IR 05000454/1998015
| ML20236T240 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 07/22/1998 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20236T237 | List: |
| References | |
| 50-454-98-15, 50-455-98-15, NUDOCS 9807280054 | |
| Download: ML20236T240 (14) | |
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U.S. NUCLEAR REGULATORY COMMISSION
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REGIONlli (
Docket Nos:
60-454: 50 455 License Nos:
50-454/98015(DRS); 50-455/98015(DRS)
Licensee:
Commonwealth Edison Company (Comed)
Facility:
Byron Generating Station, Units 1 & 2 Location:
4450 N. German Church Road Byron, IL _61010 i
Dates:
July 6 - 9,1998 Inspectors:
Andrew Dunlop, Reactor Engineer (Team Leader), Rlll Sonia Burgess, Senior Reactor Analyst, Rill Anthony Fresco, PSA Consultant, BNL i
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Approved by:
- James Gavula, Chief Engineering Specialists Branch 1 Division of Reactor Safety
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EXECUTIVE SUMMARY Byron Generating Station, Units 1 & 2 NRC Inspection Reports 50-454/98015; 50-455/98015 This inspection was a follow-up of the April 1997 maintenance rule baseline inspection that reviewed the licensee's implementation of 10 CFR 50.65, " Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants." The report covers a 4-day on-site inspection by regional inspectors and a contractor from Brookhaven National Laboratory.
The program met the requirements of the maintenance rule (MR) and concerns and open issues identified during the baseline inspection were adequately resolved.
Maintenance The low-safety-significance risk ranking for four ventilation systems, questioned during
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the baseline inspection, were considered appropriate based on additional analysis and calculations that demonstrated that operability of associated high significant equipment would not be affected.
The required periodic assessment, issued in March 1998, contained several good
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overall evaluations of the effects of the maintenance rule on the maintenance program.
The assessment met the requirements of the maintenance rule, although it was not issued in a timely manner. The implementation of the Outage Risk Assessment and Management Program demonstrated the licensee's commitment to making improvements in the control of outage risk.
The establishment of performance criteria and goal setting was considered acceptable.
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The reliability and unavailability performance criteria established were adequately linked to the values assumed in the probabilistic safety assessment, which resolved the concem identified in the baseline inspection. In addition, the revised performance criteria for the fuel handling and emergency lighting systems were acceptable.
Quality Assurance The recent corporate assessment of Byron's maintenance rule program was good and
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demonstrated Comed's intent to continuously improve maintenance rule programs based on lessons learned.
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Report Details Summarv of Plant Status Unit 1 and Unit 2 were operating at full power during the inspection.
II. Maintenance M1 Conduct of Maintenance (62706)
The primary focus of the inspection was to follow-up on issues identified during the April 1997 baseline inspection (NRC Inspection Reports 50-454/97004; 50-455/97004) to vr **y that the licensee had implemented a maintenance monitoring program which sawiied the requirements of 10 CFR 50.65," Requirements for Monitoring the Effectiveness of the Maintenance at Nuclear Power Plants," (the maintenance rule).
The inspection was performed by two regional inspectors and a consultant from the Brookhaven National Latsoratory.
M1.2 Safety (Risk) Determination. Risk Rankina. and Exoert Panel a.
Insoection Scoce Paragraph (a)(1) of the maintenance rule (MR) required that goals be commensurate with safety. Additionally, implementation of the MR using the gddance contained in NUMARC 93-01, " Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," dated April 1996, required that safety be taken into account when setting performance criteria and monitoring under paragraph (a)(2) of the rule.
This safety consideration was to be used to determine if the structure, system or component (SSC) should be monitored at the system, train or plant level. The inspectors reviewed the methods and calculations that the licensee established for making these risk determinations with respect to the four ventilation systems whose low safety significance ranking was questioned during the baseline inspection. The ventilation systems were for the diesel generator (DG) rooms, the battery rooms, the miscellaneous electrical equipment room (MEER), and the control room.
b.
