05000346/LER-1978-045-03, /03L-1:on 780503,first Reactor Vessel Stud Detensioned,Placing Unit Into Mode 6,requiring Audible Indication of Neutron Flux in Containment.Cause Was Procedure Error.Audible Indication Was Installed

/03L-1:on 780503,first Reactor Vessel Stud Detensioned,Placing Unit Into Mode 6,requiring Audible Indication of Neutron Flux in Containment.Cause Was Procedure Error.Audible Indication Was Installed

ML20027A457
Person / Time
Site:	Davis Besse
Issue date:	05/30/1978
From:	Hartigan J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20027A454	List: 05000346/LER-1978-045-03, /03L-1:on 780503,first Reactor Vessel Stud Detensioned,Placing Unit Into Mode 6,requiring Audible Indication of Neutron Flux in Containment.Cause Was Procedure Error.Audible Indication Was Installed ML20027A453
References
LER-78-045-03L, LER-78-45-3L, NP-33-78-55, NUDOCS 7812050162
Download: ML20027A457 (2)

LER-1978-045, /03L-1:on 780503,first Reactor Vessel Stud Detensioned,Placing Unit Into Mode 6,requiring Audible Indication of Neutron Flux in Containment.Cause Was Procedure Error.Audible Indication Was Installed

Event date:
Report date:
3461978045R03 - NRC Website

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[T}T} l On 5/3/78, the first reactor vessel stud was detensioned in preparation for reactor It was not realized until 5/5/78 that this first stud detensioning l

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l TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-78-84 DATE OF EVENT: June 19, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Borated Water Storage Tank (BWST) low level trip setpoint out of tolerance Conditions Prior to Occurrence: The unit was in Mode 6, with Power (MWT) = 0, and Load (MNE) = 0.

Descriotion of occurrence: During performance of Surveillance Test ST 5031.01,

" Safety Features Actuation System (SFAS) Monthly Test" on June 19, 1978, at 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />, the BWST low level trio setooint for SFAS Channel 1 was found to have been out of tolerance.

Technical Specification 3.3'.2.1 requires the operability of four BWST low level instrument strings (one in each SFAS channel) in Modes 1, 2 and 3.

Since the unit was in Mode 6 at the time of the occurrence, Action Statement 9 was not applicable. This occurrence is being reported as documentation of component failure.

Designation of Aeoarent Cause of Occurrence: The cause of the occurrence is attributed to a component failure of the level trip module. The setpoint on 1

level switch LSL-1525A had apparently drif ted.

L Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. The BWST level instrument strings for SFAS Channels 2, 3 and 4 were operable during the, period that indication for Channel 1 was inoperable.

The unit was in Mode 6 at the time of the occurrence.

Corrective Action

The level trip module was replaced with a new module under Maintenance Work Order IC 386-78. After the module was bench tested and Surveil-lance-Test ST 5031.01 was successfully performed, BWST level indication for SFAS Channel 1 was declared operable at 1535 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.840675e-4 months <br /> on June 19, 1978.

Failure Data: BWST level indication was previously reported to have been inopera-ble in Licensee Event Reports NP-33-77-107 and NP-33-78-01 due to frozen sensing lines. BWST level indication was previously reported to have been inoperable in Licensee Event Report NP-33-78-73 due to component failure other than instru=ent drift.

LER #78-070 e

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