U.S. patent application number 12/930176 was filed with the patent office on 2011-07-07 for standing wave nuclear fission reactor and methods.
This patent application is currently assigned to Searete LLC, a limited liability corporation of the State of Delaware. Invention is credited to Charles E. Ahlfeld, Thomas M. Burke, Tyler S. Ellis, John Rogers Gilleland, Jonatan Hejzlar, Pavel Hejzlar, Roderick A. Hyde, David G. McAlees, Jon D. McWhirter, Ashok Odedra, Robert C. Petroski, Nicholas W. Touran, Joshua C. Walter, Kevan D. Weaver, Thomas Allan Weaver, Charles Whitmer, Lowell L. Wood, JR., George B. Zimmerman.
Application Number | 20110164714 12/930176 |
Document ID | / |
Family ID | 43974172 |
Filed Date | 2011-07-07 |
United States Patent
Application |
20110164714 |
Kind Code |
A1 |
Ahlfeld; Charles E. ; et
al. |
July 7, 2011 |
Standing wave nuclear fission reactor and methods
Abstract
Disclosed embodiments include nuclear fission reactor cores,
nuclear fission reactors, methods of operating a nuclear fission
reactor, and methods of managing excess reactivity in a nuclear
fission reactor.
Inventors: |
Ahlfeld; Charles E.; (La
Jolla, CA) ; Burke; Thomas M.; (Prosser, WA) ;
Ellis; Tyler S.; (Bellevue, WA) ; Gilleland; John
Rogers; (Kirkland, WA) ; Hejzlar; Jonatan;
(Cernosice, CZ) ; Hejzlar; Pavel; (Kirkland,
WA) ; Hyde; Roderick A.; (Redmond, WA) ;
McAlees; David G.; (Bellevue, WA) ; McWhirter; Jon
D.; (Kirkland, WA) ; Odedra; Ashok; (Bellevue,
WA) ; Petroski; Robert C.; (Seattle, WA) ;
Touran; Nicholas W.; (Seattle, WA) ; Walter; Joshua
C.; (Kirkland, WA) ; Weaver; Kevan D.;
(Redmond, WA) ; Weaver; Thomas Allan; (San Mateo,
CA) ; Whitmer; Charles; (North Bend, WA) ;
Wood, JR.; Lowell L.; (Bellevue, WA) ; Zimmerman;
George B.; (Lafayette, CA) |
Assignee: |
Searete LLC, a limited liability
corporation of the State of Delaware
|
Family ID: |
43974172 |
Appl. No.: |
12/930176 |
Filed: |
December 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12925985 |
Nov 2, 2010 |
|
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12930176 |
|
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61280370 |
Nov 2, 2009 |
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Current U.S.
Class: |
376/220 ;
376/352; 376/449 |
Current CPC
Class: |
G21C 15/06 20130101;
Y02E 30/30 20130101; G21C 1/03 20130101; G21C 1/026 20130101; G21C
3/322 20130101; G21C 7/00 20130101; G21C 1/024 20130101; G21C
19/205 20130101 |
Class at
Publication: |
376/220 ;
376/449; 376/352 |
International
Class: |
G21C 7/06 20060101
G21C007/06; G21C 3/32 20060101 G21C003/32; G21C 15/00 20060101
G21C015/00 |
Claims
1. A nuclear fission reactor core comprising: a central core region
including: a plurality of fissile nuclear fuel assemblies; ones of
a plurality of fertile nuclear fuel assemblies; and a plurality of
movable reactivity control assemblies; and a peripheral core region
including: others of the plurality of fertile nuclear fuel
assemblies; and a plurality of neutron absorber assemblies.
2. The nuclear fission reactor core of claim 1, wherein fertile
material in the plurality of fertile nuclear fuel assemblies
includes U.sup.238.
3. The nuclear fission reactor core of claim 2, wherein the
U.sup.238 includes at least one type of uranium chosen from natural
uranium and depleted uranium.
4. The nuclear fission reactor core of claim 2, wherein the
U.sup.238 in ones of the plurality of nuclear fuel assemblies
includes natural uranium and the U.sup.238 in others of the
plurality of nuclear fuel assemblies includes depleted uranium.
5. The nuclear fission reactor core of claim 1, wherein the
plurality of fissile nuclear fuel assemblies include enriched
fissile material.
6. The nuclear fission reactor core of claim 5, wherein the
enriched fissile material includes U.sup.235.
7. The nuclear fission reactor core of claim 1, wherein the
plurality of fissile nuclear fuel assemblies includes: a plurality
of enriched fissile nuclear fuel assemblies; and a plurality of
bred fissile nuclear fuel assemblies.
8. The nuclear fission reactor core of claim 7, wherein enriched
fissile material in the plurality of enriched fissile nuclear fuel
assemblies includes U.sup.235 and bred fissile material in the
plurality of bred fissile nuclear fuel assemblies includes
PU.sup.239.
9. The nuclear fission reactor core of claim 7, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies.
10. The nuclear fission reactor core of claim 7, wherein the
peripheral core region further includes selected ones of the
plurality of enriched fissile nuclear fuel assemblies having at
least a predetermined burnup level.
11. The nuclear fission reactor core of claim 7, wherein the
peripheral core region further includes selected ones of the
plurality of bred fissile nuclear fuel assemblies having at least a
predetermined burnup level.
12. The nuclear fission reactor core of claim 7, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies having less than a
predetermined burnup level.
13. The nuclear fission reactor core of claim 1, wherein: the
plurality of fissile nuclear fuel assemblies includes a plurality
of bred fissile nuclear fuel assemblies; and the core peripheral
region includes a plurality of enriched fissile nuclear fuel
assemblies having at least a predetermined burnup level.
14. The nuclear fission reactor core of claim 13, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies.
15. The nuclear fission reactor core of claim 14, wherein the
peripheral core region further includes selected ones of the
plurality of bred fissile nuclear fuel assemblies having at least a
predetermined burnup level.
16. The nuclear fission reactor core of claim 14, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies having less than a
predetermined burnup level.
17. The nuclear fission reactor core of claim 1, wherein at least
one of the plurality of fissile nuclear fuel assemblies includes
fissile material discharged from a nuclear fission reactor.
18. The nuclear fission reactor core of claim 17, wherein the
plurality of fissile nuclear fuel assemblies that includes fissile
material discharged from a nuclear fission reactor includes at
least one re-clad fissile fuel assembly.
19. The nuclear fission reactor core of claim 1, further comprising
a plurality of fuel assembly flow receptacles defining: a first
plurality of reactor coolant flow orifices in the central core
region; and a second plurality of reactor coolant flow orifices in
the peripheral core region.
20. The nuclear fission reactor core of claim 19, wherein the first
plurality of reactor coolant flow orifices includes a plurality of
reactor coolant flow orifice groups.
21. The nuclear fission reactor core of claim 20, wherein flow rate
through a selected one of the plurality of reactor coolant flow
orifice groups is based upon a power profile at a radial location
of the selected one of the plurality of reactor coolant flow
orifice groups.
22. The nuclear fission reactor core of claim 19, wherein flow rate
through the second plurality of reactor coolant flow orifices
includes a predetermined flow rate based upon power level in the
peripheral core region.
23. The nuclear fission reactor core of claim 19, wherein the first
and second pluralities of reactor coolant flow orifices include
fixed orifices.
24. The nuclear fission reactor core of claim 19, wherein the first
and second pluralities of reactor coolant flow orifices include
variable orifices.
25. The nuclear fission reactor core of claim 19, wherein the first
and second pluralities of reactor coolant flow orifices include
fixed orifices and variable orifices.
26. The nuclear fission reactor core of claim 1, wherein the
plurality of movable reactivity control assemblies and the
plurality of neutron absorber assemblies include hafnium
hydride.
27-160. (canceled)
161. A nuclear fission reactor core comprising: a central core
region including: a plurality of fissile nuclear fuel assemblies;
ones of a plurality of fertile nuclear fuel assemblies, wherein
fertile material in the plurality of fertile nuclear fuel
assemblies includes U.sup.238; and a plurality of movable
reactivity control assemblies; and a peripheral core region
including: others of the plurality of fertile nuclear fuel
assemblies, wherein fertile material in the plurality of fertile
nuclear fuel assemblies includes U.sup.238; and a plurality of
neutron absorber assemblies; a plurality of fuel assembly flow
receptacles defining: a first plurality of reactor coolant flow
orifices in the central core region; and a second plurality of
reactor coolant flow orifices in the peripheral core region.
162. The nuclear fission reactor core of claim 161, wherein the
U.sup.238 includes at least one type of uranium chosen from natural
uranium and depleted uranium.
163. The nuclear fission reactor core of claim 161, wherein the
U.sup.238 in ones of the plurality of nuclear fuel assemblies
includes natural uranium and the U.sup.238 in others of the
plurality of nuclear fuel assemblies includes depleted uranium.
164. The nuclear fission reactor core of claim 161, wherein the
plurality of fissile nuclear fuel assemblies include enriched
fissile material.
165. The nuclear fission reactor core of claim 164, wherein the
enriched fissile material includes U.sup.235.
166. The nuclear fission reactor core of claim 161, wherein the
plurality of fissile nuclear fuel assemblies includes: a plurality
of enriched fissile nuclear fuel assemblies; and a plurality of
bred fissile nuclear fuel assemblies.
167. The nuclear fission reactor core of claim 166, wherein
enriched fissile material in the plurality of enriched fissile
nuclear fuel assemblies includes U.sup.235 and bred fissile
material in the plurality of bred fissile nuclear fuel assemblies
includes PU.sup.239.
168. The nuclear fission reactor core of claim 166, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies.
169. The nuclear fission reactor core of claim 166, wherein the
peripheral core region further includes selected ones of the
plurality of enriched fissile nuclear fuel assemblies having at
least a predetermined burnup level.
170. The nuclear fission reactor core of claim 166, wherein the
peripheral core region further includes selected ones of the
plurality of bred fissile nuclear fuel assemblies having at least a
predetermined burnup level.
171. The nuclear fission reactor core of claim 166, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies having less than a
predetermined burnup level.
172. The nuclear fission reactor core of claim 161, wherein: the
plurality of fissile nuclear fuel assemblies includes a plurality
of bred fissile nuclear fuel assemblies; and the core peripheral
region includes a plurality of enriched fissile nuclear fuel
assemblies having at least a predetermined burnup level.
