Determination of the root cause of the serious incident at Paks NPP on 10 April, 2003

Abstract

A serious incident occurred at the Paks Nuclear Power Plant (NPP) on April 10, 2003, in the revision shaft next to Unit 2 that was shut down for scheduled overhaul. 30 fuel- assemblies were damaged and, although negligible in its extent concerning the environmental impact, radioactive material was released into the environment. The event was classified as INES-3 on the 7-level International Nuclear Event Scale. In accordance with the international requirements, the event was independently investigated by the Hungarian Nuclear Safety Authority and analyzed by the methodology of Root Cause Analysis (RCA) in order to determine the primary cause of the incident. This report summarizes the different techniques of RCA and it introduces the steps of investigation from data and information collection through identification of relevant occurrences and causal factors to the development of effective corrective and preventive measures. Root cause. The cause that, if corrected, would prevent recurrence of this and similar occurrences. The root cause does not apply to this occurrence only, but has generic implications to a broad group of possible occurrences, and it is the most fundamental aspect of the cause that can logically be identified and corrected.