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AEOD/E303 Rept Re 811128 Valve Flooding Event.Analysis Showed That Water Is Available for Min of 13.7 H Before Makeup to Intake Canal Necessary.Licensee Installed Dikes, Lights & Upgraded Maint Procedures
	ML20245L276
Person / Time
Site:	Surry
Issue date:	02/16/1983
From:	Zukor D; NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	;
Shared Package
ML20244C102	List: ML20244C101; ML20245L276;
References
	TASK-AE, TASK-E303 AEOD-E303, NUDOCS 8905050359
	Download: ML20245L276 (5)
	v • d • e

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UNIT: Surry 1 and 2 EE REPORT NO. AE0D/E303 DOCKET NO. 280 and 281 DATE: February 16, 1983 NSSS/AE: Westinghouse / Stone & Webster EVAL / CONT: D. Zukor

SUBJECT:

VALVE FLOODING EVENT l

EVENT DATE: November 28, 1981 l

SUMMARY

On November 28, 1981 routine surveillance indicated that the service water l

valve pit was flooded. The valves were subsequently declared inoperable due to a grounded valve motor. The concern was that, should these valves be inoperable, and not close when necessary there would not be sufficient water available to bring the reactor to cold shutdown following a LOCA concurrent with a total loss of offsite power.

- Analysis has shown that water is available for a minimum of 13.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months before makeup to the intake canal is necessary. If the valves are not operable electrically, they may be closed manually. In the case of a steam generator tube rupture where one must be able to go to cold shut-down to end the event, the Reactor Coolant System main loop isolation valves may be used to isolate the leaking steam generator.

The licensee has installed dikes and lights. In addition, they have upgraded maintenance procedures to ensure that the valve pits do not flood in the future.

i 1

l 8905050359 830226 PDR ADOCK 05000200 S PDR -

DfSCUSS10N On November 28, 1981, with unit 1 at 100% power, routine surveillance for flooding indicated that the valve pit which is inside the turbine building basement was ' filled with water to a depth of four to five feet. Valve MOV-SW-102A and its operator are located in this pit. Investigation by station electricians revealed the valve motor to be grounded rendering the valve inoperable. The sump high water level indicator was apparently also inoperable due to shorting.

The valve was electrically inoperable because the motor was grounded. The water which flooded the pit came from two sources: the flash evaporator (a small amount) and cleaning of the water box tubesheets to the main condenser. Although cover plates were being used over the pit, leakage from the above stated sources still occurred.

DESCRIPTION OF THE SERVICE WATER SYSTEM The service water is drawn from the circulating water system which also provides cooling water for the four main condensers. Each reactor (of this two unit site) requires 840,000 gpm of river water to meet condensing and service water needs. This is provided by eight 210,000 gpm circulating water pumps, all of which are operating under normal conditions.

The circulating water intake structure is located at the end of the river intake canal. Each circulating water pump discharge line is a 96 inch diameter steel pipe which conveys water over the embankment of and into the high-head intake canal. The water levels in the canal are controlled by the piping system within the. power station and the prevailing river level. 1 The circulating water to the condenser and the service water system is gravity fed (See Figure 1). There are separate takeoffs from the circulating water lines to supply service water to the equipment needed during an emergency.

During normal operation with two units at full power, the service water system provides water to the following:

1. Component Cooling Water System (for both units) 18,000 gpm

2. Bearing Cooling Water 24,000 gpm

3. Chilled Water Condenser 2,185 gpm

4. Control Room Air Conditioning 300 gpm

5. Charging Pump Lube Oil Coolers 90 gpm 44,575 gpm The four condensers require a total of 1,546,000 gpm of circulating water, leaving a margin of 89,425 gallons after the condensing and service water needs have been met.

The purpose of the valves in question (M0V-SW-102A and B) is to isolate service water to the Component Cooling Water System heat exchangers (only) on loss of offsite power coincident with a LOCA. This ensures that sufficient flow is available from the intake canal to the circulation spray heat exchangers, the Control Room Air Conditioning System and the Charging Pump Lube CD Coolers. Valves permitting service water flow to the component cooling heat exchangers and the bearing cooling heat exchangers may be reopened from the main control room once the alarm has cleared,in are with containment.if theyThe are considered equipment necessary.

in the pitNone consists of these of heat two exchangers valves

. with their motor operators: MOV-SW-102A and MOV-SW-102B. These valves are manufactured by Limitorque and are high class NEMA enclosed valves which l- 'should be operable underwater for short periods of time. A conductivity probe measures high or low water level in the valve pit and alarms in the

, control room. During normal operation these valves are open and allow water to flow to the component cooling water heat exchangers.- In order to achieve cold shutdown, these valves must open.

