mode, the system can be operated as described above in
connection with FIG. 9A for most of its operating life. This
operation is reflected at Step 912. Towards the end of its
operating cycle, however, the system 1000 can be transitioned to
operate in the manner described above, where the generation of fast
neutrons is promoted. This is reflected in Step 914. The system
1000 could then be operated at this Step 910 until the desired
reduction of waste produces has occurred.
[0165] Note, that embodiments are envisioned where the "burn-up"
Step 914 is accomplished at a location separate from, and using a
particle beam source, different from the location at which the main
running Step 912 occurs. For example, embodiments are envisioned
wherein a system 1000 constructed in accordance with the teachings
of this disclosure is operated for a lengthy period of time at a
location where energy generation is desired and then the Thorium
assembly 300 is removed and taken to a different location where it
can be bombarded with high energy particles that result in the
generation of fast neutrons for purposes of waste burn up.
[0166] In accordance with other embodiments, the systems 1000
described herein may be operated to "burn-up" waste materials
during the main period of operation of the assembly. Such
embodiments are particularly suited for applications where the
energy output demands from the system are not constant. For
example, if the system of FIGS. 1A-1B is used to generate
electricity, the demand for electricity may vary depending based on
time, day, month, or weather conditions. For example, if the system
of FIGS. 1A-1B is used to power a remote manufacturing plant, the
plant may be operational--and thus have high energy demands--only
weekdays during normal business hours or only during certain peak
months of the year. In such applications, after an amount of
Uranium-233 has been generated that is sufficient to provide the
desired power output, the system could be operated in Region II
during the periods of high energy demand (such that the production
of energy though fission of Uranium-233 is maximized) and then be
operated in Region IV during periods of low energy demand, such
that the high-energy neutrons generated by the system during such
operational periods can be used to burn some of the TRUs and
long-lasting fission products within the system, thus reducing the
total overall waste produced by the system.
[0167] This mode of operation is generally discussed in FIG.
9C.
[0168] Referring to FIG. 9C, the system may initially be operated
in accordance where the generation of thermal neutrons and the
fission of Uranium-233 is promoted as discussed above at Step 950.
During these intervals, the energy demand of the system can be
monitored at Step 952. If the output demand of the system is not
below a certain threshold (or in alternate embodiments if the
output demand is above a certain threshold level), the system will
continue to operate in a manner where thermal-neutron production
and Uranium-233 fission is promoted. If the energy demand, however,
is below a certain threshold (and, potentially predicted based on
data to remain at that lower level for a particular period time)
the operation of the system can be adjusted to promote the
generation of fast neutrons and the potential burn-up of undesired
waste. This is reflected in Step 954.
[0169] While operating within Step 954, the output demands of the
system can be monitored (at Step 956) and, if they increase, the
system can transition back to operating in the manner described
above in connection with Step 950.
[0170] In the embodiments described above, the system 1000 is
designed (and the particle beam source 200) operated so that the
system--not including the neutrons generated as a result of the
operation of the particle beam source 200--is operated in a
sub-critical manner. As used herein, operation of the system in a
sub-critical manner means that, if the power to the particle beam
source is removed such that the particle beam source provides no
particles to the system, the number of neutrons generated within
the Thorium molten salt assembly 300 as the result of fission or
other nuclear reactions will be insufficient to sustain permanent
and on-going fission reactions within the system. As such, in the
embodiments described above, substantial nuclear fission reactions
within the system will ultimately cease if the particle beam source
ceases to operate. This sub-critical operation of the described
systems is believed to provide a safety margin that can eliminate
(or at least substantially reduce) the potential for an
uncontrolled series of nuclear reactions (sometimes referred to as
a "meltdown") of the assembly 300.
[0171] In the embodiments discussed previously in this disclosure,
the neutrons relied upon to support the nuclear reactions desired
for system operation were generated within the Thorium molten salt
assembly 300. Alternate embodiments are envisioned wherein the
neutrons relied upon for operation on of the system are primarily
generated outside the assembly 300.
