ML20028H426

LER 89-005-01:on 890330,intermittent Connection While Sliding Module Into Position Caused Automatic Test Insertion Circuit to Send Signals Greater than Normal Pulse Thus Allowing Three SIAS Modules to actuate.W/901227 Ltr

ML20028H426
Person / Time
Site:	Millstone
Issue date:	12/27/1990
From:	Deslandes K, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-005, LER-89-5, MP-90-1343, NUDOCS 9101040150
Download: ML20028H426 (4)

Text

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N^RTHEAST UTILITIES c a - = c w se a nsuaat B-kn c=a* *ut 1 UsfeNaS'sIeNs'e'ttNe:Ec"coSUn7 P.O. box 270 g ' 2 Yne*a:I$15I$Sc7E'Noany HARTFORD. CONNECTICUT 06414-0270 Nortneast twea* Energy Company (203)666-6000 Re: 10CFR50.73(a)(2)(iv)

December 27, 1990 MP-90-1343 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Reference:

Facility Operating License No. DPR-65 Docket No. 50-336 Licensee Event Report 89-005-01 Gentlemen:

This letter forwards update Licensee Event Report 89-005-01.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY FOR: Stephen E. Scace Director, Millstone Station 1

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BY: { rry((L>d HaynesV Millstone,JJnit 1 Directo SES!KDD:mo 2

Attachment:

LER 89-005-01 cc: T. T. Martin, Region I Administrator W. J. Raymond, Senior Resident Inspector, Millstone Unit Nos.1, 2 and 3 G. S. Vissine, NRC Project .Manacer, Millstone Unit No. 2 p*4pm

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l LICENSEE CONT A07 EOR %!S LER r12, NAME 'E.E ONE NuvEsFR ARL A CODL Keith D. Deslandes, Engmeer, X4421 0 0l3 4l4l7l-l1l7l9l1 COUDLETE ONY UNE FOR E AO*+ COMDONENT F ALUAE DE SOA BED IN Tws AEDOAT (131 hM ' W CAUSE SYSTEA COMPONENT CAuSE SYSTEM COMDONENT Nh" 7d I II l l I I I II ! I I I I i! I I I i l Ii i i l I su cct EMENTAc AEPOAT ExoECTED no s EXAEC'EO SuBM S S!ON

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On March 30,1989 at 0340 hours0.00394 days <br />0.0944 hours <br />5.621693e-4 weeks <br />1.2937e-4 months <br />, with the reactor critical, power level at 10" percent and the plant in mode 2, at normal temperature and pressure, instrument and Control personnel were in the process of re-installing the Automatic Test insertion (ATI) module in the Engmeered Safeguard Actuation System (ESAS). The re-installation was bemg made following troubleshooting on an unrelated problem.

The ATI automatically tests the various logic combinations for ESAS signals. It does this by actually sending a 2 millisecond signal through the instrument loop.- During reinstallation, the ATI module connector did not mate smoothly with the ESAS cabinet socket. The intermittent connection while sliding the module mio position caused the ATI circuit to send signak greater than the normal pulse thus allowing three Safety injection Actuation Signal (SlAS) modules to actuate.

The control room operators immediately responded in accordance with AOP 2571 and verified that the SI AS modules were inadvertently actuated, and that only the equipment controlled by the three modules had been affected [both Boric Acid pumps started, vahe 2-CH-514 (Boric Acid pump discharge valve) opened. Chiller .

X169B started and the "B" and "D" Containment Air Recite (C.\R) fans shilted from fast to slow speed.) The operators then restored the actuated equipment to its normal condition.

There were no safety implications because all actuated equipment responded as expected.

Similar Events: LER 84-001 and 85-004 l

l NRO Form 366 16-B91

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NRc Iorm 360A V 6, NUCLE Ak P.!OAAToRY CoMf4SSCN AWRovEo oVB No 3350-c1Cm (6-69 E XPAl s : a ,30 92 Esnmates b/ con per response to compty won 1Ns LICENSEE EVENT REPORT (LER) 7 % l g , y g g *5l, M l 4 ,,',*'t,"ll,,,