Observations and Findinos in response to the risk ranking questioned during the baseline inspection, the expert panel re-reviewed all four systems and determitied that the systems were still considered to have low safety significance. Documentation and calculations showed that the control room, battery room, and the MEER room temperatures would remain below the equipment qualification temperature of the critical equipment within the rooms
'or approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. Hot standby conditions could be established well within this period, at which time opeiators were procedurally directed to provide alternate methods of cooling the rooms. With regard to the DG ventilation, the licensee determined that the loss of room ventilation had no impact on the DG operation duri.1g the mission time
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The most limiting electrical component was determined to be a relay that could function properly when exposed to a temperature of approximately 170*F. The inspectors verified that operators were procedurally directed to provide attemate methods of cooling the DG rooms. Thece actions included methods such as manually opening large doors if power was not avai!able to use portable fans.
The inspectors also noted that although the four ventilation systems were classified as low safety significant, all had acceptable reliability and unavailability performance criteria
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in place that would be required for a high safety significant system.
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Conclusions The risk ranking for the four ventilation systems were appropriate based on additicnal analysis and calculations that demonstrated that operability of high safety significant equipment would not be affected. Further, procedures were available and actions for compensatory measures coulri be taken during an actual event before the room temperature would affect the high safety significant equipment.
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Insoection Scooe Paragraph (a)(3) of the MR required that performance and condition monitoring sctivities
and associated goals and preventive maintenance activities be evaluated, taking into
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account, where practical, industry-wide operating experience. This evaluation was required to be performed at least one time during each refueling cycle, not to exceed 24 months between evaluations. The inspectors reviewed the procedural guidelines for these evaluations and the January 1996 through June 1997 periodic assessment.
b.
Observations and Findinas The assessment followed the licensee's guidanc1 and was acceptable, although the discussion on industry-operating experience did not provide insights into how it was effectively used. Several good findings from the assessment included determining underlying causes for why SSCs went to (a)(1) (e.g., preventive maintenance program, design problems, or poor maintenance practices) and preventive maintenance changes resulting from the MR program. Although the initial 18-month periodic assessment period ended in June 1997, the assessment report was not issued until March 2,1998,8 months after the period ended. This was not considered timely as issues discussed in the report may have changed due to the delay in completion and issuance of the report to management personnel. In addition, the assessment was only provided to licensee management and not to the system engineers who have a significant role in the implementation of the program and may benefit from reviewing accomplishments on other systems by incorporating that approach into their own systems.
Subsequent to the licensee's assessment, Comed corporate issued a new procedure to i
provide guidance for performing assessments, NSP-ER-3011, Maintenance Rule
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l Periodic Effectiveness Assessments, for all operating facilities to follow. A review of the
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procedure determined that it followed the same structure as Byron's completed assessment. The guidance was flow chart based, which documenteu each area required to be assessed and who was the responsible individual.
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Conclusions The assessment conducted by the licensee was acceptable and contained several good assessments of the effects the MR had on the maintenance program, although issuance l
was delayed and considered uritimely. The new corporate procedure for performing periodic assessments met the requirements of the MR.
M1.4- (a)(3) Balancina Reliability and Unavailability a.
IDsoection Scoce Paragraph (a)(3) of the MR required that adjustments be made, where necessary, to assure that the objective of preventing failures through the performance of preventive maintenance was appropriately balanced against the objective of minimizing unavailability due to monitoring or preventive maintenance. The inspectors reviewed the licemee's plans and the periodic assessment to ensure this evaluation was performed as required by the rule.