[0172] FIG. 10 illustrates one of many alternate embodiments of the
system 1000 of FIGS. 1A and 1B in which fast and/or thermal
neutrons desired for operation of the system are generated outside
of the molten salt assembly.
[0173] Referring to FIG. 10, the alternate embodiment includes a
particle beam source 200, a Thorium molten salt assembly 300, a
heat transfer assembly 400, a generator 500, and a shielding
assembly 600 substantially as described above. The system 1000'
also includes, however, a neutron source target 230. As described
in more detail below, in this alternate embodiment, the neutron
source target 230 comprises one or more elements that are bombarded
with the particle beam from the particle beam source 220 and that,
in response, generates neutrons having various desired energy
levels.
[0174] FIGS. 11A-11F illustrate exemplary neutron source targets
230 that may be used in connection with the embodiment of FIG. 10.
For purposes of the following discussion, it is presumed that the
particle beam source 200 is as described above in connection with
FIGS. 2A-2D in that it can generate protons having energies at two
levels, where the first energy level is above 4.5 MeV and the
second energy level is between about 2.5 MeV and just below 4.5
MeV.
[0175] Referring first to FIG. 11A, an exemplary neutron target
source 252 is illustrated that comprises a core of neutron
reflecting/shielding material (such as graphite) 254 defining an
opening passing therethrough and a neutron-generating target 256
positioned within the opening. FIG. 11A illustrates the
cross-section of such a structure. In operation, particles from the
particle beam source 200 (protons for example) enter the core and
pass through the opening on the core and strike the neutron
generating target 256. The interaction between the high energy
proton beam and the target generates one or more neutrons that pass
through the opening within the core and out of the neutron
generator 252 where they can be provided to the Thorium molten salt
assembly 300 to produce reactions as generally described above.
[0176] The neutron generating target 256 can take the form of any
target that includes a material that, when struck by highly
energized particles, emits neutrons.
[0177] In the example of FIG. 11A the neutron generating target 256
comprises a cone coated with a sufficient amount of Lithium (Li)
such that the interaction with the Lithium on the cone with the
incident proton beam provided by the particle beam source 200 will
cause a Lithium (p, n) reaction producing neutrons at a generally
thermal energy level. FIG. 11B illustrates such a Lithium cone
256.
[0178] When the neutron generating target 256 is Lithium, the
incident energy level of the proton beam provided by the
accelerator should be greater than about 2.4 MeV to generate the
desired neutron density for operation of the system 1000'. As such,
the embodiments of the accelerator discussed above that can
generate proton beams on the order of 3 MeV can be used with the
neutron generating target of FIG. 11B.
[0179] In the embodiment of FIG. 11B bombardment of illustrated
neutron generating target 256 with a proton beam greater than or
about 2.4 MeV will result in the generation of neutrons having an
energy level of between roughly about 1.times.10.sup.-5 and 0.07
MeV. Neutrons at such an energy level can be applied to the Thorium
molten salt system 300 to cause the reactions discussed above
during periods where the generation of thermal neutrons is promoted
(e.g., fission of Uranium-233).
[0180] FIG. 11C illustrates an alternative neutron generating
target 258. In general, the alternate neutron target 258 is like
that of target 256, but it contains Beryllium, instead of Lithium.
The target 258 operates generally as described with respect to the
target 256, with the exception that the impingement of high energy
particles on the Beryllium of target 258 will cause the generation
of neutrons having a generally higher energy level than the
neutrons generated using the Lithium target 256 of FIG. 11B. In
general, the neutrons generated through bombardment of the
Beryllium target of FIG. 11C will have an energy level in excess of
0.7 MeV.
[0181] In the embodiment of FIG. 11C, when the Beryllium target 258
is used the incident energy level of the protons applied to the
target should be in excess of 4.5 MeV. The various particle
accelerators discussed above in connection with FIGS. 2A-2D would
be suitable to provide protons of such an energy level.
