ML19326B402

LER 78-009/01T-0:on 780413,B&W Advised Util That Results of 0.04 Ft Squared RCS Pump Discharge Break Analysis Unacceptable.Caused by ECCS Analysis re-evaluation Performed for Newer B&W Plants

ML19326B402
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/27/1978
From:	Enos T ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19326B397	List: ML19326B396 ML19326B402 ML19326B406 ML19326B409 ML19326B416
References
LER-78-009-01T, LER-78-9-1T, NUDOCS 8004150768
Download: ML19326B402 (4)

Text

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(g V l-Reportable Ocewrey.ce Report No. 50-313/78-9

2. Report Date: April 27, 1978 3. Occurrence Date: April 13, 1978 4 Facility: Arkansas Nuclear One-Unit 1 Russellville, Arkansas 72801 S. Identification of Occurrence:

Results of an analysis of a 0.04 f t2 RCS pump discharge break which had not been previously analyzed and which showed unacceptable results.

6. Conditions Prior to Occurrence:

Steady-State Power _ Reactor Power 0 MWth Hot Standby Net Output 0 MWe Cold Shutdown y Percent of Full Power 0 '5 Refueling Shutdown Load Changes During Routine g

Powrer Operation

,j Routine Startup Operation Routine Shutdown "

Operation Other (specify) 7.

Description of Occurrence:

We were notified on Agril 13, 1978 by our NSSS vendor of the rasults of an analysis of a 0.04 f t- RCO pump discharge break which had not been previously analyzed and which showed unacceptable results. The unacceptable results occur af ter apprentuately 1700 seconds when one

, acsumes that one high pressure injection train is working and that '

50% of the flow from that EPI pump is not reaching the core due to flow out of the break. Additional analyses have been perforged by B&W for break sizes of 0.3, 0.2, 0.15, 0.13, 0.1, 0.07, 0.04, ft which show that the worst case break is 0.13 f t2, i n m

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d Reportable Occurrence Report No. 50-?13/78-9

8. Designation of Apparent Cause of Occurrence:

D sign Procedure Manufacture Unusual Service Condition Including Environmental Installation / ~

Construction Component Failure (See Failure Data)

Operator Other (specify) X Reevaluation of ECCS analysis as a result of analysis results performed for'3&W's newer generation plants. Due to the small probability of this very specific occurrence with concurrent loss of offsite power and failure of a diesel generator there was no significant hacard to

, the health and safety of the public.

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Analysis of Occurrence:

Without proper cprator action 10CFR50/46 tmits could be exceeded for a limited range of very small break sizes in a specific small L

portion of RCS piping.

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Reportable Occurrence Report No. 50-313/78-9

10. Corrective Action:

Operator action will be taken in the event the Postulated Small

' Break LOCA should occur. This action will consist of opening the cross connect valve between the two main headers of high pressure injection and opening two isolation valves.

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11. Failure Data:

None i

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