Aging of Power Cables in Nuclear Power Plant due to Influence of Local Temperature Conditions

Abstract

A significant number of operating nuclear power plants (NPP) is approaching the end of the initially estimated design life. Considering that plants are stable and competitive, it may be possible to extend design lives to 60 years (perhaps even longer). Before expending life time, ageing in NPPs must be effectively managed to ensure the availability of design functions throughout the plant service life. From the safety perspective, this means controlling ageing degradation and wear-out within acceptable safety limits so that adequate safety margins remain, i.e. integrity and functional capability in excess of normal operating requirements. Even though cables are not active component, they are vital components in NPPs since they link the system components with instruments and control equipment used to monitor and control the plant. Consequently, the functionality of the cable necessary for nuclear safety is necessity for ensuring the functionality of equipment relevant to nuclear safety. Since the cable ageing have been recognized as potential threat to safe operation of NPP, this paper deals with cable ageing aimed at identifying effects of aging and to determine whether the degradation caused by aging is within the stipulated tolerance limits. Also, it analyses the impact of ambient temperature changes on the cable ageing comparing to a qualified life. For an illustration, Arrhenius’s model was used to calculate cable ageing in hot spot with the increased local temperature.