Year
2010
Abstract
KAERI has modified a previously developed passive neutron coincidence counting system for an active mode operation by adapting various interrogation sources, a neutron generator, a 252Cf isotope, and an Am-Li source, and has measured its performance with natural uranium oxide powder up to 27.9g of 235U. The objective of this study is to develop a neutron counter for fissile material accounting and to evaluate its applicability to a pyroprocess facility. For that reason, an experimental set-up based on simulation, measurement tests and an analysis of the results have been performed by using uranium samples. The experimental results showed an increment of neutron coincidence counting as the mass of the uranium samples as well as fair agreement with simulation results. The result of an active counting using a 252Cf showed a relatively lower error than other cases, but still not enough to measure small amount of fissile material in a large natural uranium sample mostly because of its high energy and inherent high background coincidence rate. It would be, however, applicable to an assay of more than 3 kg of uranium with a natural or higher enrichment level in an error range of 4 - 6 %. The experimental result using a single Am-Li source showed weaker coincidence signals due to its low intensity. Comparisons of sensitivities and errors are made are discussed while different interrogation sources (including a neutron generator) and different gate widths. More experimental approaches to investigate its applicability for pyroprocess materials and the results are described in detail.