ML20084H757

AO BFAO-7429W:on 740513,RHR Isolation Shutdown Cooling Suction Isolation Valve FCV 74-47 & Shutdown Cooling Head Spray Isolation Valve FCV 74-77 Isolated RHR Shutdown Cooling Mode & Tripped Pumps.Caused by Disconnected Spring

ML20084H757
Person / Time
Site:	Browns Ferry
Issue date:	05/23/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084H760	List: ML20084H757 ML20084H762
References
AO-BFAO-7429W, NUDOCS 8305050023
Download: ML20084H757 (3)

Text

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, TENNESSEE VALL '

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. CHATTANOOGA, ,TENNESSEEAUTHO AITY i' t73' i7/' "

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. . ~ 3 May 23, 1974 . MMN.g' SWEEEEE P A A m F.A S H ip V -

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Mr. John F. O' Leary, Director N Q ..,S,9 'r- ,/y'

'O 4 Directorate of Licensing '*/(#4 ,,,E##

Office of Regulation ' N '% b U.S. Atomic Ener6y Co::: mission

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Washington, DC 20545 s'/4[: N N.{l .

Dear Mr. O' Leary:

TE:WESSEE VALLL'Y AUTHORITY - BROWNS FERRY UUCLEAR PLANT UNIT 1 -

DOCKET NO. 50-259 - FACILITY OPERATIIiG LICENSE DPR ABNORI.'E OCCURRE:TCE REPORT BFAO-7429u The enclosed report is to provide details concerning an armature spring which disconnected on a relcy in the residual heat removal system shut-down cooling isolation valve logic and is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973. This event occurred on Browns Ferry nuclear Plant unit 1 on May 13, 1974.

Very t: .:1y yours, TD MESSEE VALLEY AUTHORITY

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E. F. Thomas Director of Power Production Enclosure CC (Enclosure): .

Mr. Herman C. Moseley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street,IDT., Suite 818 Atlanta, Georgia 30303 l

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Report No.: BFAO-7429W 'v Report Date: May 23, 1974 t!. l.~

9-Occurrence Date: May 13, 1974 \- ."

Facility: Browns Ferry nuclear Plant unit 1 1;s Identification of Occurrence Armature spring disconnected on a relay in the residual heat removal system shut-down cooling isolation valve logic.

Conditions Prior to Occurrence ,

The reactor was in the cold shutdown condition.

Description of Occurrence l

l At 8:19 a.m. while conducting a routine surveillance test, RHR isolation valves FCV 74-47, shutdown cooling suction isolation valve, and FCV 74-77, shutdown cooling head spray isolation valve, isolated the RHR shutdown cooling mode and tripped the RER pu=ps.

Designation of Armarent Cause of Occurrence Both valves are isolated by relay 10A-K983. The relay amature tensioning spring

,dlich hsids thc rclay in its accnergir.cd po.itica wa. fvund di.cuuueet,ed. . Il2e surveillance test requires that four contacts on the relcy be inhibited. 'rTnile

,attc=pting to place the inhibits on the centacts, the relay ar=ature, without the tensioning spring to hold it out, was inadvertently pushed in making up contacts to close the valves.

Analysis of Occurrence The disconnected tensioning spring allowed the relay ar=ature to go to its energized position when the armature was touched. The contacts momentarily made up, closed the valves, cnd tripped the RER pu=ps. This isolation did not affect the LPCI code of R'G , and it would have been available if needed.

Corrective Action The spring was reconnected to the armature and the relay satisfactori.1,y tested.

The RHR system was placed back in the shutdown cooling mode. The surveillance was completed and the relay functioned properly.

An inspection of all sicilar relcys in use on critical systems was conducted.

Two other relays were found with the spring disconnected and were repaired.-

One relay was in the load shedding logic for the recirculation pu=p M-G set oil pumps and the control boy vent fcns. The other was in the starting logic for diesel generator "D." Neither of these cases would have prevented the logic .

circuit from perfoming its intended safety function.

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Failure Data Two General Electric Company type E A relays, model 12 WA51AhlF, 250V de One General Electric Company type WA relay, model 12EA51A41H, 250V de i

The disconnected springs are believed caused by a maintenance or installation error rather than any weakness of the relay.

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