ML20137Z471
| ML20137Z471 | |
| Person / Time | |
|---|---|
| Issue date: | 04/17/1997 |
| From: | Boger B NRC (Affiliation Not Assigned) |
| To: | Carns N, Laudenat R NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| RTR-REGGD-01.160, RTR-REGGD-1.160, TASK-*****, TASK-RE NUDOCS 9704240190 | |
| Download: ML20137Z471 (2) | |
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[6d 3 p* UNITED STATES
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4 s* NUCLEAR REGULATORY COMMISSION O -
I o, t WASHING'ON, D.C. 20$5M001 ! (/ b
- * * * $ April 17, 1997 Mr. Neil S. Cams Senior Vice President and Chief Nuclear Officer Northeast Nuclear Energy Company a
c/o Mr. Robert T. Laudenat Director-Nuclear Licensing Services P.O. Box 128 '
Waterford, CT 06385
SUBJECT:
RESPONSE TO NOVEMBER 14,199S, LETTER PROVIDING COMMENTS ON i DRAFT REGULATORY GUIDE 1051," MONITORING THE EFFECTIVENESS OF j MAINTENANCE AT NUCLEAR POWER PLANTS"
Dear Mr. Carns:
1 1
Thank you for providing comments on Draft Regulatory Guide 1051 (DG-1051), " Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," which was the proposed Revision 2 to Regulatory Guide 1.160 (RG 1.160) of the same title. In March 1997, the staff j issued RG 1.160, Revision 2, a copy of which is enclosed. This letter provides the staff response to the comments on DG-1051 provided in your letter dated November 14,1996.
Your letter provided two comments on DG-1051, both related to the discussion of emergency diesel generators (EDGs). The first comment was that DG-1051 conflicted with the endorsed l
industry guideline, NUMARC 93-01, " Industry Guideline for Monitoring the Effectiveness of '
Maintenance at Nuclear Power Plants,"in that DG-1051 states that all structures, systems, and components (SSCs) within the scope of the rule are required to have unavailability and reliability balanced in accordance with Paragraph 10 CFR 50.65(a)(3) of the maintenance rule, and NUMARC 93-01 only required that this balancing be performed for SSCs of high l safety significance. The second comment was that the EDG section of DG-1051 had guidance redundant to the guidance elsewhere in the draft regulatory guide that was l applicable to all SSCs and not specific to EDGs.
The EDG section in DG-1051 was not changed from that in RG 1.160, Revision 1. However, the staff agrees with the comment that some of the discussion in the EDG section is redundant and not exclusive to EDGs. The purpose of this section was to link the station ,
blackout rule (10 CFR 50.63) and the maintenance rule, and the guidance was intended to be l specific to EDGs and the station blackout rule. Therefore, the EDG section in RG 1.160, l Revision 2, has been revised to eliminate the redundant and non-station-blackout-specific discussion from the EDG section.
l The staff also agrees with the comment that NUMARC 93-01 specifically requires balancing I of unavailability and reliability of SSCs of high safety significance. However, the staff does .
not agree that the balancing and adjustments required by Paragraph (a)(3) of the maintenance rule are not applicable to SSCs of low safety significance. NUMARC 93-01 (, l
)
addresses balancing in Section 12.2.4, " Optimizing Availability and Reliability for SSCs." For i SSCs of high safety significance, the balancing must explicitly address reliability and 9704240190 970417 l l
PDR REGOD 1 01.160 R PDR [, ? p6 i - I I gkyC\ %c MO E @.f RENTER M97-fD'
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l availability. For SSCs of low safety significance, the balancing is achieved by meeting the j- SSC-specific or plant level criteria or goals, as appropriate.
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if a performance criterion or goalis not met, Section 9.4.4 of NUMARC 93-01, l " Unacceptable Performance or Failure Cause Determination and Dispositioning of SSCs from j
(a)(2) to (a)(1)," requires that a cause determination be performed. The cause determination -
) includes corrective actions to preclude recurrence and an evaluation of whether the
. performance criterion or goal should be modified. . The corrective actions should address whether the maintenance program is effective and whether the performance criteria.and
[
' goals for the SSC are appropriate. Licensees would adjust the maintenance program as necessary (including giving consideratio'n as to whether the reliability and availability of the !
SSC are appropriate) as required by Paragraph (a)(3) of the maintenance rule as a result of l
the actions taken in response to the cause determination.
