ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR NUCLEAR POWER FOR TRANSPORTATION INITIAL PROGRAMS OF RESEARCH AND DEVELOPMENT FOR NUCLEAR POWER UNITS AND HIGH-TEMPERATURE MATERIALS CHRYSLER COR?.ORATFIN','PR0QJEQGT-, 2427 By: H. A. Ohlgren, University of Michigan D. H. Stewart, Chrysler Corporation M. E. Weech, University of Michigan October 3, 1955

ACKNOWLEDGEMENTS This report is prepared under the contract, Applications of Nuclear Energy to Transportation, between Chrysler Corporation and the University of Michigan. The work is administered by the Engineering Research Institute. This report is made possible through cooperative efforts of the technical groups of Chrysler Corporation and the faculty and staff of the University. The authors are grateful to the technical suggestions of Mr. George Huebner, Jr., Dr. Clayton Lewis, and Mr. Edward Mason. The staff and faculty who have contributed to various aspects of the report are Ralph Dennis, Kenneth Gordon, F. G. Hammitt, Raymond Knight, J. G. Lewis, Robert Mueller, Keshav Sanvordenker, Jerome Shapiro, and Doris Thompson. Organization, editing, and secretarial assistance has been given freely by Mrs. Joan Savage. ii

TABLE OF CONTwENTS Page 1. 0 ABSTRACT 1 2.0 POSSIBLE NUCLEAR POWER PROGRAMS IN WHICH CHRYSLER MAY HAVE INTEREST 3 3.0 RESEARCH AND DEVELOPMENT INVESTIGATIONS 7 4.0 DISCUSSION OF SPACE AND FACILITIES OF TEE UNIVERSITY OF MICHIGAN 24 5.0 PROBABLE EXPENDITURES 29 6.0 DISCUSSION OF NUCLEAR POWER SYSTEMS 32 7.0 HEAT ENGINE CYCLES 45 iii

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 1.0 ABSTRACT Joint efforts of technical staffs of Chrysler Corporation have conducted surveys of fields of nuclear energy in which Chrysler Corporation may desire to undertake. Tentative conclusions have suggested that results can be expected by combining engineering evaluations of the broad field of nuclear energy with specific initial research and development programs. Engineering investigation of nuclear power for transportation consists in re-application of data and information developed by others to propulsion. Reactor technology in this area considers: 1.1o Water cooled-steam generating reactors. 1.2 Heterogeneous, liquid metal cooled-steam generating reactors. 103 Heterogeneous gas cooled reactorso In addition to nuclear power programs, consideration should be given to energy utilization from large quantities of fission products. Long-range studies of fusion-fission types for energy generation is worthy of consideration, Specific research and development programs considered desirable cover the following: 1,4 High-temperature homogeneous reactors. 1.4.1 Bismuth-uranium fuel. 1.4.2 Metal-uranium molten salt fuel. 1.5 High-temperature particle reactors. 1.5.1 Fluidized bed reactor. 1.5.2 Gas-cooled heterogeneous reactor. 1.6 Fission to thermal energy studies. 1.6.1 Heat transfer. 1.6.2 Fluid mechanics. 1.6.3 Corrosion. 1.7 Closed cycle gas turbines. 1.7.1 Working fluids, correlation of nuclear and engineering data. 107.2 Turbine system analyses. 1.7.3 Components - turbines, compressors, heat exchangers... ~1

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 1.8 Investigation of high-temperature materials. Lo8.1 Carbon. 1.o82 Coatings. 1o8.3 Porous metalso Outlines of programs of research and development which can be initiated promptly are presented. In the event it is desired to utilize facilities at the University of -ichigan, a description of available space and estimates of added expenditures are discussed..._ _ _ _ _ _ __ 2, 2

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 20Q POSSIBLE NACLEAR POWER PROGRAMS IN WBICH CHRYSLER MAY HAVE INTEREST Through contract relations between the Chrysler Corporation and the University of Michigan, intensive investigations, analyses, and evaluations of nuclear power applications to transportation are in progress. These studies are being conducted to evaluate technical and economic applications of nuclear reactors for transportation purposes. The general range of these studies is to evaluate reactor systems which are in stages of operation, construction, engineering, research, and development, as well as conceptual design being originated at the University of Michigan for a range of horsepowers. These analyses have reached the point now where due consideration to programs of physical research and development paralleling engineering studies should be considered so that maximum progress in nuclear fields can be achieved. As a result of the studies which have been conducted to date, it has been possible to define certain initial programs for experimental investigations. In general, the nature of physical research includes certain basic investigations for one or more of the promising reactor types whose mass to power ratios might be reduced for utilization in transportation devices of several types. Heretofore, it has not been practicable to consider nuclear power reactors for propulsion units whose power requirements are less than 10,000 shaft horsepower. This has been due mainly to bulky equipment, heavy shields, and multiplicity of reactor controls. Joint investigations by the faculty and staff of the University and technical personnel of Chrysler Corporation have indicated that there are four reactor types which, through research and development, might have application to economical propulsion units whose shaft horsepower ranges are from 500 to 25,000. In order to achieve nuclear power systems of minimum mass to power ratios at maximum operating efficiency, it is suggested that physical research and development covering reactor studies, nuclear reactor loop investigations, turbo-machinery development, and high-temperature materials be investigated. This report discusses briefly those nuclear power systems which have been evaluated in detail, and effort has been made to delineate those specific types of reactors which through intensive research and development programs might find application to a multiple number of transportation devices. The areas of unknowns and limits of nuclear process variable are of great magnitude. It is believed, however, that by undertaking an aggressive program of physical research parallel with engineering studies much progress can be made. The engineering studies are intended to evaluate data and information being conducted at various locations throughout the world with constant reapplication of such data and information for specific transportation programso The coupling of such engineering efforts with specific problems of research investigations may provide the necessary insights to technical and economic feasibility of nuclear power for propulsion.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Utilization of nuclear power in fields of transportation can be considered from several viewpoints. In addition, it should be pointed out that certain types of power generation may not require the utilization of the fission or fusion process. Further possibilities exist in the utilization of radiochemicals of high specific activity when and if they become available. For the present writing, however, the programs are limited to nuclear reactors until such time as the work and effort by the coordinated staffs of Chrysler and the University can resolve those areas other than nuclear reactors in which Chrysler may have interest. American industry in conjunction with the United States Government are pursuing aggressively the use of nuclear power for electrical production and propulsion. A major emphasis in research, development, engineering, construction, and operation appears to favor water types of reactors. Further, this emphasis appears to lie in fields where reactor heat power requirements are in the range of 50 megawatts to 1000 megawatts of energy generated. Except for certain military propulsion devices and merchant ship application, a relatively minor effort is being undertaken for power production from nuclear reactors whose heat power output is less than 50 megawatts. In general, when considering the power requirements for transportation, a wide range is encountered. 2.1 Air-Borne Vehicles Air-borne vehicles are considered in categories which involve transportation of human cargo and devices of a pilotless nature. It can cover fields of aircraft, rockets, missiles, ram-jet devices, and others. Developmental activities by the military are sizeable in magnitude. It is suggested that Chrysler's efforts in the air-borne field of nuclear applications be limited presently to studies which will permit complete working knowledge in this area plus considerations for component and propulsion machine development. In the event certain reactor research and development programs contained herein meet with the general knowledge and promise, then consideration ofsuch reactor systems for air-borne applications may be worthy of consideration. 2.2 Marine propulsion Marine propulsion offers immediate opportunity for optimum use of nuclear power. In general, reactors of the water type, of the heterogeneous liquid metal cooled type, and of the homogeneous type have application to the range of specific classes used in marine propulsion. For vessels whose shaft horsepower requirements are in excess of 15,000 and where weight of generating and propulsion machinery are not critical factors, reactor power plants which have or are being demonstrated are technically feasible. Development work for reapplication might be limited to component testing. Competitive economics for nuclear power steam generation as compared to fossil fuel steam generation are contingent largely on demonstration, optimization of design to minimize capital outlay, and development

