ML20137E500
| ML20137E500 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1997 |
| From: | NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| References | |
| TASK-*****, TASK-DG-1051, TASK-RE REGGD-01.160, REGGD-1.160, NUDOCS 9703270294 | |
| Download: ML20137E500 (10) | |
Text
U.S. NUCLEAR REGULATORY COMMISSION Revision 2
[eag'o March 1997 g
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REGULATORY GUIDE OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 1.160 (Draft was DG-1051)
MONITORING THE EFFECTIVENESS OF MAINTENANCE AT NUCLEAR POWER PLANTS A. INTRODUCTION consistent with the NRC's defense-in-depth philoso-phy. Maintenance is also important to ensure that de-The NRC published the maintenance rule on sign assumptions and margins in the original design ba-July 10,1991, as Section 50.65, " Requirements for sis are maintained and are not unacceptably degraded.
Monitoring the Effectiveness of Maintenance at Nu-Therefore, nuclear power plant maintenance is clearly clear Power Plants," of 10 CFR Part 50, " Domestic Li-important in protecting public health and safety.
censing of Production and Utilization Facilities." The NRC's determination that a maintenance rule was Paragraph (a)(1) of 10 CFR 50.65 requires that needed arose from the conclusion that proper mainte.
power reactor licensees monitor the performance or nance is essential to plant safety. As discussed in the condition of SSCs against licensee-established goals in regulatory analysis for this rule,3 there is a clear link be.
a manner sufficient to provide reasonable assurance tween effective maintenance and safety as it relates to that such SSCs are capable of fulfilling their intended
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such factors as the number of transients and challenges fun:tions. Such goals are to be established commensu-V to safety systems and the associated need for operabil.
rate with safety and, where practical, take into account k
ity, availability, and reliability of safety equipment. In industry-wide operating experience. When the perfor-
/
addition, good maintenance is also important in provid.
mance or condition of an SSC does not meet estab-ing assurance that failures of other than safety-related lished goals, appropriate corrective action must be tak-structures, systems, and components (SSCs) that could en. For a nuclear power plant for which the licensee has initiate or adversely affect a transient or accident are submitted the certifications specified in 10 CFR minimized. Minimizing challenges to safety systems is 50.82(a)(1) (i.e., plants undergoing decommissioning),
Paragraph (a)(1) of 10 CFR 50.65 applies only to the ent 6at b kemee mW monb b pehmance e
'NRC Memorandum to All Commissioners from J. Taylor on "Mainte-nance Rulemaking." June 27,1991. Copies are av ailable for inspection or or condition of all SSCs associated with storing, con-wrying for a fee fram the NRC Public Document Room at 2120 L street.
trollinS, and maintaininS bpent fuel in a safe condition' N%.. Washington. DC; the PDR's mailing address is Mail stop LL-6, washington, DC 20555; phone (202)634-3273; fax (202)634-3343.
in a manner sufficient to provide reasonable assurance USNRC Rf;GULA10RY GUIDES The gu des are ssued m the follow ng ten broad dnnseons Feegulatory Gwdes are sasued to describe and mano avalaose to the publec such eforma-ton as methods acceptable to the NRC std for enplememing specac parts of the Com-q poww Reactors.
6 Froducts messon a regulations, techn# ques used by the star novaluating specific problems or pos-
- 2. Research and Test Reactors 7.
Transportaton i
tulated accidents, and data needed by the NRC staff m sts roman of applications for per' 3 Fue s and Meenas facihtees 8 Occupational Health mits and hcenses Regulatory gudas are not subs 11tutes for regulatons. and comphance 4 Enwronmentar and Smng 9 Antitrust and Financial Review with them a not rogured Methods and solutions different from those set out en the gedes 5 Matenals and Plant Protection 10 General was be acceptabe il they provide a base for the findsngs requsste to the issuance or con.
in.nce of a perma or i.cena by ine comm,=.on.
This gwde was asued after consideraton of comments received from the pubkC Com.
ments and suggestrons for emprovements m these guedes are encouraged at all hmes and Adminstration. Attention Distnbuhon and Mal Sennces Section, U S Nuclear Hegulatory f%g gudes win b. rey.ed. apprognai.. io accommodais comm.ms and io reneci nem Comenss6on, Washsngton, DC P0555-0001, or by fax at (301)415-2200 issued gwdes may also be purchased from the National Techrucal informahon Service on
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Wntien comments may be submitted to the Rules Remew and Directivas Branch, DFIPS.
a standing order basis Detals on the sannce may be obtened by wnting NTIS, 5285 Port ADM. U $ Nuchner Regulatory Commasa on, Washington. DC 20555-0001 Royal Road, Spnngfield VA 22161.
