ML20246P086
| ML20246P086 | |
| Person / Time | |
|---|---|
| Issue date: | 02/06/1989 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| References | |
| TASK-PII, TASK-SE SECY-89-044, SECY-89-044-01, SECY-89-44, SECY-89-44-1, NUDOCS 8905220078 | |
| Download: ML20246P086 (27) | |
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POLICY ISSUE February 6, 1989 (InfOrmatiOn)
SECY-89-044 For:
The Commissioners 1
From:
Victor Stello, Jr.
Executive Director for Operations Sub,iect:
REPORT ON MAINTENANCE PERFORMANCE INDICATOR DEVELOPMENT
Purpose:
To inform the Commission of additional results in the development of maintenance performance indicators.
Background:
On October 14, 1988, the staff briefed the Commission on the Proposed Rule on the Maintenance of Nuclear Power Plants, 10 CFR 50.65. That briefing included a discussion of the efforts to develop maintenance performance indica-tors.
SECY 88-289, October 7, 1988, provided a draft AEOD report'on that development (Preliminary Results of the Trial Program on Maintenance Performance Indicators, AEOD/S804A, which was issued as final in December 1988).
During the briefing, the staff committed to report further regarding the use of the Nuclear Plant Reliability Data System (NPRDS) to develop maintenance performance indica-tors. The development activities are proceeding on a schedule to support the draft maintenance Regulatory Guide.
A second report, AE0D/S804B, which provides a valid method to obtain an indicator for maintenance effectiveness, is attached.
Discussion:
In the final report (AE0D/S804A), the staff concluded that maintenance performance indicators which are based upon actual component reliability and failure history could provide a useful measure of maintenance effectiveness.
Subsequent to visits to thirteen plant sites, the staff concluded that the best existing source for such component reliability data, plant-specific or industry-wide, was the component level failure reports that were submitted by each plant to the Nuclear Plant Reliability Data System (NPRDS).
With the goal of providing the NRC staff and licensees with a practical near-tenn method to track maintenance effec-tiveness, the' staff recommended that licensees be strongly e
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encouraged to use the component failure reports submitted to the NPRDS as a basic element of the maintenance effec-tiveness monitoring activity that is to be required by the l
rul e.
The proposed rule package was modified to be consistent with the staff's recommendation.
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Since the issuance of SECY 88-289, AE0D has continued to I
pursue the development of candidate maintenance effec-tiveness indicators. The enclosed report, AE0D/S8048, documents the development and validation of one example
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l indicator and demonstrates the use of NPRDS data for monitoring maintenance effectiveness. While the focus of this report is on the use of NPRDS to monitor mainte-nance effectiveness, a mutually reinforcing correlation i
between the NPRDS-based indicator and LER maintenance cause code data points to the prospect of an additional maintenance indicator.
Further development of the maintenance cause codes from LERs is also being pursued for use in monitoring maintenance effectiveness.
Limitations:
Although there are inherent limitations in the present capability of the,NPRDS for monitoring mair+enance effectiveness, the failure data routinely reported._to this srys. tem continues to be the most' efficient and product'ive mechanism for maintenance performance indicators for staff, industry-wide, and plant-specific near-term use.
Attach-I ment 1 to the enclosed report is the staff's annual evalu-ation of the NPRDS. The NPRDS does not currently capture component failures in some of the important systems that continue to cause plant safety system challenges, such as the turbine control system.
However, the indicator that was validated, based upon BWR component failures, was effective despite these limitations.
INP0 has recently begun a study to support expansion of the NPRDS scope to cover more 80P systems. Other changes to that system are discussed in the staff's evaluation.
Current Initiatives:
The staff is currently developing simplified methods to acquire and display the example indicator. The display of this indicator currently demands extensive computer down-load time and interactive computer manipulation.
As previously 4
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,y noted, the staff is-also proceeding with further: develop-ment of maintenance. performance. indicators in support of-the maintenance Regulatory Guide and the'overall staff program to assess maintenance effectiveness.
C D, D ctor StiL+10, Jr Executive' Director for Operations Attachments AE00/S8048--
' Application of the NPRDS For Maintenance Effectiveness Monitoring a
DISTRIBUTION:
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OIA GPA REGIONAL OFFICES EDO ACRS ACNW ASLBP ASLAP SECY m i
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l AEOD/S8048 APPLICATION OF THE NPRDS FOR MAINTENANCE EFFECTIVENESS MONITORING o#'%
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Prepored by: P. D. O'Reilly, T. R. Wolf P. Cross-Prother Division of Safety Programs Office for Analysis and Evoluotion of Operational Dato U.S. Nuclear Regulatory Commission NOTE:
Appendixes A and B to this report contcin plant-specific data from the Nuclear Reliability Data System (NPRDS). Therefore, they must be treated as containing PROPRIETARY commercloi nuclear power plant Information.
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SUMMARY
On November 28,1988, the Commission issued a proposed rule on " Ensuring the Effectiveness of Molntenance Programs for Nuclear Power Plants, 10 CFR 50.65.
The proposed rule would require licensees to formaltze their molntanonce pro-grams in accordance with the definition in the rule, and to monitor the effective-ness of their programs. Specifically, the rule would require licensees to:
... regularly assess the effectiveness of this maintenance pro-gram, and based upon this assessment, make Improvements as appropriate.
Operating chorocteristics such as consistently high availability, or low equip-ment caused forced outage rates over severot operating cycles are indicators of good maintenance effectiveness. However, plant material condition con degrade significantly before these Indicators provide identification of degoded maintenance performance. A more timely indicotlon of the effectiveness of maintenance is needed.
To support the mon:toring provision of the proposed rule,the NRC's Office for Analysis and Evoluotion of Operational Data (AEOD) conducted maintenance performance indicator developmental activities and documented their results in AEOD/S804A Prellmlnary Results of the TrialProgram on Maintenance Perform-ance indicators, which was transmitted to the Commission by SECY 88-289 on October 7,1988. That report concluded that indicators which are based upon actual component reliability and failure history provide the best measure of maintenance effectiveness. It recommend 3d that:
Ucensees should be strongly encouraged to utilize an Industry-wide component failure reporting system, e.g., NPRDS, as a basic
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element of the maintenance effectiveness monitoring actMty that is to be required by the rule.
