ML20085E758

Second Interim Deficiency Rept Re Clogged Cooling Water Lines to RHR & Core Spray Pump Motor Bearing Coolers. Initially Reported on 760422.Corrective Actions to Be Determined After Final Fix Proposals Evaluated

ML20085E758
Person / Time
Site:	Browns Ferry
Issue date:	08/23/1976
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20085E756	List: ML20085E754 ML20085E758
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8308160559
Download: ML20085E758 (5)

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. August 23, 1976 Mr. Norman C. Moseley, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II - Suite 818 230 Peachtree Street, NW.

Atlanta, Georgia 30303 i

Dear Mr. Moseley:

BROUNS FERRY NUCLEAR PLANT UNIT 3 - REPORTABLE DEFICIENCY -

CLOGGED COOLING WATER LINES TO RHR AND CORE SPRAY PUMP MOTOR

BEARING COOLERS - IE CONTROL NO. H01309F2 Initial report of the subject reportable deficiency was made to G. R. Klingler, NRC-IE, Region II, on April 22, 1976, and was followed by our May 24, 1976, letter, J. E. Gilleland to N. C.

Moseley. Enclosed is our second interim report concerning this deficiency. A final report will be' prepared once a final fix has been implemented.

Very truly y9urs, y

J. E. Gilleland Assistant Manager of Power j Enclosure CC (Enclosure):

Dr. E. Volgenau, Director

. Office of Inspection and Enforcement

$ U.S. Nuclear Regulatory Co= mission Washington, DC 20555 l

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An Equal Opportunity Employer

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a n .. EHCLOSURE . .

BROWNS FERRY NUCLEAR PLANT UNIT 3 Clogged ^ Cooling Water Lines to RHR And Core Spray Pump Motor Bearing Coolers DDR 230 Second Interin Report On April 22, 1976, an initial report was made by telephone to NRC-OIE Inspector G. R. Klingler by T. W. Barkalow and S. H. Mindel. The report was made in accordance with_10CER50.55(e) . Subsequently, a written interim report on this deficien'cy was submitted to Norman C. Moseley (NRC-0IE) from J. E. Gilleland (TVA). This is the second interim reporc on the deficiency. A final report will be submitted when final plans to correct the deficiency are completed.

Description of Occurrence While conducting preoperational test TVA-4, the actual flow rates in the emergency equipment cooling water (EECW) lines to one RHR pump seal heat exchanger for unit 1, one core spray room cooler for unit 2, and 11 of the 12 core spray pump motor bearing coolers on all three units were found to be less than the flow rates required by the test. The supply and dis-diarge piping to core spray pump motor thrust bearing oil coolers 2A and 2C were removed and examined. A heavy deposit of mud and scale was found to be encrusted on the entire inner circumference of the piping.

The resulting evaluation of this system has concluded that the flow rates through the core spray pump motor thrust bearing coolers would be marginal even if the system piping were cican. The original calculations used to design the system assuced zero pressure drop across the core spray pump motor thrust bearing oil coolers based on information supplied by General Electric (CE). Since 70 psi differential pressures were measured across the oil coolers at design flows, GE was contacted to provide information regarding the design of the oil coolers. GE has verbally indicated that the oil cooler consists of a substantial length (approxicately 63 feet)

- of 3/8-inch disceter copper tubing.

Cause of Deficiency The EECW system is only used during tests or when the equipment it services is operated. Therefore, the cooling water lines contain stagnant or very low flow of water for long periods of time. Since the source of EEC1 is raw water from Wheeler Reservnir, it is currently believed that the stagnation

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1eads to scaling- of the pipe, settlement of suspended solids, and clogging in sections of the lines at the lower elevations. Investigations are con-tinuing to determine the definite cause of the scaling. An analysis of the scale found in the lines, performed by the plant laboratory, has deten:ined l

. that the scale consists of 71.1 percent iron oxide, 24.5 percent silicon I oxide, and 4.4 percent unspecified material. The EECW systea does have strainers, but they are inef fective in dealing with very small particles in the silty water. Also, some lines contained a few Asiatic clans. This indica'tes that some flow reduction may be due to blockage of the flow path by clams, but it is not believed to be the major cause of flow reductior.

The first interim report implied that the system had been periodically chlori nated as a means to control the clam population. This statement has been found to be incorrect; the EECW system has never been chlorinated as a syster Also, as described in a previous paragraph, the system had been designed on the assumption of no pressure drop across the core spray pump motor thrust bearing oil cooler.