173. The nuclear fission reactor core of claim 172, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies.
174. The nuclear fission reactor core of claim 173, wherein the
peripheral core region further includes selected ones of the
plurality of bred fissile nuclear fuel assemblies having at least a
predetermined burnup level.
175. The nuclear fission reactor core of claim 173, wherein the
peripheral core region further includes ones of the plurality of
bred fissile nuclear fuel assemblies having r less than a
predetermined burnup level.
176. The nuclear fission reactor core of claim 161, wherein at
least one of the plurality of fissile nuclear fuel assemblies
includes fissile material discharged from a nuclear fission
reactor.
177. The nuclear fission reactor core of claim 176, wherein the
plurality of fissile nuclear fuel assemblies that includes fissile
material discharged from a nuclear fission reactor includes at
least one re-clad fissile fuel assembly.
178. The nuclear fission reactor core of claim 161, wherein the
first plurality of reactor coolant flow orifices includes a
plurality of reactor coolant flow orifice groups.
179. The nuclear fission reactor core of claim 178, wherein flow
rate through a selected one of the plurality of reactor coolant
flow orifice groups is based upon a power profile at a radial
location of the selected one of the plurality of reactor coolant
flow orifice groups.
180. The nuclear fission reactor core of claim 161, wherein flow
rate through the second plurality of reactor coolant flow orifices
includes a predetermined flow rate based upon power level in the
peripheral core region.
181. The nuclear fission reactor core of claim 161, wherein the
first and second pluralities of reactor coolant flow orifices
include fixed orifices.
182. The nuclear fission reactor core of claim 161, wherein the
first and second pluralities of reactor coolant flow orifices
include variable orifices.
183. The nuclear fission reactor core of claim 161, wherein the
first and second pluralities of reactor coolant flow orifices
include fixed orifices and variable orifices.
184. The nuclear fission reactor core of claim 161, wherein the
plurality of movable reactivity control assemblies and the
plurality of neutron absorber assemblies include hafnium hydride.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is related to and claims the benefit
of the earliest available effective filing date from the following
listed application (the "Related Application") (e.g., claims
benefits under 35 USC .sctn.119(e) for provisional patent
applications, for any and all parent, grandparent,
great-grandparent, etc. applications of the Related
Application).
RELATED APPLICATIONS
[0002] For purposes of the USPTO extra-statutory requirements, the
present application claims benefit of priority of U.S. Provisional
Patent Application No. 61/280,370, entitled TRAVELING WAVE NUCLEAR
FISSION REACTOR FUEL SYSTEM AND METHOD, naming Charles E. Ahlfeld,
Thomas M. Burke, Tyler S. Ellis, John Rogers Gilleland, Jonatan
Hejzlar, Pavel Hejzlar, Roderick A. Hyde, David G. McAlees, Jon D.
McWhirter, Ashok Odedra, Robert C. Petroski, Nicholas W. Touran,
Joshua C. Walter, Kevan D. Weaver, Thomas Allan Weaver, Charles
Whitmer, Lowell L. Wood, Jr., and George B. Zimmerman as inventors,
filed Nov. 2, 2009, which was filed within the twelve months
preceding the filing date of the present application or is an
application of which a currently co-pending application is entitled
to the benefit of the filing date.
[0003] The United States Patent Office (USPTO) has published a
notice to the effect that the USPTO's computer programs require
that patent applicants reference both a serial number and indicate
whether an application is a continuation or continuation-in-part.
Stephen G. Kunin, Benefit of Prior-Filed Application, USPTO
Official Gazette Mar. 18, 2003, available at
http://www.uspto.gov/web/offices/com/sol/og/2003/week11/patbene.htm.
The present Applicant Entity (hereinafter "Applicant") has provided
above a specific reference to the application(s) from which
priority is being claimed as recited by statute. Applicant
understands that the statute is unambiguous in its specific
reference language and does not require either a serial number or
any characterization, such as "continuation" or
"continuation-in-part," for claiming priority to U.S. patent
applications. Notwithstanding the foregoing, Applicant understands
that the USPTO's computer programs have certain data entry
requirements, and hence Applicant is designating the present
application as a continuation-in-part of its parent applications as
set forth above, but expressly points out that such designations
are not to be construed in any way as any type of commentary and/or
admission as to whether or not the present application contains any
new matter in addition to the matter of its parent
application(s).
[0004] All subject matter of the Related Application and of any and
all parent, grandparent, great-grandparent, etc. applications of
the Related Application is incorporated herein by reference to the
extent such subject matter is not inconsistent herewith.
BACKGROUND
[0005] The present patent application relates to nuclear fission
reactors and methods.
SUMMARY
[0006] Disclosed embodiments include nuclear fission reactor cores,
nuclear fission reactors, methods of operating a nuclear fission
reactor, and methods of managing excess reactivity in a nuclear
fission reactor.
[0007] The foregoing is a summary and thus may contain
simplifications, generalizations, inclusions, and/or omissions of
detail; consequently, those skilled in the art will appreciate that
the summary is illustrative only and is NOT intended to be in any
way limiting. In addition to any illustrative aspects, embodiments,
and features described above, further aspects, embodiments, and
features will become apparent by reference to the drawings and the
following detailed description. Other aspects, features, and
advantages of the devices and/or processes and/or other subject
matter described herein will become apparent in the teachings set
forth herein.
BRIEF DESCRIPTION OF THE FIGURES
[0008] FIGS. 1A-1C are partial-cutaway perspective views of an
illustrative nuclear fission reactor.
[0009] FIG. 2 is a top plan view in schematic form of an
illustrative nuclear fission reactor core.
[0010] FIG. 3 is partial-cutaway perspective view in schematic form
of an illustrative nuclear fuel assembly.
[0011] FIG. 4A is a partial-cutaway perspective view in schematic
form of illustrative fuel assembly flow receptacles.
[0012] FIG. 4B illustrates a graph of relative flux distribution
overlaid with a side plan view in schematic form of an illustrative
stepped core support grid plate.
[0013] FIGS. 5A and 5B are side plan views in schematic form of
illustrative decay heat removal systems.
[0014] FIGS. 6A and 6B are illustrative graphs of reactivity versus
burnup.
[0015] FIG. 7 is an illustrative graph of plutonium isotope
evolution versus utilization of U.sup.238.
[0016] FIG. 8A is a flowchart of an illustrative method of
operating a nuclear fission reactor.
[0017] FIGS. 8B-8X are flowcharts of illustrative details of the
method of FIG. 8A.
[0018] FIG. 9A is a flowchart of another illustrative method of
operating a nuclear fission reactor.
[0019] FIGS. 9B-9V are flowcharts of illustrative details of the
method of FIG. 9A.
[0020] FIG. 10A is a flowchart of an illustrative method of
managing excess reactivity in a nuclear fission reactor.
[0021] FIGS. 10B-10H are flowcharts of illustrative details of the
method of FIG. 10A.
DETAILED DESCRIPTION
Introduction
[0022] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, the use of similar or the same symbols in different
drawings typically indicates similar or identical items, unless
context dictates otherwise.
[0023] The illustrative embodiments described in the detailed
description, drawings, and claims are not meant to be limiting.
Other embodiments may be utilized, and other changes may be made,
without departing from the spirit or scope of the subject matter
presented here.
[0024] One skilled in the art will recognize that the herein
described components (e.g., operations), devices, objects, and the
discussion accompanying them are used as examples for the sake of
conceptual clarity and that various configuration modifications are
contemplated. Consequently, as used herein, the specific exemplars
set forth and the accompanying discussion are intended to be
representative of their more general classes. In general, use of
any specific exemplar is intended to be representative of its
class, and the non-inclusion of specific components (e.g.,
operations), devices, and objects should not be taken limiting.
[0025] The present application uses formal outline headings for
clarity of presentation. However, it is to be understood that the
outline headings are for presentation purposes, and that different
types of subject matter may be discussed throughout the application
(e.g., device(s)/structure(s) may be described under
process(es)/operations heading(s) and/or process(es)/operations may
be discussed under structure(s)/process(es) headings; and/or
descriptions of single topics may span two or more topic headings).
Hence, the use of the formal outline headings is not intended to be
in any way limiting.
[0026] Overview
[0027] Referring now to FIGS. 1A-1C and FIG. 2 and given by way of
non-limiting overview, an illustrative nuclear fission reactor 10
will be described by way of illustration and not of limitation. As
will be discussed below in detail, embodiments of the nuclear
fission reactor 10 are breed-and-burn fast reactors (also referred
to as traveling wave reactors, or TWRs) in which a standing wave of
breeding-and-fissioning (also referred to as a breed-burn wave) via
movement (also referred to as shuffling) of nuclear fuel
assemblies.
[0028] Still by way of overview, a nuclear fission reactor core 12
is disposed in a reactor vessel 14. A central core region 16 (FIG.
2) of the nuclear fission reactor core 12 includes fissile nuclear
fuel assemblies 18 (FIG. 2). The central core region 16 also
includes fertile nuclear fuel assemblies 20a (FIG. 2). The central
core region 16 also includes movable reactivity control assemblies
22 (FIG. 2).
[0029] A peripheral core region 24 (FIG. 2) of the nuclear fission
reactor core 12 includes fertile nuclear fuel assemblies 20b (FIG.
2). It will be appreciated that the fertile nuclear fuel assemblies
20a and 20b may be made of the same or similar construction (as
indicated by use of similar reference numbers). As will be
explained further below, the fertile nuclear fuel assemblies 20a
reside in a neutron flux environment in the central core region 16
that is different from the neutron flux environment in the
peripheral core region 24 (in which the fertile nuclear fuel
assemblies 20b reside). As a result, over core life the fertile
nuclear fuel assemblies 20a may undergo breeding and may experience
burnup at rates that are different from rates undergone and
experienced by the fertile nuclear fuel assemblies 20b. Therefore,
the similar (but not the same) reference numbers 20a and 20b are
used to help keep track of the fertile nuclear fuel assemblies 20a
and 20b during discussions herein of various phases of core life.
The peripheral core region 24 also includes neutron absorber
assemblies 26.
[0030] An in-vessel handling system 28 is configured to shuffle
ones of the fissile nuclear fuel assemblies 18 and ones of the
fertile nuclear fuel assemblies 20a and 20b. The nuclear fission
reactor 10 also includes a reactor coolant system 30.
