BVY-98-158, Submits Clarification & Correction to NRC SER for GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power- Operated Gate Valves

Submits Clarification & Correction to NRC SER for GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power- Operated Gate Valves

ML20195D470
Person / Time
Site:	Vermont Yankee
Issue date:	11/13/1998
From:	Leach D VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-98-158, GL-95-07, GL-95-7, NUDOCS 9811180064
Download: ML20195D470 (2)

Text

_. . . __ . . _ _ _ _ . . _ _ _ _ _ _ ._ _ .___..__.____m

~i VERMONT YANKEE' y NUCLEAR POWER CORPORATION 185 Old Ferry Road, Brattleboro, VT 05301 7002 (802) 257-5271 November 13,1998 BVY 98-158 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Reference:

(a) Letter, USNRC to VYNPC, " Completion of Licensing Activity For Generic Letter 95-07", NVY 98-145, dated October 1,1998

Subject:

Vermont Yankee Nuclear Power Station License No. DPR-28 (Docket No. 50-271) I Corrections to NRC Safety Evaluation Report For Generic Letter 95 07 i

On August 17,1995, the NRC issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves", requesting licensees 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. In Reference (a), NRC issued Vermont

-Yankee a Safety Evaluation Report (SER) to close the Staft's review of our actions resulting from GL 95-07.

We have reviewed the subject SER and have identified two corrections / clarifications that are necessary and are addressed below:

SER Paragraph 3.2.c states:

"The licensee stated that procedures were revised to declare the low pressure core injection system inoperable when V10-25A/B, RHR Low Pressure Core Injection Valves, are shut during surveillance testing. The staff finds that the licensee's procedural changes provide assurance that pressure locking conditions are promptly identified, and is thus acceptable."

A clarification should be made to this paragraph to reflect that Vermont Yankee uses a pressure measurement between the normally closed isolation valve (V10-27A/B) and the inboard check j

valve (V10-46A/B) to detect back leakage into the system through the check valve. V10-25A/B g

is located between these valves and is not immediately shut for surveillances if sufYicient back leakage is present that could cause a pressure locking concern. Thus, our procedures contain instructions to check for conditions that could present a pressure locking concern with V10-25A/B. However, we do not routinely declare the subsystem inoperable to perform p

f, surveillance testing.

Our recommended correction to SER paragraph 3.2.c is as follows:

........precedures were revised to utilize a pressure measurement upstream of the injection check valve to deteralme the potential for pressure locking and if a concern is evident, not to proceed with the surveillance test without engineering evaluation. 'Ihe staff finds that ........"

981'1180064 98111 PDR ADOCK O 71 P PDR

'~

' ' BYY 98-158/page 2 SER Paragraph 3.2.d states: .

I "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. Valve V23-14, High Pressure Core Injection Steam Admission, is susceptible to thermal binding. As corrective action, procedures were revised to cycle V23-14 following every 10 F increase in steam dome temperature. His 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."

1 The V23-14 valve was initially determined to be potentially susceptible to both the pressure locking and thermal binding phenomenon. The pressure locking potential is present during plant ,

heat-up and the thermal binding concern during cool down. The cycling of the valve at 10'F increases in steam dome temperature was initially put in place for pressure locking concerns as an interim measure until valve modifications could be made. The valve modifications were completed during the 1996 refueling outage and this interim measure cancelled. However, there does remain a thermal binding concern during cool down for this valve. As a preventive measure for this thermal binding concern, we cycle the valve approximately every 50 F during cool down. ,

Our recommended correction to SER paragraph 3.2.d is as follows:

"..... Valve V23-14, High Pressure Core injection Steam Admission, is susceptible to thermal binding during plant cool down. As a corrective action, procedures were revised to cycle V23-14 following approximately each 50*F decrease in steam dome temperature... .."

We request that the subject SER be revised or supplemented to reflect these clarifications.

Should there be any questions pertaining to this request, please contact us.

Sincerely, VERMONT YANKEE NUCLEAR POWER CORPORA 110N

/

.#1 ~

n Ki pch Vice e# dent, Engineering cc: USNRC Region 1 Administrator USNRC Resident inspector- VYNPS USNRC Project Manager-VYNPS Vermont Department of Public Service