News Feature
Western Europe pushing ahead to develop fast breeder reactor For their part, policy makers and economic planners in West European governments genuinely believe that they have running out and with little little option but to push ahead with a uranium available, European program that will either prove or disprove the merits of fast breeder reactors in nations are evaluating helping meet their medium- to long-term energy requirements. Their reasoning is fuel-efficient FBR's sharpened by forecasts that point to a severe energy crunch developing at about the turn of the century. And they see in Dermot A. O'Sullivan fast breeders an essentially unlimited fuel C&EN, London source that, wisely employed, could make the difference between maintaining a Last July, several thousand demonstra- reasonably high standard of living in the tors descended on the little township of years ahead, or a sharp decline in ecoCreys-Malville in southeastern France. nomic activity with all the critical social They were there to protest the building of consequences such a development would a 1200-Mw fast breeder reactor power foster. station dubbed Superphénix. In the clash The nine countries that make up the with police that ensued, one reportedly European Communities—Belgium, died and many were.injured, some seri- Denmark, France, West Germany, Ireously. land, Italy, Luxembourg, the NetherThe incident was but one of a number lands, and the U.K.—are particularly of moves that environmentalist groups vulnerable in the energy arena. Taken as and concerned citizens in many West a whole, almost 60% of their primary enEuropean countries have been staging ergy needs now are being met by fuel imagainst the emergence of civil nuclear ports. Coal is about the only native energy energy policies in general and fast breeder source that occurs in any large amount, reactors in particular. Their stance par- but that commodity is becoming inallels that of like-minded people in the creasingly expensive to recover. The U.S. and elsewhere. Fears expressed range natural gas deposits in the Lacq region of across the spectrum of the possible con- southern France are running out, while sequences stemming from the arrival of those in the northern Netherlands are the nuclear age—unease about the safety dwindling. Recent discoveries of oil and aspects of nuclear reactors sited in heavily natural gas in the North Sea have come as populated areas, worry of radiation ef- a welcome boon. Their availability, howfects, and alarm at what is seen as the ever, based on current known reserve esgrowing likelihood of plutonium's falling timates, is expected to begin declining by into the hands of terrorist organizations about the mid-1990's. and irresponsible governments. Even the EC's current nuclear energy U.S. President Jimmy Carter has made program is critically dependent on imno secret about his opposition to the ported uranium. France is the only spread of nuclear reactors and repro- member country where uranium ore occessing facilities throughout the world. In curs to any significant extent. Reserves his view, the indiscriminate transfer of there, however, are sufficient to satisfy technology, hardware, and nuclear engi- only about 10% of the country's requireneering know-how greatly increases the ments. threat of proliferation of atomic weapons One of the tasks of the staff at the enand compounds the difficulties of inter- ergy directorate of the EC Commission in national policing programs. His thinking Brussels is to make continuing appraisals colors his own domestic policies in the of likely future energy demand patterns. area. Last April, he deferred indefinitely These take the form more of scenarios steps to undertake commercial repro- rather than of forecasts as such. In one cessing and recycling of plutonium arising scenario prepared last year, energy defrom U.S. nuclear power programs. And rived from nuclear fission is seen to grow in November, he vetoed a bill that would steadily from the current level of about 2% have included funding for the Clinch of the combined primary energy requireRiver breeder reactor demonstration ments for the nine member countries to plant in Tennessee. about 22% by the year 2000. The contri-
With fossil fuel sources
UKAEA '8 250-Mw prototype fast breeder reactor at Dounreay, Scotland, has been operating since 1975. Technicians, above, operate apparatus for handling 27-Inchdiameter flasks containing fuel Feb. 13, 1978 C&EN 41
How a fast breeder reactor can be used to generate electricity Reactor Primary sodium pump
Turbine
Heat exchanger
Intermediate heat exchanger
Generator
I Hot sodium duct
