Neutronic analysis of subcritical assembly for 99Mo isotope production based on thorium nitrate fuel

Abstract

The paper discusses a neutronic analysis of the SAMOP reactor based on thorium nitrate as fuel and target materials. The reactor core model consists of an annular cylindrical tube with a tube in the center, filled with thorium nitrate as fuel. The analysis is done for the variation of fuel enrichment, the first case use thorium nitrate with 16% 233U enrichment both on the annulus and the center of the core, and the second use 10% 233U enrichment in the annulus and 14% enrichment in the center. The methods used for this analysis is a modelling calculation using MCNPX computer code. The analysis results show that the neutron multiplication factor (kef) is 0,97706 ± 0,00250 with conversion ratio (CR) of 0.1175 and keff = 0,98113 ± 0,00216 with CR = 0,1704, for the first and second case respectively. The need of 233U for the first case and the second case are 1.448 kg and 4.383 kg, respectively. The results show that the sub-criticality requirement (keff < 1) for both cases was achieved, but from the fuel utilization, the first case is more efficient. Based on the CR values the SAMOP cannot be categorized as a breeder reactor.