sign in sign up
<<
Home , Nuclear power, Nuclear reaction

Proc. Nat. Acad. Sci. USA Vol. 68, No. 8, pp. 1923-1930, August 1971

Electric from

MANSON BENEDICT Department of , Massachusetts Institute of , Cambridge, . 02139 Contributed to Symposium on for the Future, April 26, 1971

An abundant supply of electric energy generated at low cost United States through the joint efforts of industry and with minimal adverse environmental effects is essential to government, and their use throughout the world today has civilized society. Generation of by nuclear fission reduced the cost of electricity and paid important dividends is capable of meeting all three of these requirements: abundant in enhanced U.S. prestige and favorable foreign trade. supply, low cost, and minimal environmental effect. My purpose is to describe the types of nuclear reactors used The pressurized reactor for electric generation in the United States today; the advan- The principle of the pressurized-water is tages, deficiencies, and problems of today's reactors; and the illustrated in Fig. 1. rods for this reactor consist of steps that need to be taken to realize the full potential of dioxide, enriched to about 3% in 2"5U, hermetically nuclear fission as a source of electricity. sealed in tubes of a zirconium alloy. This zirconium tubing Limited time does not permit description of all reactor constitutes the first barrier against escape of the highly types under development. Attention is focused on light- radioactive fission products that form in the fuel as the end water and fast-breeder reactors, the principal types in use or product of the . Assemblies of these zir- under development today in the United States. Heavy-water conium-clad fuel rods are mounted in a heavy-walled steel reactors and molten-salt reactors, which may also play a role pressure vessel and are surrounded by flowing water entering in the future, are not dealt with. at a temperature of around 540'F and leaving around 600'F, The type of used throughout the world held at a pressure of around 2250 psi to prevent boiling. The today for generation obtains most of its energy water slows down produced in fission and increases from slow- fission of the scarce of uranium, their probability of reacting with 236U to such an extent that 285U, which occurs in only to the extent of the uranium fuel constitutes a critical mass capable of sus- 1 part in 140. To obtain the full potential of nuclear energy it taining a nuclear-fission . To hold the chain will be necessary to develop effective means for utilizing the reaction at a steady rate, a variable amount of neutron- abundant isotope, 238U, which makes up the remaining absorbing is used in the reactor, partly as movable con- 99.3% of natural uranium. The most promising type of trol rods and partly as boric acid dissolved in the water. reactor for this purpose is the fast-, in which Pressurized water is pumped through the reactor by the 288U is converted to , which then undergoes fission circulating pump, past the gas-cushioned pressurizer which with fast neutrons. holds the pressure constant, and through the generator. The breeder reactor will provide the world with electric There is transferred from the primary pressurized water energy for thousands of years, far beyond the capability of at 600'F and 2250 psi to secondary water boiling at a lower all fossil -, oil, and gas-now known or likely to be pressure of around 720 psi to make steam at around 506'F. discovered. Already, nonbreeding reactors in operation in The steam flows through a turbine driving an electric many parts of the United States and elsewhere in the world are generator and then passes to the condenser where it is con- generating electricity at a cost as low as the cost of electricity densed at subatmospheric pressure. The condensate is re- from fossil fuels in the same place. Breeder reactors, under turned to the steam generator by the condensate pump. development in many countries, are likely to generate elec- In the condenser, heat from the condensing steam is trans- tricity at an equally low cost. ferred through cooling coils to cooling water at a pressure above atmospheric, which leaves the condenser at a tempera- LIGHT-WATER REACTORS ture typically 20'F warmer than the incoming water. In some Turning first to today's power reactors, the slow-neutron, , this cooling water is drawn from the ocean or other nonbreeding, 2"5U-consuming kind, the reactors used pre- natural sources; in others, it is recirculated through cooling dominantly in the United States are of the light-water type. towers. Disposal of the heat contained in this warm water In these reactors ordinary water, under pressure and at without adverse effect on the environment is one of the temperatures up to 600'F, is used both as coolant to problems of all steam-electric plants, nuclear as well as the heat released in fission and as moderator to slow down the fossil. In light-water nuclear plants, however, about 50% fast neutrons initially produced in fission. There are two more warm water must be handled than in an efficient fossil- principal types of light-water reactor: the pressurized water fuel plant, because the thermal efficiency of the water-cooled reactor, used in around 60% of the light-water reactor installa- nuclear plant is only 32.5% due to its relatively low steam tions, and the boiling-water reactor, used in about 40%. temperature of 506'F, compared to a fossil-fueled plant with Both of these reactor types were developed initially in the a thermal efficiency over 40% obtainable from steam tempera- 1923 Downloaded by guest on September 23, 2021 1924 N. A. S. Symposium: Energy for the Future Proc. Nat. Acad. Sci. USA 68 (1971)