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Observations and Findinas The licensee's approach to balancing reliability and unavailability coristed of monitoring SSC function performance against the established performance criteria. This task was performed during the periodic assessment. The assessment reviewed SSC functions based on four catego:ies: (1) performance criteria was met [(a)(2)] and appeared to be set properly based on actual perfor. nance; (2) performance criteria was met [(a)(2)] and i
appeared to be set improperly based on actual performance such that a criteria change may be appropriate; (3) performance criteria was not met [(a)(1)] but appeared to be set
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properly based on actual performance; and (4) performance criteria was met [(a)(1)] and appeared to be set improperly based on actual performance such that a criteria change may be appropriate. Several availability performance criteria were revised due to actual
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SSC performance to be a better system performance indicator. In addition to balancing i
during the periodic assessment, balancing was reviewed when an SSC went from (a)(2)
to (a)(1).
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Conclusions
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The inspectors concluded that the licensee's method of balancing reliability and unavailability met the intent of the MR.
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M1.5 (aV3) On-line Maintenance Risk Assessments a.
Insoection Scoce Paragraph (a)(3) of the MR states that, in performing monitoring and preventative
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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. During the baseline inspection, the inspectors noted that the licensee was j
plunning to introduce an industry standard computerized risk monitoring program for the
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November 1997 outage. The inspectors reviewed the status of the outage risk management program and also reviewed any other changes in the licensee's program for performing safety assessments when taking equipment out-of-service during power operation.
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Observations and Fintogs The only change in the program for performing safety assessments when taking equipment out-of-service during power operation was that a corporate procedure, NSP-WC-3006, "On-Line Maintenance," had been issued to supersede the sns-specific procedures in place at all of the Comed plants. The issuance of this procedure did not substantially affect the program since the new procedure had used the Byron procedure as the model.
The licensee implemented the Electric Power Research Institute (EPRI) developed Outage Risk Assessment and Management Program (ORAM) for the April 1998 Unit 2 outage. ORAM has the capability of determining the tima to boiling in the reactor vessel, the time to core damage, and the time to boiling in the spent fuel pool for all of the various plant configurations occurring during an outage. ORAM provided colored indications of risk levels: green, yellow, orange, and red. During the outage, the outage coordinator ran ORAM routinely once per week to determine the risk cf scheduled outage work. Twice per day (once per shift), the coordinator also looked at Byron Outage Guidelines System Status Sheets, which provided an indication of the specific status of electrical power control, containment, fuel pool cooling, reactivity control, inventory / decay heat removal, and vital systems (component cooling water and cooling tower basin makeup water). In this manner, the outage coordinator maintained awareness of emergent risk situations and was able to reschedule work as appropriate l
in conjunction with the revised results of the ORAM program.
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Conclusions The inspectors concluded the licensee's procedures to address the risk associated with on-line maintenance activities and shutdown risk management were acceptable. The i
implementation of the ORAM computerized program demonstrated the licensee's commitment to making improvements in the control of outage risk.
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M1.6 (a)(1) Goal Setting and Monitoring and (a)(2) Preventive Maintenance (PM)
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Insoection Scone
The inspectors reviewed program documents in order to evaluate the process l
established to set goals and monitor under (a)(1) and to verify that PM was effective l
under (a)(2) of the rule. The inspectors reviewed several systems to verify that goals or performance criteria were established in accordance with safety, that industry wide operating experience was taken into consideration where practical, that appropriate monitoring and trending were being performed, and that corrective actions were taken when an SSC failed to meet its goal or performance criteria or experienced a rnaintenance preventible functional failure. These issues were reviewed for the systems identified in the violation issued from the basefine inspection.
b.
Observations and Findinas I
The inspectors determined that the MR procedure provided appropriate guidelines for establishing performance criteria / goals for SSCs scoped under the MR. The incensee had established performance criteria and/or goals for all SSC functions designated within scope. The performance criteria were based on functional failures (FFs) versus
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maintenance preventible functional failures, which was considered a conservative l
approach. The concems identified during the baseline inspection were adequately resolved, as discussed below.
