ML20046A893

LER 93-008-00:on 930624,observed That Valve CV-31740, Instrument Air to Unit 1 Containment Closed Due to Failure of Coil in Solenoid Operated Pilot Valve.Valve Reopened Locally to Restore Instrument air.W/930723 Ltr

ML20046A893
Person / Time
Site:	Prairie Island
Issue date:	07/23/1993
From:	Richard Anderson, Hunstad A NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-008, LER-93-8, NUDOCS 9308020069
Download: ML20046A893 (6)

Text

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Northem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401-1927 Telephone (612) 330-5500 ,

July 23, 1993 10 CFR Part 50 Section 50.73 U S Nuclear Regulatory Commission Attn: Document Control Desk i

Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PIANT  !

Docket Nos. 50-282 License Nos. DPR-42 ,

50-306 DPR-60 Containment Isolation Valve Failed Closed Due to Solenoid Valve Failure The Licensee Event Report for this occurrence is attached. In the report, we made no new NRC commitments. ,

Please contact us if you require additional information related to this event.

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if '$ lAf ~~) y Roger 0 Anderson Director Licensing and Management Issues c: Regional Administrator - Region in , .m j NRR Project Manager, hRC Senior Resident Inspector, NRC Kris Sanda, State of Minnesota

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Prairie Island Nuclear Generating Plant Unit 1 l 05000 282 1 OF 4 TITLE (4)

Containment Isolation Valve Failed Closed Due to Solenoid Valve Failure EVENT DATE (5) LER NUMBER (6i REPORT NUMBER (7) OTHER FACILITIES INVOLVED (8) sr c.uma_ m a aN *'" " Nuu*"

t/DY t* cA Y q iJi G tA VONN DAY YFAA vsese n Nuesr" 0,r000 306 Prairie Island Unit 2 3 uom Nw Dcc,g;yn; earn

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6 24 93 93 008 00 7 23 93 05000 OPERATING ITHIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 6: ICheck one or more) (11)

MODE (9) N 20 402:o1 20 405;c) 50 73(aH2Hw) 73 71 tb>

POWER 20 405(aH1H ) 50 36fc H1) 50 73(aH2)(v) 73 71(c)

LEVEL (10) 1001' 20 405la H1)ho 50 3QcH2) 50 73;aH2Hvul OTHER 20 405(aH1)(no y 50.73(aH2H:1 50 73taH2HviitHA) (d*V

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t.em ens m 'ec. Nac 20 405ta H14:v) 50 73iaH2Hn) 50.73;a)(2HviWB) r y ya 20 405 ta H1 Hv) 50.73taH2Hia) 50 73.aH2Hu)

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LICENSEE CONTACT FOR THIS LER (12)

Nn v w >Nt N wi 6 waxe mes u,oe, Arne A Hunstad 612-388-1121 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) m: t tv crw %EN Mw r AcNnin } .[ cAJsE sys tv covnoNENT vwp ACTuaro "f [

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED M* " * '-

vrs ny-tum eerm tDsawsioNner l, y SUBMISSION

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ABSTRACT l Limit to 1400 tpaces i e , approomately 15 smgte-spaced typewrmen imes) (16)

On June 24, 1993, Unit I was at 100% power. At 0357 hours0.00413 days <br />0.0992 hours <br />5.902778e-4 weeks <br />1.358385e-4 months <br />, control room operators observed that valve CV-31740 Instrument Air to Unit 1 Containment, had closed. The valve could not be reopened from the control room. Cause of the valve closure was failure of a coil in its solenoid operated pilot valve.

The loss of instrument air to containment resulted in several valve and damper movements, the most notable of which was letdown line isolation. At 0443, CV-31740 was reopened and held in the open position by bypassing its solenoid operated pilot valve and supplying air directly to the valve operator. At 0450, letdown was restored.

Operators responded to the loss of instrument air using approved procedures.

An expeditious valve repair plan was instituted.

CV-31740 is a containment isolation valve that closes on a containment pressure of 17 psig. The Technical Specification " shutdown action statement" had been entered, but power reduction had not yet begun when the valve repair was completed and the valve declared operable.

