Regulatory Guide 1.160

Monitoring the Effectiveness of Maintenance at Nuclear Power Plants

ML031430362
Person / Time
Issue date:	01/31/1995
From:	Office of Nuclear Regulatory Research
To:
References
DG-1031 RG-1.160, Rev 1
Download: ML031430362 (9)

U.S. NUCLEAR REGULATORY

COMMISSION

Revision 1 January 1995 REGULATORY

GUIDE OFFICE OF NUCLEAR REGULATORY

RESEARCH REGULATORY

GUIDE 1.160 (Draft issued as DG-1031)MONITORING

THE EFFECTIVENESS

OF MAINTENANCE

AT NUCLEAR POWER PLANTS

A. INTRODUCTION

The NRC published the maintenance rule on July 10, 1991, as Section 50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," of 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities." The Commission's determination that a maintenance rule was needed arose from the conclusion that proper maintenance is essential to plant safety. As discussed in the regulatory analysis for this rule, 1 there is a clear link between effective maintenance and safety as it relates to such factors as the number of transients and challenges to safety systems and the associated need for operability, availability, and reliability of safety equipment.

In addition, good maintenance is also important in providing assurance that failures of other than safety-related structures, systems, and components (SSCs) that could initiate or adversely affect a transient or accident are minimized.

Minimizing challenges to safety systems is consistent with the Commission's defense-in-depth philosophy.

Maintenance is also important to ensure that design INRC Memorandum to All Comnissioners from J. Taylor on"Maintenance Rulemaking June 27, 1991. Copies are avail-able for inspection or copying for a fee from the NRC Public Document Room at 2120 L Street, NW., Washington, DC; the PDR's mailing address is Mail Stop L-6, Washington, DC 20555; phone (202)634-3273;

fax (202) 634-334

3. USNRC REGUIATORY

GUIDES Regulatory Guldes areissued todescrlbe and make avallableto the public such Information as methods acceptable to the NRC staff for Implement- Ing specific parts of the Commission's regulations, techniques used by the staff In evaluating specific problems or postulated accidents, and data needed by the NRC staff In Its review of applications for permits and llcenses.

Regulatory Guldes are not substitutes for regulatlons, and com-pilance with them Is not required.

Methods and solutions different from those set out In the guides will be acceptable If they provide a basis for the findings requisite to the Issuance or continuance of a permit or llcense by the Commission.

This gulde was Issued ater consideratlon of comments recelved from the public. Comments and suggestlons for Improvements In these guides are encouraged at all times, and guides will be revised, as approprlate, to accommodate comments and to reflect new Informatlon or experience.

Written comments may be submitted to the Rules Review and Directives Branch, DFIPS, ADM, U.S. Nuclear Regulatory Commisslon, Washing-ton, DC 20555-0001.

assumptions and margins in the original design basis are maintained and are not unacceptably degraded.Therefore, nuclear power plant maintenance is clearly important in protecting the public health and safety.Paragraph (a)(1) of 10 CFR 50.65 requires that power reactor licensees monitor the performance or condition of SSCs against licensee-established goals in a manner sufficient to provide reasonable assurance that such SSCs are capable of fulfilling their intended functions.

Such goals are to be established commensurate with safety and, where practical, take into account industry-wide operating experience.

When the performance or condition of an SSC does not meet established goals, appropriate corrective action must be taken.Paragraph (a) (2) of 10 CFR 50.65 states that monitoring as specified in paragraph (a)(1) is not required where it has been demonstrated that the performance or condition of an SSC is beirg effectively controlled through the performance of appropriate preventive maintenance, such that the SSC remains capable of performing its intended function.Paragraph (a)(3) of 10 CFR 50.65 requires that"Performance and condition monitoring activities and associated goals and preventive maintenance activities shall be evaluated at least every refueling cycle provided the interval between evaluations does not The guldes are Issued In the following ten broad divisions:

1. Power Reactors 2. Research and Test Reactors 3. Fuels and Materials Facilltles

4. Environmental and Sting 5. Materials and Plant Protectlon

6. Products

7. Transportatlon

8. Occupational Health 9. Antitrust and Financial Revlew 10. General Coples of Issued guides may be purchased from the Government Printing Office at the current GPO price. Information on current GPO prices may be obtained by contacting the Superintendent of Documents, U.S.Government Prlnting Office, P.O. Box 37082, Washington, DC 20402-9328, telephone

(202)512-2249.

