Condition assessment of installed nuclear power plant (I and C) cables

Twenty-five to thirty-five year old nuclear power plants are undergoing rehabilitation programs to extend the plant life to 50 or 60 years. Instrumentation and control (I and C) cables are identified as one of the major components examined in the life extension programs. Cable insulation is exposed to ionizing radiation, elevated thermal, vibration, and moist environments during normal operation in addition to extra ordinary radiation and thermal conditions in a postulated design basis accident event. Aged insulations are prone to either embrittlement and cracking or an alteration in material chemistry causing changes in dielectric properties which leads to shorting when moisture is present. This presentation discusses the techniques used to perform a condition assessment of cable insulation by means of visual and other non destructive techniques, namely, EPRI Indenter measurements and near infrared (NIR) scanning technology. Low voltage installed cables which are insulated with PVC, FRXLPE, and FREPR, and which are jacketed with PVC, are considered. The techniques discussed will allow plant personnel to extend cable life without additional qualification tests. (author)