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN of cheap nuclear fuels. In the range from 15 to 25,000 horsepower, present considerations indicate reactors of the fissioning type are preferable. In marine applications where shaft horsepowers approach 150 to 250,000, consideration can be given to partially enriched convertor reactors as well as breeders. In general, it is felt that ChryslerTs research and development efforts might be best applied to those types of reactors and propulsion systems whose energy requirements and temperature needs are in excess of 10000F. This offers the opportunity for development of reactors of small size for maximum horsepower concurrent with the development of turbo-machinery employing new working fluid. 2.3 Land Vehicles When giving consideration to types of land vehicles in which nuclear propulsion has application, consideration must be given to minimizing mass horsepower ratios as well as careful attention to health and safety hazards which may be encountered. From a military viewpoint, there appears to be certain vehicles such as tanks and remote Arctic trains in which nuclear propulsion might be developed to sizes compatible with general requirements. In the fields of railroad transportation such as locomotives, considerable opportunity through properly organized research and development programs is in the horizon. In general, it is believed that the initial efforts should be directed toward land-type vehicles whose shaft horsepower requirements lie between 500 and 8,000. A small effort in giving consideration to very long-range concepts which might permit development of low mass to horsepower ratio nuclear propulsion machines for vehicles whose shaft horsepowers are under 500 might be undertaken. Chiefly, it is believed that the emphasis in research and development should be limited presently to the high-temperature materials investigation field. 2.4 Other Applications In giving consideration to new types of high energy reactors as well as accumulated quantities of gross fission products from spent fuels of nuclear reactors, due consideration should be given to their utilization in industries. As a case in point, the production of small packaged boilers in the range from 15 to 75 horsepower might consider employing gross fission products in solid or molten form as the heat source. Considerationmight be given to the employment of an aqueous homogeneous reactor of the fissioning type for heating large buildings as well as producing power requirements for lighting and electrical means. Constant attention should be given to the utilization of radioisotopes for chemistry, metallurgy, internal combustion engines, chemical reaction kinetics, and a wide range of other applications With this as a general introduction to possible fields of activity, it is urged that Chrysler Corporation give consideration to the institution of physical research and development programs covering the following areas. 5

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN In principle, the objective is to investigate the areas of unknowns and delineate engineering variables so that nuclear power for propulsion can be produced at maximum energy levels, at minimum mass to horsepower ratios, at low capital costs with operating costs competitive with fossil fuels. Realization of these objectives requires physical research in fields of reactors;' nuclear reactor loop studies involving heat transer, fluid flow, temperature profiles, etc; closed cycle gas turbine studies from the standpoint of materials, optimum working fluids, seals, and life tests; and a general program for developing a novel material for construction for reactors, heat transfer apparatus, and propulsion machinery. Consequently, the scope of experimental work lies in the following: 2.5 Reactor studies. 2.6 Reactor loop studies. 2.7 Closed cycle gas turbine investigations for high-temperature materials. __ _ _ _ _ _ _ _ _ _ __ _ _. _ _ _ _ _ _67_ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3.0 RESEARCH AND DEVELOPMENT INVESTIGATIONS 3.1 General Viewpoints and Philosophy An active program of research and development for nuclear power, conversion of fission energy to thermal energy, conversion of thermal energy to mechanical energy at high temperatures is considered desirable. Associated with such direct programs must be fundamental investigations of high-temperature materials. A calculated risk is encountered when research and development is "pin pointed" to specific reactor types and specific problems. Investigations into the wide field of reactor technology and associated turbo-machinery have resolved desirable areas of investigation. Such investigation might be undertaken aggressively now. Such areas in general cover high temperature reactors (8000C to 10000C), heat transfer studies and fluid studies for molten metals and metallic salts, and closed cycle gas turbine investigations. It is believed that initial research and development concentrated to these areas might be started at relatively modest research expenditures. It should be borne in mind that a complete program for research, development, engineering, construction, and operation of high-temperature reactors with attendant turbo-machinery equipment or heat engine devices will involve considerable expenditures and will of necessity be long range. The general steps for such a long-range program are suggested as follows: 3.1.1 Cold reactor studies, heat transfer and gas turbine closed cycle studies associated with high-temperature material investigations. 3.1.2 Nuclear studies involving basic nuclear data such as cross sections at high temperatures, criticality experiments, and fission at low power. 3.1.3 Prototype of a full power reactor with associated turbomachinery. 3.2 Requirements for Initial Nuclear Experimental Facilities Under the existing contract between Chrysler and the University, it is suggested that a portion of this effort be devoted to engineering of experimental facilities for nuclear power reactor studies by making cold equipment runs. The overall program may require many millions of dollars of expenditures, ahd practical objectives cannot be expected in a timetable much less than ten years. Since a certain program being conducted by governmental agencies lies in the high-temperature area, it can be expected that certain useful information and data will be developed in government national laboratories, as well as by AEC contractors, so that the expenditures for a single corporation may not be extravagant. 7 -- ---------— ~~

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Paralleling a specific program of research by Chrysler Corporation necessitates continuous liaison and access to information in these parallel fields being conducted by us. Such a parallel program will tend to minimize duplication of efforts and make maximum utilization into specific application of the data provided by others. Evaluations conducted by University and Chrysler staffs to date suggest that consideration be given by Chrysler Corporation to specific immediate investigations into the following areas: 3.2.1 Reactors 3.2.1.1 Bismuth-uranium homogeneous fissioning reactor. 3.2.1.2 Uranium-metal salt homogeneous fissioning reactor. 3.2.1.3 Highly enriched heterogeneous gas cooled reactor with ideal working fluid for closed cycle gas turbine. 3.2.1.4 Fluid bed reactor using enriched fuels of thermal and fast types. 3.2.1.5 Control and instrumentation. 3.2.2 Reactor Loop Studies 3.2-2.1 Heat transfer and temperature distribution. 3.2.2.2 Fluid mechanics of high-temperature solutions. 3.2.2.3 Thermal circulation. 3.2.2.4 Corrosion and materials stability. 3.2.3 Closed Cycle Gas Turbines 3.2.3.1 Working fluids. 3.2.3.2 Seals and closure. 3.2.3.3 Heat exchange. 3.2.3.4 Compression. 3.2-3.5 Expansion. 3.2.3.6 Control 3.2.4 High-Temperature Materials 3.2.4.1 Testing of known materials for reactor, heat exchange, and turbine and establishing maximum temperature limits. 8

