An analysis of maintenance failures at a nuclear power plant

In this paper, a study of faults caused by maintenance activities is presen ted. The objective of the study was to draw conclusions on the unplanned ef fects of maintenance on nuclear power plant (NPP) safety and system availab ility. More than 4400 maintenance history reports from the years 1992-1994 of Olkiluoto BWR NPP were analysed together with the maintenance personnel. The human action induced faults were classified, e.g. according to their m ultiplicity and effects. This paper presents and discusses the results of a statistical analysis of the data. Instrumentation and electrical component s appeared to be especially prone to human failures. Many human failures we re found in safety related systems. Several failures also remained latent f rom outages to power operation. However, the safety significance of failure s was generally small. Modifications were an important source of multiple h uman failures. Plant maintenance data is a good source of human reliability data and it should be used more in the future. (C) 2001 Elsevier Science L td. All rights reserved.