Uranium enrichment by laser: A technology for the future

Even though the world enrichment market experiences disruptions which are both considerable and lasting the french approach is based on long term prospects: the aim is to have methods of enriching uranium at one's disposal which are autonomous and competitive in an environment of strong international competition. About fifteen years ago, the CEA decided to develop SILVA (Isotope Separation by Laser on the Atomic Vapour of Uranium) process, a process based on laser photo-ionization on the atomic vapour of uranium. This decision led to a significant research and development programme, led jointly by the CEA and the industrial operator COGEMA. SILVA uses the difference between the excitation frequencies of the electron layers (electronic transition) of uranium isotopes. The light emitted by a laser can be tuned to these frequencies, causing the excitation of the chosen isotope, in this case uranium 235. This excitation leads to the ionization of the atom: the ions are then separated by an electrical field and received by the dedicated collectors. This separation method is highly selective (achieving enrichment in only one step). The research programme really took off in the mid '80s, the scientific feasability being demonstrated in 1991. Since this date, a considerable number of results have been obtained both for the mastering of the process and in the form of technological breakthroughs. A special test has confirmed the suitability of SILVA physics for the enrichment of reprocessed uranium - SILVA enriches uranium 235 without increasing the content of even isotopes (such as 234, 236) which are undesirable in the production of fuel. The future programme will show the industrial operability of specific components (internal structures of the separator, lasers, optical components) and materials specific to SILVA.