Reactor jacket
Steam
Condenser
Water
Pump Core
Primary vessel
Concrete shield
The fast breeder reactor (FBR) is so called because neutrons generated within the reactor core move at high speed without being slowed down by a moderator, and because plutonium is bred at the same time that it is consumed. The fuel is a mixture of uranium dioxide, made from the fertile uranium238 isotope, and plutonium dioxide clad in stainless steel. As plutonium is being burned up, neutrons arising from the fission process change the uranium-238 to plutonium-239. This occurs each time a neutron strikes a uranium-238 atom. The unstable uranium-239 isotope that results undergoes rapid conversion by two successive ^-emissions to plutonium-239. The arrangement of the fuel "pins" in the FBR core influences the rate of formation of new plutonium. According to the conditions chosen, either the amount of plutonium used may exceed that produced, the total quantity may remain in balance, or there may be a net plutonium increase. A reactor's doubling time is the time required to generate sufficient additional plutonium to fuel another similar reactor. The fuel charge in an FBR doesn't function indefinitely. After a certain residence time in the reactor it must be replaced with new fuel. The spent fuel removed is stored in heavily shielded depositories or reprocessed to recover the re-usable uranium and plutonium from the fission products. No reprocessing of spent FBR fuel currently is being undertaken. One characteristic of an FBR is that the core is extremely compact. The
42
C&ENFeb. 13, 1978
Cool sodium duct
small size stems from the need to keep neutron moderating materials in it to a minimum so that the neutron energies are maintained at a high level. In contrast to some commercial thermal reactors that have a core volume well in excess of 2000 eu m, the core of an FBR of comparable energy output is about 6 eu m. Coupled with the FBR's small core size is its extremely high power density. This calls for a very good heat transport system to remove heat from the core. Apart from continuing evaluation of possible gas-cooled systems, liquid metal is the coolant employed In the present generation of FBR's. Liquid sodium has emerged as the preferred coolant material. Its melting point (98° C) is well below the reactor's operating temperature, and its boiling point (883° C) is well above it. It also has a high heat capacity. Of the other metal coolants studied, only Jiquid lithium has better heat transport properties and lower pumping power characteristics. Lithium, however, has a higher melting point (180° C) than sodium. Moreover, it is some 60 times costlier. An alloy of sodium and potassium has been used in the 15-Mw(e) experimental fast reactor at Dounreay, Scotland. The alloy Involved (70 parts sodium and 30 parts potassium) has a lower melting point (40° C) than that of sodium itself. But it is about five times more costly, and it is more highly reactive than sodium with air and water. Although sodium reacts violently with water if it comes in contact with it, its use as a coolant hasn't presented any
major engineering problems. Stringent controls obviously are called for both in the materials of construction and in the overall design of the system. And continuous inspection and monitoring must be maintained on those parts of the circuit that form a barrier between sodium and water. As an additional safety feature, the FBR's currently under development in Western Europe employ a secondary liquid-sodium heat transport system. Sodium pumped around the reactor core removes heat generated by the nuclear fission reactions. This heat is transferred in an intermediate heat exchanger to the secondary sodium coolant circuit. It is this heat that is used to convert water to the steam needed to power the electricity-producing units. Such a design avoids the possibility of radioactive sodium in the primary cooling circuit coming into contact with water in the event of a failure in the piping. Proponents of FBR's point to several practical advantages, apart from the fuel-breeding characteristic, that they offer over conventional thermal reactors. One is that the coolant isn't pressurized. A potential hazard associated with thermal reactors, on the other hand, is the very high pressure that builds up in the gas or liquid coolant system. Also, unlike thermal reactors in which coolant must be kept in motion by pumps, even if the pumps of an FBR should fail, natural convection in the sodium would continue to maintain a high degree of heat removal from the reactor core, allowing time for an auxiliary cooling system to be brought into use.
