The choice of the chiller sodium helium or lead also debate

Chained they were there a month on the route of the nuclear convoy to Gorleben German storage site, environmentalists have missed the signing of an agreement of strategic cooperation between scientists at the Office energy Atomic (CEA) and Areva. It is the first design studies of the prototype reactor Astrid (Advanced Sodium Technological Reactor for Industrial Demonstration) which, according to its promoters, marks the debut of "clean nuclear age". Provided through 2017 with a workforce of 350 experts, this research program will allow the Government whether or not the construction of a demonstrator who will work with one heart to fast neutrons, a technology expected to let it recycling and transmutation of ultimate wastes (neptunium, americium, curium, and minor actinides).

With this new step, the scientific and technical options specify around the development of a "sustainable" nuclear sector "We are moving from concept to a proven scientific reality which is now the engineering work," says Bernard Boulis, Director of the program of recycling and waste at the CEA. A few grams of americium into the circuit of combustion of Phoenix were sufficient: a few months, the neutron bombardment resulted in destroying a third of this mixture of long-lived nuclear elements for which there is now no way to remove.

Ultimate waste

Since then, it is the excitement in laboratories. National borrowing launched early this year allocated EUR 1 billion to research in civil nuclear power, of which 65 will be for Astrid. "This new generation reactor will wear the transmutation on a significant scale and after a few years of operation, it could have the ability to burn as many minor actinides it produces," prognostic François Gauché, head of programme at the CEA-fourth generation reactor. Ultimate waste then confined to fission products (currently either 4 of the spent fuel). Get rid of the minor actinides, these wastes be the level of radioactivity of natural uranium nor after tens of thousands of years, but after three hundred years only. "Under these conditions, said Bernard Boulis, ultimate waste storage will become a technically acceptable option, because perfectly controllable."

The feasibility of the transmutation of minor actinides assumes upstream a separation phase which will change significantly the fuel cycle. It is the purpose of the research conducted by the laboratory Atalante (workshop Alpha and laboratories for ANalyses, Transuranium and reprocessing studies). "The chemists of the ECA found molecules extractantes, selective and resistant especially for americium, curium or to retrieve products of fission as cesium", details Bernard Boulis. They also demonstrated experimentally on a dozen kilos of fuel that the selective recovery of minor actinides was possible on an industrial scale. In 2012, a point of step will be completed to take stock of these research and propose tracks of extraction in the cycle.

Technological locks

Driven by the same objectives of recycling, the Belgian nuclear study centre (SCK - CEN) researchers took advance in inaugurating this summer a scale model of a new generation fast neutron reactor whose objective is to test a system of control of chain reactions, ADS (Accelerator Driven System), essential precondition to the incineration of long-lived waste. Principle will be based on a particle accelerator in which deuterium (an isotope of hydrogen) will be added to an ion source before be pointed at the target (of the tritium) where reactions occur.

"When an ADS is in operation, says Annick Billebaud, group physics of reactors at the laboratory of subatomic physics and Cosmology, it is fueled by this external source neutron and the number of fissions in the reactor core is constant." When it stops the accelerator, the chain reaction is more maintained because there is more enough neutrons in the core. The number of fission decreases very rapidly, in microseconds, and the system stops.

The development of this reactor research, started in 2007, required an investment of EUR 10 million. His older brother, Myrrha, 100 times more calls to raise the technological locks that industrial-scale of the reactor. "The main difficulty is to design an accelerator that can produce a continuous and stable neutron beam," says project manager, Peter Baeten. The choice of the chiller (sodium, helium or lead) also debate. Twenty French, Belgian, German, Spanish and Italian researchers will be involved in the research which must last for four years before the launch of an industrial prototype, at the same time as the reactor French Astrid. Own nuclear proliferation began.