Application of Implicit and Explicit Reliability Modelsfor Incorporating Ageing Effects

摘要

The PSA methodology as the most integrated evaluation methodology of plant and processrnsafety gives excellent opportunities for ageing safety and efficiency problems solving. One of the tasksrnof Ageing PSA is an incorporation of age-dependent reliability parameters and data of certain safety-relatedrnsystem, structure and components into the PSA model and interpretation of its results.rnThe paper presents application of the implicit GO-FLOW and the explicit ATRD dynamic systemrnreliability methods for incorporating ageing effects. Both approaches are used for preparation ofrncomparable ageing process component and system models of the safety system - three-train low-pressurernresidual heat removal and emergency core cooling system, and a normal operation system –rnoil system of main coolant pump of a Russian-design PWR WWER-1000. The possible extensions ofrnthese methods are compared with the equivalent FT models of these systems. Different ways torndescribe the age-related degradation and strength reduction for different categories of components andrnby different functions growing in time could be used – linear, one- or three-parametric Weibull ageingrnmodels. Alternative methodologies could be used to investigate the feasibility of increasing of failure,rnrestore and repair rates of all component categories or reducing the surveillance intervals of repairablerncomponents to take into account ageing processes in plant availability.