Superphénix, the world’s largest fast-breeder reactor, began operation in Creys-Malville, France, as part of a joint European project to develop nuclear energy.
As a result of the energy crisis of 1973 and the sudden quadrupling of the price of crude oil, many countries adopted research programs to investigate the commercial feasibility of alternative energy sources. One energy source that engendered considerable interest was nuclear energy, which can be used to produce electrical power in nuclear reactors.
The type of reactor used for the generation of electricity employs fission reactions, which split large atomic nuclei apart to produce smaller nuclei and energy. The isotope uranium 235 (U-235) is the fissile, or fissionable, isotope naturally present in ore deposits, having a half-life (the time for one-half of an original sample of U-235 to decay) of 704 million years. When it absorbs a stray neutron, this fissile isotope naturally fissions into two smaller nuclei and several free neutrons, releasing heat energy in the process. U-235, however, constitutes only 0.7 percent of naturally occurring uranium. The remaining 99.3 percent is composed of U-238, a nonfissile isotope. Nuclear power stations employ reactors that use the rare isotope U-235 as their fuel. Given that the continued exclusive development and deployment of reactors using U-235 as their fuel source would exhaust commercially feasible ore deposits in several decades, such reactors would not offer a long-term solution to the global energy problem.
It has been known for decades, however, that the absorption of a neutron by the nonfissile isotope U-238 (preferably a fast-moving neutron) results in a transmutation of that isotope to neptunium 239 (Np-239). Np-239 then spontaneously transmutes to plutonium 239 (Pu-239), which is a fissile isotope with a half-life of 24,400 years. This process can effectively convert the nonfissile U-238 into fissionable fuel, thereby creating a manyfold increase in the available worldwide supply of fission fuel. Realizing this, scientists and engineers set to the task of designing and demonstrating the feasibility of a nuclear reactor that could produce energy by fission while at the same time converting nonfissile U-238 into fissionable Pu-239. This type of reactor is known as a breeder reactor.
Nonfissile U-238 readily absorbs fast neutrons such as those given off in fission reactions far more efficiently than it absorbs slow neutrons; breeder reactors designed to take advantage of this property are called fast-breeder reactors. A coolant commonly used in fast-breeder reactors is liquid sodium metal. In spite of its vigorous chemical reactivity with water, liquid sodium metal’s physical properties make it attractive for use with fast-breeder reactors. Such reactors are known as liquid metal fast-breeder reactors
Under the guidance of the Commissariat à L’Énergie Atomique (CEA) of France, a consortium of French, West German, and Italian utility companies began construction of Superphénix, a full-scale industrial prototype for a commercial 1,200-megawatt liquid metal fast-breeder reactor power station, in the fall of 1976. This project commanded worldwide attention because it represented the first attempt to build a commercial-scale fast-breeder reactor. France’s national utility Electricité de France covered 51 percent of the cost of construction of Superphénix. The other major national financial partners were Italy (33 percent), West Germany (11.04 percent), the Netherlands (2.36 percent), Belgium (2.36 percent), and the United Kingdom (0.24 percent). Construction of Superphénix was completed in December, 1985; the total cost of building the station was $5 billion.
Superphénix nuclear power plant in Creys-Malville, France.
Superphénix represented the culmination of a program designed to bring a new, capital-intensive technology into commercial use. The program began with an experimental reactor called Rapsodie, which was followed by a demonstration plant, Phénix, followed by the large-scale prototype power station, Superphénix. In spite of the successful track records of Rapsodie and Phénix, Superphénix was plagued almost from the start by technological problems, particularly in its liquid sodium cooling system. In February, 1994, the French government announced that it was abandoning the concept of Superphénix as a prototype fast-breeder power station and had chosen to reconfigure the core so that the reactor would serve in the opposite capacity—that is, as a debreeder, designed to consume more plutonium than it produces, thereby potentially reducing France’s increasing stockpile of plutonium generated by its conventional nuclear power plants. However, even these plans ultimately proved economically and politically unattractive, and the project was formally terminated in June, 1997.
The French government was particularly concerned with the country’s energy stability following the energy crisis of 1973. France accounts for only 0.7 percent of the world’s energy production and has only 0.1 percent of the world’s energy reserves. In 1974, France imported 75 percent of its energy needs. Although this figure had been reduced to 61 percent by 1983, it nevertheless demonstrates France’s vulnerability to external factors for meeting its energy needs. On the other hand, with more than one-half of Western Europe’s uranium reserves, France had the potential to develop a considerable degree of independence from energy imports. Consequently, the logical strategy for France was to develop a strong, aggressive program to develop nuclear energy.
To understand the impact of Superphénix on the development of fast-breeder power stations, it is helpful to track the development that led to Superphénix, beginning with Rapsodie, France’s first experimental breeder reactor. Rapsodie was constructed during the period 1962-1966, and its initial design to produce 20 megawatts of thermal energy was subsequently increased to 40 megawatts during the period 1970-1979. Following the initial successes of Rapsodie, the CEA began the construction of Phénix, a 250-megawatt demonstration plant, beginning in 1968 at Marcoule, France. Both these facilities were liquid-sodium-cooled fast-breeder reactors.
In early 1982, the operators of the Rapsodie facility detected a small leak in the reactor; the nature of the leak and its location led operators to the conclusion that the reactor could not be repaired in a reasonable amount of time or at reasonable cost. Following a series of scientific and safety tests, the reactor was permanently shut down in April, 1983. In April, 1982, a leak developed in a steam generator at the Phénix plant. After shutdown and repairs, Phénix was brought back online on June 24, 1982. Although tests and data showed that the reliability of the equipment was impressive, the leaks that developed in the cooling system foreshadowed the problems that plagued and eventually caused the abandonment of Superphénix as a commercial fast-breeder power station.
