Development of high temperature gas-cooled reactor fuel for extended burnup

高燃焼度用高温ガス炉燃料の開発

植田 祥平   ; 相原 純 ; 本田 真樹*; 降旗 昇*; 沢 和弘

Ueta, Shohei; Aihara, Jun; Honda, Masaki*; Furihata, Noboru*; Sawa, Kazuhiro

超高温ガス炉(VHTR)燃料においては、HTTRの3.6%FIMAより遥かに大きな燃焼度(1520%FIMA)まで安全性を保つ必要がある。TRISO燃料の健全性を高燃焼度まで保つためには、機械的強度向上と内圧上昇緩和のために、SiC層とバッファ層を厚くする必要がある。原子力機構においては、過去に高燃焼度用燃料を開発し、9%FIMAまでの性能を確認した。今回の研究開発においては、新たに高燃焼度用燃料を製造した。真球度その他によって示されるように、この新しい燃料の品質は過去の燃料よりも高品質であった。

Very High Temperature Reactor (VHTR) fuel is required to have excellent safety performance up to burnups of about 15 to 20% fissions per initial metal atom (FIMA), how are higher than the design of the Japanese HTTR fuel, 3.6% FIMA. In order to keep the integrity of TRISO fuel against the internal pressure increasing according to burnup, the SiC and the buffer layers should be designed to be thick, enough to increase the mechanical strength and to moderate the internal pressure in TRISO fuel, respectively. So far JAEA developed so-called extended burnup fuels whose target burnup was higher than those of the HTTR, and confirmed their performance by irradiation tests up to 9% FIMA. In this R&D, the new TRISO fuel designed for further extended burnup were fabricated. Indicated by the sphericity of the particle and so on, the quality of the new fuel resulted better than the past fuel for extended burnup.