Safety Implications The EECW system provides cooling water to the standby diesel generators, RHR and core spray equipment room environmental coolers, RHR pump seal coolers, and core spray thrust bearing coolers. Eleven of 12 core spray thrust bearin cooler lines, one RHR pump seal cooler line, and one core spray equipment rec .

environmental cooler line had ' inadequate flow. These lines are among the smallest lines in the system and, therefore, are the most sensitive to obstre :

tions. Complete plugging of these lines would prevent cooling water from circulating through that part of the system.

If all cooling water were prevented from entering a core spray pump motor thr bearing oil cooler, the temperature of the oil would increase sharply. Howev even at the resultant elevated temperature, the oil would retain its lubricat properties for two months. Instrumentation is available in the control room indicate the torus temperature and the core spray pump thrust bearing temperc These indicators and other instruments can verify for the plant operator whether each cooler or heat exchanger is receiving an adequate flow of coolin -

water. Thus, an operator will knov if the equipment is close to overheating and can take appropriate action. ..

. If all EECU cooling water were prevented from entering an RER pump seal heat exchanger, the RHR pump would not be endangered unless the pump seal cooling process water temperature increased to above 212 degrees F. The pump seal cooling process water is taken from the water being pumped by the RHR pump.

This water can increase to 212 degrees F. or above when the reactor is in the ;

shutdown cooling code. However, it is not necessary to place the RHR system into the shutdown cooling mode when the water temperature is above 212 degree.

as other equipment may be used for short-term cooling following a shutdown.

Therefore, loss of cooling water to either a core spray pump motor thrust bearing oil cooler or an RHR pump seal heat exchanger dous not pose an immedi danger to the plant or to the health and safety of the public.

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Description o f Corrective Action -

The lines to the fiotor thrust bearing coolers for core spray pumps 2A and 2C were removed and replaced with new pipe. The coolers were then back-

'- flushed. Although the flow through the coolers did increase, the original {

design requirement was still not met. The first interim report stated that adequate flow was ach.ieved in all but one core spray pump motor thrust Learing_ cooler. This~ s'tatement was incorrect in that required flow was achieved in'only one core spray pump motor thrust bearing cooler. Since 11 out of' 12 of the core spray pump motor thrust bearing oil coolers aid not meet the 4 gpm requirement, all the 1-inch supply and discharge lines will be~ replaced. GE was contacted regarding the 4 gpm flow rate requirement They replied that 3 gpm would provide adequate cooling if the inlet water temperature was not allowed to exceed 95 degrecs F. Since the inlet tempera-ture will never exceed 95 degrees F due to other operating limits, the required flow rate has been lowered to 3 gpm. It is anticipated that replacement of the 1-inch lines will increase the flow rate to above 3 gpm.

If the flow rate is not increased this amount, the 2-1/2-inch discharge line from the cocmon discharge of the oil coolers and the core spray room coolers also will be replaced.

Since the pressure dif ferential measured across the core spray room cooler that failed the preoperational test falls 'in the range predicted, the supply and discharge lines to this one cooler will be cleaned. If the ficw require-ments cannot be met af ter cleaning, consideration will be given to replace-ment of the piping. The 2-1/2-inch supply line and 2-inch inlet line from the 18-inch main header to the cooler inlet will be cicared or replaced if necessary. The 2-inch discharge line and 2-1/2-inch downstream line from the cooler discharge to the j unction with the 4-inch line from the RllR components also will be cleaned or replaced.

Since only one of the'5HR pump seal heat exchangers did not pass the preoperational test, it is being assumed that the probica lies within the heat exchanger loop itself and is not con: mon to the other heat exchangers.

As a first step, heat exchanger 1C will be opened and inspected for tube blockage. If the design flow requirement of 4 gpm is not met by seal heat exchanger 1C af ter c1 caning, both the 1-inch supply and discharge lines foc. the heat exchanger will be replaced.

In addition to the above, the following general actions will be taken:

1. All valves vill be inspected, c1 caned, and repaired if necessary.

2. When the existing piping is being replaced, representative sacples will be tagged and saved _ as archival material. Documentation will include the exact location from which the piping was taken.

