05000245/LER-1981-034, Forwards LER 81-034/03L-0.Detailed Event Analysis Encl

Forwards LER 81-034/03L-0.Detailed Event Analysis Encl

ML20032E835
Person / Time
Site:	Millstone
Issue date:	11/12/1981
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20032E836	List: 05000245/LER-1981-034, Forwards LER 81-034/03L-0.Detailed Event Analysis Encl 05000245/LER-1981-034-03, /03L-0:on 811013,one of Four Time Delay Relays Bypassing Turbine Control Valve Fast Closure Scram Trip Failed to Trip at Specified Limit.Caused by Setpoint Drift. Relay Recalibr & Tested
References
MP-1-1945, NUDOCS 8111230345
Download: ML20032E835 (2)

LER-1981-034, Forwards LER 81-034/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2451981034R00 - NRC Website

text

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g November 12, 1981 MP-1-1945 Mr. Ronald C. Havnes

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U. S. Nuclear Regulatory Coanission 6

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Reference:

Provisional License No. DPR-21 r

va. mm nmma Docket No. 50-245

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"" " r Reportable Occurrence R0-81-34/3L k

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Dear Mr. Haynes:

m This letter forwards the Licensee Event Report for Reportable Occurrence R0-81-34/3L required to be submitted within 30 days pursuant to the requirements of the Millstone Unit 1 Technical Specifications, Section 6.9.1.9.a.

An additional three cooies of the report are enclosed.

Yours truly, fiORTHEAST NUCLEAR ENERGY COMPANY

$1'$ CW E.

. Mroczka Station Superintendent Millstone fluclear Power Station EJM/TST:mo

Attachment:

LER R0-81-34/3L cc:

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

Director, Office of flanagement Information and Program C0atrol, Washington,D.C.(3) g,24L 811123034S 811112 j

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ATTACHMENT TO LER 81-34/3L NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION UNIT 1 PROVISIONAL LICENSE NUMBER DPR-21 DOCKET NUMBER 50-245 Identification of Occurrence A reactor protection instrument setting was found to be less conservative than those established by technical specifications.

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

Description of Occurrence On October 13,1981 at 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br />, while performing Turbine Control Valve Fast Closure Functional and Calibration Test, it was discovered that one of the four time delay relays which bypasses the turbine control valve fast closure scram trip exceeded technical specification limit.

Technical specification, Table 3.1.1, requires automatic bypass of a scram trip for a maximum of 260 milliseconds following initiation of a load rejection. The subject relay 590-125C was found to operate at 261 milliseconds.

Desianation of Apparent Cause Failure of the time delay to trip at its desired setpoint is attributable to setpoint drift.

Analysis of Occurrence The Turbine Control Valve Fast Closure Scram is provided to anticipate the rapid increase in pressure and neutron flux resulting from fast closure of the turbine control valves due to a load rejection and subsequent failure of the bypass valves to open.

In order to accommodate the full load rejection capability, without a reactor scram, the trip is automatically bypassed by four time delay relays whose maximum setting should be 260 milliseconds. The four relays are arranged in a one out-of-two-twice logic such that failure of one relay to trip at the proper setting does not impair the system's ability to perform its intended function. The setpoints of the remaining three relays were within their desired range and would have initiated the required action within the allotted time.

Corrective Action

The setpoint of the relay was adjusted to its proper setpoint and tested satisfactorily. This reportable occurrence is similar in nature to R0-78-3/lT, R0-78-19/3L and R0 81-30/3L.

The relay was manufactured by the Agastat Relay Company, Model Number 2122-A-H2SB, with a range of 100 to 300 milliseconds.