9703270294 970331 W--C.O' J \\
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that such SSCs are capable of fulfilling their intended functions 2 (i) That are relied upon to mitigate accidents or transients or are used in plant emergen-(
Paragraph (a)(2) of 10 CFR 50.65 states that moni-cy oper ting procedures (EOPs); or toring as specified in Paragraph (a)(1) is not required where it has been demonstrated that the performance or (ii) Whose failure could prevent safety-condition of an SSC is being effectively controlled related structures, systems, and compo-through the performance of appropriate preventive nents from fulfilling their safety-related maintenance, such that the SSC remains capable of per-function; or forming its intended function.
(iii) Whose failure could cause a reactor Paragraph (a)(3) of 10 CFR 50.65 requires that per.
scram or actuation of a safety-related formance and condition monitoring activities and asso.
system.
ciated goals and preventive maintenance activities be evaluated at least every refueling cycle provided the in-Paragraph (c) of 10 CFR 50.65 states that the rule terval between evaluations does not exceed 24 months.provisions are to be implemented by licensees no later than July 10,1996.
The evaluations must be conducted taking into account, where practical, m. dustry-wide operating experience, This Regulatory Guide 1.160 is bem.g revised to Adjustments must be made where necessary to ensure endorse Revision 2 of NUMARC 93-01, " Industry that the objective of preventing failures of SSCs Guideline for Monitoring the Effectiveness of Mainte-through maintenance is appropriately balanced against nance at Nuclear Power Plants"4 (April 1996), which the objective of minimizing unavailability of SSCs be-has been updated by the Nuclear Energy Institute. The cause of monitoring or preventive maintenance, in per-regulatory guidance is intended to provide flexibility forming monitoring and preventive mamtenance activ-for a licensee to structure its maintenance program in itses, an assessment of the total plant equipment that is duce with the safety significance of those SSCs out of service should be taken m. to account to determinewithin the scope of the rule.
the overall effect on performance of safety functions.
The information collections contained in this regu-Paragraph (b) of 10 CFR 50.65 states that the scope latory guide are covered by the requirements of 10 CFR of the monitoring program specified in Paragraph Part 50, which were approved by the Office of Manage-(a)(1) is to include safety-related and nonsafety-related ment and Budget, approval number 3150-001). The SSCs as follows.
NRC may not conduct or sponsor, and a person is not required to respond to, a collection of information un-(1) Safety-related structures, systems, or compo.
less it displays a currently valid OMB control number, nents that are relied upon to remain functional during and following design basis events to B. DISCUSSION ensure the integrity of the reactor coolant pres-sure boundary, the capability to shut down the OBJECTIVE reactor and maintain it in a safe shutdown con-dition, and the capability to prevent or mitigate The objective of 10 CFR 50.65 (referred to hereaf-the consequences of accidents that could result ter as the maintenance rule or the rule) is to require in potential offsite exposure comparable to the monitoring of the overall continuing effectiveness ofli-guidelines in 10 CFR 50.34(a)(1) or 100.11 of censee maintenance programs to ensure that (1) safety-this chapter, as applicable.3 related and certain nonsafety. elated SSCs are capable of performing their intended. unctions and (2) for non-(2) Nonsafety-related structures, systems,orcom-s fety-related equipment, failures will not occur that ponents:
prevent the fulfillment of safety-related functions, and failures resulting in scrams and unnecessary actuations 2
The specific requirements for decommissioning plants became effectisc August 28,1996. Sec 6I FR 39278. July 19.1996. " Decommissioning of Nuclear Power Reactors."
3nis Paragraph (b)(l) of the maintenance rule w as changed in the final
'This document is av ailable for inspection or coppng for a fee in the NRC rulemaking for " Reactor site Criteria including Seismic and Earthquake Pubhc Document Room,2120 L Street Nw., Washmgton, DC; the PDR's Imgineering Criteria for Nuclear Pow et Plants," December 11,1996. see mailing address is Mail stop 1.1.-6, Washington, DC 20555; phone 61 iR 65157.
(202)634-3273, fax (202)634-3343.
