05000245/LER-1982-003, Forwards LER 82-003/01T-0.Detailed Event Analysis Encl

Forwards LER 82-003/01T-0.Detailed Event Analysis Encl

ML20041E614
Person / Time
Site:	Millstone
Issue date:	03/03/1982
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20041E615	List: 05000245/LER-1982-003, Forwards LER 82-003/01T-0.Detailed Event Analysis Encl 05000245/LER-1982-003-01, /01T-0:on 820217,while Switching to Isolate North 345 Kv Line Circuit Switcher 15G-2T-6 Faulted Phase a to B Causing Fire to Circuit Switcher.Caused by Interrupter Contact within Circuit Switcher Failed in Open Position
References
MP-1-2014, NUDOCS 8203110171
Download: ML20041E614 (3)

LER-1982-003, Forwards LER 82-003/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
2451982003R00 - NRC Website

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Mr. Ronald C. Haynes

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Regional Admisiistrator, Region 1 Office of Inspection and Enforcement V

U. S. Nuclear Regulatory Commission 631 Park Avenue cv King of Prussia, Pennsylvania 19406 tu

Reference:

Facility Operating License No. DPR-21 Docket No. 50-245 Reportable Occurrence R0-82-3/lT

Dear Mr. Haynes:

This letter forwards the Licensee Event Report for Reportable Occurrence R0-82-3/lT required to be submitted within 14 days pursuant to the requirements of the Millstone Unit 1 Technical Specifications, Section 6.9.1.8.i.

An additional three copies of the report are enclosed.

Yours truly, NORTHEAST NUCLEAR ENERGY COMPANY

/ E. J. Mroczka Station Superintendent Millstone Nuclear Power Station EJM/TST:mo

Attachment:

LER R0-82-3/lT cc: Director, Office of Inspection and Enforcement, Washington, D.C. (30)

Director, Office of Management Information and Program Control, Washington, D. C. (3)

U. S. Nuclear Regulatory Commission, c/o Document Management Branch, Washington, D. C.

20555 8203110171 820303 DR ADOCK 050002 g6.4

ATTACHMENT TO LER 82-3/1T NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION - UNIT 1 PROVISIONAL LICENSE NUMBER DPR DOCKET NUMBER 50-245 Identification of Occurrence Performance of systems that required corrective action to prevent operation in a manner less conservative than assured in the Safety Analysis Report and accident analyses occurred when the 345 KV line 383 and the Reserve Station Service Transformer were automatically isolated because of a faulted circuit switcher.

Conditions Prior to Occurrence Prior to occurrence the unit was operating at a steady state power level of 100 percent.

Description of Occurrence On February 17,1982, at 0657 hours0.0076 days <br />0.183 hours <br />0.00109 weeks <br />2.499885e-4 months <br />, while switching to isolate the North 345 KV line, circuit switcher 15G-2T-6 faulted phase A to B causing a fire to break out in the circuit switcher.

The faulted circuit switcher was cleared by operation of the 383.line relaying which automatically disconnected the line and the Reserve Station Service Transformer.

Technical Specification 3.9.B.2 allows ruactor operation provided both emergency power sources are operable and the Isolation Condenser System operable when incoming power is not available from any 345 f.V line. The Diesel Generator and Gas Turbine were started accordingly.

Apparent Cause of Occurrence It is conjected that an interrupter contact within circuit switcher 15G-2T-6 failed unknowingly in an open position on a previous operation. With the North Bus isolated, full line current could not flow through the contact and therefore passed through the shunt resistor. This continuous flow through the shunt resistor caused overheating and electrical faulting of circuit switcher 15G-2T-6.

Analysis of Occurrence Normally three 345 KV lines (383, 371 and 348) are available to provide emergency power to the plant when the reactor is operating.

In the event that all 345 KV lines are out of service continued reactor operation is permitted provided both on site emergency power sources are operating with adequate fuel.

Two operational power sources provide an adequate assurance of emergency power availability under these circumstances.

In addition the Isolation Condenser System is required to be operable as a standby heat removal system.

ATTACHMENT TO LER 82-3/1T NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION - UNIT 1 PROVISIONAL LICENSE NUMBER DPR-21 DOCKET NUMBER 50-245

Corrective Action

Circuit Switcher 15G-2T-5 was isolated to facilitate replacement of the interrupter heads and to restore switching to re-energize the Reserve Transformer.

In the future personnel will visually observe the manual flag at circuit switcher 15G-2T-6 to ensu.'e the interrupter contacts are closed prior to each closing operation.