The troubled operational life of the sodium-cooled fast breeder reactor Phenix at Marcoule in southern France, ended on March 6. The reactor, which has been operated at 140 MWe on two of its original three loops for the past decade, will be shut permanently at year-end. The closure calls into question the future of French (and international) transmutation tests, which were conducted in the reactor. Phenix was connected to the grid 35 years ago and originally rated at 250 MWe.
Transmutation of long-lived minor actinides in separated reactor waste into shorter-lived nuclides is seen as complementary to a spent fuel and waste management system based on reprocessing and recycling of plutonium and uranium. (see box) Proponents say transmutation holds the promise of dramatically reducing the period during which waste in a deep repository would have to be demonstrated as not giving rise to potential unacceptable doses on the surface. Studies in France and elsewhere have concluded that transmutation in thermal reactors is inefficient. Operation of Phenix as a transmutation facility was crucial to the scientific studies produced by the CEA, as directed by France’s 1991 waste management R&D act and the follow-on waste planning act of 2006.
As long as the Monju fast breeder reactor in Japan remains offline, there is no similar facility in which to run the experiments on fast reactor fuel and on transmutation of long-lived radionuclides that have been conducted in Phenix. Within the Generation IV International Forum, Japan has the lead role in development of sodium-cooled fast reactor technology. Monju is supposed to be the test bed for a program called Gacid (Global Actinide Cycle International Demonstration) that aims to demonstrate the full fuel cycle for partitioning and transmutation of minor actinides.
Monju, located in Tsuruga, Fukui Prefecture in Japan, is a 280 MWe sodium-cooled fast breeder. Construction started in 1985 and it achieved first criticality in April 1994. It is closed following a serious sodium leak and fire on December 8, 1995. Monju is expected to resume operation in 2010, however, that has been delayed many times. The unavailability of Monju “is not a bottleneck,” Bernard Bigot, the new administrator general of the French atomic energy commission, the Commissariat a l’Energie Atomique, said. France’s 2006 waste act calls for a conclusion on the feasibility of transmutation in a fourth-generation reactor by 2020. Bigot said that means there is time to reorganize the R&D program if the Japanese reactors can’t be used.
Phenix, originally rated at 250 MWe, was built and operated by CEA as a prototype for a commercial series of fast reactors. To demonstrate that a fast reactor could produce electricity, EDF took a 20% stake in the project and was responsible for the power conversion and generation side of the plant. Phenix has had various problems since it first achieved criticality in August 1973. In the next two decades, it experienced equipment and materials problems, including corrosion and fatigue-related cracking on austenitic steel components in its secondary circuits. Reevaluation of the seismic risk at Marcoule required considerable structural work.
In late 1989 and in 1990, Phenix experienced a series of four automatic scrams due to abnormal reactivity drops. After operating off and on for another cycle, Phenix was taken down in April 1995 for a major refurbishment and safety program estimated to have cost up to Eur250 million.
In late 1998, Phenix was given a reprieve from final shutdown by the then Left-Green government in exchange for a political decision to close it successor, the 1,240-MW Superphenix commercial demonstration FBR. Billions of euros had been invested in Superphenix, particularly by Electricite de France, which owned 51% of the facility.
Source: Nucleonics Week, 19 March 2009
Contact: WISE Amsterdam
Generation IV reactors (Gen IV) are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2020-2030. Current reactors in operation around the world are generally considered second- or third-generation systems, with the first-generation systems having been retired some time ago. The term 'Generation IV' was first mentioned on a January 2000 meeting of the Nuclear Science & Technology department of the US Department of Energy.
Minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium. The most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.
Nuclear transmutation is the conversion of one chemical element or isotope into another, which occurs through nuclear reactions. Natural transmutation occurs when radioactive elements spontaneously decay over a long period of time and transform into other more stable elements. Artificial transmutation occurs in machinery that has enough energy to cause changes in the nuclear structure of the elements. Nuclear transmutation is considered as a possible mechanism for reducing the volume and hazard of radioactive waste. However, in practise many dangers, problems and uncertainties makes the whole concept very unlikely and undesired.
Read more: "Nuclear Alchemy Gamble: An Assessment of Transmutation as a Nuclear Waste Management Strategy", IEER 2000, available at: http://www.ieer.org/reports/transm/summary.html