1.160-2
i DEVELOPMENT OF INDUSTRY GUIDELINE, PLANT, SYSTEM, TRAIN, AND COMPONENT NUMARC 93-01 MONITORING LEVELS (N
The nuclear industry developed a document, The extent of monitoring may vary from system to i
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NUMARC 93-01," Industry Guideline for Monitoring system depending on the system's importance to safety, the Effectiveness of Maintenance at Nuclear Power Some monitoring at the component level may be neces-Plants"(May 1993),4 that provides guidance to licen-sary; however,it is envisioned that most of the monitor-sees regarding implementation of the maintenance rule.
ing could be done at the plant, system, or train level.
This document was prepared by NUMARC. A verifica.
SSCs with high safety significance and standby SSCs tion and validation (V&V) effort was conducted by with low safety significance should be monitored at the NUMARC, with NRC staff observation, to test the system or train level. Except as noted in the Regulatory guidance document on several representative systems.
Position of this guide, normally operating SSCs with A number of changes were made to the NUMARC low safety significance may be monitored through guidance document based on the results of the V&V ef-plant-level performance criteria, including unplanned fort. The NRC staff reviewed this document and found scrams, safety system actuations, or unplanned capa-that it provided acceptable guidance to licensees. In bility loss factors. For SSCs monitored in accordance June 1993, the NRC staff issued Regulatory Guide with 10 CFR 50.65(a)(1), additional parameter trend-1.160," Monitoring the Effectiveness of Maintenance ing may be necessary to ensure that the problem that at Nuclear Power Plants," which endorsed the May caused the SSC to be placed in the Paragraph (a)(1) 1993 version of NUMARC 93-01. In January 1995, the category is being corrected.
NRC staffissued Revision 1 to Regulatory Guide 1.160 USE OF EXISTING LICENSEE PROGRAMS to reflect the amendment to 10 CFR 50.65(a)(3) that changed the requirement for performing the periodic The NRC staff encourages licensees to use, to the evaluation from annually to once per refueling cycle, maximum extent practicable, activities currently being not to exceed 24 months between evaluations.
conducted, such as technical specification surveillance From September 1994 to March 1995, the NRC "E'
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S '#9" sties could be integrated with, and provide the basis for, g
staff performed a series of nine pilot site visits to verify the requisite level of monitoring. Consistent with the the usability and adequacy of the draft NRC mainte-underlying purposes of the rule, maximum flexibility nance rule inspection procedure and to determme the should be offered to licensees in establishing and modi-strengths and weaknesses of the implementation of the fying their monitoring activities.
rule at each site that used the guidance provided in NU-MARC 93-01. The findings are described in USE OF RELIABILITY-BASED PROGRAMS NUREG-1526, " Lessons Learned from Early Imple-Licensees are encouraged to consider the use of mentation of the Maintenance Rule at Nine Nuclear reliability-based methods for developing the preven-Power Plants"S (June 1995). The NRC staff concluded tive maintenance programs covered under 10 CFR that the requirements of the rule could be met more con-50.65(a)(2); however, the use of such methods is not sistently across the industry if some clarifying guid-required.
ance was added to NUMARC 93-01 to address the fin-dings noted in NUREG-1526. The NRC staff met with SAFETY SIGNIFICANCE CATEGORIES industry representatives in a series of public meetings The maintenance rule requires that goals be estab-to discuss proposed revisions to NUMARC 93-01 that lished commensurate with safety, in order to imple-would address the findings noted during the site visits.
ment this requirement, NUMARC 93-01 established Revision 2 to NUMARC 93-01 (April 1996) resulted two safety significance categories, " risk-significant" from these meetings.
and "non-risk-significant." The process for placing i
SSCs in either of these two categories is described in section 9.0 of NUMARC 93-01. The statements of consideration for the rule use the terms "more risk-5copics are available at current rates from the U.S. Government Printing b"
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Omce. P.O. Box 37082, Washington. DC 20402-9328 (telephone tion procedure (IP) 62706 uses the terms "high safety (202)512-2249); or from the National Technical lnformation service by significance" and " low safety significance." After dis-i wniing NTIS at 5285 Port Royal Road. Springfield. VA 22161. Copics are available for inspection or copying for a fee from the NRC Public cussions with industry representatives, the NRC staff
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Document Room at 21201. Street NW., Washington DC; the PDR's has determined that the preferred terminology is "high mailmg address is Mail stop L1A. Washington, DC 20555; telephone (202)634-3273; fax (202)634-3343.
safety significance" and " low safety significance."
1.160 - 3
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i Some licensees may elect to define other safety signifi-plant operations. Plant management should be aware of cance categories or may elect to define more than two and have the ability to control these activities.
categories, which would be acceptable if these alterna-EMERGENCY DIESEL GENERATORS tive categories are defined in the licensce's procedures and used in a consistem manner.
