ML20128F140
| ML20128F140 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 02/04/1993 |
| From: | Beck G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9302110266 | |
| Download: ML20128F140 (5) | |
Text
a PIIILADELPIIIA FLECTRIC COMI%NY NUCLEAR GROUP HEADQUARTERS 955-65 CilESTERBPsOOK BLVD.
WAYNE, PA 19087 5691 (215) 680 4 000 -
February 4, 1993 NUCLEAR SERVICES DEPARTMENT Docket Nos. 50-352 50-353 License Nos. NPF-39 NPF-85_
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Limerick Generating Station, Units 1 and 2 NRC Combined Inspection Report Nos. 50-352/92-81 and 50-353/92-81; Schedule for Resolution of Unresolved Items Gentlemen:
.NRC Combined Inspection Report _ Nos. _50-352/92-81 and 50-353/92-81, dated December 4, 1992. described.six (6) Unresolved Items'- that were identified during the Electrical Distribution SysLam Functional Inspection (EJSFI) ~onducted between August 31, 1992 and October 2,
1992 at Limerick Generating Station (LGS),
Units.1 and 2, and Philadelphia Electric Company's (PECo's) Nuclear Group Headquarters.
This-Report requested that PECo provide a schedule' for resolution of the Unresolved Items within 60 days from-the date of' receipt of-the Report.
PECo received the Report on December 8,
1992.
The attachment to. this letter - provides _ a description of ' the Unresolved. Items along with a schedule for
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resolution of each item.
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U.S. Nuclear. Regulatory Commission February 4, 1993 Document Contro.1 Desk Page 2 If you have any questions or require additional information, please contact us.
Very truly yours,
,dA)
G. J.' Beck, Manager Licensing Section Attachment cc:
T. T.
Martin, Administrator, Region 1, USNRC T.
J. Kenny, USNRC Senior Resident Inspector, LGS a
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Attachment-Papo 1 of 3-RESPONSE TO-NRC INSPECTION REPORT NOS. 50-352/92-81 AND 50-353/92 SCHEDULE FOR RESOLUTION OF UNRESOLVED ITEMS
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k Unresolved Item No. 92-81-05 The NRC team noted that, under worst-case accident vonditions, the safeguard transformers would be overloaded by about 1-MVA-in excess of their maximum rating of.14 MVA, and that the transformers associated with load centers 10B201 and 10B202, rated at 1000 KVA, could be overloaded up to 1034 and 1079 KVA, respectively, based on calculated loading.
Although.the calculated overloads were small, it was not clear ' how long they would persist.
In addition, operating instructions had not been established to ensure that the.
load carrying capability of the transformers was not exceeded.
This item is unresolved pending the establishment of approoriate load contrcis to prevent degradation of the transformers.
Schedule As indicated in the Inspection Report, we consider. that i
transformers can be overloaded for short periods of time based on the guidance provided in ANSI Standard C57.96, " Guide for. Loading Dry-Type Distribution and Power Transformers."
In addition, the.
cited transformer overloading is based on the more conservative calculated loading rather than actual loading under worst-case :
accident conditions. Regardless, the need for appropriate controls to prevent overloading of the transformers will be detormined by June 30, 1993 and implemented as required.
Unrestolved Item No. 92-81-06 As part of PECo's' self-assessment. program, a-study is in 1
progress to verify the adequacy of the.120Vac Class lE circuits.
i Based on a preliminary analysi.s performed during the inspection-period, the voltage available at some of the sampled circuits under -
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dearaded voltage. conditions appeared marginal.. The acceptability.
of the voltage at the safety related 120Vac components is unresolved pending completion of the licensee's. study.
-Schedule The 120Vac circuit study to confirm acceptable -voltage at.
safety related components will be completed by December 31, 1993.,
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Unresolved Item No. 92-81-07_
While. reviewing the control'circuito of 4kV. breakers, the NRC team observed that tb closing, tripping, and control circuits were rentactad by a single-35A. fuse.
A fault-at the'end of a control cable might-not generate a-fault current high enough'to be cleared l
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Response to NRC Inspection Report Attachment Nos. 50-352/92-81 and 50-353/92-81 Page 2 of 3 by the 35A fuse.
In this case, an undetected fault could cause-damage to surrounding cables and prevent other equipment from performiog their function.
Therefore, the acceptability of 35A fuses in control circuits is unresolved pending a
detailed evaluation by the licensee.
Schedule An evaluation of the acceptability of the 35A fuses in control-circuits will be completed by May 31, 1993.
Unresolved Item No. 92-81-08 During the inspection, the NRC team noted that there are non-safety related loads (i.e.,
the drywell chillers and control rod drive pumps) connected to safety related buses.
These loads are shed from their respectivo buses during a loss of coolant accident (LOCA).
Power to the control circuits comes, in part, from non-safety related motor control centers that are re-energized a few minutes into the event via operator action.
The NRC team noted that a f ailure of the non-safety related components could cause the j
loads to be applied to the safety related buses in an uncontrolled manner.
Such occurrence could result in the overloading of the affected buses.
This issue is unresolved pending the licensee's detailed evaluation of the circuits and administrative controls involved to ensure that the emergency buses.are not inadvertently overloaded.
Schedule An evaluation of the existing circuits and administrativ9 controls to ensure that the emergency buses are not inadvertently overloaded will be completed by April 30, 1993.
Unresolved Item No. 92-81-09 The NRC team raview of the Residual Heat Removal (RHR) and Core Spray (CS) pump curves revealed some unusual characteristics.
Discussions with the pump vendor resolved the initial concerns; however, the pump vondor indicated that the pump horsepower is sensitive to the back pressure at the outlet of the pump.
The licensee noted that they were not aware of the need to maintain 9
some minimum back pressure on the pumps.
The need for and acceptability of a minimum back pressure is unresolved pending the-licensee's evaluation.
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Schedule An avaluation of the acceptability of cuirent configuration and system or.erations alignments as they relate to a min!. mum back pressure on the RHR and CS pumps 3 will be completed by Apri) 30, 1993.
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, Response to NRC Inspection Report Attachment Nos. 50-352/92-81 and 50-353/92-81 Page 3 of 3
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tlnresolved Item No. 92-81-10 The NRC team reviewed the results of a surveillance test regarding undervoltage and time delay relays associated with an emergency bus.
The acceptance critoria is based on the actuation I
time delay of the combined relays. The test results indicated that the as-found total time delay exceeded the acceptable limit.
The combined time delay was brought within the acceptable limit by adjusting the setting of the undervoltage relay (i.e., the voltage setpoint) rather than the setting of the time delay relay.
Currently, the surveillance test procedure does not have provisions to measure the individual response times of the undervoltage relay and the time delay relay.
This item is unresolved pending the NRC's review of the licensee's evaluation to determine: 1) the cause of the deficiency, and 2) whether the procedure should be
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revised to avoid similar problems in the future.
Schedule An evaluation to determine: 1) if the cited practice has any potential negative consequences of significence, and 2) whether the procedure should be revised to provide specific guidance for how to reset the combined relay time delay to meet acceptance criteria, will be completed and available for review by May 31, 1993.
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