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3.2.4.2 Coating of stocks for special carbons and graphite. 3.2.4.3 Special coatings such as zirconium carbide, hafnium carbide, tantalum carbide, the families of nitrides, etc. on special materials. 3.24.,h4 Porous structures with coolant passages for hightemperature impervious coating. It is believed that significant progress in each of these fields can be made. Careful evaluations of results as research programs unfold will permit the re-orientation of activities from time to time. 3.3 Specific Engineering Approaches to Research Problems Consideration should be given to initiation of simultaneous programs of investigation of reactor parameters, loop and circulation studies, closed cycle gas turbine investigations, and high-temperature materials. Insofar as time has permitted, the engineering approach to such investigations reach the descriptions of the physical facilities and the types and natures of problems which can be investi — gated are presented. As studies are continued, definition of unknowns and delineation of variables will permit further definitions of problems requiring resolutions. 3.3-1 Reactor No. 1 - Operated as a "Cold" Reactor It is believed possible to design one experimental apparatus which will permit the study of a molten metal bismuth-uranium homogeneous solution and a reactor concept involving molten uranium and metallic salt as a homogeneous solution in a single experimental device. The ability to achieve such a single experimental installation for multiple reactor studies is contingent mainly upon the proper materials of construction which can withstand corrosion attacks at high temperatures. Figure 1 represents a basic idea of a reactor core into which is designed maximum heat transfer surface for removal of fission heat. It is proposed to design and construct and operate an experimental reactor which has general dimensions of 1I ID x 2' straight shell. This reactor would have dished heads. Into the internals of the geometry of the reactor would be designed heat transfer tubes in such a manner to obtain a maximum surface within the active core. Preliminary calculations and layouts indicate that from 15 to 20 square feet of heat transfer surface might be built into such an experimental reactor unit. The necessary connections for vacuum, pressurizing, filling, and draining would be required. It is proposed to construct the reactor shell from a new Croloy type of alloy manufactured by Babcock and Wilcox. It is proposed to construct the heat transfer surface from 1/2" tubes utilizing special bending devices. Such tubes would be fabricated from type 310 stainless steel, metallized on the outside surface with pure 9

^ I' - o"i GAS i OUT 1/2" VACUUM CONN. l'WJJ Sk1/2" PRESSURIZER CONN. ~4 //~~ God~11 I/2" FILL CONN. CARBON ELECTRODES 0 0 0C TEMPERATURE WELLS 5/8" WALL SUPPORT' LUGS 1/2" DRAIN CONN. GAS IN (THROUGH TUBES) FIG. I EXPERI MENTAL REACTOR FOR HOMOGENEOUS LIQUID METAL AND FUSED SALT REACTOR STUDIES 10

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN iron chrome. The heat transfer tubes would be swedged into a bundle. The tubes would extend through a suitable nozzle top and bottom of the experimental reactor. Tube sheets would be formed by heliarc welding of the spaces between tubes to a flanged cover. By machining the flanged cover and the welding, it would be possible to obtain a gas-type connection. Heating for the reactor shell would be provided by carbon electrodes inserted into the molten metal. It is believed that these carbon electrodes associated with a bismuth-uranium solution and/or a uranium tetrachloride metallic salt solution would provide adequate energy input. We will investigate those necessary problems presently visualized. A working fluid such as nitrogen, helium, C02, argon, etc. can be pathed over a range of temperatures and mass flows through the tube side of the heat transfer and measurements of the heat transfer effectiveness over a variation of temperatures, pressures, and fluid flows can be made. Investigating the necessary areas of unknowns for a bismuth-uranium reactor, there would be required about 1000 pounds of bismuth and about 10 pounds of natural or depleted uranium. Early requisitions for these types of materials would be required to facilitate and expedite a research program. Projecting the utilization of a liquid bismuth-uranium reactor to a power plant is shown by the schematic flowsheet in Figures 2 and 3. When considering uranium salts with metallic salts as reactor fuels, the projected flowsheet is shown in Figure 4. This would permit investigating the following physical and chemical data: 3.3-1.1 Solubility data of uranium in bismuth at high temperatures, including precipitate formation as a function of temperature change. 3.3.1.2 Viscosity data at high temperature. 3.3-1.3 Thermal conductivity data. 3.3.1.4 Electrical conductivity. 3.3.1.5 Expansion coefficient as a function of temperature. 3.3.1.6 Chemical stability. 3.3.1.7 Wetting experiments. 3.3.1.8 Solution stability at high temperature. 3.3.1.9 Specific heat data. 33.31.10 Influence of trace elemnents. 11

,cLC. INTERNAL GRAPHITE MODERATOR AND REFLECTOR FIG.2 LIQUID METAL HOMOGENEOUS REACTOR URANIUM - BISMUTH LIQUID METAL FUEL (LESS THAN 2000 SHP)

5~~~~~~~ &osAJ. FIG. 3 01~~~~~~00 ~~~~~~60 ft ~~~~~~~(RATR HA 00 SP G~~I p5'j;'Ple OG Oft~~~~~~~~~~~~~~~~~~~~~~~~~~L ~~~n~~~V IIU* e"~~~~~~~~~~~~~~ *a s" e\C'~~~~~~~~F G LIQUID METAL HOMOGENE,~~~~~~~~~oe URANIUM -BISMUTH LIQUID N~~~~~~~~~~~~~~~(~~:Fe s~~~~~~~~~~~~~~~~~~(RAE HN20

J-J REACTOR FUEL IS SALT EUTECTIC AS HOMOGENEOUS SOLUTION OF UF4 IN LITHIUM FLUORIDE SALT MAX. TEMP SET BY URANIUM CONCENTRATION IN LITHIUM SALT. FIG. 4 LIQUID SALT EUTECTIC FISSIONING REACTOR (APPROX. SIZE - 1000 SHP PER REACTOR CORE)

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN Other physical and chemical data can be investigated as engineering proceeds simultaneously to assure the fundamental data permit optimum design. 3.3.1.11 Engineering Parameters 3.3.1.11.1 Heat transfer and film coefficient data. 3.3.1.11.2 Local turbulances and fluid flow studies. 3.3.1.11.3 Gas flow and gas film coefficient. 3.3-.111.4 Overall heat transfer. 3.3.1.11.5 Instrumentation and control. 3.3.1.11 6 Shell and tube expansion studies. 3.3-1.11.7 Agitation. 3.3.1.11.8 Fouling characteristics. 3.3.1.11.9 Degassing. 3.3.1.11.10 Gas absorption and adsorption. 3.3.1.11.11 Precipitation and criticality control. 3.3.1.11.12 Temperature distribution. 3.3.1.12 Materials Engineering 3.3.1.12.1 Corrosion. 3.3.1.12.2 Pitting. 3.3.1.12.3 Creep. 3.3.1.12.4 Thermal shock cycling. 3.3.1.12.5 Diffusion into materials. 3.3.1.12.6 Mass transfer. 3.3.1.12.7 Passivated film techniques, utilizing additives such as zirconium, magnesium, aluminum, etc. 3.3.2 Reactor No. 2 - Operated as a "Cold'Reactor This reactor will be designed to conduct experimental work for a fluidized bed type of reactor and heterogeneous cooled reactor. Heterogeneous gas cooled reactors are discussed in 15

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN general in section 6.0. Since sizeable efforts in research, development, engineering, and operation are being undertaken. by AEC programs, decisions for research programs for this reactor should be delayed until complete evaluations for applicability are made. Allowances in design of experimental reactor no. 2 should be made to accommodate such research if deemed advisable. The physical concept which has been developed for this experimental program consists in a design of a 2' diameter x 3' straight shell, water cooled wall type of reactor, provided with particle separation devices at the top, gas distribution plates at the bottom, and a closed loop for circulating a fluidizing media complete with fans, compressors, and controls. The concept of the experimental reactor is given in Figure 5. Into the reactor geometry within the shell there will be constructed a maximum amount of heat transfer surface fabricated from stainless steel tubes so that when the uranium oxide powder or add mixtures of uranium oxide and carbon powders are heated to a maximum temperature, radiation heat transferred to gas fluids flowing through the insides of the tubes can be made. When studying a fluidized bed, it is proposed to obtain several grades of uranium oxide whose particle size ranges are from 60 mesh to -325 mesh. This powder will be introduced into the experimental reactor. A gas such as nitrogen or argon will be used to fluidize the powder in the reactor shell, and various parameters will be investigated. For such studies, it would be necessary to obtain between 1000 and 1500 pounds of uranium oxide and an equal amount of carbon powder. Also, to complete the experimental work, it would be necessary to obtain carbon rods 1" in diameter with minimum length of 4'. Projecting the utilization of a heterogeneous gas cooled reactor to a power plant system is illustrated by the flowsheet in Figure 6. In the event the basic parameter and fundamental data for a fluidized bed reactor indicate feasibility for a power plant, a projected flowsheet schematic of such a plant is illustrated in Figure 7. The areas and problems which can be investigated in this experimental setup are as follows: 3.3.2.1 Physical and Chemical Data 3.3.2.1.1 Thermal conductivity versus temperature. 3.3.2.1.2 Viscosity gases. 3.3.2.1.3 Chemical and physical properties of 1U02 impregnated into carbons. 16

