A point kernel model for the energy deposited on samples from gamma radiation in a research reactor core

A basic safety requirement for a research reactor is the reliable estimation of the gamma heating of samples irradiated in the reactor core. A three-dimensional numerical code of gamma heating using a point kernel parameterization is developed. The heating due to γ-rays, produced from U235 fission and from (n, γ) reactions with the core materials is considered. The dose build-up due to photons scattering on the core materials as well as the energy absorption build-up in the sample are also included, based on empirical relationships. The developed code (GHRRC: Gamma Heating in Research Reactor Cores) is applied for the Greek Research Reactor (GRR-1) core. The required microscopic cross-sections and the three-dimensional neutron flux are obtained with the neutronics code system XSDRNPM and CITATION. The macroscopic cross-sections of the U235 fission and the (n, γ) reactions in the core materials are determined assuming a homogenized core. Comparisons of the computed gamma heating power deposited on a Fe sample with in-pile and out of pile measurements of the sample temperature show that GHRRC gives reasonable estimations. GHRRC may easily be handled even by poorly experienced users.