Reproduction of shielding concrete activation measurements by simulations

Abstract

With the increasing number of decommissioning projects, radioactive waste estimation of biological shielding concretes is becoming more and more important. Simulation tools supporting this activity, like MCNP and Cinder are already available; however, publicly available neutron spectra in shielding concretes are limited. The aim of the study was to present and evaluate possible model arrangements for accurate neutron transport to deeper points of shielding concretes from the reactor pressure vessel. Representation of reality, neutron behavior and activity generation of seven long-lived radioisotopes (54Mn, 60Co, 65Zn, 133Ba, 134Cs, 152Eu and 154Eu) were assessed in each arrangement. After evaluating several model geometries, a conical shape neutron reflecting surface was shown to be the most suitable one to reproduce neutron fields in deeper layers of shielding concretes from a monodirectional initial neutron source.