Leakage control of HTGR fuel using a weak irradiation technique

Abstract

Radiation safety of high temperature gas-cooled reactors (HTGRs) largely depends on the leakage of fission products from the fuel under both normal and emergency modes of operation. Within the development of a pilot industrial fuel technology for an HTGR of the nuclear power engineering plant, we conducted pre-reactor tests of laboratory manufactured fuel to determine the leakage of fission products, as well as to assess the contamination of structural materials with uranium. Bulk TRISO particles, TRISO particle compacts, and blank graphite compacts were studied. The conducted tests used a weak irradiation technique developed by the NRC “Kurchatov Institute”. The technique is based on measuring the leakage of gaseous fission products from weakly irradiated samples during their annealing at temperatures close to the core temperature. A small dose of radiation causes no effect on the basic initial physical and chemical properties of fuel (density, porosity, etc.), as well as the ability to retain fission products. We analyzed the quality of laboratory-manufactured HTGR fuel by comparing the measured relative leakage of reference radionuclides with the established permissible limits, including individual technological stages of production. The study highlights the importance of the technique for quality control of HTGR fuel.