[0031] Continuing by way of non-limiting overview, according to
some aspects methods are provided for operating a nuclear fission
reactor. Given by way of non-limiting example, in some embodiments
fissile nuclear fuel material in a plurality of fissile nuclear
fuel assemblies is fissioned in a central core region of a nuclear
fission reactor core of a nuclear fission reactor. Fissile material
is bred in ones of a plurality of fertile nuclear fuel assemblies
in the central core region of the nuclear fission reactor core, and
selected ones of the plurality of fissile nuclear fuel assemblies
and selected ones and selected others of the plurality of fertile
nuclear fuel assemblies are shuffled in a manner that establishes a
standing wave of breeding fissile nuclear fuel material and
fissioning fissile nuclear fuel material.
[0032] Continuing by way of non-limiting overview, according to
some aspects methods are provided for managing excess reactivity in
a nuclear fission reactor. Given by way of non-limiting example, in
some embodiments criticality with a positive quantity of reactivity
is achieved in a central core region of a reactor core of a nuclear
fission reactor. The quantity of reactivity is increased until a
predetermined burnup level is achieved in selected ones of fuel
assemblies in the reactor core, and the increase in reactivity is
compensated for.
[0033] Details will be set forth below by way of non-limiting
examples.
[0034] Illustrative Nuclear Fission Reactors
[0035] In the discussion set forth below, details regarding
extra-core components of the nuclear fission reactor 10 will be set
forth first by way of non-limiting examples. Details regarding
extra-core components of the nuclear fission reactor 10 will be set
forth next by way of non-limiting examples. This ordering of
discussion details will facilitate an understanding of
establishment of a standing wave of breeding and fissioning in the
nuclear fission reactor core 10.
[0036] Extra-Core Components
[0037] Still referring to FIGS. 1A-1C and FIG. 2, embodiments of
the nuclear fission reactor 10 may be sized for any application as
desired. For example, various embodiments of the nuclear fission
reactor 10 may be used in low power (around 300 MW.sub.e-around 500
MW.sub.e) applications, medium power (around 500 MW.sub.e-around
1000 MW.sub.e) applications, and large power (around 1000 MW.sub.e
and above) applications as desired.
[0038] Embodiments of the nuclear fission reactor 10 are based on
elements of liquid metal-cooled, fast reactor technology. For
example, in various embodiments the reactor coolant system 30
includes a pool of liquid sodium disposed in the reactor vessel 14.
In such cases, the nuclear fission reactor core 12 is submerged in
the pool of sodium coolant in the reactor vessel 14. The reactor
vessel 14 is surrounded by a containment vessel 32 that helps
prevent loss of sodium coolant in the unlikely case of a leak from
the reactor vessel 14.
[0039] In various embodiments the reactor coolant system 30 also
includes reactor coolant pumps 34. The reactor coolant pumps 34 may
be any suitable pump as desired, such as for example
electromechanical pumps or electromagnetic pumps.
[0040] In various embodiments the reactor coolant system 30 also
includes heat exchangers 36. The heat exchangers 36 are disposed in
the pool of primary liquid sodium. The heat exchangers 36 have
non-radioactive intermediate sodium coolant on the other side of
the heat exchangers 36. To that end, the heat exchangers 36 may be
considered intermediate heat exchangers. Steam generators (not
shown for clarity in FIGS. 1A-1C and 2) are in thermal
communication with the heat exchangers 36. It will be appreciated
that any number of reactor coolant pumps 34, heat exchangers 36,
and steam generators may be used as desired.
[0041] The reactor coolant pumps 34 circulate primary sodium
coolant through the nuclear fission reactor core 12. The pumped
primary sodium coolant exits the nuclear fission reactor core 12 at
a top of the nuclear fission reactor core 12 and passes through one
side of the heat exchangers 36. Heated intermediate sodium coolant
is circulated via intermediate sodium loops 42 to the steam
generators (not shown) that, in turn, generate steam to drive
turbines (not shown) and electrical generators (not shown).
[0042] During periods of reactor shut down, in some embodiments
plant electrical loads are powered by the electrical grid and decay
heat removal is provided by pony motors (not shown for clarity) on
the reactor coolant pumps 34 that deliver reduced reactor coolant
flow through heat transport systems.
[0043] Referring additionally to FIGS. 5A and 5B, in various
embodiments the nuclear fission reactor 10 includes a decay heat
removal system 38. In the event that electrical power is not
available from the electric grid, decay heat is removed using the
decay heat removal system 38. In various embodiments, the decay
heat removal system 38 may include either one or both of two
dedicated safety class decay heat removal systems 38a (FIG. 5A) and
38b (FIG. 5B) which operate entirely by natural circulation with no
need for electrical power. In the safety class decay heat removal
system 38a (FIG. 5A), heat from the nuclear fission reactor core 12
first is transferred by naturally circulated sodium to the reactor
vessel 14, then is radiated across an argon-filled gap 40 between
the reactor vessel 14 and the containment vessel 32, and finally is
removed by naturally circulating ambient air that flows along the
wall of the containment vessel 32.
[0044] In the safety class decay heat removal system 38b (FIG. 5B),
the heat exchangers 36 and the intermediate sodium loops 42 (FIGS.
1A-1C) transfer heat by natural circulation of sodium to steam
generators 44 where the heat is dissipated through shell walls of
the steam generator 44 using ambient temperature air drawn in
through protected air intakes 46.
[0045] Referring back to FIGS. 1A-1C and 2, the in-vessel handling
system 28 is configured to shuffle ones of the fissile nuclear fuel
assemblies 18 and ones of the fertile nuclear fuel assemblies 20a
and 20b. In some stages of core life (as will be discussed below),
it may be desired to shuffle ones of the fissile nuclear fuel
assemblies 18 and ones of the fertile nuclear fuel assemblies 20a
and 20b between the central core region 16 and the peripheral core
region 24. Thus, the in-vessel handling system 28 may also be
configured to shuffle ones of the fissile nuclear fuel assemblies
18 and ones of the fertile nuclear fuel assemblies 20a and 20b
between the central core region 16 and the peripheral core region
24.
[0046] It will be appreciated that the in-vessel handling system 28
permits movement of the selected fissile nuclear fuel assemblies 18
and fertile nuclear fuel assemblies 20a and 20b without removing
the moved fissile nuclear fuel assemblies 18 and fertile nuclear
fuel assemblies 20a and 20b from the nuclear fission reactor
10.
[0047] In various embodiments, the in-vessel handling system 28
includes a rotating plug 48 and a rotating plug 50 that are both
vertically spaced apart from the top of the nuclear fission reactor
core 12. The rotating plug 50 is smaller than the rotating plug 48
and is disposed on top of the rotating plug 48. An offset arm
machine 52 extends through the rotating plug 48 to the top of the
nuclear fission reactor core 12. The offset arm machine 52 is
rotatable through the rotating plug 48. A straight pull machine 54
extends through the rotating plug 50 to the top of the nuclear
fission reactor core 12.
[0048] Lower ends of the offset arm machine 52 and the straight
pull machine 54 include suitable gripping devices, such as grapples
or the like, that enable gripping of selected fissile nuclear fuel
assemblies 18 and fertile nuclear fuel assemblies 20a and 20b (and
in some applications, as will be discussed below, neutron absorber
assemblies disposed in the peripheral core region 24) by the offset
arm machine 52 and the straight pull machine 54 during movement
operations.
[0049] Rotation of the rotating plugs 48 and 50 and the offset arm
machine 52 allows the offset arm machine 52 and the straight pull
machine 54 to be localized to any desired position for pulling a
selected assembly out of the nuclear fission reactor core 12 and
for re-inserting the selected assembly into the nuclear fission
reactor core 12 at any desired empty location.
[0050] In some embodiments the in-vessel handling system 28 may be
further configured to move ones of the neutron absorber assemblies
among selected locations in the peripheral core region 24. In such
cases, the locations in the peripheral core region 24 may be
selected from predetermined radial locations in the peripheral core
region 24 based upon a predetermined burnup level of nuclear fuel
assemblies 18, 20a, and/or 20b (depending upon stage of core life
and burnup levels) that are located in the peripheral core region
24. In some other embodiments, the in-vessel handling system 28 may
be further configured to rotate ones of the neutron absorber
assemblies.
[0051] In some other embodiments, the in-vessel handling system 28
may be further configured to shuffle ones of the fissile nuclear
fuel assemblies 18 and ones of the fertile nuclear fuel assemblies
20a and/or 20b (depending upon stage of core life and burnup
levels) between the central core region 16 and a portion of the
reactor vessel 14 that is located as desired exterior the nuclear
fission reactor core 12.
[0052] In-Core Components
[0053] Given by way of nonlimiting overview, in embodiments of the
nuclear fission reactor core 12 a sufficient number of fissile
nuclear fuel assemblies achieve initial criticality and sufficient
breeding to approach a steady state reactor core breed-and-burn
(breeding-and-fissioning) condition. The fissile assemblies are
primarily located in the central core region 16, which generates
most of the core power. Fertile nuclear fuel assemblies are placed
in the central core region 16 and the peripheral core region 24 and
their number is selected such that reactor operation is possible
for up to 40 years or more without the need to bring new fuel into
the reactor. The initial core loading is configured to achieve
criticality with a small amount of excess reactivity and ascension
to full power output shortly after initial reactor startup. Excess
reactivity increases because of breeding until a predetermined
burnup is achieved in a selected number of fuel assemblies. The
reactivity increase is compensated by movable reactivity control
assemblies, which are gradually inserted into the core to maintain
core criticality.
[0054] Still given by way of non-limiting overview, a wave of
breeding and fissioning (a "breed-burn wave" is originated in the
central core region 16 but does not move through fixed core
material.
[0055] Instead, a "standing" wave of breeding and fissioning
("burning") is established by periodically moving core material in
and out of the breed-burn region. This movement of fuel assemblies
is referred to as "fuel shuffling" and will be described in more
detail later.
[0056] Details regarding components within the nuclear fission
reactor core 12 will now be discussed by way of non-limiting
examples. When relevant, differences over core life in composition
and/or burnup levels of fuel assemblies and/or locations of fuel
assemblies within the nuclear fission reactor core 12 will be
noted.
