Feasibility study on TRISO fuel particles for efficient Pu incineration and 3S features enhancement in HTGR

Due to international concerns for the large amount of separated plutonium (Pu) and Pu in spent fuel owned by Japan, rapid Pu incineration, aiming for its direct disposal with attention to safety, security, and safeguards/non-proliferation (3S) issues, will give us one of the important options to nuclear policy-making. A feasibility study was performed to investigate the efficient Pu incineration and the enhancement of 3S features using tri-isotropic coated (TRISO) fuel particles with transuranic (TRU) oxide recovered from light water reactor (LWR) spent fuel in high temperature gas cooled reactors (HTGRs). Neutron transport with burn-up calculations for cell model revealed the Pu incineration ratios, burnup reactivity fluctuations, and fuel temperature coefficients were improved by diluting the inert-matrix-fuel (IMF) kernel and optimizing the neutron spectrum to mitigate the self-shielding effect of 240Pu. The fuel and moderator temperature coefficients were equivalent to those of conventional HTGR. Nuclear security and non-proliferation features of nuclear materials in fuel fabrication facility, fresh and spent fuel storages were relatively assessed based on the material’s physical properties among four levels in each of three discrete phases in the development of a nuclear explosive device. The nuclear security assessment was based on theft and diversion to a final Pu metal form; the assessment revealed that the non-irradiated TRISO fuel particle and IMF kernel and the non-irradiated mixed oxide fuel (MOX) powder in a MOX fueled LWR were the most vulnerable targets in their respective flows. The chemically stable TRISO fuel particle and IMF kernel would have less “material attractiveness” than the MOX powder because of their greater processing time and complexity. Furthermore, these materials still have less “material attractiveness” at a 10% Pu extraction rate. The non-proliferation assessments assumed concealed diversion and revealed the TRISO fuel particle and IMF kernel have less “material attractiveness” than the MOX powder due to their greater processing time and complexity.