ML19210A173
| ML19210A173 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/25/1975 |
| From: | Arnold R METROPOLITAN EDISON CO. |
| To: | |
| References | |
| GQL-1741, NUDOCS 7910240896 | |
| Download: ML19210A173 (4) | |
Text
sRLYURT UY MI.U.tMAL UCCUiCC.NCt; M U/Ud it.CiULIE NRCbia BUTION FOR PART 50 DOCKET 1
TERI AL (TEMPORARY FORM) 133 9 CONTROL NO:
FILE: INCIDE!E REPORT FILI FROM: Met. Edison Co.
DATE OF DOC DATE REC'D LTR TWX RPT OTHER Reading, Pa.
19603 o_e s.-,,a 11-21-75 11-25-75 XX TO:
ORIG CC OTHER SENT AEC PDR W ~.J Z NRC 1 sign $d SENT LOCAL PDR XX CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:
XXX 1
50-2Ao DESCRIPTION: Ler submitted as A0-50-289/75-40 ENCLOSURES:
on 11-12-75 re stuck voltage relays coni acts of the "A" diesel gnerator....
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SPELS W/ Copies W/ Copies W/ Copies kV/ Copies KNIEL (L)
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METROPOLITAN EDISON COMPANY POST OFFICE Box 542 R E ADING, PENNSYLV ANI A 19603 TELEPHONE 215 - 929 2601 November 21, 1975 GQL 17kl Director of IIuclear Reactor Regulation U. S. Nuclear Regulatory Ccmission Washington, D.C.
20555
Dear Sir:
Docket No. 50-289 Operating License No. DFR-50 In accordance with the Technical Specifications of our Three Mile Island Nuclear Station Unit 1 (TMI-1), we are reporting the folleving abnertal occurrence.
(1)
Report Number: A0 50-289/75 ho 9
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(2') Report Date:
Novenber 21, 1975
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'0 (To) Occurrence Date: November 12, 1975 7
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Facility: Three Mile Island Nuclear Station Unit 1
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Identificatien of Occurrence:
Title:
Stuck Voltage Relays Contacts of the "A" Diesel Gene. _
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Type: An abner =al occurrence as defined by the Technical Specificatiens,
parapaph 1.3d, in that the stuck voltage relays contacts threatened to cause an Engineering Safeguards feature or systen to be incapable of perfor=ing its intended functions.
(5)
Conditions Prior to Cccurrence:
Pcwer:
Core: 1005 Elec..
Sho MWe (Gross) 6 RC Flow: 139 x 10 lbs/hr.
RC Pressure: 2155 psig} RC Tenp.. 579 F FRZR Level-. 250 in. blN PRZR Temp. 65Cc7
. (6) Descriptien of Occurrence: Cn November 12, 1975, the three up to voltage relays on the 1A Diesel Generatcr were found to have stuck centacts. The stuck contacts resulted in the relays remaining in the energized conditien even though the 1A Diesel Generator was s hut down. This condition could have caused prenature closure of the 1A Diesel Generator Ereaker in the event the generater vaa required to autcmatically start and energize the safeguards bus. The 1A Diesel Generater had last been run on November 6,1975 and the relay contacts had apparently been stuck since that time. I:nedianely, the stuck voltage relays on the 1A Diesel Generator vere manually reset and the relays en the 13 Diesel Generator vere inspected and verified to be reset. (7) Designatien cf Apparent Cause of Occurrence: The cause of this occurrence has been de ; ermined to be raterial/ design in that the voltage relay contact pits sli :htly due to frequent operatien. In the system's present design, each volttge relay has a separate auxiliary relay. When the Diesel Generator voltage increases above setpoint, the contact in the voltage relay closes, causing the auxiliary relay to enercize. Conversely, when the voltage goes belev setpoint, the voltage relay contact should open alleving the auxiliary relay to de-energize. Ecvever, the slight pitting resulted in sporadic relay contact stickings. (8) Analysis of Occurrence: It has been determined that this occurrence did not constitute a threat to the health and safety of the public in that: a. The failure mcde of the relays was such that generator breaker closure was permitted. It is unlikely that the relay problem, in itcelf, vculd have resulted in any failure if autctatic generater start and autecatic breaker closure had been required. The generator veuld probably have operated properly because field flashing takes place while generator is cc=ing up to speed. Adequate voltage is normally present when the generator reaches rated speed. The frequency relays vculd have prevented breaker closure until generator was up to speed. In additicn, the frequency relays require voltage to operate, although, they would allev the breaker to close at a lover than desired vcitage. b. In the event that the la Diesel Generator had been prevented from operating properly, the 13 Diesel Generator was available. (9) Corrective Action: In addition to the i=nediate action described abi e, long term corrective actions are as folicvs: a. A design change vill be submitted to generatien engineering to permanently solve the prcblem. 1476 154
Until a satisfactcry sclution is cbtained, the relays vill be b. inspected for proper condition each time the diesel generators are cperated. A temporary procedure change has been implementel to assure that this inspection is acccmplished. (10) Failure Data: Diesel Generator lA Relay Desi gnations : 59-1, 59-2, 59-3 Up to Voltage Relays Voltage Relay Type: Westinghouse CV-7 Style #187552hA Auxiliary Relay: Westinghouse MG-c Si=ilar Occurrences: None Sincerely, l R. C. Arnold Vice Presiden'; RCA:JMC :t as File: 20.1.1 / T.7.3.5.1 cc: Office of Inspection & Enforcement, Region 1 1476 \\be3}}