ML20086C212
| ML20086C212 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1995 |
| From: | Black S, Correia R, Petrone C Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-1526, NUDOCS 9507060341 | |
| Download: ML20086C212 (44) | |
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NUREG-1526 Lessons Learned from Early Implementation of The Maintenance Rule at 3 me..3uclear Power Plants t
U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation C. D. Petrone, R. P. Correia, S.C. Black f
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9507060341 950630
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i AVAILABILITY NOTICE Availability of Reference Materials Cited in NRC Publications Most documents cited in NRC publications will be available from one of the following sources:
1.
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N NUREG-1526 e
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Lessons Learned from l
Early Implementation of The Maintenance Rule at Nine Nuclear Power Plants I
l Manuscript Completed: June 1995 Date Published: June 1995 l
C.D. Petrone, R.P. Correia, S.C. Black i
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Division of Technical Support Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
ABSTRACT This report summarizes the lessons learned did not consider operating experience from the nine pilot site visits that were throughout the industry. Although required to performed to review early implementation of do so, licensees were not monitoring at the the maintenance rule using the draft NRC system or train level the performance or Maintenance Inspection Procedure. Licensees condition for some systems used in standby followed NUMARC 93-01, " Industry service but not significant to risk. Most Guideline for Monitoring the Effectiveness of licensees had not established adequate Maintenance at Nuclear Power Plants." In monitoring of structures under the rule.
general, the licensees were thorough in Licensees established reasonable plans for determining which structures, systems, and doing periodic evaluations, balancing components (SSCs) were within the scope of unavailability and reliability, and assessing the the maintenance rule at each site. The use of eiTect of taking equipment out of ser/ ice for an expert panel was an appropriate and maintenance. However, these plans were not practical method of determining which SSCs evaluated because they had not been fully are risk significant. When setting goals, all implemented at the time of the site visits.
licensees considered safety but many licensees l
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. CONTENTS.
AB STRACT.............................................................. iii EXECUTIVE S UMMARY.................................................. vii k
ACKNOWLEDGEMENTS................................................... ix ABBREVIATION S............................. s......................... xi
. 1 INTRODUCTION....................................................... I 1.1 Objective......................................................... I 1.2 Need for the Maintenance Rule..........................,............ 1 l
1.3 Process-Oriented and Results-Oriented Rulemaking........................ 2 1.4 Description of the Maintenance Rule................................... 3 l
1.4.1 Goals and Monitoring....................................... 3 1.4.2 Effective Preventive Maintenance................................. 3 1.4ft Periodic evaluation and safety assessments......................... 4 -
1.4.4 Scope.................................................... 4 1.5 Implementation....................................................~ 4 2 LESSONS LEARNED FROM PILOT SITE VISITS............................ 7 2.1 Use ofIndustry Guideline NUMARC 93-01.............................. 7 2.2 Scoping......................................................... 7 2.3 Risk Determination...............................................
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2.4 Goal Setting, Monitoring, and Preventive Maintenance.................... 15 l
2.4_.I Categorizing SSCs in Paragraph (aXI) or (aX2).................... 15 2.4.2 Corrective Actions.......................................... 18 2.4.3 Safety Consideration in Goal Setting. :........................... 20 I
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2.4.4 Industry Operating Experience in Goal Setting..................... 21 2.4.5 Monitoring and Trending of Systems and Components............... 22 2.4.6 Monitoring and Trending of Structures........................... 24
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2.4.7 Functional Failures.......................................... 26 2.5 Periodic Evaluations............................................. 27 2.6 Balancing Unavailability and Reliability............................... 28 2.7 Plant Safety Assessments for Taking Equipment out of Service.............. 29 t
f 3 CONCLUS ION....................................................... 3 3 y
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EXECUTIVE SUMMAFY The stafflearned several lessons while visiting steam, condenser air removal, screen wash
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the nine pilot sites to review early water, generator gas, and turbine tube oil.
I implementation of the maintenance rule (the rule). These sites were visited to verify Risk Determination usability and adequacy of the draft NRC Maintenance Rule Inspection Procedure and The team found that each licensee had used a determine the strengths and weaknesses with well qualified expert panel to determine which the implementation of the rule at each site.
SSCs were risk significant. The use of an This report presents the results of these site expert panel that considers probabilistic risk visits to other licensees for their consideration assessment (PRA) insights is an appropriate during their implementation of the rule. The and practical method of determining risk major fmdings for each subject area are significance. The expert panels at most sites summarized below.
considered PRA insights using risk reduction worth, risk achievement worth, core damage Use ofIndustry Guideline frequency contribution, and Fussell-Vesely (F/V)importance measures. However, the Licensees implemented the rule using the expert panels at two sites did not receive the guidance in NUMARC 93-01, " Industry results of allimportance measures to consider Guideline for Monitoring the Effectiveness of when determining risk significance.
Maintenance at Nuclear Plants," May 1993, which the NRC endorsed in Regulatory Guide Categorizing Structures, Systems, and 1.160, " Monitoring the Effectiveness of Components in Paragraph (a)(1) or (a)(2)
Maintenance at Nuclear Power Plants,"
Revision 1, January 1995.
The process and procedures used by most licensees for categorizing SSCs under Scoping paragraph (a)(1) or (a)(2) of the rule was reasonable. However, some licensees were Most licensees were thorough in determining reluctant to place SSCs in the paragraph (a)(1) which structures, systems, and components category because having SSCs in that category (SSCs) are within the scope of the rule at their would imply their preventive maintenance sites. The licensees correctly classified most programs were ineffective.
safety-related SSCs and those non-safety-related SSCs whose failure could prevent Corrective Actions safety-related SSCs from fulfilling their safety-related function. Certain licensees incorrectly Licensees established effective corrective missed classifying a few non-safety-related action processes or programs. To implement SSCs as being within the rule. These systems the maintenance rule, most licensees had are relied upon to mitigate accidents or assigned primary responsibility for establishing transients or are used in emergency operating corrective action to the system engineers; a procedures, or their failure could cause a few licensees had assigned that responsibility reactor scram or actuation of a safety-related to an expert panel. Both approaches produced system. These systems included control room acceptable results.
annunciators, circulating water, reactor coolant pump vibration monitoring, extraction i
vii NUREG-1526
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1 Safety Consideration in Goal Setting Balancing Unavailability and Reliability Licensees established satisfactory programs for The preliminary plans established by all nine taking safety into consideration when setting licensees for balancing unavailability and goals.
reliability were reasonable. However, the team was unable to fully evaluate these activines Industry Operating Experience because these plans had not been implemented at the time of the site visits.
Many licensees' procedures did not have adequate guidance for ensuring that operating Plant Safety Assessments Before Taking experience was considered, where practical, Equipment Out of Service when establishing goals. In addition, licensees had not established a systematic and consistent Many licensees developed matrices to define method of collecting and using SSC reliability which system combinations could be allowed and availability data from other licensees when out of service at the same time. Several
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setting goals.
licensees are planning to use real time (or near-real-time) risk monitors to calculate the Monitoring and Trending of Systems and risk changes associated with the planned Components maintenance activities. Both the matrix approach and the risk monitor approach are The SSC performance or condition trending reasonable ways of assessing the effect on that was being performed by most licensees plant safety when taking equipment out of was not well coordinated and integrated with service for monitoring or preventive the goals and performance criteria established maintenance. However, the team did not under the rule.
evaluate the effectiveness of either method because neither had been fully implemented.
Monitoring and Trending of Structures Conclusion Most licensees assigned low priority to the monitoring of structures under the rule.
Upon considering the observations made l
Several incorrectly assumed that many of their during these pilot site visits, the team structures are inherently reliable. The concluded that the requirements of 10 CFR performance criteria for monitoring some 50.65, " Requirements for Monitoring the structures were not predictive and did not give Effectiveness ofMaintenance at Nuclear early warning ofdegradation.
Power Plants," can be met by using NUMARC j
93-01, " Industry Guidance for Monitoring the Periodic Evaluations Effectiveness ofMaintenance at Nuclear Power Plants," if the recommendations in this Two licensees had performed a periodic report are taken into consideration. The team
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evaluation before the site visit. The team also concluded that the performance-based I
reviewed the results of these evaluations and approach to implementing the rule is practical, found that they generally met the requirements the draft inspection procedure can be used to of the rule. At the seven other sites, the team monitor the implementation of the rule, and the reviewed the licensees' preliminary plans and existing PRA tools and models, used in procedures for performing the periodic conjunction with an expert panel, are adequate evaluation and found them to be reasonable.
for purposes of taking risk into cor ideration when implementing the rule.
NUREG-1526 viii
L ACKNOWLEDGEMENTS The authors wish to acknowledge Millard L.
George Replogle, Region III Wohl for reviewing risk determination John Whittemore, RegionIV methods and onlme mamtenance evaluations, Francis X. Talbot for evaluating plant systems Licensee Representatives for inclusion in the scope of the maintenance rule and preparing the tables. The authors also Roger Murgatroyd, Florida Power wish to acknowledge Jeffrey Main, who edited Corporation this report.
Mark I. Forsyth, Houston Power and Light f
NRC Team Members for the Nine Pilot Site Mark Ajluni, Georgia Power Corporation Visits Lewis A. Ward, Georgia Power Corporation Thomas Foley, NRR Keith A. Fry, Georgia Power Corporation Ronald Frahm Jr., NRR Thomas Bardauskas, Commonwealth Edison Wayne Scott, NRR Jon Anderson, Boston Edison Company Francis Talbot, NRR Don Hanley, Boston Edison Company Dave Nelson, NRR Jerry A, Kleam, Boston Edison Company Melvin Shannon, NRR Ron J, Zula, Carolina Power and Light Jin Chung, NRR Martin Bridges, Carolina Power and Light Ed Ford, SRI, Waterford Robert T. Biggerstaff, Carolina Power and Light Angel Coello, Spanish Nuclear Safety Council Robert Bickford, Maine Yankee Atomic i
Steven Barr, Reg. ion I Power Company James Stewart, Region I William Drake, Maine Yankee Atomic Power Herb Williams, Region I Company Tom Kenny, Region I Sammy Mooney, Entergy Operations Inc.
Tom Shedlosky, Region I Tom H. Thurmon, Entergy Operations Inc.