Industry-and NRC-sponsored probabilistic risle analyses (PRAs) have shown the safety significance of SAFETY SIGNIFICANCE RANKING emergency ac power sources. The station blackout rule METIIODOLOGY (10 CFR 50.63) required plant-specific coping analyses The NRC staff endorses the use of the SSC safety to ensure that a plant could withstand a totalloss of ac significance ranking methodology described in Revi-power for a specified duration and to determine ap-sion 2 (April 1996) of NUMARC 93-01 as an accept-propriate actions to mitigate the effects of a total loss of able method for meeting the requirements of the main-ac power. During the station blackout reviews, most li-j tenance rule.6 Ilowever, because of some unique censees: (1) made a commitment to implement an
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aspects of the maintenance rule, including the fact that emergency diesel generator (EDG) reliability program standby SSCs oflow safety significance are treated the in accordance with NRC regulatory guidance but re-same as SSCs of high safety significance, this endorse-served the option to later adopt the outcome of Generic ment for purposes of the maintenance rule should not be Issue B-56 resolution, and (2) stated that they had or construed as an endorsement fot other applications.
will implement an equivalent program. Subsequently, These issues were discussed in SECY 95-265, "Re-utilities docketed commitments to maintain their se-sponse to August 9,1995, Staff Requirements Memo-lected target reliability values (i.e., maintain the emer-randum Request to Analyze the Generic Applicability gency diesel generator target reliability of 0.95 or of the Risk Determination Process Used inImplement-0.975). Those values could be used as a goal or as a per-ing the Maintenance Rule."4 formance criterion for emergency diesel generator reli-ability under the maintenance rule.
APPLICABILITY OF APPENDIX B TO 10 CFR PART 50 Emergency diesel generator unavailability values were also assumed in plant-specific individual plant ex-With regard to the scope of the maintenance rule, as amination (IPE) analyses. These values should be stated in Paragraph (b) of the rule, it is understood that compared to the plant-specific emergency diesel gener-balance of plant (BOP) SSCs may have been designed ator unavailability data regularly monitored and re-and built with normal industrial quality and may not ported as industry-wide plant performance informa-meet the standards in Appendix B to 10 CFR Part 50. It tion. These values could also be used as the basis for a is not the intent of the NRC staff to require licensees t goal or performance criterion under the maintenance generate paperwork to document the basis for the de-rule. In addition,in accordance with Paragraph (a)(3) of sign, fabrication, and construction of BOP equipment the rule, licensees must periodically balance unavail-(i.e., BOP equipment need not meet the requirements of ability and reliability of the emergency diesel Appendix B to 10 CFR Part 50).
generators.
Each licensee's maintenance efforts should mini-C. REGULATORY POSITION mize failures in both safety-related and BOP SSCs that affect safe operation of the plant. The effectiveness of 1.
NUMARC 93-01 maintenance programs should be maintained for the Revision 2 of NUMARC 93-01," Industry Guide-operational life of the facility.
line for Monitoring the Effectiveness of Maintenance at SWITCIIYARD MAINTENANCE ACTIVITIES Nuclear Power Plants,"4 provides methods that are ac-i ceptable to the NRC staff for complying with the provi-As noted in the Regulatory Position of th,s guide, sions of 10 CFR 50.65 with the following provisions there may be a need to address maintenance activities and clarifications.
that occur in the switchyards that could directly affect 1.1 Scope of the Rule
- nie stafris developing guidar.cc that addresses the acceptable criteria 1.1.1 "Could Cause" Criterion
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During the nine pilat site visits, the NRC staff rec-h'
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reference the guidance, w hen available. to make the NRC staff's guid-ognized that som: licensees it.terpreted the words in
,'$. "j,"[*,i,$^,l",,'c1'"r Ii2 r'i$d " 'fa'Ii t. jf"e'inds ry seetion 8.2.1.5 of NUMARC 93-01 to mean that on1y A'
gu will be encouraged to use this guidance at that time.
those SSCs that had actually caused a plant scram or 1.160 - 4 C
safety system actuation needed to be included within 1.1.3 Function Versus System the scope of the rule. The NRC staff's position is that The rule provides criteria to determine which SSCs the SSCs to be included under the criterion "could must be included within the scope of the rule. Alterna-cause a reactor scram or actuation of a safety system" tively, licensees may use a functional basis to determine should not be limited to SSCs that "did cause" or which SSCs must be monitored within the scope of the "could likely cause." This position was discussed in rule. That is, the licensee may determine all the func-NUREG-1526, " Lessons Learned from Early imple-tions performed by the SSCs and include within the mentation of the Maintenance Rule at Nine Nuclear scope of the maintenance rule only those functions, and Power Plants"(June 1995).5 Licensees should consider the associated SSCs that fulfill those functions, that the following SSCs to be within the scope of the rule.
meet the scoping criteria of the rule.
