THE UNIVERSITY OF MICHIGAN INDUSTRY PROGIRAM OF THE COLLEGE OF ENGINEERING NUCLEAR EFFECTS ON CHEMICAL ENGINEERING J. J. Martin Professor of Chemical and Metallurgical Engineering H. A. Ohlgren Former Professor of Chemical Engineering October, 1958 IP-334

TABLE OF CONTENTS Page LIST OF TABLES.......... o.... o...... o o...o o. o. iii LIST OF FIGURES..OO.............o o a..... iv INTRODUCTIOciN.*oO~e.O eo oO*. O jO OOOOOOOeoo e o o0 0 0 0 * 1 NUCLEAR EFFECTS ON CHEMICAL ENGINEERING EDUCATION............. 2 1. Nuclear Physics.......................,.... O. 3 2, Thermodynamics eQo..... o.................. -..o.. 14 3. Unit Operations and Control.....O...................15 NUCLEAR EFFECTS ON PROCESS INDUSTRIES AND DESIGNS......,...... 17 lo Preparation of Fissile and Fertile Materials............ 17 2. Reactor Power Systems and Reactor Developments.........0. 25 3. Production and Processes for Nuclear Materialss......... 29 4. Reprocessing and Recovery of Nuclear Fuels.. **.......o..o o 32 CONCLUSIONS..... o........... * * q...o 36 REFERENCES.,aa..,a....,aa,,, a,. 6,... a. 38 ii

LIST OF TABLES Table Page I Elementary Particles of Matter...........o......... 4 II Types of Radiation.............................. III Typical Nuclear Reactions......0..oo....0.......... 7 IV Instruments and Techniques for Detection of Particles and Radiation..................... 11 V Chemical Engineering Operations and Equipment Developed in the Nuclear Fieldo....o................ 16 iii

LIST OF FIGURES Figure Page 1 Representative Fission Reaction.....o............ 9 2 Nuclide Chart..........0.0... 00.... 12 3 Control System for Process Heat Reactor. O..o..... 13 4 Nuclear Effects on Chemical Engineering - Milling and Concentration of Uranium............ 19 5 Nuclear Effects on Chemical Engineering - For Uranium Purification........... 21 6 Nuclear Effects on Chemical Engineering - Isotope Enrichment and Conversion to Reactor Fuel...... 23 7 A Typical Power Reactor System.................. 28 8 ~Nuclear - Heat - Power Demonstration Plant........... 30 9 Remotely Operated Reprocessing Systems - Impact of Nuclear Technology..........o.............O.. O. 34 iv

INTRODUCTI ON This is the atomic age. Newspapers, popular magazines,, and technical journals remind us of this fact every day, and maybe twice on Sundays when the special supplements and comics have their say. In atom-conscious sections of this country we may even hear fair, warmer, and roentgens per hour in every weather report. As chemical engineers, our reactions to this arrival of the age of the atom and nucleus are in many cases little different from those of the lay public. This may seem paradoxical, for after all, we have been educated in the physical sciences and should have a fair understanding of the implications of nuclear energy. The situation arises, however, from the simple fact that, although we are told this is the atomic age, there are still many amongst us (chemical engineers) who have not felt the impact of atom splitting either in business or in everyday life. Our closest contact with nuclear energy may well be during the inhalation of an infinitesimal trace of radioactivity resulting from the fallout of an atomic or hydrogen bomb which was set off in the Pacific Ocean or New Mexico or even Siberia; and in this instance we do not experience any noticeable effect. Pbwerful as it is and as far-reaching as it may be in its political and economic importance, nuclear energy is still somewhat remote in the daily life of the average chemical engineer. -1N

In considering the various ramifications of nuclear energy, it is not the purpose of this paper to discuss the political effects of atomic bombs or the effect of radiation on our genes, but rather to note how chemical engineering and the professional life of the chemical engineer are being or will be changed by the developments in the nuclear field. The handwriting is on the wall and we or our successors are bound to feel the influence of nuclear energy in the field of chemical engineering. This, of course, should not be surprising because chemical engineers have already played an important part in this new area. It is estimated that some two to three thousand chemical engineers now derive their employment in the nuclear field, and it is expected that this number will increase steadily in the next few years. Chemical engineering and nuclear energy are, therefore, just as surely entwined in the future as has been chemistry and engineering in the past. For purposes of this discussion the changes which are being brought about in chemical engineering by nuclear energy will be considered from two points of view. The first will deal with the changes in the curricula and education of chemical engineers and the second will treat the new industrial applications and techniques for which nuclear energy has been primarily responsible. Obviously, the two approaches go hand in hand with neither logically preceding the other. NUCLEAR EFFECTS ON CHEMICAL ENGINEERING EDUCATION It is naturally understood that many changes have been made in the courses and subject matter of chemical engineering during the past decade or two; however, our concern of the moment is only with

those which have resulted from the development of the atomic energy program. It should also be clear that not all schools have incorporated all of the following material into their teaching programs, for progress and change require time. 1. Nuclear Physics The embryo chemical engineer is not long on the campus today before his teachers of physics and chemistry are leading him through the realm of molecules and atoms to the nucleus. Although he is probably unaware of it, considerably more emphasis is placed on nuclear physics than was done with the generation of engineers before him. It is not possible to explain the whole field of nuclear physics in a few short paragraphs, but it is rather easy to present a few simple examples of the kinds of things on which the modern students attention is being focused. A survey of the kinds of particles of which matter is composed is usually covered early in order to give a feel for the ultimate structure of atoms and nuclei. Table I lists the most important particles which have been either discovered experimentally or postulated theoretically to explain the behavior of matter. Some of the particles are probably familiar and some are new to those who took their physics and chemistry more than a decade ago. The table is not meant to be complete for every few years there are additions, and as yet, there appears to be no end to the number and kinds of particles which physicists will discover. Of the many kinds of particles those with which the engineer is most often concerned are electrons, protons, neutrons; and alpha particles.

