LWR MOX fuel experience in Belgium and France with special emphasis placed on the results obtained in the BR3 PWR

MOX fuel has been developed since 1958, first on a laboratory scale, later at the pilot level and finally to an industrial operation stage. This progressive approach to maturity has resulted in improvement of the fabrication processes, leading to an appropriate fuel, and collection of the database required to qualify the fuel for scheduled operation. The key to success has been the experience built up through fabrication of large quantities of MOX fuel and irradiation of experimental or characterized fuel assemblies in various PWRs and BWRs. In particular, MOX fuel rods manufactured by BELGONUCLEAIRE (BN) following two fabrication processes (mechanical blending and micronized master blend powder) were irradiated in the BR3 PWR under various steady state operating conditions. Surveillance and post-irradiation examination of MOX fuels from BR3, CNA, Dodewaard and Garigliano are already providing the performance references required. The main conclusions can be summarized as follows: (1) MOX fuel is now fabricated industrially at the same quality level as U fuel; (2) MOX fuel irradiation behaviour is superior to that of U fuel; (3) an adequate database already exists for the actual irradiation conditions in LWR power plants. The R and D programme is being pursued in a timely manner to acquire, for steady state and transient operating conditions, the expanded database required for the more demanding irradiation conditions contemplated in the future. (author)