If you have any questions regarding the staff response to your comments, please contact Mr. Richard P..Correia, Chief, Reliability and Maintenance Section, Quality Assurance and Maintenance Branch, (301) 415-1009. l Sincerely, i
hY Bruce A. B ger, Director Division of Reactor Controls and Human Factors Office of Nuclear Reactor Regulation
Enclosure:
RG 1.160, Revision 2 Docket Nos. 50-245 50-336 50-423
no U.S. NUCLEAR REGULATORY COMMISSION Revision 2 C (p++(* )
4 OFFICE OF NUCLE i
REGULATORY GUIDE 1.160
. (Draft was DG-1051) I MONITORING THE EFFECTIVENESS OF
. MAINTENANCE AT NUCLEAR POWER PLANTS A. INTRODUCTION consistent with the NRC's defense-in-depth philoso-The NRC published the maintenance rule on phy. Maintenance is also important to ensure that de-July 10,1991, as Section 50.65, " Requirements fe' s gn assumptions and marginsin the original design ba-Monitoring :he Effectiveness of Maintenance at No- sis are maintained and are not unacceptably degraded.
- l. clear Power Plants," of 10 CFR Part 50, " Domestic Li- Therefore, nuclear power plant maintenance is clearly i
censing of Production and Utilization Fadlities." The important in protecting public health and safety.
NRC's determination that a maintenance rule was Paragraph (a)(1) of 10 CFR 50.65 requires that i
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, 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 such factors as the number of transients and challengts functions. Such goals are to be established commensu-
, \.j to safety systems and the associated need for operabit.
i rate with safety and, where practical, take into account ity, availability, and reliability of safety equipment. In industry-wide operating experience. When the perfor-addition, good maintenance is also important in provid.
i mance or condition of an SSC does not meet estab-ing assurance that failures of other than safety-related 'isSed goab, appropriate corrective action must be Mk-structures, system 3, and components (SSCs) that coul J 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),
I Paragraph (a)(1) of 10 CFR 50.65 applies only to the NRC Memorandum to An Commissioners from J. Taylor on "Mainte. extent that the licensee must monitor the performance g
nance Rulemaking," June 27,1991. Copies arc avadabic for inspection or copying for a fee from the NRC Public Document Room at 2120 L stract. of Condition of all SSCs associated with stoing, Con-Nw., Washington, DC; the PDR's mailing address is Mail Stop LL-6,trollin8, and maintaining spent fuel in a safe condition, hhington, DC 20555; phone (202)6u-3273; rax (202)6u-3u3.
in a manner sufficient to provide reasonable assurance USNRC REGUI.A rORY GUIDES The gwoes we issued m lhe fosiommg ten broad dnnesons Reg;larcry Guules we issued to dancnce and make evegataa to to pibhc suchirdorr,w tcn as methods acceptable to the Nf4C star for implemereng spectAc parts of the Com-nJared t Power Reactors 6 Products and needed NRt, einew tot per
""l't "e*,nt":"e2'"t::W"- e 3 ves and at Hearth gge;e,g ,,.g,dto"T.o"n.=:'?nlrW"3"s'a*O= ; B:re -;","*n,$, Fecoon
, y m;ndmoo re s- ~--
, 4 == '"*'"** a-This guide was asued alter considerebon of comments recoved from tre pubhc Com-
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(N.,p/ Wntten comments may be outmned to the Rules Rev ow and Directnres Rranchissuert DF PS gudes may eso be purchased from the Nabanal Techruce informahan Sennce on ADM, U S Nwaaer negumory Cornmesson. WasW, DC 20555-Ouut .
a etwicing order basis Detade on this nennee may De obtened by armnD NTIS. ESS Port Royal Road, Sonngned, VA 2216t MOSZ 7bz- W ne
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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); at 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- k condition of an SSC is being effectively controlled related structures, systems, and compo- i a
through the performance of appropriate preventive nents from fulfilling their safetv related '
l maintenance, such that the SSC remains capable ofper- function; or I
, forming its intended function.
l (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. I ciated goals and preventive maintenance activities be Paragraph (c) of 10 CFR 50.65 states that the rule evaluated at least every refueling cycle provided the in-provisions are to be implemented by licensees no later terval between evaluations does not exceed 24 months.than July 10,1996.