CONTAINMENT PRESSURIZER 2250 POUNDS/SQ. IN SHELL 6000F STEAM *~ ~~.' ~ ~~~~-n ~o ki lKinc, ,Cn Mt REACTOR 7aFUUNUS/bU IN PRESSURE VESSEL 5060F TURBINE _ GEN _ t STEAM WATER SUBATMOS. COOLING WATER PRESSURE ,TO OCEAN 30 POUNDS/SO IN FUEL -- CONDENSER RODS 4O ..FRO OCEAN POU/SU s N

CONDENSED WATER SUBATMOS PRESSURE

FIo. 1. Schematic diagram of pressurized-water . ture around 1000°F. The environmental impact of warm When the reactor is shut down for refueling and the pressure water from a nuclear plant can be dealt with satisfactorily vessel is opened, precautions as stringent as deemed necessary either by siting on a natural body of water with adequate can be taken to concentrate, package, and confine radioactive heat-absorption capacity, such as the ocean or a large river, materials present in the water or pressurized gases. or by use of cooling towers. The cost of heat disposal from a I have dwelt this long on the many barriers against escape water-cooled nuclear plant is, however, somewhat higher than of radioactivity because it is important to realize that, al- from a fossil-fueled plant. though nuclear power plants contain enormous amounts of A more significant potential environmental aspect of a radioactivity release of radioactivity to the environment, from nuclear power plant is the enormous amount of radioactivity them can be controlled to any degree desired, but with in- contained in it. Water-cooled nuclear power reactors are pro- creasing cost. All U. S. nuclear power plants are monitored by vided with many barriers against escape of radioactivity, the U. S. Public Health Service, and have been found to add which have kept releases to insignificant levels, and can be to the environment only a minute fraction of the amount of provided with even more elaborate safeguards if these should radioactivity naturally present (1). be required. As an illustration, precautions taken to minimize radioactive releases from a pressurized water reactor will be The boiling-water reactor described. The boiling-water reactor differs from the pressurized-water Most of the radioactivity is in the form of fission products reactor mainly in that the primary water in the reactor is held contained in the fuel. Some of the fission at a lower pressure, around 1000 psi, and is allowed to boil in products are refractory oxides, insoluble in water. Others, the reactor. Steam and water flowing past the fuel are sepa- however, are volatile or water-soluble, and a small fraction of rated, with the water being recirculated and the steam them appear in the primary water whenever zirconium tubes flowing directly to the turbine, after which it is condensed and leak, as they sometimes do. The primary water also carries returned to the reactor. The boiling-water reactor needs no corrosion products made radioactive by . separate steam generator, as the reactor itself performs this The radioactive content of the primary water is kept low by function. A boiling-water power plant has about the same continuous purification by filtration and ion exchange. thermal efficiency as a pressurized water plant. Escape of radioactivity from the primary water is prevented by the leak-tight pressure vessel and piping system within Comparison of nuclear power plants which this water circulates. with fossil-fueled plants Even if the primary water system should unexpectedly At present, 17 light-water nuclear power plants, with a total leak, there are further barriers against escape of radioactivity. generating capacity of 7,000,000 kW, are in operation in the The primary system is completely housed within a steel-and- United States and 108 plants, with a total capacity of close concrete containment shell. This shell is tested periodically to 90,000,000 kW, are operating, under construction, or for leak tightness and will prevent escape of serious amounts planned. The total capacity of such plants in operation by of radioactivity, even if a large fraction of the fission products 1980 is expected to be 145,000,000 kW. What are the reasons were to get out of the zirconium tubes and then out of the that lead to the widespread adoption of light-water reactors reactor. Any radioactivity leaking through the steam gen- in competition with conventional plants? erator from the high-pressure primary side to the lower- The first group of reasons relate to the favorable environ- pressure secondary side is prevented from further escape by mental aspects of nuclear power plants. The traffic of fuel the leak tightness of the secondary system. Even if the con- into a nuclear plant and waste products out is negligible com- denser leaked, no radioactivity could inadvertently get into pared with a fossil-fueled plant. Whereas a 1000-MW fossil- the cooling water and into the environment, because the fueled plant consumes over 2,000,000 tons of fuel per year, cooling water is at higher pressure than the steam being con- a nuclear plant of the same size needs only around 35 tons of densed. uranium dioxide. In contrast to the constant traffic of coal into Downloaded by guest on September 23, 2021 Proc. Nat. Acad. Sci. USA 68 (1971) Benedict: Nuclear Fission 1925

