ML20137A632
| ML20137A632 | |
| Person / Time | |
|---|---|
| Issue date: | 07/31/1985 |
| From: | Morris B, Vora J NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| References | |
| NUREG-1144, NUDOCS 8508210443 | |
| Download: ML20137A632 (48) | |
Text
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NUREG-1144 L'
Nuclear Plant Aging Research {NPAR?
Program Plan i
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U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research p + * "' %,,
I 8g82 04g 850731 1144 R PDR L
m NOTICE Availability of Reference Materials Cited in NRC Publications Most documents cited in NRC publ; cations will be available from one of the following sources:
- 1. The NRC Public Document Room,1717 H Street, N.W.
Washington, DC 20555
- 2. -The Superintendent of Documents, U.S. Government Printing Office, Post Office Box 37082, Washington, DC 20013 7082
- 3. The Na'tional Tech'nical Information Service, Springfield, VA 22161 A!though the listing that follows represents the majority of. documents cited in NRC publications, it is not intended to be exhaustive.
Referenced documents available for inspection and copying for a fee from the NRC Public Docu-ment Room include NRC correspondence and internal NRC memoranda; NRC Office of Inspection and Enforcement bulletins, circulars, information notices, inspection and investigation notices; Licensee Event Reports; tandor reports and correspondence; Commission papers; and applicant and licensee documents and correspondence.
The following documents in the NUREG series are available for purcFase from the NRC/GPO Sales
~
Program: formal NRC staff and contractor-reports, NRC sponsored conference proceedings, and NRC booklets and brochures. Also available are Regulatory Guides, NRC regulations in the Code of Federal Regulations, and Nuclear Regulatory Commission issuances.
Documents available ' rom. the National Technical Information Service include NUREG series reports and technical reports prepared by other federal agencies and reports prepared by the Atomic Energy Commission, forerunner aaency to the Nuclear Regulatory Commission.
Documents available from public and special technical libraries include all open literature items, such as books, journal and periodical articles, and transactions. Federal Register notices, federal and state legislation, and congressional reports can usually be obtained from these libraries.
Documents such as theses, dissertations, foreign reports and translations, and non-NRC conference proceedings are available for purchase from the organizrtion sponsoring the publication cited.
i Single copies of NRC draft reports are available free, to the extent of supply, upon written request to the Division of Technical Information and Document Control, U.S. Nuclear Regulatory Com-mission, Washington, DC 20555.
Copies of industry codes and standards used in a substantive manner in the NRC regulatory process are maintained at the NRC Library, 7920 Norfolk Avenue, Bethesda, Maryland, and are available i
there for reference use by the public. Codes and standards are usually copyrighted and may be purchased from the originating organization or, if they are American National Standards, from the i
American National Standards institute l1430 Broadway, New York, NY 10018.
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NUREG-1144 RD, RG, RM, RV Nuclear Plant Aging Research (NPAR)
Program Plan Minuscript Completed: July 1985 e
Dita Published: July 1985 Division of Engineering Technology Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission W chington, D.C. 20555 f - s.,,
FOREWORD ~
This document presents a plan for Nuclear Plant Aging Research to be performed principally by the Electrical Engineering, Instrumentation and Control Branch, Division of Engineering Technology, Office of Nuclear Regulatory Research.
It presents the objectives of the program, describes the research that will be carried out to achieve the objectives, and identifies areas of cooperation and/or coordination with research being performed by other organizations.
We perceive this plan to be a living document and expect to revise it period-ically to take into account our experience in implementing the plan and com-ments received from interested parties within the NRC and among the public.
Comments on this document are welcome at any time and will be considered in the development of subsequent editions of this plan.
They need not be restricted to the research activities described herein; comments identifying omissions or recommending additional research are also welcome.
'kMWW Bill M. Morris, Chief Electrical Engineering, Instrumentation an Control Branch Approved by:
\\
GuyA.lrlotto, Director A
Divisiqn of Engineering Technology Office of Nuclear Regulatory Research iii
LIST OF ACRONYMS ASPS-Accident Sequence Precursor Study HPCI High Pressure Coolant Injection System (in BWRs)
IPRDS In-Plant Reliability Data System IS and MM Inspection, Surveillance and (condition) Monitoring Methods NOAC Nuclear Operations Analysis Center at ORNL NPAR Program Nuclear Plant Aging Research Program NPRDS Nuclear Plant Reliability Data System NSAC Nuclear Safety Analysis Center operated by the Nuclear Industry Supported Electric Power Research Institute (EPRI)
ORNL Oak Ridge National Laboratory RCIC Reactor Core Isolation Cooling RG Regulatory Guides SRP Standard Review Plan NRR Office of Nuclear Reactor Regulation, U.S. NRC AEOD Office for Analysis and Evaluation of Operational Data, U.S. NRC IE Office of Inspection and Enforcement, U.S. NRC ACRS Advisory Committee on Reactor Safeguards v
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ABSTRACT The nuclear plant aging research described in this plan is intended to resolve issues related to the aging and service wear of equipment and systems at commer-cial reactor facilities and their possible impact on plant safety.
Emphasis has been placed on identification and characterization of the mechanisms of material and component degradation during service and evaluation of methods of inspection, surveillance, condition monitoring and maintenance as means of mitigating such effects.
Specifically, the goals of the program are' as follows:
Program Goals A.
To identify and characterize aging and service wear effects which, if unchecked, could cause degradation of structures, components, and systems and thereby impair plant safety.
B.
To identify methods of inspection, surveillance and monitoring, or of.
evaluating residual life of-structures, components, and systems, which will assure timely detection of significant aging effects prior to loss of safety function.
C.
To evaluate the effectiveness of storage, maintenance, repair and replace-ment practices in mitigating the rate and extent of degradation caused by aging and service wear, v
TABLE OF CONTENTS Page FOREWORD.....................
jjj LIST OF ACRONYMS..................,,.,,,,,,
jy ABSTRACT......................,,,,,,,,,
y
- 1. 0 INTRODUCTION 1_1 1.1. Nature of Aging Processes 1-2
- 1. 2 Potential Impact of Aging on Safety 1-2 1.3 Issues Which Need Resolving 1-3
- 1. 4 Specific Technical Objectives of Research 1-4 2.0 UTILIZATION OF RESEARCH RESULTS.................
2-1 3.0 RESEARCH APPROACH........................
3-1 3.1 Risk and Systems Oriented Identification of Aging Effects..
3-1 3.1.1 Review of Nuclear Plant Experience........
3-1 3.2 A Phased Approach to Aging Assessment 3-1 3.2.1 Phase I 3-1 3.2.2 Phase II.....................
3-3 4.0 COORDINATION WITH OTHER PROGRAMS INSTITUTIONS AND ORGANIZATIONS.
4-1 5.0 SCHEDULE............................
5-1 APPENDIX A Research Strategy and Program Elements.........
A-1 APPENDIX B Schedules and Milestones................
B-1 REFERENCES R-1 vii
LIST OF FIGURES Page Figure 1 Research Approach - NPAR Program.
3-2 Figure A.1 NPAR Program Strategy A-3 Figure B.1 1.
Risk Oriented Identification of Aging Effects.
B-2 Figure B.2 2.
Component Aging Assessment and Recommendations for I, S and MM, Phase I...........
B-3 Figure B.3 2.
Phase II...................
B-4 Figure B.4 3.
Evaluation of Role of Maintenance in Mitigating Aging Effects...........
B-5 Figure B.5 4.
Technical Considerations for Component Lifetime Evaluation.
B-6 Figure B.6 5.
Utilization of Recommendations.
B-7 Figure B.7 Illustrative Detailed Schedule - Motor Operated Valves (Group 1 Component)..
B-8 LIST OF TABLES Table 1 Category of Equipment and Systems of Current Interest.
A-7 l
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1.0 INTRODUCTION
In his comments on the Long Range Research Plan, H. R. Denton, Director of the Office of Nuclear. Reactor Regulation, USNRC, identified a need for a research program to investigate the safety aspects of aging processes in commercial nuclear power plants.
Initiation of an aging research program was also recommended by the ACRS in their 1983 report to Congress.
The aging research program has been planned and is currently being implemented by the
'USNRC Office of the Nuclear Regulatory Research (RES).
This document describes the rationale, methodology and utilization for the research to be conducted.
To obtain a preliminary overview of the nature and extent of the aging processes which should be considered, and potential methods of better understanding these' processes, several " workshops" and scoping studies were sponsored by the Office of Research.
These are described in References 1, 2, 3, 4, 6, and 10.
These efforts have considered plant operating experience as represented by Licensee Event Reports (LERs), "Delphi Sessions," interviews involving individuals with plant operating and design experience, and risk significance of components and systems based on Probabilistic Risk Assessment (PRA).
