ML20138E478
| ML20138E478 | |
| Person / Time | |
|---|---|
| Issue date: | 10/27/1994 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20136A631 | List: |
| References | |
| FOIA-97-045, FOIA-97-45 2515-126, NUDOCS 9411080107 | |
| Download: ML20138E478 (6) | |
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< o NUCLEAR REGULATORY COMMISSION l f WASHINGTON, D.C. 20555 4001
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l NRC INSPECTION MANUAL TOMB i
TEMPORARY INSTRUCTION 2515/126 1
l EVALUATION OF ON-LINE MAINTENANCE 1
, 1 SALP FUNCTIONAL AREA: MAINTENANCE (MAINT)
J APPLICABILITY: All power reactor facilities 2515/126-01 OBJECTIVE To evaluate the impact on safety of licensee's procedures and practices regarding the removal of equipment from service for on-line scheduled maintenance. l 2515/126-02 BACKGROUND During recent plant visits by several NRC senior managers, it was noted that licensees are increasing both the amount and frequency of maintenanc.e performed during power operation. Most of the licensees visited stated th6t they were l implementing or soon would implement the concept of outage windows while the plant was operating at power. Some licensees were limiting the planned outage window to a single train of a satem while others would allow multiple equipment in other systems within a single train to be out of service as long as it did not violate Technical Specifications. For example, at one plant it was noted that over a three-day period the liccisee had diverse components in a single train out of service for planned maintenance. During this period, work was performed on two battery chargers, an auxiliary feedwater pump, a residual water system heat exchanger, a safety injection pump, a safety-reiated chilled water system, and a station service water pump. Multiple components were planned to be simulta-neously out of service for testing or maintenance. Although most equipment could have been returned to an operable status, it is not clear that the licensee, prior to their removal, adequately evaluated the safety significance of having multiple components out of service for a period of time.
Licensees' expansion of the on-line maintenance concept without thoroughly considering the safety (risk) aspects raises significant concerns. The on-line maintenance concept appears to extend the use of Allowed Outage Times (A0T) stated in the Technical Specifications beyond the random single failure in a system and a judgement of a reasonable time to effect repairs upon which the A0Ts were based. The capability to withstand a single failure in fluid and electrical systems is a plant specific design requirement that is contained in the general i
design criteria in 10 CFR 50. Appendix A. Compliance with this criteria is demonstrated during plant licensing by assuming a worst case single failure which often results in multiple equipment failures. This does not imply that it is acceptable to voluntarily remove equipment from service to perform on-line Issue Date: 10/27/94 2515/126
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maintenance on the assumption that such actions are bounded by a worst case single failure.
A simplified qualitative model for evaluating risk can be thought of as including three factors combined in the following way.
Risk - P, x P, x Pc l Where:
! P, = The probability of an initiating event, such as a LOCA. turbine trip, or l loss of offsite power.
l l P, - The probability of being able to mitigate the event using core damage prevention as a measure of successful mitigation.
P, = The probability of being able to mitigate the consequences using l
containment integrity preservation as a measure of success.
An effective risk assessment process includes consideration of the im]act of maintenance activities on all three of these risk factors. It also consicers the impact of maintenance activities on both safety-related and non safety-related equipment. Multiple or single maintenance activities that simultaneously, or within a short time frame, impact two or more risk factors tend to increase risk the greatest.
l In addition, on-line scheduled maintenance tends to increase component unavailabilities. With increased on-line scheduled maintenance, the overall impact on train unavailability when averaged over a year has in many cases increased dramatically and in some cases to the point of invalidating the assumptions licensees themselves made in their plant specific Individual Plant Examinations-(IPE).
NRC Inspection Manual Part 9900 Technical Guidance, " Maintenance - Voluntary Entry Into Limiting Conditions For Operation Action Statements to Perform Maintenance." issued in 1991, provided some general safety principles that inspectors were to use in order to ensure that licensees did not abuse the lack of specificity in TSs regarding the proper use of A0Ts. The guidance recognized that at the time the NRC was only beginning to quantitatively study the significance to safety (risk) of the trend to perform more scheduled maintenance at power, and in general, licensees had not yet fully developed the capability to perform such studies. Therefore, the guidance did not establish quantitative criteria by which the NRC or a licensee could determine the net effect on safety that on-line scheduled maintenance would have at the facility, or for the industry as a whole.