~'A a o .~A

>F- 2N FIG. 2. Yankee Nuclear Power Plant.

and ashes out of a coal-fired plant, a nuclear plant needs only Another aspect of nuclear power that has favored its one shipment of fuel in and (spent) fuel out per year. Whereas adoption is its relative invulnerability to interruptions in a coal-fired plant needs a large, unsightly reserve coal pile, fuel supply, because a year's supply of fuel is stored right in with noisy coal-handling machinery, a nuclear plant requires the reactor. Uranium will be plentiful for at least 20 years, only about one-third as much and is quiet. A fossil- whereas in some places low-cost fossil fuels are already in fueled plant discharges an enormous amount of effluent into short supply. The low cost of transporting uranium permits the atmosphere; a 1000-MW coal-burning plant emits around a nuclear plant to obtain its fuel economically from great 10,000,000 tons of per year and several hundred distances, whereas a fossil-fueled plant is limited to sources thousand tons of sulfur dioxide, nitrogen oxides, and ash from which transportation costs are low. The cost of electricity , whereas a nuclear plant emits practically none. in a nuclear plant has been less affected by fuel prices than in Because a nuclear plant requires no combustion air, it can be a plant burning , both because the cost of fuel is built partially or wholly underground if desired, and can be a smaller fraction of the cost of electricity, and because the designed to be less obtrusive esthetically than a fossil-fueled price of uranium has been stable, while the price of fossil fuels plant. Fig. 2 shows the attractive appearance of the 600-MW has nearly doublei in the past few years. Connecticut Yankee power plant. In an evaluation of the But all these advantages of nuclear power would not have environmental impact of fossil-fired, hydro, and nuclear power been effective were it not for the fact that in many parts of the plants, a writer in the October 1970 newsletter (2) of the New United States and elsewhere, electricity can be generated by England chapter of the Sierra Club, an organization not light-water nuclear power plants at as low a cost as by other noticeably biased in favor of nuclear energy, concluded that means. This is especially true where the cost of fossil fuel is the choice was "overwhelmingly in favor of nuclear power". high because it is not produced nearby, as in most of the Another factor that has led to widespread adoption of United States except near low-cost coal mines or light-water nuclear power plants has been their excellent fields. Absolute values for the cost of electricity from different safety record. Despite their large inventory of radioactivity, kinds of plants at different times and different places are hard there have been no serious accidents and no overexposure of to interpret because of the rapid increases occurring in con- the general public in over 100 reactor-years of operation of struction costs and the effect of local climatic and environ- commercial light-water reactors. Furthermore, another 780 mental conditions on costs. One example of a comparison reactor-years of operation without a reactor accident have between the cost of electricity from a pressurized-water been recorded by pressurized water reactors in the U.S. Navy. reactor plant and a plant burning coal will illustrate how Downloaded by guest on September 23, 2021 1926 N. A. S. Symposium: Energy for the Future Proc. Nat. Acad. Sci. USA 68 (1971)