bution of nuclear fission would continue to grow until, by 2030, it might peak at around 45% of the total primary energy requirement in that year. Thereafter, nuclear fission could decline in importance with growing development of alternate energy sources such as solar, wind, wave, and geothermal power, and with the emergence of thermonuclear fusion. EC energy strategists concur with many environmentalists that prudent conservation measures, coupled with development of solar power technology, will do much to help eke out the declining reserves of oil and natural gas. At the same time, they argue that even if the energy demand growth rate were to plateau around the year 2000, such a situation would not automatically solve the fuel supply problem. West European needs still would remain high. At the same time, growing international competition to gain access to the finite stocks of fossil fuels would continue to mount because of increasing energy demands in the developing countries. Last July, the EC Commission issued a position report titled "The Fast Breeder Option in the Community Context." Citing figures compiled jointly by the Organization for Economic Cooperation & Development's Nuclear Energy Agency and the International Atomic Energy Agency, the report notes that present estimates of global uranium resources costing $30 per lb or less total some 3.5 million metric tons. A mere 3.5% of this amount occurs within EC boundaries. "Without prejudging the possibility of further uranium discoveries, and of utilizing uranium resources extractable at costs greater than $30 per lb," the report states, "it can be assumed as a basis for planning that of the 3.5 million metric tons total uranium availability, the EC could only count on 1.2 million metric tons if it could get its proportional quota on the world market. "In the absence of fast breeder reactors, nuclear energy could neither be considered as an effective long-term energy option for the EC, nor mitigate the consequences of the EC's dependence upon imported uranium. Dependence of the EC on imported uranium supplies could adversely affect the realization of a substantial nuclear energy program, and even initiate its premature decline. This is a risk that the EC cannot afford to take." The problem with the present generation of thermal fission reactors is that these reactors are very uneconomical in their use of uranium fuel. The reason is that the fissionable uranium-235 isotope that forms the basis of their fuel constitutes less than 1% of naturally occurring uranium. Fast breeder reactors, on the other hand, have the ability of generating new plutonium from the preponderance of uranium-238 at the same time that the original charge of plutonium-239 fuel is being consumed. Fast breeders can extract at least 60 times more energy from natural or depleted uranium than their conventional thermal reactor counterparts. On this
Hill: a safe fast reactor program
basis, a ton of uranium would be equivalent to some 600,000 metric tons of oil equivalent in energy content potential. Put another way, FBR's could unlock about 3 billion metric tons of oil equivalent of energy from 5000 metric tons of uranium, an amount that matches the energy content associated with the estimated technically recoverable oil and gas reserves in the North Sea. As the EC Commission report points out, "The 1.2 million metric tons of uranium that could cumulatively be made available to the EC could yield, with the help of breeders, approximately 700 billion metric tons of oil equivalent of energy. This represents more than 800 years of energy supply at the present rate of primary energy consumption [in the EC]." With such enticing calculations, it is little wonder that energy strategists in Western Europe are enthusiastic about the role FBR's might play in their projected energy scenarios. But they emphasize that it will take at least 20 years to install FBR's in sufficient numbers to improve the overall uranium utilization significantly. In fact, the rate of installation of these reactors is constrained by the rate at which plutonium becomes available from thermal reactors and from FBR's themselves. The EC Commission report concludes that "a discontinuity in the execution of the fast breeder reactor, programs presently in progress and planned in the EC could result in the loss of effectiveness of the fast breeder reactor as an energy option for the early part of the next century. The EC would not only risk being unable to meet the whole of the energy demand during that period, but also could no longer count on nuclear energy to reduce its dependence on foreign-held scarce and expensive fuel supplies." Sir John Hill, chairman of the U.K. Atomic Energy Authority, notes that, "Europe, and Japan even worse, is not well endowed either with fossil fuels or with uranium.