Issued guides may also be purchased from the National Technical Infor-mation Service on a standing order basis. Details on this service may be obtained by writing NTIS, 5285 Port Royal Road, Sprlngfield, VA 22161.

exceed 24 months. The evaluations shall be conducted taking 'into account, where practical, industry-wide operating-experience." Adjustments must be made where necess-ay to, ensure that, the objective of preventing,failures of .SCs through maintenance is appropriately balanced against the objective of minimizing unavailability of SSCs because of monitoring or p'reventive maintenance.

In performing monitoring and preventive maintenance activities, an assessment of the total plant equipment that is out of service should be taken into account to determine the overall effect on performance of safety functions.

Paragraph (b) of 10 CFR 50.65 states that the scope of the monitoring program specified in paragraph (a) (1)is to include safety-related and nonsafety-related SSCs, as follows: (1) Safety-related structures, systems, or components that are relied upon to remain functional during and following design basis events to ensure the integrity of the reactor coolant pressure boundary, the capability to shut down the reactor and maintain it in a safe shutdown condition, and the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposure comparable to the 10 CFR Part 100 guidelines.

(2) Nonsafety-related structures, systems, or components (i) That are relied upon to mitigate accidents or transients or are used in plant emergency operating procedures (EOPs); or (ii) Whose failure could prevent safety-related structures, systems, and components from fulfilling their safety-related function;

or (iii) Whose failure could cause a reactor scram or actuation of a safety-related system.Paragraph (c) of 10 CFR 50.65 states that the rule provisions are to be implemented by licensees no later than July 10, 1996.The information collections mentioned'

in this regulatory guide are covered by the requirements in 10 CFR Part 50, which were approved by the Office of Management and Budget, approval number 3150-0011.

-

B. DISCUSSION

The objective of 10 CFR 50.65 (referred to hereafter as the maintenance rule or the rule) is to require monitoring of the overall continuing effectiveness of licensee maintenance programs to ensure that: (1) safety-related and certain nonsafety-related SSCs are capable of performing their intended functions and (2) for nonsafety-related equipment, failures will not occur that prevent the fulfillment of safety-related functions, and failures resulting in scrams and unnecessary actuations of safety-related systems are minimized.

The extent of monitoring may vary from system to system depending on the system's importance to risk.Some monitoring at the component level may be necessary;

however, it is envisioned that most of the monitoring could be done at the plant, system, or train level. For example, for less risk-significant systems, indicators of system reliability (where sufficient performance data exist) and availability may be all that is necessary.

For more risk-significant systems, some parameter trending, beyond that already required by NRC requirements to provide early waming of degradation, may also be necessary for critical components whose unavailability causes a system train to be unavailable or whose failure is otherwise unacceptable.

Rather than monitoring the many SSCs that could cause plant scrams, the licensee may choose to establish a performance indicator for unplanned automatic scrams and, where scrams caused by equipment failures have been problematic or where such scrams are anticipated, the licensee may choose to monitor those initiators most likely to cause scrams.It is intended that activities currently being conducted by licensees, such as technical specification surveil ance testig, be used to the naximum extent practical to satisfy monitoring requirements.

Such activities could be integrated with, and provide the basis for, the requisite level of monitoring.

Consistent with the underlying purposes of the rule, maximum flexibility should be offered to licensees in establishing and modifying their monitoring activities.

Licensees are encouraged to consider the use of reliability-based methods for developing the preventive maintenance programs covered under paragraph (a) (2) of the rule; however, the use of such methods is not required.With regard to the scope of the maintenance rule, as stated in paragraph (b) of the rule, it is understood that balance of plant (BOP) SSCs may have been designed and built with normal industrial quality and may not meet the standards in Appendix B to 10 CFR Part 50. It is not the intent to require licensees to generate paperwork to document the basis for the design, fabrication, and construction ofBOP equipment (i.e., backfitting

10 CFR Part 50 Appendix B requirements to BOP equipment is not required).

Each licensee's maintenance efforts should minimize failures in both safety-related and BOP SSCs that affect safe operation of the plant. The effectiveness of maintenance programs should be maintained for the operational life of the facility.160-2-j As noted in the Regulatory Position, there may be a need to address maintenance activities that occur in the switchyards that could directly affect plant operations.