This report, AEOD/S8048 demonstrates the utility of the Nuclear Plant Rellobility Doio System (NPRDS) to provide useful molntenance effectiveness monitoring information. It documents the development of on indicator that is based upon the component failure reports submitted to the NPRDS, and demonstrates that the monitored indicator reflects molntenance effectiveness.
Demonstrating the validity of the condidate indicator required that the Indicator be based on a reasonably complete, consistent set of NPRDS dato, in order to AEOD/S804B 2
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t ensure that the data would sottsfy these criterio, this study considered only major.
components in systems which have historically been significant contributors to forced outages. Follures of this equipment were considered most likely to be reported to the NPRDS regardless of a plant's NPRDS reporting consistency or the aggressiveness of its operoflons personnel in detecting failures. Using this dato, on Indicator of maintenance effectiveness was then constructed that monitors increases in the failure rates within a system, and provides a signol when on increase exceeds a specified value. This yields a measure of the changes in the I
. effectiveness of molntenance on a system basis. To obtain a measure of a plant's level of maintenance effectiveness, the number of Indications or signals is tollied across a number of systems. This tolly is but one indicotton of the effec-tiveness of a plant's molntenance program. Other items, such as additional Indicators, systems analyses, and Inspections, are needed to obtain a complete picture of the obsolute level of the effectiveness of molntenance at any plant.
The vo!ldation as to whether the condidate indicator reflected molntenance ef-festiveness was based upon deterministic engineering analyses and empirical methods. Engineering l
studies of NPRDS failure
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records for such components I
. FA! LURE RATE CHANGElNDICATOR ences in molntenance
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practices among the plants caused differences In failure rates. Further, root cause
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cnolyses of the failures com-prising the Indicator revealed maintenance effectiveness os the major cause. Figure A
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, a a== = s Illustrates this port of the n== om"wrom validation process. Finally, sougs ysgegses empirically,it was shown that tne Indicator correlates reasonably wellwith other in-formation regarding molnte-j[g[
nonce problems derived from Licensee Event Reports n.,
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The usefulness of the condi-1
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date indicotor,and any ofherindicator developed based upon the component follure reports submitted to Figure A AEOD/S8048
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the NPRDS, telles to a large degree on the quality and completeness of NPRDS reporting by licensees. Since such reporting ls voluntory and subject to Individual utility priorities and commitments, some limitations are inherent in the utilization of NPRDS fcIlure reports for molntenance effectiveness trending.
This report documents that a practical and useful maintenance performance in-dicator was developed using NPRDS dato. The ability of the condldate indicator to reflect maintenance effectiveness was confirmed. The effect of non-uniforrn NPRDS reporting was shown to be acceptobly minimized through the use of a standard subset of equipment that is important to plant operoflons.
The value of the condidate indicator was confirmed through independent dato derived from molntenance-coused events r.eported in ERs, correlations with other studies, and correlations with the findings from molntenance effectiveness team inspections. While the focus of this report is on the use of NPRDS to monitor molntenance effectiveness, the mutually reinforcing correlation between ER-based dato and the NPRDS-based indicator points to the prospect of on addi-tional maintenance Indicator. The ER-based dato used in this correlation resulted from the ongoing performance indicator development effort cimed to demonstrate the usefulness of cause codes, one of which is maintenance.
Further development of this molntenance cause code from ERs is being pur-sued for use in monitoring maintenance effectiveness.
Although the methodology used in this study was developed using data for 26 i
BWRs,it should prove equally volld for other plant designs. Other volld indicators may be developed from this dato but the condidate indicator developed in this study serves os a suitable basis for describing a maintenance effectiveness tracking method which is acceptoble to the staff in the forthcoming Mainte-nonce Rule regulatory guide.
In order for the NRC staff to use the condidate indicator on on industry-wide cost-effective basis, further development is necessary to more efficiently extract the indicator from the NPRDS system and to display it in a manner which permits individual as well as generic comparisons. The staff continues to give further development efforts high priority and will shore the results of its activities with industry.
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APPLICATION OF THE NPRDS FOR MAINTENANCE EFFECTIVENESS MONITORING INTRODUCTION The Office for Analysis and Evoluotion of Operational Doto (AEOD) recently issued AEOD/S804A, " Preliminary Results of the Trial Progrdm on Molntenance Performance Indicators" (Rsf.1). A number of condidate maintenance per-formance indicators were onelyzed, including process indicators such as correc-tive molntenance backlog, and equipment performance-based indicators such qs. rework and frequency of failure. A major conclQsion of this study was:
Indicators that are based upon actual component reliability and failure historyprovide the best measure of maintenance effectiveness....
At the most fundamental level, this translates into tracking component perform-once through the construction of component failure histories. Tracking equip-ment performance is also generally accepted as a way of improving molnte-nonce. AEOD/S804A noted, however, that licensees generally were not using such dato to assess molntenance effectiveness. Independently, os shown in the following findings, recent NRC. maintenance inspections also found this to be the cose:
Improvements in problem resolution remain to be demonstrated, in view of prior and recent missed opportunities to recognize and correct the root causes of plant problems. The obsence of etfec-tive eau loment performance trendina ornarams cocears to have contributed to such overslahts. (Ref. 2, emphasis added)
Work history and performance history are not Integrated and repetitive failures of work on similar components cannot be AEOD/S804B 5
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a readilyidentitled. Therefore, root cause analysis andprompt identification and correction of ptoblems(are) not as effective as (they) could be. (Ref. 3)
Trending of equipment failures - the Inspection team observed examples of failures to adequately assess and trend equipment failure data..,. In addition to the lack of an adequate trending activity, this weakness in providing feedback to the PM (i.e.,
preventive maintenance) program aiso stems trom lncomplete maintenance and equipment history records. (Ref. 4)
AEOD/S804A also noted that most plants have o molntenance work request tracking system but that such systems do not lend themselves to the ready identi-fication and tracking of individual component fcilures. Consequently,it was concluded that the Nuclear Plant Rellobility Data System (NPRDS) (Ref. 5) was the best avollable source for component failure data. This conclusion was independently observed during one of the previously cited inspections (Ref. 3).