TABLE 1. Comparison of cost of electricity from coal and TABLE 2. U. S. uranium requirements and pressurized water reactor units to be operational in (Two 940,000-kW generating Actual Projected 1974-75 near Fredericksburg, Va.) (1970) 1980 2000 Coal generating capacity Million kW Unit investment cost of plant, Total 300 523 1550 $/kW, C 202* 255 Nuclear 6 145 735 Annual capital charge rate, Total tons uranium per year, i 0.13 0.13 concentrates consumed 200,000 1,600,000 Kilowatt-hours generated per year per kilowatt capacity, k 5256t 5256t Increase in cost Heat rate, million Btu/kW- hr, h 0.009 0.0104 Price of Tons of of electricity Cost of heat from fuel, cents/ uranium uranium resources from water-cooled million Btu, f 45 18 concentrates at this or nuclear power Cost of electricity, mills/kW-hr $/lb U308 lower price (5) plants (mills/kw -h) Plant investment, 1000 X Ci/k 5.00 6.31 Operation and maintenance 0.30 0.38 8 594,000 0.0 Fuel, 10 X hf 4.05 1.87 10 940,000 0.1 Total 9.35 8.56 15 1,450,000 0.4 Breakeven cost of heat from coal, 30 2,240,000 1.3 cents per million Btu 36.2 50 10,000,000 2.5 100 25,000,000 5.5 * With no allowance for sulfur dioxide removal. t In actual system, coal plant would generate less electricity than nuclear. and plutonium are recovered, and the radioactive fission prod- ucts are concentrated and stored in solution for around 5 years nuclear power has been able to compete economically with in double-walled containers. At the end of this time, present electricity from coal. Before deciding to build two 940,000-kW AEC regulations require that the solutions be evaporated to pressurized-water nuclear power units for operation in 1974-75 dryness and that the solid fission products be sealed in steel near Fredericksburg, Virginia, the Virginia Electric and Power containers. Finally, these containers are to be shipped to a Co. (3) compared the cost of building either the nuclear national repository to be located in a salt plant or a coal-fired plant of the same size, and estimated the mine in Central Kansas for storage 1500 ft (457.2 m) under- cost of heat from and coal. They estimated that ground. This location is chosen because geologic evidence the unit cost of the nuclear plant would be $255/kW, for the indicates that the radioactive wastes will remain out of coal plant, $202/kW. More than offsetting this capital-cost contact with ground for far more than the 1000-year disadvantage of the nuclear plant is its lower fuel cost, 18 period in which they must be safeguarded before their radio- cents/million Btu compared with 45 cents/million Btu activity will decay to a harmless level. The technology for estimated for coal at that place and time. Table 1 summarizes shipping and reprocessing radioactive fuel has been developed a calculation of the cost of electricity for both types of plant, and proved safe by a number of years of operation, although resulting in 8.56 mills/kW h for the nuclear plant and 9.35 additional measures for retention of the long-lived gaseous for the coal-fired plant. For the coal-fired plant to be com- radioactive species and krypton-85 released in re- petitive with the nuclear plant, coal would have to be avail- processing will be required when the of fuel is greater able at the plant at a breakeven price of 36.2 cents/million than now. Btu. In view of the rapid rise of coal prices, this is not likely to The proposed storage of radioactive wastes in salt deposits occur. was examined by a committee of this Academy, which re- The economic advantages of nuclear power are even greater ported (4) in November 1970 that: "The use of bedded salt in places like Chicago, where local restrictions on burning for the disposal of radioactive wastes is satisfactory. In high-sulfur coal have required importation of low-sulfur coal addition, it is the safest choice now available, provided the from Wyoming and Montana at costs of 50 cents/million Btu wastes are in an appropriate form and the salt beds meet or higher. the necessary design and geological criteria. The site near Lyons, Kansas, selected by the AEC, is satisfactory, subject Radioactive wastes to development of certain additional confirmatory data and This discussion of light-water reactors would not be complete evaluation". Despite this favorable report, the widespread without mentioning their problems and disadvantages. One concern about this proposal that has recently arisen and the problem which light-water reactors share with all other unprecedented responsibility involved in safeguarding highly fission reactors is safe, long-term storage of their highly toxic material for 1000 years dictate thorough test and careful, radioactive fission products. In this brief talk I can only gradual exploitation of this proposed storage method. outline the problem and the presently favored solution. Spent fuel assemblies removed from the reactor are sealed in shielded Uranium consumption of light-water reactors containers, specially designed to withstand shipping accidents. Particular disadvantages of light-water reactors include their Fuel assemblies are transported to a reprocessing plant where low thermal efficiency, already mentioned, and much more they are cut open, their contents are dissolved in acid, uranium significant, the fact that they utilize effectively only the Downloaded by guest on September 23, 2021 Proc. Nat. Acad. Sci. USA 68 (1971) Benedict: Nuclear Fission 1927