[0057] Regardless of stage of core life, the central core region 16
includes the movable reactivity control assemblies 22. The movable
reactivity control assemblies 22 suitably may be provided as
control rods and may be moved axially in and/or out of the central
core region 16 by associated control rod drive mechanisms. It will
be appreciated that axial position of the movable reactivity
control assemblies 22 may be adjusted by the control rod drive
mechanisms to insert neutron absorbing material into the central
core region 16 and/or to remove neutron absorbing material from the
central core region 16 as desired (such as to compensate for
increases in reactivity, to compensate for decreases in reactivity,
to shut down the reactor for planned shutdowns, and/or to start up
the reactor after the reactor has been shut down). It will also be
appreciated that in some embodiments the movable reactivity control
assemblies 22 may perform safety functions, shut as rapidly
inserting neutron absorbing material to rapidly shut down the
reactor (that is, scramming the reactor). In some embodiments,
neutron absorbing material disposed in the movable reactivity
control assemblies 22 may include hafnium hydride.
[0058] Also regardless of stage of core life, the peripheral core
region 24 includes the neutron absorber assemblies 26. Unlike the
movable reactivity control assemblies 22 (which may be moved during
reactor operation as desired, such as to compensate for increases
in reactivity), the neutron absorber assemblies 26 remain in-place
and do not move during reactor operation. The neutron absorber
assemblies 26 help maintain a low core power level in the
peripheral core region 24. This low power level helps to simplify
coolant flow requirements in the peripheral core region 24. This
low power level also helps to mitigate further increases in burnup
in fuel assemblies that previously have been used for power
production in the central core region 16 and subsequently have been
moved from the central core region 16 to the peripheral core region
24. In some embodiments, neutron absorbing material disposed in the
neutron absorber assemblies 26 may include hafnium hydride.
[0059] However, as discussed above, in some embodiments, if desired
the neutron absorber assemblies 26 may be moved by the in-vessel
handling system 28 among selected locations in the peripheral core
region 24. As mentioned above, the locations in the peripheral core
region 24 may be selected from predetermined radial locations in
the peripheral core region 24 based upon a predetermined burnup
level of nuclear fuel assemblies 18, 20a, and/or 20b (depending
upon stage of core life and burnup levels) that are located in the
peripheral core region 24. As also discussed above, in some other
embodiments the neutron absorber assemblies 26 may be rotated by
the in-vessel handling system 28.
[0060] Now that the movable reactivity control assemblies 22 and
the neutron absorber assemblies 26 have been discussed, the nuclear
fuel assemblies 18, 20a, and 20b will be discussed. As mentioned
above, this discussion includes references to various stages of
core life.
[0061] Regardless of stage of core life, fertile material in the
fertile nuclear fuel assemblies 20 (that is, the fertile nuclear
fuel assemblies 20a and the fertile nuclear fuel assemblies 20b)
includes U.sup.238. In various embodiments, the U.sup.238 may
include natural uranium and/or depleted uranium. Thus, in various
embodiments at least one of the fertile nuclear fuel assemblies 20a
may include U.sup.238 that includes natural uranium. In some other
embodiments, at least one of the fertile nuclear fuel assemblies
20a may include U.sup.238 that includes depleted uranium. In some
embodiments, at least one of the fertile nuclear fuel assemblies
20b may include U.sup.238 that includes natural uranium. In some
embodiments, at least one of the fertile nuclear fuel assemblies
20b may include U.sup.238 that includes depleted uranium.
[0062] That is, at any point in core life any one or more of the
nuclear fuel assemblies 20a may include U.sup.238 that includes
natural uranium, any one or more of the nuclear fuel assemblies 20a
may include U.sup.238 that includes depleted uranium, any one or
more of the nuclear fuel assemblies 20b may include U.sup.238 that
includes natural uranium, and/or any one or more of the nuclear
fuel assemblies 20b may include U.sup.238 that includes depleted
uranium.
[0063] Thus, regardless of stage of core life, the U.sup.238 in the
fertile nuclear fuel assemblies 20a and/or 20b need not be limited
to any one of natural uranium or depleted uranium. Therefore, at
any stage in core life, one or more of the nuclear fuel assemblies
20a may include natural uranium, one or more of the nuclear fuel
assemblies 20a may include depleted uranium, one or more of the
nuclear fuel assemblies 20b may include natural uranium, and/or one
or more of the nuclear fuel assemblies 20b may include depleted
uranium.
[0064] At beginning of life (BOL), in various embodiments the
central core region 16 includes the fissile nuclear fuel assemblies
18, the fertile nuclear fuel assemblies 20a, and the movable
reactivity control assemblies 22, and the peripheral core region
includes the fertile nuclear fuel assemblies 20b and the neutron
absorber assemblies 26. The fertile nuclear fuel assemblies 20a and
20b, the movable reactivity control assemblies 22, and the neutron
absorber assemblies 26 have been discussed above for all stages of
core life, including BOL.
[0065] At BOL, the central core region 16 includes the fissile
nuclear fuel assemblies 18 and the fertile nuclear fuel assemblies
20, and during core life (and possibly at end-of-life) the central
core region 16 includes the fissile nuclear fuel assemblies 18 and
the fertile nuclear fuel assemblies 20a and/or 20b. The nuclear
fuel assemblies 18 and 20 may be arranged as desired within the
central core region 16. In some embodiments, the nuclear fuel
assemblies 18 and 20 may be arranged symmetrically within the
central core region 16.
[0066] At BOL, the fissile nuclear fuel assemblies 18 include
enriched fissile nuclear assemblies 18a. In various embodiments,
enriched fissile material in the enriched fissile nuclear
assemblies 18a includes U.sup.235. Uranium in the enriched fissile
nuclear fuel assemblies 18a is typically enriched less than twenty
percent (20%) in the U.sup.235 isotope. It will be appreciated that
in some embodiments (such as the first of a fleet of the nuclear
fission reactors 10), at BOL all of the fissile material in the
fissile nuclear fuel assemblies 18a includes U.sup.235.
[0067] However, in other embodiments (such as in later
nth-of-a-kind members of a fleet of the nuclear fission reactors
10), as will be discussed below at BOL at least some of the fissile
material in the fissile nuclear fuel assemblies 18a may include
PU.sup.239 (that has been bred in previous members of the fleet of
nuclear fission reactors 10).
[0068] It will be further appreciated that only a small mass of
fissile nuclear fuel material (relative to the total mass of
nuclear fuel material, including fertile nuclear fuel material,
included in the nuclear fission reactor core 10 and, as will be
appreciated, as opposed to a conventional fast breeder reactor) is
entailed in initiating a breeding-and-fissioning (breed-burn) wave
in the nuclear fission reactor core 10. Illustrative initiation and
propagation of a breeding-and-fissioning (breed-burn) wave is
described by way of example and not of limitation in U.S. patent
application Ser. No. 11/605,943, entitled AUTOMATED NUCLEAR POWER
REACTOR FOR LONG-TERM OPERATION, naming RODERICK A. HYDE, MURIEL Y.
ISHIKAWA, NATHAN P. MYHRVOLD, AND LOWELL L. WOOD, JR. as inventors,
filed 28 Nov. 2006, the contents of which are hereby incorporated
by reference. It will further be noted that it is within the
capacity of a person of skill in the art of nuclear fission reactor
design and operation to determine, without undue experimentation,
the amount of fissile nuclear fuel material that is entailed in
initiating a breeding-and-fissioning (breed-burn) wave in a nuclear
fission reactor core 10 of any size as desired.
[0069] It will also be appreciated that a breed-burn wave does not
move through fixed core material. Instead, a "standing" wave of
breeding and burning (fissioning) is established by periodically
moving core material in and out of the breed-burn region. This
movement of fuel assemblies is referred to as "fuel shuffling" and
will be described in more detail later.
[0070] It will be appreciated that after BOL the nuclear fission
reactor 10 has been started up and the enriched fissile nuclear
fuel assemblies 18a have begun fissioning. Some of the neutrons may
be absorbed by nuclei of fertile material, such as U.sup.238, in
the fertile nuclear fuel assemblies 20a in the central core region
16. As a result of such absorption, in some instances the U.sup.238
will be converted via capture to U.sup.239, then via .beta. decay
to Np.sup.239, then via further .beta. decay to Pu.sup.239. Thus,
in such cases the fertile material (that is, U.sup.238) in the
fertile nuclear fuel assemblies 20a will have been bred to fissile
material (that is, Pu.sup.239) and, as a result, such fertile
nuclear fuel assemblies 20a will have been converted into bred
nuclear fuel assemblies 18b.
[0071] Therefore, it will be appreciated that after BOL the fissile
nuclear fuel assemblies 18 in the central core region 16 include
the enriched fissile nuclear fuel assemblies 18a and the bred
fissile nuclear fuel assemblies 18b. As discussed above, fissile
material in the enriched fissile nuclear fuel assemblies 18a may
include U.sup.235 and fissile material in the bred fissile nuclear
fuel assemblies 18b may include Pu.sup.239.
[0072] Some of the other neutrons may be absorbed by other nuclei
of fertile material, such as U.sup.238, in the fertile nuclear fuel
assemblies 20a in the central core region 16. As a result of such
absorption, in some other instances it will be appreciated that the
U.sup.238 in some of the fertile nuclear fuel assemblies 20a may
undergo fast fission.
[0073] It will be further appreciated that, after BOL, some
neutrons may leak from the central core region 16 to the peripheral
core region 24. In such cases, some of the leaked neutrons may be
absorbed by fertile material (such as U.sup.238) in the fertile
nuclear fuel assemblies 20b in the peripheral core region 24. As a
result of such absorption and as discussed above, in some instances
the U.sup.238 will be converted via capture to U.sup.239, then via
.beta. decay to Np.sup.239, then via further .beta. decay to
Pu.sup.239. Thus, in such cases the fertile material (that is,
U.sup.238) in the fertile nuclear fuel assemblies 20b will have
been bred to fissile material (that is, Pu.sup.239) and, as a
result, such fertile nuclear fuel assemblies 20b will have been
converted into bred nuclear fuel assemblies 18b. Thus, in such
cases, after BOL the peripheral core region 24 may include ones of
the bred fissile nuclear fuel assemblies 18b.
[0074] Some of the other leaked neutrons may be absorbed by other
nuclei of fertile material, such as U.sup.238, in the fertile
nuclear fuel assemblies 20b in the peripheral core region 24. As a
result of such absorption, in some other instances it will be
appreciated that the U.sup.238 in some of the fertile nuclear fuel
assemblies 20b may undergo fast fission. As discussed above, the
neutron absorber assemblies 26 help maintain a low power level in
the peripheral core region even though fast fission of U.sup.238 in
the fertile nuclear fuel assemblies 20b in the peripheral core
region 24 may occur.
