Managing Aging in Nuclear Powerplants

189 Pages·1993·16.568 MB·English

NU REG/CR-581 "_
/._,
BN L-N U REG-5 2309
I I II IIIIII IIIII II II ' L
Managing Aging in Nuclear
Power Plants: Insights From
NRC Maintenance Team
Inspection Reports
Prepared by
A. l;resc_, M. Subudhi, W. (}unthcr, t£. ()r_vc, J. 'ihyhu"
Brookhaven National Laboratory
Prepared fi;r
U.S. Nuclear Regulatory Commission
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i I I
NUREG/CR-5812
BNL--NUREG-52309
irll
Managing Aging in Nuclear
Power Plants: Insights From
NRC Maintenance Team
Inspection Reports
IIII I
Manuscript Completed: August 1993
Date Published: December 1993
Prepared by
A. Fresco, M. Subudhi, W.Gunther, E. Grove, J. Taylor
S.K. Aggarwal, NRC Program Manager
Brookhaven National Laboratory
Upton, NY 11973
Prepared for DISCLAIMER
Divisionof Engineering
Office of Nuclear Regulatory Research
This report was prepared as an account of work sponsored by an agency of the United States
U.S. Nuclear Regulatory Commission
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ABSTRACT
A plant's maintenance program is the principal vehicle through which age-related degradation is
managed. From 1988 to 1991, the NRC evaluated the maintenance program of every nuclear power plant
in the United States. Forty-four out of a total of 67 of the reports issued on these in-depth team inspections
were reviewed for insights into the strengths and weaknesses of the programs as related to the need to
understand and manage the effects of aging on nuclear plant systems, structures, and components. Relevant
information was extracted from these inspection reports and sorted into several categories, including Specific
Aging Insights, Preventive Maintenance, Predictive Maintenance and Condition Monitoring, Post Maintenance
Testing, Failure Trending, Root Cause Analysis and Usage of Probabilistic Risk Assessment in the
Maintenance Process. Specific examples of inspection and monitoring techniques successfully used by utilities
to detect degradation due to aging have been identified.
The information also was sorted according to systems and components, including: Auxiliary
Feedwater, Main Feedwater, High Pressure Injection for both BWRs and PWRs, Service Water, Instrument
Air, and Emergency Diesel Generator Air Start Systems, and emergency diesel generators, electrical
components such as switchgear, breakers, relays, and motor control centers, motor operated valves and check
valves. This information was compared to insights gained from the Nuclear Plant Aging Research (NPAR)
Program. Attributes of plant maintenance programs where the NRC inspectors felt that improvement was
needed to properly address the aging issue also are discussed.
iii
CONTENTS
ABSTRACT ............................................. iii
EXECUTIVE SUMMARY ........................................... xi
ACKNOWLEDGEMENTS ........................................... xi i i
1.0 INTRODUCTION ............................................ 1-1
1.1 NRC Maintenance Policy and the Maintenance
Team Inspections (MTIs) .................................. 1-1
1.2 Goals of the Nuclear Plant Aging Research
(NPAR) Program with Respect to the MTI Reports .................. 1-2
2.0 DISCUSSION OF METHODOLOGY ................................ 2-1
2.1 Methodology of the NRC Maintenance Team Inspections ............... 2-1
2.2 Methodology of the Current Study ............................. 2-1
3.0 PROGRAMMATIC INSIGHTS ................................... 3-1
3.1 Specific Aging Management Insights ........................... 3-1
3.1.1 Qualitative Insights ................................. 3-1
3.1.2 Conclusions on Specific Aging Insights ..................... 3-3
3.2 Preventive Maintenance Insights .............................. 3-3
3.2.1 Qualitative Insights ................................. 3-4
3.2.2 Conclusions Concerning Preventive Maintenance ............... 3-7
3.3 Predictive Maintenance and Condition Monitoring Insights .............. 3-8
3.3.1 Qualitative Insights ................................. 3-8
3.3.2 Conclusions for Predictive Maintenance and
Condition Monitoring ................................ 3-11
3.4 Post Maintenance Testing .................................. 3-12
3.4.1 Qualitative Insights ................................. 3-12
3.4.2 Conclusions on Post Maintenance Testing ................... 3-13
3.5 Failure Trending Analysis .................................. 3-13
3.5.1 Qualitative Insights ................................. 3-15
3.5.2 Comparison to NRC Findings .......................... 3-17
3.5.3 Conclusions for Failure Trending ........................ 3-17
CONTENTS (Cont'd)
3.6 Root CauseAnalysis ..................................... 3-17
3.6.1 Techniques of Root Cause Analysis ....................... 3-18
3.6.2 Qualitative Insights ................................. 3-19
3.6.3 Conclusions on Root Cause Analysis ...................... 3-20
3.6.4 Comparison to NRC Findings .......................... 3-21
3.7 Usage of Probabilistic Risk Assessment .......................... 3-21
4.0 INSIGHTS FOR SYSTEMS AND COMPONENTS ....................... 4-1
4.1 Systems ............................................. 4-1
4.1.1 Auxiliary Feedwater (AFW) ........................... 4-2
4.1.2 Feedwater Systems ................................. 4-4
4.1.3 High Pressure Injection Systems (HPIS) .................... 4-5
4.1.4 Service Water System ............................... 4-7
4.1.5 Instrument Air and Emergency Diesel Generator Air Start Systems
and Compressors .................................. 4-10
4.2 Components .......................................... 4-12
4.2.1 Emergency Diesel Generators ........................... 4-12
4.2.2 Electrical Components (Breakers, Switchgears, Relays, and
MCCs) ........................................ 4-15
4.2.3 Motor-Operated Valves (MOVs) ......................... 4-17