The inspection report noted that:
Repetitive failures of work on simHar components cannot be readily identitled by using CHAMPS (l.e.. the planYs molntenance tracking system)... NPRDS Is generally used. when requested, for failure determination.
Since the NPRDS is such a valuable resource,it must continue to molntain a high quality of component failure dato. To confirm that the NPRDS remains a viable source for component fallure dato,the NRC periodically cssesses its quality, The most recent annual appraisol is provided as on ottochment to this report.
Building on the findings of AEOD/S804A and the recent molntenonce inspec-tions, work continues on the development of molntenance performance Indico-tors based on NPRDS dato. This report describes the results of this work by provid-ing a detailed example of how NPRDS failure histories for selected equipment, colled outoge dominating equipment (ODE), con be combined into on indico-for of maintenance effectiveness. While the indicator was developed and validated based upon NPRDS data for a single reactor type, i.e., General Electric (GE) bolling water reactors (BWRs), the principles and approaches used are con-sidered equally applicable to reactors of other designs.
The next section discusses the construction and use of the condidate indicator.
Subsequent sections provide details about the process used to validate this indicator and on examination of its use os a timely indicator of equipment forced outages.
AEOD/S8048 6 9
INDICATOR DEFINITION AND CONSTRUCTION The Indicator constructed in this study scans the NPRDS component failure rate data within a system and signals any increase in that rote which exceeds a pre-determined threshold value. The number of these flogged failure rate increases is then follied for all systems considered over o specified span of time to obtain a PLANT A Component Failure Trends measure of thelevel of molntenance ef-l gg g
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festiveness at a i 4 4,..... '.
- plant. Figure 1 is on example for one l
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nent failure rate in-r-, w.
creases that were l
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flogged for five
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of 22 fallure rate increases were sig-noled during opproxi-I,.,.,.,III.,.,.,,..,.,.,.,.,.
motely a three-year time span. The foilowing sections discuss in detail the Rgure 1 definition of the indicator,the methods and reasons for the selection of the equipment and follure dato used, and the construction of the indicator from that dato.
INDICATOR DEFINITION Of the number of porometers which could be monitored os on indicator of maintenance effectiveness, the rote of reported component failures (i.e -, failures per month) was considered to be the most definitive measure of equipment per-formance and the one that could be directly linked to the effectiveness of the molntenance performed on that equipment. However,this porometer is suscep-tible to plant-to-plant inconsistencies in failure reporting. Control of such incon-sistencies, os well as dato completeness, con be exercised by measuring a plant i
against itself. This con be done by mor'ioring either the deviations from on AEOD/S804B 7
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overage failure rote or o ch ange in the failure rate. This study focused on the change in the failure rote as the indicotor of molntenance effectiveness.
An increase in the rcte of component follures is Indicative of a change in the -
effectiveness of maintenance. Such a change in failure rate lends itself well to
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trending and, consequently, moy be used as o trend indicator. This may be j
4 accomplished by tollying the number of increases in the' component failue rote over o given time span for a number of different systems. This folly by itself is but one indicotlon of the effectiveness of a plant's molntenance program. Other items, such as additional indicators, systems onclyses, and inspections, are needed to obtain a complete picture of the obsolute level of the effectiveness of molntenance at any plant.
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It should be pointed out that the methodology used to obtain the Indicator grouped the failure dato according to particular components in selected systems. During the course of the developmental analyses,it was found that opplying the indicator at a higher level, e.g., all components together, diluted its sensitivity and resulted in relatively fewer indications than were obtained when the onolysis was performed on on individual system basis. Another insight that stemmed from these anotyses was that the data must be analyzed on at least a monthly bosts. Viewing the failure dato on a quarterly basis resulted in a loss of.
the fine detail and sometimes a dampening out of pronounced In. creases in component failure rate that were exhibited when a monthly basisswas used.
INDICATOR CONSTRUCTI,0N In the construction of the condidate Indicator, o comparative formula was developed to detect the rate of change in the failure rates of the components within a system. It was then computerized so that it would signal o component failure rate change that exceeded a predetermined value. Once the formuto was computerized, it was adjusted to be sensitive to changes in the component failure rate that oppeared significant based on trends observed in the historical dato from 10 BWRs.
The resultant computerized Indicator formulo counts the number of component failures discovered during ecch month in a five-month span of time for each of the selected systems. Dividing the number of component failures for each of the systems in a selected time period by the number of months h the period, it then calculates the overage component failure rote for each system for (c) the first three months of the five-month time span and (b) the failure rote for the lost two l
months of the spon. It then compares the two oveFoge rates and,if the rate in the lost two months exceeds that of the first three months by more than a threshold value, on indicoting mark is placed in the lost month of the five-month AEOD/S804B 8
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d span The program then FAILURE RATE CHANGE INDICATOR cdds the next more recent
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month and drops the oldest month,i.e., the five-month j
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span is shifted forward one month, and the failure rate
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calculations and comportson
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window approach has the effect of providing multiple
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Indicating marks over successivemonthsif an s'^""""^"^'""^'T^"""*"
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increase in failure rate is large orif it is sustained over a number of months. Thus, the indicator weights periods Figure 2 of time in proportion to the degree of change in the component failure rate. Figure 2 shows how on increasing falture rate trend is signaled by this method.
DATA CONSISTENCY AND COMPLETENESS The dato used in the construction and validation of the condidate NPRDS-based indicator had to satisfy two criterlo:
(1)
A consistent set of NPRDS data had to be obtained for each plant, and (2)
The individual plant data sets had to be reasonably complete.
Major differences in the level of NPRDS reporting from unit to unit have been observed. To accommodate the shortcomings of incomplete NPRDS reporting, a logic was applied to utilize o subgroup of the equipment failures In the NPRDS.
