ML20058F873
| ML20058F873 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/02/1993 |
| From: | J. J. Barton GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C321-93-2316, GL-89-10, NUDOCS 9312090030 | |
| Download: ML20058F873 (3) | |
Text
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I GPU Nuclear Corporation u Nuclear
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i Forked River, New Jersey 08731-o388 609 971-4000 f
Wnter's Direct D;al Number:
December 2, 1993 l
C321-93-2316 U. S. Nuclear Regulatory Commission Att: Document Control Desk Washington, DC 20555 l
Gentlemen:
Subject:
Oyster Creek Nuclear Generating Station (OCNGS) l Operating License No. DPR-16 i
Docket No. 50-219 1
Generic letter 89 Core Spray System i
Motor Operated Valves Differential Pressure Test In accordance with the Generic Letter 89-10 Motor Operated Valve (MOV)
Program, GPUN has reviewed the feasibility of in-situ differential pressura
-l testing of the Core Spray System parallel injection valves (V-20-15, V-20-21, V-20-40 and V-20-41) and the test isolation valves (V-20-12 and V-20-18).
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The Core Spray System parallel injection valves and test isolation valves are i
8-inch Anchor Darling 600 lb. stainless steel flex wedge gate valves, with Limitorque SMB-1 actuators. These valves were originally purchased for 1250 psid design conditions. The design basis reviews completed for the G.L. 89-10 MOV Program have indicated that the maximum differential pressure these valves would be required to operate against is 320 psid.
The safety function of the parallel injection valves is to open against Core Spray pump head to allow core spray flow into the vessel for a loss-of-Coolant-Accident (LOCA). The safety function for these valves in the closing direction is to maintain vessel level control in certain design basis events, and complete isolation is not a requirement under these conditions.
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The safety function of the test isolation valves is to open against core spray pump head in the event the valve is closed during surveillance testing and a' j
LOCA occurs. These valves do not have a closing safety function.
The minimum calculated undervoltage thrust available in the opening direction for the parallel injection valves and the test isolation valves is 19,375 lbs.
This calculated thrust is based on a 0.40 gear pullout efficiency,1.0 application factor, a 0.2 stem friction coefficient, and appropriate temperature and voltage derated motor torque. Recent static tests conducted on three of these valves at OCNGS indicates a stem friction coefficient of 1
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C321-93-2316 Page 2 i
0.b6-0.12.
Static and dynamic tests of other G.L. 89-10 Program valves 4
indicate an average stem coefficient of 0.11 with an overall range of 0.06 to 0.18.
In addition, these valves are located in the Reactor Building outside the Drywell/ Primary Containment where ambient conditions are not detrimental j
to the stem lubricant. The open torque switch is bypassed for the first 25 -
30% of valve travel for these valves. The available thrust of 19,375 lbs.
provides sufficient thrust to allow valve opening against the design differential pressure with a valve factor equivalent to 1.25 based on a mean seat diameter of 7.3125 inches and an assumed packing load of 2500 lbs.
Static testing has indicated packing loads less then 1100 lbs. Assuming a i
coi,ervative valve factor of 0.6 and ignoring stem rejection load which aids i
valve opening, the minimum available margin for these valves is 109%.
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In the closing direction for the Core Spray parallel injection valves, we will utilize a 0.6 valve factor. This is based on EPRI testing of a 10 inch, 300 lb., Anchor Darling carbon steel flex wedge gate valve that indicates a maximum seat friction coefficient of 0.39 at 630 psid, which equates to an apparent valve factor of 0.41 for the OCNGS valves. Additional in-situ j
testing at the Monticello Plant for the EPRI Program of 16 inch, 600 lb.
Anchor Darling carbon steel flex wedge gate valves indicates apparent valve factors of 0.18 to 0.32 at 335 psid. Therefore, the assumed valve factor of 0.6 is considered conservative. The weak link limit for these valves is 1
40,000 lbs. and the operator rating is 45,000 lbs. A close torque switch setting corresponding to an available thrust of 18,000 lbs. would result in a minimum thrust margin, after equipment inaccuracy, above a conservative 0.6 valve factor of approximately 67%, based on using the M0 VATS Torque Thrust Cell, and a margin of approximately 120% based on the EPRI test results (valve factor of 0.41).
This margin is available to mitigate rate-of-loading effects, potential lubrication degradation, and valve factor uncertainty.
Furthermore, as stated previously, complete isolation is not a requirement for these valves.
These motor-operated valves have been shown to have sufficient design margin in terms of original design basis functional requirements and actuator thrust capability. This inherent margin is confirmed by calculations using conservative assumptions and review of industry test data as referenced above.
In addition, these valves are physically located in a normally non-harsh environment. A dynamic test of these valves would likely generate a crud burst affecting radiation levels and dose in the drywell and refueling floor.
Any crud injected into the vessel would require cleanup prior to continuing refueling activities during the outage, which necessitates availability of the Reactor Water Cleanup System during and after such a test. This activity would impact the ISR outage schedule by 2 - 3 days, based on testing of 2 of the 6 identical valves, and result in additional radwaste generation and i
I potential ALARA considerations.
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C321-93-2316 Page 3 On this basis, it is concluded that dynamic flow testing of the Core Spray Injection and Test Isolation motor-operated valves will not provide additional data of safety significance to justify the potential adverse consequences and outage schedule impact. The OCNGS G.L. 89-10 Motor Operated Valve Program Description will be updated accordingly to document this exception-for the Core Spray System Injection and Test Isolation Valves.
Sincerely, e
i g J. J. Ba'rton Vice President and Director Oyster Creek Nuclear Generating Station JJB/DJD/amc cc: Administrator, Region I Oyster Creek NRC Project Manager Senior Resident NRC Inspector i
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