Also of significance in evolution of this plan were a number of comments and discussions involving staff members from NRR, IE, and AE0D and. members of the ACRS.
To set a proper perspective for describing the Nuclear Plant Aging Research (NPAR) Program one must first appreciate the current status of the operating nuclear power plants.
As of January 1985, there were eighty-five licensed commercial power reactors in operation in the.U.S. with the following age distribution:
Operating Lifetime (Years Since Operating-License)
- LWRs greater than 20 years 2
between 15 and 20 years 6
between 10 and 15 years 36 between 5 and 10 years 22 less than 5 years 19 fn addition, there were. several reactors nearing completion of construction and initial operation.
For some plants construction has been terminated or delayed and equipment or structures are being removed to other sites or mothballed for possible future reactivation.
As more operating reactors come on-line and those now operating advance in age, there must be a conscious ~ national effort to understand the time related degra-dation of nuclear plant equipment during service.
The potential impact of such degradation on safety must be understood and the measures which must be taken to mitigate significant aging degradation must be available.
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1.1 Nature of Aging Processes The components and structures in these reactors involve a broad spectrum of mate-rials' and designs, they operate and function under different applications and environments, and they are maintained with differing practices and philosophies.
Consequently, there are a variety of factors which can lead to the degradation of the functional capability of equipment.
These include:
(1) natural internal chemical or physical processes during operation; (2) external stressors (e.g., radiation, humidity, chemical, etc.) caused by the storage or operating environment; (3) service wear, including changes in dimensions and/or relative positions of individual parts or subassemblies caused by operational cycling; (4) excessive testing; and (5) improper installation, application, or maintenance.
For the purpose of this discussion and throughout this report, the term " aging,"
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represents the cumulative changes with passage of time that may occur within a component or structure because of one or more of the aforementioned factors.
From this perspective, it is clear that aging is a. complex process that begins-as soon as a component or structure is produced and continues throughout its service life.
Aging is certainly a significant factor in determining the limits of nuclear plant lifetime or life extensions.
No nuclear plant, including those still under construction or being mothballed, should be considered immune from its effects.
1.2 Potential Impact of Aging on Safety Although nuclear plant aging could have an impact on the efficiency of electric power generation, the concern addressed by this research program is that' plant safety could be affected if degradation of key components or structures is not detected prior to loss of functional capability, and timely corrective action is not taken.
What must be understood is how the aging process may change the likelihood of component failures in systems which are designed to mitigate transients and accidents and therefore reduce safety margins, and how age degradation can cause such events to be initiated.
The survey (Reference 2) of LERs conducted by ORNL'as part of the planning for the development of this aging research plan shows that numerous instances of aging degradation induced failures of equipment have been reported.
The reported events indicated that essentially all types of safety-related systems have been affected by a variety of forms of degradation.
ORNL has also described in more detail the background of selected age related LERs to provide a better perspective regarding the safety significance of age degradation (Reference.11).
Based on these studies, aging effects can contribute to the probability of initiation of transients and accidents and to the probability of failure of the mitigating equipment during operation.
Also of concern is the possibility that common mode failures in redundant, but age-degraded safety-related equipment could be induced by transient stressors (electrical pulse, high pressure, vibration, steam, radiation, etc.) associated with a trigger event such as an anticipated operational transient or an accident.
The safety significance, or contribution to risk of, common-cause equipment 1-2
failures is difficult to quantify.
Two notable potential contributors to such failures, seismic events and fires, are the subjects of research programs to develop better. data and methodologies to reduce the uncertainty regarding the risk from such events.
For another potential common failure cause, the harsh environments resulting from loss of coolant or high energy line break accidents, the approach has been to test prototype electrical equipment to demonstrate performance under accident environments.
Simplified " accelerated aging" tech-niques have been employed to-simulate, for the test sample, the effects of temperature dependent chemical reactions and radiation exposure during opera-tion.
However, there is doubt that such techniques realistically represent the effects of in-service degradation.
For example, it is known that accelerated radiation aging at the high dose rates typically employed by commercial testing laboratories does not produce the degree of embrittlement of cables caused by radiation at the actual dose rate encountered inside containment during opera-tion.
Also, the polymeric materials in some kinds of solenoid valves have been observed to become more vulnerable to failure under LOCA conditions due to natural aging than artificial aging.
Because of the evidence that artificial or accelerated aging techniques may be inadequate it is difficult to assess at this time the degree of vulnerability of safety equipment, degraded by age related service and wear, to common-mode failure during accidents and transients which involve abnormal stresses and demands on the equipment.
However, the number of cases of age degradation including failures reported during normal operation suggests that such equipment failures could occur concurrently for redundant equipment during an accident or a transient even if the redundant equipment were in an earlier stage of the aging-degradation process.
Aging degradation, therefore, represents an as yet unknown, but potentially signif-icant, contributor to common-cause failure of safety-related equipment during transients and accidents.
- 1. 3 Issues Which Need Resolving Many of the issues regarding safe nuclear plant operation in the face of aging I
processes have been, and are being, addressed by the nuclear industry through research, designs, standards development and' improved operation and maintenance.
Nuclear utilities, EPRI, INPO, NSSS vendors, architect engineers, DOE, IEEE, ANS, ASME, ASTM, national laboratories, and the NRC currently participate in such efforts.
However, because of the variety of components and structures and their applications, the complexity of the aging processes, the limited experience with prolonged operation of commercial LWRS, and the potential for adverse impact on safety, significant questions remain unanswered.
These questions include:
What are the specific aging effects which could impact the safety of operating reactors?
What methods of inspections, surveillance and monitoring will be effective in detecting these affects before safety is adversely affected?
How effective are current maintenance programs in mitigating aging?
What should be done to understand the state of aged " mothballed" equipment or equipment out of service for long periods in terms of reduced safety margins and assure that later they can be operated safely?
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Under what circumstances can inspection, surveillance and monitoring, including testing, become excessive in that they cause more damage to
-equipment than they prevent or result in inordinate occupational exposure to radiation?
Can the residual operational lifetime of components and structures be sufficiently quantified to justify reduction in inspection requirements or nuclear plant license extensions?
This research program has been initiated to achieve an understanding of nuclear plant aging, its potential effects on safety, and methods for its detection and mitigation, sufficient for answering these questions and supporting regulatory decisions on such issues.
1.4 Specific Technical Objectives of Research The objectives of the nuclear plant aging research (NPAR) program are:
A.
To identify and characterize aging and service wear effects which, if unchecked, could cause degradation of structures, components, and systems and thereby impair plant safety.
-B.
To identify methods of inspection, surveillance and monitoring, or of evaluating residual life of structures, components, and systems which will assure timely detection of significant aging effects prior to loss of safety function.
C.
To evaluate the effectiveness ~of storage, maintenance, repair and replace-ment practices in mitigating the rate and extent of degradation caused by aging and service wear.
This research program has been developed to meet these objectives.
The program involves (a) risk oriented identification and selection of components, systems or structures for which assessments of the impact of aging on safety performance are to be conducted; (b) review of design bases safety margins, qualification testing, operating experience, and methods for surveillance, inspection, moni-toring and maintenance, leading to the development of recommendations for in-depth engineering studies; (c) engineering studies including verification of inspection, surveillance, monitoring and maintenance methods, in situ examina-tions and collection of data from operating equipment, and cost / benefit analyses.
The anticipated utilization of the research results to resolve aging related issues ~is discussed in Section 2.0.
Section 3.0 and Appendix A of this report provide additional details on the research approach and the specific research activities planned.
=
The degree to which the program objectives are met will depend on the resources allocated through the budget process, utilization of results from other NRC programs, the level of participation by the nuclear industry, the availability of information from foreign countries through international cooperation, and the availability of information from other government agencies.
Specific interfaces which will be established and maintained, during implementation of the plan, are discussed in Section 4.0.
Also, currently estimated schedules and milestones for completing specific research activities over the next five year period are discussed in Section 5.0 and in Appendix 8.
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s 2.0 UTILIZATION OF RESEARCH RESULTS The aging research program will result in better understanding of aging pro-cesses and imprcved confidence in methods for detecting and mitigating aging degradation.
This sill provide a basis for timely and sound regulatory decisions regarding continued operation of nuclear plants of all ages.
Detection and timely mitigation of aging degradation at an early stage, before functional capa-bility is impaired and before continued safe operation becomes questionable, will avoid unplanned and costly plant shutdowns.
In addition, operating plant maintenance practices will become more effective.
Wear from excessive testing can be minimized through use of more effective surveillance techniques and equipment reliability will be improved.
