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ANL-7138 H 2 (fl(& ANL-7138
® Sl
Argonne JRationgl Laboratorp
CATALOG OF NUCLEAR REACTOR CONCEPTS
Part . Homogeneous and
Quasi-homogeneous Reactors
Section IM. Reactors Fueled with
Liquid Metals
by
Charles E. Teeter, James A. Lecky,
and John H. Martens
i
ANNOUNCEMENT
RELEASED TOR 4
G TBNCE ARSTRACTS \
IN ? G !-L}R i ”0’“““‘_‘___—410—""
——
e
DISCLAIMER
This report was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor any agency Thereof, nor any of their employees,
makes any warranty, express or implied, or assumes any legal
liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial product,
process, or service by trade name, trademark, manufacturer, or
otherwise does not necessarily constitute or imply its endorsement,
recommendation, or favoring by the United States Government or any
agency thereof. The views and opinions of authors expressed herein
do not necessarily state or reflect those of the United States
Government or any agency thereof.
DISCLAIMER
Portions of this document may be illegible In
electronic image products. Images are produced
from the best available original document.
LEGAL NOTICE
This report was prepared as an account of Government sponsored work. Neither the United
States, nor the Commission, nor any person acting on behalf of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect to the accu-
racy, completeness, or usefulness of the information contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; u:
B. Assumes any liabilities with respect to the use of, or for damages resulliug from the
use of any information, apparatus, method, or process disclosed in this report.
As used in the above, ‘‘person acting on behalf of the Commission’’ includes any em-
ployee or contractor of the Commission, or employee of such contractor, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to, any information pursuant to his employment or contract
with the Commission, or his employment with such contractor.
Printed in USA. Price $3.00. Available from the Clearinghouse for Federal
Scientific and Technical Information, National Bureau of Standards,
U. S. Department of Commerce, Springfield, Virginia
ANL-7138
Reactor Technology
, (TID-4500)
IN N-UCLEAR SCIBNCE ABSTRACTS -§ AEC Research and
: * . Development Report
: R‘ET.:M SED FOR ANNOUNC EMENT
Y-
ARGONNE NATIONAL LABORATORY CFSTI PRICES.
9700 South Cass Avenue : -
Argonne, Illinois 60439 . H.C. $5 00 ; MN, f ‘
[ )
CATALOG OF NUCLEAR REACTOR CONCEPTS
Part I. Homogeneous and Quasi-homogeneous Reactors
Section IV. Reactors Fueled with Liquid Metals
by
Charles E. Teeter, James A. Lecky,
and John H. Martens
Technical Publications De partment
January 1966
Operated by The University of Chicago
under
Contract W-31-109-eng-38
with the
U. S. Atomic Energy Commission
e
TABLE OF CONTENTS
Page
Preface . . . . . . . e 5
Plan of Catalog of Nuclear Reactor Concepts . ........ e 6
List of Reactor Concepts..... . ........................ 7
SECTION IV. REACTQRS FIUIELED WITH LIQUID METALS ... .. 13
Chapter 1. Introduction; ............... I R 13
Chapter 2. Internally—cooféd. ReacCtors o . v v v v v v v e v e e s 19
Chapter 3. Externally-cooled Reactors .. ... ... ........ 59
-PREFACE
This report is an additional section in the 'Catallog of Nuclear Re-
actor Concepts that was begun with ANL-6892 and continued in ANL-6909
and ANL-7092. As in the previous reports, the material ‘is divided into
chapters, each with text and references, plus data sheets that cover the
individual concepts. The plan of the catalog, with the report numbers for
the sections already issued, is given on the following page. On p. 6 is a
list of the concepts covered in thls report, with the corresponding numbers
of chapters, and data. sheets., ~ . .z
Dr. Charles E. Teeter, formerly employed by the Chicago Opera-
tions Office at Argonne, Illinois, is now affiliated with the Southeastern
Massachusetts Technological Institute, New Bedford, Mass. Through a
consultantship arrangement with Argonne National Laboratory, he is con-
tinuing to help guide the organization and compilation of this catalog.
We wish to acknowledge the assistance of Miss Ellen Thro in the
compilation of this report. |
J.H.M,
January 1966
PLAN OF CATALOG OF REACTOR CONCEPTS
General Introduction
Part I. Homogeneous and Quasi-homogeneous Reactors
Section I.
Sectiqn II.
Section 1l1l.
Section IV.
Section V.
Section VI.
Particulate-fueled Reactors
Reactors Fueled with Homogeneous
Aqueous Solutions and Slurries
Reactors Fueled with Molten-salt
Solutions
Reactors Fueled with Liquid Metals
Reactors Fueled with Uranium Hexa-
fluoride, Gases, or Plasmas
Solid Homogeneous Reactors
Part II. Heterogeneous Reactors
Section I.