Two factors dletoted the group of equipment selected. First, during the site visits of the trial program documented in AEOD/S804A,it was noted that the operot-Ing crew played a major role in molntenance work request (MWR) generation during plant operoflon. The NPRDS failure reports are dependent upon MWR generation and are therefore sensitive to the aggressiveness of the operating crew in the complete and timely identificotlon of equipment problems. To minimize the effects that could be attributed to vorlations among plants, the dato analyzed was limited to follures of mojor components in systems that sup-port power operoflon. In cases where o plant was shut down, if it were to stort up without having repaired the failed equipment, the plant would be operating
- with a degraded system that could eventually have on adverse impact on l
AEOD/S8048 9 L.__________.._____
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power operotlon. Follures of this equipment are much more likely to be Identle fled for repolt in a timely manner, thereby minimizing the potentlol impact of the vorlations in the identificotlon of fcitures.
The second factor that was used to assure reasonable completeness of the dato set was information obtained from the NPRDS coordinators. Generally, the NPRDS coordinators are the individuals that produce the NPRDS reports based 4
upon the molntenance work request input. During the trial piogram reactor site.
visits, it was found that, although the obsolute reporting rate may vary widely J
from unit to unit, the NPRDS coordinators generally report the important failures.
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j Important failures,in their view, were those that could influence plant operation to such a degree that a plant outage could occur at their plant or another plant.
Considering these two factors, the condidate molntenance indicator was based on NPRDS-reported failures from the set of equipment that historically has caused equipment forced outages. Th!s dato set represented reasonably complete component failure Information for o reasonable scope of equipment.
Vorlations from plant to plant due to different NPRDS reporting philosophies were further lessened by using only those types of component failures that the NPRDS Report /ng Procedures Manual (Ref. 6) requires to be reported (i.e., immediate,
ond degraded failures), incipient failures were not.corisidered.
SCOPE The scope of the analysis used to construct the condidate Indicator was limited to o specific subset of operating plants for a specific time period due to staff resource constraints. The subset studied was further restricted to only those plants with nuclear steam supply systems (NSSS) de:Igned by GE that were op-erotional between January 1,1985 and March 31,1988. Further, the equipment considered was restricted to those BWR systems and components which histori-colly have been the dominant contributors to forced outages,i.e., ODE systems and components, that are within the NPRDS deportability scope. While this study was restricted to only one plant design, the methodology developed should be equally applicable to all plant designs.
The set of components in BWR ODE systems that was selected and analyzed was based on a compilation performed by the S. M. Stoller Corporoflon for the EPRI (Ref. 7). This compilation used the OPEC-2 database (Ref. 8) to determine and rank the contributing factors to plant unovollobility down to the component level. A number of the dominant contributors to piant unavallobility that were listed were related to either personnel or planned outages such as refueling.
These contributors were not considered. Equipment was also eliminated that
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l was structural, such as BWR recirculation piping,' or outside the current reportabil-ity scope of the NPRDS Table 1 lists the systsms and components that were 4
selected for this study.
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TABLE 1: BWR ODE SYSTEMS AND COMPONENTS J
SYSTEM CC/wlPONENT DESCRIPTION Cored Rod Dtvo Contrd Rod Mechanism j
Contrd Rod
..ored Rod Dfve Row ControlVdve Cor*d Rod Dtve Row Cored Vdve Operator Cored Rod Otve Supply Pump (Mntrd Rod Dtve Supply Pump Motor Cormd Rod Dtve Stmy PLtnp Motor Circut Brecher Feedwater Feedwater Han Pressure Heater feedwater Nmp Feedwater Pump Motor Feedwater Pump Motor Circuit beaker Feedwater Ptsnp furtune Feedwater Pump TLr%w Governor Mah Stocrn Man Steon Automatic Depresasuation Safety Valve Mdn staan Autornatic Depresataallon $arety Varve Operator Mdn Stean Contarveert toionen Vove
. Man Sloan Contonment isosation Vdve Operator Main Stean Contonment leolation Vdve Operator Circut Brecker Man Stean Screty/ Automate Depresurr#lon Ds:horge Pipe Vacwrfi 8 rec *er Man Steara Screty Vdve Neutron Mortforing hstrunentaflort Bstctne/Sultch hstrumentctrlort Indcators/ Recorders Inshtrnentattortiransnater/Primay Detector /Gement Reactor Reorcuatlon Inststanentation BstcrJe/Suitch hatrtsnenfattort indcators/Rocorders hsinsnenrattort frawnitter/Prirndy Detector /Sement Reactor Rodrcuation Pwnp Reactor RectcucPon Pump Motor Reactor Recteuction Ptsnp Motor Circut Brec*er Reactor Rodrcuation Punp Dscharge Vafve Redctor Ree?cuation Punp Dscnarge Vdve Operator Reactor Rodrcuation Ptsnp Ds:hcrge Vdve Operator CWcut Brecker Reactor Recteuction Ptsnp Suction Varve Reoctor Recycuation Pump Suction Vdve Operator Reactor RodrcsJation Punp Suction Vdve CDerator CZrcut Brecser Reactor Rodrcuation Punp Motor Generator Set Generator Reactor Rockcuanon Punp Motor Generoor Set Cotsaang Reactor Rodrcuation Punp Motor Generator Set Motor Rocctor Recycuation Ptsnp Motor Generator Set Motor Circut Brecker The equipment ilsted in Table 1 is not on o0 inclusive list..Bosed on M,esults of this study, some changes are in order. For example, the BWR fee Jwater regulot-Ing volve and its operator were not identified in the Stoller report as dominant contributors to BWR forced outoges. However, from the number of reported failures of these components found in the NPRDS during this study, these compo-nents were significant contributors to equipment forced outoges of some of the AEOD/S8048 11 9
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plants considered. Consequently, they should be added to the list of key out-oge-cousing equipment. Further, the NPRDS currently does not include certain balance-of-plant (BOP) systems and components that have historically been sig-nificant contributors to plant outoges, such as the turbine-generator and associ-oted support systems, the condenser, the circulating water system, non-nuclear portions of the service watet and closed cooling water systems, the instrument air system, and the service air system. At the most recem meeting of the NPRDS Users Group (NUG) held in December 1988, the NUG recommended to the Institute of Nuclear Power Operations (lNPO) that the deportability scope of the NPRDS be exponded to include the moln turbine, the main generator, and the condenser. This action marks the first official step in the NPRDS scope expansion process.
