QUALIFICATION OF THE APOLLO 2 ASSEMBLY CODE USING PWR-UO2 ISOTOPIC ASSAYS. THE IMPORTANCE OF IRRADIATION HISTORY AND THERMO-MECHANICS ON FUEL INVENTORY PREDICTION

摘要

The work presented in this paper is part of the qualification procedure of thernAPOLLO 2 neutronic code for calculating the depletion of 17x17 UO2 PWRrnassemblies. The fuel inventory calculation was qualified through the analysis of fuelrnirradiated for 2 and 3 cycles in BUGEY 3 (3.9% enriched - maximum burnup fractionrn: 38.3 GWd/tm) and fuel irradiated for 2, 3, 4 and 5 cycles in Gravelines (4.5%rnenriched - maximum burnup fraction : 60 GWd/tm).rnThe determination and qualification of the APOLLO 2 calculation process forrndepletion, is an important stage in reproducing an accurate inventory of the fuel.rnThis work also identifies the need to precisely describe the irradiation history (fuelrntemperature, moderator temperature, boron control, power).rnThe trends observed through the BUGEY 3 programme and the Gravelinesrnprogramme are consistent and demonstrate the ability of APOLLO 2 to accuratelyrnreproduce the fuel inventories for 17x17 UO2 PWR assemblies : the concentrationsrnof the main actinides U235, Pu239, Pu240 are reproduced with greater than 2%rnaccuracy.