The evaluations must be conducted taking into account, l where practical, industry-wide operating experience. This Regulatory Guide 1.160 is being revised to i Adjustments must be made where necessary to ensure ered rse Revismn 2 of NUMARC 93-01, " Industry that the objective of preventing failures of SSCs (>uideline for Monitoring the Effectiveness of Mainte-through maintenance is ap'propriately balanced against ance at buclear Power Plants"4 (April 1996), which !
the tbjective of minimizing unavailability of SSCs be- has been updated by the Nuclear Energy Instiiute. The
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cause of monitoring or preventive maintenance. In per- regul tory guidance is intended to provide flexibility i forming monitoring and preventive maintenance activ- for a licensee to structure its maintenance pregram m ities, an assessment of the total plant equipment that is ce rd nee with the safety significance of those SSCs out of service should be taken into account to determine within the scope of the rule.
l 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 toinclude safety-related and nonsafety-related ment md Budget, approval number 3150-0011. The SSCs as follows. l NRC may not conduct or sponsor, and a person is not required to respond to, a collection ofinformation un-(1) Safety-related structures, systems, or compo less it displays a currently valid OMB control number.
nents that are relied t.pon 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-related SSCs are capable of performing their intended functions and (2) for non-(2) Nonsafety-related structures, systems, or com- safety-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 efrective of safety-related systems are minimized.
August 28,1996. See 61 FR 39278, July 19,1996,"Decomrnissionmg of Nuclear Power Peactors."
3
%is Paragraph (b)(1)of the maintenance rule was changed in the fmal 'This document is availabk ror inspection or copymg for a fee in ti$e NRC rulemaking for*' Reactor S te Cnteria includmg Seismic and Earthquake Public Document Room. 2120 L street NW. , Washington, DC; the PDR's Engincenng Cnteria for Nuclear Power Plants," December 1 L 1996. See 6I FR 65157. mading address is Mad Stop LL-6, washington, DC 20555; phone (202)634-3273; ram (202)634-3343.
1.160 - 2
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DEVELOPMENT OF INDUSTRY GUIDELINE, NUMARC 93-01 PLANT, SYSTEM, TRAIN, AND COMPONENT MONITORING LEVELS
/q The nuclear industry developed a documen ,
The extent of monitoring may vary from system t
\ NUMARC 93-01, " Industry Guideline for Monitorin; the Effectiveness of Maintenance at Nuclear Por er system depending on the system's importance ro s Plants"(May 1993),4 that provides guidance to licen- Some monitoring at the component level rnay be nec sary; however, it is envisioned that most of the monitor-sees regarding implementation of the maintenance .ule.
This document was nrepared by NUMARC. A veritica- ~ ing could be done at the plant, system, or
- rain level.
i 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 guidance document on several representative systems. system or train level. Except as noted in the Regulatory A number of changes were made to the NUMARC Position of this guide, normally operating SSCs with guidance document based on the results of th: V& V ef- low safety significance may be monitored through plant-level performance criteria, including unplanned fort. The NRC staff reviewed this document and found that it provided acceptable guidance to licensees. In scrams, safety system actuations, or unplanned capa-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 1993 version of NUMARC 93-01. In January 1995, the caused the SSC to be placed in the Paragraph (a)(I) category is being corrected.
NRCstaffissued Revision I to Regulatory Guide 1.160 to reRect the amendment to 10 CFR 50.65(a)(3) that USE OF EXISTING LICENSEE PROGRAMS changed the requirement for perfctming 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 speciEcation surveillance From September 1994 to March 1995, the NRL, .. testing, to satisfy monitoring requirements. Such activ-staff performed a series of nine pilot site visits to verify ities could be m.tegrated with, and provide the basis for,.
the usabihty and adequacy of the draft NRC mainte- the requisite level of monitoring. Consistent with the nance rule inspection procedure and to determme the underlying purposes of the rule, maximum Hexibility strengths and weaknesses of the implementation of the should b: offered to licensees in establishing and modil rule at each site that used the guidance provided in NU- fym.g toeir momtoring ad,ities. .