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.s REQUIRED NUMBER OF DIGITS / CHARACTERS FOR EACH BLOCK BLOCK NUMBER OF NUMBER DIGITS / CHARACTERS 1 UP TO 46 FACILITY NAME 2 DOCKET NUMBER 3 IN ADDITIO 4 0 05000 3 VAR?ES PAGE NUMBER 4 UP TO 76 TITLF 5 EVENT DATE 2 PER BL K 7 TOTAL 6 LER NUMBER 3 FOR SEQUENTML NUMBER 2 FOR REVISION NUMBER 6

7 REPORT DATE p pER B CK UP TO 18 - FACILITY NAME 0 ^

8 TOTAL - DOCKET NUMBER 3 IN ADDITION TO 05000 9 1 OPERATING MODE 10 3 POWER LEVEL

REQUIREMENTS OF 10 CFR CHECK BOX THAT APPLIES W TO 50 FOR NAME 12 UCENSEE CONTACT 14 FOR TELEPHONE CAUSE VAR!ES 2 FOR SYSTEM 13 4 FOR COMPONENT EACH COMPONENT FA! LURE 4 FOR MANUFACTURER NPRDS VARIES CHECK BOX THAT APPLIES N AL WOM EFECMD O

15 2p gBLOCK EXPECTED SUBV!SSION DATE l

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NAC FORM 368A U.S. NUCLEAR REGULATORY COMMISSION m sm APPROVED BY OMB NO. 3150-0104 EXPlRES 5/31/95 ESTMA'ED BJRDEN PER RESPONSE To COMPLY WTH THS INFORMATON CoufCTON REQUEST: 50 0 HRS. FORWARD LICENSEE EVENT REPORT (LER) coMuE.cs REscoNa 8JRaEN ESTuATE To TsE gonMAToN 6

TEXT CONTINUATION AND RECORDS MANAGEMENT , mon,BRANCH oc ,mS. fuNBB ReavuToRy CoMu1SSoyg.sAS ,, Ay3 To7714), U.S THE PAPERWORK FEDUCTcN FROJECT (31500104), OFFICE oF i MANAGEMENT ANC BJDOET, WAS+tlNGToN, DC 20503. r FACIUTY NAME 0) DOCAET NUMBER (2) LER NUMBER (s) PAGE (3) g LEQUENTLAL HEVSON NUMBER NUMBER k 05000 282 2 oF 4  !

Prairie Island Unit 1 93 008 -

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i EVENT DESCRIPTION '

On June 24, 1993, Unit 1 was at 100% power. At 0357 hours0.00413 days <br />0.0992 hours <br />5.902778e-4 weeks <br />1.358385e-4 months <br />, control room t operators received indications of a loss of instrument air to Unit t  !

containment. They observed that valve CV-31740, Instrument Air to Unit 1

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Containment, had closed. The valve could not be reopened from the control ,

roon. The loss of instrument air to containment resulted in an Over Pressure Protection System low pressure alarm and several valve and damper movements:

- letdown line isolation valves closed. Reactor coolant system inventory control was of immediate concern since normal letdown capability had been lost. Charging flow to the reactor coolant system was minimized. ,

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- fan-coil unit outlet dampers repositioned to supply air to the .

containment dome. This action caused loss of ventilation to reactor  ?

coolant pump vaults, so monitoring of reactor coolant pump motor temperatures was increased.

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- cooling water valves to the control rod drive mechanism cooling i system went closed. This produced no immediate operational concern. {

Operators responded to the loss of instrument air (EIIS System Identifier LD) l using approved procedures. An expeditious valve repair plan was instituted,  !

and the operating crew's attention was directed to recovering the instrument I air supply. At 0443, CV-31740 was reopened and held in the open position by  !

bypassing its solenoid operated pilot valve (EIIS Component Identifier V) and  ;

supplying air directly to the valve operator. At 0450, letdown was restored. i A dedicated operator was stationed at the inoperable valve, with communication {

with the control room, to close the valve within one minute if a need was identified. CV-31740 is a containment isolation valve that closes on a containment pressure of 17 psig. The valve had been declared inoperable at 1 0357 and the LCO of Technical Specification 3.6.C.3 was entered. Technical Specification 3.6.C.3 states:

With one or more valve (s) listed in Table TS.4.4-1 inoperable, within four hours:

(a) restore the inoperable valve (s) to operable status or, NRC FORM 366A (5 92)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION AF* ROVED BY OMB NO. 3150-0104

