Overview of the feed back experience from French Sodium Cooled Fast Reactors operations

The French experience in operating Sodium Cooled Reactors consists of the design, construction and operation of three plants: RAPSODIE, PHENIX and SUPERPHENIX. RAPSODIE and PHENIX were operated successfully for many years and life extension of PHENIX was performed. On SUPERPHENIX, time lacked for a full demonstration but operation on the plant proved that the industrial size is successfully achievable; this is confirmed by the excellent operation of the plant during the year 1996. Burn-ups over 150,000 MWd/t were achieved on oxide fuel, with a dose damage of more than 150 dpa on core materials, through extensive irradiation programmes in RAPSODIE and PHENIX. Sophisticated computer codes have been developed and validated in the fields of fuel behaviour, core physics, accident analysis and structural integrity. The technology of sodium, quite specific of these reactors, was developed so as to enable full mastering of large circuit operation. Although a number of difficulties were encountered, they never put into question the safety or technological feasibility, even if they incurred some adverse consequences on plant availability. During the life extension programme of PHENIX, a considerable experience was gained in many areas such as the methodology, material and components behaviour, and inspections techniques. Experimental feedback from the present dismantling operation in SUPERHENIX will be useful for the future decommissioning of existing LMFR as well as for the design of future reactors. Design, construction and operation of the three plants gave successively the opportunity to improve the LMFR safety approach, accounting for the fast reactor's specificities, while consistency compared with LWR safety approach is kept. In accordance with the Safety Authority recommendations, exhaustive safety analyses were performed, recorded in regulatory reports, and sophisticated safety design provisions were developed. A special attention has been paid to the preservation of the knowledge accumulated, in order to be re-used in the next future, in view of an industrial development of sodium cooled fast reactors. (author)