Section II.
Section III.
Section IV.
Section V.
Section VI.
Section VII. |
Section VIII.
Section IX.
Reactors Cooled by Liquid Metals
| Gas-cooled Reactors
Organic-cooled Reactors
Boiling Reactors
ANIL-6892
ANL-6892
ANL-6909
- ANL-7092
This report
Reactors Cooled by Supercritical Fluids
Water-cooled Reactors
Reactors Cooled by Other Fluids
Boiling~-water Reactors
Pressurized-water Reactors
Part III. Miscellaneous Reactor Concepts
REACTOR CONCEPTS DESCRIBED IN THIS REPORT
Name of Reactor | Chapter No. Data Sheet No. Page -
Slurry-fueled Fast Breeder 2 o 1 - 31
Bismuth-cooled, Liquid-metal-
fueled, Thermal Pile 2 2 31
Thermal Breeder Reactor 2 3 32
Bubbler-type Reactor 2 - 4 32
Rotating-plate Reactor 2 5 32
Heterogeneous Liquid Fuel, _
Beryllium Moderated Reactor -2 6 ' 33
Fast U%%*® Converter , 2 7 . .33
Externaily Fueled, Internally
Cooled PBR - 2 8 34
Pineapple Reactor = . 2 ' 9 34
Radiator Reactor with Solution : |
Fuel ' 2 10 35
Radiator Reactor with Slurry , ‘
Fuel _ 2 o 11 , 35
Radiator Reactor with Solution L .
Fuel and Solid Fertile Material .2 12 36
Rotating-graphite-ring, Liquid-
bismuth-uranium Reactor 2. 13 36
Reactor with Stationary Liquid
Uranium-Bismuth Fuel, Coole'd
with Sedium and Water 2 14 37
Internally-bismuth Cooled LMFR -
with Graphite Element (One-
region) 2 ' 15 37
Liquid.--Metal Fuel--Gas Cooled | | .
Reactor 2 16 38
Los Alamos Molten Plutonium : | |
Reactor Experiment (LAMPRE-I) . 2 17 39
Liquid--Metal Reactor for Ship ‘
Propulsion 2 18 40
Reactor for Rocket Propulsion, S
with Molten Metal Fuel : 2 19 . 40
st
REACTOR CONCEPTS DESCRIBED IN THIS REPORT
Name of Reactor Chapter No. Data Sheet No. .’ :Page
Reactor for Rocket Propulsion,
with Uranium Carbide Fuel 2 | ' 20 41
Liquid Metal Pile 2 21 . 4]
Thermal Molten-metal-fueled |
Reactor _ 2 _ .22 41
Fast Molten-metal-fueled , :
Reactor 2 23 42
Molten Fuel Fast Breeder
Reactor (FBR) _ 2 | 24 42
Fluid-fuel SGR 2 25 43
Liguid-metal-fueled, Gas- o |
cooled Reactor 2 . 26 » 43
Fast Breeder LMFR for Power 2 : 27 - 44
Uranium- Bismuth Fast Breeder 2 ' 28 44
"Teitel Design" Breeder : .
Reactor 2 ' 29 45
Gas-cooled, Liguid-metal _
Reactor . . 2 30 45
Internally Cooled Liquid Metal
Fuel Reactor (Power Breeder) 2 31 46
Internally Cooled LMFR _
_ (Power Breeder) 2 32 46
Internally-cooled Experimental.
