Radiation characteristics of reactor structures after the final shutdown of a nuclear power plant with VVER

Abstract

A method for obtaining computational estimates of the radiation characteristics of irradiated structures in RBMK reactors is described. It is based on the MCNP computer program for calculating the spatial distribution of the neutron flux density inside the shaft. The nuclear transmutation occuring in the materials of the structures under irradiation in the reactor and during the subsequent holding period is simulated by the CHAIN program for calculating the isotopic composition and the radiation characteristics on the basis of the MCNP fluxes. Some results of a calculation of the radiation characteristics of the structures in the reactors in the No. 2 and No. 3 units of the Leningrad and No. 1 unit of the Chernobyl nuclear power plants are presented. Estimates of the total activity of the reactors structures and the dose rate near individual components are presented. The distribution of the mass of the structures over the degree of radioactivity is obtained as a fucntion of the holding time of a unit.