Development of fabrication technology for oxidation-resistant fuel elements for high-temperature gas-cooled reactors

Japan Atomic Energy Agency (JAEA) has developed fabrication technology for oxidation-resistant fuel elements to improve the safety of high-temperature gas-cooled reactors in severe oxidation accidents on the basis of its previous research. Simulated fuel particles (alumina particles) were coated with a mixed powder of Si, C and a small amount of resin to form over-coated particles, which were molded and sintered by hot-pressing to form simulated oxidation-resistant fuel elements with a SiC/C mixed matrix, where the SiC was formed by reaction bonding. Simulated oxidation-resistant fuel elements with a matrix whose Si/C mole ratio (about 0.551) was three times as large as that in previous research were fabricated. No Si peak was detected by X-ray diffraction of the matrix. A monoaxial compressive fracture test was carried out, and the fracture stress was found to be more than three times as large as the standard for fuel compacts of High Temperature Engineering Test Reactor (HTTR). Better oxidation resistance than that of an ordinary fuel compact with a ordinary graphite matrix was confirmed by an oxidation test in 20% O₂ at 1673 K. All simulated coated fuel particles remained in specimen after 10 h oxidation. (author)