Liquid Metal Fuel Reactor, _
Alternative Design 2 33 47
Internally-cooled Experimental,
Liquid Metal Fuel Reactor,
Alternative Design 2 | 34 47
Internally-cooled LMFR with | |
Molybdenum Core Container 2 . - 35 48
Internally Gas Cooled LMFR 2 | 36 - 48
Internally Cooled LMTBR" 2 37 49 -
Liquid Metal Breeder Reactor:
(LIMB)
REACTOR CONCEPTS DESCRIBED IN THIS REPORT
"Name of Reactor Chapter No. Data Sheet No. .. Page -
Second Los Alamos Molten
Plutonium Reactor Experi-
ment (LAMPRE-II) 2 39 - | 51
| Fast Reactor Core Test
Facility 2 40 : 52
Hate.rogcncous Reactor wilh : |
Spherical Fuel Elements 2 41 - 53
Thermal Reactor with Spheric'al
Fuel Elements in Liquid Metal 2 . 42 : 54
Fast Reactor with Spherical : :
Fuel Elementsi in Liquid Metal 2 .43 54
Halban-Kowarsk: Molten- ‘ _ . _
metal Pile 3 : 1 69
Liiquid Fuel Circulating Reactor
for Aircraft Propulsion _ 3 2 . _ 69 -
Circulating-fuel Dispersed- | _
moderator Reactor 3 .3 69
Circulating-fuel, Reflector-
moderator Reactor 3 4 .70
Circulating Uranium- Bismuth
Fuel, Beryllium-moderated
Reactor 3 5 70
Circulating Fuel Reactor 3 ' 6 70
Circulating Uranium- Bismuth
Fuel Reactor (Solid Moderator) _
for Aircraft Propulsion 3 7 71
Circulating-fuel Reactor Fueled
with Uranium- Bismuth and :
Moderated with Water 3 ' 8 71
Circulating-fuel Reactor with |
Slurry Fuel ° 3 _ 9 72
Spherical Graphite-reflected C : |
LMFR | 3 ‘ 10 72
LMFR Single-region Burner 3. 11 . 73
'Liquid Metal Fuel Reactor with | _
- Recycled Plutonium - 3 ' 12 73
o -
10
REACTOR CONCEPTS DESCRIBED IN ’I'HIS REPORT
" Name of Reactor Chapter No. Data Sheet No. - .Page
Liquid Metal Fuel Reactor
Experiment I (LMFRE-I), First
Reference Design 3 13 74 .
Liquid Metal Fuel Reactor
Experiment I (LMFRE-I),
Final Reference Design 3 14 74
Externally-cooled, Single-fluid .
LMFR 3 15 75
High Temperature Integral -
Reactor (HTIR) 3 16 75
UO,- Liquid Metal Slurry
Reactor 3 17 76
Breeder with Uranium- Bismuth
Slurry 3 18 76
Mixed Fast and Thermal Pile 3 19 77
Molten-alloy Epithermal Plu-
tonium Pile 3 20 77
Uranium- Bismuth Fluid Fuel
Reactor (LFR-2) 3 21 78
Bismuth-cooled, Circulating-
slurry Reactor I 3 22 78
Bismuth-cooled, Circulating- |
fuel Reactor II 3 23 78
IMFRE-1 3 24 79
Liquid Metal Fuel Reactor
(Central Station Power Plant) 3 25 80
Multiregion Liquid Metal Fuel.
Reactor 3 26 81
Liquid Metal Fuel Reactor
Reference Design 3 27 . 82
Two-fluid LMFR Design 3 28 82
Liquid Metal Thorium Breeder ‘
Reactor (LMTBR) 3. - 29 83
Liquid Bismuth Breeder
Reactor (LBBR) ‘ 3 ' 30 84
REACTOR CONCEPTS DESCRIBED IN THIS REPORT
Name of Reactor Chapter No. Data Sheet No. . Page
Immiscible-liquid- cooled,
Fluid-fuel Reactor (Cen’tra.].)
- Station Power Reactor) 3 _ 31 85
LMFR-SGR Power Reactor 3 .32 85
City of Orlando (Florida)
Reactor . 3 .33 86
Uranium- Bismuth- Thorium -
System Reactor 3 _ 34 ‘ 86
Circulating-fuel LMFR 3 35 87
Reactor with Circulating :
UO,;-NaK Slurry Fuel ” 3 .36 87
Direct Contact Reactor. 3 _ .37 88
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LEFT BLANK
13
PART I. HOMOGENEOUS AND QUASI-HOMOGENEOUS REACTORS
SECTION IV. REACTORS FUELED WITH LIQUID METALS
Chapter 1. Introduction
Concepts in this section include reactors fueled with liquid fission-
able materials, as well as those fueled with solutions or dispersions of
fissionable materials in nonfissionable liquid metals. A solution of uranium
in a metal, particularly bismuth, has received the most attention. Disper-
sions of uranium oxide in bismuth or sodium, as well as molten plutonium
fuels, however, have also been investigated. Bismuth is a suitable fuel
medium because it will dissolve uranium, and it has a low cross section
for thermal neutrons. The solubility is, however, so limited that enriched
uranium must be used. Liquid metals can be fuels in either thermal or
fast reactors. Concepts for liquid-metal-fueled reactors, commonly re-
ferred to as LMFR concepts, are reviewed in Refs. 1 and 2,
The concepts in this section are divided according to the method of
cooling the reactor, internal or external (see below). A third classification,
integral or "pot," is frequently used. The only distinguishing feature of this
concept is that the reactor and primary heat exchanger are both in the pri-
mary reactor vessel. Because this feature is not basic, the integral re-
actors will be discussed according to the method of cooling.