TABLE I ELEMENTARY PARTICLES OF MATTER Particle Mass, amu* Charge, e** Comments Electron 0.000549 -1 Beta particle Positron 0.000549 +1 Proton 1.0076 +1 Hydrogen nucleus Antiproton 1.0076 -1 Neutron 1.oo89 0 Important in fission Antineutron 1.oo89 0 Deuteron 2.0142 +1 Heavy hydrogen nucleus a-particle 4.0028 +1 Helium nucleus Neutrino 0 0 Needed for momentum balance t-mesons 0.144 to O.149 +l,-1l,or 0 Binding material for — mesons 0.113 +i,-l,or 0 neutrons and protons * 1 amu (atomic mass unit) = 1.66 x 10-24 gm ** e (electron charge) = 4.8 x 10-10 esu

Any treatment of the behavior of particles leads directly to a discussion of radiation. As shown in Table II, radiation falls into two general classes, corpuscular (particle) and electromagnetic (no mass). The properties and sources (i.e., accelerators, radioactive isotopes, fission reactions, etc.) of the various kinds of radiation are consideredwith the interaction of radiation and matter constituting one of the most fundamental aspects of nuclear science. For the average engineer the treatment must necessarily be brief, but if there is exceptional interest in the nuclear field, the student can take an elective course dealing with radiation and matter. On the theoretical side he can elect a course in quantum mechanics which helps to explain many of the phenomena, though this would rarely be done by an undergraduate chemical engineer. Nuclear reactions are taken up after the properties of particles and radiation are understood. Table III presents several typical nuclear reactions. It will be quickly noticed here that conventional chemical reaction nomenclature is replaced by a new scheme of subscripts and superscripts. The superscript on the right side of each nuclide is its mass number, A, and is the sum of the number of protons and neutrons in the nucleus. The subscript on the left of the nuclide is the atomic number, Z, which is the number 'of protons in the nucleus, or the positive charge of the nucleus which, in a neutral atom, is balanced by the negative charge of the surrounding electron cloud. For the reactions of ordinary interest the sum of the superscripts and subscripts respece tively must be the same on both sides of an equation when proper account is made for the coefficients mod-ifying each term. This means that the

TABLE II TYPES OF RADIATION Energy, Mev Comments ELECTROMAGNETIC Gamma 0.01 to 5.0 Extremely penetrating and X-ray lO-4 to 10-3 will ionize. Ultraviolet 10-6 to 10-5 Stopped by optically opaque Visible light 10-6 substances and insufficient Infrared 10-7 to 10-6 energy to ionize. Cerenkov lo0-6 Secondary due to fast particles. CORPUSCULAR Alpha 2 to 400 Principal particles given off Beta 10'5 to 250 during radioactive decay. Deuteron 0.07 to 3000 Proton 0.07 to 3000 Neutron 0.02 to 10 Liberated during fission. Heavy charged up to 6000 May be product of fission or particles accelerator.

TABLE III TYPICAL NUCLEAR REACTIONS Reaction Comments 1) 92U235 + onl. 54Xe141 + 38Sr92 + 3.0n Fission 2) 92U38 + on1 g 9239 + Scheme for production of plutonium 93Np239 + -1fO i94Pu239 + _15~ / 32U235 + 2He4 3) 7N14 + n - N15 + 7 (n, y) 4) 7N14 + n1 6C14 + 11 (n, p) 0 -* 5) Li6 + nnl1 1H3 4 (n, a) 3 o0 1+ 2He (n,.) 6) 1D2 + 3Li6 - 22He4 Fusion 1 32

total numbers of protons and neutrons remain unchanged during nuclear reaction. As an example, in the fission reaction of U235 the mass number balance is 235 + 1 = 141 + 92 + (3 x 1), and the atomic number or proton balance is 92 + 0 = 54 + 38 + (3 x 0). Figure 1 illustrates schematically one of sixty possible nuclear reactions which occur when fission occurs in U235. This figure shows two fission fragment nuclei being material products, three prompt neutrons which are available for sustaining fission and gamma radiation. Certain fission fragments are neutron producers. Such neutrons are termed "delayed" neutrons and provide one means for mechanical control of thermal and intermediate neutron energy reactors. The conditions under which the various nuclear reactions proceed are worthy of considerable attention, particularly in the case of the fission reaction which is more or less responsible for the growth of the nuclear field. Understanding the sustaining of a fission reaction requires a knowledge of fast and slow neutrons and their diffusion, neutron production and absorption, nuclear properties of materials, and criticality. An intensive study of these factors can be given only in a special course which again would be elected by very few undergraduate students. In addition to fission, particular attention is paid to disintegration reactions of single isotopes, which are responsible for radioactivity. This is exemplified in Table III by 93Np239 which decays to 94Pu239 while emitting a beta particle (electron). The half-life of 93Np239 is 2.3 days while that of 94239 is 24,000 years, so the relative stability of these two isotopes can easily be compared.

onl fission fragments 5 4Xe-4 incident neutron O - U235 nucleus Key: Sr92 * Proton o o Neutron %' Gamma Ray Figure 1. Representative Fission Reaction

-10 -For ordinary chemical reactions, the periodic chart of the elements has been most useful. In the same way nuclear reactions can be better understood and correlated on a chart of the nuclides. The General Electric Chart is typical of several which have been developed and a section of this is shown in the upper part of Figure 2. By means of the lower part of Figure 2, one can see how a given nucleus may be transformed to another via various nuclear reactions. In the course of studying particles, radiation, and nuclear reactions, it is expedient to include some discussion of the instruments used for detection. Table IV lists the more important instruments and techniques used to detect and measure radiation. The principles behind the instruments are discussed briefly and an occasional laboratory experiment may be run to demonstrate their use. For example, a simple ionization chamber or Geiger-Muller experiment may be carried out on the radiation from a luminous-dial wrist -watch. The coupling of instrumentation for particle detection and measurement with more conventional instrumentation and control systems for processes requires extensions of knowledge and experience for the process engineer. Consider a simple system of a reactor, heat exchanger and pump loop for transport and transfer of nuclear process heat for steam generation. The systems control and instrumentation to couple heat generation and conversion with nuclear measurements impose new problems and extension of knowledge. Such a systems control is illustrated in the Figure 3.

