日本製高品質高温ガス炉燃料の破損率計算法の提案

抄録

  The Japan Atomic Energy Agency (JAEA) has carried out research and development of high-temperature gas-cooled reactors (HTGRs) since 1960s. The high-temperature engineering test reactor (HTTR) has attained full power in 2000. In this study, a failure probability calculation method for Japanese high-quality HTGR fuel particles is suggested for the design of Japanese HTGRs. Failure probability is strongly dependent on the irradiation characteristics of pyrolytic carbon (PyC) layers of HTGR fuel particles. However, it is very difficult to obtain new irradiation data of PyC layers with experiments. Therefore, in this study, we calculated failure probabilities using a report summarizing the irradiation data obtained at various irradiation temperatures of PyC layers with various as-fabricated characterisitics and the result of the failure probability measurement of the irradiation test of HTTR fuel. The characteristics of the coating layers of Japanese HTGR fuels, including future fuel types, would be very similar to those of HTTR fuel. In addition, some calculations were carried out with the suggested method. It was shown that the thickening of the SiC layer is more effective in reducing the failure probability than the thickening of the buffer layer. Thus, the thickening of the SiC layer is important for the modification of HTGR fuel for burnup extension, suppressing the increase in core volume.