Paul J. Kellogg, Region II NEI Representatives Al Walker, Region III Dan J Rains Wayne Shafer, Region III Adrian Heymer Clark Vanderneit, Region Ill Ray Ng L
Tony Pietrangelo ix NUREG-1526
1 INTRODUCTION 1.1 Objective safety systems is consistent with the Commission's defense-in-depth philosophy.
l This report summarizes the lessons learned Maintenance is also important to ensure that during the pilot site visits that a team from the design assumptions and margins in the original U. S. Nuclear Regulatory Commission (NRC) design basis are maintained or at least not made from September 1994 to March 1995 to unacceptably degraded. Therefore, review early implementation of the maintenance at nuclear power plants is clearly maintenance m!e. The maintenance rule (the important in protecting the public health and rule), which was published on July 10,1991, safety.
as 10 CFR 50.65, " Requirements for The results of the Commission's Maintenance Monitoring the Effeciiveness of Maintenance at Nuclear Power Plants," will take effect on Team Inspections (MTIs) indicated that July 10,1996. These reviews were performed licensees have adequate maintenance programs at nine nuclear power plant sites that had and were improving implementation of their volunteered for early review of their programs Programs. However, some common maintenance-related weaknesses were found, for implementing the mle. The purpose of these site visits was to verify usability and such as madequate root cause analysis leading adequacy of the draft NRC Maintenance Rule to repetitive failures, lack of equipment Inspection Procedure and to determine the Performance trending, and the need for strengths and weaknesses of the consideration of plant risk in the prioritization, P anning, and scheduling of maintenance.
l implementation of the rule at each site. Other licensees should consider this information The Commission believes that the effectiveness when developing programs for implementing
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the rule. NRC inspectors may also use it while I'.namtenance must be assessed continually to venfy that key structures, systems, and evaluating licensees' implementation of the components are capable of performing their rule.
intended function. Further, licensees need to 1.2 Need for the Maintenance Rule e n5ider revisin8 Programmatic requirements where poor assessment results indicate ineffective maintenance.
In the statements of consideration for the rule, the Commission stated that such a rule is However, despite significant industry needed because proper maintenance is essential accomplishment in the areas of maintenance to plant safety and because effective program content and implementation, plant maintenance is clearly linked to safety. Good events caused by the degradation or failure of mamtenance helps limit the number of plant equipment continue to occur as a result transients and challenges to safety systems by ofinstances ofineffective maintenance.
ensuring operability, availability, and reliabih,ty Additionally, operational events have been of safety equipment. Good maintenance is exacerbated by, or resulted from, plant important in ensuring that failures of equipment being unavailable because of main-structures, systems, and components (SSCs) tenance activities. Most existing requirements other than safety-related SSCs that could ini-and industry maintenance initiatives do not call tiate or adversely affect a transient or accident for licensees to routinely assess the availability are numnuzed. Mimm;zmg challenges t of safety significant structures, systems, and 1
f components. These events and circumstances tenance activities. The rule provides for
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attest to the need to continually assess the continued emphasis of the defense-in-depth results of maintenance effectiveness since, principle by including select balance-of-plant together with equipment reliability, equipment (BOP) SSCs, integrates risk consideration into availability is an important measure of the maintenance process, establishes an maintenance effectiveness.
enhanced regulatory basis for inspection and enforcement of BOP maintenance-related The Commission also recognizes its need to issues, and gives a strengthened regulatory broaden its capability to take timely basis for ensuring that the progress achieved is enforcement action where maintenance sustained in the future.
I activities fail to give reasonable assurance that safety-significant SSCs are capable of 1.3 Process-Oriented and Results-performing their intended function.
Oriented Rulemaking l
Additionally, the Commission concluded that it is necessary for NRC to include requirements Although they do not appear to have a formal for corrective action to address instances of defimtion. the termsprocess-oriented (or ineffective maintenance, and for licensees t programmatic, or prescriptive) and results-use the results ofmonitoring and assessment to oriented (or results-based, or performance-improve mamtenance programs.
based) are increasingly being used to describe "8 * **
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vities. A process-The Commission also had several other oriented rule, the traditional approach for most reasons for finding the need for a rule requ..inng that the effectiveness ofma, tenance be mom-rulemaking, includes detailed requirements or m
tored. One of these reasons is that the instructions. The advantage to such mies is that they are easier to enforce because the Commission's current regulations, regulatory guidance, and licensing practice do not clearly requirements for implementing the rule are define the Commission's expectations for delineated in greater detail than would be the ensuring the continued effectiveness of case for results-oriented rules. Using a maintenance programs at nuclear power plants.
process-oriented rule, licensees generally have Another is that industry has no guidance a clearer idea of what they need to do to regarding the monitoring of mamtenance implement the requirements of the rule, and effectiveness.
NRC inspectors have a clearer idea of what to inspect. The disadvantage to such rules is that Requirements and guidance for monitoring they tend to be inflexible and thus may prevent maintenance effectiveness and for taking licensees from using the most eflicient and corrective action when maintenance is effective means ofimplementing the rule. Two inefTective should enhance the Commission's examples of process-oriented rules are Appendices J (Primary Containment Leakage capability to take timely e.nd effective action against licensees with inadequate or poorly Testing) and R (Fire Protection Program for conducted maintenance to ensure prompt Nuclear Power Facilities) to 10 CFR Part 50.8 l
resumption of effective maintenance activities.
i On July 10,1991, the Commission published 8 Although Appendix J rule is a good example of the final rule,10 CFR 50.65, in the Federal a process-oriented rule, the NRC is revising this mle Register. When the rule takes effect on July to add a results-oriented option permitting licensees l
10,1996, it will require all nuclear power plant the ficxibility to adjust leak rate test frequencies licensees to monitor the efTectiveness of main-based on performance.
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These rules contain detailed requirements for burden on licensees to develop the supporting test frequency, test pressures, training, and details needed to implement the mle.
record keeping.
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1.4 Description of the Maintenance A results-oriented (or results-based or Rule performance-based) rule describes, in general terms, the results expected while leaving the Section (a) of the rule contains mest ofits details of achieving those results up to the detailed technical requirements; paragraph (b) licensee. Such a rule has the advantage of defines the scope of structures, systems, and allowing the licensee to devise the most components within the rule; and paragraph (c) effective and eflicient means of achieving the states that the licensees shall implement the results described in the mle. It also allows mle no later than July 10,1996. Section (a) licensee to consider safety or risk significance consists of paragraphs (1), (2), and (3).
when developmg its programs. The disadvantage of a results-oriented rule is that it 1.4.1 Goals and Monitoring may be difficult to enforce because the requirements for compliance may be less Paragraph (a)(1) of the rule requires the clearly defined than the requirements of a operator of each power reactor to set goals process-oriented rule. The maintenance rule, and to monitor the performance or condition 10 CFR 50.65, is a results-oriented rule.2 of SSCs in a manner sufficient to give Although licensees clearly prefer results-reasonable assurance that those SSCs are oriented regulations over process-oriented capable of performing their intended functions.
regulations, such regulations lack of detail as The rule states the goals must be became apparent during the development of commensurate with safety and where practical regulatory guidance for the rule. The Nuclear take into account industry-wide operating Management and Resources Council, Inc, experience. The rule also requires operators to (NUMARC) now the Nuclear Energy Institute take appropriate corrective action when the (NEI), representing the industry, asked that the performance or condition of an SSC does not inspection procedure (which is normally meet established goals. In keeping with the developed after the regulatory guidance has non-prescriptive intent of the rule, the licensee been issued) be prepared early and given them establishes the goals, not the NRC, to use while preparing the industry guidance document. They wanted to use the inspection 1.4.2 Effective Preventive Maintenance procedure to address details, not in the mle itself. Results-oriented rules place a greater Paragraph (a)(2) of the rule establishes an alternative approach to the monitoring regime required by paragraph (a)(1) of the rule. The NRC recognizes in this approach that, in 2 Although the maintenance rule has been certain cases, the performance or condition of described as a results-oriented rule,it prescribes SSCs could be effectively controlled by doing l
certain specific programmatic actions. For example, paragraph (a)(3) requires that a periodic evaluation be performed and that the effect on taal plant risk by monitoring against goals.
be considered before removing equipment from service for maintenance. Therefore, while the maintenance rule is much more results-oriented and less programmatic than most other existing rules, it has certain process-oriented elements.
f 1.4.3 Periodic evaluation and safety this type of situation might be taking one train assessments of a safety system out of service while one of the alternate sources of power supply for the Paragraph (a)(3) of the rule requires that redundant train is aisc out of service.
A performance-and condition-monitoring Although the technical specification operability activities and associated goals and preventive requirements address this concern, the NRC l
maintenance activities be evaluated at least staff recently found vulnerabilities not every refueling cycle, provided the interval addressed by the technical specifications. The between evaluations does not exceed 24 requirements of this paragraph of the rule months. This paragraph will require licensees extend beyond those of the technical to syaematically review activities under specifications.
paragraphs (a)(1) and (a)(2) of the rule and to adjust those activities where needed. These 1.4.4 Scope evaluations are required by the rule to take into account, where practical, industry-wide Paragraph (b) of the rule defines those SSCs q
operating experience.
that must be included within the scope of the rule. They include all safety-related SSCs and Paragraph (a)(3) of the rule also requires that those non-safety-related SSCs (1) that are adjustments be made, where necessary, to relied upon to mitigate accidents or transients ensure that the objective of preventing failures or are used in emergency operating procedures of SSCs through maintenance is appropriately (EOPs), (2) whose failure could prevent balanced against the objective of minimizing safety related SSCs from fulfilling their the time SSCs are unavailable because of intended functions, or (3) whose failure could monitoring or preventive maintenance. This cause a scram or safety system actuation.
requirement recognizes that performing monitoring or preventive maintenance often 1.5 Implementation requires that the SSCs be taken out of service, rendering them unavailable for operation. The To develop implementation guidance, the NRC higher reliability gained by increased moni-and NUMARC established parallel steering toring or preventive maintenance could and working groups. In June 1993, the NRC decrease availability, and possibly impair published Regulatory Guide 1.160, safety.
" Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," which endorsed Paragraph (a)(3) of the rule also states that in NUMARC 93-01, " Industry Guideline for performing monitoring and preventive Monitoring the Effectiveness ofMaintenance maintenance activities, an assessment of the at Nuclear Power Plants," May 1993.
total plant equipment that is out of senice NUMARC sponsored two industry workshops should be considered to determine the overall in August 1993 to educate the industry on the effect on performance of safety functions. To methods stated in NUMARC 93-01 for address this element of the rule, licensees implementing the rule. The NRC staff should continually evaluate whether voluntary participated in these workshops.
I removal of equipment from service to perform monitoring and preventive maintenance The NRC staff developed a draft inspection activities may place the plant in a less safe procedure to verify implementation of the rule.
condition, especially if other supponive On March 31,1994, NRC sponsored a public equipment is out of service. An example of workshop in Rockville, Maryland, where NUREG-1526 4
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f members of the public and the nuclear industry South Texas, and Crystal River. The NRC could ask questions about the inspection review teams included representatives from the
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procedure. At the workshop, NRC explained Quality Assurance and Maintenance Branch its expectations about implementation of the and the Probabilistic Safety Assessment rule.
