Damage assessment in case of cable fire in nuclear facilities considering damage criteria for each material type

Various types of flame retardant cable are used in nuclear power plants. The cable insulation and sheath materials are generally categorized into two types: thermosetting( TS) and thermoplastic( TP) materials. Domestic cable fire damage criteria are set for each material type on the basis of the US guidelines, although they do not clearly define which type a TS/TP composite cable falls into. In this study, cable burning tests were conducted for TP and TS/TP composite cables used in domestic nuclear power plants to evaluate the validity of applying the US cable damage criteria to domestic cables. For varions cable damage scenarios, the tests measured the temperature/time dependence of insulation resistance between conductors and between cable and trays. The results of these tests justified the applicability of the US damage criteria. In addition, it was confirmed that the relationship between cable temperature and insulation resistance can be expressed by an Arrhenius plot. These findings are expected to be utilized for the Safety Improvement Evaluation periodically conducted by nuclear facility operators. © 2020 Atomic Energy Society of Japan, All Rights Reserved.