MARC 93-01. The findings are described in NUREG-1521 "Lessoris Learned from Early imple. USE OF RELIABILITY-BASED PROGRAMS mentation of the Maintenance Rule at Nine Nuclear
- Licensees are encouraged to consider the use of Power Plants"5 (June 1995). The NRC staff concluded reliability-based methods for developing the preven' that the requirements of the rule could be met more con- tive maintenance programs covered under 10 CFR-sistently across the industry if some clarifying guid- 50.65(a)(2); however, the use of such methods is not 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 to discuss proposed revisions to NUMARC 93411 that The maintenance rule requires that goals be estab-would address the findings noted during the site visits, lished commensurate with safety. In order to imple-Revision 2 to NUMARC 934)1 (April 1996) resulted ment this requirement, NUMARC 934)1 established from these meetings. two safety significance categories, " risk-significant" and "non-risk-significant." The process for placing l SSCs in either of these two categories is described in i
section 9.0 of NUMARC 93-01. The statements of S consideration for the rule use the terms "more risk-Copies are avaitable ai current rates from the U.s. Government Pnnting significant" and "less risk significant." NRC inspec-Office, P.O. Hon M082. washmgton, DC 20402-9328 (telephone 4 e s (202)M 2-2249). or from the National Technicat intormation Service tionbyprocedure (IP) 62706 uses the terms "high safety
\ wnting NTIS at $285 Port Royal Road. springrield. VA 22161. Copies significance" and " low safetI'si bvnificance-." After dis-
%) are available for mspection or copymg for a ree from ihe suC Public oocument Room at 2120 L street Nw., Washingto DC. ^e PDP's cussions with industry representatives, the NRC staff mahng address is Mad stop 11-6 washmgton, DC 2ni$h telephone has determined that the preferred terminology is "high co2m4-32n ran t202)634-nu safety significance" and " low safety significance."
i un_,
- Some' licensees may elect to det;ne 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.
categenes, which would be acceptable if hese t alterna-tive categories are defined in the licensee's procedures EMERGENCY DIESEL GENERATORS and used in a consistent manner.
Industry- and NRC-sponsored probabilistic risk SAFETY SIGNIFICANCE RANKING analyses (PRAs) have shown the safety significance of METIlODOLOGY mergency ac power sources. The station blackout rule
( 10 CFR 50.63) required plant-specific coping analyses The NRC staff end rses the use of the SSC safety to ensure that a plant could withstand a total loss et ,e 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 meetir.g the requirements of the main.
ac power. During the station blackout reviews, most li-tenance rule.6 Ilowever, because of some unique eersees:
(1) made a commitment to implement an
' aspects of the maintenance rule, including the fact that standby SSCs oflow safety significance are treated the emergency diesel generator (EDG) reliability program 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 endersement for other applications.
xill implement an equivalent program. Subsequently, These issues were discussed in SECY 95-265, "Re-sponse to August 9,1995, Staff Requirements Memo- utilities docketed commitments to maintain their se-levai target rdiability values (i.e., maintain the emer-randum Request to Analyze the Generic Applicability gei ey diese; generator target reliability of 0.95 or of the Risk Determination Process Used in implement-ing the Maintenance Rule."4 0.975). Those values could be used as a goal or as a per-formance criterion for emergency diesel generatos reli-ability under the maintenance rule. {
APPLICAlllLITY OF APPENDIX 11 TO 10 CFR l PART 50 1 Emergency diesel generator unavailability values With regard to the scope of the maintenance rule, as were also assumed in plant-specific individual plant ex-stated in Paragraph (b) of the rule, it is understood that amination (IPE) analyses. These values should be balance of plant (BOP) SSCs may have been designed compared to the plant-specific emergency diesel gener-and built with normal industrial quality and may not Mor unavailability data regularly monitored and re-meet the standards in Appendix B te 10 CFR Part 50. It porteu as industry-wide plant performance informa-is not the intent of the NRC staff to require licensees t" tion. These values could also be used as the basis for a generate paperwork to document the basis for the de- goal or performance criterion under the maintenance sign, fabrication, and construction of BOP equipment rulo in addition,in accordance with Paragraph (a)(3) of (i.e., BOP equipment need not mee t the requirements of the rule, licensees must periodically balance unavail-Appendix B to 10 CFR Part 50). ability and reliability of the emergency diesel generators.
