ML19296A206

LER 79-015/03L-0:on 790117,core Flood Tank 1-2 Isolation Valve CF1A Would Not Close by Remote Operation.Caused by Loose Set Screw.Cracked Pinion Gear & Associated Key Replaced Per Maint Work Order 78-2928

ML19296A206
Person / Time
Site:	Davis Besse
Issue date:	02/12/1979
From:	Oneill J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19296A205	List: ML19296A204 ML19296A206
References
LER-79-015-03L, LER-79-15-3L, NUDOCS 7902200017
Download: ML19296A206 (3)

Text

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NRC FORM 366 (7 77)

LICENSEE EVENT REPORT O CONTROL BLOCK: l l l l l l jh

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATIONI j o l i j l 0 l 11 i

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LICENSEE CODE 14 15 LICENSE NuveEM 7 8 9 CON'T o [,',o" T l L Jgl 0 l 5 l 0 l- l 0 l 3 l 4 l 6 gl 690 1 l1 l7 l 7 ] 9 }@l0 l 2 l1 l 2 l 7 l 9B0j@

EVENT DATE 14 la REPORT DATE t4 I # t,0 b1 DOCKET NUVBER EVENT DESCRIPTION AND PROBABLE CONSEQUtNCES h j f5TF1 1 On 1/17/79, Core Flood (CF) Tank 1-2 Isolation Valve CFlA would not close by remote The valve was closed manually and reactor shutdown continued. There was l

[ o ; 3 l l operation.

The primary pur- l lo l4 j j no danger to the health and safety of the public or unit personnel.

l l o l 3 l l pose of the power operation of valve CF1A is to act as a backup for cperator actions o e lduring startup.

The valve was opened prior to reaching 800 psig Reactor Coolant Sys- l The valve l J o l 7 l l tem (RCS) pressure during the previous startup as required by T.S. 3.5.1.

(NP-33-79-18) l l o j a ! l operator power supply is isolated during operations y 800 psig. 80 7 8 9' CAUSE CAUSE COMP. VALVE SYSTEM SUSCODE SUBCODE CODE CODE SU8 CODE COVPONENT CODE o ') l S l F10l@ E l@ l Bj@ l Vl Al Ll Vl 0l Pl@ g@ g @

f3 18 33 20 9 11 12 REVISION 7 8 OCCUR R E N CE REPORT SEQUENTI A L CODE TYPE REPORT NO.

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, o lThe failure of the valve motor operator to function was due to component failure re-screw. Under Maintenance Work Order 78-2928, the cracked l l jij lsulting from a loose set

,,,,,g pinion gear and its associated key were replaced. On 1/26/79, valve CFlA was cycled l The valve operated satis-j g,g3, l and observed for proper operation using the motor operator.

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John O'Neill ,,, ,.,

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT 7NE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-18 DATE OF EVENT: January 17, 1979 FACILITY: Davis-Besse Unit 1 Failure of Core Flooding Isolation Valve CF1A motor IDENTIFICATION OF OCCURRENCE:

operator The unit was in Mode 3, with Power (MWT) = 0, and  ;

Conditions Prior to Occurrence:

Load (Gross MWE) = 0.

Description of Occurrence: During a unit shutdown on January 17, 1979, operations personnel attempted to close the Core Flood (CF) Tank 1-2 Isolation Valve CFLA The valve could not be closed with the motor operator using and was the motor operator.

manually closed. During the investigation into the f ailure of the motor operator, it was determined that during a unit startup at 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br /> on December 29, 1978, the valve CFIA would not open using the motor operator and had been manually opened. Technical Specification 3.5.1 requires both Core Flood Isolation increasing Reactor Coolant System (RCS) pres-Valves to be open prior to the unitThe valve was manually opened prior to RCS pressure exceedi sure above 800 PSIG.

800 PSIG on December 29, 1978.

The Core Flood Tanks Isolation Valves are opened the entire tbne RCS pressure is above 800 PSIG, and the power removed from the motor operators to prevent Whenever an in- is RCS pressure advertent closure f rom rendering the CF Tank inoperable.

below 700 PSIG, the Core Flood Tanks Isolation Valves are closed, and the power inadvertently opening the valve and removed fran the motor operators to prevent discharging from the Core Flood Tank.

The only ef f ect the failure of the motor operator had was to render the backup This report is automatic opening of the Core Flood Isolation Valve inoperable.

being submitted as documentation of a component failure.

The apparent cause of the failure of Designation of Apparent Cause of Occurrence: The motor operator of CFlA was the motor operator for CFIA is a fabrication error.This is a small gear on the end of the found to have a cracked motor pinion gear. The set screw which motor shaft which supplies the initial torque to the operator.

This allowed the key which keeps the near holds the gear to the shaf t came loose.to travel downward and catch on the casting of the housin rotating with the shaf t The crack in the gear This in turn bent the key and caused the gear to crack.

then permitted the key to fall completely out and prohibited the pinion gear from turning with the motor shaf t. This caused the operator to be inoperative in either direction.

LER #79-015

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TOLEDO EDISON CO*1PANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-79-18 Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. Since CF LA could be operated manually, the Core Flooding System remained operable.

Corrective Action: Under Maintenance Work Order 78-2928, the pinion gear and the associated key were replaced. At 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on January 26, 1979, CF 1A was cycled using the motor operator and proper operation verified.

Failure Data: There have been no previously reported similar occurrences.

LER #79-015

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