-11 -TABLE IV INSTRUMENTS AND TECHNIQUES FOR DETECTION OF PARTICLES AND RADIATION Instrument or Technique Comments Cloud chamber Observe nuclear reactions in vapor Bubble chamber Observe nuclear reactions in liquid Ionization chamber Detect radiation by ions formed Pulse instrument Detect radiation in pulses Proportional counter Pulse heights depend upon -energy Geiger-Muller All pulses same magnitude Scintillation counter Radiation detected through light emitted Photoelectric cell and Absorption of radiation photons photomultiplier tube causes electrons to be discharged BF3 proportional counter For detection of neutrons Fission ionization chamber For detection of neutrons Neutron thermopile For detection of neutrons Photographic emulsion Detects all forms of radiation Foil activation Determine radioactivity induced by neutrons Chemical dosimeters Measure radiation by chemical reaction Associated electronic devices: Linear amplifier Amplify extremely small currents or pulses Scaling circuits Select certain percent of pulses Dlscriminator Select certain energy pulses

Relative Locations of the Products 0 0 14 16.0000 76 of Various Nuclear Processes * 21.8 N b N 12 (N 13 57 E2 N 8.8 1.23 | ~out gC n in 41 2 - - ain, 16.6 no ' m ml -l~~~~~ -~ 1 | Li | ~LI~6 6 1 17 5 20.5L 98.9i a:out ni* eutron H" 2.2 H Ip ~proton nY -1 no r |C| o dut p er in nd in B - - = alpha particle L Qo.,5m K-H K-electron capture - Figure 2. ucl18.i8 81.2,,,t O'"'""' Be 'LB 7 ~ Be e "Be 10 52.9 d io-20S 100 2 106 Iy Nucleus 1.48 GD n Li. Li 6 Li 7.Li 8 n no y H N*o 3 He 4 (He 6.5r 4 4003.00013 -100 2. 0 G)oo> noo 1.0080 -100 6016 124i y negative beta particle P46 positive 4 3 5 a K-electron capture A-Z HH$,1 Fi:ure 2. Nuclide Chart

THERMAL POWER CORRECTION INSTRUMENT TO BALANCE NEUTRON a8 HEAT COMPUTER THERMAL POWER. BTU /UNIT TIME NEUTRON CONTROL On QWCpdT PAVEI RODS I CHEMICAL PROCESS REACTOR HA r HEAT~~~~~~~~~~~~~~~ AMPLIFIER I CORE NEUTRON COUNTER HEAT EXCHANGER P'nvZ f Pt POWER PUMP nv =FLUX f xMACROSCOPIC FISSION CROSS SECTION REF. SCHULZ P. 209 E *ENERGY RELEASE PER FISSION Figure 3. Control System for Process Heat Reactor

_14 -This diagram illustrates a typical nuclear-heat system wherein a continuous calibration of reactor power level is required. A heat computer can be used to measure the heat extracted by the heat exchanger. In essence, such a measurement is achieved by computing the heat extracted by determining coolant flow rate and temperature differences. The neutron power is determined by one or more neutron measuring devices. The neutron measurements are amplified and correlated with the heat or thermal power by a comparator (which corrects and calibrates neutron power with heat power). The output of the comparator feeds back and corrects the neutron detection. The resultant measurements can be used for adjustment and control movements. Similarly, in an electrical powerplant, the feedback from turbine throttle can be coupled into the nuclear system for adjustment of reactor power level. 2. Thermodynami cs The engineer further requires insight into thermodynamics in terms of nuclear energy. Although it was undoubtedly introduced earlier, the Einstein concept that energy is merely another manifestation of matter will be emphasized, and the first law of thermodynamics re-stated to say that it is the sum of mass and energy which is always conserved. A simple calculation can be made from the well-known equation, E = mc2, to show that the mass change in an ordinary chemical reaction is so negligible as to be beyond detection. Thus, if a fuel with a heating value of 20,000 Btu/lb is burned, the loss of mass from the system containing the fuel and its required air is E (20,000 Btu)(980 gm-cm/gm force-sec2) mc2 -3x1010 cm/sec)2(454 gm/lb)(9.486xlOl11 Btu/dyne-cm)(980 dyne/gm force ) = 5.2x0o-1~ lb

-15 -It is clear that this is far beyond the ability of the finest balances to detect, so that it is justifiable to say that in chemical reactions there is no change of mass. In nuclear reactions the associated energy changes are of the order of a million times those of chemical reactions. Appreciable energy changes are, therefore encountered and must be taken into account. A very interesting aspect of the Einstein relation is that if both the system and its surroundings to which energy is transferred are considered, there is no loss of mass whatsoever. This is because the mass loss of the system due to its energy loss is exactly matched by the mass gain of the surroundings due to the energy gain of the surroundings. Except for energy in transit, the total mass of the universe is constant. From another 'point of view, one can say that for ordinary so-called "pure energy" transfers there is always an accompanying transfer of mass, though the transfer of mass is normally of minute proportions. This obviously is the reason the Einstein relation has not been given much attention in thermodynamics courses until the development of the nuclear energy program where nuclear reactions involving tremendous energy transfers are common rather than rare. 3. Unit Operations and Control The chemical engineer also feels the impact of nuclear energy in the field of unit operations and process control. Special requirements have forced the chemical engineers working in the nuclear field to develop new equipment and new procedures as solutions to its problems. Table V presents some of the more important of these operations which are gradually being absorbed into modern chemical engineering courses. In many cases the operations are being adapted to conventional processes. It can be expected that within a few years most of these operations will be as familiar to chemical engineers as ordinary heat transfer.

