高温ガス炉用耐酸化燃料要素の製造技術開発

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

相原 純 ; 本田 真樹*; 植田 祥平   ; 小河 浩晃  ; 大平 幸一*; 橘 幸男 

Aihara, Jun; Honda, Masaki*; Ueta, Shohei; Ogawa, Hiroaki; Ohira, Koichi*; Tachibana, Yukio

原子力機構は深刻な酸化事故時の高温ガス炉の安全性向上のため、日本原子力研究所(現・原子力機構)で行われた先行研究に基づき耐酸化燃料要素の製造技術開発を行った。模擬被覆燃料粒子(アルミナ粒子)をSi及びC及び少量の樹脂の混合粉末でオーバーコートし、型に詰めて熱間加圧しSiC/C混合母材を持つ耐酸化燃料要素(模擬)を焼成した。母材のSi/C比が先行研究の3倍(約0.551)である耐酸化燃料要素(模擬)を試作し、母材のX線回折を行ったところSiのピークは検出されなかった。一軸圧縮破壊応力は高温工学試験研究炉(HTTR)の規格の3倍以上と評価された。20%酸素中1673Kで10h酸化試験させたところ全ての模擬被覆燃料粒子が保持されており、従来の黒鉛/炭素母材を持つ通常の燃料コンパクトよりも優れた耐酸化性が確認された。

Japan Atomic Energy Agency carried out development of fabrication technology of oxidation resistant fuel element for improvement of safety of high temperature gas-cooled reactors in serious oxidation accident, based on precursor research in former JAEA. Dummy coated fuel particles (alumina particles) were over-coated with mixed powder of Si, C and small amount of resin to form over-coated particles, and over-coated particles were molded and hot-pressed to sinter dummy oxidation resistant fuel elements with SiC/C mixed matrix. We fabricated dummy oxidation resistant fuel elements with matrix whose Si/C mole ratio (about 0.551) is three times as large as that in precursor research. Si peak was not detected by X-ray diffraction of matrix. Better oxidation resistant was confirmed with oxidation test in 20% O at 1673 K than that of ordinal fuel compact with ordinal graphite/carbon matrix. All dummy coated fuel particles were held in specimen after 10 h oxidation.