ML20073S896
| ML20073S896 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 06/28/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073S892 | List: |
| References | |
| GL-91-04, GL-91-4, NUDOCS 9407070179 | |
| Download: ML20073S896 (9) | |
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A UNITED STATES 3
NUCLEAR REGULATORY COMMISSION E
f WASHINGTON, D.C. 20pH001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMEl'DMENT NOS. 71 AND 34 TO FACILITY OPERAT*NG LICENSE N05. NPF-39 AND NPF-85 PHILADELPHIA ELECTRIC COMPANY LIMERICK GENERATING STATION. UNITS 1 AND 2 DOCKET NOS. 50-352 AND 50-353
1.0 INTRODUCTION
By letters dated September 1, 1992, and October 15, 1992, as supplemented by letters dated October 30, 1992, March 16, 1993, June 10, 1993, July 28, 1993, September 10, 1993, April 29, 1994, June 2, 1994, June 9, 1994, and June.15, 1994, the Philadelphia Electric Company (PEco, the licensee) submitted a request for changes to the Limerick Generating Station (LGS), Units 1 and 2 Technical Specifications (TS).
The September 1,1992 submittal addresses the proposed changes to the TS surveillance intervals for the non-instrumentation TS line items ( e.g., pump, valve, and flow testing, logic system functional testing, and response time testing).
The October 15, 1992, submittal addresses the proposed changes to the TS surveillance intervals for the instrument calibration and other remaining TS line items to support the 24-month refueling cycles.
The supplemental letters provide clarifying information that did not change the initial proposed no significant hazards consideration determination.
Amendments 56 and 21 to Facility Operating Licenses NPF-39 and NPF-85, issued on August 20, 1992, approd revisions to the channel calibration frequency-for the peak acceleration seismic monitoring recorder mounted on the reactor vessel head flange, and for the frequency of the surveillance testing of the main steam safety valves from 18 to-24 months.
The requested changes extend the interval for certain TS surveillance requirements to 24 months with an additional 25-percent grace period.. The 24-month refueling cycle results in changes from the current 18-month'TS surveillance testing interval (i.e., a maximum of 22.5 months accounting for the allowable grace period) to a 24-month testing interval (1.e., a maximum of 30 months accounting for the allowable grace period). -The proposed TS changes were submitted in response to Generic letter Number 91-04, " Changes in Technical Specification Surveillance Intervals to Accommodate a 24-Month fuel Cycle."
Generic lett9r 91-04 provides generic guidance to support the development of TS revisioris to allow a 24-month fuel cycle and includes requirements for the-evaluation of the effects on safety resulting from the increase in surveillance intervals that accommodate a 24-month fuel cycle.
It states that
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__ the evaluation should conclude that the net effect on safety is small, that historical plant maintenance and surveillance data support the proposed extended surveillance interval, and that the assumptions of the plant licensing basis are still bounding with the incorporation of a 24-month surveillance interval.
The licensee has concluded that the assumptions of the plant licensing basis are not impacted by the proposed changes.
The details of the licensee's conclusion and bases and the impact of the proposed changes on system availability and safety are discussed in the evaluation.
The proposed extension of the interval was accomplished for some surveillances by explicitly embedding the term 24 months in the particular line item requirement.
For other surveillances, the proposed extension was accomplished by changing the TS Section 1.0 definition of operating cycle or refueling cycle to a maximum of 731 days. A 25-percent grace period beyond the 731 days is still allowed.
For some surveillances, the licensee stated that it was not possible to demonstrate the acceptability of extending the surveillance 6terval ueyond 18 months, plus the grace period.
For some of these surveillances, the wording of the specific TS has been revised, but the actual surveillance interval (18 months, plus grace period) remains unchanged.
2.0 EVALVATION Improved reactor fuels allow licensees to consider an increase in the duration of the fuel cycle for their facilities.
A longer fuel cycle requires consideration of whether corresponding increases of the timc interval between performance of TS surveillance requirements can be justified.
GL 91-04 provides generic guidance to support the development of TS revisions to allow 24-month surveillance intervals and includes requirements to evaluate the impact on safety for an increased surveillance interval.