Branch from the Office of Nuclear Reactor Regulation (NRR), representatives from the Beginning in September 1994 and ending in Trends and Patterns Analysis Branch from the March 1995, the NRC staff visited nine pilot Office for Analysis and Evaluation of
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sites to validate the draft inspection procedure.
Operational Data (AEOD), and regional The licensees for these plants had voluntarily inspectors. This report summarizes the lessons implemented most of the requirements of the learned from the site visits for the benefit of all rule, which does not become effective until licensees and NRC inspectors and for the staff July 10,1996. NRC coordinated with NEIin to use in completing the inspection guidance.
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selecting the sites: Grand Gulf, Maine Yankee, Shearon Harris, Pilgrim, Byron, Hatch, Vogtle, i
2 LESSONS LEARNED FROM PILOT SITE VISITS The NRC staff documented their findings, majority of SSCs the team believed should be conclusions, and recommendations in letters to within scope. However, the following are the individual licensees following each site examples of excluded SSCs from various sites visit. These reports addressed each ofeach that the team believed should be within the requirement of the rule, such as scoping and scope of the rule at that particular facility:
risk determination, as a separate topic.
- 1. Control room annunciators. The 2.1 Use ofIndustry Guideline justification for excluding control room NUMARC 93-01 annunciators, which constitute a non-safety-related system used in EOPs, from The guidance in NUMARC 93-01 was the scope of the rule did not follow the J
l endorsed in Regulatory Guide 1.160 as guidance in paragraph 8.2.1.3 of containing acceptable methods of NUMARC 93-01, which allows SSCs implementing the rule. All nine licensees used covered by paragraph 50.65(b)(2)(i) to be t
NUMARC 93-01 for implementing the rule.
excluded if they do not add "significant Eight licensees took minor exceptions that the value to the mitigation function." The NRC review team reviewed and found licensee based its decision on the fact that the annunciators are redundant to other acceptable. One licensee took major exceptions that the team reviewed and also safety-related instruments such as gauges found acceptable.
and chart recorders, which are considered the primary instruments used in EOPs.
2.2 Scoping However, the annunciators add significant value to the mitigation function because Before visiting each site, the team reviewed they will often give the first warning of an the plant final safety analysis report (FSAR),
ut-of-tolerance condition or developing accident. The team discussed this concern EOPs, and Individual Plant Evaluation (IPE) with several of the licensee's control room insights to select sample SSCs that the team believed were within the scope of the rule.
perators, who confirmed that control r m annunciators often gave them the The team used this sample list to determine whether the licensee had classified the required first warning of a problem. The team SSCs as being within the scope as defined in concluded that those annunciators, which paragraph (b) of the rule.
are used in the EOPs, do add significant value to the mitigation function and
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At each site, the team reviewed the process therefore are within the scope of the rule.
and procedures used by the licensee to determine which SSCs were to be included
- 2. Site grounding system. The licensee's documentation states that the site from the scope of the rule and which were i
excluded.
grounding system is a "non-safety-related SSC whose failure causes trip / power Findings reduction." Therefore, the site grounding system should be included within the scope Most licensees followed the scoping process of paragraph 50.65(b)(2)(iii) of the rule.
I described in NUMARC 93-01 and included the The licensee excluded this system from the l
scope of the rule because "the plant has not circulating water system did not meet the experienced significant problems with criteria of paragraph (b)(2)(iii) of the rule.
system in the past." The team believes that the licensee has misinterpreted paragraph The team disagreed with this position.
(b)(2)(iii) of the rule, which states that Paragraph (b)(2)(iii) of the mle states that non-safety-related SSCs "whose failure non-safety-related SSCs whose failure couldcause a reactor scram or actuation of could cause a reactor scram or safety a safety-related system" (emphasis added]
system actuation should be included within shall be included within the scope of the the scope of the rule. Nothing in the rule i
mle. The licensee has interpreted this itself, the statements of consideration, requirement to mean has caused rather Regulatory Guide 1.160, or NUMARC 93-than couldcause. The team believes that 01, indicates that the reliability should be this interpretation is incorrect.
considered when determining whether a system is under the scope of the rule. The
- 3. Circulating water system. Paragraph phrase beginnning with whosefailure
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(b)(2)(iii) of the mle requires that all means that the system is assumed to fail.
non-safety-related SSCs whose failure The only question is whether or not the couldcause a reactor scram or the assumed failure could cause a subsequent actuation of a safety-related system be reactor scram or safety system actuation.'
included within the scope of the mle. The team believes that the circulating water Redundant trains The licensee also made system falls under this provision since its the argument that since the circulating failure could cause a turbine trip and water system has four trains (each subsequent reactor scram. The licensee's consisting of screens, pumps, and piping) it representative stated that they had would be unreasonable to assume that the i
considered including the circulating water whole system could fail. If only one train system under the scope but had decided failed, the plant could continue operation, against it for several reasons. The team or take action to reduce power and avoid a members discussed each of these reasons reactor scram or safety system actuation.
with the licensee's representatives and stated the team's views on each of these The team disagreed with this position. A reasons. A summary of the issues follows.
failure of the system must be assumed since it would be the worst case scenario.
High reliability. The licensee stated that the design of the circulating water r.ystem 3 Paragraph (b)(2)(ii) of the rule requires that makes it very reliable. The cooling pond is non-safety-related structures and components man-made and is therefore not subject t "whose failure could prevent safety-related d
the causes of fouling (debns, plant, or structures, systems, and components from fulfilling animal life) that plague natural sources of their safety-related function" be included within the cooling water at other reactor sites. They scope of the rule. Similar to the argument for stated that reliability this is evidenced by paragraph (b)(2)(iii), the words whosefailure mean the fact that the site has never experienced that the failure is assumed. The criteria are only a loss of circulating water that resulted in a intended to determme if the assumed failure of the reactor scram or safety system actuation.
system could prevent a safety-related system from Therefore, they concluded that the fulfilling its safety related function. Therefore, the system is assigned a reliability of zero for this analysis because it is assumed to fail.
The licensee's approach of assuming a train Hypotheticalfailures. The licensee stated failure is not conservative and does not that a failure of the circulating water meet the intent of paragraph (b)(2)(iii).
system was a hypothetical failure because it had not happened at their site and was not t
Operator action The licensee made the described in the safety analysis report or argument that in the unlikely event that the any other analysis. Therefore, they believed entire circulating water system failed, the that they were not required to consider reactor operators would be able to such a failure under the guidance in recognize the event in sufficient time to paragraph 8.2.1.5 ofNUMARC 93-01.
take mitigating actions that would prevent a reactor scram or safety system actuation.
The team disagreed with the position taken by the licensee. Paragraph 8.2.1.5 of The team disagreed with this position.
NUMARC 93-01 states that "[t]he Operator action, or the lack ofit, is not a determination of hypothetical failures that criterion to be considered when making a could result from system interdependencies scoping determination under 10 CFR but have not been previously experienced 50.65(b). Operator actions are not is not required." In the section "High discussed as a criterion in either the mle, Reliability" of NUMARC 93-01, the the statements of consideration, authors state the fact that the circulating Regulatory Guide 1.160, or NUMARC 93-water system has not failed in the past does 01.
not make this a hypothetical failure. If the circulating water system does fail, the Directly cause. Paragraph (b)(2)(iii) of the interactions that could result in a reactor t
rule requires that the scope of the rule scram are not hypothetical; rather they are include all non-safety-related SSCs whose the normal expected sequence ofoperation failure could cause a reactor scram or the of the plant. A loss or reduction in actuation of a safety-related system. The circulating water would require a turbine licensee interpreted this criterion to mean runback or trip, which could result in a that only those SSCs that directly cause a reactor scram. The team believes that the reactor scram should be considered.
hypotheticalfailures described in Therefore, a loss of circulating water that NUMARC 93-01 refer to two or more caused a turbine trip and subsequently events (not previously experienced or resulted in a reactor scram should not analyzed) that occur simultaneously and come under the scope of the rule because it result in a reactor scram or safety would not be a direct trip.
actuation.'
l The team disagreed that couldcause l
Other examples. Other examples of SSCs f
should be interpreted to mean directly that the team believed should have been cause. Nothing in the rule itself, the within the scope of the mle at particular statements of consideration, Regulatory sites follow: shield walls that separate the Guide 1.160, or NUMARC 93-01, indicates that only those non-safety-related SSCs that directly cause a reactor scram or
- Some of these issues were discussed with other i
safety system actuation should be included licensees during previous site visits. This discussion within the scope of the rule. The licensee's is additional guidance to alllicensees. The team use of directly cause is not a conservative will recommend revising the implementing guidance interpretation of the rule.
to further clarify this issue.
I station startup transformers, plant in practice. Instead of using this criterion, the computer, heat tracing and freeze licensee included in the scope those protection, reactor coolant pump vibration non-safety-related systems considered to be monitoring, lightning protection, cathodic "significant contributors to the mitigation protection systems, extraction steam, strategy of the procedures." The licensee condenser air removal, screen wash water, defined significant contributors as those gland steam, gland seal water, generator
" systems whose failure would affect the gas, turbine lube oil, and turbine generator outcome of successful completion of the i
seal oil.
procedure or cause the user to transition to another procedure." The team concluded that One licensee used a different interpretation of the licensee's alternative criterion for the guidance contained in NUMARC 93-01 for identifying SSCs in EOPs is reasonable and determining which non-safety-related SSCs meets the intent of the rule.
are relied upon to mitigate accidents or transients or are used in plant EOPs under Table 1 is a summary of SSCs defined by the paragraph (b)(2)(i) of the rule. NUMARC 93-licensee as being within the scope of the rule at 01, paragraph 8.2.1.3, states that only those each site and any additional SSCs found by the SSCs that " add significant value to the team. The team found considerable variation mitigation function of an EOP by providing the even among similar plants in the numbers of total or a significant fraction of the total SSCs defined for each plant and considerable functional ability required to mitigate core variation in the numbers of SSCs identified as damage or radioactive release" should be being within the scope of the rule. The included within the scope of the rule. In numbers in this table are for general attempting to evaluate which nonsafety information and should not be used for judging systems should be included under this the acceptability of the scoping activities at provision of the rule, the licensee found other sites.
"significant fraction" a difficult criterion to use NUREG-1526 10
Table 1. Structures, systems, and components under the Scope of the Maintenance Rule' BWR/3 BWR/4 BWR/6 WEST 3 Loop WEST 4 Imp WEST 4 Imp WEST 4 loop CE B&W Total number of 102 131 341 205 176 194 112 160 137 SSCs Number of 67 86 127' 115' 103 100' 76 -
'110' 90' 5
7 SSCs within (66%)
(66%)
(37%)
(56%)
. (59%)
(52%)
(68%)
(69%)
(66%)
scope Number of n.a.20 6
16 15 6
17 23 32'
~ 7' structures (only) within z
scope NRC-identified None None l'
4' 15 l'
3' l'
15' SSCs requinng reevaluation C
1.
