ML20072A421
| ML20072A421 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 11/09/1982 |
| From: | Conn W BURNS & ROE CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| REF-PT21-83-888-000 82-10, BRGO-RO-82-012, PT21-83-888-000, NUDOCS 8306100122 | |
| Download: ML20072A421 (4) | |
Text
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Subject:
Work Order 3900-4000 7 P g:-
A Washington Public Power Supply System WNP-2 10CFR21 Reportable Condition'#82-10 Main Steam Isolation Valve-Leakage Control System
. Responds to:
NA.
November 9, 1982 BRGO-RO-82-012 Response Required:
NA U.S. Nuc1 car Regulatory Commission Region V 1450 Maria Lane, Suite 210 Walnut Creek, California 94956 Attention:
Mr. R.H. Engelken Centlemen:
This letter is to inform you of a condition we have deemed to be reportable under the guidelines set forth in 10CFR21.
WNP-2 design incorporates a Leakage Control System (LCS) past the Main Steam Isolation Valves (MSIV). The purpose of.
the system is to direct fission products, which may leak past the MSIV's, to the Standby Cas Treatment System (SGTS).
It has been discovered that a path of in-leakage may exist post-LOCA which could negate the ability of the MSIV-LCS to perform its safety function. This path exists because a' valve required to isolate post-LOCA is not powered from a crital bus. This could result in off-site doses which are a substantial fraction of 10CFR100 values.
Complete details are contained in the attached evaluation.
If you have any additional questions, please contact A.T. Luksic at (509) 943-8243.
Very truly yours, WGC:ATL:lvs Attachment U'
W.G. Conn cc:
B.A. Holmberg, SS w/a Senior Group Supervisor J.C. Tellefson, SS w/a R.T. Johnson, SS w/a L.C. Floyd, SS w/a R.M. Nelson, SS w/a E. LeBlanc, BPC w/a 8306100122 821109 PDR ADOCK 05000397 h
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l Attachment Main Steam Isolation Valve - Leakage Control System (MSIV-LCS)
(82-10)
Description of Deficiency WNP-2 design incorporates a leakage control system past the MSIV's in order to minimize the release of fission products if the MSIV's were to seat poorly.
Suction would normally be taken off the piping downstream of the outboard MSIV, and discharged into the Standby Gas Treatment System (SGTS).
It has been discovered that a valve, MS-V-146, on one of the branch pipes is not powered from a critical bus.
Post-LOCA, one could not assume it would close, nor could one assume the piping past the valve, ANSI B.31.1, would remain intact.
The fans associated with each MSLC system are designed for 50 cfm flow at 20" of water. Of this flowrate, about 107. is leakage from the main steam lines, the balance is diluent air.
This amount of steam does not affect the Standby Gas Treatment System Operation.
However, this flowrate is too small to create a face velocity of cufficient magnitude to assure in-leakage of Turbine Building at-mosphere into a 24" pipe.
Thus, the fan of the outboard MSLC will not create sufficient suction pressure and line velocities to as-sure that backflow of fission products past this open valve to the atmosphere and hence to the site boundary does not occur.
Date and Method of Discovery The deficiency was discovered during a Human Factors Engineering Review and documented on September 10, 1982.
Analysis of Safety Implication As stated above, the function of the MSLC system is to prevent po-tential leakage of containment atmosphere through closed main steam isolation valves from reaching the site boundary without filtration after a LOCA.
It is postulated that after a DBE, the non-seismic Class I steam piping will no longer be intact. An open path to the Turbine Building atmosphere will be created.
This leakage is postulated to occur at a rate of 11.5 ft /hr per steam line due to poor seating of the MSIV's.
The fission products in this leakage stream, were they to reach the site boundary with-our filtration, could result in off-site doses which are a sub-s: cacial fraction of 10CFR100 valves.
Corrective Action Valve MS-V-146 will be powered from a critical bus to assure that the MSIV-LCS can perform it's intended function when required.
Applicability to Other Nuclear Projects None.
This situation is unique to RNP-2.
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b) D&te Mailed to Other Regions -
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Give Written Report to Each Region V Affected Principal Inspector 9.
a) _Date Given to Principal Inspe_ctor(s) b) Name(s) of Inspectors Given To 10.
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