05000245/LER-1981-006, Forwards LER 81-006/03L-0.Detailed Event Analysis Encl

Forwards LER 81-006/03L-0.Detailed Event Analysis Encl

ML20008F920
Person / Time
Site:	Millstone
Issue date:	05/06/1981
From:	Mroczka E NORTHEAST UTILITIES
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20008F921	List: 05000245/LER-1981-006, Forwards LER 81-006/03L-0.Detailed Event Analysis Encl 05000245/LER-1981-006-03, /03L-0:on 810417,one of Two Ventilation Duct Radiation Monitors Was Found to Trip Outside Allowable Range.Caused by Setpoint Drift Due to Failed Sensor Converter.Converter Replaced
References
MP-1-1766, NUDOCS 8105120334
Download: ML20008F920 (2)

LER-1981-006, Forwards LER 81-006/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2451981006R00 - NRC Website

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May 6, 1981 MP-1-1766 S

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Mr. Boyce H. Grier

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Director, Region 1 9

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Reference:

Provisional License DPR-21

1. %A: di Docket No. 50-245 Reportable Occurrence R0-81-06/3L

Dear Mr. Grier:

This letter forwards the Licensee Event Report for Reportable Occurrence R0-81-06/3L required to be submitted within 30 days pursuant to the l

requirements of the Millstone Unit 1 Technical Specifications, Section 6.9.1.9.a.

An additional three copies of the report are enclosed.

Yours truly, NORTHEAST NUCLEAR ENERGY COMPANY

&3 J. Mroczka Station Superintendent Millstone Nuclear Power Station EJM/MJB:jf l

Attachment:

LER R0-81-06/3L t

Director, Office of Inspection and Enforcement, Washingtor.,

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D. C. (30)

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

U. S. Nuclear Regulatory Commission, c/o Dccument Management Branch, Washington, D. C. 20555 4

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ATTACH:!ENT TO LER 81-06/3L NORTHEAST NUCLEAR ENERGY COP.PANY MILLSTONE NUCLEAR POWER STATION-UNIT 1 PROVISIONAL LICENSE tNMBER DPR-21 DOCKET NUMBER 50-245 IDENTIFICATION OF OCCURRENCE A reactor protection system instrument ser. ting was-found to be less conservative than that established by the technical specifications, but did not prevent the fulfillrcent of the functional requirements of the affected system.

CONDITIONS PRIOR TO THE OCCURRENCE Prior to the occurrence the plant was shut down for a planned refueling outage.

DESCRIPTION OF OCCURRENCE On April 17,1981 at 0430 hours0.00498 days <br />0.119 hours <br />7.109788e-4 weeks <br />1.63615e-4 months <br /> while performing routine surveillance, Reactor Building Exhaust Duct and Refuel Floor High Radiation Monitor Functional Test, one of the two ventilation duct radiation monitors was found to have a trip set point of 14 tR/hr.

Technical Specfications require that these radiation monitors be set to trip at 11 mR/hr.

The radiation conitoring system was manufactured by the General Electric Company, and has a range of 0.1 mR/hr to 1000 cR/hr.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE Failure of the ventilation duct radiation conitor to trip at its cesired set point was attributed to setpoint drift to failure of the radiation monitor sensor converter.

ANALYSIS OF OCCURRENCE The two radiation monitors located in the reactor building ventilation exhaust duct are provided to initiate isolation of the reactor building ventilation system and operatio'n of the standby gas treatment system upon receipt of an Failure of the radiatinn conitor exhaust duct radiaticn done rate of 11 mR/hr.

in question to trip at the required setpoint did not impair operability of the system.

The redundant radiation monitor was found to be within acceptable limits and would have initiated the required actions upon receipt of a ventilation exhaust duct high radiation signal.

CORRECTIVE ACTION

The sensor converter in the radiation monitor in question was replaced and calibrated; the radiation monitor was satisfactorily tested.

P00R BRIGINAI.