As on independent check on the selected outoge dominating systems and components, published results were reviewed of a study of plant ovaliability that was done by the North American Electric Rellobd.ty Council (NERC) using their NERC-GADS database (Ref. 9). This review confirmed the basis used for selecting the equipr'.ent listed in Table 1.
As a result of queries of the NPRDS based on these systems and components,it was found that 8 of the 37_ operating GE BWRs had too little dato to analyze because of either limited.conimercial operating history or,in some ecses, due to extended shutdowns during the study period'. In addition, $lg Rock Point does not report to the NPRDS because of its urilque design chor:1cteristics. Thus the validation was based on NPRDS failure data from 28 operating GE BWRs.
The use of the indiccior model and computerized algorithm developed during this study results in considerable time savings in the calculation of the condidate indicotor for the number of plants analyzed. However, this process still requires the manual downloading of large amounts of component failure dato from the NPRDS. Further manipulation of the downloaded dato is required to prepare the j
input for the algorithm. These two efforts are time consuming and labor-
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intensive. The destrobility of trending component failure rote has been recognized by NPRDS users. The current NPRDS user software hos the copobility to trend failure rate:in on automated way. Efforts have been initiated to see if expansion or modification of this software is possible so that it could provide the condidate indicator.
The following section of this report documents the validation method that was used to confirm the relationship of the tendidate NPRDS-based indicator to the Commission's definition of maintenance effectiveness.
AEOD/S804B 12 i
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J VALIDATION Volidation of the condidate indicator was accomplished through two tasks. The first task consisted of a root cause analysis of those component failure rate increases identified by the indicator. This analysis was done to determine if the indicator is o direct or nearly direct measure of molntenance effectiveness. In the second task, the condidate Indicator was compared statistically with on-other measure of molntenance effectiveness that is currently under develop -
ment, namely, the frequency of molntenance-coused reportable events docu-mented in Ucensee Event Reports (LERs) submitted in accordonce with 10 CFR 50.73 (Ref.10). While both the NPRDS-and the LER-based indicators are the subject of validation, o positive correlation between Indicators based on dato from different sources would be mutually reinforcing.
Applying the computerized algorithm technique to the NPRDS component failure data for the three year period considered resulted in between 0 and 8 indicottons for each of the ODE systems for o given plant, with the overage number of Indications per system per plant varying between 2 and 3. About half of the Indications were due to failures discovered during power operoflon and half were due to failures discovered during on outage. Forty of the component failure rote increases flogged by the cigorithm were examined by AEOD contractors at the Idaho Nc!!onal Engin'eering Laboratory (INEL) to establish the' relationship between the component failure rate increases and mo!ntenance effectiveness. This involved reviewing the NPRDS descriptions of the 500 component follares which contributed to the 40 failure rote increases and assigning the cause of each failure to one of five distinct categories:
(1)
Ineffective Maintenance - Foilures experienced while conducting, or os o consequence of, maintenance, upkeep, repair, surveillance, testing, and calibration of plant equipment. Examples include personnel errors of omission and commission by molntenance staff, procedure problems re-sulting in inadequate / improper maintenance, problems traceable to maintenance program administrative control, and equipment failures due to improper previous repair.
(2)
Rondom - Follures of this type usually occur in electronic equipment and are rare,In operating equipment. As the term implies, there is no pottern associated with the failure and, therefore, this type of failure would not be expected 00 be o recurring problem.
(3)
Design / Installation / Construction - Failures experienced while performing, or os o consequence of, design, f abrication, construction, and Installo-tion of. equipment, systems, and structures. Exorriples include personnel errors of omission and commission, procedure problems resulting in inode-l i
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.y-quote or Improper design or Installation, and problems traceable to de-sign or construction program administrative control.
(4)
Normal Agbg/Woorout/End of-Ufo - Failures caused by a component or system reaching its end-of-life by normal aging or weorout.
(5)
Unknown - Insufficient information was provided in the failure norratives to determine the root cause of the failure.
As shown in Figure 3,it was found that over three-fourths of the failures involved maintenance ine' festiveness. On a plant-specific basis, the contribution as-cribed to Ineffective molntenance ranged from about 25 percent to 100 per-cent.
The strong relation-ship of these fcilures to maintenance inef-festiveness hos been ODE EQUIPMENT FAILURE C AUSE' confirmed in other ALL PLANTS REVIEWED studies. Forexample,
_a tr, ends and patterns j
analysis was com-pleted by AEOD of NPRDS failure data for M"I"c'M38"
- moln feedwater 4~
i (MFW) flow control i
volves, MFW flow jjljjjliit w
control bypass volves,
~
and MFW pumps in U**d?"
I I
U.S. commercial pres-wearout
(*)
surized water reactors Ragom Un wn (PWRs) (Refs.11,12).
The primary finding of this analysis was that
@ASED ON NPROS N.URE NARRA~MVES) differences among plants that could be Figure 3 traced to differences l
In maintenance proc-l tices had a greater influence on the follure rate of these components than any l
of the component design features studied. This result was independently ob-toined, but echoed the results of a 1980 Electric Power Research Institute (EPRI) l study of MFW pump performance (Ref.13). The EPRI report concluded that the l
ultimate performance of a major component such as a pump is offected more l
AEOD/S80dB M
j
)'
~1 by how it is molntained than by the selection of a specific pump manufacture".
AEOD hos also performed a trends and patterns onclysis of moln steam isolation volve (MSIV) failures at both PWRs and BWRs (Ref.14). Based on NPRDS dato, the -
major finding of this analysis was that proper molntenance was o dominant means for minimizing MSIV problems at both PWRs and BWRs.
