05000245/LER-1981-028, Forwards LER 81-028/03L-0.Detailed Event Analysis Encl

Forwards LER 81-028/03L-0.Detailed Event Analysis Encl

ML20031F876
Person / Time
Site:	Millstone
Issue date:	10/07/1981
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20031F877	List: 05000245/LER-1981-028, Forwards LER 81-028/03L-0.Detailed Event Analysis Encl 05000245/LER-1981-028-03, /03L-0:on 810811 During Gas Turbine Black Start Test,Generator Output Breaker Failed to Close,Preventing Output Voltage on Gas Turbine.Caused by Oxidation of Contacting Surfaces of Potentiometer.Surfaces Burnished
References
MP-1-1904, NUDOCS 8110200504
Download: ML20031F876 (3)

LER-1981-028, Forwards LER 81-028/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2451981028R00 - NRC Website

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October 7, 1981 MP-1-1904

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bL l Mr. Ronald C. Haynes OCT 19 931..-

Director, Region I Office of Inspection and Enforcement

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f King of Prussia, Pennsylvania 19406 Dir

Reference:

Provisional License No. DPR-21 Docket No. 50-245 Reportable Occurrence R0-81-28/3L e

Dear Mr. Haynes:

This letter forwards the Licensee Event Report for Reportable Occurrence R0-81-28/3L required to be submitted within 30 days pursuant to the requirements of the Millstone Unit 1 Technical Specifications, Section 6.9.1.9.b.

An additional three copies of the report are enclosed.

The Plant Incident Report (PIR) was inadvertently misplaced and therefore delayed the completion of this Reportable Occurrence within the 30 days time limit.

Yours truly, NORTHEAST NUCLEAR ENERGY COMPANY anrdf E. J. Mroczka Station Superintendent Millstone Nuclear Power Station EJM/TST:bjo

Attachment:

LER R0-81-28/3L cc:

Director, Office of Inspection and Enforcement, Washington, D.C. (30)

Diractor, 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

'3110200504 811007 PDR ADDCK 05000g S

ATTACHMENT TO LER 81-28/3L NORTHEAST NdCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION - UNIT 1 PROVISIONAL LICENSE NUMBER DPR-21 DOCKET NUMBER 245 Identification of Occurrence Operation in a degraded mode permitted by a limiting condition for operation occurred when the Gas Turbine Generator failed to start.

Conditions Prior to Occurrence Prior to occurrence the unit was in the start up mode with reactor pressure at 158 psig.

Description of Occurrench On August 11, 1981, at 0645, while performing Gas Turbine Black Start Test, the generator output breaker failed to close thereby preventing an output voltage on the machine.

Technical Specification 3.9.A.2 requires the Diesel and Gas Turbine (emergency power sources) to be operable at all times.

A) parent Cause T1e generator output breaker failed to close due to a malfunction of the automatic voltage regulator which prevented the generator output voltage from reaching its rated value. The malfunction was caused by oxidation of the contacting surfaces of a potentiometer which resulted in loss of circuit continuity.

Analysis of Occurrence The voltage regulator cabinet which houses all the electrical and electronic componets is in an uncontrolled environment, that is, it is vented for cooling to the Gas Turbine building.

The Gas Turbine building is vented directly to th9 outside via large louvered openings through the walls. While the voltage regulator cabinet does have strip heaters within to maintain the cabinet temperature slightly above the Gas Turbine building ambient, it is obvious by the presence of oxidation products on many metal parts that.it is insufficient to preclude moisture intrusion.

Failure of the Gas Turbine to accelerate upon receipt of a black start signal did not create a condition which had not been analyzed.

The Gas Turbine is one out of two emergency power sources that are utilized for engineered safeguard systems.

In an actual emergency condition where emergency core cooling systems are required and a loss of off-site power accompany it, the Gas Turbine and the Diesel provide emergency power.

Each power source is indeoendent of the other, thereby allowing the Gas Turbine or Diesel to solely provide emergency power if the other fails.

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Corrective Action

The contacting surfaces of the potentiometer were burnished to remove the oxide coating.

The potentiometer was then cycled while monitering continuity.

This was repeated several times until continuity was maintained throughout the full travel of the variable arm. Additionally a new potentiometer will be ordered and installed when it becomes available.

3 L__.-