"The U.S., on the other hand, is very fortunate in its raw materials. The discovered deposits of uranium there are something like 40% of the world reserves. In Europe there is very little. There is some in France, not much. There is quite a lot in Sweden in shales, but it's at very low concentration, about 300 grams per metric ton, and it will be both expensive and very damaging to the environment to get it out fast. "Looking into the future, the fast reactor really does seem the way that Europe and Japan want to go. And frankly, I think the same will apply in the U.S. as well. At the world energy conference in Istanbul in September, there was virtual unanimity that the world must go for the fast reactor because no one can see how to balance up supply and demand [of energy] in the next century without having substantial fast reactor programs. "No one anywhere is arguing for a large program of fast breeders now," Sir John continues. "What people [in the U.K.] are arguing for is that they should build a full-scale demonstration fast reactor power station so that we can get the bugs out of that, and so that in 10 or 12 years' time we will have a fully developed system on full industrial scale which can be replicated, modified, or copied if required. The Soviet Union sees things in exactly the same way as do Europe and Japan." The concept of the FBR isn't particularly new. As early as 1944, Dr. Enrico Fermi and Dr. Walter Zinn were considering the possibility of a controlled chain reaction without neutron moderation that would allow effective breeding of the fissile material. "Few people today remember that the first electricity produced from nuclear power was generated in a fast reactor," observes England's Lord Hinton, who played a key role in directing the U.K.'s early drive to develop FBR's. "By 1948, Walter Zinn at Argonne National Laboratory was working on the problems of the fast breeder reactor. It was his work that led to construction of the experimental breeder reactor at Idaho Falls, and it was there that electricity was first generated from nuclear energy." In Western Europe, the U.K. was the first to build and operate an experimental electricity-producing FBR. In a sparsely populated region of the Scottish coast, the U.K. Atomic Energy Authority installed the 15-Mw(e) Dounreay fast reactor. It went critical in 1959 and continued in operation until phased out last year. Encouraged by the functioning of this reactor, UKAEA next set about a 250-Mw prototype fast reactor. Since its startup in 1974, it has been feeding electricity into the Scottish grid. The aim ultimately is to erect a 1300-Mw commercial-scale fast reactor power plant, the CFR-1. The French and West Germans, too, have been putting an increasing amount of engineering effort into FBR design and development studies. Commissariat à l'Energie Atomique, the French atomic energy commission, completed a reactor test facility in 1967 at its Cadarache research center in southeastern France. Feb. 13, 1978 C&EN
43
Flowers: anxiety about the hazards
Called Rapsodie, a melodic-sounding contraction of rapide (fast) and sodium, the liquid-metal coolant employed, it now has a thermal output capacity of 40 Mw, double the original power level. Rapsodie doesn't generate electricity. It is used to evaluate the effects of prolonged irradiation on fuel assemblies in an FBR environment. Next came Phénix, named after the mythical bird that was reborn from its own ashes, a subtle reference to a fast reactor's ability to generate new fuel as the original plutonium charge is burned. Built at Marcoule in the Rhône valley, not far from Avignon, the Phénix reactor was completed in 1973. It has a power rating of250Mw. Based on the engineering experience gained with Rapsodie and Phénix, the French commission, together with Electricité de France (EdF) and Italy's Ente Nazionale per l'Energia Elettrica (ENEL)—the electric utility companies of the two countries—launched a collaborative venture to build Superphénix, a full-scale commercial FBR power plant. Participants since have been expanded to include West Germany's Rheinisch Westfâlisches Elektrizitâtswerke (RWE), a major electricity utility, Synatome of Belgium, Samenwerkende ElektriciteitProduktie Bedrijven (SEP) of the Netherlands, and the Central Electricity Generating Board of the U.K. Ground has been broken for Superphénix at CieysMalville, about 35 miles from Lyon. Scheduled for completion in 1982, it will have an output of 1200 Mw. It will be operated by NERSA (Centrale Nucléaire Européenne à Neutrons Rapides S.A.), a company owned 51% by EdF, 33% by ENEL, and 16% by Schnellbruter Kernkraftwerkgesellschaft (SBK), comprising the Belgian, British, Dutch, and West German interests. Meanwhile, at Karlsruhe, West Germany, a 200-Mw experimental fast breeder, KNK-2, was built in 1968 for fuel irradiation studies. SBK now is planning a 300-Mw prototype FBR power plant,
SNR-300, at Kalkar, a West German town on the Rhine near the border with the Netherlands. The intention is to install a commercial-scale 1200-Mw plant, SNR-2, more or less matching Superphénix. Like Superphénix, SNR-2 would come within the framework of the Europewide international collaborative program. The broadening of the research, development, and operating effort to embrace a large number of countries truly places the FBR development program in a Europewide context. A pact signed last July covers cooperation at four levels. In the area of R&D, the agreement "provides for complete exchange of information, harmonization of programs, and crossparticipation in joint projects." Too, it covers full exchange of building and operating experience of reactors. There will be "agreed cooperation on design studies, engineering, and construction of FBR power plants." In addition, "commercialization of information and know-how will be accomplished through licenses granted by a joint company, SERENA." Société Européenne pour la Promotion des Systèmes Réacteurs Rapides au Sodium (SERENA) is a newly formed fast reactor know-how holding company comprising Belgian, British, Dutch, French, West German, and Italian partners. One of the features of the new collaboration is that it spans all levels of nuclear engineering interests among the participants. These include government-owned fundamental research laboratories, commercial engineering concerns, and electrical utility companies. Considering the complexity of the engineering involved in FBR design, and their use of such a potentially hazardous material as liquid sodium for coolant, the reactors built and tested to date in Western Europe have been remarkably trouble-free. Some cases of operating problems have been encountered, of