The second validotion task determined if positive correlations existed in cases where plants with high frequencies of operating events which con be ascribed to molntenance deficiencies also exhibit a high degree of ODE Indication, and whether plants with moderate and low frequencies of molntenance-related events exhibit moderate and low degrees of ODE indicotton, respectively. The events used in th!s comparison were those reported to the NRC in LERs. A corre-lotion was found between the condidate indicator and the LER-based molnte-nonce-coused event frequency. This correlation reinforces the conclusion that NPPDS con support a useful maintenance effectiveness indicator. A detailed explanation follows.
Using the historical LER datobose in the Sequence Coding and Search System (SCSS) (Ref.15), the Nuclear Operation and Analysis Center (NOAC) of the Ook Ridge National Laborotory (ORNL) developed a technique to classify the causes of the events reported in LERs. One of these causes is molntenance. The classifi--
cation technique uses specific search cigoritnms to produce the some results as manual cause coding of LERs by experienced engineers. Each event con be categorized by one or more causes.
The rnointenance cause category covers the entire range of programmatic deficiencies related to maintenance, surveillance, testing, and calibration.
These deficiencies are deemed attributable to poor molntenance practices or errors made by maintenance personnel. The deficiencies include:
(1)
Maintenance personnel errors - Personnel errors associated with the per-formance of surveillance, testing, collbration, or rodlotion protection activities; and (2)
Poor maintenance practices - Equipment failures that are strongly indico-tive of maintenance problems such as improper lubrication, corrosion due to boric acid precipitation, short circuits, and improper prior repairs.
To eliminate the effects of the startup of NPRDS reporting on the condidate Indicator count, the analysis was opp!!ed to those BWRs which began commer-clat operation prior to Janudry 1,1985. Hence,the number of BWRs considered was reduced from the 28 used.!n the first part of the condidate Indicator volldo-tion to 23. The mean number of maintenance-related events occurring per month during the period of interest at each of these 23 BWRs was calculated AEOD/S804B 15
.m..__-.__._._.___
m j
(1]'
b'osed on trie number of events in the SCSS LER datobose that involved molnte-nonce deficiencies (i.e., molntenance-related events). This mean molntenance-related event frequency provides :ome comparative measure of molntenance performance. That is, plants with the highest mean frequency of molntenance-related events seem to experience the greatest difficulty with their maintenance programs compared with other plants. Using similar techniques, the condidate indicator was also coiculated.
Using a linear correlation analysis, the degree of assoclotion between the condi-date indicator and the mean molntenance event frequency for the 23 BWRs was then examined. The analysis calculated a correlation coefficient between the condidate indicator and the mean molntenance-related event frequency of 0.6. (A correlation coefficient of zero (0) indicates there is no relationship be-tween the varlobles. When there is perfect correlation and the verlobles very in.
~
the some direction, the coefficient is 1.0 (positive correlation). When there is perfect correlation but the vorlobles vary in opposite directions, the coefficient is
-1.0 (negative correlation). The correlation coefficient con vary between the ex-tremes of -1.0 and 1.0 to indicate some Intermedlote degree of correlation). This positive correlation was statistically significant at the 0.01 level, Indicoting that the correlation was not due to rondom fluctuations in the dato. Figure 4 shows how the two variables trend in the Jame direction. These results illustrate that the indicator cormloted acceptably well with LER-bas.e'd data. Thus, th'e sec' nd
~
o part of the validation process was satisfied.
The correlation between the NPRDS-based condidate NPRDS INDICATOR VS LER-BASED DATA indlCotor and the LER-based MtNTENANCE.RELATED EVENTS dato,When cVeraged over a long period of time,is not entirely unexpected since h
the NPRDS failures were g,j shown to result primarliy from e so o4r4 j
g maintenance ineffectiveness,
+
and the some finding was g
/*
- +-
made for failures found in e
~'f
,,84 LERs in NUREG-1212,the A+,+++
g stoffs trend and pottern
.,7 ano!ytis of industry mainte-A,,.*
5 nonce (Ref.16). The indl-
, 9+*
I cated strength of the corre-
+
" * " ^ ' "
,4 lotion is quantitative confir-motion of the general relo-
"7
. =no e. ao. = o u= =am m a.
tionship of these two sources Figure 4 i
AEOD/S804B 16 i
f
. f.
l for measuring maintenance effectiveness. The correlation reinforces the poten-tiol value of cause codes as on additional source of information for monitoring molntenance effectiveness.
In the construction and validation of the condidate Indicator, oil failures were used, including those dlscovered during power 6peroflon and those discovered during shutdown. No distinction was made regarding the mode of operoflon since all of the events were actual failures and not incipient conditions. Further, the failures most likely occurred during operation, although the discovery of some of the failures could not occur untilthe plants were shut down. Overall, obout hoff of the failures were discovered during operation and half were discovered during shutdown. Ukewise, the failure rote increases that were flogged by the condidate indicator were due to failures that were discovered approximately equally between operation and shutdown. In both operoflon and shutdown, the validation indicated that failure increases showed evidence of ineffective maintenance. An aggressive preventive molntenance program would seek to identify and correct problems prior to the occurrence of octual failures such as these.
Thus, tracking all reported failures regardless of the plant operational status when the failures were discovered showed merit for indlcating molntenance effective-ness. In addition:the use of follures discovered.during plant shutdowns will' allow gouging of the general condition of equipment entering the outage and the potentlot for ineffective corrective maintenance during on outage. The quality of the maintenance during on outoge sets the tone for operation in the next cycle. The next section discusses o number of situations where increased failure rates due to failures discovered in on outoge preceded on equipment forced outage experienced soon offer restart.