[0182] In some embodiments of the system of FIG. 10, it will be
desirable to simultaneously provide neutrons having different
energy levels and, specifically at energy levels around those using
the Lithium target 256 described above and the Beryllium target 258
described above in connection with FIG. 11C. For such embodiments,
it may be possible to utilize the particle beam source 200,
discussed above, in combination with two neutron generating
targets. Such an arrangement is shown in FIG. 11D, where both
Lithium and Beryllium neutron targets are provided and the particle
beam can be directed to one or the other target (or alternated
between the two) to promote the generation of thermal or fast
neutrons, respectively.
[0183] FIGS. 11E and 11F illustrate still further alternate
embodiments for generating fast and thermal neutrons. In the
example of FIG. 11E a single neutron generating target is provided
that includes upper segments 264 formed of Lithium and a lower core
266 formed of Beryllium. In this example, a particle beam of
relatively high energy level particles and a beam shape in the form
of a spot can be directed to the lower core to generate fast
neutrons and a ring-shaped beam of a lower energy level can be
directed to the upper segments to promote the generation of thermal
neutrons.
[0184] In FIG. 11F a neutron generating target is provided in which
a Beryllium core 272 is provided and Lithium is sputtered on to
produce discrete regions 274 of Lithium containing material. In
such an embodiment the surface areas of the target will include
areas of both exposed Lithium and exposed Beryllium such that the
provision of high energy particles will result in the production of
fast and/or slow neutrons. In the example of FIG. 11F, the energy
level of the incident particles can be adjusted to promote the
generation of fast neutrons over thermal (e.g., by increasing the
energy level of the incident particles above 4.5 MeV) or to promote
the generation of thermal neutrons over fast neutrons (e.g., by
maintaining the energy level of the particles comprising the
particle beam between about 2.5 MeV and 3.5 MeV).
[0185] FIG. 12 generally illustrates the generated neutron flux
levels and energy levels when neutron generating targets such as
those illustrated in FIG. 11D are used: (a) a Beryllium target is
bombarded with protons having energy levels of approximately 4.5
MeV (reflected by the triangles), and (b) a Lithium target is
bombarded with approximately 3.0 MeV protons (reflected by the
diamonds).
[0186] The Figures described above, and the written description of
specific structures and functions below are not presented to limit
the scope of what I have invented or the scope of the appended
claims. Rather, the Figures and written description are provided to
teach any person skilled in the art to make and use the inventions
for which patent protection is sought. Those skilled in the art
will appreciate that not all features of a commercial embodiment of
the inventions are described or shown for the sake of clarity and
understanding. Persons of skill in this art will also appreciate
that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's goal for the commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related, and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill in this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
[0187] Aspects of the inventions disclosed herein may be embodied
as an apparatus, system, method, or computer program product.
Accordingly, specific embodiments may take the form of an entirely
hardware embodiment, an entirely software embodiment or an
embodiment combining software and hardware aspects, such as a
"circuit," "module" or "system." Furthermore, embodiments of the
present inventions may take the form of a computer program product
embodied in one or more computer readable storage media having
computer readable program code.
[0188] Reference throughout this disclosure to "one embodiment,"
"an embodiment," or similar language means that a feature,
structure, or characteristic described in connection with the
embodiment is included in at least one of the many possible
embodiments of the present inventions. The terms "including,"
"comprising," "having," and variations thereof mean "including but
not limited to" unless expressly specified otherwise. An enumerated
listing of items does not imply that any or all the items are
mutually exclusive and/or mutually inclusive, unless expressly
specified otherwise. The terms "a," "an," and "the" also refer to
"one or more" unless expressly specified otherwise.
