ML20115H320

Responds to RAI to Assist in Review & Evaluation of GL 95-07, Pressure Locking & Thermal Binding of SR Power Operated Gate Valves

ML20115H320
Person / Time
Site:	Point Beach
Issue date:	07/17/1996
From:	Link B WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20115H322	List: ML20115H320 ML20115H324 ML20115H326 ML20115H330 ML20115H333
References
GL-95-07, GL-95-7, VPNPD-96-043, VPNPD-96-43, NUDOCS 9607230054
Download: ML20115H320 (3)

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Wisconsin

> Electnc POWER COMPANY 231 W Michgan, PO Box 2046. Mdwoukes. WI 53201 2046 (414)221 2345 VPNPD-96-043 July 17,1996 Document Control Desk  ;

US NUCLEAR REGULATORY COMMISSION Mail Station PI-137 i Washington, DC 20553-0001 Ladies / Gentlemen:

DOCKETS 50-266 AND 50-301 RESPONSE TO REOUEST FOR ADDITIONAL INFORMATION -GENERIC LETTER 95-07 PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER OPERATED GATE VALVES POINT DEACH NUCLEAR PLANT. UNITS 1 AND 2 On August 17,1995, the Nuclear Regulatory Commission issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," requesting that licensees take actions to ensure that safety-related, power-operated gate valves, that are susceptible to pressure locking or thermal binding, are capable of performing their safety functions. Wisconsin Electric Power Company completed all of the requested actions discussed within the GL, and submitted a summary description of this information by letter ,

dated February 9,1996. I On June i1,1996, the NRC requested additional information to assist in the revicw and evaluation of our GL submittal. The following items were requested:

l. Operability determination for the PORV block valves.

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2. Documentation describing evaluations and training performed to address design and procedural modifications performed for thennal binding and pressure locking concerns.

The operability determination for the PORV block valves is contained in the two documents attached for your review. The resolution of potential thermal binding concerns for the PORY block valves, designated 1(2)RC-515 and 1(2)RC-516, was documented in internal memo PBM 95-0430, dated June 29,1995. The resolution of potential pressure locking concerns for the PORV block valves is contained in PBNP Calculation 96-0062, Revision 1. Based on these two documents, the PORV block valves are operable.  ;

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I l Document Control Desk July 17,1996 Page 2 l

In addition, to the thermal binding and pressure locking evaluations performed for the PORV block valves, PBNP is curratly evaluating the replacement of the existing wedge gate designed PORV block valves. The replacement valves being evaluated are parallel disk valves. The parallel disk design would increase the available opening margin for the PORV block valves. This evaluation is being performed as a proactive initiative for the PBNP reactor coolant system pressure increase and industry events involving PORV block valves.

To address the susceptibility to thermal binding and pressure locking of the motor-operated valves, SI-860A through D (Containment Spray Pump Discharge Valves), two procedure revisions were implemented. Inservice Test (IT) Procedures IT-05A and IT-06A, " Monthly Test of Containment Spray Pumps and Valves," were resised to include steps > cycle the SI-860 valves after the containment spray pump being tested has been secured. During IT testing, the potential exists for the bonnets of these valves to become pressurized to containment spray pump discharge pressure. The cycling of these valves will relieve any trapped bonnet pressure. These revisions were implemented on January 8,1996. These procedure changes added specific sign-off steps to the procedures, and therefore no additional training was considered necessary upon implementation. The evaluation supporting these procedure changes was documented in PBNP Calculation 96-0062, Revision 1, which concluded that these valves are operable with their bonnets pressurized to containment spray pump discharge pressure. No other procedural modifications or training were determined to be necessary.

We have not performed any design modifications to address thermal binding and pressure locking concerns at PDNP. Our GL 95-07 evaluation determined there was no need to perform modifications for valves within the scope of the GL. Evaluation of potential enhancements to the PORV block valve design are ongoing. As stated in our initial GL 95-07 submittal, fourteen (14) motor-operated gate valves within the GL scope were originally installed with bonnet relief paths to alleviate any thermal binding or pressure locking concerns.

