Current Integration Method as a Reliable Tool for Diagnosing Flame-retardant EPDM Cables Removed from Nuclear Power Plants

Ohki, Yoshimichi; Hirai, Naoshi; Sato, Kosuke; Tanaka, Yasuhiro

doi:10.23919/cmd54214.2022.9991407

Cited by 2 publications

(2 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: Introductionmentioning

confidence: 99%

“…In addition, the insulation degradation of low-voltage cables insulated with FR-EPDM, removed from NPPs, was investigated [20][21][22][23]. As a result, it has become clear that the electrical resistance of the insulation is significantly higher in cables removed after many years of installation in NPPs than that of an unused new cable [20,21]. This paper discusses the reason for the high electrical resistance measured in the harvested cables mainly by referring to typical related experimental results acquired by us for sheet samples of the same FR-EPDM [9,10].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reasons for Resistivity Increase in FR‐EPDM Insulation of Cables Aged in Nuclear Power Plants

Ohki

Hirai

Sato

et al. 2023

IEEJ Transactions Elec Engng

View full text Add to dashboard Cite

Two low-voltage cables, insulated with flame-retardant ethylene-propylene-diene rubber (FR-EPDM), were removed after being laid in nuclear power plants for many years. We measured the leakage currents flowing through their insulators and found that the resistivity of cable insulation is higher in the two harvested cables than in a similar but new and unused FR-EPDM one. The reason for this result is discussed in this paper based on a comparison of the leakage currents between new and gamma-ray irradiated FR-EPDM sheets. The discussion is continued by referring to our previous papers on mechanical properties and infrared absorption spectra of similar new and gamma-ray irradiated FR-EPDM sheets. As a result, it has been clarified that additives such as pigments contained in the cable insulators are likely to act as a source of charge carriers. In addition, the cable insulators became hardened by the long-term aging in an environment of about 60 • C, which made the ionic conduction difficult and the insulation resistivity higher.

show abstract