ML20072T945
| ML20072T945 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 03/24/1983 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-SSINS-6820 183, IEB-81-02, IEB-81-2, NUDOCS 8304110047 | |
| Download: ML20072T945 (3) | |
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March 24, 1983 Mr. James P. O'Reilly Serial No. 183 Regional Administrator N0/JHL:acm U. S. Nuclear Regulatory Commission Docket Nos. 50-338 l
Region II 50-339 101 Marietta Street, Suite 2900 License Nos. NPF-4 l
Atlanta, Georgia 30303 NPF-7 l
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Dear Mr. O'Reilly:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT NOS. 1 AND 2 j
REVISED RESPONSE TO I. E. BULLETIN NO. 81-02 Enclosed is the Virginia Electric and Power Company revised response to I. E.
Bulletin 81-02, " Failure of Gate Type Valves to Close Against Differential Pressure," for North Anna Power Station Unit Nos. I and 2.
This revised response supercedes our initial response dated May 22, 1981 (Serial No. 313).
Very truly yours.
O' l
W. L; Stewart I
l Enclosure l
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Mr. Robert A. Clark, Chief l
Operating Reactors Branch No. 3 Division of Licensing l
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REVISED RESPONSE TO IE BULLETIN 81-02 FAILURE OF GATE TYPE VALVES TO CLOSE AGAINST DIFFERENTIAL PRESSURE NORTH ANNA UNITS 1 AND 2 1.
Three valves, all installed in Unit 2, were identified:
a) MOV-2536 (3GM88 W-EMD manufactured valve)
This valve is installed as PORV Block Valve.
b) MOV-2373 (3GM88 W-EMD manufactured valve)
This valve is installed in the common charging pump recirculation flow path, c) MOV-2289B (3GM99 W-EMD manufactured valve)
This valve is installed in the normal charging line and serves to isolate normal charging flow path in the event of a safety inj ection.
2.
See responses to items 3-5.
3.
An evaluation was performed of the effect of these valves not being able to fully close on system (s) operability pursuant to Technical' Specifications:
a) MOV-2536 - The operability of this valve is not addressed in Tech Specs. Westinghouse has stated that " typically, these valves operated through 75% of their full disc travel leaving about 5% of the flow passage unsealed".
Therefore, the valve would serve to effectively isolate a stuck open PORV such that. charging pump flow could maintain RCS inventory and hence pressure, b) MOV-2373 - This valve was recently modified (Design Change 80-S63) to-remove the autcmatic Safety Injection closure signal.
Presently, emergency procedures call for this valve to be manually. closed only if RCS pressure decreases to below 1485 psig.
In addition,- once the individual charging' pump recirculation isolation valves (2775 A,'B,'C) are closed, there will be negligible AP across MOV 2373 and it would fully close.
c) MOV-2289B - This valve provides Train B isolation of normal. charging flow path in the event of a safety injection.
Since this valve is installed in series' with the Train A isolation valve.(MOV-2289A), it will see negible 'AP once the Train A valve closes.
As a' result, MOV-2289B would fully close after MOV-2289A closes.
4.
None of the affected valves were identified as spares.
5.
a) MOV-2536 - The maximum differential pressure this valve would be exposed to is approximately 2400 PSI.
The fact that - the valve will-close to-significantly restrict flow means - that the charging pumps should be able to maintain RCS inventory.-
During:the May, 1981. Unit 2. outage,. the following modifications were completed on this valve to ensure full closure for rated conditions:
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1.
The motor pinion / worm shaft'gearset was changed to be made compatible with the required thrust range.
1 2.
The control circuit wiring'for the limitorque operator was changed to limit closing to ensure a positive and predictabic seating load, I
b) MOV-2373 - The maximum differential pressure this valve would be exposed to is approximately 2600 PSI (the shutoff head of the charging pump). Since this valve is in series with the 2775 A, B, C# valves, it would fully close once these valves closed.
During the May, 1981 Unit 2 outage, the same modifications done on j
MOV-2536 were also completed for MOV-2373. This work completes all modifications required to upgrade these valves to their original rating,,
l c) MOV-2289B - The maximum differential pressure this valve would be exposed to is approximately 850 PSI (assuming S. I. initiated by RCS low pressure at 1765 PSIG).
Since this valve is in series with the l'
2289A valve, MOV-2289B would be assured of fully closing once the MOV-2289A closed.
i The modifications to this valve have been accomplished.
During the May, 1981 Unit 2 outage, the following work was completed:
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1.
The originally installed SMB-000 operator was replaced with a SB-00 operator. The SB-00' operator was modified with a new motor pinion / worm gearset to be compatible with the required thrust range.
In addition, the motor operator was fitted with a new stem nut to make the operator compatible with the original valve stem..
Finally, as was done for the other two valves, the control circuit for the limitorque operator was changed to. limit closing.
No further modification is contemplated for this valve.
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