Attenuation of atomic displacement damage in the heavy reflector of the PERLE experiment and application to EPR

Abstract

The investigation of atomic displacement damage is important for studying the irradiated materials. The present work proposes two equations to describe the total neutron-induced and gamma-induced Displacement per Atom (DPA) rates versus the penetration in materials. The attenuation of DPA rate in materials is studied in the heavy reflector of the PERLE experiment. The proposed analytic formula for neutron-induced atomic displacement well describes the Monte Carlo simulated results with two fitting parameters, while the formula for gamma-induced DPA is in agreement with Monte Carlo simulations with potential 10% uncertainties. It is noticeable that the neutron flux above 0.5 MeV is more representative than that above 0.1 MeV or 1 MeV for the attenuation of DPA in the heavy reflector. Due to the representativity of the PERLE experiment for the heavy reflector of Evolutionary Pressurized Reactor (EPR), an analytic expression of displacement damage is obtained. The atomic displacement rate at the inner surface of EPR heavy reflector is 1.4 DPA/year (using the standard Norgett-Robinson-Torrens (NRT)-DPA metric). The DPA rate at the outer surface of the reflector is reduced by a factor of 9 (and 32) as the thickness of the steel increases from 2 cm to 20 cm (and 30 cm).