The data on this table is based on a review of the licensee's documentation for rule implementation at the time ofeach NRC site visit and is sutject to change 2.
Three licensees were still evaluating structures under scope at the time of the NRC site visits ( i.e., These include the licensees for utility data in columns one, eight a,nd nine)r, therefore, the number of structures and the total number of SSCs under scope may change. All other licensees included structures under scope.
3.
The licensee found 126 SSCs. The NRC.--- =
k-1 that control room annunciators be added.
4.
The bcensee found 111 SSCs. The NRC w.._.i.: that the site grounding system, the plant computer, heat tracing and freeze protection and the reactor coolant pump vibration morntor be added to the scope.
5.
The licensee found 102 SSCs. The NRC.~..~..' : that the circulatmg water system be added to the scope.
6.
The licensee found 82 out of 151 plant systems and 17 out of 43 plant structures within scope. The NRC tecommended that the extraction seenm system be added to the scope.
7.
The licensez found 73 SSCs. The NRC recommended that the lighting protection, site grounding and cathodic protection be added to the scope.
8.
The licensee found 109 SSCs under the scope of the rule however,the NRC recommended that one adshtional structure, the shield well around the sonstup ^. - '
.._,be added to the scope.
O 9.
The licensee found 75 SSCs. The NRC.------
' ' that the so _
,; water, extraction steam, ccs : ow air removal, screen wash water, gland steam, gland esel water,
'^
G generator gas, turbme tube oil, and turbmc generator seal oil systems be added to the scope. The licensee identified the reactor contamment as the only structure that is under scope and being snonitored. The licensee considers the vernamung structures to be inherently reliable. The NRC recommended that 6 =&ama int structures 6.e.,the a suihary buildeg, N*
control complex, w~ip.-, diesel generstar building, intermediate buildmg, NSSW intake structure, and the emergency feedwater tank enclosure) be added to the scope.
- 10. Utility cxmtmumg evaluation at the time of site visit.
,l
i Conclusion 2.3 Risk Determination l
The scoping at each site was thorough. The The rule requires that goals be established licensees correctly classified most safety-commensurate with safety. To implement the related SSCs (paragraph (b)(1) of the rule) and mle in accordance with NUMARC 93-01, the those non-safety-related SSCs whose failure licensee must do a risk (or safety) could prevent safety-related SSCs from determination for all SSCs within the scope of fulfilling their safety-related function the rule. This risk determination would then (paragraph (b)(2)(ii) of the rule). The team be considered when setting goals and believes the licensees should have included monitoring under paragraph (a)(1) of the rule several other non-safety-related SSCs within and when establishing performance criteria the scope of rule: those relied upon to mitigate under paragraph (a)(2). The risk accidents or transients, those used in EOPs determination method recommended in (paragraph (b)(2)(i) of the rule), and those NUMARC 93-01 involves the use of an expert whose failure could cause a reactor scram or panel using the Delphi method of actuation of a safety-related system (paragraph NUREG/CR-5424, supplemented by (b)(2)(iii) of the mie). The number of SSCs in probabilistic risk (or safety) assessment (PRA) this category at each site follows: 0 SSCs at 2 or IPE insights, to find risk-significant SSCs.
sites,1 SSC at each of 4 sites,3 SSCs at 1 These PRA or IPE insights can include risk site,4 SSCs at I site, and 15 SSCs at I site.
reduction worth (RRW), risk achievement Recommendations worth (RAW), and core damage frequency contribution (CDF).
- 1. Do not use the following reasons for Findings excluding SSCs from the scope of the mie because they do not address the criteria in The team found that all licensees used an Paragraph (b) of the rule, expert panel (or a working group) to The SSC is very reliable, m. herently determine risk significance. These expert reliable, or has never failed at this site.
panels considered PRA or IPE insights using the methods described in NUMARC 93-01 Redundant trains will prevent the although with variation. Not alllicensees took system from every completely failing.
RRW, RAW, and CDF into consideration.
i One h,censee cons,dered only CDF and not i
Operator actions will prevent the RRW or RAW. Another licensee considered j
failure of the system from causing a CDF and RAW but not RRW. Several scram.
licensees considered the Fussell-Vesely (F/V) importance measure in addition to CDF, c
The failure of the system will not RAW, and RRW.
directly cause a scram.
The team found that licensees' PRA experts
)
- 2. Review scoping determinations to ensure were very knowledgeable and were aware of that no SSCs were excluded from the the limitations of the use of PRA insights. One l
scope of the rule without adequate of these limitations is that all risk-important i
l justification.
systems are not necessarily modeled in a PRA.
Improvements can also be made in databases, i
success criteria (which affect accident NUREG-1526 12 l
i A
I sequence emphasis), and human reliability the expert panel a permanent part of their rule analyses. The team found an expert panel was program. The team believes that those necessary to compensate for the limitations licensees who do not have a permanent expert and assumptions inherent in a PRA and to add panel will need to reconstitute the expert panel a perspective of experience to the risk in the future to revise these risk determinations determination process. The team also found as the plant is modified or when the PRA is that, although CDF, RRW, RAW, and F/V all revised.
gave useful insights, none was indispensable as long as the results were reviewed and Six of the nine licensees plan to update their evaluated by a qualified expert panel.
PRA using plant-specific reliability and availability data to maintain a living PRA. The The team interviewed members of the expert intervals for these updates are tentative and panel at each site and found that the panel vary from one year to three years, or are members were knowledgeable and experienced undetermined. The remaining three licensees and met the standards recommended in do not plan to update their PRAs routinely to NUMARC 93-01. The expert panels made incorporate plant-specific reliability and risk-significant determinations as availability data. They did, however, state that recommended in NUMARC 93-01. Those at they would evaluate the effect of any major several of the sites participated in other plant modifications on PRA models, results, maintenance activities such as scoping, and conclusions and update them if necessary.
establishing performance criteria and goals, determining when SSCs should be moved from The staff at the last few sites visited were more paragraph (a)(1) to (a)(2) and from paragraph aware of the value of time-structured PRA-(a)(2) to (a)(1), reviewing corrective actions, determined core damage frequency profiles.
and doing the periodic evaluation required by These licensees had very strong PRA expertise paragraph (a)(3) of the rule. However, some and benefitted from the lessons learned from licensees considered the expert panel to be a the site visits. The team believes that all temporary organization and the performance licensees should share information and ideas of the risk determinations to be a one-time among themselves.
activity. Other licensees, especially those who Table 2 summarizes the number of SSCs that have decided to have their expert panel participate in other rule activities, have made were determined to be risk significant, and the methods used at each site.5
)
5 The team found considerable variation, even for reactors of similar type, in the numbers of SSCs defined for each plant and a considerable variation in the numbers of SSCs determined to be risk significant. The numbers in this table are for general information and should not be used for judging the acceptability of maintenance rule activities at other sites.
13 NUREG-1526 n
Table 2. Risk i 2 =^ structures, systems, and wusyws:s and risk determination methods' i
~
CE _.
'BAW j
BWR/3 BWR/4 BWR/6 WEST 3 Imop WEST 4 Imap
. WEST 4 Lag WEST 4 Imep l
Numbur af59Cs 67 86 127 113 103 100
- 76 110 90 h suure c:
N l
0%
Num6er errisk-25 (37 %)
41 (48 %)
24 (19 %)
44(38 %)
' 41(40%)
23 (21 %)
22 (29%).
27(25%).
17 (19 %)
W
.i l
Riskegam6cusa Utihty AE structures All serudures P= rear Reactor Reader Reactor 28 P= rear i
serusesses evalmassig are inherently are isdisrently contemuness; all coreanimisma, coneannnient I
retsable reliebt?
coher structures utilityi udieresslyreliable
. t living PRA Yet Updmee Yes,3-year No No Yes,Updsee Yes,3-year Yes, Updmee No Yes,Updmee (ysefuo) and frogmency updsee ievery updsee fregnancy fregnancy '
fragmency W fregusary
==dsesen==.d augmency refuelins cycle undesramand evey reassimis cycle Risk EPDe@i EP Ftoomus IPE EP Delphi EP Process,IMs EP Delphi EP Delphi EP Process, PRT Working EPDelphi 1 diesemansemas preessa,IMs RISKMAN process,IMs (RAW. CDF, proass,IMs precoms, PRT saAware,IMs youp,IMs praesus,lMs sh (RRW, RAW, seAware,IMs (RAW, contrik)
soeware,IMs (RAW, RRW, (RAW,CDF (RAW, RRW)
A F/V,)
(RAW, RRW, RRW,CDF (RAW,CDF F/V) cemenh)
CDFemanh) comerik) casarik)
Online
- CAFTA, C 1 C - '.
PRa Online ORAM miserin RMQS and PRA prosm6me PSAM risk
-- isk RMos and eg ipeners008 noseris, RAW -
condiguration
- PRA OSPRE seAware for esking
==== mar r
evahsessan EOOS noserix renlung numerix procedure SSCs005 soAnsure l
3 mieheds' saA re.
==fsey====nor i
1.
The data in this table is based on a review of the licensee's duci i.ciitation for rule implementation at the time of each NRC site visit and is subject to change.
2.
Acronyms for risk determination and evaluation: IM (importance measure), ORAM (outage risk assessment and management), CAFTA (computer-sided fault tree analysis), PSAM (probabilistic safety assessment monitor), PRT (probabilistic risk tree), RMQS (risk management query system) EOOS (equipment out of -
service), OOS (out of service), OSPRE (operational safety predictor), F/V (Fussell-Vesely importance), RAW (risk nimi-t worth), RRW (risk reduction worth), CDF (core damage fm.m.cf,in accord with NUMARC 93-01, the utility defined cut sets that account for 90 percent of the overall CDF contribution),
e and EP (expert panel).
i 5
___,-_m m
mm h.
sm m...
m.----
_,r--.--_.,.~rme.
.m-
...i
..s..mm
_._.cw.__.__m,._____
,.*i
. C=cir si=s performance cf the periodic evaluation
- 1. The methods used to establish risk significance met the intent of the rule and
- 6. Reevaluate risk significance determinations L
the guidance in NUMARC 93-01.
whenever the plant design is modified, the PRA is updated, or new insights become
- 2. The risk determination process at each site available from configuration management
- gave reasonable results.
reviews.
i I
- 3. The use of an expert panel to consider 2.4 Goal Setting, Monitoring, and PRA or IPE insights is an appropriate and Preventive Maintenance practical method of deternurung risk signWicance The team reviewed program documents and
- 4. The expert panel members at each site records at each site to evaluate the process l
were knowledgeable and experienced and established to set goals and monitor under i
met the standards recommended in Paragraph (a)(1) of the rule and to verify that Preventive maintenance was effective under NUMARC 93-01.