scarce isotope 235U. The incomplete use of natural uranium TABLE 3. Comparison of uranium requirements of water-cooled will be a very serious disadvantage unless much greater reactors and fast-breeder reactors amounts of uranium are discovered than have now been found. Table 2 gives the cumulative consumption of uranium Water- Fast ore concentrates by light-water reactors in the United States cooled breeder if this type were used to generate the 145,000,000 kW of Principal raw material 235U 2U nuclear power expected by 1980 and the 735,000,000 kW Uranium concentrate consumption, expected by 2000. The 200,000 tons of uranium concentrates tons per million kilowatt years 171 1.3 consumed by 1980 and the 1,600,000 tons consumed by 2000 Increase in cost of electricity are to be compared with the total resources of uranium in caused by increase in price of known deposits and expected to be found in extensions of uranium, mills/kW.h/$/lb 0.06 0.0 them as a function of uranium price. Unless more uranium is found, the 1,600,000 tons which would be consumed in light- Increase in cost Million kilowatt-years water reactors by the year 2000 would raise the price of of electricity of electricity which Ura- U.S. h could be in uranium from the present value of less than $8/lb to over $15. nium uranium mills/kW- generated Since the cost of electricity from light-water reactors increases price, resources Water Fast Water Fast by about 0.06 mill/kW. h per dollar per pound increase in the ($/lb) (tons) reactor breeder reactors breeders price of uranium, this would add more than 0.4 h mill/kW- 8 594,000 0.0 0.0 3,470 460,000 to the cost of electricity. Even more serious, of course, would 10 940,000 0.1 0.0 5,500 720,000 be the complete exhaustion of all of our presently estimated 15 1,450,000 0.4 0.0 8,480 1,120,000 resources of low-cost uranium in less than 30 years. 30 2,240,000 1.3 0.0 13,100 1,720,000 50 10,000,000 2.5 0.0 58,300 7,700,000 FAST-BREEDER REACTORS 100 25, 000,000 5.5 0.0 146,000 19,200, 000 This wasteful consumption of low-cost uranium by light- water reactors can be arrested if fast-breeder reactors now water reactors. At the present rate of being developed in many countries prove to be reliable and in the United States, 300,000,000 kW, fast-breeder reactors economic. The fast-breeder reactor is fueled with a mixture of fueled with U. S. uranium resources available at $100/lb plutonium and abundant 238U. In this reactor, a coolant which could provide all our electricity for 64,000 years. It is this does not slow neutrons down is substituted for water; the two tremendous extension of our fuel resources that makes de- principal candidate coolants are under pressure or velopment of the breeder reactor so challenging and important. liquid sodium near 1 atm. Fission of a plutonium by a Where does development of the fast breeder stand today? fast neutron produces about 2.5 neutrons for every neutron Its ability to compete economically with the light-water consumed. One of these neutrons continues the fission chain reactor is not yet proved, but the fact that it would consume reaction and the remaining 1.5 are absorbed by 233U to produce so much less natural uranium is a favorable factor that 1.5 of new plutonium. One of these replaces the plu- should make the fuel cycle cost of the fast breeder around 1 tonium consumed in fission, leaving a net gain of around half mill/kW-hr lower than the fuel cycle cost of the light-water an atom of plutonium for every 1.5 atoms of 238U consumed. reactor. With this fuel cost advantage, the unit capital cost In this way, all the abundant 238U in natural uranium can be of a fast breeder could be as much as $50/kW higher than a used as fuel, which would multiply our nuclear fuel resources light-water reactor without the breeder losing its economic more than a 100-fold. advantage. Reactor development authorities in this country But this is only part of the improvement in our nuclear [6] and abroad believe that a fast breeder need not cost this fuel resources made possible by the breeder. Because a fast- much more than a light-water reactor. I share this hopeful breeder reactor consumes so little natural uranium, the cost view. of electricity from it would be practically independent of the The two types of breeder reactor that have the best chance price of uranium. Consequently, if the fast-breeder reactor of meeting this cost requirement and being proved tech- proves to be economic at today's uranium price of $8/lb, it nically sound are the liquid-metal cooled fast-breeder reactor still could be fueled economically with uranium costing $50 (LMFBR) and the gas-cooled fast-breeder reactor (GCFR). or $100/lb. At $100/lb, U.S. uranium resources are estimated Each type would use a mixture of plutonium oxide and to be 25,000,000 tons, compared with less than 1,500,000 natural uranium oxide as fuel, would have a thermal effi- at $15/lb. Thus, by being able to use this high-cost uranium, ciency close to 40%, and would be capable of producing the breeder reactor would extend nuclear fuel resources by close to 1.5 g of new plutonium for every gram of plutonium another factor of over 15. Table 3 compares the amount of consumed. This high breeding ratio gives these reactor types electricity that could be generated by breeders and light- a tremendous advantage over other types of breeders. water reactors from the amount of uranium available at dif- Except for their similar fuel and breeding potential, the ferent prices, and shows the increase in cost of electricity liquid-metal and gas-cooled breeders have little in common, caused by progressively higher uranium prices. Light-water technically or historically. The liquid-metal breeder uses reactors could generate 8,480,000,000 kW years of electricity molten sodium at low pressure as coolant, whereas the gas- from all the uranium available at $15/lb, about the highest cooled breeder uses helium at 50-75 atm. uranium price at which this type can compete with fossil fuel at today's prices. Fast breeders, on the other hand, could Gas-cooled fast breeder generate 19.2 million million kW years of electricity from The gas-cooled fast breeder can draw on the helium-cooled uranium at $100/lb, more than 2000 times as much as light- reactor technology already developed for the High-Tempera- Downloaded by guest on September 23, 2021 1928 N. A. S. Symposium: Energy for the Future Proc. Nat. Acad. Sci. USA 68 (1971)

