Prognosis of wear-out effect on of safety equipment reliability for nuclear power plants long-term safe operation

Abstract

To reach a Net Zero Emission scenario, on 1st January 2022 the European Union (EU) declared nuclear and gas as transitional activities under strict safety conditions. A central challenge is that many nuclear reactors in operation are close to or have reached their design life, so that, it is required to demonstrate the influence of equipment ageing on plant reliability will be kept under control in the plan extended lifetime. In this work a three-step methodology is proposed to obtain the time instants at which the failure rate behaviour changes (break points) and the most appropriate age-dependant reliability model to explicitly include the effects of ageing and maintenance. The methodology requires the reliability parameters estimation at each phase of the plant equipment lifetime, what is carried out by using the available Nuclear Power Plant (NPP) historical data, which is quite scarce. The methodology is applied to a motor operated valve of a NPP safety system. The results demonstrate the capability of the approach proposed to estimate and predict the component reliability in the plant extended lifetime depending on the maintenance policy implemented, being necessary to estimate an accurate age-dependant reliability model to support the decision-making process on equipment ageing management.