Plant management should be aware of and have the ability to control these activities.

The regulatory guidance is intended to provide flexibility for a licensee to structure its maintenance program in accordance with the safety significance of those SSCs within the scope of the rule.The nuclear industry has developed a document that provides guidance to licensees regarding implementation of the maintenance rule, NUMARC 93-01, "Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants" (May 1993).2 This document has been prepared by NUMARC. A verification and validation (V&V) effort was conducted by NUMARC, with NRC staff observation, to test the guidance document on several representative systems. A number of changes were made to the NUMARC guidance document based on the results of the V&V effort. The NRC staff reviewed this document and found that it provides acceptable guidance to licensees.

Licensees may use methods other than those provided in NUMARC 93-01 to meet the intent of the maintenance rule.However, the NRC will determine acceptability of other methods on a case-by-case basis.Industry and NRC-sponsored probabilistic risk analyses (PRAs) have shown the risk significance of emergency ac power sources. The station blackout rule (10 CFR 50.63) required plant-specific coping analyses to ensure that a plant could withstand a total loss of ac power for a specified duration and to determine appropriate actions to mitigate the effects of a total loss of ac power. During the station blackout reviews, most licensees

(1) made a commitment to implement an emergency diesel generator (EDG)reliability program in accordance with NRC regulatory guidance but reserved the option to later adopt the outcome of Generic Issue B-56 resolution and (2)stated that they had or will implement an equivalent program. Subsequently, utilities docketed commitments to maintain their selected target reliability values (i.e., maintain the emergency diesel generator target reliability of 0.95 or 0.975). Those values could be used as a goal or as a performance criterion for emergency diesel generator reliability under the maintenance rule.Additionally, emergency diesel generator unavailability values were assumed in plant-specific individual plant examination (IPE) analyses.

These 2 Copies are available for inspection or copying for a fee from the NRC Public Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; phone (202) 634-3273;

fax (202) 634-3343.values should be compared to the plant-specific emergency diesel generator unavailability data regularly monitored and reported as industry-wide plant performance information.

These 'values could also be used as the basis for a goal or performance criterion under the maintenance rule.All SSCs within the scope of the maintenance rule, including the emergency diesel generators, are required to be handled under either 10 CFR 50.65 (a) (1) where they are subject to monitoring against licensee-established goals or under 10 CFR 50.65(a)(2)

where they are subject to monitoring against licensee-established performance criteria as described in NUMARC 93-01. Additionally, periodic evaluations under 10 CFR 50.56 (a) (3) that balance reliability and unavailability and assess the impact of removing SSCs from service on overall plant safety must be performed.

Performance criteria for emergency diesel generators (and the support systems vital to their functioning)

would be met by the absence of a repetitive maintenance-preventable functional failure (MPFF), by not exceeding the established reliability or unavailability criterion, or by the occurrence of a single maintenance-preventable failure followed by appropriate cause determination and corrective action. SSCs being handled under 10 CFR 50.65(a)(2)

would be dispositioned to 10 CFR 50.65(a) (1) if the performance criteria are not met or if a repetitive maintenance-preventable functional failure occurs. Once under 10 CFR 50.65(a)(1), the SSCs would be subject to goal setting and monitoring.

All SSCs within the scope of the rule (i.e., those under 10 CFR 50.65(a)(1)

and (a)(2)) are subject to the requirements of 10 CFR 50.65(a)(3), including

(1)periodic evaluation, (2) balancing reliability and unavailability, and (3) assessing the impact on plant safety of taking equipment out of service for maintenance.

C. REGULATORY

POSITION The* scope of monitoring efforts under the maintenance rule, as defined in 10 CFR 50.65(b), encompasses those SSCs that directly and significantly affect plant operations, regardless of what organization actually performs the maintenance activities.

Maintenance activities that occur in the switchyard can directly affect plant operations;

and as a result, electrical distribution equipment out to the first inter-tie with the off-site distribution system (i.e., equipment in the switchyard)

should be included as defined in 10 CFR 50.65(b).NUMARC 93-01 provides methods acceptable to the NRC staff for complying with the provisions of 10 CFR 50.65. NUMARC 93-01 references other documents, but NRC's endorsement of NUMARC 93-01 should not be considered as endorsement of the referenced documents.

