ML20117G063
| ML20117G063 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 08/29/1996 |
| From: | Walter MacFarland PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9609050009 | |
| Download: ML20117G063 (5) | |
Text
W:lttr G. MicFarfind, IV, P.E.
Vce President Limenck Generating Station PECO NUCLEAR mme-c-en<
PO Box 2300 A UNIT or l'fCO f wcy Sanatoga, PA 19464-0920 610 718 3000 Fax 010 718 3008 Pager 1800 672 2285 #8320 August 29,1996 Docket Nos. 50-352 50 353 License Nos. NPF 39 NPF 85 1
U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
Limerick Generating Station, Units 1 and 2 Response to An Apparent Violation NRC Integrated Inspection Report 50-352/96 04 and 50-353/96 04 This letter provides PECO Energy's response to an apparent violation for Limerick Generating Station (LGS), Units 1 and 2, that was contained in your letter dated July 30,1996, which forwarded the subject NRC Inspection Report. The apparent violation concerns inadegaate foreign material exclusion (FME) controls for the Unit 1 suppression pool such that the 1 A Residual Heat Removal (RHR) system pump experienced suction strainer fouling while running in the suppression pool cooling mode in response to a main steam line safety relief valve (SRV) inadvertent opening event in September,1995. The details of this event are described in NRC SpecialInspection Report 50-352/95-81 and 50 353/95-81 for LGS, Units 1 and 2, dated October 31,1995.
The reason for the apparent violation, the immediate corrective steps taken, and the corrective steps taken to avoid further violations are described in the following previously docketed correspondence:
NRC SpecialInspection Report 50-352/95 81 and 50-353195 81 dated October 31,1995, PECO Energy letter dated October 6,199, which provided the LGS " Main Steam Safety l
Relief Valve / Emergency Core Cooling System Action Plan" developed in response to the l
September 1995 event, PECO Energy response dated November 16,1995, to NRC Bulletin 95-02, " Unexpected Clogging of a Residual Heat Remeval (RHR) Pump strainer While Operating in Suppression Pool Cooling Mode,"
l 9609050009 960829 l- }lN f' PDR ADOCK 05000352 t
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Docket Nos. 50-352 and 50-353 i
August 29,1996 Page 2 i
PECO Energy letter dated March 1,1998, which provided a revised action plan in response to a Request for AdditionalInformation (RAl) from the NRC dated January 31,1996, i
PECO Energy response dated June 10,1996, to NRC RAI dated May 9,1996, concerning NRC Bulletin 95-02, and NRC Integrated Inspection Report 50 352/96-04 and 50 353/96 04 dated July 30,1996.
Compliance was achieved by September 23,1995, when enhanced suppression pool FME controls were implemented, and suppression pool cleanup activities, including cleanup of the Emergency Core Cooling Systems (ECCS) suction strainers and suppression pool cleanliness acceptance testing, were complete.
Although the fouling of the Unit 1 A RHR pump suction strainer was identified through the September,1995 event, the inadequacy of the FME controls noted in the subject NRC inspection report was identified by PECO Energy through a comprehensive and exhaustive root cause investigation performed in response to the event. This investigation was conducted over a one month period following the event. The investigation was performed by a multi-discipline review team, including individuals who were directly involved with the event, and others who were completely independent. The scope of the investigation extended back to 1985, to capture the first applicable industry operating experience, and ended with immediate corrective actions taken after the September 11,1995 event. Formal event and causal factors charting techniques were employed as part of the investigation. Industry operating experience, regulatory documentation, and station documentation concerning containment cleanliness, suppression pool liner issues, and ECCS suction strainer problems were researched during the review. This information included: NRC Generic Letters, Information Notices, and Bulletins; institute Of Nuclear Power Operations (INPO) Operating Experience documentation; and Boiling Water Reactor Owner's Group (BWROG) documentation. The investigation included a review of LGS responses to this industry and regulatory information.
Interviews with key individuals were also performed. As a result of this extensive investigation,15 potential generic implications were identified and extensive corrective actions were implemented which helped to set the industry standard for responding to this issue.