FINDINGS Case 1 Under a loss of offsite power, plus a LOCA in one reactor unit with the other unit in hot standby, the circulating water system provides water to the following systems:

1. Control Room Air Conditioning 300 gpm

2. Charging Pump Lube Oil Coolers 90 gpm 3.* Condenser (for unaffected unit) 77,300 gpm

4. Recirculation Spray Heat Exchanger 12,000 gpm 89,690 gpm

~

Case 2 In the event of a LOCA and a total loss of offsite power with the require-ment that the unit not undergoing a LOCA must also be cooled down, the following service water systems must operate:

1. Component Cooling Water System 9,000 gpm

2. Control Room Air Conditioning 300 gpm

3. Charging Pump Lube Oil Coolers 90 gpm

4. Recirculation Spray Heat Exchangers 12,000 gpm j 21,390 gpm ,

l Case 3 i

For a loss of offsite power in both units and subsequent cooldown of both {

units, circulating water must be supplied to-the following systems: j

1. Component Cooling Water System 18,000 gpm

2. Bearing Cooling System 24,000 gpm

3. Chilled Water Condenser 2,185 gpm

4. Control Room Air Conditioning 300 gpm

5. Charging Pump Lube Oil Coolers 90 gpm 6.* Condensers (throttled to 10% of full flow) 154,600 gpm 199,175 gpm

Note: Condensers are isolated when level of upper intake canal decreases to eighteen feet to conserve the ultimate heat sink.

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_3-The condenser inlet and outlet valves close when the water level in the l

canal drops to below 18 feet which is about 45 million gallons. The technical specification minimum for the intake canal volume is 25,000,000 gallons. Remotely operated valves are automatically positioned according to incident conditions. Power to these valves caa be supplied by emergency generators. Three emergency, diesel-driven, service water pumps are provided with a flow of 15,000 gpm each to supply water to the high level intake canal.

For case 1 the 25 million gallons will last for 33.6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months before makeup by the emergency service water pumps is necessary. For cases 2 and 3,19.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months and 9.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , respectively, must pass before the water in the upper level intake canal is depleted.

From information obtained from the plant, the requirement that the component cooling heat exchangers are isolated conserves water in the upper intake canal . Therefore, it appears that for cases 1 and 2 there is sufficient water provided to the recirculation spray heat exchangers for a minimum of 13.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months once the condensers isolated even if the two valves isolating the e monent cooling water system fail to close and no makeup is provided to ts.c upper intake canal by the emergency service water pumps. Although this does not represent any immediate safety concerns, it reduces the time before which the emergency service water pumps may be required i.e., from 33.6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months to 13.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months for case 1, and from 19.4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months to 13.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months for case 2.

The component cooling system must be available to go to cold shutdown. If the valves which provide service water to the component cooling heat exchangers are flooded, they will not be electrically operable, however, the valves can be manually operated by dispatching a man to the valves within minutes. In the {

case of a steam generator tube rupture, one must be able to go to cold shutdown (

to end the event. But this can also be accomplished by closing the RCS main (

loop isolation valves to isolate the leaking steam generator.

CONCLUSIONS Although the flooding of the valves in question does not appear to cause an immediate safety concern, the plant views the present flooding situation as unsatisfactory. They have attempted to reduce leakage by upgrading maintenance procedures. A similar event occurred at Unit 2 on July 28, 1982.

Dikes and handrails have now been installed around the service water valve pits, and grating covering the pits are in place. The pit is now lit to l facilitate inspections. The procedures for the water box cleaning operations i now contain cautions to remind the maintenance personnel to drain the water boxes to assure that the valve pits are not receiving water. The operating staff has been instructed to inspect the affected pit (and other pits) once per shift and immediately whenever a valve pit "high level" alann is in or suspected of being inoperable.

REFERENCE

1. Updated Final Safety Analysis Report, Surry Power Station Units 1 and 2

2. Licensee Report LER 50-280/81-075

3. Licensee Event Report LER 50-281/82-039 {

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ML20245L276

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SUBJECT:

SUMMARY

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