In addition to these general benefits, specific uses for research results are as follows:
(1) To support the NRR " Maintenance and Surveillance Program," which has as its purpose the development of criteria to evaluate maintenance and surveillance activities conducted at commercial nuclear plants; (2) To support implementation of 10 CFR S50.49, " Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants,"
which includes the requirement:
" Equipment qualified by test must be preconditioned by natural or artificial (accelerated) aging to its.end-of-installed life condition.
Consideration must be given to all significant types of degradation which can have an effect on the functional capability of.the equipment.
If preconditioning to an end-of-installed life condition is-not practicable, the equipment may be preconditioned to a shorter designated life.
The equipment must be replaced or refurbished at the end of this designated life unless ongoing qualification demonstrates that the item has additional life."
The evaluation of actual aging processes through the research program will provide a basis for assessing the adequacy of industry methods for precon-ditioning prior to qualification testing or may lead to recommendation for surveillance or monitoring.
This may involve recommendations for revisions of the IEEE standards related to. environmental qualification through participation, of researchers in the aging research program, in the relevant IEEE standards committees, and development of industry consensus based on the results of the research.
Some of the relevant IEEE standards are:
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323 - Standard for Qualifying Class IE Equipment for Nuclear Power Generating Stations 344 - Recommended Practice for Seismic Qualification of Class 1E Equipment for Nuclear Power Generating Stations 317 - Electrical Penetration Assemblies in Containment Structures 382 - Type Test of Class 1E Electric Valve Operators 501 - Seismic Testing of Relays 535 - Qualification of Class 1E Lead Storage Batteries 572 - Qualification of Class 1E Connection Assemblies 649 - Qualifying Class 1E Motor Control Centers 650 - Qualification of Class 1E Static Battery Chargers and Inverters (3) To support the development of the ASME industry consensus on standards for operations and maintenance of mechanical equipment through participation, of researchers from the aging research program, in the relevant ASME commit-tees.
The components and systems currently being considered in these standards include:
OM-01 Pressure Relief Devices OM-04 Dynamic Restraints (Snubbers)
OM-06 Performance Testing of Pumps OM-08 Motor Operated Valves OM-10 Performance Testing of Valves OM-13
. Power Operated Relief Valve Assemblies OM-15 Emergency Core Cooling System OM-16 Inservice Testing of Diesel Drives (4) Support NRR in resolution of Generic Issue II.E.6.1 "In Situ Testing of Valves" by assessing methods for monitoring motor operated valves.
(5) Support NRR in evaluating aging and service wear of diesel generators.
(6) Support NRR in development of criteria for evaluating plans for "mothballing" plants during construction and for reactivation of
. mothballed equipment.
(7) Support implementation of 10.CFR S50.51 (Duration of license, renewal) through development of criteria for evaluating requests for extension of plant operating licenses.
(8) Development of criteria for evaluating the reliability of " snubbers" as piping restraints (this will become more significant when the number of installed snubbers is reduced).
'(9) Support NRR in resolution of Generic Issue 70, "PORV and Block Valve Reliability."
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3.0 RESEARCH APPROACH
.The NRC aging research program will be carried out in discrete stages as portrayed in Figure 1.
A selection process will be followed to establish priorities for detailed aging assessments of specific systems and components.
Selection criteria will include the potential contribution to risk from failure of systems or compo-nents, nuclear plant experience, and expert judgment regarding proclivity of the system or component to aging degradation.
3.1 Risk and Systems Oriented Identification of Aging Effects Completed scoping studies-(References 2, 4, and 6) and ongoing probabilistic risk studies and systems analyses will be evaluated to identify (a) the rela-
-tive importance to risk from the aging of various plant systems and components, (b) the stresses to which equipment will be subjected during operations and design basis events (including plant cycling and trips), and which could pose an increased potent'ial for common-mode failure of aged redundant components, (c)_ levels of component functional degradation at which impairment of system performance would cause an increase in the severity or frequency of plant tran-sients or an unacceptable degradation in the capability to mitigate design basis events. These evaluations will be combined with the evaluations of aging and service wear experience to establish general program priorities and direction.
3.1.1 Review of Nuclear Plant Experience The LWR operating-experience which relates to equipment aging and service wear will be evaluated to identify aging effects which have occurred to date and which require further study to understand how such effects could impact safety over the expected forty years of plant life.
Specific LWR oriented data bases to be evaluated include Licensee Event Reports, the In-Plant Reliability Data System, Plant Preventive Maintenance Records, Nuclear Plant Experience Reports, Inservice Inspection Reports, and the :luclear Plant Reliability Data System.
Non-LWR experience will also be considered including that from non-commercial reactors, fossil-fueled power plants, military'and aerospace programs, and the petro-chemical industry, etc.
General trends from operating experience will be used in conjunction with risk-aging systems evaluations.
Based on the evaluations carried out to date, a preliminary selection has been made of those components and systems for which the initial aging assessments will be performed.
Research schedules have been established for these studies.
The selected items are listed in Table 1 (see Appendix A, page A-7).
3.2 A Phased Approach to Aging Assessment 3.2.1 Phase I Aging assessments of selected systems or components will involve two stages.
Phase I will include evaluations of design specifications including:
materials; 3-1
ResearCh Approach - NPAR Program Phase 1 Phase ll e Operating Experience Verification of improved Recommendations for Select Revie e and Analysis e
e Review of Methods I, S, and MM*
Systems e
1, S, and MM Tests of Naturally Evaluation of " Mothballed
and and Technology for e
e Components I, S, and MM g
Aged Components, and Equipment.
Screening Type Components, Models, for e
o Modification of Codes, Assessment Exammation and Tests Samples with S,mulated i
Standards and Guides w
e Interim Recommendations Degradation e Lifetime Extensions Cost / Benefit Study k
for Eng, eering Tests e
m in Phase II Figure 1
- I, S, and MM - Inspection, Surveillance and Monitoring Methods
r I
operational environments; qualification tests; operating experience; systems interfaces; methods for inspection, surveillance, monitoring, and maintenance; and screening type equipment examinations and tests.
In a Phase I component or system analysis the product of the study will be, a preliminary identification of the significant modes of degradation, and evaluation of current inspection, surveillance and monitoring methods.
Based on these evaluations, recommenda-tions will be developed to identify detailed engineering tests and analyses to be conducted in Phase II.
Phase I evaluation of systems may lead to recommenda-tions for a systems level Phase II assessment or to recommendations for assessments of components not yet included in the plan.
3.2.2 Phase II Phase II assessments will generally involve some combination of:
(a) tests of naturally aged equipment or of equipment with simulated degradation; (b) labora-tory or in plant verification of methods for inspection, monitoring, and surveil-lance; (c) development of recommendations for inspection or monitoring techniques in lieu of tests which cause excessive wear; (d) verification of methods for evaluation of residual service lifetime; (e) identification of effective mainte-nance practices; (f) in-situ examination and data gathering for operating equipment; and (g) cost / benefit analyses.
Component aging assessment will include the examination and testing of equipment removed from service at operating LWRs and decommissioned reactors.* This equip-ment will be used to identify failure modes related to aging and service wear and indicators of such potential failure modes which may be monitored to detect the approach to failure in an incipient stage.
Tests of aged equipment will simulate, where appropriate, stresses typical of the dynamic, seismic, electrical, mechanical, thermal, steam, and radiation transients anticipated during operating service and representative of design basis events.
Selection of equipment, for which examinations and tests will be performed, will be based on considerations of risk-aging / systems evaluations and evaluation of previous experience.
In situ monitoring of operating equipment at LWRs will also be performed to gain an understanding of the interaction between aging and service wear defect characterization and inspection, surveillance and maintenance.
When available, aging assessment will also be performed on equipment which has failed during operation as well as on equipment which has survived extensive periods of operation.
This will be done in order to gain an understanding of those aging effects which would only be excited during a trigger event accompanied by abnormal stresses.
- A number of naturally aged components are to be obtained during decommission-ing of Shippingport and others are being requested from utilities and other decommissioned reactors.
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4.0 COORDINATION WITH OTHER PROGRAMS INSTITUTIONS AND ORGANIZATIONS Various institutions and the industry organizations have performed studies and instituted programs relevant'to the aging research.
Results of the more impor-tant activities are reported in the References (numbers 1, 3, 4, 5, 7 and 9).
Also, there are a number of ongoing programs which are producing significant results which cannot and should not be duplicated.
A major emphasis in the
. program plan is that proper coordination and integration of plant aging.research activities shall be attained at various levels to achieve overall program goals and objectives and to assure the efficient use of available resources.
Interfaces have been established and will be maintained with ongoing NRC programs.
External programs involving both domestic and foreign organizations, similarly have been contacted. -The ongoing programs and contacts are noted below:
NRC PROGRAMS Sponsor Licensee. Event Reports (LERs)...............................AEOD In-Plant Reliabil.ity Data System (IPRDS)............
