Evaluation of life by long hour deterioration test using radiation and heat for insulating materials of electric wires

From the viewpoint of securing the safety and extending the life of nuclear power stations, as for pressure vessels, concrete for living body shielding and electric wires which are largely related to plant life, it is desirable to establish deterioration diagnosis technology and the technology for estimating the remainder of life. The electric wires and cables for nuclear power stations are exposed to the environment of radiation and heat, 1 Gy/h and 50degC at maximum in PWRs and 0.5 Gy/h and 57degC on average in BWRs, in the normal operation for 40 years which is the approved life of nuclear power plants. In this study, the insulating materials used for the electric wires and cables for nuclear power stations were exposed to the combined environment of heat and radiation in wide range for long hours, and the deterioration was examined by using elongation as the index. Based on its data, the analysis by superposition method was carried out, and the estimation of life in the real environment was attempted. Two kinds of polyvinyl chloride were irradiated with Co-60 gamma ray at different temperature. The results are reported. (K.I.)