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I b.1 Performance Criteria for Reliability and Unavailability
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In response to the vio'ation identified during the baseline inspection concerning the linkage between the performance criteria and the assumptions in the probabilistic safety assessment (PSA), the licensee generated a new calculation uculation BYR97-372 R3,"PSA Basis for Byron's Maintenance Rule Performance Criteria." The calculation documented the process for establishing the availability and reliability performance criteria for the MR functions of SSCs that were modeled in the PSA.
Specifically, the availability performance critelia were entered into the Byron Risk Monitoring Query System PSA model, which was the same version of the PSA model and data in effect during the baseline inspection. When factored into the PSA, the availability performance criteria caused an increase in the core damage frequency from 1.15E-05 per year to 2.75E-05 per year, an increase of 139% The licensee considered this increase to be acceptable as compared to a maximum permanent increase in core
damage frequency of 870%, which would be allowable for a baseline core damage frequency (CDF) of 1.1E-05 per reactor year according to EPRI TR-105395, "PSA I
Applications Guide," and furthermore that it was highly unlikely that all MR functions wou d be performing at their maximum allowable limit during the course of the 24-month monitoring period. The inspectors considered these assumptions to be appropriate.
Therefore, the inspectors considered the increase in CDF to be reasonable and concluded that the availability performance criteria were appropriately established and based on the PSA data.
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l The reliability performance criteria were established in the same calculation. Both I
individual train level and aggregate system level performance criteria were established.
l The statistical methodology involving the binomial distribution and the Poisson
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distribution described in EPRI Technical Bulletin 96-11. " Monitoring Reliability for the l
Maintenance Rule," and EPRI Technical Bulletin 97-03 " Monitoring Reliability for the Maintenance Rule - Failures to Run," were applied to the failure rates assumed in the PSA for those SSCs modeled. For each high safety significant function that had been i
modeled in the PSA, the licensee first determined proposed performance criteria at the
train level. Then, using the methodology, aggregate limits on the total number of failures considered acceptable for sets of redundant trains were determined using the binomial distribution for standby demand type failures and the Poisson distribution for
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time dependent running failures. For a given PSA failure rate and assumed number of l
demands or running time over a 24-month period, the binomial distribution for standby l
failures or Poisson distribution for running failures were calculated to determine the probability of zero, one, two or more demands. If the probability of having the number of failures specified by a particular performance criterion was less than 5% (or equivalently was greater than 95%), then the performance criterion was considered to allow too many failures and the criterion was adjusted to be more conservative.
For certain functions which involved both standby and running failures, the standby and running failures were combined by converting the standby failure rate to a probability i
and adding that value to the running failure probability. The combined failure probability l
was then substituted into the Poisson distribution to determine the acceptable aggregate performance criterion for the respective function. The aggregate limits of the reliability performance criteria ranged from 0 for the reactor coolant system leakage rate to 30 FFs per 24 months for 4 trains in both units for the high head safety injection function, which the expert panel reduced to 12 FFs. The individual train performance criterion was 2 FFs. In one case, for the steam generator atmospheric pressure control function (MS 4), the results of the statistical approach showed that zero failures could be tolerated. However, the licensee determined that one functional failure per 24-month period could be tolerated by substituting the higher failure probabit!ty into the PSA model. The PSA CDF for this case, when added to the 139% increase in CDF attributable to the availability performance criteria alone, increased by 3% for a total combined CDF increase of 142%. Based on the small increase, the licensee considered the higher performance criterion for MS 4 function to be acceptable.
Since the limits for the reliability performance criteria were established using the data in the Byron PSA, and the licensee performed a sensitivity study showing an acceptable increase in CDF for the one exception of the MS 4 function, the inspectors considered the reliability criteria to be directly and appropriately linked to the PSA assumptions.