.......DRA0/RES Reliability Assurance Program...............................DRA0/RES Procedures for Evaluating-Technical-Specifications (PETS)...DRA0/RES Maintenance and Surveillance Program........................DHFS/NRR Equipment Qualification Research - Electrical, Mechanical...DET/RES Materials Research..........................................DET/RES Mechanical Components and Structural Research...............DET/RES Equipment. Quali fication - Licensing Activities.............. EQB/NRR DOMESTIC PROGRAMS OUTSIDE NRC Sponsor Aging / Seismic Research......................................EPRI Equipment Qualification Research..............
.............EPRI Condition Monitoring of Electrical Equipment................EPRI Decommissioning of Shippingport Atomic Power Station........ DOE Nuclear Plant Reliability Data System (NPRDS)...............INP0 Nuclear Plant-Life Extension Research.......................EPRI.
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FOREIGN ORGANIZATIONS France...........................CEA, EDF W. Germany.......................BMI, BMFT, GRS, TUV, KWU Italy............................ENEL, ENEA Japan............................MITI, NUPEC It will be necessary to coordinate with externally sponsored programs and to integrate the knowledge and experience previously gained by outside organizations.
There are very likely other aging-related research programs which will be sponsored by EPRI, DOE, 000, and foreign organizations.
An important activity in the NPAR program will be identification of relevant programs and establishment of appropriate interfaces.
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5.0 SCHEDULE The. currently estimated schedules and milestones for completing specific research activities over the next five years are provided in Appendix B.
These general schedules, and particularly schedules.for evaluation of specific components and systems, will depend on funding, the assignment of priority, and the degree of coordination and participation by other institutions and organiza-tions.
The NRC/RES staff and its contractors will actively pursue the solicita-tion of such participation from domestic and foreign institutions and organizations.
The active interest in requirements for plant-life extensions should facilitate industry cooperation and active participation in aging research.
A critical. program element identified for the NPAR is the timely availability of naturally aged equipment from operating power plant facilities.
Post-service examination and testing of these naturally aged equipment are essential to relate artificial aging (pre-aging / accelerated aging) to normal aging.
Evaluation and analysis of naturally aged equipment is intended to generate recommendations for criteria and guidelines for decisions.
Cooperative programs among the indus-try and research organizations should be instituted to facilitate the availabil-ity of naturally aged equipment for aging research.
Scnedules and resource requirements will need adjustments to reflect the extent of these cooperative programs.
hRC 'unding available to the program for FY 85 is approximately 2.2 million dollo.s.
The FY 86 and FY 87 funding levels have not yet been firmly established.
In addition NRC staff participation at an average level of three full time professionals per year will be needed for the duration of the program.
When participation by outside organizations is achieved, the resources provided from outside NRC will be identified in future revisions of this plan.
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t APPENDIX A
-RESEARCH STRATEGY AND PROGRAM ELEMENTS TABLE OF CONTENTS Page A.1 RESEARCH PROGRAM STRATEGY.........................................
A-1 A.1.a Discussion of Strategy Flow Chart.......................
A-1 A.1.b Contractor Support......................................
A-2 A.2 DESCRIPTION OF RESEARCH ELEMENTS..................................
A-2 A.2.a Risk and Systems Oriented Identification of Aging Effects.................................................
A-2 (1) Importance of Aging in Risk Assessments.................
A-2 (2) Analysis of the Impact of Component Aging on System Performance.............................................
A-4 (3) Review of LWR Opeialing Experience to Identify Aging Trends..................................................
A-5 (a) Operating Experience Survey........................
A-5 (b) Survey of Aged Plant Facilities....................
A-5 (c) Gathering of Experts' Knowledge via Workshops......
A-5 (4) Selection of Components for Aging Assessment............
A-6 (5) Evaluation of Impact of Plant Cycling and Trips on Components and Structures...............................
A-6 A.2.b Component Aging Assessment and Recommendations for Inspection, Surveillance and Monitoring Methods (IS&MM).
A-8 (1) Phase I................................................
A-8 (a) Operating Experience - Review and Analysis..........
A-8 (b) Review and Analysis of Materials, Designs and Specifications, Stressors, Service Environments and Operations Parameters...........................
A-8 (c) Identification of Failure Mechanisms / Modes /Causes and Performance Indicators..........................
A-10 (d) Review of Current Methods and Technology for IS&MM..
A-10 (e) Screening Type Post-Service Examination and In Situ Testing.............................................
A-11 (f)
Interim Assessment and Recommendations..............
A-11 A-i
TABLE OF CONTENTS (Continued)
Page (2) Phase II................................................
A-11 (a) Review and Verification of Improved IS&MM...........
A-11 l
(b) Test Naturally Aged Components, and Component Models/ Samples with Simulated Degradation...........
A-12 (c) Value-Impact Study..................................
A-12 A.3 EVALUATION OF THE ROLE OF MAINTENANCE IN MITIGATING AGING EFFECTS..
A-12 A.4 TECHNICAL CONSIDERATIONS FOR COMPONENT LIFETIME EVALUATIONS........
A-13 A.4.a Evaluation of Service-Life Prediction Methods-Electrical l
Components...............................................
A-13 A.4.b Residual Lifetime Evaluation-Mechanical Components.......
A-13 A.5 INVESTIGATION OF AGING /SE!SMIC STRESS INTERACTIONS.................
A-14 i
I I
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A-li
APPENDIX A Research Strategy and Program Elements 1
An overview of the phased approach to research for components and systems was described in Section 3.0.
In this section of the program plan a comprehensive discussion of the overall program strategy is presented.
Also included is a detailed description of current research activities.
A.1 Research Program Strategy The NPAR program has been planned so that the major program elements (the cir-cled elements in Figure A.1) can be accomplished within a reasonable schedule.
A number of supporting tasks (identified by blocks in Figure A.1) have been selected and scheduled so that research on the major elements can proceed with the full benefit of the completed necessary groundwork.
Where information is needed from manufacturers and utilities, avenues of com-munication have been planned.
Where related research is underway, liaison is planned.
Insofar as practical, both government and industry-supported programs, including foreign efforts, will be incorporated.
The overall program plan will include establishment of a central data bank of information (component and system specific) on:
research relevant to plant aging, standards and guides relevant to aging; and citations and sources of published information on plant aging.
This central, integrated data bank of information will benefit not only the NRC in its plant aging research, but also all other organizations (labora-tories, professional societies, utilities, and manufacturers) concerned with plant aging.
Also, the program will identify gaps in existing aging-related research that can be filled by government or industry sources, depending on which is most appropriate.
To provide the maximum possible flow and exchange of information, one product of this program will be the publication of reports
.on the research tasks.
The research information will be disseminated through preparation of technical papers, presentations at technical conferences, sponsorship of workshops and symposia, and exchange of visits with principal sources of related research.
A final product of the research program will be recommendations for the revision of existing standards and regulatory guides and the development of new standards and guides, as necessary.
The technical basis, developed from the research program, will accompany all of the recommendations.
A.1.a Discussion of Strategy Flow Chart The task of developing the overall program strategy has already been substan-tially accomplished.
During the development process, the program strategy was presented ahi discussed with groups in NRR, I&E, AE0D and ACRS subcommittees.
The plan is illustrated in Figure A.1.
The middle row of circles identifies the major tasks or milestones.
The upper and lower rows of blocks identify subsidiary tasks that will support the major tasks.
The first major element of the program is to:
(a) identify and select the equipment and system for which degradation and failure have safety impacts; and (b) to define the boundaries of the equipment (i.e., its interfaces with other parts of the safety systems A-1
in which it is installed, its mounting configuration, and the input and output parameters).
The second major element is to evaluate the reported operating experiences of groups of components and systems which will be selected on the basis of their aging significance to the safety of LWR plants.
The third major element is the Phase I aging assessment of the selected groups of components and systems.
The fourth major element is the Phase II aging assessment, defect characterization and recommendations for inspection, surveillance and condition monitoring methods (IS and MM) for selected components and systems.
The fifth major element, preparation of application guidelines, is based on the output of the preceding elements.
The comprehensive aging assessment and recommendations for IS&MM will lead to practical guidelines for their application, which will be the products of the final major elements.
They include the preparation of recommendations for: new-and revised standards and regulatory guides; guidelines for effective maintenance; evaluation of " mothballed" equipment; and relicensing considerations.
The flow logic associated with implementing the overall NPAR program should be applicable to an electrical or mechanical component, or to a I
structural element, or to fluid and electrical systems.
Each major program l
element is discussed in more detail.
A. l. b Contractor Support The following national laboratories are currently involved in plant aging research on electrical and mechanical components and fluid and electrical systems.