Each licensee's maintenance efforts should mini-mize failures in both safety-related and BOP SSCs that C. REGULATORY POSITION affect safe operation of the plant. The effectiveness of
- 1. NUMARC 93-01 maintenance programs should be maintained for the operational life of the facility. Revision 2 of NUMARC 93-01," Industry Guide-line for Monitoring the Effectiveness of Maintenance at SWITCIIYARD MAINTENANCE ACrlVITIES Nuclear Power Plants,"4 provides methods that are ac-As noted in the Regulatory Position of this guide, ceptable to the NRC staff for complying with the provi-there may be a need to address maintenance activities sions of 10 CFR 50.65 with the following provisions and clarifications, that occur in the switchyards that could directly affect 1.1 Scope of the Rule
- The staff is developing guidance the addresses the acceptable enteria for the use of PRAs in nsk-informed regulatory matters. The NRC staff 1.1.1 "Could Cause" Criterion anucipates than a lature revision to this Regulatory Guide t.160 would Durin8 the nine Eilot site visits, the NRC staff rec-refennce the guidance. when avaitable, to make the NRC staff's guid-
- " n the use of PRA in the maintenance rule consistent wen the NRCognized that some licensees interpreted the words in staff.s guidance in other areas o' nsk. informed regulation. The "5duun mit be encounged io use this guidance as thai nme. ection 8.2.1.5 of NUMARC 93-01 to mean that only those SSCs that had actually caused a plant scram or 1.160 -4
_, . . . _ \
i i
i-safety system actuation needed to be included within ;
1.1.3 Function Versus System '
the reope of the rule. The NRC staff's position is that p the SSCs to be included under the criterion "could I he rule provides criteria todetermine which SSCs (s cause a reactor scram or actuah.on of a safety system.. must be included within the scope of the rule. Alterna-should not be limited to SSCs that "did cause" or tively, licensees may use a functional basis te determine I "could likely cause." This position was discussed in which SSCs must be monitored within the scope of the1 e
NUREG-1526, " Lessons Learned fn m Early imple- rt.t . That is, the licensee may determine all the fune-mentation of the Maintenance Rule at Nine Nucleaf tions performed by the SSCs and include within the
' I Power Plants"(June 1995).5 Licensees should consider scope of the maintenance rule ordy thos.: . ncticas, anJ i the following SSCs to be within the scope of the rule- the associated SSCs that fulfill those functions, that meet the scoping criteria of the rule.
1.
SSCs whose failure has caused a reactor senm 1.1.4 Systems with Meltiple flesign Functions or actuation of a safety-related system at their site. For systems that have multiple design function..
the NRC staff's position is that some design functions
- 2. may be within the scope of the maintenance rule while SSCs whose failure has caused a reactor scram others may be outside the scope of the rule. Failures of or actuation of a safety-related system at a site with a similar configuration. components that affect a design function that is within the scope of the maintenance rule would require correc-
- 3. tive action and monitoring under the rule. For example.
SSCs identified in the licensee's analysis (e.g.,
FSAR, IPE) whose failure would cause a reac- the c< mpenents (piping, pumps, and valves) in the high-pressure coolant injection system (HPCI) that are for scram or actuation of a safety-related system. needed to perform the design function (injection of 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. However, the compo-FSAR, IPE) and by operational experience that the de- nents that are only u3ed for testing (e.g., test loop, sam-sign or configuration of an SSC is fault-tolerant val E valves) might be excluded from the through redundancy or mstalled standby spares such scope of the rule unless they meet anather scoping erite-that a reactor scram or actuation of a safetprelated sys-rion (e.g., if they could cause failure of a safety-related tem is unplausible. 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 IIPCI.
1.1.2 SSCs Relied Upon To Mitigate l ..: Definition of Maintenance Accidents or Transients or Used in For the purposes of the maintenance rule, mainte-Emergency Operating Procedures nance activities are as described in the " Final Commis-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-cy operating procedures (EOPs) are included in the all activities associated with the planning, scheduling, scope of the rule by 10 CFR 50.65(b)(2)(i). NUM ARC accomplishment, post-maintenance testing, and return-93-01 states that only those SSCs that provide agnifi- to-service activities for surveillances and preventive cant fraction of the r.:itigating function need to be in- and corrective maintenance. These activities are con cluded in the scope of the rule. The NRC staff considers sidered maintenance regardless of which organization ihis to mean that SSCs that are directly used to address performs the activity (e.g., maintenance, operatio" the accident or transient or explicitly used in the EOPs contractors). This definition is referenced , r.
are within the scope of the rule, as are SSCs whose use NUMARC 93-01. Some licensees have questioned the is implied and that provide a significant fraction of the guidance because in section 9.4.5 of NUMARC 93-01 mitigating function. Examples of SSCs that should be an example of a failure that is not a maintenance-considered include communications and emergency preventable functional failure (MPFF) is " failures due to operational errors.. " The operational errors referred lighting systems, which are necessary to successfully d mitigate accidents and transients and to use the EOPs, to in that example are those that are not associated with although they may not directly address the accident or a maintenance activity.
transient, or not be explicitly mentioned in the EOPs. 7 5HP.900, March 23,1988.
