Degradation mechanisms of cable insulation materials during radiation-thermal ageing in radiation environment

ケーブル絶縁材料の放射線環境における放射線・熱劣化反応機構

瀬口 忠男*; 田村 清俊; 大島 武; 島田 明彦; 工藤 久明*

Seguchi, Tadao*; Tamura, Kiyotoshi; Oshima, Takeshi; Shimada, Akihiko; Kudo, Hisaaki*

原子力発電所のケーブル経年劣化における加速試験の劣化反応機構を解明する研究である。放射線と熱劣化の複合劣化において、加速倍率が高くなると酸化反応速度が不連続になる原因を究明した。微量安定剤である酸化防止剤の濃度が放射線で分解し、また、熱劣化では高分子から飛散することを見いだし、これが劣化速度不連続の要因であることを明らかにした。

The cables applied in radiation facility such as a nuclear power plant degrade by radiation and thermal combined ageing. The degradation of polymers for cable insulation is induced by oxidation, and the oxidation is accelerated by synergism of radiation and thermal oxidation. The degradation mechanisms were studied at accelerated degradation for various cable insulation materials. The distribution of degradation in film samples was investigated with various techniques. It was found that the antioxidant agent for stabilizer of insulation materials is closely related to the synergism. With progress of ageing, the concentration of effective antioxidant decreases by radiation decomposition and also by evaporation in thermal ageing. When the concentration of antioxidant is reduced to a limited value, the thermal oxidation is progressing.