In the internally-cooled reactors, Chapter 2, the liquid metal remains
in the core; the coolant, another fluid, flows through the core and out to an
external heat exchanger. Thus the core itself acts as a heat exchanger. In
this design, the fuel inventory is reduced, but the introduction of a second
- fluid complicates core design.
In externally-cooled reactors Chapter 3, the fuel circulates to an
external heat exchanger for cooling.
Liquid-metal-fueled reactors may be either one-fluid or two-fluid,
analogous to the one- and two-region reactors in Sections II and III, Part I,
of this Catalog. In the one-fluid reactors, the fuel carrier contains fertile,
material if breeding is desired, and there is no fertile blanket. In the two-
fluid reactors, a blanket of either solid or liquid fertlle rna.terla.l permits
higher conversion ratios.
In 1941, Halban and Kowarski suggested the use of a bismuth-
uranium alloy as a nuclear fuel.” The alloy would be circulated outside
the reactor for cooling in a heat exchanger. ’
14
Several workers in the wartime atomic-energy program advanced
ideas for reactors fueled with liquid metals, but most of the ideas were not
developed in enough detail for complete concepts. The advantages of a fuel
that could be used at high temperatures and low pressures and could be
easily reprocessed were rec:ognized'ea,rly,4 but development was hindered
by such difficulties as those arising in pumping liquid metals and by empha-
sis put on other concepts, which showed greater promise.
By 1944, a pile in which the fuel is dissolved in liquid bismuth and
the solution is circulated through the pile in bery'l‘lium tubes was being
studied.® The greatest difficulty expected was the removal of fission
products. In one 1945 concept, chunks of beryllium metal would be hung
inside of the pile container as a moderator.® Alternatively, the container
could be a cylinder that is filled with uranium dissolved in sodium and that
contains beryllium tubes through which the coolant stream flows.” Unfor-
tunately, uranium is even less soluble in liquid sodium than it is in liquid
bismuth. The possibility of an all-liquid pile containing a molten alloy of
plutonium and uranium, with some diluent, was discussed, but development
was hindered by lack of knowledge of the proper alloy.®
In 1947, Young summarized current developments of c:oncepts,.9
Fuels suggested included a slurry of uranium oxide in liquid metal and a
solution of uranium in a molten alloy.
Two more-advanced concepts were described in 1947 by Menke and
by Young. 10,11
Liquid-metal fuels have most of the advantages and disadvantages
previously discussed for aqueous and molten-salt fuels,! and they have
some of their own. Liquid-metal systems can operate at high temperatures
and low pressures and have good heat-transfer properties. They are com-
paratively free from radiation damage and bubble formation. Because of
their lack of inherent moderating properties, they can be used in either
thermal or fast reactors. As with other liquid fuels, removal of fission
products and reenrichment are simpler than with solid fuels. Wolfgang, !¢
for example, has suggested the use of fission recoil to separate fission
products and thus simplify waste removal. If a solid adsorbent, such as
alumina, were suspended in the fuel, fission products would be adsorbed
on the suspended solid rather than on the fuel. A mixed suspension of fuel
and adsorbent might be continuously processed by simple techniques. Such
a system has not, however, been developed. Among the disadvantages of -
these fuels are: the low heat capacity of metals as compared with that of
water; the greater difficulties of pumping liquid metals, some of which can
be avoided by the use of electromagnetic pumps; corrosion and mass-
transfer problems; and the low solubility of uranium in bismuth, requiring
‘the use of highly enriched fuel. Slurries are often used to attain high fuel
concentrations, but such difficulties as settling out of the solid and erosion
are encountered. The high melting point of metals makes startup of.a reactor
difficult. The sodium-potassium alloy is, however, liquid at room temperature.
15
Although several studies have been made on applying the liquid-
metal-fuel concept to aircraft propulsion, it has also been considered for
central- station power plants.
The problems of using liquid metals as fuels, which include selec-
tion of construction materials, heat transfer, special equipment, and engl-
neering aspects of operation, are discussed in Refs. 1 and 2,
Extensive developmental work in the United States on molten metals
as reactor fuels began with investigations at Brookhaven National Labora-
tory (BNL), the Babcock & Wilcox Cormupany, and the Los Alamos Scientific
Laboratory (LASL). Other organizations in which work was carried out on
liquid-metal fuels include the Knolls Atomic Power Laboratory (KAPL) of
the General Electric Company, the Argonne National Laboratory (ANL), and
the Fairchild Engine and Airplane Corporation (NEPA Project). At ANL
and KAPL, for example, slurries of uranium dioxide in molten sodium-
potassium were investigated. The development of a reactor fueled with
liquid metals began at BNL in 1947. In 1954, Babcock & Wilcox and other
companies prepared a reference design for a power reactor. In 1956,
this company contracted with the USAEC to design, construct, and operate
a Liquid Metal Fuel Reactor Experiment (LMFRE) and to do research and
development beyond that carried out at BNL.!