The licensee evaluation has concluded that the net effect on safety is small, that historical plant maintenance and surveillance data support the proposed extended surveillance interval, and that the assumptions of the plant licensing basis a'e still bounding with the incorporation of a 24-month surveillance interval.
2.1 INSTRUMENTATION in order for a licensee to use the provisions of GL 91-04, the staff has required the licensee to address the issue of instrumentation errors /setpoint methodology assumptions when proposing an extended instrumentation surveillance interval.
Specifically, the licensee must evaluate the effects of an increased calibration interval on instrument uncertainties, equipment qualification, and vendor maintenance requirements to ensure that an extended surveillance interval does not result in exceeding the assumptions stated in the safety analysis.
GL 91-04 allows for either vendor drift data or plant-specific drift data to be utilized in determining a 24- (30- with grace period) month instrument
3-drift term.
Vendor information and/or licensee operating experience can i
provide sufficient data to evaluate long-term instrument performance to support an extended surveillance interval of 24 months. The basis for the extended vendor drift term should reflect a compatible setpoint methodology to that used in the plant setpoint methodology.
Additionally, GL 91-04 requires a plant-specific program to monitor and assess the long-term effects of instrument drift and provide continuing data to evaluate extended 24-month instrumentation surveillance intervals.
GL 91-04 required licensees to address a number of issues to justify an increase in calibration interval for instruments that perform a safety function. The licensee addressed the GL 91-04 issues in its evaluation of instrument performance.
The licensee evaluated plant-specific surveillance drift data to determine instrument drift over a 24-month fuel cycle.
The licensee stated that the impact of extended surveillance intervals on system availability is small in that the failures detected by the 18-month surveillance are less than one percent. The licensee reviewed applicable surveillance test results and evaluated the historical as-left and as-found drift information.
The raaintenance and surveillance test evaluations confirmed that instrument drift has not exceeded the allowable limits except on rare occasions.
Vendor maintenance requirements have been reviewed by the licensee and found to be compatible with a 24-month surveillance interval.
The drift analysis employed by the licensee to determine the acceptability of a 24-month surveillance interval is based on the drift analysis module identified in NEDC-31336, "GE Instrument Setpoint Methodology." The GE setpoint methodology is a generic methodology that, in general, requires plant-specific calculations with plant-specific data.
1he staff approved NEDC-31336 by Safety Evaluation Report (SER) dated February 9,1993, and noted the use of independent, random and normally distributed data but expressed concern with the use of only a single sided confidence interval distribution with an undefined confidence level.
The staff also expressed concern that the difference between the Allowable Value and Nominal Trip Setpoint included drift-terms besides those checked during the monthly setpoint surveillance test. The staff accepted the-GE drift term methodology within the limitations outlined in the SER. The_GE report i
i demonstrated that drift for the instruments included in the topical report l
were normally distributed. However, the staff did not accept the assum) tion i
that. drift is inherently random and normally distributed and agreed witi GE-that each instrument shotld be confirmed to have random drift terms by-empirical and field data.
Finally, the use of a single sided test for instrument drift terms for trips or indication / recorders related to increasing or decreasing variables _was found to be unacceptable by the staff.
In addition, the staff believes it is good engineering practice to employ data with a two sided, 95 percent confidence _ interval with a 95 percent confidence
- level (95/95).
Subsequent to NEDC-31336, GE developed a computer model, " Instrument Trending-Analysis System (GEITAS)," based on the drift determination methodology
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The GE-developed instrument trending system includes the as-left and as-found drift data for numerous GE Boiling Water Reactor (BWR) instruments.
GEITAS was the methodology chosen by the licensee to project a 30-month drift value for the Limerick Generating Station instrumentation.
In general, the licensee elected to use plant-specific surveillance drif t data for the GEllAS analysis. The GE drift analysis methodology has been previously reviewed by the staff (NEDC-31366A).
The sof tware for GEITAS was developed under a GE quality assurance program.
previously reviewed by the staff as documented in NED0-ll209-04, Revision 8, "GE Nuclear Energy Quality Assurance Program Description," for safety-related software.
