UO2-BASED ACCIDENT-TOLERANT HYBRID FUEL: A COMPARATIVE STUDY OF HIGH THERMAL CONDUCTIVITY ADDITIVES

Abstract

Lower fuel temperature than conventional pressurized water reactors (PWR) is strongly preferred for Autonomous, Transportable, On-demand reactor-Module (ATOM), an innovative small modular PWR concept under initial development phase in the Republic of Korea for the incoming six years. The conceptual design and material feasibility test of high thermal conductivity hybrid oxide fuel is thus an essential course of the development of the ATOM. Among a few additive candidates, uranium sesquisilicide(U3Si2) has been selected mainly due to high fissile density, high thermal conductivity, and acceptable chemical stability. This study first examined the fabricability of UO2-U3Si2 hybrid fuel using surrogate materials, CeO2 and Ce3Si2. Metallurgical and thermophysical characterizations of micro-wave sintered pellets of CeO2-20%Ce3Si2 using SEM-EDS, XRD, and DSC suggested the formation of Ce5Si3 during high energy ball mill (HEBM) process for Ce3Si2 powder production. Achieved highest fractional density of the hybrid ceramic was ~87%TD and enhanced thermal conductivity was experimentally confirmed using LFA, which was comparable with that of 95%TD CeO2 up to 500 °C