Tools to quantitatively asses the relative risks of various maintenance and j outage schedules are now available to licensees as discussed below. Additional- I ly, Regulatory Guide 1.160, issued to support implementation of the Maintenance l Rule (10 CFR 50.65) in 1996, provides some valuable insights. The maintenance l rule requires licensees both to balance the improvement in reliability resulting I from maintenance with the increase in equipment unavailability due to the planned maintenance and to evaluate the impact upon safety of all equipment currently out of service before voluntarily taking additional equipment out of service.
This Temporary Instruction (TI) is intended to provide guidance to inspectors to l
enable them to determine whether licensee processes appropriately consider the significance of on-line maintenance and identify specific instances where planned
! 2515/126 Issue Date: 10/27/94
maintenance will potentially. result in an impact on plant safety (risk).
Inspectors are cautioned not to attempt to enforce the requirements of the maintenance rule when implementing this TI. but rather are requested to raise concerns to regional managers and the TI 2515/126 review committee that is in the process of being established.
2515/126-03 INSPECTION REQUIREMENTS 03.01 Maintenance Plannino and Schedulino. Determine whether licensees have in place a program that focuses on all three of the risk factors discussed above and thoroughly evaluates the impact of scheduling on-line maintenance with regard to plant safety.
- a. Review the process and procedures that the licensee has in place to schedule on-line maintenance.
- b. Determine whether the licensee evaluates the risk incurred from performing on-line maintenance activities by assessing the cumulative effect of multiple equipment maintenance activities and equipment outages, prior to performing the maintenance or taking equipment out of service.
- c. Determine how the process integrates scheduled maintenance activities with existing degraded / inoperable equipment.
- d. Determine the extent of knowledge and awareness of supervisory and working level personnel concerning the licensee's process for planning and scheduling operations and maintenance activities. (The necessary level of knowledge of the comprehensive process should be dependent upon the extent to which the individuals are responsible for the details of specific and over all planning and scheduling).
03.02 Planned Maintenance. Review the on-line scheduled maintenance for the upcoming cycle (should look at a time period between one month and one quarter of planned activity) to identi fy any specific instances (situations or configurations) where planned on-line maintenance could potentially have a significant impact on plant risk. As stated in the background section multiple or single maintenance activities that simultaneously, or within a short time frame, impact two or more risk factors tend to increase risk the greatest.
03.03 Reoortina. Consult with and identify any concerns to regional management for coordination with the NRR TI 2515/126 review committee.
2515/126-04 GUIDANCE 04.01 Maintenance Plannina and Schedulina. The process established by the licensee to evaluate what planned maintenance should be conducted on-line should consider the cumulative impact of the maintenance activities on overall plant safety.
- a. In reviewing the process. the inspector must concentrate on the effectiveness of the maintenance program and on the procedures used for planning and scheduling maintenance activities, specifically looking for the incorporation of risk insights derived from consideration of all three of the risk factors discussed in the background section above. (Some plants have computer based models, while others use simple equipment Issue Date: 10/27/94 2515/126 ,
matrices which restrict having risk-significant combinations of equipment inoperable simultaneously.)
- b. Licensees may not have thoroughly considered the safety (risk) aspects of doing more on-line maintenance. Some licensees are using the concept of division or trnn outages to ensure that they do not have a loss of system function. In the extreme. this could result in all of the equipment in a division being out of service at the same time with unexamined risk consequences, while being in literal compliance with plant TS. For example, one facility that used a division or train approach to on-line maintenance had planned to take out of service the following equipment:
4 B Auxiliary Feedwater. B Battery Charger. B Service Water. B RHR. and the B Charging Pump. Because redundant train equipment was available, there was no violation of TS. However, in the event of a design--basis transient such as a loss of offsite power precipitated by maintenance or instrumentation calibration activities associated with nonsafety-related equipment in the switchyard, the plant would be in a configuration with significant risk implications due to a diminished capability to remove decay heat at hig 1 pressure. This is an example of maintenance simultaneously increasing the probability of an initiating event, in this case a loss of offsite power. and diminishing the plant's capability to mitigate the event.
The confidence in the operabilit." of redundant / diverse equi) ment should be high during periods of on-line scheduled maintenance. Ivaluate the licensee's conduct of operations during on-line maintenance activities.