PRESTRESSED CONCRETE PRESSURE VESSEL

FIG. 3. Gas-cooled fast reactor. ture Gas-Cooled Reactor (HTGR). One 45-MW example of the fuel and is heated to 1200'F. The helium then flows this slow-neutron, nonbreeding, helium-cooled reactor is now through the steam generator, producing steam at 1050'F. in operation in the United States, and a second 330-MW unit Fuel, helium circulator, and steam generator are all contained is being built. Fig. 3 illustrates schematically the principle of within a prestressed concrete pressure vessel, as in the HTGR. the gas-cooled fast breeder. The prestressed-concrete pressure Because of the high temperature at which steam is produced, vessel, helium circulator, and helium-heated steam generator the thermal efficiency of this gas-cooled fast-breeder system developed for the High-Temperature Gas-Cooled Reactor would be around 40%, much better than water-cooled reactor could be used without major change for this type of fast systems and as high as a modern fossil-fueled plant or the reactor. liquid-metal fast-breeder system. Fuel for the gas-cooled fast-breeder reactor consists of a The major drawbacks of the gas-cooled fast-reactor stem mixture of,15% plutonium dioxide and 85% [28U]uranium from the relatively poor heat-removal characteristics of dioxide clad in stainless steel; fuel would be generally similar helium gas, compared with liquid sodium. The most serious of to fuel developed for the liquid metal fast-breeder reactor. these is the difficulty of preventing overheating of fuel in the Helium gas at 1250 psi is pumped by a helium circulator over event of loss of helium pressure. Engineering studies of INTERMEDIATE 11500F / 1100 PRIMARY / SECON

FUEL U02 + Pu02

REACTOR

PRIMARY SECONDARY FEED WATER SODIUM PUMP SODIUM PUMP PUMP FIG. 4. Liquid-metal fast-breeder reactor. Downloaded by guest on September 23, 2021 Proc. Nat. Acad. Sci. USA 68 (1971) Benedict: Nuclear Fission 1929

