Calculation of DPA for the VVER-1200 Reactor Vessel

Abstract

Neutron irradiation damage is of the most critical damage mechanisms in reactor vessel (RV) steel. Neutrons transfer their kinetic energy to target atoms of RV steel that start to jump creating vacancies and interstitials known as Frenkel Pairs (FP). The FPs are responsible for formation of defected clusters and microstructural modifications. These effects deteriorate physical and mechanical properties of the RV steels among which results in limiting the lifetime of reactor vessel. The most sensitive location in the RV related neutron irradiation damages is the area adjacent to the middle of the reactor core. In this paper, Monte Carlo simulation of the detailed reactor core have led to identifying the areas maximum neutron flux in the RV. Then the SRIM/TRIM Monte Carlo codes are used to evaluate the neutron spectral-averaged Displacements Per Atom (DPA) values for the RV region with the most intense neutron irradiation.