EVALUATION OF DRIVER FUEL PERFORMANCE IN THE JOYO MK-II CORE

Experimental fast reactor ''Joyo'' attained first criticality of its M k-II core (irradiation core) in 1982. Peak burnup and fluence has reac hed 83 MWd/kg M and 10 x 10(26) n/m2 (E > 0.1 MeV), respectively. Eval uation of the performance of Joyo Mk-II driver fuels has been carried out based on the post-irradiation examination (PIE) results including the highest burnup assembly in the core. The results showed that the p erformance of the Joyo Mk-II driver fuels was excellent and they were used with enough margin for the design criteria, suggesting the actual lifetime could be extended beyond the design limit. A large body of t he PIE data of the driver assemblies and fuel pins made it possible to conduct a reliable evaluation of the fuel performance.