Several groups have evaluated liquid-metal-fueled reactors.
The Project Dynamo evaluation of 195337 concluded that the LMFR
was extremely attractive if it could be proven technically feasible. The first
comprehensive effort to determine general layouts and costs of a full-scale
LMFR power plant was made at BNL in March 1954. Pursuant to the re-
-quest of the USAEC, Brookhaven and Babcock & Wilcox arranged a formal
contract to determine the feasibility of the various LMFR types.“’ The re-
sults of this study favored the externally-cooled reactor for immediate
feasibility, but the integral type, either externally or internally cooled, for
long-range possibilities.'!7 A reevaluation by Babcock & Wilcox in 1957
reaffirmed the previous conclusion.®
In 1959, the USAEC sponsored a Fluid Fuel Reactors Task Force
to compare the three fluid-fuel reactor concepts then under development:
the agqueous-homogeneous, molten-salt, and liquid-metal-fuel reactors.
Although the task force found that the liquid-metal-fuel concept could be
developed into a "hold-own" (i.e., conversion ratio = 1) breeder with reason-
able power-cost potential, the development of a suitable container material
for the slurry fuel presented too many problems for the existing technology
for the LMFR to be considered technically feasible.
Three LMFR concepts were examined: an externally-cooled, one-
fluid breeder using a U*® 0,-ThO, slurry in bismuth; an externally-cooled,
open-type breeder using U-Bi solution for fuel and circulating ThBi,
"soluble" slurry in bismuth for fertile material; and an internally-cooled
16
breeder using a slowly-circulating suspension of U?3 and Th particles in
bismuth for fuel-fertile material, with a bismuth coolant circulating sep-
arately through a graphite core. In the third concept, fuel was circulated
solely to permit degassing and fuel addition. On the basis of rules estab-
lished by the task force, the first concept of the three--the externally-
cooled, one-fluid breeder--was chosen by Babcock & Wilcox as the most
attractive firsl-generation LMFR concept for low-cost power.2?
In 1960, the USAEC terminated the liquid-metal-fuel reactor pro-
gram, as well as the agqueous homogeneous progra.rn,?‘1 At LASL, however,
developmental work on fast reactors fueled with molten plutonium was
continued with a facility for testing cores for fasl reactoro.
10.
11.
12.
13.
14,
15.
16.
REFERLENCES
Fluid Fuel Reactors, J. A. Lane, H. G. MacPherson, and Frank Maslan,
eds., Addison-Wesley Publishing Co., Reading, Mass., 1958,
‘Reactor Handbook, 2nd ed. IV, Engineering, Stuart McLain and
J. H. Martens, eds., Interscience Publishers, a division of John Wiley &
Sons, N. Y., 1964.
H. Halban and L. Kowarski, Technological Aspects of Nuclear Chain
Reactors Used as a Source of Power, BR-7, Cambridge University,
England, Oct. 1941, ‘ ‘
F. H. Spedding, The Molten-Metal Fuel Reactor, ISC-318, Del., Ames
Laboratory, Iowa State University, June 1953. Decl., April 1958, -
Gale Young, in Physics Research Report for Month Ending Novem--
ber 25, 1944, CP-2426, p. 37, Metallurgical Laboratory, The University of
Chicago, Oct. 16-17, 1945,
Gale Young, in New Piles Meeting, CF- 3352, p. 18, Metallurgical
Laboratory, The University of Chicago, Oct. 16-17, 1945, Issued,"
Nov. 29, 1945, Decl., Feb. 15, 1956, - ‘
R. E. Connick, ibid., p. 23,
W. H. Zinn, ibid..
Gale Young, Some Notes on Power Piles, MonP - 190, Clinton Labora-
tories (now Oak Ridge National Laboratory) Oct. 30, 1947, '
J. R. Menke, Fast Piles, in Physics Division Monthly Report for _
January 1947, L. W. Nordheim, comp., MonP-250, Clinton Laboratories,
Feb. 19, 1947. Decl., March 23, 1956.