1.160-3 I I I I,>r F I

D. IMPLEMENTATION

The purpose of this section is to provide information to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.Except in those cases in which an applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the methods described in this guide will be used in the evaluation of the effectiveness of maintenance activities of licensees who are required to comply with 10 CFR 50.65. The guide will also be used to evaluate the effectiveness of emergency diesel generator maintenance activities associated with compliance with 10 CFR 50.6

3. REGULATORY

AND BACKFIT ANALYSES Separate regulatory and backfit analyses were prepared for this Regulatory Guide 1.160. They are available, in the file for Regulatory Guide 1.160, for inspection or copying for a fee in the Commission's Public Document Room, 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555;phone (202)634-3273;

fax (202)634-3343.

UNITED STATES NUCLEAR REGULATORY

COMMISSION

WASHINGTON, D.C. 20555-0001 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300 FIRST CLASS MAIL POSTAGE AND FEES PAID USNRC PERMIT NO. G-67 120555003954

1 1B51S US NRC-OIRM END USER SUPPT SERVICES CHIEF LIBRARY SERVICES SECTION 2WAGFN-2C8 WASHINGTON

DC 20555 U.S. NUCLEAR REGULATORY

COMMISSION

June 1993 REGULATORY

GUIDE OFFICE OF NUCLEAR REGULATORY

RESEARCH REGULATORY

GUIDE 1.160 (Draft was DG-1020)MONITORING

THE EFFECTIVENESS

OF-, MAINTENANCE

AT NUCLEAR POWER PLANTS

A. INTRODUCTION

The NRC published the maintenance rule on July 10, 1991, as Section 50.65, "Requirements for Monitoring.the Effectiveness of Maintenance at Nu-clear Power Plants," of 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities." The Commission's determination that a maintenance rule was needed arose from the conclusion that proper maintenance is essential to plant safety. As discussed in the regulatory analysis for this rule,'there is a clear link between effective maintenance and safety as it relates to such factors as the number of transients and challenges to safety systems and the associated need for operability, availability, and reli-ability of safety equipment.

In addition, good mainte-nance is also important in providing assurance that failures of other than safety-related structures, sys-tems, and components SSCs) that could initiate or adversely affect a transient or accident are mini-mized. Minimizing challenges to safety systems is con-sistent with the Commission's defense-in-depth phi-losophy. Maintenance is also important to ensure that design assumptions and margins in the original design basis are maintained and are not unacceptably de-'NRC Memorandum to All Commissioners from J. Taylor on'Maintenance Rulemaking," June 27, 1991. Copies are available for inspection or copying for a fee from the NRC Public Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washing-ton, DC 20555; phone (202) 634-3273;

fax (202) 634-334

3. USNRC REGUIATORY

GUIDES Regulatory Guldes are Issued to describe and make available to the pub-lic such Information as methods acceptable to the NRC staff for Imple-menting specific parts of the Commission's regulatlons, techniques used by the staff In evaluating specific problems or postulated acci-dents, and data needed by the NRC staff in Its review of applications for permits and licenses.

Regulatory Guides are not substitutes or regula-tions, and compliance with them is not required.

Methods and solutions different frorn those set out In the guides will be acceptable It they pro-vide a basis for the findings requisite to the Issuance or continuance of a permit or license by the Commission.

This guide was Issued after consideration of comments received from the public. Comments and suggestions for Improvements In these guides are encouraged at all times, and guides will be revised, as ap-propriate, to accommodate comments and to reflect new Information or experience.

graded. Therefore, nuclear power plant maintenance is clearly important in protecting the public health and safety.Paragraph (a)(1) of 10 CFR 50.65 requires that power reactor licensees monitor the performance ol condition of SSCs against licensee-established goals in a manner sufficient to provide reasonable assurance that such SSCs are capable of fulfilling their intended functions.

Such goals are to be established commen-surate with safety and, where practical, take into ac-count industry-wide operating experience.