2'-0" FLUIDIZING GAS OUT -1/2" BACK WASH CONN. JACKET COOLANT OUT WORKING, l II L _ _ PARTICLE SEPARATOR FLUID' OUT I - ICOOULING JACKET HEAT TRANSFER SURFACE 5/8'" WALL TEMPERATURE WELLS HEATING ELEMENTS JACKET COOLANT IN ||'_________2__ iWORKING FLUID IN DISTRIBUTOR PLATE I.V2" PRESSURE TAP FLUIDIZING GAS FIG. 5 IN EXPERIMENTAL REACTOR FOR FLUIDIZED BED AND GAS COOLED REACTOR STUDIES 17

Of~ jeo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.o S 00H 1 HETEROGENEOUSHTERGENOUSGAECOLEDREATO (TO 25,000 SHP)

Rs g es~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~e clop~~~~~~~~~~~~ SO2 CARBON AS RODS ARE USED FOR MODERATION IF REQUIRED. FIG. 7 FLUIDIZED BED ECO (LIMITED TO 8000 SHP PRRATRCR

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3.3.2.1.4 Basic structures of special carbons. 3.3.2.1.5 Thermodynamic correlation for gas fluid - solid mixtures at high temperatures. 3.-32.2 Engineering Parameters 33.3.2.21 Radiant and convection transfer. 3.3.2.2.2 Particle size distribution. 3.3.2.2.3 Particle movement. 3.3.2.2.4 Ratio of UO2 to carbon, 3.3.2.2.5 Fluid flow studies through beds and through tubes. 33.20.2.6 Attrition of particles. 3,3.2,2.7 Particle separation from gas streams. 3.3.2.2.8 Gas circulation problems and fluid characteristics of powders. 3.3.2.2.9 Backwash technique for de-entrainment. 3,3e2.2.10 Gas fluid -heads with respect to bed depth. 3.3.2.2.11 Bed density changes. 3.3,2.2.12 Localized bubbling as a function of fluid flow. 3.3.2.2.13 Powder addition and powder removal. 3.3.2.2.14 Fluidization around tube and carbon rod inserts. 3.3.2.3 Materials Engineering 3.3.2.3.1 Properties of powders. 3.3.2.3.2 Properties of graphite moderators. 3.3.2.3.3 Materials of construction for shell and tubes. 3.3.2.3.4 Corrosion and pitting. 3.3.2.3.5 Erosion. 3.3.2.3.6 Powder stability. 20

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3 3. 2.37 Tube stresses. 3.3.2.3.8 Thermal shock. 3.3.2.3.9 Creep. 33.02.3,10 Sintered filters, high temperature. 3.3.2.3.11 Agglomeration. 3.3.2.3.12 Chemical reactivity of UJ2 and carbon with carbide oxide transition stages and phase diagram. By the conduction of the experimental work for the reactors mentioned above, it is believed that significant progress can be achieved in evaluating engineering parameters for nuclear engineering of four different types of reactors. 3.4 Investigations of High-Temperature Materials As an initial effort for investigation of high-temperature materials, it is proposed to install facilities for coking of special hydrocarbons to amorphous and graphitic type of coke. The installation of a high-temperature resistant furnace with carbon arc techniques so that materials can be prepared at temperatures approaching 55000F and of vacuum equipment so that samples can be prepared and evaluated after they are prepared. Design studies are underway now for the experimental equipment in which such high-temperature material studies can be made.- This installation will permit investigation of the following: 3.4.1 Special carbons and graphites. 3.4.2 Investigation of tantalum, hafnium, aluminum, titanium and other carbides and nitrides. 3.4.3 Vapor phase deposition of coating on various structural materials. 3.4.4 Studies of porous structures with impervious films so that the cooling of structural materials can be accommodated to minimize temperature differences and shocks. 3.4.5 High-temperature reactions for deposition and diffusion through materials. It should be noted that the initial efforts will not provide facilities for the testing of materials "per se." It is expected that such testing will be instituted after preliminary programs and new materials are produced. 3.5 Heat Engine Studies In giving consideration to the conversion of thermal energy to 21

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN mechanical energy at high temperatures and pressures, it is believed that research and development programs for investigating closed-cycle gas turbines in conjunction with nuclear reactors is one of the more important phases of achieving a minimum mass-to-horsepower ratio. A problem of heat engine research and development is basically one of long-range and must be continuously evaluated step wise as data and information unfold. Throughout the world considerable effort and expenditures have been spent on a development program. In these initial efforts of closed ycle gas turbine studies, it is suggested herein that consideration be given to investigations of working fluids whose nuclear and thermodynamic properties are suitable to nuclear propulsion. These investigations involve considering working fluids such as air, nitrogen, carbon dioxide, argon, helium, hydrogen, anhydrous hydrofluoric acid. The present engineering studies have indicated that temperatures approaching 1500OF for a working fluid at pressure ranges from 100 to 1000 pounds should be achieved in order to develop a closed cycle gas turbine in conjunction with a heat power nuclear reactor at optimum conditions. The research investigations contained herein are limited presently to the investigation of the basic and fundamental high temperature properties of working fluid. Reviews of the literature have indicated that little or no data at this range of temperatures and pressures are known. Thus, fundamental investigations as follows appear desirable as an initial effort. 3.5.1 Viscosity data. 3.5.2 Specific heat data. 3.5.3 Entropy data. 3.5.4 Enthalpy data. 3.5-5 Thermal conductivity. 3.5.6 Gas diffusion into high-temperature materials. 3.5.7 Seal studies. 3.5.8 Gas purification. 3.35.9 Heat transfer coefficients. 3.5.10 Solubilities and additives. 3.5.11 Expansion characteristics. 3.5.12 Compressibilities. 3.5.13 Radiation effects and stabilities of di-atomic gases. 22

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN In the event it becomes apparent that data and information and hightemperatures and pressures for various working fluids look promising, it is believed desirable to give consideration to the engineering design of a closed cycle gas turbine installation which has maximum flexibility for the greatest number of working fluids with the minimum changes in turbines, compressors, and heat transfer equipment. Through effective programs of fundamental research coupled with evaluations of data, it is believed possible in a reasonable period of time to consider the construction and installation of a closed cycle gas turbine whose general size permits extrapolation over a wide range of shaft, horsepower from the data produced. 23