(1) Oak Ridge National Labortory (0RNL)
(2) Brookhaven National Laboratory (BNL)
(3) Idaho National Engineering Laboratory (INEL)
(4) Battelle-Pacific Northwest Laboratories (PNL)
In addition, the following private sector participants are also involved:
(5) Franklin Research Center (FRC) as subcontractor to ORNL and BNL (6) System Engineering Associates, Inc. (SEA)
A.2 Description of Research Elements A.2.a Risk and Systems Oriented Identification of Aging Effects The research activities identified in sections which follow apply to the pro-cess of selecting safety equipment, safety groups and safety systems that may impact plant safety as a consequence of degradation with time.
A.2.a(1)
Importance of Aging in Risk Assessments The objective of the initial project task was to identify components in nuclear power plants which would adversely affect risk if aging processes were to contri-bute significantly to decreased component reliability or degraded performance characteristics.
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The approach taken in this task was to use the results of existing (Reference 6) probabilistic risk analyses (PRAs) to gain some insights into relationship between risk and component aging or wear-out.
An attempt was made to develop and apply a method for determining the potential risk significance of aging effects which is based on determining the sensitivity of risk to increases in failure rate.
Based on the aging sensitivity measure many of the potentially risk significant components identified in the initial study are in the auxiliary feedwater sys-tem, the reactor protection system and the service water systems.
Pumps, check valves, motor operated valves, circuit breakers, and actuating circuits were the component types which have the most potential risk impact.
Subsequently, this effort will be supplemented with the collective judgement of technical experts on the proclivity of components toward aging.
Interim recom-mendations then will be generated for the components for which aging assessments should be pursued.
However, as the study on risk assessment progresses, further sophistication and refinement of current PRA techniques will be necessary.
The reason is that the risk ranking of systems and components could change with the consideration of aging effects.
The information presented in a standard PRA does not include time dependent effects.
In determining the risk level at a plant, PRA's gener-ally use a time averaged unavailability.
In dealing with aging issues we are interested in the time dependent nature of risk.
This limits the nature of the information that can be' extracted from a PRA without extensively modifying the PRA.
Additional research tasks have been contemplated to include considerations for time dependent failure rates.
A.2.a.(2)' Analysis of the Impact of Component Aging on System Performance In the overall strategy for the NPAR program it was recognized that to evaluate plant safety in the presence and the consequences of aged components an'd their interfaces in vital LWR systems, a systems approach and detailed assessments at the component. level must be pursued.
In certain scenarios, investigations of functional interactions between multiple systems.and support systems will be necessary for safety equipment function.
Also, within a given system an inter-action approach will be necessary to evaluate the effect that aged equipment may have on systems performance during and after a postulated event.
The primary objectives of this research element are to: (1) identify unsuspected or unknown age-related problems in systems that may be important to nuclear plant safety; (2) investigate the systems' ability (or inability) to mitigate effects of aging which due to triggered events, may lead to common mode failures; and (3) identify the set of critical equipment and interfaces considered important for those events.
An approach to achieve these objectives will be to select fluid-mechanical sys-tems and electrical systems considered vital for plant safety and (a) conduct systems level assessments; (b) investigate the effect on selected systems, that is, their ability to perform the required safety function with normally aged equipment; and then (,c) identify the set of critical equipment (within the sys-tem boundary) important for the safety function.
The identified critical equip-ment will then become candidates for comprehensive aging assessment.
A-4
In the work plan as a minimum, a fluid system and an electrical system from a LWR will be selected to conduct systems interaction evaluation (with aged equipment) and demonstrate the recommended approach to investigate the effect that an aged-safety-related item may have on plant performance during and after a triggered event (LOCA, MSLB, Lightning and Switching transients, cycling and trips, etc.).
This task is being planned and recommended as a joint effort between the NRC contractor (s), utilities (having interest in studying the selected systems),
architectural engineering firm (s) (which were involved with the participating utility during the design and construction phase of the systems) ano manu-facturers who supplied the equipment in the selected systems.
A.2.a.(3) Review of LWR Operating Experience to Identify Aging Trends (3)(a) Operating Experience Survey The objective of this subelement is to review the currently available sources of LWR operating experience information in order to identify and evaluate aging effects on mechanical, electrical, and structural systems which could result in degradation of the safety function of such components and structures.
Key tasks involved in the subelement are:
(1) a survey of operating experiences from Licensee Event Reports (LERs); (2) a survey of nuclear power plant operat-ing experience from sources other than LERs; and (3) a survey of LWR surveil-lance and maintenance practices.
Abstracts of operating experience information contained in the Licensee Event Reports (LERs) from commercial power plants reported from 1969 to 1982 were surveyed ~in this initial effort (Reference 2).
A total of 4461 event abstracts were reviewed in detail, yielding 3098 events considered age-related.
- Wear, corrosion, crud, and fatigue were the identified failure cause mechanisms in over one-third of the 3098 events.
Pump and valve problems made up almost 30%
of the failed components and almost two-thirds of the reported failures were detected by routine surveillance testing.
(3)(b) Survey of Aged Plant Facilities The primary objective of this task was to survey aged nuclear plant facilities to determine what, if any, loss of function can be attributed to aging.
The information gathered from the plant histories were analyzed for recurring patterns which could be applicable to LWRs (Reference 4).
The results of the limited preliminary investigation of the fluid systems indi-cated that many of the failures reported were due to effects such as erosion, corrosion, vibration, and foreign materials which could affect performance at a system level.
In addition, there appeared to be a strong correlation between the cause of component failure and the system in which it operates.
(3)(c) Gathering of Experts' Knowledge via Workshops Workshops and seminars are planned to benefit from the knowledge of experts having experience with materials, design, fabrication, qualification, operation, A-5
and maintenance of systems, components, and structures in nuclear power plants.
Also, sharing experience with other specialists from laboratories and contractors will strengthen the data base for the plant aging assessment.
The objectives of the early workshops were to identify issues concerning aging, to discuss tne state of knowledge on aging phenomena, and to identify future activities necessary to understand the aging processes.
The first workshop, conducted in August 1982 (Reference 1) program, provided preliminary basis for the NRC-Nuclear Plant Aging Research.
Subsequently, two mini-workshops were conducted to identify whether there is J
any evidence of component or structural aging problems in nuclear power plants,
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and, if so, what problems are of greatest importance.
Fifteen representatives from national laboratories, architect / engineers, nuclear steam supply system vendors, research firms, and a university participated in the workshops.
Based on completed questionnaires and group discussions, which screened over 112 com-ponents believed to be susceptible to excessive aging; by consensus, the follow-3 ing emerged as the most important aging issues: pressure / temperature sensors, e
valve operators, and snubbers (Reference 3).
A.2.a.(4) Selection of Components for Aging Assessments h
Search and analysis for aging processes has been initiated on equipment con-sidered important to plant safety and includes a reasonable cross-section of representative plant components.
The logic for dividing the components and systems into groups, is discussed below.
z$9 In FY 1984, eight components, which are identified as Group 1 components in Table 1, were selected for study.
Aging assessments of Group 2 components were initiated in FY 1985.
Studies of Groups 3 and 4 components are contem-plated for FY 1986.
The reason for such grouping was influenced by: (a) the availability of funds; (b) the attempt to refrain from duplication of work and to supplement other ongoing NRC sponsored research in equipment qualification, j
(c) the expert's opinion and the results of various meetings and workshops, and (d) the conclusions and recommendations which emanated from the initial e
study on "Importance Ranking Based on Aging Considerations of Components Included in Probabilistic Risk Assessments."
(Reference 6) g Zi The selection of systems was based un: experts opinions; system comprising a Ei reasonable cross-section of electrical and mechanical components; systems which 1
are considered important for safety injection function; and systems which have Y
support systems and interfaces of interest to the overall program.
"j A formalized task study has also been initiated on plant level systems to evaluate aging concerns.
Additional system level studies have been contem-
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plated if they can be justified programmatically and adequate resources are available.
]
A.2.a(5) Evaluation of Impact of Plant Cycling and Trips on Components and Structures The influence of plant operational, trans,ient, and accident cyclic loads on degradation of vital components and systems is an issue that requires investiga-tion.
This issue will be investigated to determine whether the components and A-6 m
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TABLE 1 Categorization'of Equipment and Systems of Current Interest Equipment Motor Opera'ted Valves Gr. 1 Check Valves Auxiliary Feed Water Pumps Electric Motors (Large, Inside Containment)
Batteries Chargers / Inverters Snubbers Diesel Generators
'Gr. 2
' Circuit Breakers Protective and Auxiliary Relays Room Coolers Gang Operated Control Switches Solenoid Valves Gr. 3 Cables (power, control, instrument)
Electrical Penetrations Sensars/ Systems / Transmitters - Temperature, Pressure, Level Connectors, Terminal Blocks Gr. 4 Purge and Vent Valves Safety Relief Valves
' Service Water and Component Cooling Water Pumps Pilot Operated Relief Valves Systems High Pressure Emergency Core Cooling Systems Low Pressure Emergency Core Cooling Systems Service Water System Component Cooling Water System Reactor Protection System Residual Heat Removal System / Auxiliary Heat Removal System Class 1E Electric Distribution. System Engineered Safety Feature Actuation System systems selected in Table 1 are subjected to excessive stressors during plant cycling and trips.