[0189] Furthermore, the described features, structures, or
characteristics of one embodiment may be combined in any suitable
manner in one or more other embodiments. Those of skill in the art
having the benefit of this disclosure will understand that the
inventions may be practiced without one or more of the specific
details, or with other methods, components, materials, and so
forth. In other instances, well-known structures, materials, or
operations are not shown or described in detail to avoid obscuring
aspects of the disclosure.
[0190] Aspects of the present disclosure are described with
reference to schematic flowchart diagrams and/or schematic block
diagrams of methods, apparatuses, systems, and computer program
products according to embodiments of the disclosure. It will be
understood by those of skill in the art that each block of the
schematic flowchart diagrams and/or schematic block diagrams, and
combinations of blocks in the schematic flowchart diagrams and/or
schematic block diagrams, may be implemented by computer program
instructions. Such computer program instructions may be provided to
a processor of a general purpose computer, special purpose
computer, or other programmable data processing apparatus to create
a machine or device, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, structurally configured to implement the functions/acts
specified in the schematic flowchart diagrams and/or schematic
block diagrams block or blocks. These computer program instructions
also may be stored in a computer readable storage medium that can
direct a computer, other programmable data processing apparatus, or
other devices to function in a particular manner, such that the
instructions stored in the computer readable storage medium produce
an article of manufacture including instructions which implement
the function/act specified in the schematic flowchart diagrams
and/or schematic block diagrams block or blocks. The computer
program instructions also may be loaded onto a computer, other
programmable data processing apparatus, or other devices to cause a
series of operational steps to be performed on the computer, other
programmable apparatus or other devices to produce a computer
implemented process such that the instructions that execute on the
computer or other programmable apparatus provide processes for
implementing the functions/acts specified in the flowchart and/or
block diagram block or blocks.
[0191] The schematic flowchart diagrams and/or schematic block
diagrams in the Figures illustrate the architecture, functionality,
and/or operation of possible apparatuses, systems, methods, and
computer program products according to various embodiments of the
present inventions. In this regard, each block in the schematic
flowchart diagrams and/or schematic block diagrams may represent a
module, segment, or portion of code, which comprises one or more
executable instructions for implementing the specified logical
function(s).
[0192] It also should be noted that, in some possible embodiments,
the functions noted in the block may occur out of the order noted
in the figures. For example, two blocks shown in succession may, in
fact, be executed substantially concurrently, or the blocks may
sometimes be executed in the reverse order, depending upon the
functionality involved. Other steps and methods may be conceived
that are equivalent in function, logic, or effect to one or more
blocks, or portions thereof, of the illustrated figures.
[0193] Although various arrow types and line types may be employed
in the flowchart and/or block diagrams, they do not limit the scope
of the corresponding embodiments. Indeed, some arrows or other
connectors may be used to indicate only the logical flow of the
depicted embodiment. For example, but not limitation, an arrow may
indicate a waiting or monitoring period of unspecified duration
between enumerated steps of the depicted embodiment. It will also
be noted that each block of the block diagrams and/or flowchart
diagrams, and combinations of blocks in the block diagrams and/or
flowchart diagrams, may be implemented by special purpose
hardware-based systems that perform the specified functions or
acts, or combinations of special purpose hardware and computer
instructions.
[0194] The description of elements in each Figure may refer to
elements of proceeding Figures. Like numbers refer to like elements
in all figures, including alternate embodiments of like elements.
In some possible embodiments, the functions/actions/structures
noted in the figures may occur out of the order noted in the block
diagrams and/or operational illustrations. For example, two
operations shown as occurring in succession, in fact, may be
executed substantially concurrently or the operations may be
executed in the reverse order, depending upon the
functionality/acts/structure involved.
[0195] The inventions have been described in the context of
preferred and other embodiments and not every embodiment of the
invention has been described. Obvious modifications and alterations
to the described embodiments are available to those of ordinary
skill in the art. The disclosed and undisclosed embodiments are not
intended to limit or restrict the scope or applicability of the
invention conceived of by the Applicants, but rather, in conformity
with the patent laws, Applicants intend to protect fully all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
* * * * *
References