Gale Young, Outline of a Liquid Metal Pile, MonP-264, Clinton
Laboratories, March 6, 1947,
Richard Wolfgang, Fission Recoil Separation of Fission Products in
Power Reactor Design, Nucl. Sci. Eng. 1, No. 5, p. 383 Oct. 1956
C. Goodman, J. L. Greenstadt, R. M. Kiehn, A. Klein, M. M. Mills,
and N. Tralli, Nuclear Problems of Non- Aqueous Fluid-Fuel
Reactors, MIT-5000, MIT, Oct. 15, 1952. Decl., Feb. 28, 1957,
G. Scatchard, H. M. Clark, S. Golden, A. Boltax, and R. Schuhmann, Jr.,
Chemical Problems of Non—Aqueous Fluid- Fuel Reactors, MIT-5001,
MIT, Oct. 15, 1952. Decl., Oct. 7, 1959,
Power Plants with Thermal Reactors, MIT-5003 Del., MIT,
Sept. 15, 1953, p. 517. Decl. with del., March 5, 1957.
Liquid Metal Fuel Reactor. Technical Feasibility Report, BAW-2,,
Babcock & Wilcox Co., June 30, 1955, Decl., Feb. 15, 1960, pp. 25-27.
17
18
17.
18,
19.
20.
21,
Liquid Metal Fuel Reactor, Interim Feasibility Report, BW-AED-501,
p. 358, Babcock & Wilcox Co., March 31, 1955.
C. Williams and R. T. Schomer, Liquid Metal Fuel Reactor and
LMFRE-I, Proc. 2nd U.N. Int. Conf. on Peaceful Uses of Atomic
Energy 10, pp. 4872499, United Nations, N.. Y,, 1958.
Report of the Fluid Fuels Reactor Task Force to the Division of
Reactor Development, United States Atomic Energy Commaission,
TID-8507, USAEC, Feb. 1959.. . ..
Externally Cooled LMFR, A Reference Design for Low-Cost Power,
BAW-1147, Babcock & Wilcox Co., March 1960. |
|
- Major Activities in the Atomic Energy Programs, Jan-Dec 1959,
pp. 31-32, USAEC, Jan. 1960..
19
Chapter 2. Internally-cooled Reactors
In the reactors described in this chapter, the fuel remains stagnant
within the core except for circulation needed for changing and reprocess-
ing fuel. The circulating coolant flows around the fuel. Typically, the core
is a graphite or beryllium structure, with tubes for the fuel and passages
for coolant., IFast reactors, with no moderator, have also been designed.
Because the fuel does not circulate outside the core, internally-cooled re-
actors have.the advantages that a lower fuel inventory is needed and the
heat exchangers and other equipment outside the core are not contaminated
by radioactive coolant. Alsvu, the shielding problem is simpler. The devel-
opment of internally-cooled reactors has been contemporary with that of
externally-cooled reactors, and they have been compared at different times
for specific purposes. ‘ ‘ ’ ‘
One-fluid Reactors
In these reactors, if conversion or.breeding is desired, the fertile
material is incorporated into the fuel solution or slurry.
In 1946, Snyder suggested a fast breeder in .which the fuel and fertile
material is a slurry of uranium-235 and uranium-238 in molten metal;’
The fuel is contained in compartments to prevent gross physical changes
in the physical disposition of the active metal, with consequent changes in’
reactivity. The coolant, either an alloy of lead and bismuth or one of
sodium and potassium, flows around the compartments.
A 1947 concept was the Bismuth-cooled, Liquid-metal-fueled,
Thermal Pile.? .In this concept, alternative arrangements of the U?*? fuel,
beryllium moderator, and bismuth coolant are given: a vertical or hori-
zontal cylindrical or a spherical core; the beryllium as plates separating
fuel from the coolant or as tubes containing the coolant, with the fuel
outside. ' '
An unusual coolant, boiling rubidium, is a feature of a concept by
Grebe.? Uranium-235 in molten rubidium is the fuel. The rubidium boils;
the vapors rise to the top of the reactor, where they are condensed by
contact with cooling coils; and the liquid returnsr to the bottom of the
reactor. .. o
Two concepts for internally-cooled reactors fueled with liquid
metals were proposed in 1950 by staff members of the H. K. Ferguson Co.*
In both concepts, the coolant would bé a liquid that is lighter than, and
immiscible with, the liquid-metal fuel. A molten salt or another non-
metallic, immiscible liquid might be used as the coolant.
20
In the Bubbler-type reactor, the fuel (molte‘n uranium-bismuth or
uranium-aluminum) fills the vertical, cylindrical reactor. The lighter,
immiscible coolant is pumped to the bottom of the reactor, and bubbles of
it rise through the fuel to extract heat, which is exchanged to a secondary
coolant.
The reactor vessel in the Rotating-plate reactor, which is similar
to the Bubbler-type reactor, is a horizontal cylinder with a battery of ro-
tating metal discs. This reactor also closely resembles Grebe's Rotating-
ring concept of 1954. The immiscible coolant floats on the fuel, and heat
is transferred from fuel to coolant by the rotating metal discs. The fuel
(uranium-bismuth or uranium-aluminum) partially fills the cylinder.