Prior to the September 11,1995 event, neither LGS unit had experienced any indicated problems related to clogging of ECCS suction strainers. ECCS pump suction pressure was previously monitored during quarterly pump, valve and flow testing; however, trending of this data led to the conclusion that strainer clogging was not occurring in either unit. LGS review of industry experience prior to the event focused on the specific issues identified in various industry and regulatory documents, and determined such issues were either already addressed or they were not applicable to LGS. During the specialinspection following the September 1995 event, the NRC reviewed LGS responses to the above referenced NRC Bulletin 93-02 and its supplement, and determined, as indicated in NRC SpecialInspection Report 50-352/95 81 and 50-353/95-81, that the responses were adequate. During the same inspection, the NRC evaluated the LGS training materials used for informing the operators and other appropriate plant personnel about the issues related to the
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i Docket Nos. 50-352 and 50-353 August 29,1996 Page 3 potential clogging of ECCS strainers, including indications of strainer clogging, and determined that they were adequate as indicated in the inspection report. The adequacy of the operator training relative to recognizing potential clogging of an ECCS pump suction strainer was confirmed by Operations personnel response during the September 1995 event.
Considering the ongoing industry and NRC efforts to resolve the generic Boiling Water Reactor (BWR)
ECCS strainer clogging issue, l.GS planned to clean the suppression pool and ECCS suction strainers of both units during the next available refueling outage for each unit, although no such commitment was made in response to NRC Bulletin 93-02 or its supplement. LGS belief at the time, consistent with the focus of the industry and the NRC, was that the fibrous material of concern was drywell insulation destroyed in a loss of Coolant Accident (LOCA) and transported to the suppression pool, and not a preexisting condition in the pool. The cleaning schedule was based on the assumption that procedural housekeeping and FME controls were adequate, that the suppression pools were clean, and that the material found in the Unit 2 suppression pool was not characteristic of the material of concern in the Bulletin.
The Unit 2 suppression pool was cleaned in February,1995 (Unit I was scheduled to be cleaned in February,1996). During the cleaning process, an extensive amount of foreign material was removed from the suppression pool.
Our internal investigation identified that no evaluation of the Unit 2 inspection results was performed and that the evolution was primarily considered a cleanup activity.
No information was presented to management that would indicate the foreign material was of the magnitude or type discussed in the bulletin or that the material found being in the pool reflected any deficiency in existing FME controls. There was no access to the suppression pool during operation and the two Unit 1 mini-outages in the summer of 1995 were not anticipated. As a result, management did not contemplate rescheduling the Unit 1 suppression pool cleaning to an outage earlier than the next refueling outage. Consequently, it would be inaccurate to describe the mini-outages as missed opportunities to clean the Unit 1 suppression pool.
The corrective actions in response to the apparent violation were prompt and comprehensive. Based on observation of PECO Energy's investigation of the event, NRC SpecialInspection Report 50-352/95-81 and 50-353/95 81 noted that the corrective actions and monitoring activities with respect to suppression pool cleanliness and ECCS operability following the event were excellent. LGS management employed multitasked resolution schemes built on industry state-of the art knowledge and techniques. The corrective actions were aggressive, routinely incorporated quality considerations into the line decision making practices, were based on sound engineering principles and were focused on safety. Nineteen (19) corrective actions were identified and implemented prior to the restart of Unit 1. Sixteen (16) other corrective actions addressing the identified conditions adverse to quality and causal factors were identified, with a majority of the actions scheduled for completion by December 31,1995. Twelve (12) corrective actions addressing the generic implications were
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- i Docket Nos. 50 352 and 50-353 August 29,1996 Page 4 identified, with a majority of these actions also scheduled for completion by December 31,1995.
Based on a followup review of the completed corrective actions, the subject NRC inspection report indicates that adequate corrective actions to minimize the likelihood that debris would enter the suppression pool have been implemented.
If you have any questions or require additionalinformation, please contact us.
Very truly yours, r
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H. J. Miller, Administrator, Region I, USNRC N. S. Perry, USNRC Senior Resident inspector, LGS I
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00MMQNWEALTH OF PENNSYLVANIA i
SS COUNTY OF MONTGOMERY W. G. MacFarland, being first duly sworn, deposes and says:
l That he is a Vice President of PECO Energy Company; that he has read the attached response to an Apparent Violation for Limerick Generating Station, Units 1 and 2, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information and belief.
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Vice President I
6 Subscribed and sworn to before me this 291 day i
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1996.
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Dennis P. Wesley. Notary Ptbre tJme**Twp., Mangamery MyCornmisson Expres Aprt 7,1 7 Meneer, PennsyMrna Assoonbon of Natanes i
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