-16 -TABLE V CHEMICAL ENGINEERING OPERATIONS AND EQUIPMENT DEVELOPED IN THE NUCLEAR FIELD - 'l::, r. -.m ' ' - - -.' ', -' * - '.m ' i,, -, '..i -... -:' ';,'... ' ",::.. '- -. -,, r ' Operation or Equipment Comments Barrier diffusion Principle means of obtaining U235 Gas centrifugation For general isotope separation Gas thermal diffusion For general isotope separation Pulse columns For liquid-liquid extraction Ultra-low-temp. distillation For separating heavy hydrogen Ultra-high-temp. distillation For purifying metals High decontamination evap. For removing radioactivity from solutions Liquid metal heat transfer For heat transfer at high temperature Electromagnetic pumps For moving liquid metals Pressurized water systems For improving heat transfer Remote control handling For operations behind shielding Radiation sensing gauges For liquid-level7 thickness, and flow meas. Micro-analytical control Process control with micro amounts Neutron-analytical control Control standards based on neutron absorption Materials of construction re- Materials required for the cores of sisting radiation damage and nuclear reactors and for use in regions with low neutron absorption of intense radiation Special storage systems For storing radioactive materials safely Radiation chemistry and Special attention is given to radiation irradiated catalysts as a potential process variable Ion exchange Unusual applications in intense radiation _ __ I'............

-17 -NUCLEAR EFFECTS ON PROCESS INDUSTRIES AND DESIGNS The chemical engineer practicing his profession in any one of the many industries contributing their efforts to the enhancement of nuclear energy, finds it necessary to broaden his background and fields of interest as well as probe into the depths of knowledge. In general,, areas requiring extension of knowledge might be classified as follows: a. Nuclear physics b, Operational mathematics c. Reactor theory d. Interactions of radiation and matter e. Nuclear instrumentation and control f. Shielding g. Nuclear process design Such increase in depth of knowledge and broadening of background and experience are essential for the achievement of nuclear processes which are technically feasible, "safe in operation," and possess economic potential with maximum flexibility. To illustrate such "nuclear" effects on systems and processes that involve radiation, neutrons, particles and neutron reaction rates in an overall system, the following areas have been selected for discussion. 1. Preparation of Fissile and Fertile Materials Uranium and thorium are found in nature in concentrations comparable to the range of concentrations of chemical waste streams, As an example, in many uranium deposits, such as the carnotite ores, the uranium concentration will range from.1 to 1%g. Processes must be

developed wherein this low grade material is upgraded to a purity of 99.99% and in which isotopes are separated in relatively pure form. Present day practice consists of the following steps. a. Ore Concentration. —In ore concentration, the chemical engineer has been required to develop process systems in which microchemistry is conducted in production-scale flow systems where many degrees of conversion are required in the separations technologies employed. As an example, in a solvent extraction system, the solvent extraction columns for the recovery of uranium must provide a product of uranium which has a purity of 99.99% or better while the losses of uranium from the system must be accountable within 0.1%. While such processing improvements and higher degrees of purification are being effected, the chemical engineer must give Consideration to radioactive contaminants in certain components existing in the ore. A good example is the uranium ores obtained from the Belgium Congo which contain significant quantities of radium so that, while upgrading the concentrate, consideration must be given to the hazards of radiation and the provisions of structural shields for the protection of health and radiation safety. Figure 4 illustrates some of the nuclear effects involved in the treatment of uranium ores which contain limited quantities of radioactivity. The presence of radiation not only permits discovery of new ore deposits but must be considered in terms of radiation health, control of radioactive particuJlates, partial shielding as radioactive materials become more concentrated, methods for remote mechanical handling, methods for decontaminating equipment, structures, clothing

EXAMPLE - ORE CONTAINING RADIUM (REFERENCE - U. S. BUREAU OF MINES) ORDINARY CHEMICAL ENGINEERING PROBLEM ADDED NIUCLEAR EFFECTS MATERIALS HANDLING MOVING MATERIALS RADIATION HEALTH SIZE SEPARATION & CLASSIFICATION RADIOACTIVE PARTICULATES RADIANT & CONDUCTIVE CRUSNG, GRIDING,. SHIELDING STRUCTURES & CONVECTIVE HEAT TRANSFERAND CLASSIFICATION DIFFUSIONAL OPERATION DECONTAMINATION DIFFUSMIVITY MICROCEEMICAL ANALYSES I PRECIPITATION ROASTING & CALCINING RADIOACTIVE DISPOSAL FILTRATION S. F. ACCOUNTABILITY EVAPORATION DRYING SEPARATIONS RADIUM VANADIUM URANIUM CONCENTRATES Figure 4. Nuclear Effects on Chemical Engineering - Milling and Concentration of Uranium.

-20 -and wastes. In addition to the problems of radiation, the process concepts must be extended to provide means for essentially complete recovery of all the uranium in as pure a form as possible. b. Conversion of Uranium to Nuclear-Grade Metal., Metal Oxides, Metal Fluorides, and Other Compounds. —The processes which have been developed for such concentration involve basically reaction rate data, solvent extraction, evaporation, denitration, hydrofluorination, and reduction operations as well as fluorination reactions. Such concentrations have a two-fold application: (1) the preparation of a material in such chemical form that isotopic separations of uranium-235 from uranium-238 will result; (2) the production of nucleargrade structural materials such as natural uranium fuel for power reactors, breeder blankets for fast reactors,- and special shielding materials. Figure 5 illustrates some of the nuclear effects in achieving feasible process designs for feed materials preparation and nuclear-grade natural uranium for reactors. This figure illustrates a typical dissolution, solvent extraction and conversion process for production of uranium as metal, oxide, or hexafluoride. Since the product has high value the process requires complete accountability of uranium in all process streams (which in essence is microchemical control in production processes), separation factors for recoveries of 99% or higher, unusual control of waste streams, and special materials of construction. In each of these cases, the processes must be conducted under conditions so that the product possesses purities normally foreign

