Component unavailability model for PSA Level I applications considering aging and startup degradation: An Application to an Emergency Diesel Generator System

The paper proposes an unavailability model, which considers standby component degradation due to repeated startups, including not only planned surveillance tests, but also additional startups due to real demands and, in cases when the component is detected failed in the planned test, extra tests related to corrective maintenance. The model is applied to evaluate the effect of additional tests on Emergency Diesel Generators from a Nuclear Power Plant’s Onsite Power System. These additional tests are not considered in traditional reliability models. The results show that excessive Diesel Generator testing during its working life may lead to a significant increase of component unavailability with reflections on the core damage frequency at the end of its overhaul maintenance period. This increment could justify anticipation of Diesel Generator overhaul maintenance in one or two working cycles.