05000245/LER-1981-033, Forwards LER 81-033/03L-0.Detailed Event Analysis Encl

Forwards LER 81-033/03L-0.Detailed Event Analysis Encl

ML20032C986
Person / Time
Site:	Millstone
Issue date:	11/05/1981
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20032C987	List: 05000245/LER-1981-033, Forwards LER 81-033/03L-0.Detailed Event Analysis Encl 05000245/LER-1981-033-03, /03L-0:on 811006,during Reactor Vessel Low Water Level Scram & low-low Isolation Functional Test,Switch 263-57A Setpoint Found Less Conservative than Tech Spec. Caused by Setpoint Drift.Switch Recalibr & Tested
References
MP-1-1942, NUDOCS 8111130276
Download: ML20032C986 (2)

LER-1981-033, Forwards LER 81-033/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2451981033R00 - NRC Website

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November 5, 19 g @\\19 D/Tg Mr. Ronald C. Haynes MP-1-1942 Director, Region I g' ( fj g 3, I },o Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 7j fd.bLi V

631 Park Avenue

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NOV12 I90l'.il King of Prussia, Pennsylvania 1940b

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Reference:

Provi.;ional License DPR-21 D

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,y Docket No. 50-245 h

Reportable Occurrence R0-81-33/3L

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Dear Mr. Haynes:

This letter forwards the Licensee Event Report for Reportable Occurrence R0-81-33/3L 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 copies of tne report are enclosed.

Yours truly, NORTHEAST NUCLEAR ENERGY COMPANY ff/

• CCE/

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

Attachment:

LER R0-81-33/3L 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 K0$bbb

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Attachment to LER 81-33/3L Northeast Nuclear Energy Company Millstone Nuclear Power Station - Unit 1 Provisional License Numoer DPR-21 Docket Number 50-245 Identification of Occurrence An engineered safeguard isolation setpoint was found to be less conservative than that established by Technical Specifications.

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

Designation of Occurrence On October 6,1981, at 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br />, while performing Reactor Vessel Lo Water Level Scram and to Lo Isolation Functional and Calibration Test, switch 263-57A was found to trip at a water level of approximately 83.2" above active fuel. Technical Specification, Table 3.2.1 requires a lo-lo water primary containment isolation at 79",

+4",-0", above active fuel.

Designation of Apparent Cause of Occurrence Failure of the switch in to trip at its desired setpoint was attributable to setpoint drift.

Analysis of Occurrence The low low reactor water level instrumentation is set to trip when reactor water level is 79" above the top of the active fuel. This trip initiates closure of Group 1 primary containment isolation valves and also activates Emergency Core Cooling Subsystems (ECCS) and starts the emergency diesel generator and the gas turbine generator and trips the recirculation ptimps. The trip level setting was chosen to be high enough to prevent spurious operation but low enough to initiate ECCS operation and priuary system isolation so that post accident cooling can be effectively accomplished.

Failure of the switch in question to operate did not result in a condition that had not been previously analyzed. The remaining switches in the logic system were found to be operating properly and would have initiated the required action.

Corrective Action

c 1

The pressure switch in question was recalibrated to within its acceptable setpoint range and was satisfactorily tested.

The pressure switch is a Yarway, Model 4418C.