ML20205M011

Forwards Questions to Be Discussed in Upcoming Telcon on GL 95-07.Questions Transmitted by Fax on 990413 to J Rrainsberry of SCE

ML20205M011
Person / Time
Site:	San Onofre
Issue date:	04/13/1999
From:	Raghavan L NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
References
GL-95-07, GL-95-7, TAC-M93515, NUDOCS 9904150050
Download: ML20205M011 (3)

Text

(A M4g g4  % UNITED STATES g j t

NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2066fH201 4 ,o 9***** April 13,1999 MEMORANDUM FOR: Docket File ,

FROM: L. Raghavan, Senior Project Manager -

Project Directorate IV - Section 2 Division of Licensing Project Management Office of Nuclear Reactor Regulation

SUBJECT:

SAN ONOFRE NUCLEAR GENERATING STATION, --

FACSIMILE TRANSMISSION, ISSUES TO BE DISCUSSED IN AN UPCOMING PHONE CONVERSATION ON GL 95-07 (TAC M93515)

The attached questions were transmitted by fax today to Mr. Jack Rainseberry of Southern California Edison Company to prepare him and others for an upcoming telephone call. This memorandum and the attachment do not convey a formal request for information or represent an NRC staff position.

l l

Docket Numbers: 50-361 50-362  ;

Distribution .  ;

PUBLIC SONGS r/f S. Dembeck

\

,/

S%d 150002  :

9904150050 990413 PDR ADOCK 05000361 P PDR

1. Your submittal dated February 13,1996, states that you developed a pressure locking analytical method to demonstrate that the following WKM valves will operate during pressure locking conditions:

2(3)HV9306 2(3)HV9307 2(3)HV9336 2(3)HV9337 2(3)HV9339 2(3)HV9347 2(3)HV9348 2(3)HV9377 2(3)HV9378 2(3)HV9379 The submittal describes the calculation that was used to determine that the above valves would operate during pressure locking conditions. Upstream and downstream drag forces, stem rejection load, disk / stem weight and packing load are used to determine the force required to open the valve during pressure locking conditions. EPRI developed an analytical method for calculating the required i stem thrust to open a WKM valve during differential pressure conditions. This calculation included a term involving the friction coefficient between the gate and segment which is applicable when I cracking a valve open from the fully wedged position.

Explain how your pressure locking analytical method accounted for the friction between the gate and the segment.

2. On April 9,1997, a public meeting was conducted to discuss the Commonwealth Edison and Entergy Ooerations, Inc. pressure locking thrust prediction methodologies presented in GL 95-07 submittals. The minutes of the public meeting were issued on April 25,1997, and placed in the ,

Public Document Room. The Commonwealth Edison and Entergy Operations, Inc., methodologies that predict the thrust required to open pressure locked flexible-wedge gate valves, validation testing of the analytical method, enhancements to the Commonwealth Edison pressure locking methodology, and pressure locking tests sponsored by the NRC conducted by Idaho National Engineering and Environmental Laboratory were discussed during the meeting. The minutes of this public meeting indicate the typa of information requested by the NRC in order to review and approve pressure locking thrust prediction methodologies.

In order for the NRC to review your pressure locking thrust prediction methodology used for WKM valves, describe any testing that was performed that validated the methodology and discuss the recommended margin between actuator capability and the calculated thmst value when using your pressure locking prediction methodology, any limitations associated with tha use of your methodology

- and any diagnostic test equipment accuracy requirements. Commonwaalth Edison Company provided this type of information to the NRC in a letter dated May 29,1998. Thisletteris in the Public Document Room (Accession Number: 9806040184).

3. Your submittal dated February 13,1996, states that you developed a pressure locking analytical method to demonstrate that the following double disk Target Rock valves will operate during pressure locking conditions:

2(3)HV9235 2(3)HV9240

. 2(3)HV9247 2(3)HV9367 -

2(3)HV9368 2(3)LV0227C

.s 2

Pressure locking tests sponsored by the NRC were conducted by Idaho National Engineering and Environmental Laboratory on a double disk gate valve. The results of this testing are documented in NUREG/CR-6611,"Results of Press'ure Locking and Therms: Binding Tests of Gate Valves." Test data demonstrated that the double disk modified industry gate valve thrust equation trended with the pressure locking test results but generally underestimated the thrust required to open a pressure-locked valve. The NRC staff finds that the modified industry gate valve thrust equation provides reasonable assuiance that valves susceptlble to pressure locking are capable of performing their

- intended safety-related function provided that the margin between calculated pressure locking thrust and actuator capability exceeds 40 percent.

Discuss the recommended margin between actuator capability and the calculated thrust value when using your pressure locking prediction methodology for tbs above valves, any limitations associated with the use of your methodology and any diagnostic test equipment accuracy requirements.

4. Your submittal dated February 13,1996, states that all gate valves which are considered potentially susceptible to pressure locking are assumed to have water solid bonnet cavities. Explain why valves with steam filled bonnet cavities are not susceptible to pressure locking and if valves were excluded from the scope of GL 95-07 because their bonnet cavities were filled with steam in lieu of water.

5. Your submittals dated February 13, and September 3,1996, state that the following valves were susceptible to thermal binding:

)_

2(3)HV8152 2(3)HV8153 You stated that testing quantified the magnitude of the thermal binding effect, larger actuators were installed and that procedural revisions were implemented to limit the allowable temperature at which these valves can be closed. Discuss the testing that you performed that quantified the magnitude of thermal binding, how you calculated the addition thrust required to overcome thermal binding and how you determined that the valves would not thermally bind when closed before exceeding 250 F.

. 6. Your pressure locking analytical method credits intemal relief valves installed in the disks of WKM valves to prevent bonnet pressure from exceeding the upstream pressure by 300 psi. Explain if you periodically setpoint test the internal relief valve installed in the disk of WKM valves, and if not tested, explain why testing is not required.

7. Your February 13,1996, submittal states that a COF of .5 was used in the calculations that determine the amount of thrust reqt ed to operate WKM valves during oressure locking conditions.

Testing accomplished by EPRI indicates that the COF for WKM valves in low temperature applications where average contact stress normally does not exceed 10 KSI is .61. Explain why you are using a COF of .5 verses .61 and if testing accomplished during the GL 89-10 Program demonstrated that a COF of .5 is applicable.

8. Valves 2(3)HV9353,2(3)HV9359 are not listed in Table llA of your February 13,1996, submittal; however, your IST Program requires that these valves be stroke tested in the open direction. Explain why these valves are not susceptible to pressure locking or thermal binding.

1 . . . . .. . . . . . . . . . . . . .

.