An early theoretical approach was that of Neustadt,” who in 1951
made calculations to determine the effect of fuel lumping on the performance
of a reactor fueled with uranium-235 in bismuth and moderated with
beryllium. An unusual feature is the sharp difference between the tem-
perature of the molten fuel in molybdenum tubes (1947°C) and the beryllium
moderator (20°C). The two were to be separated by a gap filled with helium.
Use of the low moderator temperature and the high fuel temperature was
an attempt to partly compensate for the effect of lumping on critical mass,
Calculations showed that it would not do so.
A 1952 ORSORT term paper by Davis et _a_\.l.f’ described a concept
for a fast reactor fueled with a eutectic of iron and slightly enriched urani-
um. This sodium-cooled reactor was designed to produce 153 MW(t).
In a preliminary investigation of the thermal properties of a power
reactor, Old” proposed a fast reactor fueled with a eutectic of plutonium
and nickel. This reactor, cooled by either sodium or lead and with an out-
let temperature of 1000°F, would produce 500 MW(t).
Four designs for fast reactors were proposed in 1952 in a joint
study of reactors by the Dow Chemical Company and the Detroit-Edison
Company.®? Among them was an unusual fast reactor, the "Pineapple" re-
actor. In it, the core is a sphere of molten-metal fuel (plutonium-nickel
eutectic), at about 750°C, within a container. The metal circulates rapidly
to the container surface. Near this surface are many small recessed
cyclones, into which the fuel is inducted by jets of sodium, the coolant.
After they are mixed, the fuel and coolant are separated by centrifugal
force; the coolant goes to heat boiler tubes, and the fuel returns to the
core. With plutonium fuel, this reactor should have a specific power of
5000 kW/kg and a breeding gain of 0.8 to 1.0. A blanket of thorium or
depleted uranium was suggested for breeding. Adding appreciable amounts
of fertile material to the core would slow neutrons by inelastic collisions
and would require an increase in the critical mass.
21
The remaining three reactors are similar in structure to each other
but differ in the type of fuel, power, size, breeding gain, and other details,
In all, the core is a container of molten fuel cooled by sodium flowing in
tubes through it. The reactor is made up of sections in a radiator type of
arrangement. Individual sections might be filled outside the reactor and
inserted. The individual sections, "fuel elements," are very small--
0.1-inch diameter,.
This small size is necessary because the high heat release per unit
volume requires either such small sizes of fuel elements or large drops in
ternperature.> For breeding, a blanket of thorium or of natural or depleted
uranium would be used. The coolant temperature available for steam pro-
duction is 900°F for the first and third reactors, and 1020°F for the second.
In the first design, the fuel is a eutectic of plutonium and nickel.
It has a maximum heat output of 25 MW (t) and, at 30% efficiency, produces
7.5 MW(e). The breeding gain is 0.8.
The second design is for a reactor fueled with a slurry of uranium-
bismuth alloy in bismuth. Because of the fuel dilution, adding appreciable
amounts of uranium-238 to the core for internal breeding would be dif-
ficult. This reactor requires four times as much [issionable material
(200 kg) for criticality as does the first design, and this core volume
(200 liters) is 25 times that in the first. The reactor produces 460 MW(t)
and 138 MW (e) at 30% efficiency. The breeding gain is 0.4.
The third design includes a solution fuel (plutonium-nickel) with
solid fertile material (uranium). The critical mass and core volume are
of the same order of magnitude as those of the second design. The re-
actor produces 75 MW(t) and 22.5 MW(e), at 30% efficiency. The breeding
gain is 1.0. | :
In Grebe's Rotating-ring concept (1954),10 the moderator-coolant
is a solid, formed of a series of concentric graphite cylinders (rings)
rotating as a unit and moving through the reactor core. Thus it is similar
to the 1956 Rotating-plate Reactor of the H, K. Ferguson Co. Beryllium
or lithium-7 deuteride might be used for the rings. The molten uranium-
bismuth fuel is in annuli between the cylinders in the core, which is po-
sitioned eccentrically with respect to the axis of the rings but parallel to
it. As the rings move through the core region, they are heated. The
portions outside the core act as a heat exchanger, and boiler tubes are in
annuli in the outside area.
In a 1955 ORSORT termpaper by Burch et al.'’ is a brief descrip-
tion of a uranium-bismuth-fueled reactor cooled by both water and molten
sodium. In one part of the core, water is circulated at 1000 psi, it is
heated, and pressure is reduced to form steam. In the other, molten
22
sodium is circulated to give heat for superheating the steam formed by
the water. Breeding ratios calculated for cores of 5, 10, and 20 ft diam-
eter were too low for economic power, and the concentration of uranium
needed was above the solubility of uranium in bismauth.
