Superposition of Time-dependent Data for Accelerated Aging of Nuclear Power Plant Cables and Its Validity

Ohki, Yoshimichi; Hirai, Naoshi; Okada, Sohei

doi:10.23919/cmd54214.2022.9991591

Cited by 2 publications

(3 citation statements)

References 18 publications

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“…It probably does not contain pigments or additives necessary for cable manufacturing. As reported in [22,23], the 60 Co gamma‐ray irradiation at a rate of 100 Gy/h at 100°C to D0 has been known to make the condition of D0 equivalent to that of A1 and C1, when irradiated for 1997 and 1289 h, respectively. With this regard, the sheet was irradiated with gamma rays at a rate of 100 Gy/h at 100°C for the periods of 100, 1200, and 2000 h. Then, the leakage current flowing through the sheet was measured upon the application of a DC voltage in the same manner as in the previous section.…”

Section: Discussion I: Leakage Currents In Sheet Samplesmentioning

confidence: 99%

“…Similarly, the aging of cable C1 for 12.0 years at 58 • C corresponds to 271, 111, and 24 h of aging at 175, 200, and 250 • C, respectively. Here, to simulate the degradation that cables would have suffered over time in a nuclear environment, the method called the superposition of time-dependent data [22,30,31] has been used widely. The same artificial thermal aging periods can be obtained by this method, confirming the validity of the above calculations.…”

Section: Discussion Ii: Leakage Currents In Harvested Cables A1 and C1mentioning

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].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

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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.

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Section: Discussion I: Leakage Currents In Sheet Samplesmentioning

confidence: 99%

Section: Discussion Ii: Leakage Currents In Harvested Cables A1 and C1mentioning

confidence: 99%