The drift data as analyzed by the GE methodology software program compensates for the additional error terms normally associated with the as-found and as-left values (instrument accuracy, measurement and test equipment and temperature effects).
The licensee chose not to compensate for the additional errors during the analysis of the Limerick Generating Station specific drift data (temperature and calibration errors).
These additional error terms assumed by the licensee in the as-lef t and as-found data are consistent rith industry practice.
As a result, the 30-month drift terms calculated by the licensee may have additional con;ervatism with respect to the actual drift term. The drift term results were derived from plant-specific drift data, and therefore, satisfy the requirements of GL 91-04.
In situations where instrumentation was recently installed, or a limited number of data points were available, or vendor 30-month drif t data was available, the licensee chose not to utilize the GE drif t analysis methodology.
For these cases the licensee provided a specific evaluation to justify the change.
Although GL 91-04 allows the use of vendor drift terms in the development of extended surveillance intervals the licensee should confirm that the published vendor drift satisfies the existing setpoint calculation criteria (normally 95-95, normal / random distribution, sufficient number of data points, surveillance interval, and vendor methodology is compatible with the licensee setpoint methodology requirements).
Additionally, the vendor drift values must be verified by subsequent plant as-lef t and as-found data as required by GL 91-04 trending requirements. The licensee stated that the vendor drift terms were compatible with the present setpoint methodology used by the licensee.
The licensee determined the magnitude of instrument drift and identified the channels and TS sections affected.
The 30-month drift term was crmpared to the procedure drift allowance for each instrument application.
T,ie licensee stated that if the 30-month instrument drift term was not bounded by the existing drift allowance then the surveillance interval was set at 18 mcnths.
Any extension of the above surveillances' calibration interval was based on additional justification.
The licensee stated that in no case was the setpoint of an instrument revised to accommodate a drift error larger than previously analyzed.
The licensee confirmed that the projected instrument
__ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ drift is bounded by the design basis instrument drift calculations.
The safe shutdown analysis /TS (setpoint related) did not require revision to accommodate a 24-month calibration cycle.
GL 91-04 requires that the licensee verify that any revised setpoint or safety analysis is reflected in procedure acceptance criteria for channel checks, channel functional tests, and channel calibrations.
Item 6 of GL 91-04 requires that plant procedures for the affected instrumentation be reviewed and verified to reflect the requirements of the setpoint methodology and safety analysis.
The licensee stated that plant procedure acceptance criteria was evaluated and found to meet the requirements of the setpoint calculations and safety analysis.
The licensee established a program for monitoring and assessing the effects of increased calibration intervals on instrument drift.
The purpose of this monitoring program is to provide a means to verify the assumptions made in the-setpoint methodology with regards to instrument drift.
The monitoring program a o provides a method to determine the adequacy of a specific surveillance interval.
The licensees drift trending program commits to evaluate any calibration surveillance that f ails to meet the specified procedure drift allowance for that instrument.
Based on the above, the licensees monitoring program meets the requirements of GL 91-04 for the proposed amendment and is, therefore, acceptable to the staff.
The following paragraphs in this section discuss instrumentation issues that warranted plant-specific treatment:
The licensee evaluated the drift for the main turbine control valve electro-hydraulic control pressure switch and determined that the instruments experienced significant drift.
The drift exceeded the current allowable drift as specified by GE and the more conservative value currently used by Limerick Generating Station for End-of-Cycle Recirculation Pump Trip (E0C RPT).
The licensee reviewed the accident analysis and considered the potential impact of the observed drift, The licensee concluded that drift in the non-conservative direction would impact the response time of the reactor scram and EOC-RPT signal.
The licensee stated that a worst-case drift of 200 psi had minimal impact on the response time (3 milliseconds) and will still be within the historical response times noted for RPS and E0C-RPT, Additionally, modifications were performed by the licensee on the electro-hydraulic control (EHC) system to eliminate pressure oscillations and l
vibration of the EHC piping.
