Contribution of fission products to displacement damage in fast reactor fuel cladding

摘要

The number of Displacement per Atom (DPA) in the fuel cladding is a key quantity for determining the operation lifetime of fuel assemblies in Sodium-cooled Fast Reactor (SFR). Since the cladding is directly irradiated by Fission Products (FPs), the present work evaluates the FPs-induced atomic displacements in the Fe-14Cr cladding. Three degrees of freedom (the yields of FPs, energy distribution, and angular distribution of each FP) are reduced using the assumptions proposed in this paper. Two additional approximations are proposed to obtain the reasonable upper and lower limits of DPA in the cladding so that the computation burden is largely reduced. Numerical results show that the proposed approximations can give a reasonable estimate of the FPs-induced DPA in the fuel cladding. The FPs-induced damage is limited in the range of few microns but can be 5 times more important than the neutron-induced one in the cladding of ASTRID inner core. Along with the depth in the cladding, the FPs-induced damage rate becomes less important than the neutron-induced one at penetration deeper than 5 mu m and smaller than 1/10 of neutron-induced DPA at penetration larger than 7 mu m. A subsequent question of whether the FPs-induced damage should be taken into account in the cladding needs to be discussed for SFRs. (C) 2020 Elsevier Ltd. All rights reserved.