[0075] The enriched fissile nuclear fuel assemblies 18a will
undergo burnup after BOL. After some time after BOL, the enriched
fissile nuclear fuel assemblies 18a will accumulate sufficient
burnup such that it will be desired to shuffle (or move) such
enriched fissile nuclear fuel assemblies 18a from the central core
region 16 to the peripheral core region 24 (with the in-vessel
handling system 28). It will be appreciated that a person of skill
in the art of nuclear fission reactor design and operation will be
able to determine, without undue experimentation, a burnup level at
which one of, the enriched fissile nuclear fuel assemblies 18a is
to be shuffled from the central core region 16 to the peripheral
core region 24. Thus, in such cases, the peripheral core region 24
may further include selected ones of the enriched fissile nuclear
fuel assemblies 18a having at least a predetermined burnup
level.
[0076] Likewise, the bred fissile nuclear fuel assemblies 18b will
also undergo burnup after BOL. After some time after BOL, the bred
fissile nuclear fuel assemblies 18b will accumulate sufficient
burnup such that it will be desired to shuffle (or move) such bred
fissile nuclear fuel assemblies 18b from the central core region 16
to the peripheral core region 24 (with the in-vessel handling
system 28). It will be appreciated that a person of skill in the
art of nuclear fission reactor design and operation will be able to
determine, without undue experimentation, a burnup level at which
one of the enriched fissile nuclear fuel assemblies 18b is to be
shuffled from the central core region 16 to the peripheral core
region 24. Thus, in such cases, the peripheral core region 24 may
further include selected ones of the bred fissile nuclear fuel
assemblies 18b having at least a predetermined burnup level.
[0077] It will further be appreciated that, as discussed above,
some of the fertile nuclear fuel assemblies 20b in the peripheral
core region 24 will be converted to the bred fissile nuclear fuel
assemblies 18b. As also discussed above, the fertile nuclear fuel
assemblies 20b may have been subject to neutron flux levels in the
peripheral core region 24 below neutron flux levels in the central
core region 16 to which the fertile nuclear fuel assemblies 20a
have been subjected. As a result, the peripheral core region 24 may
include ones of the bred fissile nuclear fuel assemblies 18b (that
is, converted from the fertile nuclear fuel assemblies 20b in the
peripheral core region 24) having less than a predetermined burnup
level.
[0078] During various stages of core life, ones of the neutron
absorber assemblies 26 may be moved by the in-vessel handling
system 28 among any of several locations in the peripheral core
region 24. The locations in the peripheral core region 24 may
include predetermined radial locations in the peripheral core
region 24 that are selectable based upon a predetermined burnup
level of nuclear fuel assemblies 18 and 20 that are located in the
peripheral core region 24.
[0079] Toward end-of-life (EOL), the enriched fissile nuclear fuel
assemblies 18a may have undergone sufficient burnup such that the
enriched fissile nuclear fuel assemblies 18a have been shuffled
(moved) from the central core region 16 to the peripheral core
region 24. Thus, toward EOL the fissile nuclear fuel assemblies 18
that are located in the central core region 16 are the bred fissile
nuclear fuel assemblies 18b. Therefore, toward EOL, the fissile
nuclear fuel assemblies 18 (in the central core region 16) include
the bred fissile nuclear fuel assemblies 18b, and the peripheral
core region 24 includes enriched fissile nuclear fuel assemblies
18a having at least a predetermined burnup level.
[0080] It will be appreciated that, toward EOL, the peripheral core
region may also include bred fissile fuel assemblies 18b. Some of
the bred fissile nuclear fuel assemblies 18b in the peripheral core
region 24 may include selected ones of the bred fissile nuclear
fuel assemblies 18b that have been shuffled from the central core
region 16 to the peripheral core region 24 and that have at least a
predetermined burnup level. It will further be appreciated that
some others of the bred fissile nuclear fuel assemblies 18b in the
peripheral core region 24 may include (i) ones of the bred fissile
nuclear fuel assemblies 18b that have been shuffled from the
central core region 16 to the peripheral core region 24 that have
less than a predetermined burnup level and/or (ii) ones of the bred
fissile nuclear fuel assemblies 18b that have been converted from
ones of the fertile nuclear fuel assemblies 20b (that have resided
in the peripheral core region 24) that have less than a
predetermined burnup level.
[0081] Embodiments of the nuclear fission reactor 10 lend
themselves to fuel recycling. Some embodiments of the nuclear
fission reactor 10 may discharge their fuel at an average burnup of
approximately 15% of initial heavy metal atoms, with axial peaking
making the peak burnup in the range of 28-32%. Meanwhile, fissile
material bred in various embodiments of the nuclear fission reactor
10 of nominal `smear` composition may remain critical to over 40%
average burnup (even without any fission product removal) via melt
refining. Including the effect of periodic melt refilling can allow
burn-ups exceeding 50% to be achieved. Therefore, fuel discharged
from a first generation nuclear fission reactor 10 still has most
of its potential life remaining from a neutronic standpoint (even
before any "life extension" associated with thermal removal of
fission products during recladding is considered) and would be
available for re-use without any need for chemical
reprocessing.
[0082] To that end and as mentioned above, in some embodiments
(such as in later nth-of-a-kind members of a fleet of the nuclear
fission reactors 10), at BOL at least some of the fissile material
in the fissile nuclear fuel assemblies 18a may include Pu.sup.239
(that has been bred in previous members of the fleet of nuclear
fission reactors 10). In some such cases, one or more of the
fissile nuclear fuel assemblies 18 may include fissile material
that has been discharged from a nuclear fission reactor. Moreover,
in some of these cases the fissile nuclear fuel assemblies 18 that
include fissile material that has been discharged from a nuclear
fission reactor may include re-clad fissile fuel assemblies.
[0083] In such embodiments, the fissile nuclear fuel assemblies 18
may be recycled via fuel recladding--a process in which the old
clad is removed and the used fuel is refabricated into new fuel.
The fissile fuel material is recycled through thermal and physical
(but not chemical) processes. The used fuel assemblies are
disassembled into individual fuel rods which then have their
cladding mechanically cut away. The used fuel then undergoes a high
temperature (1300-1400.degree. C.) melt refining process in an
inert atmosphere which separates many of the fission products from
the fuel in two main ways: (i) the volatile and gaseous fission
products (e.g., Br, Kr, Rb, Cd, I, Xe, Cs) simply escape; while
(ii) the more than 95% of the chemically-reactive fission products
(e.g., Sr, Y, Te, Ba, and rare earths) become oxidized in a
reaction with the zirconia crucible and are readily separated. The
melt-refined fuel can then be cast or extruded into new fuel slugs,
placed into new cladding with a sodium bond, and integrated into
new fuel assemblies.
[0084] Referring additionally to FIG. 3, an illustrative nuclear
fuel assembly (regardless of whether it is a fissile nuclear fuel
assembly 18 or a fertile nuclear fuel assembly 20) includes fuel
pins (or fuel rods or fuel elements) 56. In various embodiments,
the fuel pins 56 include metal fuel (again, regardless of whether
the fuel is fissile fuel or fertile fuel). It will be appreciated
that metal fuel offers high heavy metal loadings and excellent
neutron economy, which is desirable for the breed-and-burn process
in the nuclear fission reactor core 12.
[0085] In various embodiments the metal fuel may be alloyed with
about 3% to about 8% zirconium to dimensionally stabilize the alloy
during irradiation and to inhibit low-temperature eutectic and
corrosion damage of the cladding. A sodium thermal bond fills the
gap that exists between the alloy fuel and the inner wall of the
clad tube to allow for fuel swelling and to provide efficient heat
transfer which keeps the fuel temperatures low. Individual fuel
pins 56 may have a thin wire 58 from about 0.8 mm diameter to about
1.6 mm diameter helically wrapped around the circumference of the
clad tubing to provide coolant space and mechanical separation of
individual fuel pins 56 within the housing of the fuel assembly 18
and 20 (that also serves as the coolant duct). In various
embodiments the cladding, wire wrap, and housing may be fabricated
from ferritic-martensitic steel because of its irradiation
performance as indicated by a body of empirical data.
[0086] Large power differences between the fissile nuclear fuel
assemblies 18 in the central core region 16 and the fertile nuclear
fuel assemblies 20a and/or 20b in the peripheral core region 24
entail significant differences in assembly flow distribution to
match flow to power and thus outlet temperature. In various
embodiments this flow distribution is accomplished through
orifices, such as a combination of fixed and variable orifices,
which make it possible to optimize primary coolant flow
proportionally to predicted assembly power.
[0087] Referring now to FIG. 4A, in various embodiments orifices
60, such as fixed orifices, are installed in fuel assembly flow
receptacles 62 below the nuclear fission reactor core 12. The fuel
assembly flow receptacles 62 mate with seats 64 in a core support
grid plate 66 and contain sockets 68 where the nuclear fuel
assemblies 18 and 20 are inserted.
[0088] The fuel assembly flow receptacles 62 have orifices 60 that
may be used to match flow to power generated in the nuclear fuel
assemblies. For example, the fuel assembly flow receptacles 62
under the peripheral core region 24 have very high-pressure-drop
orifices 60 to minimize the flow into very low-power fertile
nuclear fuel assemblies 20. On the other hand, the fuel assembly
flow receptacles 62 below the nuclear fuel assemblies 18 and 20 in
the central core region 16 may be divided into several groups
having orifices 60 ranging from very low resistance to higher
resistance to match the radial power profile in the central core
region 16.
[0089] In addition to the fixed orifices 60, in some embodiments
each nuclear fission fuel assembly 18 and 20 may have an ability to
adjust assembly flow by rotation during fuel shuffling operations
to enable minor flow adjustments at the assembly level, if
desired.
[0090] Thus, in some embodiments, the fuel assembly flow
receptacles 62 may define a group of reactor coolant flow orifices
60 in the central core region 16 and another group of reactor
coolant flow orifices 60 in the peripheral core region 24. The
group of reactor coolant flow orifices 60 in the central core
region 16 may includes reactor coolant flow orifice groups. In such
cases, flow rate through a selected one of the reactor coolant flow
orifice groups may be based upon a power profile at a radial
location of the selected one of the reactor coolant flow orifice
groups. Moreover, flow rate through the reactor coolant flow
orifices 60 in the peripheral core region 24 may include a
predetermined flow rate based upon power level in the peripheral
core region 24.
[0091] In various embodiments, the orifices 60 include fixed
orifices. In other embodiments, variable orifices may be provided
(via rotation of the nuclear fuel assemblies 18 and 20). In some
other embodiments, the orifices 60 may include fixed orifices and
variable orificing may also be provided (via rotation of the
nuclear fuel assemblies 18 and 20).