When the performance or condition of an SSC does not meet established goals, appropriate corrective action must be taken;Paragraph (a)(2) of 10 CFR 50.65 states that monitoring as specified in paragraph (a) (1) is not re-quired where it has been demonstrated that the per-formance or condition of an SSC is being effectively controlled through the performance of appropriate preventive maintenance, such that the SSC remains capable of performing its intended function.Paragraph (a)(3) of 10 CFR 50.65 requires that performance and condition monitoring activities and associated goals and preventive maintenance activities must be evaluated at least annually, 2 taking into 2 As of the publication of this regulatory guide, a modification to the maintenance rule is in preparation that would chano the evaluation interval to every refueling outage but not to ex-ceed 2 years.Written comments may be submitted to the Regulatory Publications Branch, DFIPS, ADM, U.S. Nuclear Regulatory Commission.

Washing-ton, DC 20555.The guides are issued in the following ten broad divisions:

1. Power Reactors 2. Research and Test Reactors 3. Fuels and Materials Facilities

4. Environmental and Siting 5. Materials and Plant Protection

6. Products

7. Transportation

8. Occupational Health 9. Antitrust and Financial Review 10. General Copies of Issued guides may be purchased from the Government Printing Office at the current GPO price. Information on current GPO prices may be obtained by contacting the Superintendent of Documents.

U.S.Government Printing Office, Post Office Box 37082, Washington, DC 20013-7082, telephone

(202)512-2249 or 202)512-2171.

Issued guides may also be purchased from the National Technical Infor-mation Service on a standing order basis. Details on this service may be obtained by writing NTIS, 5285 Port Royal Road, Springfield, VA 22161.

account, where practical, industry-wide operaing ex-perience.

Adjustments'must be made where necessary to ensure that the objective

`f0 preventing'failures of SSCs through maintenance is appropriately

'balanced against the objective of minimizing

'unavailability;

of SSCs'because t:of monitoring or preventive

'mainte-nance. I n performing monitormg and preventive maintenance activities,'

anv assessment'

of the total plant equipment tat is out of service'shoul De taken into account to determine the overall effect on per-formance of safety functions.

Paragraph (b) of 10 CFR 50.65 states th'at`the-scope of the monitoring program specified'

in paragraph (a) (1) is to include safety-related and nonsafety-related SSCs, as follows: (1) Safety-related structures, systems, or compo-nents that are relied upon to remain functional during and following design basis events to en-sure the integrity of the reactor coolant pressure boundary, the capability to shut down the reac-tor and maintain it in a safe shutdown condition, and the capability to prevent or mitigate the con-sequences of accidents that could result in po-tential offsite exposure comparable to the 10 CFR Part 100 guidelines.

(2) Nonsafety-related structures, systems, or components (i) That are relied upon to mitigate accidents or transients or are used in plant emergency operating procedures (EOPs); or (ii) Whose failure could prevent safety-related structures, systems, and components from fulfilling their safety-related function;

or (iii) Whose failure could cause a reactor scram or actuation of a safety-related system.Paragraph (c) of 10 CFR 50.65 states that the rule provisions are to be implemented by licensees no later than July 10, 1996.Any information collection activities mentioned in this regulatory guide are contained as requirements in 10 CFR Part 50, which provides the regulatory ba-sis for this guide. The information collection require-ments in 10 CFR Part 50 have been approved by the Office of Management and Budget, Approval No.3150-0011.

B. DISCUSSION

The objective of 10 CFR 50.65 (referred to here-after as the maintenance rule or the rule) is to require monitoring of the overall continuing effectiveness of licensee maintenance programs to ensure that: (1) safety-related and certain nonsafety-related SSCs are capable of performing their intended functions and (2) for nonsafety-related equipment, failures will not occur that prevent the fulfillment of safety-related functions, and failures resulting in scrams and unnec-essary actuations of safety-related systems are mini-mized.The extent of monitoring may vary from system to system depending on the system's importance to rsk. Some m6nitoring at the component level may be necessary;

however, it is envisioned that most of the monitoring could be done at the plant, system, or train level. For example, for less risk-significant sys-tems, indicators of system reliability (where sufficient performance data exist) and availability may be all that is necessary.

For more risk-significant systems, some parameter trending, beyond that already re-quired by NRC requirements to provide early warning of degradation, may also be necessary for critical components whose unavailability causes a system train to be unavailable or whose failure is otherwise unacceptable.

