New method for detecting degradation in installed cables in nuclear power plants

Simple and precise methods for detecting degradation in installed cables in nuclear power plants are expected to develop from the viewpoint of the safety operation and the life extension of the plants. Generally, the degradation of cable insulation by thermal and/or radiation aging has been examined by tensile tests, and the degree of degradation was evaluated from the ultimate strength and elongation. The degradation of cables installed in the facility is likely to be detected by non-destructive techniques. For this purpose, two kinds of detecting methods i.e., (a) torque-strain response and (b) thermal gravimetry were studied in order to apply to the low voltage cables, for which effective detecting methods have not been completed. The paper describes a basic idea to determine degradation of the low voltage CV-cables (polyethylene insulation, polyvinylchloride jacket). Elongation at break was used as a primary standard to evaluate availability of the methods