Group " Back end of the Cycle and Nuclear Energy"
Energy issues on the world level in 2050 perspective are considerable. In fact, the energy consumption will increase in the next 50 years by a factor 2 to 3. It is necessary to realize that during these 50 years, the world population will consume more energy than throughout the history of humanity and, paradoxically, it will be imperative to limit the consumption of fossil fuels in order to preserve the environment and to control the “greenhouse effect”.
Nuclear energy, like wind, hydraulic and solar energies, can produce electricity without the emission of carbon dioxide or other gases that lead to “greenhouse effect”. Far from being competitors, nuclear energy and “innovative renewable energies” are tightly associated as the ones that can satisfy the huge world demand in clean and long-lasting energy. However, nuclear energy nowadays is the only well-tried option that is capable to generate the large amounts of electricity required on the world level.
Research activities on the nuclear energy cycle
- The principal questions that arise in the debates concerning the nuclear energy cycle are limited uranium resources and accumulation of wastes connected to the present nuclear energy cycle. The law of December 30, 1991 (Bataille law) had imposed the obligation for the research agencies to study the options to manage radioactive wastes that accompany the production of nuclear energy.
The new law (June, 2006) concerning the long-term management of radioactive waste is a prolongation of “Bataille” law and sets the timeframes for various solutions to be put into operation. For the separation and transmutation of long-lived radioactive elements (axis 1), the corresponding studies and research activities will have to be conducted along the tracks for new generation of nuclear reactors mentioned in the program of the law of July 2005 that stated the directions of the energy policy as well as along the path for the pilot reactors with accelerators dedicated to the transmutation of the wastes. This law has clearly indicated the importance of considering the issue of waste in relation to the future nuclear options. It requested to make the evaluation of industrial perspectives for these channels by 2012 and to put into operation the prototype of the facility before December 31, 2020.
- Numerous CNRS teams are involved with the aspects of incineration of these wastes in sub-critical reactors controlled with the accelerator (ADS - Accelerator Driven System) as well as with the issue of the nuclear fuel that would not exhaust the resources and produce less waste.
The promising direction taken by CNRS is the MSR Th/U (molten salt reactor on the base of thorium) that not only produces wastes that are about thousand times less radiotoxic than in conventional PWR (pressurized water reactor) but also can regenerate the fuel (there are as many fissile nuclei U consumed as produced).
- In both cases, for transmutation of wastes or innovative fuel cycle like for example (Th/U), the studies rely on numeric simulations of high complexity whose precision is limited by experimental neutron cross-sections (capture and fission). Insufficiencies and/or disagreements in the databases are clear in the case of major isotopes: Pa and U in the Th cycle. The same is true for minor actinides (isotopes of Americium and Curium) for which transmutation by fission is currently envisaged. The necessity to improve the neutron databases gave birth to a vast international effort on measurements of cross-sections for reactions induced by thermal and fast neutrons. The group ACEN («Back End of the Cycle and Nuclear Energy») of CENBG contributes towards this effort.