The results of the calibration surveillance showed that instrument drift was within the procedure drift allowance.
The licensee stated that the EHC system vibrations and pressure oscillations contributed to the excessive drift experienced by the EHC pressure instrumentation.
Based on the above licensee evaluation, the staff concluded that the present 18-month calibration interval can be extended to 24-months for the main turbine control value electro-hydraulic pressure switch.
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_ The licensee proposed to extend the surveillance interval for the following steam leak detection loops: TF Table 4.3.2.1-1, Items 1.f, l.g, 3.b. 3.c, 4.d, 4.e, 4. f, 5.d. 5.e and 5. f.
The original steam leak detection equipment has been replaced with GE NUMAC equipment.
The NUMAC instrumentation has insufficient plant-specific drift data to evaluate and project a 30-month drift term.
Based on information listed in Topical Report NED0-30883 (CER dated September 16,1986), both the instrument drift and the accuracy of the GE NUMAC equipment are improved with respect to the original INMAC equipment.
The licensee consulted with the vendor who confirmed that a 24-month surveillance interval for the newly installed NUMAC steam leak dettetion equipment is acceptable. However, the 30-month drift term supplied by the vendor does not include the sensors.
The licensee stated that the sensors (thermocouples) exhibit minimal drift and, therefore, the vendor supplied 30 month drift term is representative of the total drift expected for this instrumentation and is within the procedure drift allowance.
Based on the data supplied by the licensee, the staff finds the proposed 24-month surveillance interval acceptable.
The licensee elected to maintait the surveillance interval for TS Table 4.3.3.1-1, item 3.d, " Suppression Pool Water level - High" at the current 18-month interval.
The calibration interval designation will be revised to read "E".
The "E" designation will be defined in Table 1.1,
" Surveillance frequency Notation," as "At least once-per-18-months (550) days." This is an administrative change and is, therefore, acceptable to the staff.
For Limerick Generating Station, Unit 2, the licensee evaluated the surveillance tests for TS Table 4.3.3.1-1 pressure switches.
The number of data points were insufficient to determine a 30-month drift term.
Additionally, the licensee stated that based on the existing data the switches do not operate satisfactorily over a 24-month surveillance interval (30 months with grace period).
The licensee has replaced these pressure switches with switches that demonstrate acceptable drift over the proposed 24-month surveillance interval.
The replacement of the above switches, with switches shown to exhibit acceptable drift over the proposed 24-month calibration surveillance interval, is acceptable to the staff.
The seismic monitoring instrumentation TS Table 4.3.7.2-1. Items 1.a.
I through 6, 1.b. I through 5, 1.c.1, and 3.a. did not have adequate surveillan:e test data to satisfy the requirements of the GE setpoint methodology for a 30-month drift term. The licensee consulted with the manufacturer on the acceptability of a 24-month surveillance interval.
The manufacturer stated that a 24-month surveillance interval (30 with grace) is acceptable.
Based on the above, the staff finds the proposed 24-month surveillance interval acceptable for the above referenced seismic monitoring equipment.
The surveillance test results for the RCIC low pressure bearing oil temperature instrumentation, TS Table 4.3.7.10.c, item 18, shows that no calibration adjustments were required for 42 and 23 months for Units 1 and 2, 4m
- respectively.
Although there is not sufficient drift data to satisfy the GE setpoint program, the licensee concluded that in conjunction with the monthly functional test the available data supports extending the surveillance interval for this instrumentation to 24 months.
The proposed 24-month surveillance interval for the RCIC low pressure bearing oil temperature is acceptable to the staff.
The GE NUMAC instrumentation has replaced existing radiation monitoring instrumentation associated with TS Table 4.3.1.1-1, Item 6, and TS Table 4.3.2.1-1, item 1,b.
The NUMAC instrumentation does not have sufficient historical drift data to satisfy the GE setpoint methodology.
The licensee requested that the manufacturer evaluate the impact of a 24-month surveillance interval for this instrumentation.
The manufacturer stated that a 24-month surveillance interval is acceptable for the NUMAC instrumentation.
