Feasibility study of spectroscopy of low-volatile FPs for special nuclear material accountancy in molten core material

Sagara, Hiroshi; Tomikawa, Hirofumi; Watahiki, Masaru; Kuno, Yusuke

Reviewing the technologies applied to TMI-2, feasibility study of spectroscopy of low-volatile FPs for special nuclear material accountancy in molten core material or debris has been performed numerically, and the sensitivity of low-volatile FP nuclides on fuel contents, especially Pu, was studied with parameters of typical BWR fuel such as enrichment, burnup and neutron spectrum, heat density. Comparing TMI-2, a PWR reactor, broader neutron spectrum axial profile and irradiation cycle complexity of typical BWR fuel assemblies make more variance in the accumulation of daughter nuclides by neutron capture reactions. As results, Pu quantification, by burnup dependent Eu/Pu index has accuracy of 15-18% in 1-sigma level mainly affected by burnup uncertainty, and Pu quantification by Ce/Pu has accuracy of 20% as long as Ce released photon could be observed within 10 years, within the scope of inventory survey except for measurement uncertainty. Finally systematic image of fuel quantification by passive spectroscopy and, as future study, FPs quantification by passive measurement tests by mockup debris measurement with self-attenuation correction are introduced.