Based on the actions we have taken to date, together with the submittal of this additional information, we believe that all requirements of Generic Letter 95-07 have been satisfactorily completed.

Please contact us if you have any questions or require any additional information.

Sincerely, i

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f t Bob Link Vice President Nuclear Power MDR/jg ec: NRC Resident inspector NRC Regional Administrator, Region 111

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M 3 SL 89- @ l PBM 95-0430 t i- l l TO: G. J. Maxfield  !

FROM: F. A. Mueller l

DATE: June 29, 1995  ;

SUBJECT:

RESOLUTION OF POTENTIAL THERMAL BINDING OF RC-515 AND RC-516, POWER OPERATED RELIEF. ISOLATION VALVES REFERENCE (S) : OP-3C l Generic Letter 89-10 j TS 15.3.1 .

TS 15.3.15 j COPY TO: W. B. Fromm F. A. Mueller i S. W. Greco S. A. Patulski l P. J. Katers A. L. Reimer ]

J. F. McNamara J. J. Roberts .

File J. A. Schroeder I

At the exit meeting for the Nuclear Regulatory Commission close-out inspection for the Generic Letter 89-10 Motor Operated Valve program, an open item concerning potential thermal binding of the Power Operated Relief Valve (PORV) isolation valves was noted. The scenario leading to this condition was as follows: Due to a leaking PORV, the corresponding PORV isolation valve, either RC-515 or RC-516, is closed in accordance with Technical Specification 15.3.1.A.S.a(1) while the plant is at full power and normal operating temperature. If the plant was then shutdown and cooled to a temperature corresponding to the initiation of Low Temperature Over-pressure Protection (LTOP), approximately 360*F, the valve body and disk could have cooled sufficiently that the valve would not open due to thermal binding.

Thermal binding of the PORV isolation valves while at power is not a concern as the only active safety function they have at that time is to go closed to.

isolate a leaking PORV. For all other conditions at power, these valves are maintained open. These valves are opened before arming LTOP as part of OP-3C,

" Hot Shutdown to Cold Shutdown," operating procedure. In the current revision of the procedure, Revision 62, dated May 22, 1995, valves RC-515 and RC-516 are verified open in steps 4.9.4 and 4.9.5. If these valves cannot be opened, Operators could then decide to either heat back up to relieve the thermal binding condition or to enter Technical Specification 15.3.15.A.2.

Technical Specification 15.3.15.A.2.a requires that if a single PORV isolation ,

-valve is inoperable for Reactor Coolant System temperature between 200*F and  !

360*F, the valve would have to be restored within 7 days or the system vented I and depressurized within the next 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. For a single PORV isolation valve l inoperable and the temperature below 200*F, 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is allowed for restoration of the valve or a total of 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> is allowed for the system to be depressurized and vented by Technical Specification 15.3.15.A.2.b. The most restrictive Technical Specification, 15.3.15.A.2.c., requires that the Reactor Coolant System be depressurized and vented within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> if both PORV isolation valves are inoperable. This time period is consistent with the Standard Technical Specifications and is based upon the expected time needed to perform this operation. Discussions with operations personnel indicate that this time requirement can be met.

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PBM 95-0430 t June 29, 1995- -

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A review of plant history shows that the PORV isolation valves have been l closed several times in the past. Discussions with plant operators indicate '

that these valves, RC-515 and RC-516, have openec5 following a cooldown from i operating temperature to LTOP operating temperature, f

Based upon the operational uses and Technical Specification requirements for j the PORV isolation valves, RC-515 and RC-516, a thermal binding condition  !

would not represent a safety problem. When at power, the valves only need to l close. When they are required to be opened for LTOP, sufficient time exists i to either allow for conditions to change to allow for their opening or l eliminate the need for their opening by depressurizing and venting the system.  !

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