When Superphénix was completed in December, 1985, it represented the largest fast-breeder reactor yet constructed, rated at a 1,200-megawatt electrical output with an efficiency of 41.5 percent. It was expected to contribute from 1.5 to 2 percent of the total installed electrical power on the French grid. Prior to the completion of Superphénix, the largest breeder reactor was the Bieloyarsk BN 600 reactor in the Soviet Union.
In March, 1987, after one year of operation, a sodium leak was discovered in Superphénix. The leak appeared to be in a subsidiary storage tank in which fuel rods were stored temporarily during their removal from the core of the reactor. The occurrence of the leak had a significant impact on the funding of a planned sister reactor, Superphénix 2; West Germany and Italy were reluctant to commit finances to this proposed successor. Furthermore, during the 1980’s the cost of uranium was declining. Consequently, the energy produced by Superphénix was approximately twice as expensive as energy produced by conventional light-water reactors using enriched uranium. Therefore, not only France’s partners but also other nations worldwide were questioning the wisdom of pursuing the expensive programs required to develop LMFBR technology. Several nations eventually did abandon their efforts, and France shelved its plans to build Superphénix 2 in 1989.
Early in the subsequent twenty-month shutdown of Superphénix, fissures were found in the inner lining of the reactor’s storage tank. The engineering staff of Electricité de France proposed replacing the liquid sodium with inert argon gas as a coolant inside the affected storage chamber, removing the defective lining, and restarting the reactor. Engineers estimated that they would have about one year to modify the storage chamber before the reactor required shutdown. The French government decided to restart the reactor based on this recommendation, even though the storage tank was the only place to store the fuel rods in the event of an accident requiring their removal from the core.
Problems resulting from the leaky cooling system continued to plague Superphénix. In December, 1990, the roof of the turbine hall collapsed under the weight of a heavy snow accumulation, forcing yet another shutdown. In 1992, Superphénix was ready to be brought back online, but the prime minister of France, Pierre Bérégovoy, placed the plan on hold. Prompted by a concern over accumulating stockpiles of plutonium, Bérégovoy established a commission to investigate the benefits of restarting the plant and the proposal to convert Superphénix to a plutonium debreeder.
In February, 1994, the French government announced that Superphénix would no longer function as a commercial prototype for power generation, as originally intended. Rather, Superphénix would be modified to carry out research into the disposal of nuclear waste, particularly excess plutonium generated by France’s light-water reactors. It was estimated that Superphénix could dispose of approximately 200 kilograms, or about 440 pounds, of plutonium per year in the new configuration. Nearly fifty tons of plutonium are generated per year by more than fifty French nuclear reactors. In spite of the failure of Superphénix as a commercially viable fast-breeder reactor, France remained committed to developing nuclear power to meet its energy needs.
Superphénix’s technological problems and their financial consequences contributed to a widespread loss of confidence in commercial fast-breeder reactors. Both Great Britain and West Germany abandoned their fast-breeder programs late in the 1980’s. In addition, unexpectedly low prices for petroleum and low costs for traditional reactors using enriched uranium fuel caused the nuclear power industry to discontinue development of fast-breeder reactor technology.
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Atkins, Stephen E. Historical Encyclopedia of Atomic Energy. Westport, Conn.: Greenwood Press, 2000. Comprehensive volume covers all aspects of humankind’s research into and use of nuclear power. Includes chronology, bibliography, and index. -
Bethe, Hans A. “The Necessity of Fission Power.” Scientific American, January, 1976, 21-31. A Nobel laureate in physics presents a well-balanced argument for the need to develop nuclear power. -
Coles, Peter. “Reactor Restarts sans Repair.” Nature 337 (January 19, 1989): 327. Brief article announces the anticipated restart of Superphénix in 1989 and the plan to repair the storage tank. -
Dickson, David. “Superphénix Springs a Leak.” Science 236 (April 17, 1987): 248. Discusses the sodium leak that Superphénix developed in March, 1987. -
Dorozynski, Alexander. “Superphénix Set to Rise Again.” Science 262 (October 15, 1993): 327. Brief article discusses the alteration of the Superphénix nuclear core so that it burns more plutonium than it produces, thereby turning the reactor into a plutonium incinerator. -
Patel, Tara. “Troubled Rebirth for French Fast Reactor.” New Scientist, March 5, 1994, 7. Discusses the French government’s decision to restart the reconfigured Superphénix as a debreeder to dispose of plutonium produced by other reactors. -
Seaborg, Glenn T., and Justin L. Bloom. “Fast Breeder Reactors.” Scientific American, November, 1970, 13-21. Gives a comprehensive description of the liquid metal fast-breeder reactor. Easily understood by the layperson; a good starting place to understand the subject. -
Vendryes, Georges. “The French Liquid-Metal Fast Breeder Reactor Program.” In Annual Review of Energy, edited by Jack M. Hollander and Harvey Brooks. Vol. 9. Palo Alto, Calif.: Annual Reviews, 1984. Presents a comprehensive technical analysis of the French fast-breeder reactor program. Offers a clearly argued justification for the program and the expected outlook and projected impacts of a successful program. Does not, however, anticipate the technical difficulties that led to the premature shutdown and redirection of the reactor. -
_______. “Superphénix: A Full-Scale Breeder Reactor.” Scientific American, March, 1977, 26-35. Excellent article provides clear diagrams of the Superphénix reactor design and fuel assembly design as well as comparative statistics regarding Phénix and Superphénix. Also describes the physics of the transmutation of U-238 plus neutron into Pu-239.
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