Events related to emergency diesel generators in the nuclear industry: Analysis of lessons learned from the operating experience

• Analysis of operating experience for the past twenty years.
• Identifying events that involved failures of EDGs or its supporting systems in NPPs.
• Compiling categorized lessons learned based on specific EDG-related failures.
• Designating generic recommendations intended to tackle the identified EDG failures.

This study focuses on specific operating experience related to emergency diesel generators (EDG) at nuclear power plants. The study aims at analysing operating experience for the past twenty years and identifying events that involved failures of EDG or its supporting systems.The selected operating experience was analysed in order to identify type of failures, attributes that contributed to the failure, failure modes, discuss risk relevance, summarize important lessons learned and provide recommendations. For the purpose of this study EDG failure is defined as EDG fail to function on demand (i.e. fail to start, fail to run) or during testing, or an unavailability of an EDG, except of unavailability due to regular maintenance.The Gesellschaft für Anlagen und Reaktorsicherheit mbH (GRS) and Institut de Radioprotection et de Sûreté Nucléaire (IRSN) databases were screened to select all the events between 1990 and 2010 related to this topic. Besides IRSN and GRS operating experience, the operating experience contained in the IAEA/NEA International Reporting System for Operating Experience as well as the U.S. Licensee Event Reports were also analysed.The selected events were analysed in depth. Causes, root causes, contributing factors, consequences and lessons learned were determined. The events were classified into categories in order to establish main conclusions on the topic. A trend analysis was performed wherever possible, by assigning the reported events into different categories regarding chronology of occurrence, failure types, components involved, failure mode, failure causes, failure detection, etc. Subsequently, generic recommendations related with the analysed EDG failures were compiled.The focus of this paper is on the lessons learned from the analysed operating experience as well as on designating generic recommendations for the specific EDG-related issues encountered rather than presenting selected statistical results.