Rather than monitoring the many SSCs that could cause plant scrams, the licensee may choose to establish a performance indicator for un-planned automatic scrams and, where scrams caused by equipment failures have been problematic or where such scrams are anticipated, the licensee may choose to monitor those initiators most likely to cause scrams.It is intended that activities currently being con-ducted by licensees, such as technical specification surveillance testing, can satisfy monitoring require-ments. Such activities could be integrated with, and provide the basis for, the requisite level of monitor-ing. Consistent with the underlying purposes of the rule, maximum flexibility should be offered to licen-sees in establishing and modifying their monitoring activities.

Licensees are encouraged to consider the use of reliability-based methods for developing the preven-tive maintenance programs covered under paragraph (a) (2) of the rule; however, the use of such methods is not required.'

With regard to the scope of the maintenance rule, as stated in paragraph (b) of the rule, it is -un-derstood that balance of plant (BOP) SSCs may have been designed and built with normal industrial quality and may not meet the standards in Appendix B to 10 CFR Part 50. It is not the intent to require licen-sees to generate paperwork to document the basis for the design, fabrication, and construction of BOP equipment.

Each licensee's maintenance efforts should mini-mize failures in both safety-related and BOP SSCs that affect safe operation of the plant. The effective- ness of maintenance programs should be maintained for the operational life of the facility.As noted in the Regulatory Position, there may be a need to address maintenance activities that occur in the switchyards that could directly affect plant op-erations.

Plant management should be aware of and have the ability to control these activities.

1.160-2 i.' .; -The regulatory guidance is intended to provid flexibility for a licensee to structure its maintenanc program in accordance with the safety significance o those SSCs within the scope of the rule.W_ The nuclear industry has developed a documen that provides guidance to licensees regardin implementation of the maintenance rule. This docu ment has been prepared by NUMARC. A verificatioi and validation (V&V) effort was conducted b'NUMARC, with NRC staff observation, to test th: guidance document on several representative systems A number of changes were made to the NUMAR(guidance document based on the results of the V&\effort. The NRC staff reviewed this document ani found that it provides acceptable guidance ti licensees.

Certain requirements for a renewed license unde 10 CFR Part 54 may be satisfied by taking credit fo activities required by the maintenance rule. However the renewal rule requires (10 CFR 54.21(a)(6)(iii))

-among other provisions, that an effective prograr must be implemented by the facility operating pro cedures and reviewed by the on-site review commit tee. The maintenance rule does not have thes requirements.

Industry and NRC-sponsored probabilistic risl analyses (PRAs) have shown the risk significance c emergency ac power sources. The station blackou rule (10 CFR 50.63) required plant-specific copin analyses to ensure that a plant'could withstand a tota loss of ac power for a specified duration and to deter , mine appropriate actions to mitigate the effects of-total loss of ac power. During the station blackout re views, most licensees

(1) made a commitment to im* plement an emergency diesel generator (EDG) reli ability program in accordance with NRC regulator.- :-'guidance but reserved the option to later adopt th:outcome of Generic Issue B-56 resolution, (2) state that they had or will implement an equivalent prc gram, or (3) endorsed the program embodied i.-'.:,NUMARC

87-00, Revision 1, August 1991, "Guide lines and Technical Bases for NUMARC Initiative Addressing Station Blackout at Light Water Reactors ,(i.e., maintain the emergency diesel generator targe.reliability of 0.95 or 0.975). Subsequently, utilitie..docketed commitments to maintain their selected tai get reliability values. Those values could be used as t-goal or as a performance criterion for emergency di(-sel generator reliability under the maintenance rule..':: When utilities were performing their plani specific coping analyses, they were allowed to us lplant-specific data concerning unavailability due t Lmaintenance.

Therefore, emergency diesel generatc Unavailability due to maintenance, as assumed in l ';Plnt-specific individual plant examination (IPE ianalysis could also be used as the basis for a goal c erformace criterion under the maintenance rule.e Section (a) (3) of the maintenance rule requires e that adjustments be made where necessary to ensure f that the objective of preventing failures of SSCs through maintenance is appropriately balanced against the objective of minimizing unavailability of It SSCs due to monitoring or preventive maintenance.

