Development of Fabrication and Inspection Technologies for Oxidation-Resistant Fuel Element for High-Temperature Gas-Cooled Reactors

Abstract

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.

A statistical approach for modelling the effect of hot press conditions on the mechanical strength properties of HTGR fuel elements

“…the SiC and carbon (C) mixture matrix by the reaction sintering of silicon (Si) and C powders in Japan (Ikawa et al, 1978) (Ikawa et al, 1977) (Aihara et al, 2019a) (Aihara et al, 2019b).…”