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REVISED REPORT - PnEVIOUS REPORT DATE 9/17/80

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LICENSEE EVENT REPORT EXHIBIT A

CONTnOL GLOCC | | I \ | | |h (PLE ASE PRINT OR TYPE ALL HFQUIREO INFORMATIONI

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!g 21 I During Mode 1 operation a surve@illance performed on the service waterensT otscnieTiOy emR:s Asa cOosecacoces

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!a ;1; i flow through the Containment Cooling Unit: indicated inadequate service i

l o I' l Lw3ter flow rate. A unit shutdown was initi ated and the coolers were in- |Io t si Lspected and found to be plugged with Asian clams. New safety analyses |

I a is 1 I were performed which showed th_at adequate flow did exist through the coolt

Ic !:1 I ers and new Technical Specifications were approved with the revised flow I

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cAuse Otseniefics ec ac=acen.e ActiOss @li ia l lThe cause of low service water flow in the containment coolers was a build-,,,,jiup of Asian ciams. The cooling units were backflushed and cleaneo and

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p i,i i acceptable flow rates verified. Other heat exchancers were inspected i

i i 131 I aqd/or tested for fouling and adeouate flowrate. Several were found to I

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~ LICENSEE EVENT REPORT

(Cont.)

have fouling and some plugging due to a buildup of silt, corrosionproducts 6nd debris. Cleaning and/or flushing was performed onthese units to remove material blocking flow. All three HPSI pumpbearing and seal cooling heat exche ger units were discovered tohave their service water supply lir. substantially plugged. Thispiping is l" carbon steel and was replaced with new material during-

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the outage. Periodic checking of the service water flow through theHPSI pump coolers will be performei during the monthly ASME Section XIpump testing. The effect upon HPSI pump operability is presentlybeing evaluated.

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i - 1* Reportabic Occurrence Report No. 50-368/80-072 Rev. 1i

2. Report Date: _11/07/80 3. Occurrence Date: 09/03/80

| 4.- racility: Arkansas Nuclear One - Unit 2j Russellville, Arkansas

5. Identification of Occurrence:i

Operation of the unit when a parameter (service water flow rate-

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through Containment Cooling Units) subject to a Limiting Conditionfor Operation (T.S. 3.6.2.3) was less conservative than the least

; conservative aspect of the Limiting Condition for Operation.Reportable per 6.9.1.8.b-

6. Conditions Prior to Occurrence:i

Steady-State Power X Reactor Power 2815 f.!Wth

Hot Standby Not Output 875 MWe

Cold Shutdown Percent -of Full Power 100 %

Refueling Shutdown Load Changes During Routine ',

s> Power Operation

Routine StartupOperation Mode 1

Routine ShutdownOperation

Other (specify) '

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7 Description of Occurrence:

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A surveillance performed on 8/20/80 revealed inadequate service waterflow through the containment cooling un. s. The surveillance. procedure

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results were inadequately reviewed by Operations supervision and the; inadequate flow rate was not detected until 9/3/80 when discovered by

the NRC resident inspector. A plant shutdown was initiated and thecontainment coolers were inspected.-

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The coolers were found to be plugged partially with live asian cl'amsand clam shells. 'These were removed and backflushed to the extent,

; possible and the coolers were reassembled. Testing was performedunder revised Technical Specifications and acceptable flow rates were

' veri fied.

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R.0.R. No. 50-368/80-072, Rev. 1

7. Description of Occurrence (continued)

Inspection of other heat exchangers in the Unit 2 service water system,

revealed some fouling or plugging of additional coolers due to a buildupof silt, corrosion products and debris (largely dead clam shell pieces).Most notable of these was the HPSI pump bearing and seal coolers. Allthese HPSI pumps were found to have substantial plugging in the small. pipe SW supply lines to the mentioned coolers. The plugging was dueto silt and corrosion products. The h" pipe on the supply and returasof these coolers was replaced. The Unit 2 Boric Acid makeup pump r]omcoolers were found to be plugged. However, analysis showed these unitsto be unnecessary due to prior design changes, thus they were simplyremoved from service. Other coolers were found to be partially fouled.All were verified clean and/or verified to have service water flow priorto return to service.

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Reportable Occurrence Report No. 50-368/80-072, Rev. I,

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| 8. Designation of Apparent Cause of Occurrence:.

,Design Procedure

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bbnufacture Unusual Service Condition X

Including Environnental,

Installation /-;

Const ructionj _ Conponent Failure(See Failure Data).

Operator;

| Other (specify)Cause of- the low service water flow through the containment coolingunits was due to a buildup of asian clams in the service water side

i of the coolers. Fouling / Plugging of additional coolers in the Unit-2 service water system due-to silt, corrosion products and debrisbuildup.+

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| 9. Analysis of Occurrenec:~

An analysis of the containment peak pressure and depressurizationrate following LOCA was performed assuming 1 containment cooling unit>

with 1250 gpm ficw. This analysis was used to substantiate a TechnicalSpecification change and also indicated that the flow rates observedduring routine surveillances would have been acceptable from a public*

health and safety viewpoint had a LOCA occurred. The.effect of littleor no service water flow through the HPSI pump bearing and seal coolersis being evaluated presently. Other fouling observed is judged to4

have been acceptable for operability of the other cooling units..

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Reportable Occurrence Report do. 50-368/80-072 Rev. I

10. Corrective Action:

The containment cooling units were flushed, backflushed and cleaned,then reassembled and acceptable flow rates verified. All other heatexchangers were tested and/or inspected to verify acceptability.The Boric Acid Makeup pump room coolers were removed from servicepermanently.s The h" piping was replaced on the service water supplyand returns on the HPSI pump bearing and seal coolers. Other unitswere cleaned as necessary and flushed to verify cleanliness. Thesurveillance frequency was increased on the containment cooling unitsand concurrent chlorination initiated to kill clam larva. Periodicinspection of other heat exchangers is planned.

11. Failure Data:

No Similar Occurrences.

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