Speedy commercialization of FBR's could cut EEC fossil fuel demand almost 90% within 40 years Millions of metric tons of oil equivalent
700 600 LWRon^r
500 400 300 LWft + F M 200
• • l i m n — u i * IMP 100
ο
1980
1990
oL·!-
L
2000
i
2010
-J
C&EN Feb. 13, 1978
2020
I
2030
2040
1
L
2050
I
2060
-J
2070
I
1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 Note: These scenarios assume that the annual rate of increase of primary energy demand in the European Economic Community will slow down and eventually plateau about the year 2040. Also assumed is that the maximum amount of uranium available to EEC is 1.2 million metric tons, about a third of estimated global resources recoverable at economical prices. Source: Commission of the European Communities
44
course, but these generally have been ascribed as the "teething problems" usually associated with the emergence of any new technology. For instance, two small secondary sodium leaks developed at the top of one of the intermediate heat exchangers of Phénix. French engineers emphasize that the fault did not directly involve the reactor itself, and they modified the design to avoid a similar problem's arising again. Indeed, a characteristic of the various FBR development programs is the considerable care that is being exercised to reduce the element of operating risk. As one scientist puts it, "We just cannot afford to make mistakes." The EC Commission's report on the FBR option addresses itself squarely to the question of risk. "For fast reactors to become acceptable," it notes, "their performance in terms of safety, radiological protection, and impact on the environment in normal and accidental conditions must be shown to be equivalent to that of established thermal reactors. It is one of the primary tasks of the fast reactor demonstration and safety programs now in hand in the various countries of the EC to progressively satisfy this condition." The Fast Reactor Coordinating Committee in Brussels formed a safety working group in 1971. Members are drawn from the participating governments, electricity producers, industrial concerns, research centers, and nuclear inspection bodies. They meet periodically to exchange information on R&D programs, to discuss problems of particular concern to FBR safety and to put forward methods of solving them, and to establish common safety criteria. Examples of the specific topics that members are concerned with are the interaction between molten reactor fuel and sodium coolant, secondary containment design, accidents that might arise from causes outside the power plant itself, and
future large-scale test installations and core meltdown/collectors. Deliberations are being expanded to include accident scenarios, the consequences of accidental radioactivity releases, postaccident heat removal, and the like. FBR safety studies in EC run to about $60 million annually. In addition, funding of support work at the EC Joint Research Center Laboratory in Ispra, Italy, exceeds $10 million annually. The EC Commission has called for "greater community involvement in fast reactor safety programs. Such involvement could contribute to strengthening the cooperation already existing, to intensifying and increasing the efficiency of national efforts, and ultimately to facilitating acceptance of fast reactors by establishing a coherent community approach.". Reprocessing of spent reactor fuel is an essential aspect of the overall nuclear fuel cycle. Indeed, the European view is that reprocessing is a prerequisite to all nuclear fission systems. The reasoning behind this stance is that spent fuel coming either from a conventional thermal reactor or from a fast reactor contains uranium-238 and plutonium-239, both of high commercial value. Their recovery becomes even more critical when there is a limit to the amount of uranium available. Before the uranium and plutonium can be refabricated into new fuel, however, they first must be isolated from the fission products formed during burning, and then separated from one another. Much of the reprocessing know-how has developed from the need to extract plutonium from thermal reactor spent fuel for military weaponry. Nuclear fuel reprocessing has been carried out at a number of sites in Western Europe for some years. At Eurochemic in Mol, Belgium, 13 countries collaborated in a multipurpose fuel reprocessing pilot operation between 1959 and 1975. At Windscale, on England's
Radioactive fuel transported in a steel coffin from Windscale