(ASD ON FLOWHEETS PUBLISHED BY BEMEDICT & PIOGrRD) ORDINARY CHEMICAL ENGIEIRING DISSOLUTION OF URANIUM NUCLEAR EFFECT8 CON CIENEATES 1. REACTION DATE DATA 1. NUCLEAR ACCOUNTABILITY 2. OFF-OAS PROCESSES 2. MICROCEMISTIRY IN PRODUCTION CHEMICAL ADJUSTMIIFTS PROCESSES 3. CHEMICAL ADJUSTIT CONCElMRATION, pH 3. DECONTAMINATION IN PROCESSING 4. CEMCAL T eDYNMIcCS. CONTAMINAION IN MAI CE SOLVENT EXRACTION 5. EQUILIBRIUM DATA 5. NIIC SEPARATION FACTOR 99.99% rWOaIRY 6. HEAT TeANSFER 6. PROIDET P1,RITY 7. MASS TANSFER & DIFFUSIONS STRIPPING NTCL3A CROS S-CTION 8PECIFICATIONS 8. OXIDATION-REDUCTION POTENTIALS 7. PARTICULATE REMOVAL 9. SOLVENT RECOVERY EVAPORATION 8. HIGH-COST SOLVENiT H 10. EVAPORATION 9. PRED MIED PARTICLE SIZE 11. REACTION RATES8 & ACID RECOVERY & DENSITY CONTIOLS DENITRATION 12. CHEMICAL REACTIONS, DlESITY 10. ISOTOPIC. ANALYSES SIZE CONTROL REDUCTION TO U02 U02 HYDROFLUORINATI ON METAL PRODUCTION FLUORINATION TO UF6 Figure 5. Nuclear Effects on Chemical Engineering - For Uranium Purification.

-22 -to chemical engineering processes. The recoveries must be complete so that waste solutions do not prompt pollution problems in either atmosphere or in liquid form. Since the value of the products lies somewhere in the range from $2 to $100 per pound, unusual precautions must be taken in process inventory, process recovery, and product handling systems. c. Gaseous Diffusion. —Most power reactors in the United States, at least, are directed toward a degree of isotopic enrichment of the fissile species, uranium-235, so that smaller, more compact reactor.ystems can be achieved. Isotopic separations in the main consist of the conversion of uranium to uranium hexafluoride which, as a gas, can be cascaded through several thousand diffusion cascades to enrich uranium-235 from 0.71% to some specified enrichment lying somewhere between 1 to 93.4% as uranium-235. The diffusion cascades, as a consequence, require special materials of construction, special diffusion barriers, and numbers of cascades ranging in the thousands.(l) Figure 6 serves to illustrate some of the special nuclear problems which must be considered in view of process engineering in isotopic separations employing gaseous diffusion and resultant conversion of uranium hexafluoride to fuel form. In addition to applying the nominal chemical engineering principles to the gaseous diffusion cascade attendant with the numerous problems of pumps, controlled atmosphere, materials of construction, etc., nuclear problems have been imposed. As the uranium becomes enriched in the isotope U-235, there is an increasing problem of geometry so that the system will be maintained as a subcritical system throughout the process. The chemical engineer, therefore, must be in a position

ORDINARY CHEMICAL ENGINEERING UF6 (0.71% U235) NUCR FECTS 1. DIFFUSION RATES ( 1. NEUON DIFFUSION 2. SEPARATION FACTORS 2. ISOTOPE CONTROLS 3. MINIMUM VS. PRACTICAL STAGES 3. CRITICAL GEOMETRIES 4. STAGE EFFICIENCIES ( 4. IITERACTIONS 5. HEAT TRAmSFER 5. THOUSANDS OF STAGES 6. CORROSION 6. CROSS-SECTION DATA 7. GAS HANDLING 7. MICROCHEMICAL ANALYSES 8. FLUID MECHANICS 90 35 8. ENRICHMENT FACTORS ro 9. RATE THEORY DEPLETEDURANIUM 9. ACCOUNTABILITIES W 10. MATERIALS HANDLING 10. NUCIEAR WASTES ONVERSION 11. INFINITELY SAFE GEOMETRIES TO BLANKET'TO METAL, FERTI2 E OXIDES, CARBIDES, MATERIALS AND ALLOYS SHIELDING FISSILE MATERIAL ETC. TO BREEDER REACTORS TO BURNER CONVERTORS Figure 6. Nuclear Effects on Chemical Engineering - Isotope Enrichment and Conversion to Reactor Fuel.

to calculate critical geometries, critical mass, neutron interreactions, nuclear diffusional phenomena, and many other problems unique to the nuclear energy program. The conversion of uranium hexafluoride to metals metal oxides, metal carbides and other uranium compounds imposes new problems on the chemical engineering process systems employed for such conversion. Since 1 gram of uranium-235 is equivalent to about 3 tons of coal, or 600 barrels of fuel oil, the chemical process must be one which accounts for every gram of uranium-235 in the system. For fully enriched uranium systems, the processes must be conducted in equipment which is either "geometrically safe" at all times or in "unsafe geometries" wherein uranium-235 concentrations are controlled in each step of the process. The new knowledge, therefore, involves a high degree of recovery coupled with criticality controls. Special processing techniques and methods must be employed for the physical handling, packaging and shipment of an enriched product for reactor fuel fabrication. d. Fabrication of Reactor Fuel Elements and Reactor Fuel Solutions. —Since the nuclear power programs include reactors which have fuels in solid form, as aqueous salt solutions of uranium, and liquid metal solutions of uranium, the processing techniques for assemblage and preparation of reactor fuels has had considerable effect on the chemical engineering process system. These include: (1) selection of fuel form, such as uranium metal vs. uranium dioxide or some other compound; (2) the selection of structural cladding material because of the chemical instability of uranium and uranium compounds