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 4..O IDISCUSSION OF SPACE AND FACILITIES OF THE UNIVERSITY OF NMICIEGAN If Chrysler Corporation decides to initiate physical research and development activities in accordance with the program suggested in this report, a possibility exists that the sponsored research contract existent between the Chrysler Corporation and the University of Michigan migeht be extended to cover such areas of investigation. Under such conditions the faculty, staff, and students at the University can serve initially as the nucleus of a nuclear research and development group for Chrysler Corporation. To conduct the research programs covered in this report by an extension of contract, allocations of space and facilities for various functions are requisite. Certain suggestions are offered as possibilities and will require further investigation on the part of the University prior to authorization. The following discusses various categories of nuclear activities involved in the present and proposed work. 4.1 Space for Nuclear Engineering Work For the continuation of studies, evaluations, and analyses of fields and activities in the nuclear energy programs in which Chrysler might have interest as well as the requisite engineering work to achieve physical research and development and evaluation of resultant data, these various phases of work are being conducted in the Cooley Building of the North Campus. Added space is needed. Consideration is being given by the University, the Phoenix Project, and the Engineering Research Institute to possible utilization of space located on the third floor of the Phoenix Building. This space requires completion of lighting, partitions, flooring, etc. at relatively modest expenditures to adapt its use for engineering desig activities. Another possible alternate is being investigated for additional space. This alternate consists in leasing office space in the vicinity of Ann Arbor which might be adapted to use for engineering work, drafting, etc. 4.2 Space for Research and Development Two buildings located at the Willow Run Research Center area of the University of Michigan are possible locations for installation of physical and experimental facilities. One of the buildings contains space for office personnel and files. The second building has possibilities for installation of research equipment and associated facilities. These buildings are shown in perspective in Figure 8. 4.2.1 Office Building This building is of temporary construction consisting of a one story building covered with gray asphalt siding (mock concrete block). The total floor space is approximately 1130 square feet. This area has been partitioned into eight offices with a central reception area. The building is wired for 110 volt lighting source. It is supplied with drinking water and

DESCRIPTION OF FACILITLES BUILDING * 3 BDILDING #8 TYPE ONE STORY OFFICE BLDG. TWO STORY RESEARCH BLOG. SIZE 90' x 25' 104'x 38' CONST. TEMPORARY CONCRETE BLOCK a STEEL FRAME AREA 1130 SOQ.FT. 2000 SO. FT. MECH. EUIP NONE ONE TON TRAVELLING CRANE GENL FAC. WATER WATER SEWAGE SEWAGE 1ISv POWER I ISv POWER 220v'- 3 60 C, IOOKVA AIR LINES FUEL PIPE LINES?lko"~. oal, FIG. 8 ENGINEERING RESEARCH FACILITIES WILLOW RUN i'7' 0 as tf;S W0 ok jety"'''~ —---

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN sanitary sewage. The building is heated by forced air. All outside walls are insulated. I believe that this building will be adequate for housing personnel concerned with the operating of research and development functions. One of the offices has applicability to storage of classified material. Another office is adequate for the installation of several drafting tables in which design studies and modification to physical research facilities can be achieved. This office building layout is shown in Figure 9. 4.2.2 Research and Development Building Across the street from the office building is building no. 8. This building is a two-story concrete block building with steel frame. The total floor space available is about 2000 square feet. The main area has dimensions of 66' x 36' wide x 16-1/2' ceiling height. A one-ton travelling crane over this entire area is available. The height from the floor to the boom of the crane is 14'. The building is provided with 110 volt single phase power and 220 volt three-phase 60 current. Approximately 100 KVA of electrical power is available. Adjacent to the building are propane underground gas storage tanks which can provide necessary gas for experimental heating. Surrounding the building are piping headers for air, water, gas with various outlets at points around the building. Adjacent to the main area, there is a 24' x 36' x 10' high area which might be suitable for a maintenance area or a control area. The building has a small second floor at the North end of the building with a general space of about 12' x 36'. This area could be used as a storage room. The proposed experimental building is heated by forced air. In general, the building appears to be adequate for establishing experiments which must be run essentially by remote methods as well as having suitable free area to contain the initial program for research and development outlined in this report. This building layout is shown in Figure 10. In general, these buildings are located in an area of the Campus which can be isolated from the standpoint of its work. In the event the reactor studies might approach stages where criticality experiments as well as reactor low power experiments are conducted, it can be readily expanded for this type of function. Furthermore, it offers possibilities of installation of high sources of radiation in which a number of metallurgical process as well as radiation damage studies might be instituted at a later date. These buildings should be regarded as temporary facilities which will permit the initiation of research and development programs promptly and can be used possibly for such periods of time until permanent buildings for these types of research activity can be achieved. It is possible that arrangements might be made with the officials of the University to have this type of building space made available for a period of about three years. 26

~- N REST HEATING ROOM SECURITY OFFICE OFFICE OFFICE SCI I oa LTR 1 OFFICE OFFICE R 1 DRAFTING c IROOM RECETION LLILSJ.2.B1 I I I FLOOR PLAN FIG. 9 PROPOSED RESEARCH OFFICE BLDG. WILLOW RUN AIRPORT ENGR. RES. INST UNIV. OF MICHIGAN SCALE: 1/16',' 9 -15 55

* — N UTILITIES TO PROPANE TANKS AREA RESTROOM 011 0(~~__, BL)DG. HEATER BOIL ER CRANE ROOM 0 ow c HIGH BAY FU) c:: BLDG. HEAT ER -C~~~ Io" ~104' 0 FLOOR PLAN LEDGEND: FIG. 10 WATER PROPOSED o STEAM 0~~ PROPSTE~~ANEM~ ~PHYSICAL RESEARCH BLDG. PROP* ~~~~~AIRNE WILLOW RUN AIRPORT O V~~~~~~ACUUMIR~~ ~ENGR. RES. INST!- VACUUM o 115 AC UNIV. OF MICHIGAN SCALE: 1/S16" I' 9-15-55

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 5.0 PROBABLE EXPENDITURES Efforts have been made to predict ranges of expenditures which might be needed to begin programs for: 5.1 Installation of experimental equipment and facilities in available space and buildings. 5.2 Operating budgets. Assuming the fact that initial programs of research might be conducted for Chrysler by the staff, faculty, and students of the University of Michigan in buildings located at Willow Run, the following estimates have been made. These funds are above the present contract budget. TABLE I Summary of Physical Equipment* Experimental Nuclear Reactor #1 $ 39,925 Experimental Nuclear Reactor #2 51,120 High-temperature Equipment 24,900 Gas Fluid Studies 43,600 $159, 545 * Assumed that analytical facilities of the University's Department of Chemistry and Department of Chemical and Metallurgical Engineering can be used for the range of work. TABLE 2 Physical Equipment for Experimental Reactor #1 Vessels $10,350 Mechanical Equipment 3,525 Instruments 7,200* Piping 4,950* Structures 2,100* Electrical 11,800*O $39,925 *~ These are allocated costs. 29

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE 3 Physical Equipment for Experimental Reactor #2 Vessels $14, 320 Mechanical Equipment 6,400 Instruments 8,600 Piping 7,900 Structures 2,100 Electrical 11,800 $51,120 TABLE 4 Physical Equipment for High-Temperature Equipment Cooking Unit $ 3,600 Resistance Furnace 6,800 Vacuum Furnace 4,900 Structures 1,800 Piping 2,400 Electrical 5,oo00 $24, 900 TABLE 5 Physical Equipment for Gas Fluid Studies Experimental Apparatus $12,300 Mechanical Equipment 8,600 Instruments 6,600 Piping 5,100 Structures 4,200 Electrical 6,800 ~~~~30 ~~$43,600 30

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE 6 Operating Budget - Basis First Year Payroll $ 87,500 Analytical 25,000 Materials and Supplies 47,900* Office and Other 8,500* Travel 6,300 Reproduction and Reports 4,900goo $180,100 * Assumed that depleted uranium and UO2 can be obtained at no cost. Does not provide for recruitment, moving and travel, or for Chrysler personnel. 31

