ML20195E105

Safety Evaluation Accepting Licensee Response to GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power Operated Gate Valves, Issued 950817

ML20195E105
Person / Time
Site:	FitzPatrick
Issue date:	11/13/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20195D976	List: ML20195D971 ML20195E105
References
GL-95-07, GL-95-7, NUDOCS 9811180233
Download: ML20195E105 (3)

Text

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}- g NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 24e6 0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION  !

l RESPONSE TO GENERIC LETTER 95-07. " PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES" i POWER AUTHORITY OF THE STATE OF NEW YORK JAMES A. FITZPATRICK NUCLEAR POWER PLANT DOCKET NUMBER 50-333

1.0 INTRODUCTION

I Pressure locking and thermal binding represent potential common-cause failure mechanisms that can render redundant safety systems incapable of performing their safety functions. The ,

identification of susceptible valves and the determination of when the phenomena might occur l require a thorough knowledge of components, systems, and plant operations. Pressure locking occurs in flexible-wedge and double-disk gate valves when fluid becomes pressurized inside the valve bonnet and the actuator is not capable of overcoming the additional thrust requirements resulting from the differential pressure created across both valve disks by the pressurized fluid in the valve bonnet. Thermal binding is generally associated with a wedge gate valve that is closed i while the system is hot and then is allowed to cool before an attempt is made to open the valve.

Pressure locking or thermal binding occurs as a result of the valve design characteristics (wedge and valve body configuration, flexibility, and material thermal coefficients) when the valve is subjected to specific pressures and temperatures during various modes of plant operation. ,

Operating experience indicates that these situations were not always considered in many plants as part of the design basis for valves.

2.0 REGULATORY REQUIREMENTS 10 CFR Part 50 (Appendix A, General Design Criteria 1 and 4) and plant licensing safety analyses require or commit (or both) that licensees design and test safety-related components and systems to provide adequate assurance that those systems can perform their safety functions. Other individual criteria in Appendix A to 10 CFR Part 50 apply to specific systems. In accordance with those regulations and licensing commitments, and under the additional provisions of 10 CFR Part 50 (Appendix B, Criterion XVI), licensees are expected to act to ensure that safety-related power-operated gate valves susceptible to pressure locking or thermal binding are capable of performing their required safety functions.

On August 17,1995, the NRC issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," to request that licensees take certain 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 within the current licensing bases of the facility. GL 95-07 requested that each licensee, within 180 days of the date of issuance of the generic letter (1) evaluate the operational configurations of safety-related power-operated gate valves in its plant to identify valves that are susceptible to pressure locking or thermal binding, and (2) perform further analyses and take needed corrective actions (or justify 9811190233 981113 PDR ADOCK 05000333 P PDR Enclosure

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I longer schedules) to ensure that the susceptible valves, identified in (1) above, are capable of performing their intended safety functions under all modes of plant operation, including test configuration. In addition, GL 95-07 requested that licensees, within 180 days of the date of ,

issuance of the GL, provide to the NRC a summary description of (1) the susceptibility evaluation i used to determine that valves are or are not susceptible to pressure locking or thermal binding, (2) the results of the susceptibility evaluation, including a listing of the susceptible valves i identified, and (3) the corrective actions, or other dispositioning, for the valves identified as i susceptible to pressure locking or thermal binding. The NRC issued GL 95-07 as a " compliance I backfit" pursuant to 10 CFR 50.109(a)(4)(i) because modification may be necessary to bring facilities into compliance with the rules of the Commission referenced above.

In letters dated October 16,1995, and February 13 and March 8,1996, the Power Authority of the State of New York (the licensee, also known as the New York Power Authority) responsed to GL 95-07 for the James A. FitzPatrick Nuclear Power Plant. The NRC staff requested additional information on May 29,1996, which the licensee provided on June 27,1996.