The licensee should avoid performing other testing or maintenance that would increase the likelihood of a transient (a potential event initiation). This consideration should include degraded or out-of-service equipment in the balance of plant. ,
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- c. The process used by the licensee to schedule and plan on-line maintenance should ensure that maintenance and testing schedules are appropriately .
modified to account for degraded or inoperable equipment. When reviewing l the process, determine how it accomplishes this function.
- d. Determine the extent to which the process used by the licensee is used by the operations and maintenance staffs. The following are examples of questions that should help determine the operations / maintenance level of familiarity with the process employed in managing scheduled maintenance activities. When planning on-line maintenance:
- Does the licensee take probabilistic risk insights into account?
e Does the licensee allow multiple train outages?
e How does the licensee take into account component and system dependencies?
e How does the licensee assure that important combinations of equipment needed for accident mitigation are not unavailable at the same time?
i e By what process does the licensee determine how and what procedures and testing to focus on in minimizing unavailability and reducing the potential for accident or transient initiation including the impact of maintenance activities involving nonsafety equipment (e.g.,
turbine generator and electrical equipment)?
2515/126 Issue Date: 10/27/94
i o How does the licensee determine the maximum amount of time to allow for the maintenance and how does it determine the risk associated ,
with the decision? !
e At any given time, how much planned maintenance is in progress and how is it coordinated to minimize risk?
04.02 Planned Maintenance. In reviewing the licensees planned maintenance look for occurrences of scheduled maintenance activities that simultaneously, or within a short time frame, impact two or mare of the risk factors discussed in the Background section, above. The following example is provided:
Example: Maintenance is scheduled to be performed at a PWR. The equipment (the A EDG and the A motor driven auxiliary feedwater pump) will be out of service during the maintenance.
Before undertaking the above maintenance, the licensee's planning and scheduling should consider the potential effects on plant safety of any j concurrent maintenance, surveillance or testing on, as well as unavailability '
of:
- 1. Obvious risk contributing systems and components such as offsite power.
l the normal power to other Train A components, the Train B EDG. the Train B motor driven auxiliary feedwater pump, and the turbine driven auxiliary feedwater pump.
- 2. Less obvious potential risk contributors could also exist. Considering just the unavailability of the EDG, the steam driven aux feed pump and the l station batteries could be significant (i f for instance a grid i perturbation caused a loss of offsite power and concurrent RX trip and failure of the B EDG to start). In the case of the unavailable auxiliary feedwater pump, maintenance on secondary components such as the main feedwater and condensate pumps might be significant given that their loss could cause a Reactor trip and the need for auxiliary feed.
04.03 Reoortina. Inspector's concerns with any specific upcoming on-line scheduled maintenance should be given priority over completed maintenance.
2515/126-05 REPORTING REQUIREMENTS The inspector should reference TI 2515/126 and briefly document the results of the completion of this TI in a routine inspection report. In addition, the inspector should transmit, through appropriate regional office management. those concerns identified to the Chief. Quality Assurance and Maintenance Branch. NRR.
0WFN 10-A-19.
2515/126-06 COMPLETION SCHEDULE This inspection should be completed by December 31. 1994.
2515/126-07 EXPIRATION This Temporary Instruction will expire on June 30. 1995.
Issue Date: 10/27/94 2515/126
L 2515/126-08 CONTACT Direct questions regarding implementation of this TI to R. Correia. Quality Assurance & Maintenance Branch, at (301) 504-1009.
2515/126-09 STATISTICAL DATA REPORTING Report the direct inspection effort expended for this TI against 2515/126 and under inspection program element (IPE) code of "SI" (Safety Issue Program).
2515/126-10 ORIGINATING ORGANIZATION INFORMATION 10.01 Orqanizational Resoonsibility. The Quality Assurance and Maintenance Branch (TOMB) originated this temporary instruction.
10.02 Resource Estimate. It is estimated that approximately 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> of direct inspection effort will be necessary to complete this TI. Actual inspection at a specific plant may require more or less time depending on plant specific issues.
10.03 Other. Portions of Inspection Procedure 62703, " Maintenance Observa-tions," may be satisfied by the performance of this TI.