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• EXPIRES 5/31/95 ESTIMATED BJRDEN PER RESPONSE To COMPLY WrrH THis INrORMA!cN COLLECTON RE QUEST: SC O HRS. Fo8PAARD LICENSEE EVENT REPORT (LER) CoMut.cs nEsiRa~2 BsRDEN EstuAn To T E woRuito~

TEXT CONTINUATION AND REOoRDS MANAGEMENT B%NCH (MNBB 7714L U.S. NUCLEAR nEsutAtoRv CoMM:SsoN. wAssiNaToN. oc resucooi. AND To THE PAPERWORK HEDUCTON PRCUECT (31MC104). oFFCE or MANAGEMEN r AND BJDGET, WASHINGTON. DC 205C3-F AC'UTY 9eAME til DOCKET NUMBER (2) Lf R NUMBER (5) PAGE (3) gg SEQutNTiAL REvibcN NUMBER NUMBER Frairie Island Unit 1 - 008 -

00 93 TEXT cu nn nu. ,una a mm. cunn or uRc ram m on (b) deactivate the operable valve in the closed position or, (c) lock closed at least one valve in each penetration having one inoperable valve.

Sin.:e it was desired to keep the inoperable valve open, none of those actions were taken, and plans for a timely valve repair were instituted.

After 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, the valve was still inoperable since the repair had not quite been completed, so the action statement of Technical Specification 3.6.A.2 was entered. Technical Specification 3.6.A.2 states:

If these conditions [for containment integrity) cannot be satisfied, within one hour initiate the action necessary to place the unit in HOT SHUTDOWN, and be in at least HOT SHUTDOWN within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Operators began reviewing plant status and procedures for unit shutdown. They evaluated the expected repair time against the necessary time to perform a controlled unit shutdown. Since it was expected that completion of the repair was imminent, a power decrease was not begun. At 0947 repairs to CV-31740 were complete and the valve declared operable.

CAUSE OF THE EVENT Cause of the event was failure of a coil in a solenoid operated pilot valve, which resulted in closure of CV-31740, Instrument Air to Unit 1 Containment, a containment isolation valve. The solenoid coil had failed open.

ANALYSIS OF THE EVENT The event is reportable pursuant to 10CFR50.73(a)(2)(1)(B) since the " shutdown action statement" of Technical Specification 3.6.A.2 had been entered. Health and safety of the public were unaffected. Plant systems functioned as expected, and timely and prudent corrective actions by plant personnel avoided the need for a unit shutdown. Power reduction had not yet begun when the valve repair was completed and the valve declared operable.

NRO FORM 306A (5 82;

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NRC FORM 36EA U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104

1. 5 92)

EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WfTH THIS INFORMADON COLLECTON REQUEST: 50.0 MRS FORW ARD LICENSEE EVENT REPORT (LER) CoMMEu S REGuo~G suRDtN EsTiuATE To TsE i~roRMAroN TEXT CONTINUATION AND RECORDS MANAGEMENT BFANCH (MNBB 7714). U.S. NUCLEAR ReGuieroRv CouM:SScN. wASmNGroN. oC 2essseos. AND To THE PAPE'RWORK REDUCTON PRCUECT (21540104L oFFCE OF MANAGEMENT AND BUDGET, WASH lNGToN, DC 2Cs03.

FACILITY NAME p) DOCP.ET NUMBER (2) LER NUMBER (S) PAGE(3) yg EEQUENIAL ftEVSON NUVBER NUMBER 05000 282 4 OF 4 Prairie Island Unit 1 -

93 - 008 00 TEXT (tr more space a remarea. use sootons comes of NAC form ac64) p 7)

CORRECTIVE ACTION Upon noting the valve closure, operators attempted to reopen the valve from .

the control room. When that failed, the valve was reopened locally to restore  !

instrument air to containment while repairs could be accomplished. A ,

dedicated operator was stationed at the valve to perform a manual closure if needed. Repair activities were expedited to avoid a unit shutdown.

FAILED COMPONENT IDENTIFICATION L

ASco 125VDC solenoid valve Model NP8321A1E PREVIOUS SIMIIAR EVENTS

• There have been no previous similar events reported at Prairie Island although there was a reactor trip of Unit 1 caused by an air line failure reported as LER 85-009. '

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