west coast, British Nuclear Fuels Ltd., a wholly owned subsidiary of UKAEA, has a commercial operation for reprocessing uranium metal fuel from Magnox reactors, so called because the fuel is clad in a magnesium oxide alloy. In addition to fuel from Britain's own network of Magnox reactors, British Nuclear Fuels reprocesses similar fuel on a contract basis for customers in Italy and Japan. A few years ago, British Nuclear Fuels adapted the plant to cope with spent oxide fuel from light-water reactors. This was stopped in 1973 following accidental release of radioactive fission products into the environment. The company now is seeking planning permission to install a large spent-oxide fuel reprocessing plant at Windscale. What started out as a fairly straightforward planning application to the local authorities escalated into a major public debate because of opposition to the
Novel energy sources and fusion may supply part of European Communities' energy in the next century Millions of metric tons of oil equivalent Total Conventional energy energy sources 8 requirement % of total
1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035
867 1050 1220 1370 1510 1640 1760 1860 1940 2000 2030 2055 2070
848 996 1125 1200 1245 1240 1195 1110 985 885 795 730 680
97.8% 94.9 92.2 87.6 82.4 75.6 67.9 59.7 50.8 44.3 39.2 35.5 32.8
Nuclear fisslon b % of total
19 54 95 165 250 360 490 620 760 860 910 930 910
2.2% 5.1 7.8 12.0 16.6 22.0 27.8 33.3 39.1 43.0 44.8 45.3 44.0
Novel energy sources 6 % of total
— — — 5 15 40 75 130 195 255 320 375 430
— — — 0.4% 1.0 2.4 4.3 7.0 10.1 12.7 15.8 18.2 20.8
Thermonuclear fusion % of total
— — — — — — — — — — 5 20 50
— — — — — — — — — — 0.2% 1.0 2.4
a Includes fossil fuels and hydroetectriclty. b Includes fast breeder reactors, c Includes solar, wind, wave, and geothermal power. Source: Commission of the European Communities
scheme from a number of quarters. Daily hearings were held for nearly four months last year before a panel of three judges led by Justice Roger Parker. Since the hearings ended last November, Parker has had the unenviable task of sifting through all the evidence and preparing a recommendation on the course of action to be followed. His report, due out imminently, will go to Peter Shore, U.K. secretary of state for the environment, who called the hearings in the first place. Meanwhile, at Dounreay, Scotland, a unit is nearing completion for reprocessing spent fuel from the adjacent prototype fast reactor. When it starts up around midyear, it will be the first plant in Western Europe designed specifically for coping with spent FBR fuel. In France, reprocessing is carried out at Marcoule in the south and at La Hague, some 12 miles from Cherbourg on the west coast. Cogema, the industrial arm of the French atomic energy commission, manages both facilities. The Marcoule operation has been under way for the past 20 years. The larger center at La Hague started up in 1967. Two years ago, it was adapted to reprocess up to 1000 metric tons annually of spent oxide fuel arising both from reactors in France and elsewhere. In addition to recovering uranium and plutonium, the La Hague plant isolates such valuable radionuclides as strontium-90, cesium-137, neptunium237, americium-241, and curium-242 from the fission products. Cogema gives a number of reasons for selecting La Hague for reprocessing. It is a fairly desolate region of the country. More important, tidal currents at that particular section of the coast reach speeds up to 10 mph so that liquid waste containing a low level of radioactivity may be discharged and rapidly dispersed without causing damage to the environment. Also, prevailing winds that blow seaward at a rate averaging 15 mph "greatly favor rapid dispersion of gaseous effluents." Feb. 13, 1978 C&EN
45
In 1971, British Nuclear Fuels, the French atomic energy commission, and Kernbrennstoff - Wiederaufarbeitungsgesellschaft (KEWA) of West Germany jointly formed United Reprocessors GmbH with headquarters in Karlsruhe. This commercial enterprise offers a complete range of irradiated oxide fuel reprocessing services including trans portation and reconstituting of uranium and plutonium fuel. Four chemical com panies have an equal stake in KEWA. They are Bayer, Gelsenberg, Hoechst, and Nukem. The company has been operating a 40 metric-ton-per year oxide fuel re processing pilot plant at Karlsruhe since 1971. Probably one of the most emotional issues associated with spent fuel repro cessing centers on disposal of the fission products. These vary widely in the time they take to decay—some have half-lives of many thousands of years—and in their radiation characteristics. The wastes fall into three categories: low-, medium-, and high-level, depending on the amount and character of the radiation they emit. Ra diation from low-level wastes ranges from 0 to 0.01 curie per eu m, that from me dium-level between 0.01 to 100 curies per eu m. High-level wastes include every thing higher than 100 curies per eu m. For obvious reasons, high-level wastes are the most insidious. These consist of βand 7-emitting isotopes such as strontium-90 and cesium-137 in addition to plutonium and other α-emitting actinides that are extremely radiotoxic if ingest ed. In a typical waste management proce dure, the liquefied wastes are stored up to 20 years in specially constructed shielded tanks to allow them time to cool and to allow the isotopes with short half-lives to decayi Ultimately, the plan is to incor porate them into glass blocks before dumping them in carefully selected sites—a process known as vitrification.
