Electricite de France standardized designs: Modifications management

For the last 12 yr, from 1977 to the end of 1988, Electricite de France (EdF), the only electrical utility in France, has commissioned 48 pressurized water reactor nuclear units representing 47,000 MW. The advantages of standardization are well known; Germany and the United States have already launched projects based on that principle. The standardization concept, however, should not be considered as a freezing of the design. In fact, due to several factors, a permanent evolution of the design is unavoidable, and EdF has implemented numerous modifications on each of its units in order to improve the efficiency and reliability of the equipment and to increase its life duration. These modifications concern all the technical engineering and safety fields. Their cost range from thousands to millions of dollars. The paper explains the origin of the modifications and the problems encountered by EdF to oversee modifications not implemented simultaneously on different units of the same series.