ML20202J370

Responds to IE Bulletin 86-001, Min Flow Logic Problems That Could Disable RHR Pumps. Single Failure Condition Does Not Exist at Unit

ML20202J370
Person / Time
Site:	Limerick
Issue date:	06/09/1986
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
IEB-86-001, IEB-86-1, NUDOCS 8607170067
Download: ML20202J370 (5)

Text

9 Po PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 (21s) e41 so2o

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Docket No. 50-352 Dr. T. E. Murley, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406

Subject:

Response to IE Bulletin 86-01:

(Minimum Flow Logic Problems that Could Disable RHR Pumps), Dated May 23, 1986 Limerick Generating Station Unit 1

Dear Dr. Murley:

The purpose of this letter is to provide the Philadelphia Electric Company (PECo) response to IE Bulletin 86-01 for Limerick Generating Station Unit 1. The bulletin discussed a situation at an operating nuclear power plant in which a single failure occurring under certain accident sequences could result in all Residual Heat Removal (RHR) system minimum flow bypass valves being signaled to close while all other pump discharge valves are also closed. The postulated single failure involves loss of a flow sensing instrument. As indicated in the bulletin, this condition could result in no flow through the RHR pumps and could lead to the pumps running dead headed with potential for pump damage in a few minutes. The actions required by the bulletin are restated belcw followed by our response:

1. Promptly determine whether or not your facility has this single failure vulnerability.

2. If the problem exists, immediately instruct all operating shifts of the problem and measures to recognize and mitigate the problem.

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• Dr. T. E. Murley June 9, 1986 Page 2

3. Within 7 days of receipt of this bulletin, provide (a) a written report to the NRC which identifies whether or not this problem exists at your facility,.(b) if the problem exists, identify the short-term modifications to plant operating

procedures or hardware that have been or are being i implemented to assure safe plant operations.

!' 4. If the problem exists, provide a written report within 30 days of receipt of this bulletin informing the NRC of the schedule for long-term j resolution of problems that are identified as a result of this bulletin.

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! Response PECo has reviewed the RHR minimum flow logic for Limerick Generating Station Unit 1 and has determined that the single failure condition discussed in IE Bulletin 86-01 does not exist at the unit. The RHR system is comprised of four independent and redundant electrical safeguard j divisions. There are four RHR pumps; each pump has an 1 associated flow sensing loop installed in the pump discharge j- line and an associated minimum flow return line to the suppression pool. Each flow sensing loop consists of a flow ,

j element, flow transmitter and flow indicating switch. A t

normally closed motor operated shutoff valve is provided in

. each minimum flow return line. Attachment 1 provides a list j of the subject pumps, valves, and flow sensing

! instrumentation.

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! When a RHR pump is opet4 ting, the associated flow i sensing loop installed in the pump discharge line initiates automatic opening of the shutoff valve in the associated minimum flow return line if adequate flow is not sensed in the pump discharge line. When adequate flow is established, the flow sensing loop initiates automatic closure of the shutoff valve. Each flow sensing loop controls only the shutoff valve associated with that RHR pump and flow sensing j loop.

1 Each RHR pump, associated flow sensing instrumentation, and associated minimum flow return line and

, shutoff valve is assigned to a separate electrical safeguard division. Consequently, each pump, associated flow sensing l instrumentation, and minimum flow return line and shutoff l valve is independent from, separated from, and redundant to 4

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t Dr. T. E. MurlCy June 9, 1986 Page 3 each of the other pumps and associated equipment. The single failure of a flow sensing element could result in the loss of only the associated RHR pump. The three remaining RHR pumps will not be affected.

The RHR minimum flow logic problem identified in IE Bulletin 86-01 does not exist at Limerick Generating Station Unit 1. No long-term modifications to plant operating procedures or hardware are required.

Should you have any questions, or require additional information, please do not hesitate to contact us.

Very truly yours,

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Attachment cc: E. M. Kelly, Senior Resident Site Inspector Document Control Desk I

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COMMONWEALT!! OF PENilSYLVA!!IA :

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COUNTY OP PilILADELPilIA  :

M. J.-Cooney, being first duly sworn, deposes and says:

That he is Manager-Nuclear Production, of Philadelphia Electric Company, the Applicant herein; that he has read the foregoing response to I.E. Bulletin No. 86-01 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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d Subscribed and sworn to t before me this Y day of IveC. 1986.

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Notary Public JUDITH Y. PptANNUN g Notary Public. Phila., Phila. Co.

My Commission Expires July 28.1987 4

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f. ATTACHMENT 1 Bulletin 86-01 Recoonce June 9, 1986 Doc'<et No. 50-35 2 RHR PUMP MINIMrN FLOW DROTECTION LIMERIC5C GENERATING SftTION UNIT 1 RHR Pump Minimum Flow Valve Control Device 14P202 HV-1F0074 FE-lN014A FT-1N052A FISL-IN6524 IBP202 HV-1F0078 FE-1N014B FT-lN052B FISL-IN652B ICP202 HV-1F007C FE-lN014C FT-1N052C FISL-IN652C 10P202 HV-lF007D PE-1N014D FT-1N052D FISL-IN652D 1