低圧ケーブル絶縁劣化診断法の信頼性検討

Reliability aspect of diagnostics method of cable insulation for LWRs

渡士 克己

Watashi, Katsumi

冷却材喪失事故のような過酷な環境下で、それまで定常運転状態で放射線下・空気環境下で長時間使用されてきた安全系低圧ケーブルが、絶縁を維持して信号を伝達できるかどうかは、安全上の関心事である。このような評価を行うために、経年化炉の安全系低圧ケーブルの絶縁劣化の評価方法は、原子力安全基盤機構によって研究プロジェクトが展開され、報告書としてまとめられている。本報では、今後も経年化炉で使用される可能性の高いケーブルについて、当該評価方法の信頼性をAPI-RBM的方法で改良一次近似二次モーメント法を応用して検討した結果を示す。

The insulation degradation can be appeared in cables which were installed at radiation and air environment in aged LWRs. It is implicated that the behavior is related to decrease of an antioxidant among the stabilizers which was caused by thermal oxidation and radiation induced oxidation. JNES has prepared a diagnostics method of insulation degradation for safety related low voltage cable used in aged LWRs. This paper shows a degradation indicator, for which nondestructive test and, then, probability of insulation degradation. A reliability analysis method applied in the paper is based on level 2 reliability analysis method. A degradation master curve, critical values of the indicator and the nondestructive test performance were referred form JNES report. Importance of nondestructive test performance was concluded.