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 6.0 DISCUSSION OF NUCLEAR POWER SYSTEMS Consideration has been givern to a number of nuclear reactors which are in various stages of operation, engineering, and development in installations throughout the country for application to propulsion systems. This section of the report deals with a brief summary of the various possible nuclear reactors which are considered technically feasible for propulsion purposes as well as possessing potentials for economic applications in specific instances. 6.1 Pressurized Water Nuclear Power Reactor with Heat Exchanger The submarine thermal reactor, STR, is of this type. Pressurized water reactor systems employ heterogeneous fuel elements operating in the thermal range of neutron energy. Such reactors may be highly enriched with uranium-235, uranium-233, or plutonium-239 or they may be partially enriched with thorium-233 or uranium-238 with uranium-235. If natural uranium were used as a fuel in this type of a reactor, it would be necessary to employ heavy water rather than light water as a moderator. In the event of partial enrichment, such reactors would produce given amounts of uranium-233 or plutonium, depending upon the nature of fuels used. The reactor fuel is composed of solid fuel elements. For highly enriched reactors, it is necessary to design the fuels for specific power. Thus, it becomes necessary to design fuel elements for heat transfer surfaces of the extended type. Fuel elements of the plate type are common for highly enriched reactors. Plates are of the sandwich type. The meat of the sandwich is the active fuel, either pure or diluted with inert material. The bread or cladding is a metal such as zirconium or stainless steel. Figure 11 indicates the basic components of a closed loop circulating water heterogeneous reactor. Water at high pressures, 2000 psig, and at temperatures approaching saturation is circulated by means of a pump through a high-pressure vessel in which the reactor fuel is located. The fission energy is removed by the circulating water. The circulating water flows through a heat exchanger which serves as a steam generator. The feed water is transferred to the heat exchanger and steam is vaporized. Steam conditions may approach 6000 psig saturated steam, which can be used to operate a steam cycle turbine. dontrol of this type of reactor is sustained by positioning control rods through the pressure vessel. Such control rods absorb neutrons. In giving consideration to this type of a reactor for propulsion purposes, it appears that such a reactor can be applied without undertaking major programs of reactor research and development. On the mobile power viewpoint, this type of reactor has application mainly in the marine field such as submarines, naval craft such as aircraft carriers, merchant ships such as tankers, cargo passenger ships, and cargo ships. Economic studies indicate that such a reactor can obtain a competitive position only through an active program of building construction and operation. When using this type of reactor on shipboard as an example and assuming that structural shielding is needed, the minimum mass of the reactor system including heat exchangers within a shield 32

- ON 6AiAd CONTROL RODS HEATI I HE oil CORE DRUM P. ~ ~~1 j I2 RE ACTOR FEED WATER I FEED WATER IN P Pi I~~~~~~~~~~ i PI TAP TA PI~,I ":, A ~'.' j [ -.- i [i PUMP PUMP /L/_ ~ db ~4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHIELD I -' ~'' r~~ ~ ~~~~~~~~~~~~~~~~~~~~~.4. ~.rA ~ ~. - 0, P~~~~~~~~~~~~~~~~~~~~~~~~ 4"* d ~ ~~~~~~ ~~~' "'' ~C ~"'c FIG. II PRESSURIZED WATER REACTOR (POWER LEVEL I00 MEGAWATTS)

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN is about 1,000 tons. Thus, it does not appear practicable to consider this reactor for purposes under 15,000 shaft horsepower. From the viewpoint of economics, it appears that major reductions in capital costs for shipboard installation as well as major strides in reduction of fuel element costs must be achieved. At the present writing, the cost of this type of a reactor ranges from three to ten times more than the cost of ordinary steam generating equipment using fuel oil. From an operating cost viewpoint, the controlling costs appear to be costs of nuclear fuel elements. Such costs presently for plutoniumuranium are about ten times the cost of fossil fuels. It is believed that through an active program of development, the cost of nuclear fuel elements can be made competitive to the costs of fossil fuels. Employing partial enrichment types of reactors for shipboard construction in which the metallurgy of fuel elements will permit significant burnups of plutonium formed offer some attractive opportunities for reductions in operating costs. 6.2 Boiling Water Reactor A modification of the circulating water type of heterogeneous reactor is the flashing or boiling water type. This type is illustrated in Figure 12. Recent developments have overcome some of the problems and resolved certain unknowns. In this type of reactor, fuels may be used at high enrichments of uranium-235, plutonium-239, or uranium233. Also, they may be partially enriched or natural uranium types of reactors. In the latter case, it would be necessary to employ heavy water and exchange such heavy water with a light water loop. For application of this type of reactor to packaged power for mobile purposes, high enrichment appears to be more attractive. Where plutonium production is of value or where plutonium burnup can be utilized in fuel elements, partial enrichment also deserves consideration. Again, it appears that this type of reactor may have application to propulsion devices when shaft horsepower requirements are greater than 15,000. Certain possibilities for development of extremely highpressure systems permit favorable and efficient steam cycles might offer opportunities. As an example, if this were a supercritical water reactor, it could produce steam above the critical pressure of 3,200 pounds. It is possible to achieve a relatively efficient thermydynamic cycle. From a cost viewpoint, it appears that such a reactor necessitates a relatively high mass at low horsepower ranges. Capital cost requirements can be expected to be much higher than employing conventional steam generating equipment. From an operating cost viewpoint, the cost of fuel elements again appears to be controlling. Through properly instituted development programs, it would be possible to effect major reductions in fuel costs. 6.3 Aqueous HomogeneouReactor The Oak Ridge National Laboratory has pursued intensively a program for aqueous homogeneous reactors. In a homogeneous reactor, the fuel 34

CONTROL RODS SHIELD BOUNDRY BUS BARS S TEAM DRUM!l.L 1-~~~~ Ii v11 COREE lI apt C~~~TUR IE GENE ATO L,~, REACTOR | DRIPS TO CONDENSER ~~~~~~~~TAI I jLED I~~F I WTE EoAE SHIELD RQUSIEL FIG. 12 SCHEMATIC OF BOILING |WATER REACTOR

ENGINEERING RESEARCH INSTITUTE - UNIVERSITY OF MICHIGAN uranium or thorium is dissolved in an acid solution of water forming a salt uranyl sulfate. This solution is transferred to a critical geometry in which fission takes place. From the reactor, the solution flows to a heat exchanger where the heat is transferred to a second loop generating steam. Thus, non-radioactive steam is generated. It is possible to think-of a homogeneous reactor which directly boils water from the reactor. Such water boiled from the reactor would contain fission products, necessitating the shielding of turbomachinery. The aqueous homogeneous reactor has attractive possibilities for small, compact packaged power units as well as for convertor reactors for production of plutonium and uranium-233. In considering a homogeneous fissioning type of a reactor, this reactor offers greater promise in reduction of size since the critical geometry is about equivalent to the heterogeneous geometry of a fuel element assembly. It is believed possible through an engineering approach to reduce the overall mass of a fissioning, aqueous, homogeneous reactor including heat exchange equipment to something less than 500 tons. Thus, it would appear practicable to utilize an aqueous homogeneous reactor for propulsion purposes whose shaft horsepower requirements are in excess of 10,000. This type of reactor necessitates employing a steam cycle for its turbine machinery. At the present writing, it is limited to the generation of saturated steam at relatively low pressures and corresponding saturation temperatures. A typical homogeneous reactor system is indicated in Figure 13. 6.4 Liquid Metal Heterogeneous Reactor A heterogeneous liquid metal reactor is comparable to the pressurized circulating water reactor with the exception that liquid metal such as sodium has been substituted for water to permit operation at higher temperatures and at lower pressures. Liquid metal reactors of the highly enriched type employing heterogeneous fuel cores have application to propulsion and packaged power generation. Reactors employing partial enrichment or of the core-blanket type can be used for convertor reactors or for fast breeder types of reactors. The general principle for heterogeneous molten metal reactors is given in Figure 14. Liquid metal which may be a sodium, sodiumpotassium, sodium-lithium, or possibly molten salts of certain metals is circulated through a reactor vessel containing a critical core of a heterogeneous fuel assemblage. The circulating molten metal removes the fission heat and circulates through a steam generating heat exchanger or through a secondary liquid metal loop which in turn passes through a heat exchanger. A heterogeneous liquid metal reactor of the fissioning type operates in the intermediate range of neutron energies. Under such conditions it is possible to use fuel elements fabricated from stainless steel and uranium oxide employing reflectors of beryllium with sodium as a coolant. Under such conditions, it is possible to operate at temperature levels at low pressures in the primary loop. For applications to propulsion systems, somewhat higher thermal efficiencies might be realized. 36

