Microstructures and positron annihilation spectroscopy of nearly stoichiometric ZrC coating layers for advanced high-temperature gas-cooled reactor fuel

Aihara, Jun ; Maekawa, Masaki; Ueta, Shohei   ; Kawasuso, Atsuo; Sawa, Kazuhiro

Japan Atomic Energy Agency has started to study and develop zirconium carbide (ZrC)-coated fuel particles for advanced high temperature gas-cooled reactors. The ZrC coated particles have been fabricated at JAEA by bromide process and heat treated to investigate the effects of the sintering process of fuel compact. The remarkable ZrC crystal grain growth occurred in a batch (F-batch) but not another batch (G-batch) in spite of the same C/Zr ratio and ZrC density. TEM/STEM observation of the specimens before heat treatment clarified that much more free carbons or voids were distributed in ZrC layer in G-batch than F-batch. The difference between F- and G-batch, which could not be detected by the estimation of C/Zr ratio and the ZrC density, could be detected with positron annihilation spectroscopy (PAS). Then PAS might be suitable for the quality control method of the ZrC coated fuel particles. Characterization of the defects detected with PAS would be the next step.