Seismic evaluation of electrical and instrumentation systems. Backfit actions being carried out at Trino Vercellese nuclear power plant

A special program has been set up for the seismic qualification of the electrical and instrumentation safety related systems at Trino Vercellese nuclear power plant. The intent of this paper is to describe the problems connected to the seismic qualification of operating plants and to present a viable and cost effective approach to the solution. An example of a practical application is included. It shows how the operability of the equipment following a seismic event based on a similarity method can be demonstrated. (author)