Reliability aspect of diagnostics method of cable insulation for LWRs

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 from JNES report. Importance of nondestructive test performance was concluded. (author)