RELATIONSHIP WITH EQUIPMENT FORCED OUTAGES Because of the nature of the equipment whose historical data was used in the construction and validation of the condidate indicator,it is a logical hypothesis that there may be a relation between the indicator and the occurrence of equipment forced outoges (EFOs). In this study, increases in the component failure rote for a given system are viewed as indicative of the general condition of the system. This analysis postulated on increased chance of an EFO occur-r!ng, given on observed increase in the failure rate. The usefulness of the condi-d6te ind!cator would be enhanced if it r,rovides o more timely indicotlon of the potential for on EFO. This analysis examined the operoflonal experience of the 28 plants in detall. The results for the individuol plants are contained in the proprietary Appendix A of this report.
AEOD/S804B 17
---m_____.___
'4 l
l.,' '
o, l
1 i
i This onelysis examined historical dato that combined NPRDS failure Information with forced outage information from NUREG-0020 Ucensed Operating Reactors Status Summary Report (Ref,17), The objective of this effort was to see whether on increase in the rote of reported system component failures preceded on EFO involving that some system. Although this seemed like o reasonoble expecto-tion, there are a number of reasons why on increase in the system component fallure rate indicated by the set of dato analyzed might not result in a forced outoge. These include:
(1) -'
The redundancy of the equipment design in each plant may be such
~
that a specific system con tolerate o number of failures without the plant being required to shut down:
(2)
An o0gressive molntenance program may have discovered and fixed the problem equipment; and (3)
A single component failure con result in on EFO'with no previous warning.
Therefore,it was recognized that the tie between the condidate indicator and EFOs may not be very strong.
To perform this analysis, c'omponent failure records for each of the ODE systems
' were obtained from the NPRDS(see proprietary Appendix B) and a listing of all the EFOs tho+ were related to the ODE systems was extracted from NUREG-0020 (see Appendix C). The forced outage and equipment follure data were com-bined and arranged chronologically for each plant, in this manner, chronolo-gies were ossembled from approximately 3.000 component failures and 200 EFOs involving selected equipment in the reactor recirculation, neutron monitoring, control rod drive, feedwater, and moln steam systems of the 28 BWRs. The trend in the rote of component failures within each system was examined using plots of cumulative failures os a function of time (months) on which were superim-posed the historical EFOs and the operoflonal history of the plant (l.e., all planned and unplanned outage periods).
Recognizing the limitations just listed, the analysis provided some positive results.
Ten of the 28 plants evoluoted experienced at least one EFO over the three-year perioo studied which was preceded by on increase in the failure rote of the components within the system that was ossociated with the forced outoge. The lead times observed for the failure rate increase prior to on EFO generally ranged from two to s!x months. While these results indicate that there may bs a relationship between the condl dote indicator and EFOs, this relationship is not very strong.
AEOD/S8048 18
. ;- 7'
=
/ o
,o in general for all of the plants ' considered,the best results were found for equip-1 ment in the reactor recirculation, feedwater, and moln steam systems. Both the control rod drive and neutron monitoring systems experienced large numbers of failures, but few EFOs. Each of these two systems is composed of highly redun-
' dont components and has a copocity to absorb failures up to the limits 1mposed by technical specifications. These systems / components did not play a major role in this plant onelysis. However,the rate of accumulation of these kinds of failures coming out of a refueling outage could be o measure of the effective-g ness of the molntenance performed in the outage.
The current scope limitations of the NPRDS ruled out examining the failure experi-ence for systems such as the main turbine and the main generator which domb noted the EFO experience at severci plants. This factor impacted the number of plants for which results could be demonstrated. Another limitation was that in-cipient failures are reported voluntarily to the NPRDS. Because of this, such '
follures were not used in this analysis to ensure that the results would not depend on these failures and, consequently, be invalidated if licensees had modified
~
their reporting practices during the study time period.
Given these limitations, from the results for some specific plants, the condidate indicator oppeared to have some limited poter)tlalin providng a warning signot prJcrt6 on associated EFO. However, as anticipatect, the results did not show o'n overall statistically strong relationship' between the condidateindicator and EFOs. Nevertheless,it oppears that the condidate indicator performed as expected.
FINDINGS AND CONCLUSIONS i
RNDINGS The major findings of this study cre:
(1)
Based on a review of the indMdual failures in the NPRDS, increased component failure rates within a system are generally associated with traintenance effectiveness; (2)
Detailed engineering studies that employed both statistical and deter-ministic analyses have shown a nexus between ineffective molntenance ond NPRDS-reported failures of ODE equipment,i.e.,feedwater regulot-l ing volves, moln feedwater pumps, and MSIVs; AEOD/S804B 19
.________._m_..__________________.______._.____..___________.____._.._______________.___._________m_
y
.,.7 -
j'
,~
c.
'o s 9;
j pyf;,[j 7
.n a
- -s lt
'(3)
An equipment forced outoge due to a follure of a specific system was sometimes preceded by on increased rate of failure of equipment in that l system; (4) l The frequency of molntenance problems connect 3d with reportable' events showed a positive corrclotion with the magnitude of the condi-do's !ndicotor for the period analyzed; and -
(5)
Implementation of the condidate ladiccior by the NRC stoff on on '
IndvMryside basis would be labor Intensive. Consequently, more effi- '
cient dato techniques need to be developed.
L CONCLUSIONS.
(1)
A practical and useful maintenance pedormance indicator was deve!-
oped using NPRDS data. This indicator con serve os a suitable basis for -
describing a maintenance effectiveness tracking method which is oc-ceptable to the stoff in the forthcoming Maintenance Rule regulatory guide. Other indicatoss could be developed from the NPRDS data.
g
[(2)
The ability of the condidcte indicator and the NPRDS dato to refiect
, t'nointenance ef'ect!vonass was confirmed.
(3)
The effect of non-uniform NPRDS reporting con be acceptably mlnlmized through ihe use of a standard subset of equipment that is important to.
plant operoflons.
(4)
The value of the condidate indicator was confi.rned through:
Root cause analysis; Independent dato derived from LER-raported, molntenance coused events; Correlations with other studies; and Correlations v/ith the findings ' rom molntenance effectiveness t6cm inspections, j
While the focus of this report is on the use of NPRDS to monitor mo!nte-nonce effectiveness, the mutuo!!y reinforcing correlation cetween LER-based dato and the NPRDS-based indicator points to the prospect of on hEOD/S804B 20
-ew_____m
-- mm-
- - - - - ~ - - - - - - - - -
7,,....'