4.2.4 Check Valves .................................... 4-22
5.0 GENERAL SUMMARY AND CONCLUSIONS ......................... 5-1
5.1 Programmatic Areas ..................................... 5-1
5.1.1 Specific Aging Insights ............................... 5-1
5.1.2 Preventive Maintenance .............................. 5-1
5.1.3 Predictive Maintenance and ConditionMonitoring .............. 5-1
5.1.4 Post MaintenanceTesting ............................. 5-1
5.1.5 Failure Trending .................................. 5-2
5.1.6 Root Cause Analysis ................................ 5-2
5.1.7 Usage of ProbabilisticRisk Assessment ..................... 5-2
5.2 Systems and Components .................................. 5-2
5.2.1 Systems ........................................ 5-2
5.2.2 Components ..................................... 5-4
vi
CONTENTS (Cont'd)
Pa.P_a
5.3 CommentsConcerningtheNRC MaintenanceRule ................... 5-6
5.4 Final Comments ........................................ 5-6
6.0 REFERENCES ............................................. 6-1
APPENDIX A: CODING SCHEMEDEFINITIONS ......................... A-1
APPENDIX B: SAMPLE askSam OUTPUT FOR CALVERT
CLIFFS UNITS 1AND 2 ............................... B-1
APPENDIX C: QUANTITATIVE INSIGHTS OFINSIGHTS DERIVED FROM
MAINTENANCE TEAM INSPECTION REPORTS ............... C-1
APPENDIX D: SPECIFICEXAMPLES OF PROGRAMMATIC INSIGHTS FROM
MAINTENANCE TEAM INSPECTIONREPORTS ............... D-1
APPENDIX E: SPECIFICEXAMPLES OF INSIGHTS FOR SYSTEMS AND
COMPONENTSFROM MTIREPORTS ...................... E-1
vii
LIST OF FIGURES
Pa_s
2.I MaintenanceInspectionTree ..................................... 2-2
3.1 Trendingprogramfor managingaging ............................... 3-14
VIII""
LIST OF TABLES
1.1 List of Maintenance Team Inspection Reports Reviewed for Westinghouse
PWR Plants ............................................. 1-4
1.2 Listing of Maintenance Team Inspection Reports Reviewed for B&W and CE
PWR Plants ............................................. I-5
1.3 Listing of Maintenance Team Inspection Reports Reviewed for GE BWR Plants ...... 1-6
2.1 Correlation of Certain Maintenance Inspection Tree Elements with the
Management of Aging ......................................... 2-3
2.2 Categories of Information or Activities Important for the Management of Aging ...... 2-6
2.3 Categorization of Findings ....................................... 2-6
3.1 Typical Aging Problems in Nuclear Power Plant Components Identified in the
MTI Reports ............................................. 3-2
3.2 Examples of PM Activities (Noted in MTI Reports) ....................... 3-5
3.3 PM Frequency for Certain Equipment (as identified in the MTI Reports) .......... 3-6
3.4 Examples of Positive Failure Trending Findings .......................... 3-18
3.5 Some Examples of Components/Systems Considered for RCA Identified in the
MTI Reports ............................................. 3-21
4.1 Summary of Common Motor-Operated Valve Deficiencies, Misadjustments, and
Degraded Conditions (from NRC Generic Letter 89-10) ..................... 4-19
4.2 Selected Diagnostic Capabilities and Limitations of Check Valve Monitoring
Methods ............................................. 4-24
ix
EXECUTIVE SUMMARY
A plant's maintenance program is the principal vehicle through which age-related degradation is
managed. From 1988 to 1991, the NRC evaluated the maintenance program of every nuclear power plant
in the United States. The NRC issued 67 reports on these in-depth team inspections, one for each plant site.
Forty-four of these reports were selected and reviewed for insights into the strengths and we_dcnesses of the
programs as they relate to understanding and managing the effects of aging on nuclear power plant systems,
structures, and components. Relevant information was extracted and sorted into several categories. Specific
examples of inspection and monitoring techniques successfully used by utilities to detect degradation due to
aging were identified. The information also was sorted according to a selected number of systems and
components. Attributes of plant maintenance programs where the NRC inspectors felt that improvement was
needed to properly address the aging issue also are discussed.
The NRC staff assessed the maintenance programs at every nuclear power plant site in the country.
As a result, a large database of maintenance-related information was made available which, upon extraction
and reorganization, could be presented to those individuals concerned with managing aging-related degradation
of nuclear power plant systems and components. The database lends itself more to qualitative rather than
quantitative evz,luation; thus, the focus of this report is on providing primarily qualitative assessments of the
effectiveness of the programmatic activities, and also onthe effectiveness of those programmatic activities with
respect to selected systems and components. A quantitative assessment showed no apparent correlation with
plant age.
Six broad programmatic categories were focussed upon as essential activities to address the
management of aging:
* Specific Aging Insights
o Preventive Maintenance
e Predictive Maintenance and Condition Monitoring
• Post-Maintenance Testing
• Failure Trending
• Root Cause Analysis
A seventh category, Usage of Probabilistic Risk Assessment (PRA) in the Maintenance Process, was
chosen to examine the extent to which time-dependent failure rates for system components have been used by
the utilities in the modeling of plant-specific PRAs.
Inaddition to the seven programmatic categories, the database also was cross-sorted by specific plant
systems and components. The systems chosen are:
. Auxiliary Feedwater
• Feedwater
. High Pressure Injection
• Service Water
• Instrument Air and Emergency Diesel Generator Air Start Systems and Compressors
xi