Therefore, plant-specific emergency diesel generator g reliability and unavailability should be monitored as n goals under 10 CFR 50.65(a)(1)

or established as performance criteria under the plant's preventive eY maintenance program under 10 CFR 0.65(a)(2), e taking into account the objectives of 10 CFR 50-65(a)(3).

Under 10 CFR 50.65(a) (2), the utility would es-d tablish performance criteria for both emergency die-D sel generator reliability and unavailability.

Emergency diesel generator performance criteria for reliability would be met by the absence of a maintenance- r preventable failure or the occurrence of a single r maintenance-preventable failure followed by appro-r, priate root cause determination and corrective action.Performance criteria for unavailability would be met n by having fewer unavailable hours, on a rolling 1-year basis, than required by the established performance criteria.e If any performance criterion is not met, or a second emergency diesel generator maintenance- preventable failure occurs, it is expected that the li-k censee would establish goals and monitor subsequent of emergency diesel generator performance under It 10 CFR 50.65(a)(1), consistent with an appropriate g balance between emergency diesel generator reliabil-dl ity and unavailability.

a The emergency diesel generator reliability per-formance criteria or goals selected for implementing the intent of 10 CFR 50.63 for coping with station blackout could be monitored through the use of the y triggers 3 and the monitoring methods described in e Appendix D of NUMARC 87-00, Revision 1, d "Guidelines and Technical Bases for NUMARC In-)- itiatives Addressing Station Blackout at LWRs," n August 1991 (except for triggers and testing for"problem diesels" as described in paragraph D.2.4.4 ,5 of NUMARC 87-00, which will be addressed sepa-rately by the NRC). An acceptable unavailability goal et could be to have fewer hours unavailable (on a rolling*s 1-year basis) than the number of hours established as acceptable by the licensee.a C. REGULATORY

POSITION The scope of monitoring efforts under the main-L- tenance rule, as defined in 10 CFR 50.65(b), encom-e passes those SSCs that directly and significantly affect Dr 3 The triggers are intended to indicate when emergency diesel generator performance problems exist such that additional a monitoring or corrective action is necessary.

It is recognized that it is not practical to demonstrate by statistical analysis that conformance to the trigger values will ensure the attain-)r ment of high reliability, with a reasonable degree of confi-dence, of individual EDG units.1.160-3---;,-I .iw.......9 plant operations, regardless of what organization actu-ally performs the maintenance activities.

Mainte-nance activities that occur in the switchyard can di-rectly affect plant operations, and as a result electrical distribution equipment out to the first inter-tie with the off-site distribution system (i.e., equipment in the switchyard)

should be considered for comparison with 10 CFR 50.65(b) for inclusion under he scope of the maintenance rule.NUMARC 93-01, dated May 1993, Industry Guideline for Monitoring the Effectiveness of Mainte-nance at Nuclear Power Plants," 4 provides methods acceptable to the NRC staff for complying with the provisions of 10 CFR 50.65. NUMARC 93-01 refer-ences other documents, but NRC's endorsement of NUMARC 93-01 should not be considered as en-dorsement of the referenced documents.

The example in NUMARC 93-01, Sec-tion 12.2.4, which refers to optimizing emergency 4Copies are available for inspection or copying for a fee from the NRC Public Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; phone (202) 634-3273;

fax (202) 634-3343.diesel generator reliability and availability, describes an acceptable method to establish emergency diesel generator performance criteria and/or goals and sub-sequently monitor emergency diesel generator per-formance.

D. IMPLEMENTATION

The purpose of this section is to provide informa-tion to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.Except in those cases in which the applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commis-sion's regulations, the methods described in the guide will be used in the evaluation of submittals for construction permits and operating licenses (as appro-priate) and will be used to evaluate the effectiveness of maintenance activities of licensees who are re-quired to comply with 10 CFR 50.65. The guide will also be used to evaluate the effectiveness of emer-gency diesel generator maintenance activities associ-ated with compliance with 10 CFR 50.63.1.160-4 REGULATORY

AND BACKFIT ANALYSES.Separate regulatory and backfit analyses were prepared for this Regulatory Guide 1.160. They are available, in the file for Regulatory Guide 1.160, for inspection or copying for a fee in the Commission's Public Document Room, 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; phone (202)634-3273;

fax (202)634-3343.

1.160-5