Based on the manufacturer's evaluation and information provided by the licensee, the 3
staff finds the proposed 04-month calibration interval acceptable.
The existing radiation recorders for Units 1 and 2 refueling area ventilation exhaust duct radiation monitors (TS Table 4.i.2.1-1, items 7.c.) and 7.c.2) are to be replaced with recorders that will tupport a 24-month surveillance interval and bound the existing drift surveillance allowan;es.
Based on the licensee replacement of the present recorders with instruments that satisfy the 30-month surveillance allowance, the staff finds the proposed 24-month surveillance interval acceptable.
The main turbine control valve (HTCV) EHC system pressure switches were evaluated for drift using the GE drift program. The licensee's evaluation determined that this instrumentation experienced significant drift.
Closure of the turbine control valves can result in a significant addition of positive reactivity and pressure increase.
The turbine stop valve fast closure scram initiates an anticipatory scram and end-of-cycle recirculation pumr trip (E0C-RPT).
The licensee reviewed the impact of drift in the non-conservative direction i
and determined that the impact would be an increase in the response time of the reactor scram signal and EOC-RPT.
The additional _ increase in response time (3 milliseconds) will be added to the overall response time of the~ trip by the licensee. The licensee noted that the increased response time is well within the observed margin and within the response time requirements stated in the TS.
The licensee has performed modifications-on the EHC system to alleviate the drift experienced with:the MTCV pressure switches.
The limited operating experience to date has shown that the observed drift is within the surveillance test acceptance values.
The licensee concluded that the 4
surveillance interval for the above instrumentation can be increased to 24 months.
Based on the evaluation presented by the licensee, the proposed 24-month surveillance is acceptable to the staff.
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i 1 2.f ELECTRICAL POWER SYSTEMS Based on review of the information contained in licensee's submittals, the staff finds that the proposed revisions to the electrical power systems TS SR Sections 4.8.1.1.1.b 4.8.1.1.2.e, 4.8.2.1.c, 4.8.2.1.d 4.8.2.1.f.
4.8.4.1.a.1, 4.8.4.1.a.2, and 4.8.4.2.2 only revise the frequency of surveillance testing for certain equipment items.
These sections increase the time interval between surveillance testing and this time interval increase has a small impact on system availability.
Further, the licensee has documented that their review of surveillance testing history demonstrated there is no evidence of any failures which would invalidate this conclusion.
In addition, the licensee has committed to propose othte changes for TS SR Section 4.8.2.1.e regarding battery performance div.harge testing.
These changes are to reflect the modified performance dischaiy testing described in the 1993 draft revision of IEEE Standard 450. TS SR 3.ction 4.8.2.1.f that addresses the frequency of performance discharge testing of degraded batteries or batteries that have reached a certain percentage of expected service life may be revised pending future licensee evaluation of the existing SR in conjunction with possible future changes to the 1993 draft revision of IEEE Standard 450.
The staff finds the commitments for these areas acceptable. On the bases of the above, the staff concludes that the licensee's proposed TS SR revisions are consistent with Generic Letter 91-04, are technically adequate, and are acceptable.
2.3 OTHER TS LINE ITEM!i Finally, the licensee has evaluated the effect of the increase in the surveillance intervals on safety for the other 18-month surveillances and has concluded that the effect is small. The licensen has confirmed that historical plant maintenance and surveilltaco dats do not invalidate this conclusion.
The licensee also confirmed that the increase in surveillance intervals to accommodate a 24-month fuel cycle does not invalidate any assumption in the plant licensing basis. The staff reviewed this information and finds that the proposeo TS changes do not have a significant effect on safety and are, therefere, acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change the surveillance requirements.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released l
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sffsite, *nd that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (57 FR 42778 and 57 FR 48823). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR Sl.22(c)(9).
Pursuant to 10 CFR Sl.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issu;nce of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conde,ted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public, Principal Contributors:
F. Rinaldi, PDI-2 S. Dembek, PDI-2 C. Doutt, HICB D. Nguyen, EEL 8 F. Ashe, EELB Date: June 28, 1994
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