[0092] In some other embodiments and referring additionally to FIG.
4B, a core support grid plate 66a may be "stepped". That is, the
stepped core support grid plate 66a may be used to offset the
nuclear fuel assemblies 18 and 20 axially. As such, the stepped
core support grid plate 66a allows changing position of the nuclear
fuel assemblies 18 and 20 in the axial direction as a function of
their position in the radial direction.
[0093] Utilization of fuel in the nuclear fission reactor core 12
may be further increased by offsetting the assemblies axially (in
addition to shuffling the nuclear fuel assemblies 18 and 20
radially). It will be appreciated that relative neutron flux
distribution is higher in the central axial zone of the nuclear
fission reactor core 12 than in the axial extents of the nuclear
fission reactor core 12, as shown by curve 67. Such axially
offsetting can allow for fuel bred near the axial extents of the
fertile nuclear fuel assemblies 20 to be moved closer to (or, if
needed, further from) the central axial zone of the nuclear fission
reactor core 12. Such offsetting can thus allow for a higher degree
of control of burn-up in the axial dimension, which can further
help yield higher fuel utilization.
[0094] In some embodiments the stepped core support grid plate 66a
may include a single axially-sectioned assembly. In some
embodiments the level of offset could be fixed and could include a
pre-determined fuel management strategy. In some other embodiments
the level of offset may be altered through the use of spacers, such
as risers or shims or the like, that may be installed at the bottom
of the nuclear fuel assemblies 18 and 20 or directly onto the
stepped core support grid plate 66a.
[0095] Aspects of operation of embodiments of the nuclear fission
reactor core 12 will be explained.
[0096] It will be appreciated that various design features of
embodiments of the nuclear fission reactor core 10 can help
increase the maximum burnup and fluence the fuel can sustain before
the accumulation of fission products makes the fuel
subcritical.
[0097] For example, the fissile nuclear fuel assemblies 18 in the
central core region 16 are surrounded by subcritical feed fuel
(that is, the fertile nuclear fuel assemblies 20 in the central
core region 16 and in the peripheral core region 24), which absorbs
leakage neutrons and uses them to breed new fuel. It will be
appreciated by those of skill in the art of nuclear reactor design
and operation that past a thickness of feed fuel surrounding the
central core region 16 of approximately 70 cm (or, depending upon
size of the fertile nuclear fuel assemblies 20, about 5 assembly
rows) the fraction of neutrons leaking from the nuclear fission
reactor core 12 is reduced toward zero.
[0098] Such neutron conserving features accomplish two things.
First, they minimize the burnup and fluence entailed in achieving
breeding-and-fissioning wave propagation, which in turn eases
material degradation issues and enables embodiments of the nuclear
fission reactor 10 to be made with existing materials. Second, they
increase the maximum burnup and fluence the fuel can sustain before
the accumulation of fission products makes the fuel subcritical.
This second point is illustrated in FIG. 6A.
[0099] Referring additionally to FIG. 6A, a graph 70 graphs
reactivity versus burnup for illustrative embodiments of the
nuclear fission reactor core 12 along a curve 72. The graph 70
compares the reactivity evolution of feed fuel in illustrative
embodiments of the nuclear fission reactor core 12 (illustrated
along the curve 72) with the reactivity evolution of enriched fuel
from a typical sodium fast reactor which is illustrated along a
curve 74. The enriched fuel from a typical sodium fast reactor is
modeled as having SuperPhenix fuel, coolant and structure volume
fractions with 75% smear density, and an initial enrichment of 16%.
As is known, typical sodium fast reactor fuel must start at a high
enrichment to achieve criticality, and the excess reactivity of
fresh fuel is lost to control elements, absorption in the breeding
blanket, and leakage from the core. As shown by the curve 74, the
typical sodium fast reactor fuel quickly loses reactivity as
U.sup.235 is depleted, and it becomes subcritical at approximately
310 MWd/kgHM burnup. At the point where the typical sodium fast
reactor fuel becomes subcritical, about half of the total fissions
are due to U.sup.235, and the utilization fraction of U.sup.238 is
less than 20%.
[0100] Meanwhile, as shown by the curve 72, feed fuel in
embodiments of the nuclear fission reactor core 12 begins as
subcritical fertile fuel in the fertile nuclear fuel assemblies 20
and gains reactivity as Pu.sup.239 is bred in. Once the fuel
becomes critical, excess reactivity is offset by breeding
additional subcritical feed fuel (it will be noted that during the
first 50 MWd/kgHM of burn-up, the driver fuel makes the reactor
critical). A total fuel burnup of up to 400 MWd/kgHM or higher can
be achieved before the fuel becomes subcritical, and since the fuel
begins as nearly all U.sup.238, the U.sup.238 utilization fraction
can be greater than 40%.
[0101] Referring additionally to FIG. 6B, a graph 76 of reactivity
versus burnup shows effects of periodic thermal removal of fission
products along a curve 78. The graph 76 also includes the graph 72
for feed fuel without thermal removal of fission products.
Embodiments of the nuclear fission reactor core 12 are presently
designed to discharge their fuel at an average burnup of
approximately 15% of initial heavy metal atoms, with axial peaking
making the peak burnup in the range of 28-32%. Meanwhile, as shown
by the curve 72, feed fuel bred in an illustrative nuclear fission
reactor core 12 of nominal `smear` composition remains critical to
over 40% average burnup, even without any fission product removal
via melt refining. Including the effect of periodic melt refining,
as shown by the curve 78, allows burn-ups exceeding 50% to be
achieved. Therefore, fuel discharged from a first generation
nuclear fission reactor 10 still has most of its potential life
remaining from a neutronic standpoint (even before any "life
extension" associated with thermal removal of fission products
during recladding is considered) and would be available for reuse
without any need for chemical reprocessing.
[0102] Referring now to FIG. 7, a graph 80 illustrates plutonium
isotope evolution versus utilization of U.sup.238. At low
utilization, the plutonium produced is substantially all
Pu.sup.239, since operation begins with U.sup.238 and no plutonium.
At higher utilizations, the plutonium quality becomes increasingly
degraded as higher isotopes of plutonium are created. At the point
which the feed fuel's k-infinity falls below unity (as shown by the
curve 72 in FIGS. 6A and 6B), the fissile plutonium fraction is
under 70%, similar to reactor-grade plutonium from LWR spent fuel.
Additionally, the plutonium in spent fuel from embodiments of the
nuclear fission reactor 10 is contaminated to a much higher degree
with fission products, thereby making it more difficult to handle
and reprocess and less attractive for diversion to weapons
purposes.
[0103] Illustrative Methods
[0104] Following are a series of flowcharts depicting
implementations. For ease of understanding, the flowcharts are
organized such that the initial flowcharts present implementations
via an example implementation and thereafter the following
flowcharts present alternate implementations and/or expansions of
the initial flowchart(s) as either sub-component operations or
additional component operations building on one or more
earlier-presented flowcharts. Those having skill in the art will
appreciate that the style of presentation utilized herein (e.g.,
beginning with a presentation of a flowchart(s) presenting an
example implementation and thereafter providing additions to and/or
further details in subsequent flowcharts) generally allows for a
rapid and easy understanding of the various process
implementations. In addition, those skilled in the art will further
appreciate that the style of presentation used herein also lends
itself well to modular and/or object-oriented program design
paradigms.
[0105] Given by way of overview and referring now to FIG. 8A, a
method 100 is provided for operating a nuclear fission reactor. The
method 100 starts at a block 102. At a block 104 fissile nuclear
fuel material is fissioned in a plurality of fissile nuclear fuel
assemblies in a central core region of a nuclear fission reactor
core of a nuclear fission reactor. At a block 106 fissile material
is bred in ones of a plurality of fertile nuclear fuel assemblies
in the central core region of the nuclear fission reactor core. At
a block 108 selected ones of the plurality of fissile nuclear fuel
assemblies and selected ones and selected others of the plurality
of fertile nuclear fuel assemblies are shuffled in a manner that
establishes a standing wave of breeding fissile nuclear fuel
material and fissioning fissile nuclear fuel material. The method
100 stops at a block 110. Details will be set forth below by way of
non-limiting examples.
[0106] Referring to FIG. 8B, in some embodiments fissioning fissile
nuclear fuel material in a plurality of fissile nuclear fuel
assemblies in a central core region of a nuclear fission reactor
core of a nuclear fission reactor at the block 104 may include
generating in the central core region at least a predetermined
amount of power in the nuclear fission reactor core at a block
112.
[0107] Referring to FIG. 8C, in some embodiments neutrons may be
absorbed in a peripheral core region at a block 114.
[0108] Referring to FIG. 8D, in some embodiments absorbing neutrons
in a peripheral core region at the block 114 may include absorbing
neutrons in others of the plurality of fertile nuclear fuel
assemblies in the peripheral core region at a block 116.
[0109] Referring to FIG. 8E, in some embodiments absorbing neutrons
in others of the plurality of fertile nuclear fuel assemblies in
the peripheral core region at the block 116 may include breeding
fissile material in others of the plurality of fertile nuclear fuel
assemblies in the peripheral core region at a block 118.
[0110] Referring to FIG. 8F, in some embodiments absorbing neutrons
in a peripheral core region at the block 114 may include absorbing
neutrons in a plurality of neutron absorber assemblies in the
peripheral core region at a block 120.
[0111] Referring to FIG. 8G, in some embodiments absorbing neutrons
in a plurality of neutron absorber assemblies in the peripheral
core region at the block 120 may include absorbing neutrons in a
plurality of neutron absorber assemblies in the peripheral core
region such that power produced in the peripheral core region is
maintained below a predetermined power level at a block 122.
[0112] Referring to FIG. 8H, in some embodiments absorbing neutrons
in a peripheral core region at the block 114 may include absorbing
neutrons in others of the plurality of fertile nuclear fuel
assemblies in the peripheral core region and absorbing neutrons in
a plurality of neutron absorber assemblies in the peripheral core
region at a block 124.
[0113] Referring to FIG. 8I, in some embodiments at a block 126 the
nuclear fission reactor may be shut down before shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies.
[0114] Referring to FIG. 8J, in some embodiments shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies in a manner that establishes a standing
wave of breeding fissile nuclear fuel material and fissioning
fissile nuclear fuel material at the block 108 may include
shuffling selected ones of the plurality of fissile nuclear fuel
assemblies and selected ones and selected others of the plurality
of fertile nuclear fuel assemblies between the central core region
and the peripheral core region in a manner that establishes a
standing wave of breeding fissile nuclear fuel material and
fissioning fissile nuclear fuel material at a block 128.