3 paragraph (a)(2) of the rule. The team also
- 5. The participation of the expert panelin discussed the program with plant staff. At other rule activities at certain sites is a each site, the team selected a sample of strength.
systems that were categorized under paragraphs (a)(1) and (a)(2) for further review.
Recommendations i
2.4.1 Categorizing SSCs in Paragraph
- 1. Use the process described in NUMARC (a)(1) or (a)(2) l l
93-01 which makes use of an expert panel for making risk determinations.
Regulatory Guide 1.160 and NUMARC 93-01 state that SSCs be subject to goal setting and
RAW, F/V, and any other methods to whenever performance criteria are exceeded or I
compensate for their limitations.
repetitive maintenance-preventible functional failures (MPFFs) occur.
i
- 3. Consider using other calculational methods i
such as Fussell-Vesely, Birnbaum, and Findings others in addition to CDF, RHR, and l
RAW.
The team reviewed a sample of systems at I
each site that were categorized under
- 4. Establish the expert panel as a permanent paragraph (a)(2) of the rule to determine if l
part of the licensee's organization.
they should have been categorized under l
paragraph (a)(1), where they would have been
- 5. Consider using the expert panel to assist in subject to goal setting and monitoring. At 1
making decisions on other aspects of eight of the nine sites, the team did not find l.
implementing the mle such as scoping, the any SSCs that should have been categorized l
establishment of performance criteria and under paragraph (a)(1) of the rule. At one site j
goals, the determination of when SSCs where the licensee had not categorized the salt should be moved from paragraph (a)(1) to service water system (SSW), the team i
(a)(2) and from paragraph (a)(2) to (a)(1),
recommended that it be categorized as a the review of corrective actions, and the paragraph (a)(1) system.
l l
15 NUREG-1526 1
l r
Very few SSCs were categ:rized under.
stages ofimplementing the rule and thus may 1
paragraph (a)(1) at any of the sites. Table 3 assign more SSCs to the paragraph (a)(1) presents the numbers of SSCs in each category category in the future. However, licensees at each site.' Licensees are still in the early may be reluctant to place SSCs in the paragraph (a)(1) category because having numerous SSCs in the paragraph (a)(1)
' The team found considerable variation, even category might indicate to the NRC or licensee for reactors of similar type, in the numbers of SSCs management that their preventive maintensnce
{
defined for each plant and in the numbers of SSCs placed in the (a)(1) category. The numbers in this Program is not effective.
table are for general information and should not be used forjudging the acceptability of the maintenance d
rule activities at other sites.
1 l
NUREG-1526 16
.9
..e Table 3. Structures, systems, and components categorized under paragraphs (aXI) and (aX2)'
d Paragraph BWR/3 BWR/4 BWRE>
WEST 3 loop WEST 4 loop WEST 4 Loop WEST 4 Imop CE B&W (aXI) 18 15 4*
6' 3'
'l' 5'
5' 3"
(aX2) 66 85 123 109 100 99 71 105 87 1.
The data on this table is based on a review oflicensee's documentation for rule implementation at the time of each site visit and is subject to change.
- 2. At the time of the NRC site visit, the licensee was considenng addmg the salt service water (SSW) system to paragraph (aXI).
- 3. The only SSC categonzed under paragraph (aXI) was the post-accident sampling system; hu-w, the utility was st21 evalustag the performan-of SSCs to determme if other SSCs should be placed under the paragraph (aXI) category 4.
The SSCs categonzed under paragraph (aXI) include the residual heat removal system, the service water system, contamment insegnty and the ESF1 switch gear room coolers
- 5. The SSCs categorized under paragraph (aXI) include the turbme-dnven auxiliary feedwater pump, the LK-16 circuit breaker, the BIF butterfly i
G valves, the "B" emergency diesel generator, the reactor cavity semis, and the "A" heater drain pump motor.
6.
The SSCs categonzed under paragraph (aXI) include the auxiliary feedwater system, the emergency diesel generators, and the solid state pre nenn-n system (i.e.,7300 process support system).
- 7. The reactor coolant system was the only system categonzed under paragraph (aXI) of the rule.
- 8. The SSCs categorized under paragraph (aXI) include the control rod drive system circuit cards,4 kv cucuit breakers,125 vde cucuit breakers, steam generator power-operated relief valves (PORVs) and pressurizer PORVs.
j
- 9. The SSCs categonmed under paragraph (aXI) include the contamment control air system, the condensate system, the heater drain system, the service water system, and the cuculating water system.
l
- 10. The SSCs categonzed under paragraph (aXI) include the emergency diesel generators, the instrument air system and the demmerahzad water j
system.
e C;
-g
-4
._,,-...-,.,, _.-,. - - - - -. _, -. ~... _ _. -. _. - ~. _ -... _.._
... _ -. _... -... -.. ~. - -,. _ - -.
The methods described in NUMARC 93-01 (a)(1). Failure to place the SSC under assume that the performance or condition of paragraph (a)(1) when preventive maintenance most SSCs at most sites is adequately has been shown to be ineffective would be a controlled through preventive maintenance and violation of the rule.
therefore should, at least initially, be placed in category (a)(2), where they are monitored Several licensees' procedures did not clearly l
exP ain the intended use of paragraph (a)(1) of against performance criteria. Only those SSCs that exceed their performance criteria, or the rule. The team recommended to these experienced repetitive maintenance preventible licensees that they review, and if necessary functional failures are placed in the paragraph revise, their procedures to clarify the intent of (a)(1) category, where they are monitored Paragraph (a)(1) of the rule and to ensure that against goals. Therefore, using the NUMARC SSCs are placed in that category whenever 93-01 guidance, category (a)(1) could be used adequate preventive maintenance can no as a tool to focus attention on those SSCs that longer be demonstrated.
need to be monitored more closely and does not indicate maintenance program Conclusion effectiveness. While using paragraph (a)(1)in this way is an acceptable approach for The process and procedures for categorizing SSCs m paragraph (a)(1) or (a)(2) of the rule implementing the rule, the team believes that wem reasonah Howner, some licensees an approach that places most SSCs in the were reluctant to place SSCs m the (a)(1) paragraph (a)(1) category and places in category.
category (a)(2) only a few SSCs whose performance or condition is being effectively Recommendations controlled through the performance of effective preventive maintenance, would also
- 1. Review, and if necessary, revise meet the intent of the rule.
procedures to clarify the criteria for determining when goal setting under The team assured the licensees' representatives paragraph (a)(1)is required and to that the NRC staff would not consider the emphasize that the conservative approach placement of SSCs in the paragraph (a)(1) to implementing the rule would be to category as an indicator of a poor maintenance categorize an SSC under paragraph (a)(1) program nor would it be used in determining whenever there was any doubt if the the grade m the maintenance area of the performance criteria had been met or a Systematic Assessment of Licensee repetitive maintenance preventible Performance. The team also cautioned functional failure had occurred.
licensee managers that they should not view the number of SSCs in the paragraph (a)(1)
- 2. The number of SSCs in the paragraph category as an indicator of performance, since (a)(1) category should not be used as an l
it might inhibit their staff members from indicator of a poor maintenance program.
i placing an SSC under paragraph (a)(1) when a performance criterion was exceeded or a 2.4.2 Corrective Actions repetitive maintenance preventible functional failure had occurred. If a licensee is not certain Paragraph (a)(1) of the rule states that whether or not an SSC should be categorized appropriate corrective action shall be taken in paragraph (a)(1) or (a)(2), the conservative when the performance or condition of an SSC approach is to place the SSC in the paragraph does not meet established goals.
NUREG-1526 18 a
Findings system engineer had thoroughly reviewed past performance and industry operating experience Many licensees have assigned the task of to determine appropriate corrective actions.
determining the root cause and developing These corrective actions included unclogging corrective action to the responsible system lines, replacing leaking valves, revising engineer at each site. At some sites, the procedures, and training PASS system licensee's expert panel participates in this operators. Long-term actions include the process.
establishment of goals and a monitoring program. The team also interviewed the At one site, the team reviewed correct,ve system engineer and found her to be very 1
i actions for six paragraph (a)(1) systems and knowledgeable of the PASS system and the found certain corrective actions were rule. The team believes that actions to ineffective. For example, the turbine-driven implement the rule caused licensees to focus auxiliary feedwater pump experienced an over-more attention to establishing appropriate
)
speed trip that was attributed to a faulty logic corrective actions for PASS and other card, which was replaced. Three months later, non-safety-related systems.
two more over-speed trips occurred: the first was again attributed to a faulty logic card, The team reviewed the corrective actions which was also replaced, and the second was taken by another licensee to repair a faulty attributed to a faulty seal on the servo unit.
pressurizer pressure transmitter. The system Two months later, a fourth over speed trip engineer had performed extensive reviews, occurred, which was again attributed to a considered industry-wide operating faulty logic card. The team concluded that a experience, and trended the performance of more thorough evaluation of the first failure similar transmitters to determine the cause of might have enabled the licensee to find the the faulty transmitter. The corrective actions root cause of the logic card failure and avoid established in this process corrected the the subsequent failures. To enhance its problem.
corrective action process, the licensee began requiring that all proposed corrective actions The licensees for most of the other sites visited be reviewed and approved by the expert panel.
by the team had established effective corrective The corrective actions will also include a action programs. At these sites, the system review of the corrective, predictive, and engineer was Senerally assigned responsibility preventive maintenance activities. The for determining corrective actions.
licensee's improved process for establishing corrective actions is very rigorous and Conclusions methodical.
Licensees established effective corrective The team reviewed the actions taken by one action programs. Some of those programs licensee to resolve problems with its post.
improved significantly after the licensees acted accident sampling system (PASS). This to the implement the rule, while others appear system had been very unreliable in the past and to have been effective before the rule.
was found to be inoperable when needed Although most licensees assigned the system during the two most recent emergency drills.
engineers primary responsibility for The team reviewed the corrective actions establishing corrective action, a few assigned taken for PASS since the licensee began that responsibility to an expert panel. Both implementing the rule and noted that the approaches produced acceptable results.
19 NUREG-1526
Recommendation standby systems within the scope of the rule.
Since precise system unavailability data was None.
not readily retrievable from plant records, the expert panel relied on their collective judgment 2.4.3 Safety Consideration in Goal Setting to estimate system unavailability data from the monthly operating reports. To validate this Paragraph (a)(1) of the rule requires that safety unavailability data, the licensee recalculated (risk) be considered when establishing goals the PRA using the new unavailability values and monitoring.
and confirmed that the results were consistent Findings with the original PRA calculation. This is another example of how safety has been Each licensee performed risk determinations considered when setting goals and for all SSCs within the scope of the rule at its Performance criteria.
site.' These risk determinations formed the basis for considering safety when setting goals At another site, the licensee selected goals and under paragraph (a)(1) and performance Performance enteria based on unavailability or criteria under (a)(2) of the rule. All licensees reliability data assumed in the licensee's PRA.