UKAEA scientists at Harwell were among the first to develop a vitrification process some 15 years ago. Their early Fingal process, since renamed Harvest, involves forming blocks of borosilicate glass with entrained inactive simulated waste liquors. Accelerated aging studies of the samples indicate that they are en vironmentally inert and that the degree to which the contained waste might mi grate or be leached out of the glass is negligible. Similar vitrification studies are under way in France. In a continuous process developed at Marcoule, the solution con taining thefissionproducts, together with additives, is poured into tubes fitted within a rotary roasting furnace. Some evaporation occurs in the upper region of the tubes, and roasting of the residue takes place lower down. The calcined product flows continuously into a melting furnace along with vitrifying additives. There, final roasting and vitrification takes place. An industrial-scale vitrifica tion plant was completed last year at Marcoule. A similar unit is planned for La Hague and is scheduled to be ready by Working on fuel element fabrication for 1982. fast reactors at Wlndscale Vitrification studies in West Germany include a modified concept. The waste- Belgians and Italians are examining clays, containing glass or ceramic material is and the Dutch and West Germans are converted to beads by a simple mechani evaluating salt. cal process. These are then incorporated The program got under way in earnest in a lead alloy matrix. The advantage a little more than a year ago and will cited for using the metal is that it pro continue into 1980. The cost likely will motes even distribution and dissipation reach $70 million or so. Funding will come of heat thereby avoiding the possibility of in part from the participating countries localized crystallization and cracking of and in part from central EC resources. the vitreous mass. Findings will be circulated among the The aim ultimately is to bury the vit participants. Each country then will make rified blocks, encased in thick concrete use of the results in formulating its own containers, deep underground at carefully waste disposal policy. There is no plan for selected sites. Six West European any one country to be chosen as a site for countries are collaborating in studying the repository of all European wastes. most suitable sites for deposition. The Deep borings first will be undertaken British and French are looking at sub to provide a profile of the underground terranean granite rock structures, the rock and soil structures. These will be
Spent fuel from thermal and fast breeder reactors can be recycled Uranium ore contains a mere 0.7% or so of uranium-235, the fissionable iso tope used to fuel conventional thermal reactors. The balance comprises uranium-238. This is nonfissile. 238 U, however, is fertile in the sense that when an atom of the isotope captures a neutron in a reactor core it is converted to fissile plutonium-239. Thermal reactors use a moderator to slow down the neutrons in the core. Moderators employed are graphite, water, or heavy water. The type of fuel depends on the kind of moderator in volved. Some thermal reactors use natural uranium metal as fuel. Most, however, use uranium dioxide with a higher-tharvnormal 235U content. Before such a fuel can be made, a step known as enrichment is called for. Here, the uranium oxide (U308) is converted to gaseous uranium hexafluoride (UF6), commonly known as "hex." By a diffu-
46 C&EN Feb. 13, 1978
sion technique, the concentration of 235 U is raised to a level of 2 to 4 % , depending on the reactor type. The re sulting enriched uranium then is fabri cated into U0 2 fuel elements. Within the reactor, some of the ura nium is destroyed, giving rise to a variety of fission products and transuranium elements. Some is converted to 239Pu; some of it remains unchanged. Spent fuel elements, on removal from thermal reactors, are stored for six months or so under water to allow them to cool. They then go to a reprocessing plant where uranium and plutonium are separated from the fission products and recovered. This is essentially a chemical operation involving solvent extraction. In a typical procedure, the spent fuel elements are broken up and dissolved in nitric acid. The solution passes through a series of mixer-settler tanks where the uranium and plutonium pass out of the
acid phase into a solvent such as tributyl phosphate. The acid solution with the fission products ultimately goes to evaporation and storage tanks for ra dioactive waste management. The ura nium and plutonium are separated from one another by selective solvent ex traction and recovered. Some of the uranium is recycled to the thermal reactor fuel fabrication plant. Some uranium dioxide, together with plutonium dioxide, may be made into fast breeder reactor fuel. In the fast breeder reactor itself, some of the original plutonium in the fuel is destroyed. At the same time, some of the uranium converts to plutonium. Spent fast breeder reactor fuel goes to a reprocessing plant where the fission products are separated from the urani um and plutonium by essentially the same methods used in reprocessing spent thermal reactor fuel.
Western Europe and the Soviet Union have active fast breeder reactor developments under way France
West Germany
U.K.
U.S.S.R.
