ML20064F198

/03L-0 on 781027:during Routing Surveillance of Steam Pipe Rupture Detection Sys,One of Three Bistables for High Temperature Under Pcrv Did Not Trip,Due to Corroded Cable Terminal Board at Junction Box

ML20064F198
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/22/1978
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:
Shared Package
ML20064F172	List: ML20064F170 ML20064F198
References
LER-78-033-03L, LER-78-33-3L, NUDOCS 7811280318
Download: ML20064F198 (4)

Text

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. \ REPORT DATE: Nov:mbar 22, 1978 REPORTABLE OCCURRENCE 78-33

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[,' ISSUE O OCCURRENCE DATE: Octobar 27, 1978 PAGE 1 of 3 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/78-33/03-L-0 Final IDENTIFICATION OF OCCURRENCE:

During routine surveillance testing of the steam pipe rupture detection system, one of the high temperature bistable switches did'not trip.

This resulted in operation under a degraded mode permitted by LCO 4.4.1 and is reportable per Fort St. Vrain Technical Specification AC 7.5.2(b)2.

(":! EVENT DESCRIPTION:

On October 27, 1978, while operating at 12% reactor power with no electrical output, plant instrucent personnel performing routine surveillance testing, noted that one .of the three bistables for high temperature under the PCRV did not trip.

Two other redundant bistables were available as indicated by a successful test.

See Figure 1.(typical for red dant channels). A combination of ultrasonic noise, detected by noise detectors, 1 ,i conjunction with a pressure rise, detected by pressure differential switches, 2 , or a temperature rise, detected by temp-eratureswitches,() If a loopshutdownlogic],(f)indicatesapiperupture., )initiates , throughaaloop shutdow series of

(} solid state electronics and relays.

The inoperable channel was placed in a tripped condition in compliance with LCO 4.4.1 requirements and was returned to service following repair and test.

CAUSE DES CRIPTION:

The cable between the temperature element and the temperature switch was open due to corrosion at a terminal board, caused by moisture leaking into the junction box.

CORRECTIVE ACTION:

The terminal board and junction box have been replaced and the junction box sealed with silicone to prevent a recurrence of the problem.

No further corrective action is anticipated or required.

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REPORTABLE OCCLRRENCE 78-33

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ISSUE O

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Reactor Building South Wall Area Loop 1 - Loop 2 Piping Arapf

- v Piping Area O I ,.

Building Atmospheric

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Air (typical of 3)

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la 2 h l Solenoid Solenoid Ultra XE I XE Temperature under Sonic TS

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Noise Deucted PCRV (rypical of 3) j iemperatur a

(' ' Main S aitch h Room Amplifer .

Control Test Test Switch XSH Bistable Switches Bistables ,,

Loop Shutdown A VBkCk AuRi el ,

Logich 2 of 3 l 2 of 3 2 of 3 2 of 3 j

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2 of 3 input IiSN,bm,o J I 2 of 3 1 2 of 3 I uncer FCRV 4 '

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under PCW Sonic No wall 4 il 2 of 3 input l2of3

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Reactor Bldg. _ emm eith Lock out sonic No.

Loop 1ILoon 2l Wall Rx. I ld;;.

Senses Loop 1 or Leak V Building Pressure or and Temperature Rise (Discriminates Against

-d Spurious Noise)

Loop Stutdown h

Figure 1

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• I REPORTABLE OCCURRENCE 78-33 ISSUE O Page 3 of 3 Prepared by: # .

Asa Reed, Jr. //

Technical ServiceF Technician Reviewed by: ./ , c_ -

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chnical Services Supervisor Reviewed by: / 7A'b

, Frank M. Mathie Operations Manager Approved by: Ne .o ,

Don Ware = bourg Manager, Nuclear Production

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LICENSEE EWENl;JEFON1r CONTROL B' LOCK: l 1

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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7 8 60 61 DOCKET NUMB ER 68 69 EVENT CATE i EVENT DESCRIPTION AND PRC9ABLE CONSEQUENCES h 10121l During routine surveillance of the steam pipe rupture detection system one of the l Redundant systems l' Io lai I three bistables for high temperature under the PCRV did not trip.

loi.,l were available and operable. Event was not repetitive. Cable terminal board in l 1o isl l junction box was replaced and the surveillance test was successfully completed. No l 1o is l l accompanying occurrences, no effects on public health. 1 l

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34 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h li10ll A cable terminal board at the junction box was open circuited due to corrosion. I li l 3 g l Corrosion was the result of humidity and temperature in ambient atmosphere. Terminall

board and junction box was replaced and surveillance test successfully completed. I g , g 3] l No further corrective action required.

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• h 80WER CTHER STATUS IS O Y OfSCOVERY DESCRIPTION STA N/A l l1 15 l l E l@ l 0l ll 2l@] "

l lB l@l" Surveillance Test 8 A!TiviTY C:TTENT RELEASE AVOUNT CF ACTIVITY LOCATION oF RELEASE lile I i Z l @D OF PELEASEl N/A Zl@l l l N/A 80 l

7 8 9 10 11 44 45 PERSONNEL EXPOSURES NUYBER TYPE D E SCR'PTIO N N/A l li 17 l l 0 l 0 l 0 l@l Z ]@l

• PERSON d % # ES NUY8 t R DESCRIPTION N/A l li l- l8 l90 l 0 l 0 l@l*2 7 11 80 LO*4 OF OR DAMAGE TO FACILITY Tv*E CESCRIPTION I i 19 l l_Z_jhl N/A l 80 7 8 9 10

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J. W. Gahm PHCNE: (303 785-2253 rA ecPPasoaps, _ .