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0l 6l 0l 0l 0l3 l3 l6 6l4 0l 0l$ 0l1 0l 2 OF 0l 3 TE c m mme sme 4 receee n. anon Noc *em 3esA u on 1.' Desermoon of Event On March 30,1989 at 0340 hours0.00394 days <br />0.0944 hours <br />5.621693e-4 weeks <br />1.2937e-4 months <br />, wnh the reactor crincal, power level at 10"' percent and the plant in -

mode 2 at normal temperature and pressure, Instrument and Control personnel were in the process of re-instalhng the Automatic Test insernon (ATI) module m the Engineered Safeguard Actuauon $3 stem (ESAS). The re-instalianon was bemp made following troubleshooting on an unrelated problem. j The ATl automaticall> tests the vanous logic combinations for ESAS signals. It does this by actually sendmg a 2 milhsecond signal through the mstrument loop. Durmg re-installation, the ATI module connector did not mate smoothly with the ESAS cabinet socket, The intermittent connection while sliding the module into position caused the ATI circuit to send signals greater than the normal pulse thus allowmp three Safety injection Actuation Signal (SlAS) modules to muate.

The control room operators immediately responded in accordance with AOP 2571 and verihed. that the SlAS modules were inadvertently actuated, and that only the equipment controlled by the three modules had been affected (both Boric Acid pumps started, valve 2-CH-514 (Bone Acid pump discharge valve) opened. Chiller X169B started and the "B" and "D" Containment Air Recirc (CAR) fans shifted from fast to slow speed.) The operators then restored the actuated equipment to us normal condition.

11. Cnute of Event The cause of the event was the sudden power spike durmg the re-energization of the ATI module.

The root cause of the event is the method required for removing and installing the ATI module and may be termed a hardware design problem. The electrical pins of the module do not engage the socket (located in the ESAS) until the module captive screws are at half travel, The screws.are turned down in.

a sequence so the total module moves in uniformly, otherwise some pins will engage before the others and an inadvertent actuation may occur, as it did it this case.

This is the normal design feature of the ATI module and rarely does the module need to be removed during normal operating conditions.

111. - Annhwit of Event ,

This event is being reported pursuant to the requirements of paragraph 50.73 (a)(2)(iv), a condition that resuhed in manual or automatic actuauon of any Engineered Safety Feature (ESF).

The Boric Acid pumps and chiller 169-B are normally off during normal operation. Valve 2-CH-511 is normally clo3ed and the B and D Car fans are normally-in fast speed. - When the modules (AM615, 618 and 625) actuated due to the inadvertent ATI signal, the Boric Acid pumps and Chiller 169-B started,-

valve 2-CH-514 opened and the B and D Car fans went to slow speed. The equipment went to its respective accident position. The worst case condition would be that the Boric Acid pumps would tend to take the reactor sub-critical. With the CAR fans in slow speed, Containment temperatures might have increased, however operation in response to Containment temperature alarms would correct this condition, Therefore there were no safety consequences as a result of this occurrence.

IV. Corrective Action A key swnch has been installed which will remove power from the ATI in a postuve, controlled, manner.

Whenever the switch is in the "off" posinon (power remmed) a local indication, and control room annunciator will alarm. The alarm will notify the control room operator and the technician performing the work, that the ATI is disabled.

The removal of power from the module will act as an ATI block, which will prently reduce the chance of an inadsertent actuauon when performing corrective maintenance on the module.

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LICENTEXT CONTINUATIONSEE EVENT REPORT (LER) aw neports Managemem Branen <c 53o,. v s. Ne# ear

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'EU 'c arn hiillstone Nuclear Power Station U L-0l 6l 0l 0l 0l3 l3 l6 8l9 0l 0l 5 0l1 Oj 3 OF -0l 3 TE XT 01 more space is f equue1 use additrortai NRc Fo'm 366A 51 (171 V, Additionnl Information Similar LER'S: 64-001 and 86-004 ESAS Actuation System Vendor: C560 hiodel: 9N21-6 Component Function: XC ESAS h!TI Actuation hiodule Vendor: C560 Niodel: 6N41 Component Function: AIK Boric Acid Pumps Vendor: GIS:

N1odel: 3195h!T Component Function: P Containment Air Recire (CAR) fans Vendor: W121 hiodel: 366-A7 Component Function: FAN Valve 2-CH-514 Vendor: YOSS Alodel: P-35142

. Component Function: Y Chiller X169B' Vendor: T265

-Modeh COWA-4006-MA Component Function: CHU a

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