One of the Babcock & Wilcox designs was for a single-fluid,
internally-cooled converter, with a graphite core, and with a slurry of
uranium and thorium as combined fuel and fertile material.'?!* Both the
fuel and molten-bismuth coolant are in passages within the graphite struc-
ture, with the coolant flowing past the fuel. The power is 825 MW (t).
A reactor with a graphite core drilled with vertical passages con-
taining fuel and horizontal passages for circulating helinm coolant was
proposed by Robba and staff members of the Raytheon Manufacturing
Cornpany.14 The fucl is highly enriched uranium in molten bismuth. The
helium leaves the core at 1300°F to produce steam at 850 psig and 900°F
in a steam generator., This reference design for a power station would
produce 16.5 MW(e). '
The first Los Alamos Molten Plutonium Reactor Experiment
(LAMPRE-I)}1¢ was a fast reactor with a molten eutectic of iron and
plutonium as fuel. The fuel is contained in tantalum capsules in a cylin-
drical core, with stainless-steel reflector pins in some of the capsule
locations and fuel in the others. The investigative program for this re-
actor included determining feasibility of separating fission gas from the
molten plutonium fuel; satisfactory fuel containment; and the suitability
of this type of reactor for power breeders. The reactor has been success-
fully operated.
An internally-cooled, one-fluid reactor for ship propulsion was
described by Byford in 1959.'7 The fuel, molten uranium-235 in bismuth,
. is contained in tubes in graphite sheaths, with provision for adding and
removing fuel., Molten bismuth flows up through coolant tubes, around
the fuel elements, and out to a heat exchanger cooled by molten salt. The
power, 33 MW(t), is considered suitable for the class of ships with about
25,000-ton dead weight, powered by a geared steam turbine of 12,000 shp.
Two one-fluid reactors have been proposed for rocket propulsion.
In the first concept, by McCarthy,18 molten uranium or plutonium is held
by centrifugal force against the walls of a rotating cylindrical rocket.
Hydrogen, which is the coolant (working fluid), is passed through small
holes into the rocket chamber, and it bubbles through the fuel. The maxi-
mum temperature is reached as the gas leaves the surface of the metal.
Possible difficulties with this concept include loss of fuel by formation of
volatile compounds with the gas or by being blown out of the chamber,
difficulties in pumping gas through the molten fuel, and the problem of
keeping the engine spinning. In the second concept, by Rom,'? which is
23
very similar to the first, molten uranium carbide (m.p. 4485°F) is the
fuel. Hydrogen passes through the walls of the rocket, which are porous
tungsten-184, and bubbles through the molten fuel and out of the nozzle,
The reactor would operate at below 6500°F and 1000 psia. (Tungsten melts
at 6120°F;) :
Two-fluid Reactors
¥
The need for more fcrtile material than could be included in a one-
fluid reactor has led to many concepts for breeder reactors, particularly
those from BNL and Lhe Babcock & Wilcox Company.
One of the earliest concepts was a two-fluid breeder, briefly de-
scribed by Young in 1946.°° A molten alloy of uranium-235 in bismuth is
contained within the walls of a beryllium moderator core, and bismuth
coolant flows around the fuel. A thorium blanket surrounds the core.
Spedding, in 1953, discussed the use of molten metals as fuels in
advanced concepts for both thermal and fast reactors.?!
In the thermal reactor, which could be a converter or breeder, the
fuel is enriched uranium in a eutectic with chromium, iron, nickel, manga-
nese, or other metals; uranium-235 would be used initially, and the
uranium-233 produced would be used later. The fuel is within tubes around
which the coolant flows, and the fertile material circulates through tubes
in the annulus at the periphery of the reactor vessel. In the other concept,
Spedding postulated that a fast reactor of the same design as for the thermal
reactor would be possible if more than 2 percent uranium could be dis-
solved in molten magnesium, ’
A design for a molten-fuel fast breeder reactor, also known as the
Power Breeder Reactor or the Fast Power Breeder Reac‘cor,?“z’?‘3 was
developed by Kelly, Robbins, Stichka, and other members of the staff of
California Research and Development Corporation. This 1953 concept in-
cludes a molten alloy of plutonium, uranium-238, and nickel as fuel, a
blanket of spheres of uranium-238 as fertile material, and control by
movement of plutonium silicide rods in the core and movement of the
fast reflector--a hollow nickel cylinder around the core. The reactor was
designed for a power of 180 MW(e).
A modification of'the Sodium Graphite Reactor to take advantage
of the properties of liquid metal fuels was. given in a preliminary design