ML20214H409
| ML20214H409 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/14/1987 |
| From: | Carey J DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 2NRC-7-120, 87-13, NUDOCS 8705270375 | |
| Download: ML20214H409 (3) | |
Text
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' 7pp 2NRC-7-120 Beaver Valley No. 2 Unit Project Organization Telecopy
-8 ku ""$[8 May 14, 1987 sox Shippingport, PA 15077 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 ATTENTION: Mr. William T. Russell Administrator
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Pressure Locking and Thermal Binding of Westinghouse Gate Valves Potential Significant Deficiency Report 87-13 f
i Gentlemen:
This Potentially Reportable Significant Deficiency Report is being submitted pursuant to the requirements of 10CFR50.55(e).
It is anticipated that no additional reports will be required.
DUQUESNE LIGHT COMPANY By J. J. Carey Sr. Vice President LMR/ijr NRC/LMR/SDR/8713 Attachment AR/NAR cc: Mr. P. Tam, Project Manager (w/a)
Mr. J. M. Taylor, Director (3) (w/a)
Mr. J. Beall, Sr. Resident Inspector (w/a)
Mr. L. Prividy, NRC Resident Inspector (w/a)
INP0 Records Center (w/a)
NRC Document Control Desk (w/a) h((
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ATTACHMENT 1.
Summary Significant Operating Experience Report (50ER) 84-7 identified a potential problem with the operability of gate valves due to _ differential pressure locking, liquid entrapment, and/or_ thermal binding.
Stone & Webster Engineering Corporation (SWEC) has determined that ten (10) Westinghouse NSSS valves require a modification, as recommended.i n 50ER 84-7, to prevent valve bonnet over-pressurization caused by differential pressure blocking or liquid entrapment.
2.
Immediate Action Taken SWEC initiated a review of all normally closed gate valves that are required to open in response to an automatic signal and/or to provide emergency core cooling.
Mr. L. M. Rabenau, Lead Compliance Engineer, Beaver Valley. Power Station Unit No. 2, notified Mr. D. Limroth, NRC Region I, of this concern on April 15, 1987.
3.
Description of Deficiency' Differential pressure locking occurs when high pressure fluid contained in a gate valve bonnet cavity prevents valve opening.
Bonnet cavities of certain Westinghouse gate valves could become pressurized by high pressure charging fluid and experience differential pressure locking.
Liquid entrapment occurs when fluid contained in a gate valve bonnet cavi-ty is heated by a local high temperature-source or building ambient temperature.
This heating increases cavity pressure to prevent valve opening.
Since a loss of ventilation is assumed coincident with a design basis accident, several Westinghouse valves required for cold or hot leg injection are subject to this condition.
Gate valves that are closed hot and required to open cold could be subject to thermal binding. None of the valves that were evaluated are subject to this condition.
4.
Analysis of Safety Implication The ten safety-related gate valves in the Emergency Core Cooling (ECCS) a n d Residual Heat Removal (RHR) Systems that require the recomended modification are as follows:
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a s-
. e a) 2 SIS *MOV867A & B: Cold Leg Injection Isolation-Valves Function: Open automatically in response to an SI signal for cold leg injection.
b) 2 SIS *M0V836:
HHSI to Cold Leg Isolation Valve Function: Open automatically for shift. to cold leg recirculation.
c) 2 SIS *M0V869A&B, 8889: Hot Leg Recirculation Isolation Valves Function: Open by remote operator action for hot leg recircula-tion.
The loss of operability of any of these ECCS valves will impair the capability to mitigate the consequences of a DBA-LOCA.
d) 2RHS*MOV701A&B, 702A&B: ' RHR Suction Isolation Valves Function: Open for second phase of plant cooldown.
The loss of operability of these valves could affect ability of the plant to achieve and maintain cold shutdown.
5.
Corrective Action to Resolve the Deficiency The-SWEC review resulted in the initiation of Advance Change Notice (ACN)
D-0266, which called for the drilling of a 1/8 inch diameter hole in the upstream face-of the discs for the 10 valves. The corrective action has been completed.
6.
Additional Report No additional reports are expected.
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