Strength evaluation method of ZrC coating layer on TRISO particles using a crush test

TRISO coated fuel particle used in HTGR(High Temperature Gas-cooled Reactor) is composed of four layers of buffer PyC layer, inner PyC layer, SiC layer, and outer PyC layer coated on UO₂ kernel. SiC layer maintains the structural integrity of TRISO coated fuel particle at high temperature and retains fission products since its excellent high temperature mechanical properties. However, β-SiC deposited by CVD causes a phase change to α-SiC above 1800 .deg. C, which may cause damage to the TRISO coating layer. Since the SiC layer reacts with the fission product Pd to form Pd₂Si, which causes corrosion, resulting in a loss of ¹³⁷Cs trapping ability of TRISO coated fuel particle. As a result of FEA simulation using ZrC hemisphere shell with inner and buffer PyC layers, the maximum stress was applied to the ZrC layer. ZrC TRISO were fabricated by FBCD method. ZrC hemisphere shell were prepared by several treatments. In the load-displacement curves of ZrC hemisphere shell, a small load drop was observed when the ZrC coating layer was broken during crush test. From the fracture load, the strength value of ZrC coating layer was evaluated by using FEA simulation results.