]
used the results of these initial risk The team reviewed the goals set for the determinations to decide if goals and emergency diesel generator, the demineralized performance criteria would be set at the water system, and the mstrument air system, and verified that information from the PRA system level or the plant level. System of train had been considered. The team concluded that level goals or performance criteria were set for risk-significant SSCs and for non-risk-this was an acceptable method of takmg safety nto considerat,on when sett, g goals under i
m significant SSCs that were used in standby service. Plant level goals were set for the Paragraph (a)(1) of the rule.
remaining non-risk-significant SSCs.
Therefore, all licensees had taken safety into consideration through the process of
- 1. Alllicensees had considered safety as part determining whether to set system-or plant-of ti.e process of determining if an SSC i
level goals.
should be categorized as risk-significant or Some of the licensees had taken safety into consideration in other ways in addition to the
- 2. Certain licensees considered safety by steps described above. For example, the using the same values for system reliability expert panel at one site received the and availability for goals as were assumed information from the risk determination in the PRA. Other licensees used the PRA process to use in establishing goals for those to check the validity of availability goals.
SSCs assigned to categories under paragraph (a)(1) of the mle and in establishing Recommendation performance criteria under paragraph (a)(2) of the rule. The expert panel decided to establish Eusure that procedures and processes functional failures and hours unavailable as adequately address safety when setting goals.
goals for most systems. To determine what would be appropriate unavailability values, the expert panel reviewed historical system performance for the risk-significant and NUREG-1526 20
2.4.4 Industry Operating Experience in must be taken into account whenever goals are Goal Setting established. At several other sites, the licensees had considered OE when establishing Paragraph (a)(1) of the rule requires that goals for all their paragraph (a)(1) systems and industry-wide operating experience (OE) be their procedures were adequate.
taken into account, where practical, when establishing goals.
At some sites, the OE database was available to each engineer on his or her computer Findings terminal, which could be used at any time to research for information on system or The degree to which OE was considered when component problems. The team believes that setting goals varied considerably among the such an online capability would facilitate the sites. At one site, the team verified that OE process of considering industry operating information from the Institute for Nuclear experience when setting goals. At other sites, Power Operations, and industry codes and the process for obtaining information from the standards had been considered when setting OE database required individual engineers to goals for some SSCs under paragraph (a)(1) of complete request forms, which were sent to the rule but not for others. The team reviewed the OE database manager who did the actual the licensee's procedures and noted that they search. This process is more cumbersome than only required that relevant industry NPRDS having an online capability and could inlubit operating experience be reviewed and the use of OE for goal setting.
considered as part of the goal setting process.
The licensee agreed to revise their procedure During the site visits, the team did not mention to clarify that their review should not be its concern that licensees had not established a limited to NPRDS data.
systematic and consistent method of collecting and using SSC reliability and availability data At another site, the team reviewed the goals from other licensees when setting goals. The set for several systems and verified, through team came to this conclusion during internal discussion with the licensee's system engineers, NRC meetings to discuss the results of the that OE had been considered when setting nine site visits. The team understands that goals. However, the team reviewed the goals for some SSCs are based on PRA '
licensee's procedures and found no explicit reliability and availability data which, to some requirement to endder OE as part of the goal extent, may have been developed from generic setting process. The hcensee's representative industry data. Therefore, industry-wide stated that consideration of OE was part of the reliability and availability data may have been root cause analysis process that would be considered when setting goals for a limited required whenever goals were established.
number of SSCs. However, after considering However, the representative agreed to add the this issue in the light of the results of all nine requirement to consider all relevant pilot inspections, the team concluded that a information from their OE program as part of more direct use ofindustry-wide reliability and their goal settmg procedure.
availability data should be considered by licensees. Existing OE programs at most sites Several licensees had considered OE when focus on anecdotal data such as descriptions of establishing goals for some of their paragraph specific equipment failures and do not (a)(1) systems but not for others. These generally give reliability and availability data.
licensees agreed to revise existing procedures Therefore, the team recommends that licensees or issue a new procedure to clarify that OE 21 NUREG-1526
\\
consider expanding their programs for likely to cause loss of an intended function, collecting OE information to ensure that monitoring under paragraph (a)(1) should be industry-wide SSC reliability and availability predictive, giving early warning of data is collected and considered in setting degradation. NUMARC 93-01 gives guidance goals in a systematic and consistent manner.
for using predictive maintenance, inspection, testing, and performance trending for Conclusions monitoring performance or condition under paragraph (a)(2) of the mle.
- 1. Most licensees had considered OE in varying degrees when setting goals.
Findings
- 2. Many licensees' procedures do not have The team reviewed the monitoring and adequate guidance for ensuring that OE is trending for selected systems and components considered, where practical, when at each site and found the following issues.
establishing goals.
Coordination of trending and goals. The
- 3. Those responsible for establishing goals at team found great variance among the licensees some sites had easy cccess to the OE in the quality and quantity of trending that was
+
database; at other sites the access was being performed. One licensee was doing very limited or cumbersome and could inhibit little trending of SSCs performance or the use of the database.
condition. Two otherlicensees had established trending programs that were well integrated
- 4. Licensees had not established a systematic into their rule programs. The remaining and consistent method of collecting and licensees had trending programs that were not using SSC reliability and availability data well integrated into their rule programs. Many from other licensees when setting goals.
of these trending programs generated equipment performance data that would be Recommendations very useful when establishing goals and
- 1. Review procedures to ensure that the Performance criteria under the rule; however, guidance is adequate for considering OE in many cases, licensees did not consider this when establishing goals.
data when selecting goals and performance entena and establishing a monitoring program
- 2. Ensure that OE data is readily accessible under the rule. The team believes that goal for plant stafTto use when setting goals.
setting and trending activities should be coordinated and integrated as much as possible
- 3. Consider expanding progen for so that the improvements in performance can collecting OE information to ensure that be monitored against established goals. Goals industry-wide SSC reliability and should use existing trending activities where availability data is collected and considered appropriate, and licensees should consider systematically and consistently when establishing new monitoring and trending setting goals activities that directly address the problem whenever new goals are established.
2.4.5 Monitoring and Trending of Systems and Components Trending for all goals not required.
Although trending of all goals should always In the statements of consideration for the mle, be considered, it may not be practical. For the Commission states that where failures are example, one licensee had established a NUREG-1526 22
predictive maintenance program that included established individual performance criteria periodic monitoring, diagnosis, and trending of and monitoring for each fuel oil pump train system performance and condition so that under the rule. The team was concerned needed maintenance could be performed that the redundant pump could degrade before failure. Predictive maintenance actions significantly without being detected included the use of diagnostic test equipment because one pump could supply the to perform vibration analysis, thermography, necessary volume of fuel during routine flow measurements, and ultrasonic surveillance tests. The high reliability of measurement of pipe wall thicimess. The team one pump could mask the unreliability of reviewed the documentation for five paragraph the redundant pump.
(a)(1) systems at that site and noted that comprehensive trending was being performed
- 2. One licensee used multiple redundant air for at least two of these systems. The team compressors to supply site compressed air concluded that trending was not necessarily and to act as an alternate supply for the required for the other three systems. The team instrument air system. The licensee's believes that trending should be used where representatives stated that one of the practical and appropriate, but not necessarily reasons for the many compressors was thet for all SSCs under the scope of the rule.
some ofthem were very unreliable.
Therefore, the level of trending being However, the licensee was monitoring this performed was reasonable.
system using plant-level performance criteria instead of train-level performance Monitoring of redundant trains. The NRC criteria. The licensee's representative staff endorsed the position in NUMARC 93-01 stated that they considered the extra that systems with redundant trains must be compressors to be installed spares rather monitored at the train level to ensure that the than redundant loops and therefore did not good performance of one train does not mask require train level goals for each the poor performance of the redundant train in compressor. The team disagreed with this a system. This train-level monitoring would be position, noting that the intent of the rule required for all those SSCs that were as explained in NUMARC 93-01 is to determined to be risk-significant and all monitor any system with redundant trains non-risk-significant SSCs that were used in at the train level. The intent of the rule is standby service. Monitoring at the train level also to monitor all standby systems at the would not be required for normally operating system level rather than at the plant level.
non-risk-significant SSCs, which can be In this case, the air compressors constitute monitored using plant level goals.
a system with multiple redundant compressor trains, some of which are used The team noted several instances where in standby service. Therefore, this system redundant trains were not being monitored at should not be monitored at the plant level the train level.
both because it contains redundant trains and because some of those trains are used
- 1. The fuel oil system for the emergency in standby service. Rather, each train, diesel generators at one site consisted of including the motor, compressor, and
(
two redundant fuel oil pump trains, either valves, should be monitored individually.
[
of which can be used to transfer fuel oil from the large storage tanks to the diesel At another site, the containment spray day tanks. The licensee had not system, which contains redundant trains, 23 NUREG-1526 m --
f was being monitored at the system level performance criteria with equipment trending rather than the train level, which could wherever possible.
allow unreliable components to go undetected.
Monitoring of standby systems or systems f
with redundant trains. Ensure that one train Trending of zero failures. At many of the does not mask the poor performance of a sites visited, licensees had established zero redundant or standby train. Accomplish this MPFFs or 100-percent reliability as a goal or task by monitoring at the following levels.
performance criterion for many of the SSCs o
under the scope of the rule. The rule intends
- 1. Monitor single train risk-significant that licensees be afforded maximum flexibility systems at the system level.
in establishing goals and performance criteria.
f However, the rule also intends that where
- 2. Monitor multiple train risk-significant failures are likely to cause loss of an intended systems at the train level.
function, monitoring should be predictive,
- 3. Monitor s.mgle train non-risk-s.igmficant giving early warning of degradation. The team was concerned that it would be difficult to use systems used in standby at the system level.
trending to help predict or anticipate failures
- 4. Monitor multiple train non-risk-significant l
when failure data is the only information being monitored.
systems that are used in standby service at the trainlevel.
Conclusions
- 5. Monitor normally openrting, non-risk-Coordination of trending and goals. Most significant systems at th: plant level.
licensees had established trending programs.