Experimental reactor»
Prototype reactor·
Commercial reactor·
RapsocHe at Cadarache; startup 1967; 40 Mw(th) KNK-2 at Karlsruhe; startup 1968; 20 Mw(e) DFR at Dounreay; startup 1959; shutdown 1977; 15Mw(e) BOR at Melekess; startup 1969; 60Mw(e)
Phénix at Marcoule; startup 1973; 250 Mw(e) SNR-300 at Kalkar; under construction; 300 Mw(e) PFR at Dounreay; startup 1974; 250 Mw(e)
Superphénix at Creys-Mafville; under construction; 1200 Mw(e) SNR-2 being considered; 1200 Mw(e)
BN-350 at Shevchanko; startup 1973; 150Mw(e)* BN-600 at Beioyarsk; startup 1977; 600 Mw(e)
BN-1500 being considered; 1500 Mw(e)
;
CFR-1 being considered; 1300 Mw(e)
a The BN-350 reactor facility also 1$ designed to produce 120,000 eu m daily of fresh water by desalting Caspian Sea
Demonstrators stopping a train near Paris during "Antlnuclear day"
followed by such tests as seismological evaluation of the regions, and examination of the degree of water movement within the substrata. Ideally, the repository zones should be dry to avoid any possibility that the radionuclides will leach out and eventually recirculate, by way of aquifers, to the biosphere. In West Germany, plans are being laid to develop an integrated fuel reprocessing, refabrication, and waste disposal facility at Gorleben near the East German border. The operating company will be Deutsche Gesellschaft fur Wiederaufarbeitung von Kernbrennstoffen (DWK). Partners in DWK are Bayer, Gelsenberg, Hoechst, and Nukem, and a consortium of 12 companies and utilities that plan to build and operate nuclear power reactors in West Germany. These 12 concerns will take over the entire management of DWK at the end of this year. The chemical companies will drop out, although their chemists and engineers still will be directly involved. Gorleben is sited on a salt deposit some 12,000 feet underground. The intention is to place all the waste there. Already, low- and medium-level nuclear waste is being stored on a trial basis in a similar underground salt structure at nearby Asse. Scientists and engineers associated with the European FBR development in all its aspects readily agree that a number of problems still remain to be solved. But they voice confidence that they will in time solve those of a technical nature. Those of sociopolitical nature may prove less easy to cope with. In a lengthy and detailed evaluation of nuclear power and the environment drawn up in September 1976 by the U.K. Royal Commission on Environmental Pollution, warning signals were run up on the likely consequences of the arrival of
the plutonium economy. The commission members, headed by Sir Brian Flowers, rector of London's Imperial College of Science & Technology, noted that "our anxiety about the hazards of an economy based on plutonium leads us to the view that fast reactors should be introduced only if they are demonstrably essential." Among the fears they raised were the possibility of plutonium, "in widespread use as a staple commodity of energy supply" falling into the hands of terrorists, and the threat to civil liberties that might ensue from efforts to circumvent such a likelihood's occurring. However, UKAEA's Sir John Hill views as highly remote the likelihood of a terrorist gang's hijacking a shipment of fuel. "Remember," he says, "that trucks bearing the 80-ton steel flasks containing the fuel can travel at only 6 mph. So if a terrorist gang were to steal one, it wouldn't get very far before being overtaken. Moreover, it requires a 100-ton crane to remove a flask from the truck." He foresees the setting up of regional reprocessing centers to cope with fuel from a variety of reactor sources and redelivering the reconstituted fuel in the same 80-tonflasksin which the spent fuel arrived. "The chances of people stealing it, and hiding it, and then having a clandestine chemical plant and making a bomb all within a 6-mile radius of where they stole it seems to me to be highly remote," he reasons. Nevertheless, as an added precaution he suggests there is the option that before the fuel goes back to the customer it is irradiated in a small reactor. The resulting radiation of the fuel would effectively lock up the plutonium making it inaccessible even if it were stolen, he observes. "If you do that, proliferation, or theft, or terrorism is impossible. So I can see a way of running a fast reactor program with safety.
"There is certainly going to be international policing of fuel reprocessing and therefore of the production of new plutonium," Sir John comments. "And the plutonium that is produced will have to be used in an approved manner. The view I take is that the exporting government and the importing government and the United Nations International Atomic Energy Agency should be the three parties that agree to any fuel transfers." Arguing in favor of the EC countries' FBR evaluation programs, Dr. Mario de Bacci, head of the EC commission's Office of Reactor Development & Advanced Technologies in Brussels, points out that the few fast reactors that will come into operation by the year 2000 won't add significantly to the store of plutonium. "Practically all the plutonium that will exist in 1990 or 2000 will have been produced by thermal reactors." De Bacci makes the added point that "the problem of proliferation as we will understand it in the year 2000 will be different from what we understand it now. The political situation will be different; the technical situation will be different. Twenty-three years from now it will be seen in another light because one will know more about it. The techniques of enrichment will have improved; the techniques of protection will have progressed. "The question is, should we lose these next 23 years doing nothing, or should we rather do what is necessary and sufficient to learn enough to master these problems?" In· answer to his own question he says, "What we in the EC must do is to keep an effective option open to be able in the year 2000 or so to have this [fast reactor] industry ready to take off if required. We must do everything up to then to get to that condition. If we don't, we will have another problem." D Feb. 13, 1978 C&EN
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