in reactor coolants, as well as the containment of fission products in a power reactor; (3) the analysis of impurities which have high probabilities for neutron absorption in both uranium fuel-bearing materials and fuel structural materials; (4) chemical and metallurgical bonding of fuel structural materials to fuel materials for optimum heat transfer; (5) control of atom concentrations as a function of temperature limits of the system, solubilities as temperature functions, and thermal stress problems in transient behavior systems. In the areas of nuclear energy which involve the conversion of fissile and fertile materials to reactor fuel form we see that the chemical engineer in process designs and process developments must give consideration to an increased number of new variables which basically involve nuclear interreactions, as contrasted to chemical reactions, such as radiation problems, shielding, higher degrees of purity than heretofore required, and new principles of health and safety. 2. Reactor Power Systems and Reactor Developments Nuclear reactors are assemblages of fissile and fertile materials coupled with coolants, reflectors, moderators, neutron and biological shields, wherein the assembled system produces heat with unlimited temperature ranges, neutrons, radioactive fission products, beta particles, gamma rays, neutrinos, and new fissile species. Such nuclear heat source devices are useful in the generation of power, chemical process heat, radioisotopes, fissionable materials production and an unusual flexible combination of useful purposes. Alvin Weinberg, Oak Ridge National Laboratories, has indicated that there are possibly

20 to 25 thousand possible reactor concepts. He further states that there are several hundred physical concepts worthy of consideration, of which perhaps 10 to 20 may result in economical power plants and heat sources. In order to reduce the number of theoretical concepts to practically feasible systems which possess economic potential, it becomes necessary to combine conventional engineering disciplines with comprehensive understanding of nuclear phenomena. Many chemical engineers have adapted their backgrounds and knowledge with experience and qualification to make major contributions in this field. It is interesting to note that the generalized diffusion equations and slowing down models have had to rely fundamentally upon the early developments of heat conduction equations and principles of mass transfer. As an example, the time-rate of change of neutron density in a given volume is equivalent to the number of neutrons absorbed in a given volume per second plus the net number of neutrons escaping from a given unit volume per second, less the number of neutrons which are produced in that given volume. Mathematically, we write such an expression as follows: - T (rt)dr = aaC(r,t)dT + V-j (r,t)d- - S(r,t)dT Solutions to such general mathematical expressions are dependent upon the relationship between neutron currents and the gradient of flux in terms of Fick's Law and bear a similarity to the equations developed for heat, mass and momentum transfer. By the insertion of proper boundary conditions and separations of variables, it is possible to obtain solutions which predict the gradients of neutron flux and the

-27 -critical parameters of the system. In order to solve such problems, it requires that the neutron balances and fluxes be determined in proper energy groups, dependent upon the selection of the materials comprising a nuclear power system. Upon obtaining reference design considerations which define the dimensions of a power reactor fuel, the fuel concentration, and the selection of reflectors, it is necessary to couple such nuclear variables with variables of heat transmission, variations in coolant flow and changes of fuel with time. Although it is not possible to discuss these interrelationships in detail and since they vary from one reactor concept to another, Figure 7 indicates a typical power reactor system using the boiling water principle as developed by the Argonne National Laboratories and as now being developed extensively by the General Electric Company for application to power reactors. It should be noted from this figure that this is a typical boiling water heat cycle for the generation of power in which the heat source component is a reactor and conventional saturated steam turbomachinery comprises the powerplant. The conventional engineering problems involved in the design of such a powerplant are indicated in the figure and include considerations of heat conduction, nucleate boiling, fluid mechanics, methods and processes for purification of water, thermal stress considerations, heat cycle analysis, process controls and instrumentation, and other major problems. In addition to these conventional problems, the "reactor process engineer" must depend in the main upon new knowledge which must be coupled with the conventional process variables in which he is concerned with the effects of criticality and excess multiplication constants in terms of all of the

A TYPICAL POWER REACTOR SYSTEM* EXAMPLE: BOILING WATER - STEAM CYCLE POWER PLANT NUCLEAR EFFECTS ON SOME CONVENTIONAL PROBLEMS FEED BACK CONTROLS SOME NUCLEAR PROBLEMS I SSTEAM 1. HEAT CONDUCTION 1. NEUTRON DIFFUSION 2. NUCLEATE BOILING NEUTRON SHIELD THRO 2. COLD & HOT 3. FLUID MECHANICS BIOLOGICAL SHIELD CRITICALITY 4. OFF GAS r- __ 3. NEUTRON ENERGY SPECTRA 5. WATER PURIFICATION - NEUTRON BALANCE 6. THERMAL STRESS P O I 4. FUEL ENRICHMENT 7. HEAT CYCLE ANALYSIS I Il5CONTROL RODS 5. RESONANCE ESCAPE 8. VACUUM CONTROLS I I,TURBINE PROBABILITY 9. CYCLE EFFICIENCY I 6. MAX. ALLOWABLE FUEL 10. THERMAL TRANSIENTS I BURNUP CONVECTIVE HEAT IS 7. RADIATION DAMAGE TRANSFER I DRUM 8. FORMATION, BUILDUP 11. PUMPING CTR I & DECAY OF FISSION 12. CONVERSION PRODUCTS 13. SYSTEMS OPTIMIZATION I CORE I ONDENSER 9. ISOTOPIC CHANGES 14. OFF-PEAK PERFORMANCE I I C OLANT IN FUEL n> 15. PROCESS CONTROL I I 10. PLUTONIUM CONVERSION INSTRUMENTATION 11. FILM BOILING & HOT 16. POWER PLANT DYNAMICS I I CHANNEL FACTORS 17. PRESSURE VESSEL DESIGN I / INTER 12. THERMAL TRANSIET 18. MASS TRANSPORT.CHANGER EFFECTS ON REACTOR 19. RATING HEAT EXCHANGERS THERMAL KINETICS 20. PRESSURE DROP - PRESSURE SHIELD BOILER 13. TEMPERATURE COEICINTS RATIO CORRELATION FEED FEED WATER 14. DENSITY & FISSION 21. CAPITAL COST ESTIMATES PUMP MAKEUP PRODUCT COEFFICIENTS 22. ECONOMIC STUDIES 15. REACTOR CONTROL & I| j { \ |~~~~~~~~~~~~~ NEUTRON LEAKAGE 16. RADIOACTIVE STEAM & CIRCI PUMP DECAY _I~~~~~ [..~~~~~~~~~ J17. REMOTE FUEL LOADING SHIELDING j & UNLOADING 18. EUTRO SIELDING 19. BIOLOGICAL SHIELDING * OF-PRENCE: 20. GAMMA HEATING EXPERIMENTAL BOILING WATER REACTOR, 21. RADIATION MONTORING REPORT NO. ANL-5607, 1957. HEALTH PHYSICS Figure 7. A Typical Power Reactor System.

