A STUDY OF NUCLEAR POWER PLANT EVENTS THAT INVOLVE INSTRUMENTATION AND CONTROL SYSTEMS 1

The Accident Sequence Precursor(ASP) database and the Licensee Event Report(LER) database provide a snapshot of instrumentation and control(IC starting in 1994. The LER study placed LERs in three categories: hardware, software, and human!system interface(HSI). Analysis showed an even distribution of events in each of the categories. The analysis also showed that approximately 9% of all LERs, from 1994 to 1999, contain digital I&C failures, and 9% of reactor trips for those years are attributed to digital I&C failures. Both database studies show that I&C systems, particularly those that are digital, have noticeable impact on nuclear power plant safety.