Conservative approach for PWR MOX Burnup Credit implementation

Burnup Credit allows considering the reactivity dec rease due to fuel irradiation in criticality studie s for the nuclear fuel cycle. Its implementation requires to carefully analyze the validity of the assumption ma de to: define the axial profile of the burnup, determine t he composition of the irradiated fuel and compute t he criticality simulation. In the framework of Burnup Credit implementation for PWR mixed oxide fuels (MOX), this paper focus on the determination of a conservative inventory of th e irradiated fuel. The studies presented in this pa per concern: the influence of irradiation conditions and of the MOX fuel initial composition on the irradiated MOX fuel reactivity. Criticality calculations are also perfo rmed for PWR MOX fuel industrial applications in order to get Burnup Credit gain estimations.