Trending of zero failures Where reliance on Trending was not required for all SSCs under the rule although it should be considered. The the use ofzero MPFFs or 100-percent reliability as a goal or perfbrmance criterion trending being performed by most licensees may preclude predictive trending, consider i
was not well coordinated and integrated with the goals and performance criteria established establishing additional goals and performance i
criteria that can be trended.
under the rule.
i 1
2.4.6 Monitoring and Trending of Monitoring of standby systems or systems Structures with redundant trains. Certain non-risk-significant systems used in standby service The rule requires that the performance or i
were being monitored at the plant level rather condition of stmetures be monitored in a than at the system or train level as required, manner sufficient to give reasonable assurance I
that those structures are capable offulfilling Trending of zero failures. Reliance on the their intended function. The statements of use of zero MPFFs or 100-percent reliability as consideration for the rule states "[w]here a goal or perfonnance criterion may preclude failures are likely to cause loss of an intended predictive trending.
function, monitoring should be predictive in nature, providing early warning of Recommendat.ons degradation." NUMARC 93-01, paragraph Coordination of trending and goals.
9.4.2.4 lists examples of structural monitoring Coordinate and integrate goals and activities meludmg nondestructive NUREG-1526 24
. n
=
examination, visual inspection, vibration needed. The team believes that the licensee analysis, and measurement of deflection.
should establish performance criteria and goals under the rule which take credit for the Findings existing monitoring activities and build upon h
them.
/
The team reviewed the monitoring and I
trending of structures at the nine pilot sites and One licensee had established performance
}
found that most licensees considered criteria for most structures under the scope of
)
monitoring of structures under the rule to be a the rule. However, the performance criteria low priority. Some licensees had not for many of these stmetures was that the established goals or performance criteria for stmeture would not degrade to the point monitoring most structures at their sites.
where it caused a loss of function of systems Many licensees considered most structures to contained in the structure or supported by it.
~
be inherently reliable. Some licensees believed For example, the roof of a building that was that as long as a structure such as a building leaking would meet the performance criteria did not fall down and damage the equipment until the water leaking into the building caused inside, the structure its:!f need not be the system inside the building to fail. However, monitored. At some sites, the onsite personnel such performance criteria are not acceptable j
were not aware of existing preventive because they are not predictive and do not give i
maintenance and monitoring activities that early warning of degradation. The team I
were being performed on these structures by believes that a more appropriate performance offsite stmetural or civil engineering groups.
criterion would have been "no water leaks."
One licensee took the position that their Another licensee had determined that all i
structures had performed acceptably for the structures within scope of the mie, except the j
past 20 years, not causing a loss of function of primary containment, were inherently reliable the systems contained in or supported by the and therefore did not require goal setting these structures, and were not expected to under parsgraph (a)(1) of the rule or
{i begin a more rapid degradation from aging in monitoring against performance criteria under the future. Therefore, believing these paragraph (a)(2) of the rule. The licensee's structures "very reliable," they found it representative stated that these structures are
[
unnecessary to establish goals or performance routinely examined by plant personnel during j
criteria to monitor them. However, they also their walkdown inspections of the plant. They stated that inspection and maintenance is believe that this monitoring activity is sufficient necessary to ensure degradation of these to verify that preventive maintenance is structures does not cause a loss of function.
adequate. The team believes that although l
The structures are monitored during the condition-monitoring is an appropriate method
}
normal operator rounds, management of monitoring structures, the lack of specific walkaround inspections, and inspection by criteria to monitor against would make it other plant departments in the course of difficult to detect degradation of these normal work activities. Deficiency cards and structures maintenance work orders are generated when conditions adverse to quality are found. The Conclusions team believes that the existence of these longstanding monitoring activities contradicts Most licensees considered the monitoring of the licensee's position that no monitoring is structures under the rule to be a low priority.
Some licensees incorrectly assumed that many 25 NUREG-1526 L
m
of their structures are inherently reliable. The 2.4.7 Functional Failures performance criteria for monitoring the performance or condition of some structures The statements of consideration for the rule are not predictive and do not give early state that where one or more maintenance warning of degradation.
Preventiblefailures occur on SSCs under paragraph (a)(2) of the rule, the effectiveness Certain structures such as the primary of preventive maintenance is no longer containment can be monitored by fulfilling demonstrated, and the SSC must then be established testing requirements such as those treated under paragraph (a)(1) of the rule. This in 10 CFR Pan 50, Appendix 1 However, term was changed in NUMARC 93-01 to other structures such as reactor buildings, maintenance preventiblefunctionalfailures to auxiliary buildings, and cooling towers may be emphasize that only a failure in which the item more amenable to condition-monitoring.
actually failed the function should be counted Some licensees are developing programs for as a failure that would require goal setting and l
monitoring structures that willinclude doing monitoring under paragraph (a)(1).
plant walkdown inspections and engineering j
evaluations to establish condition-monitoring Findings criteria. This program should include the establishment of specific criteria for Two licensees focused onfunctionalfailures monitoring.
rather than just maintenance preventible functionalfailures as described in NUMARC Recommendations 93-01. These licensees did so because it was easier to process both types of failures
- l. Reevaluate the monitoring of stmetures (maintenance-related or not) in the same and determine, using the methods manner because they would not know if the described in NUMARC 93-01, paragraph failure was maintenance-preventible until after 9.3.2, to determine whether performance the root cause evaluation had been performed.
j criteria or goals are needed to monitor the The team reviewed this approach and noted performance or condition ofindividual that all functional failures would be evaluated i
structures.
and dispositioned in the same manner as
- 2. Review the existing structural monitoring activities and use them, with enhancements Conclusion as necessary, as a basis for establishing a l
monitoring program under the rule.
The use offunctionalfailures in stead of 1
maintenance-preventiblefunctionalfailures is
- 3. Do not use very reliable or inherently acceptable. Approaches other than those reliable to describe structures that require described in NUMARC 93-01 are acceptable if preventive maintenance or monitoring.
the licensee can demonstrate that the alternative gives the same level of assurance
- 4. Establish performance criteria or goals that that the requirements of the rule will be are predictive and give early warning of satisfied.
failure.
- 5. Take credit for existing plant walkdown inspections or other structural inspection activities under the rule.
NUREG-1526 26
.A
=
Recommendation data each month. In addition, a bimonthly system status report would be issued which None would include an assessment of actual performance against the performance criteria 2.5 Periodic Evaluations for all systems within the scope of the rule, an evaluation of maintenance effectiveness, an Paragraph (a)(3) of the rule requires that evaluation of the balance of unavailability and performance-and condition-monitoring reliability, and an evaluation of the continued activities and associated goals and preventive applicability of the established performance maintenance activities be evaluated at least criteria. These continuing activities would be every refueling cycle if the interval between followed by a high-level periodic evaluation to I
evaluations does not exceed 24 months. The verify all rule requirements have been met. The evaluation is required to consider, where evaluation would include a sampling of actual practical, industry-wide operating experience.
implementation. These high-level periodic l
evaluations would be performed each refueling j
At each site, the team reviewed the licensee's cycle, not to exceed 24 months between j
plans and procedures for performing the evaluations.
j" evaluations.
Two licensees had already doine periodic Findings evaluations even though the first evaluation would not be due until after the rule takes One licensee planned to do the period.ic effect on July 10,1996. The licensees evaluation each year to coinade with other performed these evaluations to gain experience existmg maintenance evaluation activities.
and to evaluate their progress in implementing g
[
Since the hcensee's refueling cycle is longer the other requirements of the rule. The team than one year, performing the penodic reviewed these preliminary evaluations and evaluation annually would result in it be.ing found that both generally met the requirements evaluated more frequently than required by the of the mie' rule. At the remaining sites, the licensees planned to perform the evaluation once each Conclusions refueling cycle.
- 1. Performing the periodic evaluation each At one of the two unit sites where a periodic year meets the intent of the rule if the evaluation is planned once each refueling refueling cycle is longer than one year.
cycle, the licensee plans to evaluate both units at the site at the same time. The licensee will
- 2. The periodic evaluation does not have to periodically evaluate each unit at a different be performed at any particular time during time during each unit's refueling cycle because the refueling cycle as long it is performed the refueling outages for each unit at that site at least one time during the cycle, and the are not scheduled at the same time.
interval between evaluations does not exceed 24 months. This requirement Another licensee plans to perform most of the would permit the licensee for a multiple required evaluations on a continuing schedule unit site to perform the periodic throughout the refueling cycle. System evaluations of all units at the same time engineers would continuously assess the even though the refueling cycles for the b
appropriateness of the performance criteria for units are staggered.
their assigned systems and update performance i
27 NUREG-1526 Y
,J
^
- 3. The requirement for performing the Two licensees plan to continually balance periodic evaluation can be satisfied by unavailability and reliability as an integral part using continuing evaluations, with a higher of monitoring against performance criteria level summary evaluation performed at under the rule. Performance history, least once each refueling cycle.
preventive maintenance activities, and out-of-service time are considered when
- 4. The early periodic evaluations performed developing the performance criteria. The by two of the licensees were generally licensees believe that meeting these satisfactory.
performance criteria will ensure that a satisfactory balance of reliability and
- 5. The other seven licensees had reasonable unavailability has been achieved. The team preliminary plans and procedures for found that guidance, acceptance criteria, or performing the penodic evaluation, both needed to be added to the licensees' although their implementation could not be procedures, reviewed at the time of the site visit.
At one site, unavailability and reliability were Recommendations initially balanced by the licensee's expert panel.
None.
The licensee will maintain this balance by trending and evaluating SSCs rendered 2.6 Balancing Unavailability and unavailable because of preventive maintenance and by making adjustments where necessary to Reliability achieve the appropriate balance. The licensee's Performance Monitoring Group will perform Paragraph (a)(3) of the rule states that this activity as part of their semi-annual adjustments shall be made where necessary to evaluation of maintenance program activities.
ensure that the objective of preventing failures of structures, systems, and components One licensee plans to accomplish this balancing through maintenance is appropriately balanced by calculating the risk contribution associated against the objective of minimizing the effect with unavailability of the system caused by of monitoring or preventive maintenance on preventive maintenance activities and the risk the availability of structures, systems, and contribution causing the reliability of the SSC.
components.
The licensee would then attempt to balance the
[
contribution to risk from each source to ensure At each of the sites, the team reviewed the consistency with PRA or IPE evaluations.
plans, processes, and procedures established for doing this activity.
Another licensee's PRA was used to determine values for unavailability and reliability which, if Findings met, would ensure that certain threshold CDF values would not be exceeded. The The team found that although all licensees had performance criteria were established in established preliminary plans for accomplishmg accordance with these unavailability and this activity, none of them had fully developed reliability values. The licensee believes that and implemented these plans. However, five meeting these performance criteria will ensure 4
of the licensees had procedures for accomplishing this activity, which were a reasonable balance of unavailability and reliability is attained.
reviewed by the team.
NUREG-1526 28 6
f
=
l Conclusions probability of being able to mitigate the consequences by preserving containment Each of the nine licensees established integrity.
reasonable preliminary plans for balancing unavailability and reliability, and the Findings procedures developed by five of those licensees were reasonable. However, the team One licensee elected to use a matrix approach, I
was unable to evaluate these activities because which involved listing preanalyzed
?
these plans had not been implemented at the configurations to supplement their existing time of the site visits.
