2019 年 18 巻 4 号 p. 237-245
The development of fabrication and inspection technologies for an oxidation-resistant fuel element was conducted referring to previous research to improve the safety of high-temperature gas-cooled reactors (HTGRs) during a severe oxidation accident. Herein, simulated coated fuel particles (CFPs), alumina particles, were coated with a mixture of Si and C powders and a small amount of resin to form “over-coated” particles that were subsequently molded and hot-pressed to sinter the simulated oxidation-resistant fuel elements with a SiC/C mixed matrix. SiC was formed by reaction bonding. Simulated oxidation-resistant fuel elements containing a matrix with a Si/C mole ratio of 1.00 were fabricated. Elemental Si and C peaks were not detected in X-ray diffraction of the matrix. The failure fraction of CFPs in fuel elements is a very important HTGR fuel inspection subject; it is essential that CFPs are extracted from fuel elements without additional failure. Herein, a method of extracting CFPs was developed. The dissolution of SiC using KOH or by pressurized acidolysis should be applied to extract CFPs. However, the outer high-density pyrolytic carbon layer should remain in spite of its transformation to SiC during sintering by reaction bonding with Si in the mixed powder.