solutions to this and other problems of the GCFR are being TABLE 4. Liquid-metal fast-breeder power plants conducted in this country, and in Europe, and solutions are likely to be found, but there are as yet no firm plans for Electric Years building a reactor of this type. It is, nevertheless, an attractive Country Reactor megawatts operated concept because it promises high breeding ratio, high ther- U.S. EBR-I 0.3 1951-63 mal efficiency, low capital cost, and freedom from the prob- U.K. 60 1963- lems of handling sodium that complicate the liquid-metal U.S. EBR-II 20 1965- breeder. The gas-cooled fast breeder should receive sub- U.S. Fermi 70 1965- stantially increased development funding because of the Rapsodie 20 1967- advantages it would have over the liquid-metal breeder if U.S.S.R. BR-60 60 1970- emergency cooling of GCFR fuel could be proved reliable. Under construction Scheduled to operate U.S.S.R. BR-350 150 1971- Liquid-metal fast breeder U.K. PFR 250 1972- Despite the difficulties of working with sodium, its use as a France Phenix 250 1973 coolant for fast reactors has appealed to reactor engineers U.S.S.R. BN-600 600 1973-1975 since 1950 and a number of sodium-cooled fast reactors have already been built. Sodium has excellent heat-removal characteristics-very high thermal conductivity and high to authorize construction of a 300-MW fast-breeder power volumetric -so that overheating of the fuel plant and Japan and Italy are making rapid progress. during normal operation or in emergencies can be practically In the United States, the policy of the AEC has been to guaranteed not to occur. By designing the reactor as a double- build facilities for testing the novel components of a liquid- walled vessel with no openings below the top of the fuel, metal fast-breeder reactor before constructing large demon- assurance is provided that the fuel will remain submerged in stration power plants. Three industrial companies have built and cooled by liquid sodium even in the event of mechanical these testing facilities: General Electric has participated in failure of the cooling system external to the reactor. Because the SEFOR project, which is testing the dynamic and safety of sodium's high boiling point and compatibility with stainless characteristics of a small LMFBR; North American Rock- steel, sodium can be heated to 11500 F in the reactor and can well has built facilities for engineering test of sodium com- be used to generate steam at high temperatures and pressures ponents; and Westinghouse is building the Fast Test Reactor similar to those used in conventional power plants, yielding a to test fuel, scheduled to start operation in 1974. Each of thermal efficiency of over 40%. these firms has submitted to the AEC a proposal to build a But sodium has numerous drawbacks. It is opaque, so demonstration LMFBR power plant in the 300 to 500-MW that refueling and other operations in the reactor have to be range, each of which would cost around $500,000,000. carried out blind. It is made intensely radioactive in the A number of difficult decisions must now be made. Among reactor, so that it is considered prudent to interpose a secon- the questions to be answered are these: Shall one, two, or dary, nonradioactive, sodium coolant loop between the three demonstration plants be built? If more than one, in primary-reactor sodium and the steam generator, as shown in which order? If less than three, how can all three companies Fig. 4. Sodium reacts with air or water, so that it is necessary be kept in the development to provide competitive sources of to provide argon cover gas for free sodium surfaces and to supply for commercial plants? On what time scale shall design the steam generator so that leakage of water into demonstration plants be built? How shall the large sums sodium is prevented. If local boiling of sodium should occur needed for their construction be apportioned among the in the reactor, the rate of fission might increase to an un- government, the three interested companies, and the many acceptable degree unless adequate precautions are taken in electric power companies of the United States? the design and operation of the reactor. Finally, a commercial While these questions are being debated in the United liquid-metal breeder reactor requires the development of States by many government and commercial interests, pumps, valves, and heat exchangers for handling sodium foreign projects have been moving faster. In Russia, England, in unprecedently large volumes. and France, government agencies have had full responsibility These difficulties with sodium have been largely overcome. for breeder projects and have driven ahead with construction The development of liquid-metal fast-breeder reactors is far of demonstration plants without waiting for the exhaustive advanced, and a number of power plants of this type have testing of components now characteristic of the U.S. program been built. Table 4 shows the principal liquid-metal fast- and without trying to establish several competing sources breeder power plants that have been built or are under of supply. Unless these foreign projects run into major diffi- construction. culties, liquid-metal fast-breeder reactors will become commer- In the United States, as long ago as 1951, the Experimental cially available abroad many years earlier