If they are, then the next step will be to estimate the severity and signatures of anticipated stressors. The NPAR strategy,-as dis-cussed in Section A.1 for aging assessment of components and systems in the time domain, should be applicable for this task element.
Currently, the contractors who are evaluating the role of maintenance in miti-gating aging effects will also identify potential mechanisms causing component degradation due to plant cycling and trips.
Depending upon the availability of resources, the influence of plant. cycling and trips for other components and syster.s will be considered in future.
A-7 g
A.2.b Component Aging Assessment and Recommendations for Inspection, Surveillance and Monitoring Methods (IS&MM)
To meet the objective of the aging research program it will be necessary to assure that resources are focused on the most significant age related modes of equipment degradation.
Therefore, for each component and system under study, a.
multi phased effort will be pursued.
The Phase I study primarily will consist of assessments and interim recommendations..They will be based on the review and analyses of: operating experiences; current inspection, surveillance, moni-toring and maintenance methods; screening type examinations and tests of equip-ment.
The Phase II study is visualized as a long-term effort.
It will include validation of advanced inspection, surveillance and monitoring methods through testing of samples, models and new equipment with simulated degradation, as well as testing of naturally aged equipment from operating reactor facilities.
A Phased approach to NPAR also will provide opportunities to scrutinize and evaluate contractors' performance and to shift resource allocations for Phase II studies to achieve the most cost effective resource utilization.
A.2.b.(1) PHASE I (a) Operating Experience - Review and Analysis
.A significant amount of knowledge and experience, as well as use of an existing data base, go into the design, application, operation, and maintenance of a component in a nuclear plant system.
Therefore, it is recommended that all available data, on a component selected for study, be extracted from: the design of the equipment and its specifications; from its system application considera-tions; from installation, operation and caintenance manuals; and from operating experiences in real plant environments.
This information will be reviewed and analyzed prior to initiating costly phjsical examinations and tests.
For each component under study, this task will contribute to the identifica-tion of potential failure modes resulting from time-dependent degradation or service wear.
Then, measurable performance parameters, that could be used to monitor and detect degradation of selected components in the incipient stage, will be identified for each failure mode.
The products of this effort will fulfill a large segment of component aging profile and a failure signature analysis.
(b) Review and Analysis of Materials, Designs and Specifications, Stressors, Service Environments and Operations Parameters A comprehensive aging assessment of a component will require identification of the materials and parts within the equipment boundary.
The assessment will include the materials associated with the interfaces between the equipment (under study) and the system in vdlich it functions.
It will be necessary to obtain design data and snecifications, to determine the design basis time vary-ing stress distributions within the equipment boundary and stressors at inter-faces.
Then, one needs to identify key operational parameters (as indicators of perfo*mance) that are practical to monitor and cost-effective to apply to an aging assessment.
A-8
Once the type of equipment (electrical or mechanical) is selected for aging evaluation, the following approach will be used.
(1) Materials:
A list of all significant materials, used in the construction of the equipment or device, will be generated.
The types of materials that will be identified may include: metals, ceramics, polymers, chemicals, oils and greases, paints and varnishes, epoxies, and insulating materials such as textiles, fiberglass, phenolics, cellulosic insulation, teflon, nylon, plastics, corks, rubbers / neoprenes, nitriles, special material and composites.
(2) Design and Specifications:
It is essential that the manufacturer's design data and user's operating requirements and specifications be studied and evaluated.
As a minimum, these will include non proprietary design docu-mentation, operating and maintenance manuals, product literature, design margins, data relevant to operational assurance (including quality assur-ance), design life considerations, and acceptance criteria.
(3) Operating and Environmental Stressors:
Age-related' degradation of com-ponents and structures is a time-dependent phenomenon.
Therefore, an effort must be made to establish tne stresses that a component will ex-perience in a time domain.
One has to consider effects from normal and abnormal operating conditions (including plant cycling and trips) and stresses generated due to trigger events (including electric switching and seismic shocks).
The stresses to be assessed and the environment contributing to degradation in the time domain include:
electrical, mechanical and thermal stresses, chemical, radiation, and other environ-mental stresses including humidity.
It will also be necessary to assess the stressors and stress distribution involving synergistic influences of the aforementioned stressors in a time domain.
For example, the nature of electrical voltages may include, d.c., 50-60 Hz a.c., transients of lightning and switching varieties or superposed stresses generated due to various combinations of voltages.
Examples of mechanical stressors include static loading stress, dynamic loading stress, seismic stresses, vibrational stresses, stresses due to other trigger events, stresses due to resonances, or stresses due to the superposition of two or more pressure loads.
(4) Operational Parameters:
During the aging assessment study, it will be necessary to:
review users' equipment specifications; assess safety func-tions required under normal, abnormal, and accident conditions; and iden-tify critical oerformance parameter (s) that are practical to monitor and cost effective as indicators for age-related degradation.
The aforementioned review and analysis of materials, designs and specifications, stressors and environment, and operational parameters will be attempted on all components selected for the comprehensive aging assessment.
It is recognized that some of the data search and analysis may not be techni.cally as well as practically feasible.
Nevertheless, an effort will be made to acquire as much of this knowledge on a given component as possible.
It safety issues warrant such detailed assessments and adequate resources are available, then the logic for reviews and analysis described above will be followed.
(All NPAR research contractors will be instructed to follow this same strategy.)
A-9
A.2.b(1)(c) Identification of Failure Mechanisms / Modes /Causes and Performance Indicators The search and analysis segment of the comprehensive aging assessment of a selected component will include:
(1) evaluation of failure mechanisms, failure modes, and causes; (2) study of operational assurances; and (3) review of opera-tional successes of similar types of equipment.
The segments of the data base for which no information is available will be recommended as topics for research.
Car selected components:
Failure mechanisms will be established through the process of:
(1) identification of predominant stressors; (2) study of materials; (3) designs of components and parts; and (4) reviews of service environ-ments and applications.
Then, the nature of, and factors contributing to, age-related degradation and failures will be evaluated.
Failure modes, the indicators of failures (i.e., voltage collapse or disturbance in current signature, etc.) will be assessed, and critical age-related failure modes will be identified.
Failure causes, i.e., the conditions of design, manufacture, service environments and applications that may lead to failures, will be deter-mined.
Pertinent information helpful in identifying component specific failure modes, failure causes and mechanisms of failures will be obtained from various ongoing programs including In-Plant Reliability Data System (IPRDS) and Nuclear Plant Reliability Data System (NPRDS).
IPRDS provides a source of data base on selected plant systems and components.
The useful information in the present IPRDS.for discovering aging phenomenon are the narratives' describing the fail-ures (incipient, degraded, catastrophic) and the resulting repair action.
The Nuclear Plant Reliability Data System under the technical management of the Institute of Nuclear Power Operation (INPO) has been gathering engineering and failure data on safety related systems and components.
NPRDS provides an im-portant source for the aging assessment data base.
Therefore, a major effort under the evaluation of operating experiences will be expended in search and analysis of data banks from IPRDS and NPRDS and from other sources such as LERs, Plant Maintenance Records and In-Service Inspection Reports.
A.2.b(1)(d) Review of Current Methods and Technology for IS&MM Existing methods for inspection, surveillance and monitoring will be evaluated to determine those methods likely to be effective in detecting aging degrada-tion in an incipient stage prior to loss of safety function.
Also, it will be important that the methods not be unreasonably expensive to implement and will not result in unacceptable levels of occupational exposure.
Surveillance and monitoring methods to be evaluated are expected to include periodic visual and instrument-aided inspections, and on-line instrumented techniques.
The evaluation also w.11 seek to identify performance parameters and functional indicators that are capable of representing the functional capability of equip-ment.
The selected parameters and indicators s'hould be monitorable at operat-ing plants, at reasonable cost.
A-10 l
l
A.2.b(1)(e) Screening Type Post-Service Examination and In Situ Testing In addition to the evaluations of operationel records, it will be necessary to perform some examinations and tests on selected components to supplement or confirm deduced failure mechanisms.
Such activities will also assist in iden-tification of key-performance parameters which may be monitored to determine the ongoing effects of aging.
Test samples will include equipment removed from service at operating LWRs, and from mothballed or decommissioned reactors.