3. During the interim period until a final fix is impicnented, more extensive testing and =onitoring will be required. Surveillance testing of the EECW system will be required at three-month

- intervals with the minimum testing being the verification of design flow to all coeponents of the EEC;l system. Documentation o f these tests will be available at the plant.

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Means Taken to Prevent a Recurrence TVA is presently in the process of determining the exact cause of the corrosion and deposit buildup in the EECW lines and is evaluating several proposals for a final fix. Due to the complexity of the prcblem, a final proposal for a fix cannot be made at this time. TVA commits to submitting an interim report every three months until this deficiency is completely resolved. Also, an interim report will be submitted when a final fix is identified and a final report will be submitted once the final fix has

- been implemented.

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go' UT% () 830 Power Building Y

TENNESSEE VALLEY AUTHO

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• 16-19 "$ FD 2 41976 ,p COP's Mr. Norman C. Moseley, Director '

Office of Inspection and Enforcement U.S. Nuclear Regulatory Co m ission Region II - Suite 818 230 Peachtree Street, L'.

Atlanta, Georgia 30303

Dear Mr. Moseley:

BROWNS FERRY NUCLEAR FIRNT UNIT 3 - REPORTABLE DEFICIENCY -

CLOGGED COOLING WATER LINES TO RER AND COPI SPRAY PUMP -

POTOR BEARING COOLERS e

Initial report of the subject reportable deficiency was made to G. R. Klingler, NRC-IE, Region II, on April 22, 1976. In co=pliance with paragraph 50.55(e) of 10 CFR Part 50, we submit the enclosed interic report of the deficiency. A final report will be submitted when plans to correct this deficiency are conpleted and -

approved.

Very truly yours, 1 - r 7 L , .,

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8, g J. E. Gilleland Assistant Manager of Poweri Enclosure CC (Enclosure):

Dr. E. Volgenau, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Comnission Washington, DC 20555 .

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An Equal Opportunity Employer

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O ENCLOSUPI o  ;

BRO,lI;S FERRY KUOZAR PLA!!T UNIT 3 CLOGGED C00LIN3 WATER LINES TO RE AND CORE SFRAY PJM? MOTOR EARI!!3 C00ERS

. DDR 230 INTEREi PSPORT ,,

On April 22, 1976, an initial report was made by telephone to 130-0IE Inspector, G. R. Klinger, by T. W. Earkalow and S. H. Mindel. The report was cade in co pliance with 10CFR50 55(e). This is an interis report.

A final report vill be subnitted once final plans to correct the deficiency are co=pleted.

Description of Occurrence _

While conducting preoperational test TVA !+, the actual flow rates in the emergency equip =ent cooling water (EECW) lines to the RER and core spray punp notor bearing coolers were found to be below those required by the test. An investigation revealed these lines to be clogged with mud and scale. Thelinesinvolvedhaddiametersofeither3/8inchor 1 inch.

Cause of the Deficiency The EECW system is only used during tests or when equipment it services is operated. Therefore, the cooling water lines contain stagnant water for long periois of time. Since the ECW source is r=w water from Wheeler Reservoir, the sta6 nation leads to settlement of suspended solids and clogging in sections of lims at the lower elevations. The syste=

does have strainers, but they have been ineffective in dealing with silty water. Also, a few lines contained asiastic clams which were all of about the same size. This indicates that they may be able to grow in the system between flushings with chlorinated water.

Safety Trolications The EECW system provides cooling water to the standby diesel generators, RER and core spray equipment room environmental coolers, RER pu=p seal coolers, and core spray thrust bearing coolers. Lim s to the~ 1atter two coolers were found to be clogged. These lines are the smallest lines in the system and, therefore, are the easiest to clog. Ccx:plete plugging of these lines would prevent cooling water from circulating through this part of the system. However, . temperature measurements indicated in the control room verify whether each cooler or heat exchanger in the affected unit area is receiving adequate flow of cooling water. Inadequate flow could eventually lead to failure of the core spray pumps and the RHR pumps.

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Description of Corrective Action j' All the check valves in the clogged sections of the lines were removed and thoroughly cleaned. The lines were then backflushed through the coolers. . Tests conducted after the lines were reassembled shcsed adequate flow in all but one line to a core spray pu=p noter bearing cooler. ~

This line will be disassembled and reflushed to remove any remaining blockage.

Means Taken to Prevent a Eeeurrence_

Final plans to correct this deficiency have yet to be completed and .

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