ML20064B745

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/03X-1 on 780305:loss of Svc Water Flow Through Charging Pump Intermediate Seal Cooler Was Caused by Corrosion of Stem of Discharge Gate Valve;Corrosion Was Galvanic(Brass Touching Bronze);Problem Will Be Studied
ML20064B745
Person / Time
Site: Surry Dominion icon.png
Issue date: 10/03/1978
From: Baucom T
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18113A547 List:
References
LER-78-004-03X, LER-78-4-3X, NUDOCS 7810100079
Download: ML20064B745 (3)
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61 CCC4ET NUveER 64 69 EVENT OATE 74 75 RE*CRT QATE e3 EVENT CESCRIPTION AND PROBASLE CONSECUENCES h l 1 o i 2 I lWith unit in nornal operation. at rated power, charging pump intermediate seal cooler l

,, ,3, ,1-SW-E-13 was checked for service water flow. This check was prompted by an observed, j

,3,,, gno-flow condition on unit 2 "B" cooler. As on Unit 2, Unit 1 "B" cooler had no flow. ;

y n , , , ,This is contrary to T.S.-3.3. A.S.C. and is reportable per T.S. 6.6.2.b. (2) . The fully

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,,,aj ps on Unit 2, the no flow condition was caused by a dropped disc in the cooler outlet j y , , , , [ isolation valve. The valve was disassembled and the disc removed. Subsequently, a  ;

replacement for the corroded stem was fabricated. The old disc and a new stem uere I l

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I Virginia Electric and Powar Company Surry Power Station Docket No: 050-0280 LER 73-004/03X-1 Event Date 3-5-78 foss of Service Water Flow Through Charging Puop Intermediate Seal Cooler

1. Description of Event:

At about 1500, 3-5-78, with the unit at normal operation and at rated power, the charging pump intermediate seal cooler 1-SW-E-1B was found to have no service water flow. This check was prompted by the discovery of a similar condition found on Unit 2 at about 1300 on the same day (reported in Unit 2 LER-78-004/03L-0). This event is contrary to Technical Specification ~ 3.3.A.8.C. and is reportable in accordance with Technical Specification 6.6.2.b.(2).

2. Probable Consequence of Event:

The loss of the charging pu=p intermediate seal cooler 1-SW-E-13 had no effect upon the health and safety of the general public because adequate cooling of the charging pump component cooling system was available via the "A" charging pump intermediate seal cooler, which is a full size cooler.

3. Cause of Event:

The loss of flow to the "B" intermediate seal cooler was due to the failure of the cooler's discharge gate valve. Corrosion of the stem permitted the disc to drop free and obstruct the service water flow path. 4 Immediate Corrective Action: The ic=ediate action was to verify flow to seal cooler 1-SW-E-1A. Cooler "B" was then isolated, the suspected valve was opened and the disc removed. A new steu was fabricated from stainless steel. The new stem and old disc were re-installed and the valve raturned to service. J Following repair of the "B" cooler discharge valve, the "B" cooler was placed in service. The "A" cooler was isolated to examine its discharge valve. A similar condition of stem corrosion was found but had not advanced to the point of dropping the disc. A new stem was fabricated and installed in this valve.

5. Scheduled Corrective Action:

The initial report indicated that all of the 1 1/2" and 2" valves in the charging pump service water system would be inspected during the then forthecming rufueling outage. This inspection was performed and several of the ralves were found in various stages of deterioration. However, due to the availability of spare parts, only those valves required to provide flow to at least luo lube oil coolers and one intermediate seal cooler were repaired or replaced. The other lube oil cooler and seal cooler are operable but with valves in varying stages of deterioration. As parts become available, these valves will be repaired. If they should fail before this, flow can be established by removal of the disc. l t l

tal Virginia Electric and Powar Company Surry Power Station, Unit 1 Docket No: 050-0280 LER 78-004/03X-1  ; Event Date 3-5-78 j i Loss of Service Water Flow Throuch Charging Puno Intermediate Seal Cooler )

6. Action Taken to Prevent Recurrence:

An engineering study was instituted to identify possible long term corrective action. Also discussed in the study was the mode of corrosion. From observation of the failed components, it was decided that the mode of corrosion was predominantly galvanic, due to the brass stem in contacc with the bronze disc. The brass, being the anode of this galvanic couple, would I be wasted as was observed. 

                                                                         ~

As far as long term corrective action is concerned, it was concluded that a suitable replacementa valve with a valve design that embodies less dissimilarity of materials and a " fail-as-is" principle, should be installed in place of the existing valves. Based on this conclusion, a design change has been initiated to implement this idea. Present indications are that the replacement will commence concurrent with the steam generator replacement (s).

7. Generic Imolications:

The event possesses generic implications in that the corrosion observed in the cooler outlet valves may also exist in other gate valves of the f charging pump service water system. Based on the inspection performed, it was found that this problem was generic in the Walworth 1 1/2" and 2" gate valves. Whether this problem exists in other types of safety related service' water valves will be determined in a separate study. 

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