than in the United Breeder Reactor I demonstrated a breeding ratio greater than States. There is a definite possibility that in the 1980s U.S. unity and was the world's first reactor to generate electricity. power companies will be buying breeder reactors from France, Later, the larger Experimental Breeder Reactor II and the England, or Germany instead of from Schenectady, Pitts- Reactor have come into operation. Although burgh, or Los Angeles. Many U.S. reactor engineers, in- other countries entered the breeder field later than the United cluding myself, believe that the technology of the liquid- States, Russia, England, and France have run reactors com- metal fast-breeder reactor is sufficiently advanced to justify parable to our Experimental Breeder Reactors and are now starting construction of at least one demonstration plant building demonstration breeder power plants larger than here and now before we lose the momentum of our present any now authorized in the United States. Germany is about fast-reactor program. Downloaded by guest on September 23, 2021 1930 N. A. S. Symposium: Energy for the Future Proc. Nat. Acad. Sci. USA 68 (1971) We cannot wait to start construction of these demonstra- Second, I would like to urge maintenance of a sensible tion plants until the eventual shortage of uranium is upon us. attitude toward the low levels of radioactivity emitted by It will take at least 7 years to bring the first demonstration these power plants. While it is proper to recommend that plant into operation, and another 7 years to build the first these levels be kept as low as practicable, we should bear in full-scale commercial plants. Construction of the first demon- mind that we are surrounded on all sides by natural . stration plants for light-water reactors started 15 years ago, We should therefore not require that extreme measures be and these reactors are only today reaching full commercial taken and excessive costs incurred to limit radiation exposure maturity. The development period for liquid-metal breeders from nuclear power plants to an unnecessarily small fraction is apt to be even longer. of natural levels. We urge Congress, the AEC, and the Office of Management Third, I would like to recommend prompt implementation Budget to agree on a national program and a timely schedule and thorough testing of the proposed long-term storage of for building these demonstration plants. We urge these high-level radioactive wastes in bedded salt formations. Until governmental groups, the interested manufacturers, and the this or an equivalent procedure has been proved by actual power companies to agree on an equitable plan for funding operation to be completely reliable, critics of nuclear power their construction. One mechanism proposed for obtaining will have a valid cause for concern. the necessary funds is a Federal tax on electricity to be Finally, we should move ahead aggressively with the remitted by the Federal government to groups building and development of breeder reactors, because today's slow operating the first fast-reactor demonstration plants, some- neutron, nonbreeding reactors provide only a short-term what as the Federal gasoline tax is remitted to the states for solution to our electric energy needs. One or more demon- highway construction. In this way the costs would be borne stration plants of the liquid-metal fast-breeder type should by the U.S. consumer of electricity, the ultimate beneficiary be built as soon as possible. All present indications are that of this abundant source of low-cost electricity for all time to the fast-breeder reactor is our best hope for providing electric come. energy in practically unlimited amounts for thousands of years. We cannot afford to allow other nations to pass the CONCLUSIONS United States as the leader in this vital development. Let me conclude by placing before you the points I consider most important in this brief summary of power from nuclear 1. See, for instance, Nuclear Power Reactors and the Population, fission. Public Health Service Report BRH/OCS 70-1, Jan. 1970, p. First, I would emphasize that properly designed and 14. operated light-water reactors have been proved to be eco- 2. "The Power Dilemma-Our Choices and the Environmental nomic, reliable, relatively unobtrusive, safe, and nonpolluting. Burden," New England Sierran, Oct. 1970. With these reactors we have a new energy source that can 3. Personal from Mr. Stanley Ragone, Virginia Electric and Power Co., April 22, 1971. serve as our principal means for generating electricity for the 4. Disposal of Solid Radioactive Wastes in Bedded Salt Deposits, remainder of this century. They are the best solution we have report by the Committee on Radioactive Waste Management, to the current energy crisis. Light-water reactors are eco- National Academy of -National Research Council, nomically competitive with fossil fuel for generating elec- Nov. 1970. use 5. Potential Nuclear Power Growth Patterns, U.S. tricity. Their for this purpose will conserve fossil fuel for Commission, Report WASH-1098, Dec. 1970. transport, home heating, chemical synthesis, and other more 6. See, for instance, Report of the EEI Reactor Assessment Panel, versatile applications for which uranium cannot be used. Edison Electric Institute, New York, 1970. Downloaded by guest on September 23, 2021