,.n -
An example of an operator action that would not be 1.5 Monitoring Structures
' an MPFF would be improper closure of a valve while filling a tank that resulk in a p ~ip fol!owett by 1 The iaaintenance rule does not treat structures dif-reactor trip. An example of an operator action that ferently from systems and components. Experience would be an MPFF could be when an operator failed to w th the rule and NUMARC 93-01 during the pilot site I visits and the initial period following the effective date reopen a suction valve for a pump following post-maintenance testing and the closed suction valve of the rule indicated that specific guidance for monitor-caused pump failure during a subsequent demand. ing the effectiveness of maintenance for structures was needed, as structures present a different situation than 1.3 T,melm, i ess do ystems and components. The primary diSulty in implementing the rule for structures using NUMARC NUMARC 93411 states that activities such as 93-01 was in establishing appropriate criteria for per-cause determinations and moving SSCs from the (a)(2) to the (a)(1) category must be performed in a " timely' formance and monitoring structures under Paragraph (a)(1) instead of Paragraph (a)(2).
manner. Some licensees have requested that the NRC staff provide a specific period that would be considered h effectivenesa of maimenance can be moni-
" timely." To be consistent with the iment of the mainte- tored by using performance criteria or goals, o$ by con-nance rule to provide Dexibility to licensees, the NRC dition monitoring. While it is acceptable to use perfor-staff does not consider it appropriate to provide a spe-mance criteria or goals, most licensees have found it citic timeliness criterion. Licensees are to undertake more practical to use condition monitoring for struc-and accomplish activities associated with the mainte- With certain exceptions (e.g., primary contain-cance rule in a manner commensurate with the safety ment), Stutures do not have unavailability, ad rarely significance of the SSC and the complexity of the issue Mve demands placed on their safety significant fune-being addressed. t ons (e.g.. maintain integrity under all relevant design basis events), which makes reliability monitoring 1.4 MPFFs as an Indicator of Reliability I
- P'" #"
NUMARC 93-01 states that performance criteria An cceptable structural monitoring program for for SSCs of high safety significance should be estab- the purposes of the maintenance rule should have the lished to assure that reliability and availability assump. following rtributes, tions used in the plant-specific safety analysis are main-tained or adjusted. NUM ARC 934)1 further allows the Consistent with the NUMARC 934)1 ap- i use of MPFFs as an indicator of reliability. The mainte" proach for systems and components, most l nance rule requires tha* the performance of SSCs be structures would be monitored in accordance monitared commemurate woh safety; however, the with Paragraph (a)(2), provided there is not i maintenance rule does not require that the assumptions significant degradation of the structure.
in the safety analysis be validated. Licensees who .
choose to use their safety analyses as described in The condition of all structures within the scope of the rule would be assessed periodically. The NUMARC 93-4)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 standby SSCs, this would require, at a minimum, a rea- icance of the structure and its condition.
sonable estimate of the number of demands during that .
Licensees would evaluate the results of the time period.
assessments to determine the extent and rate of If a licensee desires to establish a reliability perfor- any degradation of the structures. Deficiencies mance criterion that is not consistent with the assump- would be corrected in a timely manner tions used in the risk analysis, adequate technical justi- commensurate with their safety significance, fication for the performance criterion must be provided. their complexity, and other regulatory requirements.
For some SSCs, an MPFF performance criterion may be too small to be effectively monitored and trendeu as .
required by the rule. In these cases, the licensee should A structure would be monitored in accordance 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) .he structure has de-can demonstrate that maintenance is effective.
graded to the extent that, if the degradation 1.160 - 6
were allowed to continue uncorrected until the
- 1.7 Normally Operating SSCs of Low Safety next normally scheduled assessment, the Significance strumre me 't meet its desigt. basis. The G structure would continue to be monitored m.
accordance with Paragraph (a)(1) until the 1.7.1 L,ause Determm.ations For all SSCs that are being monitored using plant degradation and it cause have been corrected. level performance criteria (i.e., normally operatin SSCs of low safety significance), the NRC staff's posi tion is that a cause determination is required wheneve a
any of these performance criteria are excecded (failed For structures monitored in accordance with Paragraph (a)(1), there would be additional in order to determine which SSCcaused a criterion t degradation-specific condition monitoring be exceeded or whether the failure was a repetitivt and increased frequency of assessments until MPFF. As part of the cause determination, it would also
/
the licensee's corrective actions are comp'ere be necessary to determine whether the SSC was within and the licensee is assured that the struernre de scope of the maintenance rule and, if so, whether can fulfill its intended functions and will not corrective action and monitoring (tracking. trendine. '
degrade to the point that it cannot fulfill its de- coal setting) under 10 CFR 50.65(a)(1) should be sign basis. performed.