10.04 Trainino. No special training requirements are associated with this TI.
2515/126-12 REFERENCES NRC Inspection Manual Part 9900: Technical Guidance " Maintenance - Voluntary Entry Into Limiting Conditions for Operation Action Statements to Perform Preventive Maintenance" 10 CFR 50.65 Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants. (Maintenance Rule)
Regulatory Guide 1.160. " Monitoring the Effectiveness of Maintenance at Nuclear Power Plants" i END 2515/126 Issue Date: 10/27/94
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.'..... July 14, 199s j Mr. Thomas Tipton
- Nuclear [nergy Institute
! 1716 [ye Street W, Suite 300 i Washington, DC 20004 3104 J
Dear Mr. Tipton:
l 1 The purpose of this letter in to provide you with the results and conclusions
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from the evaluation of Inspettlon findings using Temporary Instruction 4 (ii) 251$/126, *1 valuation of On line Maintenance.' the it was issued j October 21, 1994, and the i pections were completed by the specified date of 4 Dec ember 31, 1994 A review committee was established to consolidate and
- review the il inspection results and tvaluate the industry's policles and l controit concernin9 current on line maintenance practices. The results of th"
- committee's Inillal review were documented in a letter to you dated february 24, 1995. Subsequent review of the il inspection results did not provide any significant thangen to these init ial conc lusions.
1 Although this evalgation of licenseen' tsn line maintenant e at livlt les revealcil
! several weaknessel (e.g., lack of coeprehensive risk assessment s, procedural controit, and training), we recogntye that licensees
- on.llne maintenanc e 1 practices and progrees are changt and will continue to evolve as they
! laptement the saintenance rule. Staf f han completed nine pilot site j vltitt to evolwate laplementation activillet in accordante with the malt.tenem e rule. The pilot lite visitt included an evaluat ion of lic ensecs'
! plans for meeting the requirements of the saintenance rule including requisite i safety assesteents for egulpeent out of service for preventive maintenance, j In general, these anlesteents indicated that licensees are in verlous stages j of laplementation, and that the leptementation activit ies are progressing.
4 i We further reccanlye that both the Institute of Nuclear power Operat lons i (INPO) and NiI are aware of our comernt with on line maintenante and are
- actively developing 9widame for licenseen for the development and i leptementation of evitable progrant and controll, INPO lisved a letter on j february if, 1996, to ese'er willittet that provided guidante for managiny l
maintensMe during power operations. The staff han held pulillt **et'.ngs with i
N(I representativen to discutt revillong to the maintenance rule guidelines, j IRMARC 93 01, ' Industry Guideline for Monitoring the lif et tiveness of MaintenaMe at Nwclear power plants,' to incorporate insights from the II
- relvlts and the maintenance rule pilot site visitt. We entourage lHP0 and fd I
! to continue providing gvidence to the lodustry on the development and j laplementation of effect.ve progrees to control on line salnlananic and assoc iated ac t ivit ies at U% power reat tors .
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dtgG 2 T. Tipton July 14, 1995 In conclusion, it appears that the industry is aware of and reacting to NRC concerns with on-line maintenance practices, but continued inspection by the regional offices will be necessary to monitor and assess licensees' on-line maintenance activities to ensure overall plant safety.
Sincerely, Ashok Thadani, Associate Director for Technical Assessment Office of Nuclear Reactor Regulation cc: William Kindley Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, Georgia 30339-5957 DISTRIBUTION: TQMB R/F ADR R/F CENTRAL FILES /PDR SEE PREVIOUS CONCURERNCE DOCUMENT NAME: g:\ draft \tiletter.nei To receive a copy of this document, indicate in the boa: *C* = Copy without enclosures *E" = Copy with enclosures "N" = No copy 0FFICE TQMB/ DOTS l TQMS/ DOTS l TQMB/ DOTS l DOTS /NRR l D/DSSA l NAME RFrahm RCoreria SBlack LSpessard GHolahan DATE 6/23/95* 6/23/95* 6/23/95* 6/27/95* 7/6/95*
OFFICE 0: DISP l AD/ADPR l APT /NRR l DD/NRR l D/NRR l NAME FGillespie RZimmerman AThadani FMirgalia WRussell DATE N/A N/A 7/10/95* 7/11/95* 7/11/95 0FFICIAL RECORD COPY I
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T. Tipton In conclusion, it appears that the industry is aware of and reacting to NRC l concerns with on-line maintenance practices, but continued inspection by the regional offices will be necessary to monitor and assess licensees' on-line .
maintenance activities to ensure overall plant safety. !
Sincerely,
/ ,
, r, n .A u]f Asho Thadani, Associate Director for Technical Assessment Office of Nuclear Reactor Regulation ;
cc: William Kindley Institute of Nuclear Power Operations '
700 Galleria Parkway Atlanta, Georgia 30339-5957 a
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