ML20195J644

Forwards Request for Addl Info Re GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power-Operated Gate Valves. Response Requested within 30 Days of Receipt of Ltr

ML20195J644
Person / Time
Site:	San Onofre
Issue date:	06/15/1999
From:	Raghavan L NRC (Affiliation Not Assigned)
To:	Ray H SOUTHERN CALIFORNIA EDISON CO.
References
GL-95-07, GL-95-7, TAC-M93515, TAC-M93516, NUDOCS 9906210066
Download: ML20195J644 (5)

Text

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• . June 15,1999 3 Mr. Harold B. Ray Executive Vice President Southern California Edison Company San Onofre Nuclear Generating Station

- P. O. Box 128 San Clemente, CA 92674-0128

SUBJECT:

SAN ONOFRE NUCLEAR GENERATING STATION (SONGS), UNITS 2 AND 3 -

REQUEST FOR ADDITIONAL INFORMATION - GENERIC LETTER 95-07,

" PRESSURE LOCKING ANDTHERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES,"(TAC NOS. M93515 AND M93516)

Dear Mr. Rayi.

On August 17,1995, the U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate

. Valves," to request licensees to 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. In a letter of February 13,1996, you submitted your 180-day response to the GL for SONGS. In response to our request for additional information (RAl), by letter dated September 3,1996, you provided additional information. Our review of your submittal is in progress. To complete its review, the NRC staff has determined that additionalinformation as discussed in the' enclosure is necessary.;

- The enclosed request was discussed with Mr. Jack Rainsberry of your licensing staff. A mutually agreeable target date of within 30 days of receipt of this letter for your response was established.' .lf circumstances result in the need to revise the target date, please call me at (301) 415-1471 at the eariiest opportunity. '

Sincerely

• /s/

9906210066 990615 g . L: Raghavan, Senior Project Manager, Section 2 PDR ADOCK 05000361 ,

Project Directorate IV & Decommissioning ,

P PDR .6.

• Division of Licensing Project Management Office of Nuclear Reactor Regulation

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Docket Nos. 50-361 and 50-362 -

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% *'**** June 15, 1999 Mr. Harold B. Ray Executive Vice President Southern California Edison Company San Onofre Nuclear Generating Station P. O. Box 128 '

San Clemente, CA 92674-0128 l

SUBJECT:

SAN ONOFRE NUCLEAR GENERATING STATION (SONGS), UNITS 2 AND 3 -

REQUEST FOR ADDITIONAL INFORMATION - GENERIC LETTER 95-07,

" PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED

]

POWER-OPERATED GATE VALVES," (TAC NOS. M93515 AND M93516)

Dear Mr. Ray:

On August 17,1995, the U.S. Nuclear Regulatory Commission (NRC) issued deneric Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," to request licensees to 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. In a letter of February 13,1996, you submitted your 180-day response to the GL for SONGS. In response to our request for additional information (RAl), by letter dated September 3,1996, you provided additional information. Our review of your submittal is in

. progress. To complete its review, the NRC staff has determined that additional information as discussed in the enclosure is necessary.

The enclosed request was discussed with Mr. Jack Rainsberry of your licensing staff. A mutually agreeable target date of within 30 days of receipt of this letter for your response was !

established, if circumstances result in the need to revise the target date, please call me at (301) 415-1471 at the earliest opportunity.

Sincerely  :

L. Raghavan, Senior Project Manager, Section 2 Project Directorate IV & Decommiss oning Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-361 and 50-362

Enclosure:

As stated cc w/ encl:- See next page

San Onofre Nuclear Generating Station, Units 2 and 3 cc: ,

Mr. R. W. Krieger, Vice President Mayor Southem Califomia Edison Company City of San Clemente San Onofre Nuclear Generating Station 100 Avenida Presidio P. O. Box 128 San Clemente, CA 92672 San Clemente,' CA 92674-0128 Mr. Dwight E. Nunn, Vice President Chairman, Board of Supervisors Southem Califomia Edison Company County of San Diego San Onofre Nuclear Generating Station 1600 Pacific Highway, Room 335 P.O. Box 128 San Diego, CA 92101 San Clemente, CA 92674-0128 Alan R. Watts, Esq.

Woodruff, Spradlin & Smart 701 S. Parker St. No. 7000 Orange, CA 9266E 4720 Mr. Sherwin Harris Resource Project Manager Public Utilities Department City of Riverside 3900 Main Street Riverside, CA 92522 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower & Pavilion 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 Mr. Michael Olson San Onofre Liaison

. San Diego Gas & Electric Company P.O. Box 1831 San Diego, CA 92112-4150 Mr. Steve Hsu Radiologic Health Branch State Department of Health Services Post Office Box 942732 ~ l

. Sacramento, CA 94234 Resident inspector / San Onofre NPS c/o U.S. Nuclear Regulatory Commission

)

Post Office Box 4329 San Clemente, CA 92674 June 1 %

- i

C REQUEST FOR ADDITIONAL INFORMATION SAN ONOFRE NUCLEAR GENERATING STATION RESPONSE TO GENERIC LETTER 95-07.

" PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES"

1. Your February 13,1996, submittal states that you developed a pressure-locking thrust prediction methodology to demonstrate that the following WKM and Target Rock valves will operate during pressure locking conditions:

WKM Valves 2(3)HV9306 Safety injection (SI) Recirculation to Refueling Water Storage Tank (RWST) 2(3)HV9307 St Recirculation to RWST 2(3)HV9336 Shutdown Cooling System (SDCS) to Low Pressure Safety injection (LPSI) 1 Pump Suction i 2(3)HV9337 SDCS to LPSI Pump Suction

! SDCS From Reactor Coolant System (RCS) Loop 2 2(3)HV9339 2(3)HV9347 SI Recirculation Retum to RWST isolation 2(3)HV9348 SI Recirculation Retum to RWST isolation 2(3)HV9377 SDCS Bypass to LPSI Suction isolation 2(3)HV9378 SDCS Bypass to LPSI Suction isolation 2(3)HV9379 SDCS Bypass to LPSI Suction isolation l Taraet Rock valves 2(3)HV9235 Boric Acid Makeup (BAMU) Tank Gravity Feed to Charging Pump Suction 2(3)HV9240 BAMU Tank to Charging Pump Suction Header Control Valve 2(3)HV9247 BAMU Pump to Charging Pump Suction Control Valve 2(3)HV9367 Containment Spray Pump Discharge 2(3)HV9368 Containment Spray Pump Discharge 2(3)LV0227C RWST to Charging Pump Suction Header The NRC staff has approved the use of pressure-locking thrust prediction methodologies to demonstrate that valves will operate during pressure-locking conditions as acceptable corrective action for GL 95-07 provided that the pressure-locking thrust prediction methodology is validated by testing. For example, Commonwealth Edison (Comed) and Entergy Operations, Inc. (EOl), developed pressure-locking thrust prediction methodologies for flexible wedge gate valves. Comed recommends that, when using its methodology, minimum margins should be applied between calculated pressure-locking thrust and actuator capability. These margins along with diagnostic equipment accuracy and methodology limitations are defined in a letter from Comed to the NRC dated May 29,1998 (Accession Number 9806040184). The NRC considers the use of the Comed pressure-locking methodology acceptable for long-term corrective action provided these margins, diagnostic equipment accuracy requirements, and methodology limitations are incorporated into the pressure-locking calculations. Comed and EOl validated their i pressure-locking thrust prediction methodologies with test programs. The NRC is currently l reviewing the EOl pressure-locking thrust prediction methodology. s l

ENCLOSURE

I 1

The NRC staff has also approved the use of a modified industry gate valve thrust equation (double disk area) for calculating the thrust required to open double disk gate valves during pressure-locking conditions._ The double disk gate valve pressure-locking thrust prediction methodology and the testing used to validate the methodology are described in NUREG/CR-6611, "Results of Pressure Locking and Thermal Binding Tests of Gate Valves." The test data demonstrated that the results of the double disk gate valve .

pressure-locking thrust prediction methodology trended with the pressure-locking test i results but generally underestimated the thrust required to open a pressure-locked valve.

The NRC staff considers sizing and setting the valve actuator to deliver the thrust determined from the double disk gate valve pressure-locking thrust prediction methodology to be acceptable long-term corrective action for GL 95-07 provided that the margin between calculated pressure-locking thrust and actuator capability exceeds 40 percent.  ;

This large margin is needed to account for valve degradation, diagnostic equipment accuracy, and the additional thrust that was required to open the test valve.

i in a telephone discussion with the NRC on May 29,1999, your staff stated that the design of WKM valves is such that the friction coefficient between the gate and segment is not applicable when a valve opens during pressure-locking conditions; therefore, your pressure-locking thrust prediction methodology is not required to account for the friction between the gate and segment. Please describe and discuss:

a. the testing that validates your pressure-locking thrust prediction methodology, and

b. the recommended margin between actuator capability and the calculated thrust value when using your pressure-locking prediction methodology, any limitations associated with the use of your methodology, and any diagnostic test equipment accuracy requireraants. l

2. Your submittal dated February 13,1996, states that you credit the intemal relief valve insta!!ed in the disk of WKM valves to prevent bonnet pressure from exceeding the upstream pressure by 300 psi. The IJRC staff considers that failure of the intemal relief valve to relieve pressure in the bonnet could prevent a valve from opening during pressure-locking conditions. Please:

a. discuss if you periodically test the intamal relief valve, and if not tested, explain why testing is not required;

b. explain why the intamal relief valve feature is not required to be included in your inservice testing program; and

c. explain why WKM valves are equipped with an intamal relief valve. Normally, valves

are not equipped with an intamal relief valve.