1.7.2 Unplanned Manual Scrams Consistent with the intent of the rule, licenset ,
shauld use their existing structural monitoring pro- in order to monitor the effectiveness of mainte-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 unamicipated scrams be con-sidered, including those scrams that are manually initi-1.6 Definition of Standby ated in anticipation of an automatic scram. The purpose of this is not to discourage manual trips but rather to en.
(nU) in NUMARC 93-01, standby SSCs of low safety significance must have SSC-specific performance cri- sure that operators do not mask a maintenance perfor-teria or goals, similar to SSCs of high safety signifi- mance issue. Ifineffective maintenance is forcing plant cance. NUMARC 93-01 provides a definition of stand- shutdowns, whether the trip is initiated automatically or manually should not affect how licensees address the by. Some licensees have improperly interpreted this maintenance performance issue under the maintenance definition as m:aning that SSCs that are energized are rule.
normally operating. As stated in NUMARC 93-01, it the SSC only performs its intended function when initi. 1.7.3 Establishing SSC--Specific Performance ated by either an automatic or manual demand signal, Criteria 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-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 rhould establish SSC-specific per-SSCs may have both' normally operatirg and f rmance criteria or goals or use condition monitoring.
standby functions. In order to adequately monito "le For example, a licensee determined that the rod n effectiveness of maintenance for the SSCs associated position indication system and the spent fuel pool pit (v) with standby functions, licensees should develop SSC-specific performance criteria or goals, or condition cooling system were wi'hin the scope of the mainte-nance rule because they were safety-related at the li-monitoring. 1 censee's site. None of the three plant-level performance 1.160 - 7
criteria described in NUMARC 9341 (unplanned automatic scrams, unplanned capability loss factor, or ing a repetitive MPFF. Therefore, the Paragraph (a)(1) unplanned safety system actuations) would monitor the category could be used as a tool to focus attention on effectiveness of maintenance on these systems. There- those SSCs that neel to be monitored f more closel . It is tere, additional plant level performance criteria or possibit that no (or very few) SSCs would be handled system specific performance criteria under the requirements of Paragraph (a)(1). However, established.
must be the role does not require this approach. Licensees could also taxe ihe approach that all(or most) SSCs would be 1.8 Clarification of MPFFs Related to Design handled under Paragraph (a)(1) of the rule and none (or Deficiencies very few) would be considered under Paragraph (a)(2)
The third paragraph of Section 9.4.5 of NUMARC the rule. Licensees may take either approach.
of 9341 provides guidance on the licensee's options fol. ..
During the pd.or site visits, licensees questioned lowing a failure and on whether, as a result of the whether licens- a large number of SSCs monitored under Para-ce s corrective actions, subsequent failures would be 1) would be used by the NRC as an indicator considered MPFFs. In particular, this paragraph of ad- poe maintenance performance. The NRC staff as-dresses failures caused by design deficiencies. sured Ideally, the licensees that NRC management would not licensees would make design modificationsme to eh. .
use the number of SSCs monitored under Paragraph nate the poorly designed equipment. However, if the li- (a)( ) at a .indicator of maintenance performance not censee determines that such an approach is not cost ef-* "* ' " "I""* * "S
- "Y " * #
fective (e.g., the cost of modification is prohibiti"e), *""' "I ""# E# "" "'" N"'
the li;ensee has t.vo options: E * #
m intenanc area. The number of SSCs monitored un-der Paragraph (a)(1) can vary greatly because of factors (1) Replace or repair the failed equipment and that have nothing to do with the quality of the licensee's make adjustments to the preventive mainte- i g Meies For example, two identical nance program as necessary to prevent recut'
, effective maintenance programs rence of the failure. Subsequent failures of the same type that are caused by madequate cor-could have different numbers of SSCs moc.itored under Paragraph (a)(1) because of differences in the way sys-rective or preventive maintenance would be tem boundaries were defined (a system with three trains MPFFs, and could be repetitive MPFFs.