BUS BARS SHCIRLDING STEAM DRUM L-~~~~~~~~~~~P TURBO GENERA'O HEAT HOMOGENEOUS EXCHAYCONDENSER REACTOR HEjTE FEED WATER RUN PUMP ccOD~VE CIRCULATING PUMP FIG. 1 3 SCHEM AT IC OF AQUEOUS HOMOGENEOUS REAC CTO R SYSTEM

CONTROL RODS BUS BARS SHIELD TURBO-GENERATOR l I I X LIQUID METAL SATURATED STEAM CONDENSER O M T M AP I C TO MSYSTEM FIG. 14| |ECOOLED REACTOR

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN In giving considerations to the economics of employing heterogeneous liquid metal reactors, heavy shielding is required for relatively massive equipment. It can be expected that the capital requirements for an installation would be considerably higher with present technology than installing the comparable conventional steam generation system. Analysis of operating costs indicates that the major operating costs lie in fuel elements.,Until such time as technology has advanced to permit the simple design of extended heat transfer surfaces containing highly enriched uranium as fuel, it does not appear likely that such a unit can compete economically. In giving consideration to the total mass of reactor plus auxiliary power generating equipment and if structural shielding is employed, the total weight required for this type of reactor approaches about 1,000 tons. Thus, a liquid metal heterogeneous reactor might have use in propulsion devices whose shaft horsepower requirements are in excess of 10,000. 6.5 Organic Liquid Moderated and Cooled ReactQr System Another possible reactor system would be to employ radiation resistant organic materials such as terphenyl for coolants and moderators in a pressurized reactor system employing heterogeneous fuel element assemblies. This type of reactor is subject to radiation damage with subsequent polymerization and has definite limitations as to maximum levels of temperature which can be achieved for the fission energy. It is understood that such a reactor is being investigated for commercial ship propulsion. The data and information collected to date at the University is limited. It is not possible to present any information regarding economic or possible advantages of such a reactor. 6.6 Sodium Graphite Heterogeneous Reactor Another type of heterogeneous reactor employing liquid metal utilizes a fuel element design of a graphite-uranium or a carbon-uranium solid solution fabricated into fuel elements properly clad with materials. A coolant presently proposed for this type of reactor is sodium. This type of reactor permits high-temperature gradients in the fuel itself, thus offering the opportunity of reducing reactor fuel costs to ranges competitive with fossil fuels. This reactor is being developed by North American Aviation and an experimental facility is being erected near Los Angeles. It is considered worth while to follow closely this phase of development for ultimate application to propulsion systems of high shaft horsepower. 6.7 Liquid Metal Homogeneous Reactor A ipromising high-temperature reactor which was originally developed by the Brookhaven National Laboratories offers considerable promise for the production of energy for many uses. Though this reactor has application for conversion and breeding, discussions in this report will be limited to the fissioning type of a reactor. In general, the flow system for a fissioning type of reactor is given in Figure.-5. 39

STEAM FIG.1 PREHE & WATER FLUIDIZED BED REACTOR SYSTEM I ENGINEERING RESEARCH INSTITUTE SATURATED UNIVERSITY OF MICHIGAN STEAM DRUM I FEED DESIGNED BY H.A.O. I WATER DRAWN BY R.I.K. PRE' IN CHECKED BY M.E.W. TUBES ALL METALLIZED TO REACTOR SEATOR WALL FROM PELLET W A MACHINE I0~~ | *)))) \ t | eO~~~~~VIBRATOR TO CHEMICAL FEED I PROCESSING H OPPR _CHROMEL ALUMEL O | I |I I| THERMOCOUPLE:::: I | FLUIDIZED BED I REACTOR SO IDS o SOFED 0 FLOW RECORDER CONTROLLER L: ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ NEUTRON REFLECTOR CONSTANT HEAD BOUNDARY OF GAMMA SHIELD

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN A solution of uranium dissolved in bismuth at high temperatures is a homogeneous solution. By.adjusting the uranium-235 concentration at proper levels, it is possible to flow this system into a critical geometry in which fission takes place. For applications of power production of moderate values approximately 4 to 6 megawatts and less, it is possible to consider the heat exchange surface constructed into the critical geometry of the fissioning core. For reactor heat powers greater than 6 megawatts, it might be necessary to provide an external heat exchanger with a circulating loop in which the bismuth is circulated at high velocities, presumably by a pump. The heat exchanger, whether in the reactor itself or as an external unit, provides the means for converting the thermal energy of fission to energy which can be used for power propulsion. An attractive means for this is to exchange the heat in the uranium-bismuth with a working fluid such as air, nitrogen, carbon dioxide, argon, and helium. Such a working fluid is compatible with some conceptual designs of a closed cycle gas turbine. Recent data resulting from cooperative efforts of the Brookhaven National Laboratories and industrial groups interested in power have found that temperature levels up to 1000lQC can be approached without danger or risk of high corrosion rates. Under these conditions, it is possible to conceive designs of a nuclear power plant of relatively small size. Of the reactor types discussed in this report, this system offers the greatest opportunity of early achievement of a nuclear power plant for propulsion and transportation systems over a wide range of shaft horsepower. The status of this reactor system must be considered in early stages of research and development. Therefore, much work in physical research, development, engineering, and safety must be done before final decisions can be reached. Investigations indicate that this type of a reactor might achieve low mass-to-horsepower ratios in the range of 500 to 25,000 shaft horsepower. Some of the relative advantages of this reactor are: 6.7.1 High-temperature operation. 6.7.2 Homogeneous fuel. 6.7.3 25,000 to 40,000 hours of continuous operation without necessity to remove fuel. 6.7.4 Maximum temperature established by uranium concentration in bismuth. 6.7.5 Control rods external of the reactor rather than in the core. 6.7.6 Low critical mass and low fuel inventory. 6.7.7 High heat transfer characteristics. Certain projections for capital and operating requirements indicate that for transportation purposes the liquid metal homogeneous reactor offers great promise of achieving a low initial capital cost as well as low 4.1

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN operating costs. It is believed that through intensive programs of research, development, and engineering studies, it would be possible to achieve a nuclear powered propulsion device that is not only technically feasible but that can compete economically with fossil fuels in certain horsepower ranges. It is urged, therefore, that consideration be given to the detailed experimental investigations that are needed for adapting this reactor concept for propulsion. 6.8 Molten Salt Homogeneous Reactor Another reactor of a very promising type to consider is a reactor which employs as a fuel a solution of uranium metal salts. The reactor system has all of the inherent characteristics and advantages mentioned for the bismuth-uranium reactor under 6.7 and essentially the same flow system applies. The inherent difference between this reactor and the bismuth-uranium react:or is the problem of materials of construction for metal fluoride salts at high temperatures. It is urged, however, that this reactor be given equal consideration initially to the bismuth-uranium reactor with a primary emphasis on developing materials of construction which will withstand the corrosion attacks of such salts as lithium- fluoride, uranium tetrafluoride at high temperatures. This reactor offers promise for application to propulsion devices in the range of 500 to 25,000 shaft horsepower with low mass to horsepower ratios. 6.9 Heterogeneous Gas-Cooled Reactor An ultimate attractive type of reactor system for propulsion devices is to consider a heterogeneous fuel core operating at high temperatures in contact with a high-pressure working fluid such as air, nitrogen, carbon dioxide, argon, helium, hydrogen, etc. In this case, this working fluid is the coolant as well as the possible working fluid for the turbo-machinery. The gas flows at high pressures through the critical geometry where the fission heat is removed. The exit gases flow to turbo-machinery in which at high temperatures such thermal energy is converted to mechanical energy. Such a reactor might operate either with an open cycle turbine or a closed cycle turbine, depending upon the shaft horsepower requirements. In general, it might be considered that open cycle turbines have application to horsepower ranges up to 6,000. The closed turbines for this type of reactor might have application for shaft horsepower requirements in excess of 6,000. The limiting conditions for this type of a reactor appears to be construction material. With presently available technology, thermaximum sheath temperature on the fuel element which can be attained is about 18000F. Thus, the temperature of the exit gases which can be achieved from such a reactor system might approach 15000F. At the present writing, no economic evaluations from either capital or operating costs for this reactor system have been made. It is believed that careful consideration should be given to all development now underway at various ACE sites for gas-cooled. rweactors with specific emphasis on physical research problems and evaluating and. developing high-temperature materials....... 42

