05000382/LER-1990-004, :on 900408,partial Actuation of Emergency Feedwater Sys Occurred During Scheduled Test of Plant Protection Sys.Caused by Test Circuit Malfunction.Relay Hold Pushbutton Assembly Replaced

:on 900408,partial Actuation of Emergency Feedwater Sys Occurred During Scheduled Test of Plant Protection Sys.Caused by Test Circuit Malfunction.Relay Hold Pushbutton Assembly Replaced

ML20042F750
Person / Time
Site:	Waterford
Issue date:	05/07/1990
From:	Mcgaha J, Tanya Smith LOUISIANA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-004, W3A90-0145, NUDOCS 9005090344
Download: ML20042F750 (5)

LER-1990-004, on 900408,partial Actuation of Emergency Feedwater Sys Occurred During Scheduled Test of Plant Protection Sys.Caused by Test Circuit Malfunction.Relay Hold Pushbutton Assembly Replaced

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
3821990004R00 - NRC Website

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i Ref: 10CFR50.73(a)(2)(iv)

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W3A90-0145 A4.05 QA May 7,1990 U.S. Nuclear Regulatory Commission ATTENTION: Document Control Desk I

Washington, D.C.

20555 Subject: Waterford 3 SES l

Docket No. 50-382 License No. NPF-35 Reporting of Lice see Event Report l

Gentlemen Attached is Licensee Event Report Number LER-90-004-00 for Waterford Steam Electric Station Unit 3.

This Licensee Event Report is submitted pursuant to 10CFR50.73(a)(2)(iv).

Very truly yours,

'J.R.

McGaha Plant Manager - Nuclear JRM/KTW/rk (w/ Attachment) cci Messrs. R.D. Martin J.T. Wheolock - INPO Records Center E.L. Blake W.M. Stevenson D.L. Wigginton NRC Resident Inspectors Office 9005090344 900507 6DR ADOCK 05000382 l

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At 0444 hours0.00514 days <br />0.123 hours <br />7.34127e-4 weeks <br />1.68942e-4 months <br /> on April 8, 1990, Waterford Steam Electric Station Unit 3 was operating at 100% power when a partial actuation of the Emergency Feedwater i

(EFW) system occurred during a scheduled functional test of the Plant Protection System (PPS).

This event is reportable an an unplanned Engineered Safety Feature (ESP) actuation. The actuation was not of sufficient duration to allow ErW flow to the Steam Generators (SG).

The root cause of this event is test circuit malfunction.

Inspection of the matrix test module relay hold pushbutton contact blocks and wiring revealed a higher than normal resistance across the early opening contacts.

The relay hold pushbutton assembly has been replaced and the PPS functional test has been l

completed satisfactorily. Further diagnostic testing of the relay hold pushbutton is planned to attempt to isolate the cause of the circuit malfunction.

11ecause the circuit malfunction was associated only with the test circuitry and i

the EFW System was capabic of responding in the safe direction, this event did I

not threaten the health and safety of the general public or plant personnel, i

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PA06 (31 ygan f l uvt NT ea k ef v stoN Waterford Steam Electric Station Unit 3 0l 0l 4 0 l5 l 0 l 0 l 0 l 3l8 l2 9 10 O l0 012 OF gl4 iEKT IN newe spece h reess eel arse enMaanelMC Form anWeb (1h At 0444 hours0.00514 days <br />0.123 hours <br />7.34127e-4 weeks <br />1.68942e-4 months <br /> on April 8, 1990, Waterford Steam Electric Station Unit 3 was operating at 100% power when a partial actuation of the Emergency Feedwater (EFW) (EIIS Identifier - DA) occurred during a scheduled functional test of the Plant Protection System (PPS) (EIIS Identifier - JC).

This event is reportable as an unplanned engineered safety feature (ESP) actuation.

While performing step 85 of operating procedure (0p) 903-107, " Plant Protection System Channel Functional Test," which involves pressing and-holding the PPS matrix relay hold pushbutton and verifying system response, all three EFW pumps (EIIS Identifier BA-P) and Steam Generator (SG) (EIIS Identifier-SG) Blowdown System Isolation Valves (EIIS Identifier WI-ISV) actuated.

The EFW to SG isolation valves did not open due to the short dura: ion of the actuation signal.

The functional test was terminated and EFW system components were returned to their normal configuration.

The inadvertent actuation could not be reproduced and the functional test was later reperformed with satisfactory results.

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The matrix relay hold pushbutton performs three functions.

1) It interrupts test power to the matrix test modules (EIIS Identifier - IMOD) not being tested.

2) It provides test power to the matrix relay bistable coils (EIIS Identifier - RIN/CL) through the use of early closure contacts (EIIS Identifier - CNTR) on the pushbutton.

3) It provides test power to the 1

matrix bistable relay opposing coils.

During the circuit test sequence. the relay hold pushbutton is depressed and l

I through use of the early closure contacts, applies test power to the aiding 1'

coils of the matrix trip path relays before the bistable relays are l

l deenergized.

If the bistabic relays deerergize the matrix trip path relay primary coils before the matrix relay aiding coils energize, an Emergency Feedwater Actuation Signal (EFAS) (EIIS Identifier BA-JE) will result.

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During troubleshooting performed on May 3, 1990, the relay hold pushbutton and contact blocks for the A-C matrix test module were examined and revealed a higher than normal resistance across the early opening contacts.

(Resistance measured in the range of 1.9 to 28 chms, compared to a normal resistanco of 0.2 ohms). This increased resistance may have allowed the bistable relays to deenergized before the matrix relay aiding coils fully energized, causing the EFAS.

I Based on the results of this inspection, the relay hold pushbutton and contacts were repinced and the A-C matrix was tested satisfactorily. Further diagnostic testing of the removed pushbutton is planned to attempt to isolate the cause of the circuit malfunction and evaluate to what degree the observed increase in contact resistance could have delayed the energitation of the aiding coils.

The possibility of carbon or corrosion product buildup on the contacts will also be explored. Based on the results of the diagnostic testing, the relay hold pushbutton assembly may be sent to the vendor (Combustion Engineering, Inc.) for further analysis. Appropriate long term corrective action will be taken as a result of this testing.

Consideration will also be given to examination of similar pushbutton assemblies to address any generic concerns that may arise from the collective test results.

If critical definitive information results from these analyses, a supplement to this report will be issued. The above mentioned testing is expected to be completed prior to December 28, 1990.

The circuit malfunction was limited to the PPS test circuitry and would not have impaired the ability of the EFW system or any other related safety systems to respond to an actual demand on the PPS if required. The functional test in progress at the time of the EFAS was later completed satisfactorily. For these reasons, the health and safety of the general public was not jeopardized during this event,

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Similar Events

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