NUREG/CR-68 19, Vol. 1 INEEL/EXT-99-006 13 Common-Cause Failure Event Insights Emergency Diesel Generators Idaho National Engineering and Environmental Laboratory U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research ,,,g, Washington, DC 20555-0001 AVAILABIUTY OF REFERENCE MATERIALS IN NRC PUBLICATIONS NRC Reference Material Non-NRC Reference Material As of November 1999, you may electronically access Documents available from public and special technical NUREG-series publications and other NRC records at libraries include all open literature items, such as NRC's Public Electronic Reading Room at books, journal articles, and transacUons, Federal htto://www.nrc.aov/readina-rm.html. Publicly released Register notces, Federal and State legislaton, and records include, to name a few, NUREG-series congressional reports. 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(NUREG-0750). DISCLAIMER: This report was prepared as an account of work sponsored by an agency of the U.S. Govemment. Neither the U.S. Govemment nor any agency thereof, nor any employee, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, apparatus, product, or process disclosed in this publicaton, or represents that its use by such third party would not infringe privately owned rights. NUREG/CR-6819, Vol. 1 INEEL/EXT-99-00613 Common-Cause Failure Event Insights Emergency Diesel Generators Manuscript Completed: March 2003 Date Published: May 2003 Prepared by T. E. Wierman, INEEL D. M. Rasmuson, NRC N. B. Stockton, INEEL Idaho National Engineering and Environmental Laboratory Idaho Falls, ID 83415 T.R Wolf, NRC Project Manager Prepared for Division of Risk Analysis and Applications Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 NRC Job Code Y6194 ABSTRACT This report documents a study performed on the set of common-cause failures (CCF) of emergency diesel generators (EDG) from 1980 to 2000. The data studied here were derived from the NRC CCF database, which is based on US commercial nuclear power plant event data. Ihis report is the result of an in- depth review of the EDO CCF data and presents several insights about the EDO CCF data. The objective of this document is to look beyond the CCF parameter estimates that can be obtained from the CCF data, to gain further understanding of why CCF events occur and what measures may be taken to prevent, or at least mitigate the effect of, EDG CCF events. This report presents quantitative presentation of the EDG CCF data and discussion of some engineering aspects of the EDG events. iii CONTENTS Abstract ............ iii Executive Summary .............. xiii Foreword ............. xvii Acknowledgements .. ............ xix Acronyms ................. xxi Glossary ... .. .xxiii 1. Introduction...1 1.1 Background .1 1.2 Common-Cause Failure Event Concepts .2 1.3 Report Structure .5 2. Component Description . .7 2.1 Introduction .7 2.2 Risk Significance .7 2.3 Component Description and Boundary .7 2.4 Sub-System Description .. 2.4.1 Battery 8 2.4.2 Combustion Air .8 2.4.3 Cooling .................... 8 2.4.4 Engine .9 2.4.5 Exhaust .9 2.4.6 Fuel Oil .9 2.4.7 Generator .9 2.4.8 Instrumentation and Control . 9 2.4.9 Lubrication Oil .9 2.4.10 Output Circuit Breaker .10 2.4.11 Starting Air ...... 10 2.5 Failure Modes .10 3. High Level Overview Of Emergency Diesel Generator Insights ........................................... 13 3.1 Introduction .13 3.2 CCF Trends Overview .14 v 3.3 CCF Sub-System Overview ...................... 17 3.4 CCFProximate Cause ...................... 17 3.5 CCF Coupling Factors ...................... 20 3.6 CCF Discovery Method Overview ...................... 22 3.7 Other EDG CCF Observations ...................... 23 4. Engineering Insights By Emergency Diesel Generator Sub-System ............................................. 27 4.1 ntroduction .................. 27 4.2 Instrumentation and Control .................. 29 4.3 Engine .................. 33 4.4 Fuel Oil .................. 36 4.5 Generator .................. 39 4.6 Cooling .................. 41 4.7 Starting Air .................. 44 4.8 Output Circuit Breaker .................. 47 4.9 Lube Oil .................. 49 4.10 Exhaust ........................................ 49 4.11 Battery ....................................... 50 5. Insights from EDG foreign Experience ........................................ 51 5.1 International Common-cause Data Exchange Project ............... ........................ 51 5.2 Scope of the EDG Event Collection ........................................ 51 5.3 Summary of European Events ........................................ 51 5.4 Comparison of USA and European Experience ....................................... 52 6. How To Obtain More Detailed Information ....................................... 59 7. References ......................................... 61 vi Appendix A D Summaryata .................... A-1 Appendix B Data Summary by Sub-System ................... B-i vii FIGURES Figure ES-1. Trend for all EDG CCF events. The decreasing trend is statistically significant with a p-value = 0.0001 ................................................................. xiv Figure ES-2. Proximate cause distribution for all EDG CCF events ................................................. xv Figure ES-3. Distribution of EDG events by the affected sub-system .. .......................................... xv Figure 2-1. Emergency diesel generator component boundaries ......................................................... 8 Figure 3-1. Trend for all EDG CCF events. The decreasing trend is statistically significant with a p-value = 0.0001 ................................................................. 14 Figure 3-2. Trend for Complete EDG CCF events. The decreasing trend is statistically significant with a p-value = 0.0001. The trend from 1985-2000 is not statistically significant (p-value 0.4874) ................................................................. 15 Figure 3-3. Trend for all EDG CCF events for the fail-to-start failure mode. The decreasing trend is statistically significant with a p-value = 0.0001 .......................................................... 15 Figure 3-4. Trend for all EDG CCF events for the fail-to-run failure mode. The decreasing trend is statistically significant with a p-value = 0.0001 .......................................................... 16 Figure 3-5. Sub-system distribution for all EDG CCF events ........................................................... 17 Figure 3-6. Proximate