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 6.10 Fluidized Bed Reactor For the past year, the faculty, staff, and students of the University of Michigan have given consideration to new conceptual designs for reactor systems. One of these reactors which is under consideration employs a fluidized bed of totally enriched uranium oxides as a powder suspended in a gas medium. Under critical geometry and critical mass, this powder can be expected to generate thermal energies at temperature levels approaching 25000F. The fluidizing gas is primarily provided to change the density of the solid, internally circulate particles and continuously remove fission products which are in the gas phase. A fluidized bed reactor could be largely self-decontaminating. Fines formed by the attrition of uranium oxide particles and fragmentation due to fissioning will be carried out of the reactor bed by the fluidizing media. At the same time, fresh uranium oxide can be added to the incoming fluidizing system, either continously or intermittently. Operated in this manner, the reactor is automatically relieved of spent fuel and recharged with fresh fuel continuously. Such methods would eliminate expensive and time-consuming charging mechanisms and procedures. Control of such a reactor can be accomplished by using standard control instruments. This system is indicated in Figure T. The fluidized bed is contained in the vessel with a conical top and bottom. The bed itself occupies about one half of the straight side volume. The vessel inner wall is constructed of firebox grade or low chromium steel. Heat transfer tubes are located within the critical geometry and fluidized bed temperatures are maintained between 2000 and 2500OF. Bed temperatures are measured and set the mass flow rate of the fluidizing gas. If the temperature increases higher than desired, the control instrument opens the regulating valve in the air-feed line. More gas flows through the bed expanding it until a critical geometry balance of the bed is reached. If an increase in bed temperature is desired, the instrument acts to decrease the fluidizing gas flow. The bed contracts giving greater excess reactivity and thus more heat generation. At the temperature levels indicated, heat transfer is accomplished by radiation. Heat transfer surfaces located in the reactor provide means for absorbing the thermal radiant energy. By passing a working fluid through the internals of puch tubes, it is possible to remove the fission heat into a gas stream and consider such working fluids for use in turbomachinery. This system must be considered as a pure research problem at the present time. No physical research has yet been conducted for this reactor concept. Since it is a type of a reactor which permits attainment of high temperatures for a fissioning reactor and since it has general application to propulsion machines in the range of 100 to 8,000 shaft horsepower, it is urged that serious consideration be given to investigating fundamental data and nuclear parameters for this type of a reactor. At the present time, it is not possible to indicate any economic figures. It should be kept in mind, however, that this reactor possesses potentiality of achieving low mass to horsepower ratios. I43

MAIN CIRCULATING L PUMP SHIELD RADIOACTIVE! ~STEAM RADIOACTIVE GAS STORAGE DRUM TURBINE PRODUCTS TO F.P. STORAGE T COOLING CONDENSER WATER MODERATOR SALT! CIRCULATING LIQUID METAL ],t ~FUEL SOLUTION ~~~~~FUEL ISHIELD MAKEUP FIG. 16 m SCHEMATIC OF LIQUID METAL FUEL REACTOR r FEEDWVATER PUMP fs X' ]

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 7.0 HEAT ENGINE CYCLES of fission into useable mechanical energy. In general, this problem is one of conversion of the energy from a nuclear reactor to useful mechanical work with as high a degree or utilization of such thermal energy as possible. Consideration must be given to such factors as cost, space, weight, reliability, life, and independence from coolant sources, all of which are important to varying degrees depending upon specific applications. The possible nuclear reactor heat to mechanical power conversion devices which can be of practical importance in the relatively near future are limited to heat engine cycles. Examples of heat engine cycles are steam turbine machinery, open cycle gas turbines, closed cycle gas turbines, reciprocating machines, etc. Such engines may employ as working fluids either those substances which do not undergo a phase change in the course o the cycle or those which do. Also, possibilities exist for employing cycles which utilize more than one working fluid such as the mercury-steam binary cycle or a gas-steam combination. In giving consideration to the research and development program outlined in this report, the general boundary conditions have been established which will permit obtaining thermal efficiencies approaching 40 percent or higher. In giving consideration to the various heat engines which might be applicable for transportation devices, preliminary surveys have been made for steam turbine machinery which does have application to propulsion devices such as merchant ships and certain sea going naval craft; to open gas cycle engines which might have application to utilization in aircraft and other gas turbine re-applications which require generally less than 6,000 shaft horsepower; and to closed cycle gas turbines which can have application to land transportation devices as well as to propulsion devices whose shaft horsepower requirements may approach 25,000 or higher. Since the reactor development programs which are outlined herein have as their general objective to achieve reactor temperatures of 10000C and higher and since commercial vehicles require absolute assurances of safety from radiation, it is believed that research and development programs for achieving an optimum closed cycle gas turbine in conjunction with a given nuclear heat power reactor will yield optimum results in applications of nuclear energy to fields of transportation. The closed cycle gas turbine continuously recycles the same working fluid from heat source to heat sink. If a highly effective heat recovery exchanger between the turbine discharge and compressor discharge is utilized as well as a compressor intercooling, the thermal efficiency of a closed cycle gas turbine may approach ranges from 40 to 50 percent, considering presently obtainable temperature and component efficiencies. The range of efficiencies appear possible only in fairly large turbine and compressor sizes. For smaller output powers where space and weight are not of great importance, it is conceivable that alternative heat engine applications may be worthy of consideration. A closed cycle gas turbine may 45

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN utilize a working fluid in which radioactivity is induced providing the turbine machinery and its auxiliaries are properly shielded for safety purposes. It is possible also tb select a working fluid which does not become radioactive in which case it would be necessary only to shield the reactor and its specific components. This report suggests initiating research and development programs as specifically applied to a heat engine of the closed cycle gas turbine type. The initial work projected confines investigations to the basic parameters of working fluid such as air, nitrogen, argon, carbon dioxide, helium, and hydrogen. Coupled with the research investigations of working fluid, it appears desirable to conduct basic investigations into materials which will contain these gases at high pressures and high temperatures and analysis of conceptual design for seals, stuffing boxes, and other points of a closed cycle gas turbine which might permit leakages of the working fluid to the outside. In the event that the investigations of working fluids, components, and materials prove successful, consideration should be given to the design, construction and operation of a closed cycle gas turbine of suitable size so that engineering parameters and materials problems can be evaluated for a performing turbine installation. The size of such a closed cycle gas turbine experimental unit should be selected to permit extrapolation of resultant data to turbine sizes and compressor sizes over a wide range of shaft horsepower requirements. _ _ _ _ _ _ _ _ _ _ __ L4 6