1.
SSCs whose failure has caused a reactor scram 1.1.4 Systems with Multiple Design Functions or actuation of a safety-related system at their For systems that have multiple design functions, site.
the NRC staff's position is that some design functions may be within the scope of the maintenance rule while 2.
SSCs whose failure has caused a teactor scram others may be outside the scope of the rule. Failures of or actuation of a safety related system at a site components that affect a design function that is within with a similar configuration.
the scope of the maintenance rule would require correc-tive action and monitoring under the rule. For example, 3.
SSCs identified in the licensee's analysis (e.g.,
the components (piping, pumps, and valves) in the FSAR, IPE) whose failure would cause a reac-high-pressure coolant injection system (if PCI) that are for scram or actuation of a safety-related needed to perform the design function (injection of system.
high-pressure water into the reactor) would be included The only exception to items 2 and 3 above would within the scope of the rule because this is a safety-be a licensee who has demonstrated by an analysis (e.g.,
related function of the system. Ilowever, the compo-
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FSAR, IPE) and by operational experience that the de-nents that are only used for testing (e.g., test loop. sam-g sign or configuration of an SSC is fault-tolerant ple valves, bypass valves) might be excluded from the through redundancy or mstalled standby spares such scope of the rule unless they meet another scoping crite-that a reactor scram or actuation of a safety-related sys-rion (e.g., if they could cause failure of a safety-related tem is implausible. In these cases, the licensee may ex-SSC), because these components are not required for clude the SSC from the scope of the rule.
the coolant injection function of the llPCI.
1.2 Definition of Maintenance 1.1.2 SSCs Relied Upon To Mitigate For the purposes of the maintenance rule, mainte-Accidents or Transients or Used in nance activities are as described in the " Final Commis-Emergency Operating Procedures sion Policy Statement on Maintenance of Nuclear Pow-Nonsafety-related SSCs that are relied upon to mit-er Plants."7 This definition is very broad and includes igate accidents or transients or that are used in emergen-all activities associated with the planning, scheduling, cy operating procedures (EOPs) are included in the accomplishment, post-maintenance testing, and retum-scope of the rule by 10 CFR 50.65(b)(2)(i). NUMARC to-service activities for surveillances and preventive 93-01 states that only those SSCs that provide a signifi-and corrective maintenance. These activities are con-cant fraction of the mitigating function need to be in-sidered maintenance regardless of which organization cluded in the scope of the rule. The NRC staff considers performs the activity (e.g., maintenance, operations, this to mean that SSCs that are directly used to address contractors). This definition is referenced in i
l the accident or transient or explicitly used in the EOPs NUMARC 93--01. Some licensees have questioned the I
are within the scope of the rule, as are SSCs whose use guidance because in section 9.4.5 of NUMARC 93-01
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is implied and that provide a significant fraction of the an example of a failure that is not a maintenance-I mitigating function. Examples of SSCs that should be preventable functional failure (MPFF) is " failures due considered include communications and emergency to operational errors...." The operational errors referred lighting systems, which are necessary to successfully to in that example are those that are not associated with x
s I
mitigate accidents and transients and to use the EOPs, a maintenance activity.
although they may not directly address the accident or transient, or not be explicitly mentioned in the EOPs.
753 FR 9430, March 23,1988.
1.160 - 5
An example of an operator action that would not be 1.5 Monitoring Structures an MPFF would be improper closure of a valve while The maintenance rule does not treat structures dif-filling a tank that results in a pump trip followed by a ferently from systems and components. Experience reactor trip. An example of an operator action that with the rule and NUM ARC 934)1 during the pilot site would be an MPFF could be when an operator failed to visits and the initial period following the effective date reopen a suction valve for a pump following post-of the rule indicated that specific guidance for monitor-maintenance testing and the closed suction valve ing the effectiveness of maintenance for structures was caused pump failure during a subsequent demand.
needed, as structures present a different situation than do systems and components. The primary difficulty in 1.3,I,s,melm, ess implementing the rule for structures using NUMARC NUMARC 934)1 states that activities such as 934)1 was in establishing appropriate criteria for per-cause determinations and moving SSCs from the (a)(2) formance and monitoring structures under Paragraph
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to the (a)(1) category must be performed in a " timely" (a)(1) instead of Paragraph (a)(2).