[0115] Referring to FIG. 8K, in some embodiments shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies at the block 108 may include replacing
selected ones of the plurality of fissile nuclear fuel assemblies
of the central core region with selected ones of the plurality of
fertile nuclear fuel assemblies of the central core region and with
selected others of the plurality of fertile nuclear fuel assemblies
of the peripheral core region at a block 130.
[0116] Referring to FIG. 8L, in some embodiments shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies at the block 108 may include shuffling
selected ones of the plurality of fissile nuclear fuel assemblies
having a predetermined burnup level and selected ones and selected
others of the plurality of fertile nuclear fuel assemblies at a
block 132.
[0117] Referring to FIG. 8M, in some embodiments reactivity in the
central core region may be controlled at a block 134.
[0118] Referring to FIG. 8N, in some embodiments controlling
reactivity in the central core region at the block 134 may include
controlling reactivity in the central core region with a plurality
of movable reactivity control assemblies at a block 136.
[0119] Referring to FIG. 8O, in some embodiments controlling
reactivity in the central core region at the block 134 may include
shuffling selected ones of the plurality of fissile nuclear fuel
assemblies and selected ones and selected others of the plurality
of fertile nuclear fuel assemblies at a block 138.
[0120] Referring to FIG. 8P, in some embodiments controlling
reactivity in the central core region at the block 134 may include
controlling reactivity in the central core region with a plurality
of movable reactivity control assemblies and shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies at a block 140.
[0121] Referring to FIG. 8Q, in some embodiments reactor coolant
may be flowed through a first plurality of reactor coolant flow
orifices in the central core region at a block 142 and reactor
coolant may be flowed through a second plurality of reactor coolant
flow orifices in the peripheral core region at a block 144.
[0122] Referring to FIG. 8R, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 142 may include flowing
reactor coolant through a plurality of reactor coolant flow orifice
groups in the central core region at a block 146. In some
embodiments, flow rate through a selected one of the plurality of
reactor coolant flow orifice groups may be based upon a power
profile at a radial location of the selected one of the plurality
of reactor coolant flow orifice groups. In some embodiments, flow
rate through the second plurality of reactor coolant flow orifices
may include a predetermined flow rate based upon power level in the
peripheral core region.
[0123] Referring to FIG. 8S, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 142 and flowing reactor
coolant through a second plurality of reactor coolant flow orifices
in the peripheral core region at the block 144 may include
maintaining substantially steady flow of reactor coolant through
ones of the first and second pluralities of reactor coolant flow
orifices at a block 148.
[0124] Referring to FIG. 8T, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 142 and flowing reactor
coolant through a second plurality of reactor coolant flow orifices
in the peripheral core region at the block 144 may include varying
flow of reactor coolant through others of the first and second
pluralities of reactor coolant flow orifices at a block 150.
[0125] Referring to FIG. 8U, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 142 and flowing reactor
coolant through a second plurality of reactor coolant flow orifices
in the peripheral core region at the block 144 may include
maintaining substantially steady flow of reactor coolant through
ones of the first and second pluralities of reactor coolant flow
orifices and varying flow of reactor coolant through others of the
first and second pluralities of reactor coolant flow orifices at a
block 152.
[0126] Referring to FIG. 8V, in some embodiments flow of reactor
coolant may be varied through at least one of the shuffled nuclear
fuel assemblies at a block 154.
[0127] Referring to FIG. 8W, in some embodiments varying flow of
reactor coolant through at least one of the shuffled nuclear fuel
assemblies at the block 154 may include rotating at least one of
the shuffled nuclear fuel assemblies at a block 156.
[0128] Referring to FIG. 8X, in some embodiments ones of the
plurality of neutron absorber assemblies may be moved among a
plurality of locations in the peripheral core region at a block
158. In some embodiments, the plurality of locations in the
peripheral core region may include a plurality of predetermined
radial locations in the peripheral core region that are selectable
based upon a predetermined burnup level of ones of the fissile
nuclear fuel assemblies that have been shuffled into the peripheral
core region.
[0129] Referring to FIG. 8Y, in some embodiments at a block 160
ones of the plurality of fissile nuclear fuel assemblies and ones
and others of the plurality of fertile nuclear fuel assemblies may
be selected for shuffling in a manner that establishes a standing
wave of breeding fissile nuclear fuel material and fissioning
fissile nuclear fuel material. In some embodiments selecting ones
of the plurality of fissile nuclear fuel assemblies and ones and
others of the plurality of fertile nuclear fuel assemblies for
shuffling in a manner that establishes a standing wave of breeding
fissile nuclear fuel material and fissioning fissile nuclear fuel
material may be based upon at least one operational datum chosen
from neutron flux data, fuel assembly outlet temperature, and fuel
assembly flow rate.
[0130] Given by way of overview and referring now to FIG. 9A, a
method 200 is provided for operating a nuclear fission reactor. The
method 200 starts at a block 202. At a block 204 fissile nuclear
fuel material is fissioned in a plurality of fissile nuclear fuel
assemblies in a central core region of a nuclear fission reactor
core of a nuclear fission reactor. At a block 206 fissile material
is bred in ones of a plurality of fertile nuclear fuel assemblies
in the central core region of the nuclear fission reactor core. At
a block 208 reactivity in the central core region is controlled. At
a block 210 neutrons are absorbed in a peripheral core region. At a
block 212 selected ones of the plurality of fissile nuclear fuel
assemblies and selected ones and selected others of the plurality
of fertile nuclear fuel assemblies are shuffled in a manner that
establishes a standing wave of breeding fissile nuclear fuel
material and fissioning fissile nuclear fuel material. The method
200 stops at a block 214. Details will be set forth below by way of
non-limiting examples.
[0131] Referring to FIG. 9B, in some embodiments fissioning fissile
nuclear fuel material in a plurality of fissile nuclear fuel
assemblies in a central core region of a nuclear fission reactor
core of a nuclear fission reactor at the block 204 may include
generating in the central core region at least a predetermined
amount of power in the nuclear fission reactor core at a block
216.
[0132] Referring to FIG. 9C, in some embodiments absorbing neutrons
in a peripheral core region at the block 210 may include absorbing
neutrons in others of the plurality of fertile nuclear fuel
assemblies in the peripheral core region at a block 218.
[0133] Referring to FIG. 9D, in some embodiments absorbing neutrons
in others of the plurality of fertile nuclear fuel assemblies in
the peripheral core region at the block 218 may include breeding
fissile material in others of the plurality of fertile nuclear fuel
assemblies in the peripheral core region at a block 220.
[0134] Referring to FIG. 9E, in some embodiments absorbing neutrons
in a peripheral core region at the block 210 may include absorbing
neutrons in a plurality of neutron absorber assemblies in the
peripheral core region at a block 222.
[0135] Referring to FIG. 9F, in some embodiments absorbing neutrons
in a plurality of neutron absorber assemblies in the peripheral
core region at the block 222 may include absorbing neutrons in a
plurality of neutron absorber assemblies in the peripheral core
region such that power produced in the peripheral core region is
maintained below a predetermined power level at a block 224.
[0136] Referring to FIG. 9G, in some embodiments absorbing neutrons
in a peripheral core region at the block 210 may include absorbing
neutrons in others of the plurality of fertile nuclear fuel
assemblies in the peripheral core region and absorbing neutrons in
a plurality of neutron absorber assemblies in the peripheral core
region at a block 226.
[0137] Referring to FIG. 9H, in some embodiments at a block 228 the
nuclear fission reactor may be shut down before shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies between the central core region and the
peripheral core region.
[0138] Referring to FIG. 9I, in some embodiments shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies in a manner that establishes a standing
wave of breeding fissile nuclear fuel material and fissioning
fissile nuclear fuel material at the block 212 may include
shuffling selected ones of the plurality of fissile nuclear fuel
assemblies and selected ones and selected others of the plurality
of fertile nuclear fuel assemblies between the central core region
and the peripheral core region in a manner that establishes a
standing wave of breeding fissile nuclear fuel material and
fissioning fissile nuclear fuel material at a block 230.
[0139] Referring to FIG. 9J, in some embodiments shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies at the block 212 may include replacing
selected ones of the plurality of fissile nuclear fuel assemblies
of the central core region with selected ones of the plurality of
fertile nuclear fuel assemblies of the central core region and with
selected others of the plurality of fertile nuclear fuel assemblies
of the peripheral core region at a block 232.
[0140] Referring to FIG. 9K, in some embodiments shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies at the block 212 may include shuffling
selected ones of the plurality of fissile nuclear fuel assemblies
having a predetermined burnup level and selected ones and selected
others of the plurality of fertile nuclear fuel assemblies at a
block 234.
[0141] Referring to FIG. 9L, in some embodiments controlling
reactivity in the central core region at the block 208 may include
controlling reactivity in the central core region with a plurality
of movable reactivity control assemblies at a block 236.
[0142] Referring to FIG. 9M, in some embodiments controlling
reactivity in the central core region at the block 208 may include
shuffling selected ones of the plurality of fissile nuclear fuel
assemblies and selected ones and selected others of the plurality
of fertile nuclear fuel assemblies at a block 238.
[0143] Referring to FIG. 9N, in some embodiments controlling
reactivity in the central core region at the block 208 may include
controlling reactivity in the central core region with a plurality
of movable reactivity control assemblies and shuffling selected
ones of the plurality of fissile nuclear fuel assemblies and
selected ones and selected others of the plurality of fertile
nuclear fuel assemblies at a block 240.
[0144] Referring to FIG. 9O, in some embodiments reactor coolant
may be flowed through a first plurality of reactor coolant flow
orifices in the central core region at a block 242 and reactor
coolant may be flowed through a second plurality of reactor coolant
flow orifices in the peripheral core region at a block 244.
[0145] Referring to FIG. 9P, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 242 may include flowing
reactor coolant through a plurality of reactor coolant flow orifice
groups in the central core region at a block 246. In some
embodiments flow rate through a selected one of the plurality of
reactor coolant flow orifice groups may be based upon a power
profile at a radial location of the selected one of the plurality
of reactor coolant flow orifice groups. In some embodiments flow
rate through the second plurality of reactor coolant flow orifices
may include a predetermined flow rate based upon power level in the
peripheral core region.