3.0 STAFF EVALUATION 3.1 Scope of Licensee's Review GL 95-07 requested that licensees evaluate the operational configurations of safety-related power-operated gate valves in their plants to identify valves that are susceptible to pressure locking or thermal binding. The licensee's submittats of February 13, March 8, and June 27, 1996, described the scope of valves evaluated in response to GL 95-07. The NRC staff has reviewed the scope of the licensee's susceptibility evaluation performed in response to GL 95-07 and found it complete and acceptable. The criteria for determining the scope of power-operated valves for GL 95-07 are consistent with the staff's acceptance of the scope of motor-operated valves associated with GL 89-10, " Safety-Related Motor-Operated Valve Testing and Surveillance."

3.2 Corrective Actions GL 95-07 requested that licensees, within 180 days, perform further analyses as appropriate, and take appropriate corrective actions (orjustify longer schedules), to ensure that the susceptible valves identified are capable of performing their intended safety function under all modes of plant operation, including test configuration. The licensee's submittals discussed proposed corrective actions to address potential pressure-locking and thermal-binding problems. The staff's evaluation of the licensee's actions is discussed in the following paragraphs;

a. The licensee stated that the following valves were modified to eliminate the potential for pressure locking:

10MOV-17 Residual Heat Removal (RHR) Shutdown Cooling Outboard 10MOV-18 RHR Shutdown Cooling Inboard 10MOV-25A/B RHR/ Low Pressure Coolant injection (LPCI) Injection 10MOV-26A/B RHR Containment Spray 10MOV-39B RHR Torus Cooling Isolation 12MOV-15 Reacwr Water Clean Up (RWCU) Inboard 12MOV-18 RWCU Outboard 12MOV-69 RWCU Retum

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. 13MOV-15 Reactor Core isolation Cooling (RCIC) Steam Supply Inboard 13MOV-16 RCIC Steam Supply Outboard 13MOV-21 RCIC Pump Discharge Inboard 14MOV-12A/B Core Spray Inboard Isolation

-20MOV-82 Domineralized Water 23MOV-14 High Pressure Core injection (HPCI) Steam Supply Outboard 23MOV-15 HPCI Steam Supply Inboard 23MOV-16 HPCIInjection 23MOV-19 HPCI Pump Discharge inboard 29MOV-74 Main Steam inside Steam Drain 29MOV-77 Main Steam Drain To eliminate the potential for pressure locking, valve 13MOV-131, RCIC turbine steam isolation inlet, was replaced with a globe valve. The staff finds that physical modification to valves susceptible to pressure locking and replacement of a valve with a valve that is not susceptible to pressure locking are appropriate corrective actions to ensure operability of

- the valves and are thus acceptable.

b. The licensee stated that all flexible and solid wedge gate valves in the scope of GL 95-07 were evaluated for thermal binding. When evaluating whether valves were susceptible to thermal binding, the licensee assumed that thermal binding would not occur below specific temperature thresholds. The seating thrust for valves 14MOV-12NB, core spray inboard isolation, was reduced to minimize pullout thrust in order to provide additional assurance that the valves are not susceptible to thermal binding. This corrective action and the screening criteria used by the licensee provide a reasonable approach to identify those valves that might be susceptible to thermal binding. Until more definitive industry criteria are developed, the staff concludes that the licensee's actions to address thermal binding of gate valves are acceptable.

4.0 CONCLUSION

On the basis of this evaluation, the NRC staff finds that the licensee has performed appropriate evaluations of the operational configurations of safety-related power-operated gate valves to identify valves at the James A. FitzPatrick Nuclear Power Plant that are susceptible to pressure locking or thermal binding. In addition, the NRC staff finds that the licensee has taken appropriate corrective actions to ensure that these valves are capable of performing their intended safety functions. Therefore, the staff concludes that the licensee has adequately addressed the requested actions discussed in GL 95-07.

Principal Contributor: S. Tingen, NRR Date: November 13, 1998

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