Depending on circumstances, the examinations or tests may be conducted in situ, onsite after equipment is removed, or at various laboratories with appropriate test and examination capabilities.
The Shippingport PWR, now in decommissioning, is expected to be a source of test equipment.
The candidate components for examination and testing have been identified through site visits by NRC and contractor experts representing a range of disciplines and interests.
Detailed information for each specific component will be developed and used to further assess relevance to commercial LWR systems.
A.2.b(1)(f)
Interim Assessment and Recommendations For the specific types of components and systems under study, an interim aging assessment, defect characterization and evaluation of IS&MM technologies will be made.
Interim recommendations will ther be made for Phase II studies based on the results and reviews of research' activities completed in Phase I sub-elements (a) through (e).
The results of the Fnase I study will be issued in a technical progress report or a milestone report.
Continuation to Phase II activities for a given component and system will be halted if:
(a) adequate data base and experience exist within the industry; (b) industry sponsored programs will adequately address the research needs; and (c) resources can be utilized better for other research activities.
A.2.b.(2). PHASE II (a) Review and Verification of Improved IS&MM In Phase I, the research activity involved the review of current methods and technology for IS&MM.
In the Phase II segment of the research for each cate-gory of components under study, a review of advanced techniques and tech-nologies, either under development or in use, will be made.
Sources outside the nuclear industry will include the petro-chemical, the aircraft industry and various branches of D00 and other government agencies.
Practical feasibility of applying these technologies to nuclear plant components will be explored.
l Laboratory and field application and verification tests of IS&MM candidates will be carried out.
The objective of the tests will be to demonstrate that:
the methods are appropriate to follow the dynamics of the performance para-meters and functional indicators of interest; the methods have adequate selec-tivity (will not give false indications) and sensitivity (will detect in the incipient stage); and suitable acceptance / rejection criteria are available so that maintenance needs can be correctly identified.
A-11
The laboratory tests will involve simulation of defects of varying degrees of intensity to determine sensitivity and criteria; and in defect and environment combinations to determine selectivity.
These laboratory tests will be carried out to verify that the methods are applicable for in situ use at power plants.
Field tests will be carried out at cooperating utilities in order to:
confirm the laboratory results; provide information about the frequency and method of data collection and analysis; and estimate cost effectiveness and practicality of application.
A.2.b(2)(b) Test Naturally Aged Components, and Component Models/ Samples with Simulated Degradation This research element.is perhaps the most cost intensive and difficult element of the NPAR program.
Yet, it is essential to quantify aging and determine that adequate safety margins exist to assure operability of naturally aged components and systems during design basis accident situations.
Considerable effort will be expended in acquiring naturally aged equipment for examinations and tests.
Equipment which has experienced significant operating and environmental stressors will be sought from various sources.
They will include commercial operating plants, decommissioned facilities and research reactors.
A major thrust of this research element will be to evaluate perfor-mance of an aged equipment before and after it is subjected to stressors and environment expected under accident conditions.
The evaluation will be based on following the dynamics of performance parameters and functional indicators which were identified in Phase I activity.
A.2.b(2)(c) Value-Impact Study Various surveillance and monitoring methods for degraded components, considered to have potential for eventual implementation at operating plants, will be evaluated to determine the occupational exposure likely to occur in conjunction with such techniques.
Also, the study will include identification of those methods which are cost effective and practical to apply in commercial plant environment.
Prior to generating application guidelines for improved IS&MM technology a con-scious effort will be made to interact with the NRC staff, code and standards committees and industry groups, as indicated in Figure A.1.
A.3 Evaluation of the Role of Maintenance in Mitigating Aging Effects This effort will consist of-the following activities:
a.
Review current practices and procedures carried out by nuclear utilities to maintain equipment.
Consider each component selected for aging assess-ments and recommend maintenance methods to assure safety.
For complete-ness, also include additional components considered important by the l
utilities.
b.
Review nuclear equipment vendors' recommendations for maintenance of com-ponents or subcomponents selected for aging assessments.
l A-12 l
c.
Perform an evaluation', including a comparative analysis, of the relative merits of:
(a) performing maintenance when a component has been discovered
'to be malfunctioning (corrective maintenance); and (b) performing main-tenance when an observation has been ude througM surveillance, inspec-tion, or monitoring, that a component may not function when required during a design basis or " trigger" event (preventive maintenance).
Emphasis will be placed on the relation between failures (causes or modes) expected to be experienced during operation and those which would potentially occur under the stresses associated with design basis or trigger events.
d.
Identify, where possible, those component failure mechanisms likely to be induced through preventive or corrective maintenance.
Specifically, look for those which might be detectable through short-term, post-maintenance surveillance, inspection, or monitoring.
Develop recommendations, for acceptable or preferred maintenance practices, e.
based on the foregoing activities.
In all cases, the emphasis shall be on the technical or hardware aspects of maintenance rather than on institutional, organizational, programmatic, or human factors considerations.
A.4 Technical Considerations for Component Lifetime Evaluations In some cases it will be impractical or prohibitively costly in resources or occupational radiation exposure to inspect or monitor equipment or structures.
In such cases it will be useful to determine whether there are credible methods for predicting service life of electrical and mechanical components.
In the early scoping study, various tasks have been identified to address some of the technical issues which arise for service life-time evaluation and considerations for relicensing.
They include:.(1) a review of topics in the NRC Standard Review Plan (SRP)'to identify systems and components; (2) a review and analysis of existing service life prediction models for electrical components; and (3) residual lifetime evaluation of selected mechanical compnents.
a.
Evaluation of Service-Life Prediction Methods-Electrical Components As a part of the evaluation of surveillance and inspection methods, the valid-ity of current methodologies for service-life prediction will also be' evaluated.
The initial tasks will be to collect existing models and methods and assess them for application to selected electrical nuclear plant components.
Special attention will be given to account for the combination of thermal and non-thermal stresses and a variety or bilure modes to be identified in other activities of the aging research program.
Also, the basis for the selection of the intervals for surveillance and inspection will be re-evaluated using theoretical service-life prediction techniques.
b.
Residual Lifetime Evaluation-Mechanical Components An initial scoping study has been initiated for the residual lifetime evalua-tion'of vital mechanical components.
This task will provide insights and the technical bases for the lifetime evaluations.
Those components which are not readily accessible during routine inspection, surveillance and maintenance will be of special interest.
A-13
A5 Investigation of Aging / Seismic Stress Interactions An understanding of the significance of aging as a potential mechanism for degrading the functional capability of safety equipment is necessary.
This includes the ability to withstand stresses generated by trigger events, such as seismic disturbances.
Current industry standard (IEEE 323) require preaging before seismic qualification of electrical and mechanical equipment.
- However, the NRC has not determined such a need for mechanical squipment and is currently evaluating the significance of aging as a factor in qualification regulatory guides.
Therefore, an assessment.is needed of the potential importance of aging in degrading seismic performance of equipment.
To avoid duplication, a review of various ongoing and completed programs will be made prior to initiating any new study.
As a minimum, the1 reviews of the following projects will be completed:
Aging / Seismic Correlation Study on Class 1E Equipment by Nutech Engineers. -(NUREG/CR-3808 Sept. 1984)
Program for the Development of an Alternative Approach to Seismic Equipment Qualification, prepared by EQE, Inc., for Seismic Qualifi-cation Equipment Group (SQUG). (Pilot program report-draft.)
Use of Post Earthquake Data to Show Seismic Ruggedness of Certain Classes of Equipment in Nuclear Power Plants, prepared by Senior Seismic Review and Advisory Panel (SSRAP).
(Draft document.)
Correlation between Aging and Seismic Qualification for Nuclear Plant Electrical Components, prepared by Wylie Laboratories.
(EPRI NP-3326, Dec. 1983)
Only those topics (relevant to NPAR strategy for agirig/ seismic interaction study) which have not been addressed adequately, in the aforementioned projects, may be investigated in the NPAR program.
A-14
APPENDIX B Schedules and Milestones The schedules for the effort on major elements of the NPAR program are illustrated in Figures B.1-B.6.
As an example of a detailed schedule with milestones the study of motor-operated valves is presented in Figure B.7.
In the early imple-mentation state of the program plan, and as applied to Group 1 through 4 compo-nents, schedules for various program elements and sub-elements and the cost esti-mates were generated and based on seven major activities (Phase I and II assess-ments).
However, it must be recognized that these activities and schedules may change as the program matures and additional inputs are provided, and specific program needs are further identified.
It should be emphasized that the number of systems and components and the degree and depth of assessments and analyses which can be carried out effectively will depend upon the availability of funds and the period of time over which the results are required.
The timely availability of naturally aged equipment from operating and decommissioned facilities and the opportunity for in situ assess-ments will determine, in a significant manner, the resource requirements and the completion schedule for the various activities.