variables of the system. There have been listed 22 areas to. which a process engineer must give consideration when dealing with the develop ment of power reactors themselves. As a result of coupling conventional engineering and fully realizing the necessary effects from nuclear technology, it becomes possible for the chemical engineer to give consideration to multiple purpose nuclear heat power systems, as illustrated in Figure 8. This is an example of a typical high temperatures nuclear heat source adapted for possible application in.a typical chemical or petroleum plant wherein it is desirable to utilize nuclear process heat for chemical reactions while producing high temperature, high pressure process steam and the necessary power requirements for a given number of chemical process systems. In order for such a nuclear heat power concept to have utility in chemical and petroleum product manufacture, it becomes necessary to optimize simultaneously a complete economic balance around the chemical plant while giving consideration to the interreactions of neutrons, gamma radiation, and fission fragments for certain specific types of useful chemical products. 3. Production and Processes for Nuclear Materials Another very important area for the successful growth of nuclear technology which has had significant effects upon the chemical engineering profession is the processing of special nuclear materials and the production of nuclear-specification products for use in reactor programs. These processes and productions might be identified as follows. a. Processes and Production of Zirconium and Hafnium. — Zirconium metal has useful applications as fuel element cladding material in many types of reactor systems. In addition to useful chemical, physical, mechanical and metallurgical properties zirconium has an

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absorption cross section in the thermal neutron energy range of 0o.18 barns. To achieve a reactor material which has an absorption cross section in this range, it has been found necessary to develop chemical processing techniques for the selective separation of hafnium from zirconium. Although a number of separation techniques have been employed for such separations, the solvent extraction of thiocyanates with hexone (ref. Benedict and Pigforda p. 169) illustrates the nuclear effects- upon chemical technology. This method, in principle, consists in separating hafnium from zirconium by means of such a solvent as hexone so that the hafnium concentrates preferentially in the organic phase while leaving the zirconium in the aqueous phase. By giving consideration to the nuclear properties of the system, it became possible to produce commercially relatively large quantities of hafnium-free zirconium which contains less than 0.005% of hafnium. Thus, a process was effected whereby the zirconium became a useable nuclear fuel construction material and the hafnium possessed properties as excellent control rod material for reactors. b. Production of Deuterium and Heavy Water. — Since heavy water is an excellent moderator for those types of reactors where a high degree of thermnalization is desired, such as a natural uranium reactor, the process engineer was confronted with the problem of developing process systems whereby a high degree of purity of either deuterium and/or heavy water could be obtained for use in such types of systems. Processes have been developed for the production of heavy water at produetion rates and costs which make certain types of natural uranium reactors feasible.

-3a2 -c. Process and Production do-Special Solvents. —In solvent extraction technologies using aqueous systems for the recovery of uranium, thorium, plutonium,., and radioactive nucli des the nuclear technology has imposed the problem on the chemical engineer to develop special types of solvents of high purity, such as diethyl ether, hexone, tributyl phosphate, special kerosene fractions, chelating agents, and special materials with variable oxidation reduction potentials. 4. Reprocessing and Recovery of Nuclear Fuels The power reactor programs throughout the world involve numerous types of fuels concepts for reactors in which each specific type requires special consideration of metallurgy and materials engineering, unique to a given specific type of reactor. In addition, the reactor types areFissioning reactors or burnup reactors Convertor single-region reactors Fast breeder reactors Thermal breeder reactors Consequently, the process engineer who is required to develop systems by which fissile and fertile materials can be recovered, recycled and/or sold,and dispose of radioactive fission products in gaseous, liquid, and solid form is confronted with combining special nuclear problems with conventional chemical engineering. Each type of reactor fuel, therefore, possesses challenges of unique problems in which the impact of nuclear technology can control the selection of process variables, capital and operating costs. There are numerous chemical engineers practicing professionally today who have acquired unusual and unique

-33 -backgrounds for the development of process systems for the separation and recovery of various materials discharged from nuclear reactors. Floyd L. Culler (ref. General Economics of Chemical Reprocessing Using Solvent Extraction Processes, 1958 Nuclear Congress, Preprint 22) has discussed a number of aqueous chemical systems which involve the coupling of dissolution and solvent extraction for the separation of fissile and fertile materials from fission products. S. Lawroski, of Argonne National Laboratories, has presented information describing special volatility techniques for conversion of uranium to uranium hexafluoride, permitting either recycle to gaseous diffusion or reconversion back to fuel form. Ercole Motta, North American Aviation, has discussed aspects of pyrometallurgical techniques wherein high degrees of decontamination have been achieved by special metals extraction processes. The Brookhaven National Laboratories have developed unique systems for the recovery of fissile and fertile materials from liquid metal-fueled reactors. Although it is not possible to discuss the enumerable multiple materials and metallurgies confronting such engineers, an example will illustrate the nature of the impact of nuclear technology on process considerations. Figure 9 indicates in general the type of remotely operated reprocessing system for a specific type of fast power breeder reactor system. Such a system is considered extremely important to the fissile and fertile materials power economy of this nation and of modern civilization. Chemical and nuclear engineers have coupled their efforts in several locations throughout the country whereby

