ML20004C351: Difference between revisions

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{{Adams
#REDIRECT [[05000298/LER-1981-005, Forwards LER 81-005/03L-0.Detailed Event Analysis Submitted]]
| number = ML20004C351
| issue date = 04/16/1981
| title = Forwards LER 81-005/03L-0.Detailed Event Analysis Submitted
| author name = Lessor L
| author affiliation = NEBRASKA PUBLIC POWER DISTRICT
| addressee name = Seyfrit K
| addressee affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
| docket = 05000298
| license number =
| contact person =
| document report number = CN55810222, NUDOCS 8106030233
| package number = ML20004C352
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE, UTILITY TO NRC
| page count = 2
}}
 
=Text=
{{#Wiki_filter::.  .
1 M    /                                                              Coof ER NUCLEAR STATaoN 9          Nebraska Public Power District                    "' *            "
                                                                            "A"E, 3 R M Gh"."^A" "'''
CNS 10222                                                                            .R April 16, 1981                                                              .
                                                                                      $'\          *y Sh Mr. K. V. Seyfrit, Director                      !Y, 3LU
                                                                ., ~ '> n ~
                                                                                          ^ '
                                                                                              .\%          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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