4 manner. Some licensees have requested that the NRC The effectiveness of maintenance can be moni-(
staff provide a specific period that would be considered tored by using performance criteria or goals, or by con-
" timely " To be consistent with the intent of the mainte-dition monitoring. While it is acceptable to use perfor-nance rule to provide flexibility to licensees, the NRC mance criteria or goals, most licensees have found it staff does not etmsider it appropriate to provide a spe-more practical to use condition monitoring for struc-cific timeliness criterion. Licensees are to undertake tures. With certain exceptions (e.g., primary contain-and accomplish activities associated with the mamte-ment), structures do not have unavailability, and rarely nance rule in a manner commensurate with the safety have demands placed on their safety significant func-significance of the SSC and the complexity of the issue tions (e.g., maintain integrity under all relevant design being addressed.
basis events), which makes reliability monitoring impr etical.
1.4 MPFFs as an Indicator of Reliability NUMARC 934)1 states that performance criteria An acceptable structural monitoring program for for SSCs of high safetv significance should be estab-the purposes of the maintenance rule should have the lished to assure that reliability and availability assump-following ttributes.
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tions used in the plant-specific safety analysis are main-Consistent with the NUMARC 934)1 ap-tained or adjusted. NUMARC 934)1 further allows the proach for systems and components, most use of MPFFs as an indicator of reliability. The mainte-structures would be monitored in accordance nance rule requires that the performance of SSCs be with Paragraph (a)(2), provided there is not monitored commensurate with safety; however, the significant degradation of the structure.
maintenance rule does not require that the assumptions in the safety analysis be validated. Licensees who The condition of all structures within the scope a
choose to use their safety analyses as described in of the rule would be assessed periodically.The NUMARC 934)1 must be able to demonstrate how the appropriate frequency of the assessments number of MPFFs allowed per evaluation period is would be commensurate with the safety signif-consistent with the assumptions in the risk analysis. For icanee of the structure and its condition.
standby SSCs, this would require, at a minimum, a rea-Licensees would evaluate the results of the sonable estimate of the number of demands during that assessments to determine the extent and rate of time period.
any degradation of the structures. Deficiencies if a licensee desires to establish a reliability perfor-would be corrected in a timely manner mance criterion that is not consistent with the assump-commensurate with their safety significance, 4
tions used in the risk analysis, adequate technical justi-their complexity, and other regulatory fication for the perfoimance criterion must be provided.
requirements.
For some SSCs, an MPFF performance criterion may be too small to be effectively monitored and trended as A structure would be monitored in accordance required by the rule. In these cases, the licensee should with Paragraph (a)(1) if either (1) degradation establish performance or condition monitoring criteria is to the extent that the structure may not meet that can be monitored and trended so that the licensee its design basis or (2) the structure has de-can demonstrate that maintenance is effective.
graded to the extent that, if the degradation 1.160 - 6
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were allowed to continue uncorrected until the 1.7 Normilly Operating SSCs of Low Safety next normally scheduled assessment, the Significance f
. structure may not meet its design basis. The 1.7.1 Cause Determinations
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structure would continue to be monitored in accordance with Paragraph (a)(1) until the For all SSCs that are being monitored using plant-degradation and its cause have been corrected.
level performance criteria (i.e., normally operating SSCs oflow safety significance), the NRC staff's posi-l I
tion is that a cause determination is required whenever any of these performance criteria are exceeded (failed)
For structures monitored in accordance with in order to determine which SSC caused the criterion to I
Paragraph (a)(1), there would be additional be exceeded or whether the failure was a repetitive degradation-specific condition monitoring MPFF. As part of the cause determination, it would also and increased frequency of assessments until be necessary to determine whether the SSC was within I
the licensee's corrective actions are complete the scope of the maintenance rule and, if so, whether and the licensee is assured that the structure corrective action and monitoring (tracking, trending, can fulfill its intended functions and will not goal setting) under 10 CFR 50.65(a)(1) should be degrade to the point that it cannot fulfill its de-performed.
sign basis.