CONVENTIONAL PROCESS PROCESS HEAT NUCLEAR EFFECTS ON CONSIDERATIONS & POWER PROCESS VARIABLES RADIOACTIVE 1. CHEMICAL THERMODYNAMICS OFF GAS 1. BURNUP CYCLES 2. REACTION RATE CONSTANTS 2. RADIOACTIVE DECAY & 3. MASS TRANSFER FUEL COOLING 4. FLUID FLOW _ 3. ISOTOPE BUILDUP & DECAY 9. PROCESS SELECTION 4. FISSILE ATOMS 6. TECHNICAL FEASIBILITIES REACTOR CORE & CORE GROSS ACCOUNTABILITY 7. PROCESSING CYCLES CORE _ FISSION 5. REMOTE DECLADDING 8. ECONOMIC CONSIDERATIONS PRODUCTS 6. REMOTE INSTRUMENTATION 9. METALS FABRICATION COOLING _ PROCESING 7. CRITICALITY & 10. CORROSION REACTOR INFINITELY SAFE 11. MULTIPLE METALLURGIES GEOMETRIES ) -RECOVERED FISSILE 8. BIOLOGICAL SHIELDS MATERIAL 9. REMOTE MAINTENANCE VS. DIRECT MAINTENANCE RECYCLE FUEL I 10. FISSION PRODUCT POISONS 11. FISSION PRODUCT UTILIZATION RADIOACTIVE PROCESS OFF GAS FISSILE MATERIAL CORE REFABRICATION PURCHASED FERTILE MATERIAL BLANKET REFABRICATION FISSILE MATERIAL FOR SALE POSSIBLE PROCESSES: 1. AQUEOUS CHEMICAL TECHNOLOGY (ORNL) 2. VOLATILITY PROCESSING (ANL ) 3. PYROMETALLURGICAL PROCESS (NAA & ANL) 4. FUSED SALT (BNL ) Figure 9. Remotely Operated Reprocessing Systems Impact of Nuclear Technology.

-35 -reprocessing systems and unique chemical and metallurgical processes are combined with nuclear considerations. A typical fast reactor system is comprised of a highly enriched core surrounded by a depleted blanket. Such a fast reactor system requires rapid recycle with minimum inventory of fissile materials external to the reactor. Thus, the processing engineer is confronted with the recovery of fissile and fertile material with minimum cooling and decay time, introducing special engineering problems. The objective is to recycle and return the fissile materials from the reactor core with optimum removal of fission products and to combine such core fissile material with that portion of the fissile materials produced in the reactor blanket to sustain power reactor operations. The conventional process considerations cover the range from chemical thermodynamics to the technical and economic feasibility evaluations of selecting a particular process suitable for a given type or types of reactor. In order to select such optimum systems, it becomes necessary to couple with such conventional process considerations detailed and complete evaluations of reactor burnup cycles, radioactive decay and fuel cooling, special isotopic buildups resulting from neutron capture (such as protoactinium in the thorium series and neptunium in the uranium series), a high degree of accountability of fissile atoms, possible methods for remote decladding, remote instrumentation, and unusual precautions for determining geometries in which critical configurations are not possible until the materials are

returned to the reactor. In addition, the design criteria must be established to give consideration to health and safety, in-process inventory control, optimization of equipment designs in terms of normal process variables, coupled with nuclear variables, and the processing concepts for the separation and disposal of radioactive fission products. Again, we see that it is not possible to achieve a practical and workable system or to make engineering applications of technical data for reprocessing reactor fuels unless the background knowledge, experience and qualifications of the engineers are extended to include the nuclear parameters. CONCLUSIONS The achievement of a national and probably a world-wide energy and power economy will depend largely upon the abilities of scientists and engineers to convert data, information, conceptual engineering and operational principles of numerous individual processing systems integrated into an overall energy production and conversion system whose technical and economic feasibilities depend upon extensions of knowledge. Such data, concepts and demonstration programs must be reduced to a production technology which is compatible with our social, economic and political changes. Such reduction to production technologies can be achieved only through coupling science with engineering in all phases of developments. Achievement of this kind cannot be attained by our producing only highly educated and trained scientists, mathematicians and engineers whose breadth of knowledge is limited to only narrow fragments of specialization in one area of knowledge. Such high degrees of

-37 -specialization must be knit together into overall systems concepts. Hence, in addition to the highly specialized scientist and engineer on one hand, and the general engineering practitioner on the other, we have a need to develop, educate, and train technical men whose backgrounds, knowledge and experience cross the spectrum of the disciplines of nuclear science and engineering, economics, social and health problems. Such a man might be termed the "nuclear process engineer."

-38 -REFERENCES 1. Benedict, Manson and Pigford, Thomas, Nuclear Chemical Engineering, McGraw-Hill, 1957. 2. Bonilla, Charles, Nuclear Engineering, McGraw-Hill, 1957. 3. Glasstone, Samuel and Edlund, Milton C., Elements of Nuclear Reactor Theory, D. VanNostrand, 1952. 4. Holmes, D. K. and Meghreblian, I. V., "Notes on Reactor Analysis - Part II," August, 1955, CS-54-7-88, Technical Information Service. 5. Farbman, G. H., "Developments in Commercial Atomic Powerplants," Preprint 127, 1958 Nuclear Congress. 6 Flinn, S.. and Petric, M., "Performance and Potential of Natural Circulation Boiling Reactors," Preprint 98, American Society of Mechanical Engineers. 7. Jealous, A. C. and Klotzbach, R. J., "Reprocessing Costs for Fuels from a Single Region Aqueous Homogeneous Reactor," AIChE Preprint 66, 1958 Nuclear Congress. 8. Perry, J. H., Editor, Perry's Chemical Engineering Handbook, McGraw-Hill, 1950.

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