Thickness Measurement of Coating layers of Simulated TRISO-Coated Particles by X-ray Radiography under an IAEA CRP Program

The TRISO-coated fuel particle for a HTGR(high temperature gas-cooled reactor) is composed of a nuclear fuel kernel and outer coating layers. The coating layers consist of a buffer PyC(pyrolytic carbon), inner PyC(I-PyC), SiC, and outer PyC(O-PyC) layer. The coating thickness is measured to evaluate the soundness of the coating layers. X-ray radiography is one of the nondestructive alternatives to measure a coating thickness without generating a radioactive waste. Phase contrast X-ray radiography technology is more powerful for acquiring a radiography image with clear boundaries between coating layers, when compared with the conventional X-ray radiography. In this experiment, the SiC specimens and the O-PyC specimens of 4 kinds of simulated TRISO-coated particles with ZrO2 kernel were measured by the phase contrast X-ray radiography under the IAEA CRP-6 (coordinated research project 6) program for characterizing TRISO-coated fuel particles for HTGR through the round robin tests with 4 different samples distributed from 4 member organizations to the 9 participating organizations