Procedural guidance for voluntary online maintenance. Thislist ofpreanalyzed
[
Recorumendation configurations was developed using risk achievement worth (RAW) to rank Focus attention on establishing and configurations according to risk. The implementing processes and procedures for licensee's existing work planning processes balancing unavailability and reliability as established a preventive maintenance (PM) required by paragraph (a)(3) of the rule.
schedule, which allows work on only one division (train) of certain systems to help limit 2.7 Plant Safety Assessments for the risk of placing multiple trains of the same Taking Equipment out of system out of service at one time.
i Service One licensee makes use of a 12-week rolling Paragraph (a)(3) of the rule states that, when window cycle to schedule preventive maintenance activities. At the time of the site performing monitoring and preventive maintenance activities, an assesstnent of the visit, the licensee was developing a procedure t establish PRA-based priorities for taking total plant equipment that is out of service should be considered to determine the overall certain combinations of systems out of service f r maintenance at the same time.
effect on performance of safety functions.
NRC issued Temporary Instruction (TI)
One licensee's plant operations staff maintained 2515/126, " Evaluation of On-Line an equipment out-of-service (EOOS) status t
)
Maintenance," to aid inspectors in evaluating board to assess the total plant equipment that is out of service. To control risk in the the effect on safety oflicensee procedures and practices for removing equipment from service schedule for the upcoming maintenance i
for online maintenance. This instruction activities, the licensee will use the plant IPE to details the NRC's expectations regarding safety evaluate the increases in core damage assessments to be performed before taking frequency (CDF) resulting from multiple i
equipment out of service. The instruction equipment outages. The licensee will adjust the recommends inspectors consider three factors schedule to minimize significant spikes in the I
when evaluating the overall risk of taking CDF envelope of the schedule. The licensee has also established administrative controls equipment out of service for online i
l maintenance: (1) the probability of an initiating that forbid certain equipment out-of-service i
event such as a loss-of-coolant accident, configurations under specified conditions. In f
turbine trip, or loss of offsite power; (2) the addition, the licensee is considering the probability of being able to mitigate the event Purchase of a real-time safety (risk) monitor.
using core damage prevention; and (3) the 29 NUREG-1526
One licensee plans to incorporate a matrix of One licensee plans to evaluate the total effect risk-significant combinations of equipment into on plant safety by using an IPE tool and hand i
their 12-week work planning schedule. This calculations. This IPE tool will be used for matrix, which was developed from the evaluating the risk significance of online licensee's PRA, lists combinations of maintenance strategies as an interim approach equipment that would increase risk until more sophisticated calculational aids are unacceptably if taken out of service at the developed. The IPE tool gives risk evaluations same time. Procedures to implement this for the 500 highest contributing core damage process had not been developed at the time of sequences, which account for about 93 percent the site visit.
of the total CDF. The licensee is considering a more accurate tool for the longer term, such as One licensee is planning to design a rolling a risk monitor (near real-time), which would windows (12-week) maintenance schedule be used for preventive maintenance planning with the matrix formulation of the Operational and other applications. The licensee is Safety Predictor (OSPRE) methodology to preparing the procedures to implement this control the risk resulting multiple equipment requirement. In addition, this licensee plans to outages. The licensee will adjust this schedule design a rolling windows preventive with the OSPRE matrix to minimize risk. In maintenance schedule with a matrix addition, the licensee drafted a policy formulation methodology to control the risk statement that requires the establishment of an resulting multiple equipment outages in the effective risk management program to various schedular weeks. The licensee will determine the relative amount of risk involved adjust this schedule with the matrix to in making systems or components unavailable minimize risk.
and to evaluate the effect of multiple concurrent outages of systems important to One licensee implemented a program that j
safety. This policy statement addresses the generates risk profiles for planned maintenance need to (1) assess the confidence in the activities each week. These profiles are redundant equipment before taking equipment discussed at a weekly scheduling meeting.
I out of service for maintenance, (2) minimize Changes are made to the schedule to improve challenges to that redundant equipment, and safety when undesirable equipment outage (3) establish contingency plans in case the configuration changes are anticipated. The redundant train is also rendered inoperable.
licensee also plans to establish a rolling window (12-week) maintenance schedule that One licensee's online maintenance work will use PRA methodology to control the risk philosophy is based on " ensuring plant safety, resulting from multiple equipment outages.
maximizing availability, and maintaining They also plan to use the outage risk adequate reliability." The plant operations assessment and management (ORAM) tool to staff maintains a " plan of the day" that control shutdown risk associated with l
describes all work authorized to be performed maintenance activities during outages.
on or around operating plant equipment during i
the 24-hour period. Specific procedures for One licensee is using probabilistic safety establishing a preventive maintenance assessment monitor (PSAM) software to equipment out-of-service matrix were still improve the reliability and safety of the plant being developed at the time of the site visit.
by enhanced online risk monitoring of risk-significant systems included in the plant PRA.
A weekly draft online maintenance schedule is NUREG-1526 30
produced on Thursday of each week and is operational situations and may unnecessarily analyzed using the risk monitor software limit operational flexibility.
before noon on Friday of the same week. On Monday of the following week, before Several licensees are planning to use real time equipment is taken out of service for (or nearly real time) risk monitors that can maintenance, a final risk analysis is performed calculate the risk changes associated with the P anned maintenance activities. Although risk l
and any necessary schedular adjustments are made. The licensee also reduces the monitors can analyze a greater number of l
occurrence ofinitiating events by paying possible combinations of out of service heightened attention to main feedwater system systems, they may require specially trained operability before performing maintenance on personnel to operate them or to interpret de emergency feedwater pumps and by ensuring results.
that no switchyard work is performed when an emergency diesel generator is out of service.
Both the matrix and the risk monitor were The licensee analyzes plant conditions each reasonable ways of assessing the effect on lP ant safety when taking equipment out of l
day, including reviewing operational logs to ensure that redundant train equipment or service for monitoring or preventive support equipment is not degraded during the maintenance. However, the team could not online maintenance. The licensee uses a evaluate the effectiveness of either of these software program called CAFTA (Computer methods because they had not been fully Aided Fault Tree Analysis) to aid in controlling implemented at the time of the site visits.
shutdown risk.
Many of the licensees had not established Conclusions Programs and procedures that prescribed giving consideration to initiating events, Certain licensees were using a variety of mitigating capability, and containment integrity approaches for assessing the overall effect on before taking equipment out of service for the performance of safety functions of taking monitoring or preventive maintenance.
plant equipment out of service for monitoring or preventive maintenance, while others were Recommendations planning to do so.
- l. Develop and implement processes and Some licensees plans and procedures for Procedures for considering plant safety performing safety assessments appear to be before taking equipment out of service for well thought out and comprehensive although mamtenance.
they had not been fully implemented. The plans at other sites were preliminary, and the
- 2. Jnclude a program requirement to consider procedures had not yet been developed or imtialmg events, mitigat,mg capability, and implemented.
containment integnty before taking equipment out of service for monitoring or Many licensees approached the problem by Preventive maintenance.
developing a matrix that defines which system combinations could be allowed out of service
- 3. Pay increased attent,on to reducing i
at the same time. Although the matrix is simple initiating event frequencies, with particular to use, it defines a limited number of
- phasis on enhanced safety oversight of combinations that may not address all switchyard activities.
31 NUREG-1526
3 CONCLUSION f
The team considered the observations made The team also concluded that the performance-during these pilot site visits and concluded that based approach to implementing the rule is the requirements of 10 CFR 50.65 can be met practical; the draft inspection procedure can be by using NUMARC 93-01 if the used to monitor the implementation of the rule; recommendations in this report are taken into and the existing PRA tools and models, used in consideration.
conjunction with an expert panel, are adequate for taking risk into consideration when implementing the rule.
33 NUREG-1526
.__-______--.-____-_____A
NRC soRu 335 u.S. NUCLE AR L EIULF. TORY COMNilS$1CN
- 1. REPOAT NUMBER L*"EllLf"=Ml"o,.'.';l'L*"i"~ ""-
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DATE REPORT PUBLISHED uomTH V$AR Lessons Learned From Early Implementation of The June 1995 Maintenance Rule at Nine Nuclear Power Plants UW OR GRANT NUMBER
- 6. AUTHOR (5)
- 6. TYPE OF REPORT l
C.D. Petrone, R.P. Correia, S.C. Black Final
- 7. PERIOD COVEREDisacs s e onces /
u N/A I
- e. PERF0Rgg,N,iAT,0N - N Au e ANo AooREss 1,1~ac.
o o ao ora-or no,6 as N.c ar n se,or, c.--
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(
Washington, DC 20555-0001
- 9. SPONSORING ORGAN 1ZAT80N - NAME AND ADDR ESS 199 Nac. sype ~some m eso.e~. cr contrarror. revner Nnc o.vo.oe. Oroke or neron. v1 Necker no,userary cmason, and meant naureul L
l i
SAME AS AB0VE 3
- 10. SUPPLEMENTARY NOTES
- 11. A85 TRACT tmwerde er mes>
This report summarizes the lessons learned from the nine pilot site visits that were performed to review early implementation of the maintenance rule using the draft NRC Maintenance inspection i
i Procedure. Licensees followed NUMARC 93-01, " Industry Guideline for Monitoring the ji Effectiveness of Maintenance at Nuclear Power Plants." In general, the licensees were thorough in i
determining which structures, systems, and components (SSCs) were within the scope of the I
maintenance rule at each site. The use of an expert panel was an appropriate and practical method i
of determining which SSCs are risk significant. When setting goals, alllicensees considered safety but rnany licensees did not consider operating experience throughout the industry. Although li required to do so, licensees were not monitoring at the system or train level the performance or
)
condition for some systems used in standby service but not significant to risk. Most licensees had y
not established adequate monitoring of structures under the rule. Licensees established reasonable l
plans for doing periodic evaluations, balancing unavailability and reliability, and assessing the effect of taking equipment out of service for maintenance. However, these plans were not evaluated
)
because they had not been fully implemented at the time of the site visits.
- 12. K E Y WOR D$/CE$CRtPTORS (t6sr weret or Aram ener =#t meet mese. cam m acceday rne moorr./
- 13. AvAlLA88UT V $1 Aif MEN 1 j
Unlimited i
Maintenance Rule
, w cuo,1Tc m,.cAnou Maintenance Rule Pilot Site Visits 3
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10 CFR 50.65 Unclassified (TMs neportl Unclassified
- 15. NUMBER OF PAGES
- 16. PRICE NRC 70Ru 336 (2491
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.NUREG-1526 LESSONS LEARNED FROM EARLY IMPLEMENTATION OF THE MAINTENANCE RULE '-
JUNE 1995.
AT NINE NUCLEAR POWER PIANTS
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