ML19282B550
| ML19282B550 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 03/09/1979 |
| From: | Renberger D WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| GO1-79-154, NUDOCS 7903150340 | |
| Download: ML19282B550 (3) | |
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P Q Row 168 3300 Gao WassiNGrom Way R : cH L a N o W a sw,Nu f oN 39352 PHowa(SC3s 9 4 6 161 t March 9,1979 G01 154 fluclear Regulatory Commission Region V Suite 202 Walnut Creek Plaza 1900 ft. California Boulevard Walnut Creek, California 94596 Attention:
f1r. R. H. Engelken Director
Dear Mr. Engelken:
Subject:
WPPSS fluclear Project Nos.1/4 Docket flumbers 50-460 and 50-513 Reportable Condition 10CFR50.55(e)
WVJ4 Valve Overpressurization Your staff was informed of a reportable deficiency under the provisions of 10CFR50.55(e) by telecon on February 9,1979.
Appendix A to this letter contains the WPPSS final report on the subject condition.
If you have any questions, or desire further information, please advise.
Very truly yours, o d /22Jy D. L. Renberger Attachment Assistant Director-Technology DLR:TJH:jds cc: CR Bryant - BPA BD Redd - UE&C, Pnil.
JG Davis - NRC Region 1
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APPENDIX A WPPSS Nuclear Projects Nos. 1/4 Docket Numbers 50-460 and 50-513 Reportable Condition 10CFR50.55(e)
Wai Valve Overpressurization DESCRIPTION OF THE DEFICIENCY The WKM Pow-R-Seal gate valve is a double sealing valve and as such requires special provision for pressure relief of fluids that may be trapped in the internal body cavities of the valve. When fluids trapped in the internal body cavity are heated due to increased temperatures of adjacent piping systems or of the environment, substantial pressure increases may result that could rupture the valve. hhen the valve is in tne closed position, over-pressure relief is obtained by means of a relief valve installed in the segment, which relieves the fluid to the upstream side of the valve.
(Note:
the segment is a portion of the valve which, together with the valve gate, provides the required sealing function.) The reported concern is that when the valve is in the open position, there is no provision for pressure relief since the relief valve is not designed to function in this position.
The subject valves cre used in the following applications ir. the B&W 205FA plant:
(a) 2 are la" core flood tank isolation valves (CFV 1A and B)
(b) 2 are 4" make-up tank isolation valves (MUV 30 and 31)
(c) 2 are 12" in the low pressure injection line (DHV IA and B)
(d) 4 are 12" in the decay heat letdown drop line (DHV 11A and B, 12A and B)
(e) 1 is a 2-1/2" pressurizer spray line isolation valve (RCV 11)
(f) 1 is a 4" pressurizer relief isolaticn valve (RCV 10)
CAUSE AND ANALYSIS The valve manufacturer had claimed until recently that pressure relief is provided when the valve is open because there is sufficient leakage between the mating surfaces of the segment and the gate to provide communication between the body and the valve conduit to prevent overpressurization.
In a meeting between B&W and the valve manufacturer on November 3,1978, the valve manu-facturer stated they could not guarantee that there was ccmmunication between the cavity and the conduit. They therefore concluded that the potential to overpressurize did exist with tr.e valve cpen.
9 APPENDIX A Page Two CAUSE AND ANALYSIS (Cont'd)
An analysis has not been performed to determine with certainty that over-pressurization of gate valves used as core flood isolation valves and on the low pressure injection line constitutes a significant deficiency. Sufficient potential concern exists, however, to deem it reportable under the provisions of 10CFR50.55(e) for the WNP-1 and -4 units. The basis for reportability is that, as defined by the regulation, there potentially is a "significant deficiency in the final design approval and released for construction," and that the defi ier.cy, were it ta remair.. corrected, could acversely affect c
safe operation of the plant.
SAFETY IMPLICATIONS As an example, two applications of the valves which are safety concerns are the core flood tank isolation valves and the low pressure injection line valves; both of these applications are in the ECCS. The potential exists that, during or following a LOCA, the valve cavities could undergo a thermal transient and overpressurize.
An analysis has not been made to determine the degree to which the valve would be deformed or damaged when subjected to these thermal transients.
If valve body rupture were to take place, it could redure the flow from the core flood tank or from the low pressure injection system in a non-conservative manner with respect to the safety analysis.
This occurrence therefore has the potential for adversely affecting safety of plant operations.
CORRECTIVE ACTION All of the valves listed in the description of the deficiency will be modified by the manufacturer to ensure that overocessurication of the valve body cannot occur. A field change package has been prepared to authorize valve modification for the valves that have been shipped, and the manufacturer has agreed to modify the design on the remaining valves on order.
The modification requires that a 1/16" hold be drilled radially through the bottom of the gate. This 1/16" hole prevents the trapping of fluid in the valve body with the valve in the open position and a subsequent overpressuriza-tion of the valve body.