1.7.2 Unplanned Manual Scrams Consistent with the intent of the rule, licensees In order to monitor the effectiveness of mainte-should use their existing structural monitoring pro-nance for those SSCs monitored by plant-level criteria, grams (e.g., those required by other regulations or NUMARC 93-01 recommends that only those scrams codes) to the maximum extent practical.
that are automatically initiated be counted. The NRC staff's position is that all unanticipated scrams be con-sidered, including those scrams that are manually initi-l.6 Definition of Standby ated in anticipation of an automatic scram. The purpose (N
of this is not to discourage manual trips but rather to en-(
in NUMARC 93-01, standby SSCs of low safety sure that operators do not mask a maintenance perfor-significance must have SSC-specific performance cri-mance issue. Ifineffective maintenance is forcing plant j
teria or goals, similar to SSCs of high safety signifi-shutdowns, whether the trip is initiated automatically cance. NUM ARC 93-01 provides a definition of stand-or manually should not affect how licensees address the l
by. Some licensees have improperly interpreted this maintenance performance issue under the maintenance j
definition as meaning that SSCs that are energized are rule.
i normally operating. As stated in NUMARC 93-01,if the SSC only performs its intended function when initi.
1.7.3 Establishing SSC-Specific Performance Criteria ated by either an automatic or manual demand signal, the SSC is in standby.
The maintenance rule requires that licensees moni-tor the effectiveness of maintenance for all SSCs within Normally operating SSCs are those whose failure the scope of the rule. NUMARC 93-01 allows licen-would be readily apparent (e.g., a pump failure results sees to monitor SSCs of low safety significance with in loss of flow that causes a trip). Standby SSCs are plant-level criteria. NUMARC 93-01 notes that some those whose failure would not become apparent until normally operating SSCs of low safety significance the next demand, actuation, or surveillance. Only those cannot be practically monitored by plant-level criteria.
SSCs of low safety significance, whose failure would Licensees must ensure that the plant-level criteria es-i be readily apparent (because they are normally operat.
tablished do effectively monitor the maintenance per-ing), should be monitored by plant-level criteria.
formance of the normally operating SSCs oflow safety significance, or they should establish SSC-specific per-f rmance criteria or goals or use condition monitoring.
SSCs may have both normally operating and standby functions. In order to adequately monitor the For example, a licensee determined that the rod effectiveness of maintenance for the SSCs associated position indication system and the spent fuel pool pit s
with standby functions, licensees should develop SSC-cooling system were within the scope of the mainte-specific performance criteria or goals, or condition nance rule because they were safety-related at the li-monitoring.
censee's site. None of the three plant-level performance 1.160 -7 L
l l,
criteria described in NUMARC 93-01 (unplanned ing a repetitive MPFF. Therefore, the Paragraph (a)(1) automatic scrams, unplanned capability loss factor, or category could be used as a tool to focus attention on unplanned safety system actuations) would monitor the those SSCs that need to be monitored more closely. It is effectiveness of maintenance on these systems. There-possible that no (or very few) SSCs would be handled fore, additional plant-level performance criteria or under the requirements of Paragraph (a)(1). Ilowever, system-specific performance criteria must be the rule does not require this approach. Licensees could established.
also take the approach that all(or most) SSCs would be handled under Paragraph (a)(1) of the rule and none (or 1.8 Clarification of MPFFs Related to Design very few) would be considered under Paragraph (a)(2)
Deficiencies of the rule. Licensees may take either approach.
The third paragraph of Section 9.4.5 of NUMARC During the pilot site visits, licensees questioned 93-.01 provides guidance on the licensee,s options fol-whether a large number of SSCs monitored under Para-lowing a failure and on whether, as a result of the licens-graph (a)(1) would be used by the NRC as an indicator ce s corrective actions, subsequent failures would b of poor maintenance performance. The NRC staff as-considered MPFFs. In particular, this paragraph ad-sured the licensees that NRC management would not dresses failures caused by design deficiencies. Ideally, use the number of SSCs monitored under Paragraph licensees would make design modifications to elim[
(a)(1) as an indicator of maintenance performance nor nate the poorly designed equipment. Ilowever,if the li-would it be used in determining the systematic assess-censee determines that such an approach is not cost ef-ment of licensee performance (SALP) grade in the fective (e.g., the cost of modification is prohibitive)'
maintenance area. The number of SSCs monitored un-the licensee has two options:
der Paragraph (a)(1) can vary greatly because of factors i
that have nothing to do with the quality of the licensee's (1) Replace or repair the failed equipment and maintenance activities. For example, two identical make adjustments to the preventive mainte-plants with equally effective maintenance programs nance program as necessary to prevent recur-could have different numbers of SSCs monitored under rence of the failure. Subsequent failures of the Paragraph (a)(1) because of differences in the way sys-same type that are caused by inadequate cor-tem boundaries were defined (a system with three trains rective or preventive maintenance would be may be 6efined as one system at one plant while the MPFFs, and could be repetitive MPFFs.
