ML20115H300
| ML20115H300 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/17/1996 |
| From: | Hill W NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, TAC-M93487, NUDOCS 9607230033 | |
| Download: ML20115H300 (6) | |
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NoinaT, States Power Company Monticello Nuclear Generating Plant 2807 West Hwy 75 Monticello, Minnesota 55362-9637 i
July 17,1996 Generic Letter 95-07 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Response to Request for Additional information Concerning Generic Letter 95-07: Pressure Locking and Thermal Bindina of Safetv Related Power-Operated Gate Valves (TAC M93487)
Generic Letter 95-07 (dated August 17,1995) was issued by the NRC requesting licensees to provide information concerning (1) the evaluation of operational configurations of safety-related, power-operated gate valves for susceptibility to pressure locking and thermal binding; and (2) analyses, and needed corrective actions, to ensure that safety-related power-operated gate valves that ate susceptible to pressure locking or thermal binding are capable of j
performing the required safety function.
By letters dated October 16,1995, with subject, " Response to Generic Letter 95-07: Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," and February 12,1996, with subject, "180 Day Response to Generic Letter 95-07: Pressure Locking and j
Thermal Binding of Safety-Related Power-Operated Gate Valves (TAC M93487);" Monticello responded to the Generic Letter.
By letter dated June 18,1996, the NRC staff requested additional information in order to complete its review of the Monticello responses to Generic Letter 95-07. Attachment A to this letter provides the information requested by the staff. This letter contains no new NRC commitments, nor does it modify any prior commitments. Please contact Marv Engen, Sr Licensing Engineer, at (612) 295-1291 if you require further information.
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Williarn J Hill Plant Manager Monticello Nuclear Generating Plant c see next page 7/16/96 NSP HADATA\\NRCCORR\\GL9507RA. DOC 9607230033 960717
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USNRC NORTHERN STATES POWER COMPANY July 17,1996 Page 2 c: Regional Administrator-111, NRC NRR Project Manager, NRC Sr Resident inspector, NRC Stato of Minnesota, Attn: Kris Sanda Attachments: Affidavit to the US Nuclear Regulatory Commission A - Monticello Nuclear Generating Plant, Response to Request for Additional Information Regarding Generic Letter 95-07
UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 Response Dated July 17,1996 to Request for Additional information Conceming Generic Letter 95-07: Pressure Locking and Thermal Bindina of Safetv-Related Power-Ocerated Gate Valves (TAC M33487)
Northem States Power Company, a Minnesota corporation, hereby provides the required 30 day response to NRC letter dated June 18,1996, with subject, " Request for Additional information ' Generic Letter 95-07: Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves,' Monticello Nuclear Generating Plant (TAC No. 93487)". This letter contains no restricted or other defenso information.
NORTHERN STATES POWER COMPANY By /
is G
William J Hi!!'
Plant Manager i
Monticello Nuclear Generating Plant On this 17 Oday of blv 1996 before me a notary public in and for said County, personally appeare'd William J Hill, Plant Manager, Monticello Nuclear Generating Plant, and being first duly swom acknowledged that he is authorized to execute this document on behalf of Northem States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not interposed for delay.
MARVIN RICHARD ENGEN
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' NOTARY Puoug.amasusenTA Marvin R Engen /
my comm. so.Jan.st,seso; Notary Public-Minnesota Sherbume County My Commission Expires January 31,2000 7/17/96 NSP HADATA\\NRCCORR\\GL9507RADOC
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AttachmentA i
I Monticello Nuclear Generating Plant l
Response to Request for Additional information l
Reaardina Generic Letter 95-07 Requested information Through review of operationalexperience feedback, the staffis aware ofinstances where licensees have completed design orproceduralmodifications to preclude pressure locking or thermal binding which may have had an adverse impact on plant safety due to incornplete or incorrect evaluation of the potential effects of these modifications. Please describe evaluations and training forplant personnel that have been conducted for each design change or procedural modification completed to address potentialpressure locking or thermal binding concems.
Monticello Response
- 1. Pressure Lockina Monticello's resolution of pressure locking concems is being impimented by either performing a modification to the valves, which drilled a hole in the valve's disc, or by changing surveillance test procedures such that the system is declared inoperable and a Technical Specification Limiting Condition for Operation (LCO) is entered when these normally open valves are closed.
1.1 Anti-Pressure Locking Disc Hole MOV No.
Valve Description MO-1753 and MO-1754 Core Spray Inboard injection MO-2006' and MO-2007 RHR Torus Cooling / Spray
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MO-2014 and MO-2015 LPCI Injection inboard MO-2036 HPCI Steam Supply MO-2067 and MO-2068 HPCI Injection Outboard / Inboard MO-2106 and MO-2107 RCIC injection Outboard / Inboard These flex wedge gate valves have been modified to provide the added feature of a small hole drilled through one disc. This hole allows the fluid to communicate with the valve bonnet / body cavity thus preventing the trapping of higher pressure fluid and a valve pressure locking condition.
' in Monticello's 180 day response to GL 95-07 dated 2-12-96, a commitment was made to drill an anti-pressure locidng hole in the valve disc of MO-2007 prior to the completion of the 1996 refueling outage and MO-2006 prior to the completion of the 1998 refueling outage. A hole was installed in the disc of i
MO-2007 during the 1996 refueling outage which ended in May 1996.
7/17/96 NSP H:\\ DATA \\NRCCORR\\GL9507RA. DOC
Attachment A July 17,1996 Page 2 Safety evaluations per 10CRF50.59 and the following engineering evaluations were performed and concluded that the modifications do not constitute an unreviewed safety question.
Sealina Capability i
Affect of the modification on the valve performance sealing capability was evaluated and found to be consistent with dcsign requirements.
Structural Limits Affect of the modification on the valve structuralintegrity was evaluated and found that i
the modification has no adverse effect on the operation, structural integrity or valve thrust limits determined in the weak link analysis.
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Thermal Stress Affect of the modification on the valve was evaluated for situations were a small flow though the disc hole could occur, to determine if this flow could induce thermal fatigue.
The effects of this potentialleakage path were found to be insignificant.
Orientation To ensure that the disc is orientated correctly, a step in the modification installation procedure required proper orientation prior to valve assembly. Additionally, Monticello controlled valve drawings and valve mechanical maintenance procedures identify valve disc orientation requirements for correct re-assembly following any future maintenance activities.
1.2 Surveillance Testing Procedural Change YOV No.
Valve Description MO-1751 and MO-1752 Core Spray Outboard injection MO-2034 and MO-2035 HPCI Inboard / Outboard Steam Line isolation These valves are normally in their safety position of open. During surveillance testing prior to the valve being closed, test procedures require the system to be declared inoperable and a Technical Specification Limiting Condition for Operation (LCO) to be entered until the valve is re-opened. These non-complex procedural instructions are provided to plant operators in a very concise descriptive manner.
4 If valve maintenance arises which would allow an anti-pressure locking hole to be installed, this change will be considered which would eliminate the need for declaring the system inoperable during testing.
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AttachmentA July 17,1996 Page 3
- 2. Thermal Bindino MOV No.
Valve Description MO-2068 HPCI Pump Injection MO-2036 HPCI Turbine Steam Supply l
MO-2107 RCIC Pump Injection i
Monticello's plant shutdown procedure has been revised to require periodic cycling of these valves as valve body temperature decreases. Cycling of these valves does not create an abnormal system configuration. Additionally, these proceduralinstructions identify the
- reason for cycling these valves (i.e. relieve potential for thermal binding).
l The potential for thermal binding of these valves is considered low as Monticello has not l
experieravl thermal binding of the valves during past operations.
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