may be defined as one system at one plant while the m ty be defined as three sepaute systems (2) Perform an evaluation that demonstrates that plant) or because of differences in the at an identical the equipment can be un to failure (as de- nv performnce criteria were defined at the two plants scribed in Section 9.3.3 of NUM ARC (a l'icensee 93-01). who takes a very conservative approach to if tf e equipment can be run to failure, the li- monitoring ap. inst the performance criteria would censee can replace or repair the failed equip- have more SSCs in the (a)(1) category). The NRC staff ment, but adjustments to the preventive main- also cautioned licensee managers that they should not tenance program are not necessary and view the number of SSCs in the (a)(1) category as an subsequent failures would not be MPFFs.
indicator of performance since that attitude might in-hibit the licensees' staff from monitoring an SSC under
.9 SSCs Considered Under 10 CFR 50.65(a)(1)
Paragraph (a)(1) when a performance criterion has been Paragraph (a){l) of ;he maintenance rule requires exceeded or a repetitive MPFF has occurred. If there is t goal setting and monitoring be established for all some doubt about whether a particular SSC should be Cs within the scope of the rule except for those SSCs monitored under Paragraph (a)(1) or Paragraph (a)(2),
ose performance or condition is adequately con- the conservative approach would be to monitor the SSC under Paragraph (a)(1).
lled through the performance of appropriate preven-e maintenance as described in Paragraph (a)(2) of the
, e. In NUMARC 9341, all SSCs are initially placed 1.10 Use of Other Methods er Paragraph (a)(2) and are only moved under Para-ph (a)(1) if experience indicates that the perfor- Licensees may use methods other than those pro- i nce or condition is not adequately controlled vided in Revision 2 cf NUMARC 9341 to meet the re.
ough preventive maintenance as evidenced byquirements the of the maintenance rule, but the NRC will ure to meet a performance criterion or by experienc-determine by the acceptability of other methods on a case-1 se buis.
1.160 -8 P - - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - - -
1-i 2.
OTHER DOCUMENTS REFERENCED IN NUMARC 93-01 (i.e., equipment in the switchyard) should be consi.
ered for inclusion as defined in 10 CFR O NRC'sendorsementofNUMARC93-01shouldnotbeNUMARC 93-01 ref considered an endorsement of the referenced D. IMPLEMENTATION documents.
.The purpose of this section is to provide informa t;on to applicants and licensees regarding the NR(
- 3. staff's plans for using this regulatory guide INCLUSION OF ELECTRICAL DISTRIBUTION EOUIPMENT I,xcept in th se e ses in which an applicant or h.
i censee proposes an acceptable alternative method fo
! The monitoring efforts under the maintenance rule, as defined in 10 CFR 50.65(b), encompass those SSCs complying with specified portions of the NRC's regu-i lations, the methods described in this guide will be used that directly and significantly affect plant operations, j_ in the evaluation of the effectiveness of maintena regardless of what organization actually performs the j activities of licensees 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.
l 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 i;;ter-tie with the offsite distribution system CFR 50.63.
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e 1.160 - 9
REGUIATORY AND HACKFIT ANALYSES Separate regulatory and backfit analyses were not prepared for this Revision 2 of Regulatory Guide 1.160.the level of protection of public health and safety be-The regulatory analysis and the backtit analysisyond that that currently provided by the Commission's reg-were prepared when this guide was first issued as a ulations, and that the costs ofimplementing the rule are draft, DG-1020, in November 1992, are still applica- justified m view of this increased protection."* The re-ble. The backfit analysis prepared for DG-1020 con- gulatory analysis and backfit analysis for DG ""9 are cluded that no backfit was associated with the regulato; available. in the file for Regulatory Guide 1.160, for m-ry guide because it was only providing guidance to spection or copy ing for a fee in the Commission's Pub-implement the existing requirements of the mainte- lic Document Room,2120 L Street NW., Washington, nance rule. The Comruission determined, on the basis DC the PDR's mailing address is Mail Stop LL-6, of the backfit analysis performed for the maintenance Washington, DC 2055.C phone (202)634-3273; fax rule, " (202)634-3343.
that backfitting of the requirements in the -
maintenance rule will provide a substan:ial increase in !
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