Resource requirements will be developed as the program evolves during FY 85.
Also, we expect input and program review comments from the offices within NRC and from the industry.
These comments will help to identify and justify, more clearly, the program needs for the later years.
Participation in cooperative programs sponsored by agencies and organizations outside NRC will also influence the needs for NRC funds during the later years.
B-1
NPAR - Milestones and Schedule End of Fiscal Year 85 86 87 88 89 Activity Description 1
Risk Oriented identification of Aging Effects A.
Correlation of Risk and Aging Trends B.
Analysis of impact of Component Aging on System Performance (Currently Planned for 1 Electrical
[
System and 1 Fluid System)
C.
LWR Operating Experience Survey to Identify Aging Trends (Currently for NPRDS)
D.
Selection of Compo ents for Aging Assessment (4th Group)
E.
Evaluation of impact of Plant Cycling and Trips on Components Figure B.1
NPAR - Milestones and Schedule End of Fiscal Year Activity Description 85 86 87 88 89 2.
Component Aging Assessment and Recommendations l
for Inspection, Surveillance and Monitoring Methods PhaseI G R. -1 G R.2, 3, G R. 4 d>
A.
Operating Experience Review and Analysis B.
Review of Current Methods and Technology for inspection, Surveillance, and Maintenance 1
C.
Screening Type Post-Service Examination and in-Situ Testing D.
Interim Assessments and Recommendations Figure B.2 1
NPAR - Milestones and Schedule Activity Description End of Fiscal Year 2 (cont'd) 85 86 87 88 89 Phase 11 A.
Review and Verify Modified Inspection, g
Surveillance and Monitoring Methods B.
Test Naturally Aged Components, Components /Models/ Samples with Simulated Aging C.
Develop Value-impact Studies and Recommendations-for inspection, Surveillance and Monitoring Methods Figure B.3
NPAR - Milestones and Schedule End of Fiscal Year 85 86 87 88 89 Activity Description 3.
Evaluation of Role of Maintenance in Mitigating Aging Effects A.
Survey of Current Maintenance Practices 7
to Mitigate Aging and Service Wear of Components and Structures GR.1 GR.2, 3, GR. 4 B.
Evaluation of Relative Benefits of Preventive and Corrective Maintenance C.
Identification of Potential Mechanisms Causing Equipment Degradation Through improper Maintenance D.
Development of Recommendations for Preferred Maintenance Practices Figure B.4
NPAR - Milestones and Schedule End of F.iscal Year 85 86 87 88 89 Activity Description
.4.
Technical. Considerations for Component Lifetime Evaluation 5
A.
Review and Analysis of Service Life Prediction Methodologies B.
Selected Electrical Equipment C.
Selected Mechanical Equipment Figure B.5
NPAR - Milestones and Schedule End of Fiscal Year Activity Description 85 86 87 88 89
- 5. Utilization of Recommendations A.
Support implementation of 10 CFR 50.49-Revision of R.G.1.89 and IEEE Std 323 B.
Support implementation of 10 CFR 50.51 including Plant License Extension C.
Revise R.G.1.100 D.
Suppori NR R re: G.I.II.E.6.1, in-Situ Testing of Valves E. Support / Endorse IEEE Stds 317,382,501,535, 572,649 and 650 F.
Support / Endorse ASME-O & M Stds OM-01,04, 06,08,10,13,15 and 16 Figure B.6
Motor Operated Valves Program Manager:
Dr. D M. Eissenberg (Group i Component)
Tei. n/ TELEX a:
FTS s24-o747 Contractor: ORNL Mailing Address:
Bldg. 9201 -3 P
- B0828 Oak Ridge Tenn 37830 FY84 F'l85 FY86 FY87 FY88 FY89 Remarks Funding Level:($ x Thousands)
Activity Description Phasei A.
Operating Experience Review and Analysis m
B.
Review of Current Methods and Technology 4
for I, S, & MM S
S C.
Screening-Types Examinations and In-Situ Monitoring D.
Aging Assessment and Interim Recommendation R1 R NUREG/CR-4234 i
Phase 11 S
S E.
Review and Verification of Advanced R.S -
2 1
R2 A Letter Report 1, S, & MM Methods l
to NRR S
l F.
Test Selected Equipment g
G.
Value impact Study and Recommendations
-- L8R 3
for I, S, & MM Guidelines S
Figure B.7
REFERENCES Nuclear Plant Aging Research 1.
NUREG/CP-0036, Proceedings of the Workshop on Nuclear Power Plant Aging, November 1982, Compiled by B.E. Bader and L.A. Hanchey (SNL).
2.
NUREG/CR-3543, Survey of Operating Experiences from LERs to Identify Aging Trends, January 1984, G.A. Murphy, R.B. Gallagher, M.L. Casada and H.C. Hoy (ORNL).
3.
NUREG/CR-3818, Report of Results of Nuclear Power Plant Aging Workshops, May 1984, N.H. Clark and D.L. Berry (SNL).
4.
NUREG/CR-3819, Survey of Aged Power Plant Facilities, July 1985, J. A. Rose, R..Steele, K. G. DeWall, B. C. Cornwell (INEL).
5.
NUREG/CR-4156, Operating Experience and Aging-Seismic Assessment of Electric Motors, M. Subudhi, E. L. Burns, J. H. Taylor (BNL) (to be published).
6.
NUREG/CR-4144, Importance Ranking Based on Aging Consideration of Components Included in Probabilistic Risk Assessment, April 1985, T. Davis, A. Shafaghi, R. Kurth and F. Leverenz (PNL).
7.
NUREG/CR-4279, Aging and Service Wear of Hydraulic and Mechanical Snubbers Used in Safety-Related Piping and Components of Nuclear Power Plants, S. H. Bush, P. G. Heasier, R. E. Dodge (PNL) (to be published).
- 8.
NUREG/CR-4234, Vol 1, Aging and Service Wear of Electric Motor-0perated Valves Used in Engineered Safety-Feature Systems of Nuclear Power Plants, W. L. Greenstreet, G. A. Murphy, D. M. Eissenberg, July 1985 (0RNL).
9.
NUREG/CR-4257, Inspection, Surveillance, and Monitoring of Electrical Equipment Inside Containment of Nuclear Power Plants - with Application to Electrical Cables, S. Ahmed, S. Carfagno and G. Toman (FRC) (to be publishe'd).
10.
NUREG/CR-3385, Measures of Risk Inportance and Their Applications, July 1983, W. E. Vesely, T. C. Davis, R. S. Dennig, N. Saltos (BCL).
11.
Letter Report from G. Murphy, ORNL to J. Vora, NRC, June 5, 1985,
" Accident Precursor Events Involving Age-Related Component Degradation."
4 R-1
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BIBLIOGRAPHIC DATA SHEET NUREG-1144
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- 2. Tif LE AND S Y tT L E 3 LE AVE SLANE Nucl ea Plant Aging Research (NPAR) Program Plan 4 DATE REP @T COMPLETED fj uONT-vtAR July
/
1985
.. tut OR,,,
- D[E REPORT ISSUED B.M. Morris, J.
Vora l
July.ONT [
vEAR 1985 7 PEAPORLING ORGANelAllON NAME AN AILING ADORES $ f,ac,usele Cest, 8 PROJECTsT A5 PORK UNif NUW3ER Division of Engineer g Technology
/
Office of Nuclear Regu tory Research
. "~ Oa WNT Numa U.S. Nuclear Regulatory onsnission Washington, DC 20555
- 10. SPONSORING ORGANA 2 AT#ON N AME AND M AILING ADDR f,wAwde le Cope, Ila VPE OF REPORT Same as 7, above.
Research - Program Plan
.,E R,00 COv E R Eo,,,,,,.
12 SUPPLEMENT ARY NOFE$
.The. nuclear plant aging research described thi plan is intended to resolve issues related to the aging and service wear of equi t and systems at commercial reactor facilities and their possible impact on plant fe ty.
Emphasis has been placed on identification and characterization of the megha isms of material and component degradation during service and evaluation offneth s of inspection, surveillance, condition monitoring and maintenance as mear)t of m igating such effects. Speci fically, the goals of the program are as follows: f1) To ide tify and characterize aging and -
service wear effects which, if unchecked,[could cause gradation of structures, components, and systems and thereby impa)r plant safet (2) To identify methods of
-inspection, surveillance and monitoringe or of evaluatin residual life of structures, components, and systems, which will asfure timely detecti of significant agin'g effects prior to loss of safety function, andf(3) To evaluate the fectiveness of storage, maintenance, repair and replacement practices in mitigating he rate and extent of degradation caused by aging and ser ice wear.
- 1. muwNT AN ALvs,... RE mORos,OEsCR,PTORs g
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defeet characterization li fetime
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