b.2 Emeraency Lichtina Based on the concerns identified in the baseline inspection, the licensee revised the performance criteria for the emergency lighting function (LL1). The performance criteria were based on historical performance of the emergency lighting units (ELUs) and allowed less than or equal to 62 FFs in a two-year period for the 206 ELUs in scope of
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the MR and no repetitive failures on individual ELUs. Although the number of allowed failures appeared high, it included 8-hour discharge test failures, along with failures associated with the quarterly test acceptance criteria such as light bulb failures, low voltage, low battery water level, which provided some predictive information about
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battery degradation. Based on the 8 tests performed on each ELU, this resulted in an j
approximate 15% failure rate. This was considered acceptable to resolve the concern.
l The LL1 function was placed into (a)(1) as a result of a 2-year review that identified 89 total FFs. One of the main causes for the high number of failures was the lack of a preventive maintenance (PM) program for the ELUs as identified in the baseline inspection. The licensee's corrective action for this (a)(1) system included establishing some PM program. Since one of the major concems was degradation of the batteries, a number of older batteries were scheduled for replacement. Although no definitive PM j
program has been put in place, the system engineer was tracking failures and test I
results for each ELU in order to establish an acceptable replacement frequency.
b.3 Fuel Handlino Eauioment Based on the conccms identified in the baseline inspection, the licensee revised the performance criteria for the fuel handling equipment function (FH1) to handle and transport fuel and related components reliability performance criteria. The initial concern was that the performance criteria could allow a number of significant failures (e.g., damage fuel assemblies) along with other minor equipment failures. The one I
criterion was revised to three separate criteria as follows: (1) no FFs resulting in fuel j
damage or fission product release; (2) less than or equal to one FFs in two years that could cause fuel damage or fission product release; and (3) less than or equal to five FFs in 2 years for all other equiprnent failures. These criteria were considered acceptable to resolve the concern.
i b.4 Goals Established for (aV1) SSCs The inspectors reviewed a number of (a)(1) disposition checklists and documentation summaries to ensure adequate goals and corrective actions were identified. The l
licensee had good documentation for each (a)(1) system function that identified the
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problem that caused the function to go to (a)(1), the goal established, how industry-wide operating experience was used, and the corrective action plans to return the system to (a)(2). Goals and corrective action plans appeared to be appropriate for those functions in (a)(1).
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Conclusions The performance criteria established and goal setting process were considered acceptable. The unavailability and reliability performance criteria for high safety significant SSCs were adequately linked with the reliability values assumed in the PSA.
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l M7 Quality Assurance in Maintenance Activities (40500)
M7.1 Licensee Self-Assessments of the Maintenance Rule Prooram a.
Insoection Scooe The inspectors reviewed the March 1998 corporate assessment of the Byron MR implementation.
b.
Observations and Findirigs The licensee's corporate assessment was conducted as part of Comed's process to provide periodic oversight of major station programs. The assessment focused on the implementation of the MR program to ensure lessons learned had been adequrtely incorporated. Severalissues and recommendations were identified during the assessment. Corrective actions have been impmented or are in process for these issues.
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Conclusions The recent corporate assessment was good and demonstrated Comed's intent to continuously improve MR programs based on lessons leamed.
M8 Miscellaneous Maintenance issues M8.1 (Closed)Insoection Followuo item 50-454/97004-01(DRSh 50-455/97004-01(DRSh This issue concemed the low risk significance determinations for four ventilation systems. Based on the discussion in section M1.2 of this report, this issue is closed.
M8.2 (Closed) Insoection Followuo item 50-454/97004-02(DRSk 50-455/97004-02(DRSh This issue concerned not having completed a periodic assessment as required by (3)(3)
of the MR prior to the baseline inspection. Based on the completion of an assessment as discussed in sections M1.3 and M1.4 of this report, this issue is closed.
M8.3 (Closed) Violation 50-454/97004-03(DRSh 50-455/97004-03(DRSh This violation concemed the failure to establish an acceptable link for the reliability performance criteria to the failure rates assumed in the PSA, and the inadequate reliability performance criteria for the emergency lighting and fuel handling systems. Based on the discussion in sections M1.6 of this report, this issue is closed.