same system may be defined as three separate systems at an identical plant) or because of differences in the (2) Perform an evaluation that demonstrates that way performance criteria were defined at the two plants the equipment can be run to failure (as de-(a licensee who takes a very conservative approach to scribed in Section 9.3.3 of NUMARC 93-01).
monitoring against the performance enteria would If the equipment can be run to failure, the li-have more SSCs in the (a)(1) category). The NRC staff censee can replace or repair the failed equip-also cautioned licensee managers that they should not ment, but adjustments to the preventive main-view the number of SSCs in the (a)(1) category as an tenance program are not necessary and indicator of performance since that attitude might in-subsequent failures would not be MPFFs.
hibit the licensees' staff from monitoring an SSC under Paragraph (a)(1) when a performance criterion has been 1.9 SSCs Considered Under 10 CFR 50.65(a)(1) exceeded or a repetitive MPFF has occurred. If there is Paragraph (a)(1) of the maintenance rule requires some doubt about whether a particular SSC should be that goal setting and monitoring be established for all monitored under Paragraph (a)(1) or Paragraph (a)(2),
SSCs within the scope of the rule except for those SSCs the conservative approach would be to monitor the SSC whose performance or condition is adequately con-under Paragraph (a)(1).
trolled through the performance of appropriate preven-tive maintenance as described in Paragraph (a)(2) of the 1.10 Use of Other Methods rule. In NUMARC 93-01, all SSCs are initially placed under Paragraph (a)(2) and are only moved under Para-Licensees may use methods other than those pro-graph (a)(1) if experience indicates that the perfor-vided in Revision 2 of NUMARC 93-01 to meet the re-mance or condition is not adequately controlled quirements of the maintenance rule, but the NRC will through preventive maintenance as evidenced by the determine the acceptability of other methods on a case-failure to meet a performance criterion or by experienc-by-case basis.
1.160 - 8
2.
OTHER DOCUMENTS REFERENCED IN (i.e., equipment in the switchyard) should be consid-NUMARC 93-01 ered for inclusion as defined in 10 CFR 50.65(b).
NUMARC 93-01 references other documents, but NRC's endorsement of NUMARC 93-01 should not be D. IMPLEMENTATION considered an endorsement of the referenced The purpose of this section is to provide informa-documents.
tion to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.
3.
INCLUSION OF ELECTRICAL Except in those cases.in which an apph. cant or 11-DISTRIBUTION EOUIPMENT censee proposes an acceptable alternative method for The monitoring efforts under the maintenance rule, complying with specified portions of the NRC's regu-
)
as defined in 10 CFR 50.65(b), encompass those SSCs lation., the methods described in this guide will be used that irectly and significantly affect plant operations, in the evaluation of the effectiveness of maintenance regardless of what organization actually performs the activities oflicensees who are required to comply with maintenance activities. Maintenance activities that oc-10 CFR 50.65. The guide will also be used to evaluate cur in the switchyard can directly affect plant opera-the effectiveness of emergency diesel generator mainte-tions; as a result, electrical distribution equipment out nance activities associated with compliance with 10 to the first inter-tie with the offsite distribution system CFR 50.63.
D(
1 b
1.160 - 9
+
I REGULATORY AND llACKFIT ANALYSES Separate regulatory and backfit analyses were not the level of protection of public health and safety be-prepared for this Revision 20f Regulatory Guide 1.160.
yond that currently provided by the Commission's reg-The regulatory analysis and the backfit analysis that ulations, and that the costs ofimplementing the rule are were prepared when this guide was first issued as a justified in view of this increased protection."* The re-draft, DG-1020, in November 1992, are still applica-gulatory analysis and backfit analysis for DG-1020 are ble. The backfit analysis prepared for DG-1020 con-available, in the file for Regulatory Guide 1.160, for in-cluded that no backfit was associated with the regulato-spection or copying for a fee in the Commission's Pub-ry guide because it was only providing guidance to lic Document Room,2120 L Street NW., Washington, implement the existing requirements of the mainte-DC; the PDR's mailing address is Mail Stop LL-6, nance rule. The Commission determined, on the basis Washington, DC 20555: phone (202)634-3273; fax of the backfit analysis performed for the maintenance (202)634-3343.
rule, ".. that backfitting of the requirements in the maintenance rule will provide a substantial increase in
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