[0146] Referring to FIG. 9Q, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 242 and flowing reactor
coolant through a second plurality of reactor coolant flow orifices
in the peripheral core region at the block 244 may include
maintaining substantially steady flow of reactor coolant through
ones of the first and second pluralities of reactor coolant flow
orifices at a block 248.
[0147] Referring to FIG. 9R, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 242 and flowing reactor
coolant through a second plurality of reactor coolant flow orifices
in the peripheral core region at the block 244 may include varying
flow of reactor coolant through others of the first and second
pluralities of reactor coolant flow orifices at a block 250.
[0148] Referring to FIG. 9S, in some embodiments flowing reactor
coolant through a first plurality of reactor coolant flow orifices
in the central core region at the block 242 and flowing reactor
coolant through a second plurality of reactor coolant flow orifices
in the peripheral core region at the block 244 may include
maintaining substantially steady flow of reactor coolant through
ones of the first and second pluralities of reactor coolant flow
orifices and varying flow of reactor coolant through others of the
first and second pluralities of reactor coolant flow orifices at a
block 252.
[0149] Referring to FIG. 9T, in some embodiments flow of reactor
coolant through at least one of the shuffled nuclear fuel
assemblies may be varied at a block 254.
[0150] Referring to FIG. 9U, in some embodiments varying flow of
reactor coolant through at least one of the shuffled nuclear fuel
assemblies at the block 254 may include rotating at least one of
the shuffled nuclear fuel assemblies at a block 256.
[0151] Referring to FIG. 9V, in some embodiments ones of the
plurality of neutron absorber assemblies may be moved among a
plurality of locations in the peripheral core region at a block
258. In some embodiments the plurality of locations in the
peripheral core region may include a plurality of predetermined
radial locations in the peripheral core region that are selectable
based upon a predetermined burnup level of ones of the fissile
nuclear fuel assemblies that have been shuffled into the peripheral
core region.
[0152] Referring to FIG. 9W, in some embodiments at a block 260
ones of the plurality of fissile nuclear fuel assemblies and ones
and others of the plurality of fertile nuclear fuel assemblies may
be selected for shuffling in a manner that establishes a standing
wave of breeding fissile nuclear fuel material and fissioning
fissile nuclear fuel material. In some embodiments selecting ones
of the plurality of fissile nuclear fuel assemblies and ones and
others of the plurality of fertile nuclear fuel assemblies for
shuffling in a manner that establishes a standing wave of breeding
fissile nuclear fuel material and fissioning fissile nuclear fuel
material may be based upon at least one operational datum chosen
from neutron flux data, fuel assembly outlet temperature, and fuel
assembly flow rate.
[0153] Given by way of overview and referring now to FIG. 10A, a
method 300 is provided for managing excess reactivity in a nuclear
fission reactor. The method 300 starts at a block 302. At a block
304, criticality with a positive quantity of reactivity is achieved
in a central core region of a reactor core of a nuclear fission
reactor. At a block 306 the quantity of reactivity is increased
until a predetermined burnup level is achieved in selected ones of
fuel assemblies in the reactor core. At a block 308 the increase in
reactivity is compensated for. The method 300 stops at a block 310.
Details will be set forth below by way of non-limiting
examples.
[0154] Referring to FIG. 10B, in some embodiments increasing the
quantity of reactivity until a predetermined burnup level is
achieved in selected ones of fuel assemblies in the reactor core at
the block 306 may include monotonically increasing the quantity of
reactivity until a predetermined burnup level is achieved in
selected ones of fuel assemblies in the reactor core at a block
312.
[0155] Referring to FIG. 10C, in some embodiments increasing the
quantity of reactivity until a predetermined burnup level is
achieved in selected ones of fuel assemblies in the reactor core at
the block 306 may include increasing amount of fissile material in
ones of the fuel assemblies of the reactor core until a
predetermined burnup level is achieved in selected ones of fuel
assemblies in the reactor core at a block 314.
[0156] Referring to FIG. 10D, in some embodiments increasing amount
of fissile material in ones of the fuel assemblies of the reactor
core until a predetermined burnup level is achieved in selected
ones of fuel assemblies in the reactor core at the block 314 may
include breeding fissile fuel material from fertile fuel material
at a block 316.
[0157] Referring to FIG. 10E, in some embodiments compensating for
the increase in reactivity at the block 308 may include inserting
neutron absorbing material into the central core region at a block
318.
[0158] Referring to FIG. 10F, in some embodiments inserting neutron
absorbing material into the central core region at the block 318
may include inserting control rods into the central core region at
a block 320.
[0159] Referring to FIG. 10G, in some embodiments inserting neutron
absorbing material into the central core region at the block 318
may include replacing selected fissile fuel assemblies in the
central core region with fertile fuel assemblies from a peripheral
core region of the reactor core at a block 322.
[0160] Referring to FIG. 10H, in some embodiments inserting neutron
absorbing material into the central core region at the block 318
may include inserting control rods into the central core region and
replacing selected fissile fuel assemblies in the central core
region with fertile fuel assemblies from a peripheral core region
of the reactor core at a block 324.
[0161] All of the above U.S. patents, U.S. patent application
publications, U.S. patent applications, foreign patents, foreign
patent applications and non-patent publications referred to in this
specification and/or listed in any Application Data Sheet, are
incorporated herein by reference, to the extent not inconsistent
herewith.
[0162] With respect to the use of substantially any plural and/or
singular terms herein, those having skill in the art can translate
from the plural to the singular and/or from the singular to the
plural as is appropriate to the context and/or application. The
various singular/plural permutations are not expressly set forth
herein for sake of clarity.
[0163] The herein described subject matter sometimes illustrates
different components contained within, or connected with, different
other components. It is to be understood that such depicted
architectures are merely exemplary, and that in fact many other
architectures may be implemented which achieve the same
functionality. In a conceptual sense, any arrangement of components
to achieve the same functionality is effectively "associated" such
that the desired functionality is achieved. Hence, any two
components herein combined to achieve a particular functionality
can be seen as "associated with" each other such that the desired
functionality is achieved, irrespective of architectures or
intermedial components. Likewise, any two components so associated
can also be viewed as being "operably connected", or "operably
coupled," to each other to achieve the desired functionality, and
any two components capable of being so associated can also be
viewed as being "operably couplable," to each other to achieve the
desired functionality. Specific examples of operably couplable
include but are not limited to physically mateable and/or
physically interacting components, and/or wirelessly interactable,
and/or wirelessly interacting components, and/or logically
interacting, and/or logically interactable components.
[0164] In some instances, one or more components may be referred to
herein as "configured to," "configured by," "configurable to,"
"operable/operative to," "adapted/adaptable," "able to,"
"conformable/conformed to," etc. Those skilled in the art will
recognize that such terms (e.g. "configured to") can generally
encompass active-state components and/or inactive-state components
and/or standby-state components, unless context requires
otherwise.
[0165] While particular aspects of the present subject matter
described herein have been shown and described, it will be apparent
to those skilled in the art that, based upon the teachings herein,
changes and modifications may be made without departing from the
subject matter described herein and its broader aspects and,
therefore, the appended claims are to encompass within their scope
all such changes and modifications as are within the true spirit
and scope of the subject matter described herein. It will be
understood by those within the art that, in general, terms used
herein, and especially in the appended claims (e.g., bodies of the
appended claims) are generally intended as "open" terms (e.g., the
term "including" should be interpreted as "including but not
limited to," the term "having" should be interpreted as "having at
least," the term "includes" should be interpreted as "includes but
is not limited to," etc.). It will be further understood by those
within the art that if a specific number of an introduced claim
recitation is intended, such an intent will be explicitly recited
in the claim, and in the absence of such recitation no such intent
is present. For example, as an aid to understanding, the following
appended claims may contain usage of the introductory phrases "at
least one" and "one or more" to introduce claim recitations.
However, the use of such phrases should not be construed to imply
that the introduction of a claim recitation by the indefinite
articles "a" or "an" limits any particular claim containing such
introduced claim recitation to claims containing only one such
recitation, even when the same claim includes the introductory
phrases "one or more" or "at least one" and indefinite articles
such as "a" or "an" (e.g., "a" and/or "an" should typically be
interpreted to mean "at least one" or "one or more"); the same
holds true for the use of definite articles used to introduce claim
recitations. In addition, even if a specific number of an
introduced claim recitation is explicitly recited, those skilled in
the art will recognize that such recitation should typically be
interpreted to mean at least the recited number (e.g., the bare
recitation of "two recitations," without other modifiers, typically
means at least two recitations, or two or more recitations).
Furthermore, in those instances where a convention analogous to "at
least one of A, B, and C, etc." is used, in general such a
construction is intended in the sense one having skill in the art
would understand the convention (e.g., "a system having at least
one of A, B, and C" would include but not be limited to systems
that have A alone, B alone, C alone, A and B together, A and C
together, B and C together, and/or A, B, and C together, etc.). In
those instances where a convention analogous to "at least one of A,
B, or C, etc." is used, in general such a construction is intended
in the sense one having skill in the art would understand the
convention (e.g., "a system having at least one of A, B, or C"
would include but not be limited to systems that have A alone, B
alone, C alone, A and B together, A and C together, B and C
together, and/or A, B, and C together, etc.). It will be further
understood by those within the art that typically a disjunctive
word and/or phrase presenting two or more alternative terms,
whether in the description, claims, or drawings, should be
understood to contemplate the possibilities of including one of the
terms, either of the terms, or both terms unless context dictates
otherwise. For example, the phrase "A or B" will be typically
understood to include the possibilities of "A" or "B" or "A and
B."
[0166] With respect to the appended claims, those skilled in the
art will appreciate that recited operations therein may generally
be performed in any order. Also, although various operational flows
are presented in a sequence(s), it should be understood that the
various operations may be performed in other orders than those
which are illustrated, or may be performed concurrently. Examples
of such alternate orderings may include overlapping, interleaved,
interrupted, reordered, incremental, preparatory, supplemental,
simultaneous, reverse, or other variant orderings, unless context
dictates otherwise. Furthermore, terms like "responsive to,"
"related to," or other past-tense adjectives are generally not
intended to exclude such variants, unless context dictates
otherwise.
[0167] Those skilled in the art will appreciate that the foregoing
specific exemplary processes and/or devices and/or technologies are
representative of more general processes and/or devices and/or
technologies taught elsewhere herein, such as in the claims filed
herewith and/or elsewhere in the present application.
[0168] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the
following claims.
* * * * *
References