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V. Management Meetings
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Xi Exit Meeting Summary The inspectors discussed the progress of the inspection with licensee representatives on a daily basis and presented the inspection results to members of licensee management at the conclusion of the inspection on July 9,1998. The licensee acknowledged the findings presented.
l-The inspectors asked the licensee whether any materials examined during the inspection should be considered proprietary; none was identified.
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PARTIAL LIST OF PERSONS CONTACTED l
Licenseg E. Campbell, Maintenance Manager R. Colgiazier, NRC Coordinator i-G. Frantz-Outage Coordinator K. Graesser, Byron Site Vice President J. Harkness, Site Maintenance Rule Owner W. Israel, Assessment Manager l
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A. Javorik, Chief, Corporate Systems / Component Engineering H. Kats, System Engineering B. Kouba, Sitn Engineering Manager J. Langan, Performance Monitoring Group Lead M. Melnicoff, Corporate Risk Management Engineer T. Schuster, Nuclear Oversight Manager M. Strait, Corporate Maintenance Rule Coordinator J. VanLaere, System Engineering Supervisor i
W. Walter, Operating Engineer j
D. Wozniak, Acting Station Manager LIST OF INSPECTION PROCEDURES USED IP 62706:
Maintenance Rule IP 40500:
Effectiveness of Licensee Controls in identifying, Resolving, and Preventing Problems LIST OF ITEMS CLOSED 50-454/455/97004-01(DRS) IFl Risk Significance of Ventilation Systems 50-454/455/97004-02(DRS) IFl Periodic Assessment 50-454/455/97004-03(DRS) VIO Reliability Performance Criteria l
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l UST OF ACRONYMS USED
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Core Damage Frequency Comed Commonwealth Edison Company.
DG Diesel Generator DRS Division of Reactor Safety ELU Electric Lighting Unit-EPRI Electric Power Research Institute FF Functional Failure
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MEER Miscellaneous Electrical Equipment Room MR Maintenance Rule
.NUMARC Nuclear Management Resource Council l
ORAM On-line Risk Assessment Monitor PM Preventive Maintenance PSA Probabilistic Safety Assessment SSC Structures, Systems or Components I
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LIST OF DOCUMENTS REVIEWED BVP 800-37," Maintenance Rule implementation and Compliance Program," Revision 6, May 28,1998 BVP 800-37A2, " Maintenance Rule Performance Criteria," Revision 6, May 28,1998 BVP 800-37T2, " Determination of Risk Significance," for VC, VD, and VX Systems, Revision 1 BAP 1750-6, " Shutdown Risk Program Sumniary," Revision 3, September 26,1997 BAR 0-31-A4,"Aisnunciator Response for MEER/SWGR Room Temp High," Revision 2 October 5,1993
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BOP VD-6," Emergency Restoration of the DG Room Ventilation System," Revision 1,
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November 12 1997 BOP VC-15, " Alternate Methods of Cooling the Aux Electric Equipment Room," Revision 3, I
January 12,1998 Byron Outage Guidelines System Status Sheets (SRMG-BOG, Revision 1, November 11,1997)
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NSP-ER-3011," Maintenance Rule Periodic Effectiveness Assessments," Revision 0, March 3, 1998 NSP-WC-3006, "On-Line Maintenance," Revision 0, May 15,1998 i
Maintenance Rule Periodic Assessment, January 1996 - June 1997, March 2,1998 l
Letter Byron 97-0168, Response to Notice of Violation Inspection Report No. 50-454/97004;
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50-455/97004, July 14,1997 NODCA 98-015GM, Corporate Assessment of Byron Maintenance Rule implementation, March 16-20,1998 Calculation No. BYR97-372 R3,"PSA Basis for Byron's Maintenance Rule Performance Criteria," Revision 2, September 30,1997, and Revision 3, July 6,1998 Calculation No. ATD-0072," Misc Equipment Rooms Temperature Transient Following HELB in Turbine Building on Elev 451 ft," Revision 0.
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