. ll*.
i:
n' additional rnointenance indicator. The LER-based dato useo in this cor.
. relation resulted from the ongoing performance Indicator development effort aimed to dernonstrate the u6efulness of cause codes,~ one of which is maintenance. Further development of this molntenance cause code :
" m LC.Rs is being pursued for use in monitoring molntenance effective "
E ness.
L4
. (5)
- Although the methodology used in this study was developed using dato E
for 28 BWRs, it should prove equally valid for other plant designs.-
(6)
For cost-effective NRC staff use of the condidate Indicator on'an indus-
. try-wide basis, further development is necessary to more efficiently ex-i tract the Indicator dato from the NPRDS and to display it in a manner
.which permits indMdual os well as generic comparisons. These efforts will.
receive high staff priority and the results of these activities will be shared with industry.
)
e D
g 9
p 4
e e
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O i
AEOD/S804B 21
_ _ _ _ _ = _ _ _ _ - - _ _ _ _ _ _ _ _ _ _ _
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/
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~
REFERENCES 1.
" Preliminary Results of the Trial Program on Maintenance Performance Indicators / AEOD/S804A, Office for Analysis and Evoluotion of Operational Doto, U.S. Nuclear Regulatory Commission, Washington, D.C., October 1988.
2.
Letter from John B. Mortin, Regional Administrator, USNRC, Region V, to i
D. W. Cockfield, Vice President - Nuclear Portland General Electric Company,
Subject:
Inspection Report No. 50-344/88-30 Enclosure 2, dated December 2,1988.
3.
Letter from' Thomas T. Mortin, USNRC, Region I, to C. A. McNeill, Executive Vice President - Nuclear, Philadelphia Electric Company,
Subject:
Com-bined Inspection Report Nos. 50-277/88-17 and 50-278/88-17. Enclosure 2.
dated October 11,1988.
4.
Letter from Hubert J. Miller, USNRC, Region ill, to Murry Edelman, Presi-dent, Toledc Edison Company,
Subject:
Inspection Report No. 50-346/
88029(DRS), Enclosure 2: dcted Becember 16,1988.,,
5.
'The Nuclear Plant Reliability Dato SyGem Program Description / INPO 86-010,!nstitute of Nuclear Power Operoflons, Atlanto, Georgia,1986.
6.
'NPRDS Reporting Procedures Manual / INPO 84-011, Institute of Nuclear Power Operations, Atlanto, Georgia,1984 (Proprietary).
7.
Results of this compilation have been published in a series of Electire Power Research Institute (EPRD reports: EPRI-NP-5544, EPRI-NP-4368, and EPRl-NP-3480.
8.
' OPEC-2 System / The S. M. Stoller Corporation,1250 Broadway, New York, New York.
i 9.
" Generating Availability Report 1982-86,* North American Electric ReHobility Council, Princeton, New Jersey, no publication dote given.
10.
10 CFR 50.73,' Licensee Event Report System.'
11.
Trends and Potterns Progrom Report - Operoflonal Experierce Feedbcck on Main Feedwater Flow Control and Moln Feedwater Flow I
AEOD/S804B 22
1
, 4.
,o 4 '3 ' '
Bypass Volves and Volve Operators," AEOD/P701, Plumlee Ill, G. L, Office for Analysis and Evoluotion of Operoflonal Data, U.S. Nuclear Regulatory Commission, Washington, D.C., August 1987 (Proprietary).
12.
" Technical Evoluotion Report on Operational Experience Feedback for Moln Feedwater Pumps and Their Assocloted Components /
EGG-NTA-7010, Revision 1, Gentillon, C. D., Meachum, T. R., and Pace, N. E., EG&G-Idaho,Inc., Idaho Falls, Idaho, November 1987 (Proprietary).
13.
"Evoluction of Basic Causes of Repetitive Failures of Nuclear and Fossil Feedwater Pumps,' EPRI NP-1571, Electric Power Research Institute, Polo Alto, Califomic, October 1980.
14.
"Technico! Evoluotion Report on Operoflonal Experience Feedback for McIn Steam isolation Valves and Their Associated Operators,"
EGG-NTA-8126, Fish, L W., Gentillon, C. D.. Meachum, T. R., EG&G-idaho, in.c., Idaho Falls, Idaho, November 1987 (Proprietary).
15.
" Sequence Coding and Search System for Ucensee Event Reports,'
NUREG/CR-3905, Volumes 1-4, Nuclear Operations Analysis Center, Ook Ridge National Laboratory Ook Ridge, Tennessee, April 1985.
e 56.
"St6tus of Maintenance in.ihe U.S. Nuclear Power Industry 1985," NUREG-1212, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, D. C., Volumes 1 and 2, June 1986.
17.
'Ucensed Operating Reactors Status Summary Report,' NUREG-0020, U.S. Nuclear Regulatory Commission, Washington, D. C., published monthly.
I i
e i
AEOD/S8048 23
~ R 5
1
/
'o UNITED STATES
- 2
,f
(/'j NUCLEAR REGULATORY COMMISSION g *-
g W ASHIN GTON. D.C. 20555 o,
a g, v,#
j May 11, 1989 OFFICE OF THE SECRETARY i
i l
MEMORANDUM FOR:
Betsy Shelburne, Chief Public Document Room
-r THRU:
Sandy Showman, efg Correspondence and Reebrds Branch FROM:
ew Bates, Chief Operations Branch
SUBJECT:
RELEASE OF SECY-89-044 AND SECY-89-046 TO THE PDR Attached for placement in the PDR are advance copies of:
" Report on Maintenance Performance Indicator Develpment" (without Proprieta2 Enclosure)
" Performance Indicator Program Development -
Cause Codes" The request for release was made by EDO and all Commission offices concur.
Attachments:
As stated cc:
DCS - P1-24 l
DFoT
(
1 l
l
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l I
l l
l