ML20004C351
| ML20004C351 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 04/16/1981 |
| From: | Lessor L NEBRASKA PUBLIC POWER DISTRICT |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML20004C352 | List: |
| References | |
| CN55810222, NUDOCS 8106030233 | |
| Download: ML20004C351 (2) | |
Text
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1 M / Coof ER NUCLEAR STATaoN 9 Nebraska Public Power District "' * "
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CNS 10222 .R April 16, 1981 .
$'\ *y Sh Mr. K. V. Seyfrit, Director !Y, 3LU
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.\% k' U.S. Nuclear Regulatory Commission / /4 d 10ffice of Inspection and Enforcement D Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011
Dear Sir:
This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on March 20, 1981. A licensee event report form is also enclosed.
Report No.: 50-298-81-25 Report Date: April 16, 1981 Occurrence Date: March 20, 1981 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:
A condition which lead to operation in a degraded mode permitted by the limiting condition for operation established in Section 3.12.B.2 of the Technical Specifications.
Conditions Prior to Occurrence:
The reactor was operating at a steady state power level approx-imately 95% of rated thermal power.
Description of Occurrence:
During Surveillance Procedure S.P. 6.3.16.3, Reactor Building Closed Cooling Water pump 1D tripped when started.
Designation of Apparent Cause of Occurrence:
A minimally sized fuse was installed in the control circuit of RBCCW pump 1D.
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Mr. K. V. Seyfrit April 16,-1981-Page 2.
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' Analysis of Occurrence:
l The Reactor Building Closed'Coolir.g Water. System (RBCCW) consists l
of 'two independent closed loups. = It:is designed with sufficient l
' redundancy so_that no single active system component failure nor i any single active component failure in any other plant- sys tem can
-Prevent it from achieving its safety objective. Each loop has two
[- pumps discharging to one reactor building cooling water heat ex-changer. The two Toops can be' interconnected through crosstie equipped with isolation valves. .Either: reactor building closed cooling water loop has sufficient capacity with one puni operating to transfer the essential services design cooling load-during-postulated-transient or accident conditions.
Each-RBCCW pump'has a size 4 motor-starter protected by a control power fuse.. The undersized control power fuse (3 amp) blew when
. pump,.lD was started,which made' the pump inoperable for about 6 ,
hours. 'The subject motor starters were initially supplied with a 4 amp style AB fuse. The AB style fuse has been discontinued by the fuse manufacturer and style ABC has been supplied. Style ABC is available in 1, 2,-3, 5, 6,.. 20 amp capacity. It is apparent that the original 4. amp style AB fuse had been replaced with a 3 any style ABC fuse. This was'a conservative action however and the 3 amp fuse on occasion failed during the instantaneous control circuit in-rush current during' motor starter actuation.
Redundant systems were available and operable. This occurrence presented no adverse consequences from the standpoint of public health and safety.
Corrective Action:
A spare size 4 motor starter was bench tested, its in-rush current ;
measured, and was found to be the same as the measured in-rush I current on the subject matcr starter. Based on the motor starter manufacturer recommendation and a revised fuse specification sheet, a 5 amp control power fuse was specified'for installation in the subject size 4 motor starter. Control power fuses in all size 4 motor starters for ECCS components were checked and undersized fuses replaced. Equipment history did not reveal similar problems with control fuses in sizes 1, 2, & 3 motor starters for ECCS equipment.
Sincerely, L. C. Lessor
' Station Superintendent Cooper Nuclear Station LCL:cg Attach.
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