05000271/LER-1992-001, :on 911219,spurious HPCI Condensate Storage Tank Low Level Alarm Received & Suction Transferred to Torus.Cause Unknown.Proper Consendate Storage Tank Level Verified & HPCI Suction Transferred

:on 911219,spurious HPCI Condensate Storage Tank Low Level Alarm Received & Suction Transferred to Torus.Cause Unknown.Proper Consendate Storage Tank Level Verified & HPCI Suction Transferred

ML20092F244
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	02/20/1992
From:	Reid D VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-001, LER-92-1, NUDOCS 9202190190
Download: ML20092F244 (4)

LER-1992-001, on 911219,spurious HPCI Condensate Storage Tank Low Level Alarm Received & Suction Transferred to Torus.Cause Unknown.Proper Consendate Storage Tank Level Verified & HPCI Suction Transferred

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(iv), System Actuation
2711992001R00 - NRC Website

text

_ _ _ _ _

VEllMONT YANKEE NUCLE 61t POWEll COltPOllATION

'xf P.O. Box 157, Governor Hunt Road Y

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Vernon, Verrnont 05354 0157

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(802) 257-7711

.1 February 13, 1992 U.S. Nuclear Regulatory Cornmission Document Control Desk Washington, D.C. 20555 REFERENCEt Operating License DPR-28 Docket No. 50-271 Reportable occurrence No. LER 92-01 Dear Sirst As defined by 10 CFR 50.73, we are reporting the attached Reportablo occurrence as LER 92-01.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION n

Donald A. Reid Plant Manager ces Regional Adtninistrator USNRC Region I 475 Allendale Road King of Prussia, PA 19406 I b O O[,0

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9202190190 920220 e

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TITLt (4) pputious N$c1 Suction Transfer due to unknown cause CVENT DATE (5)

Ltk NUM8tR (6)

RefORT DATE (7)

OTHED FACIL!?ita INVOLVED (*)

MONTH DAY YEAR YtAR 8tQ 5 RtV4 NONTH DAY YEAR FACILITY NAMt$

Porri'T No.

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EKFECTED MD DAY YR SUBMISSION DATE (15)

Yt8 (if yea, corplete EXFECTED SUBMISSION DATE)

X NO MLhn:ACT (Limit to 1400 spaces, i.e., approx. fifteen single-space typewritten lines) (le) l On 12/19/91 at 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br />, during normal operation with Reactor power at 100%, a spurious liigh Pressure Coolant Injection (llPCI) (+BJ) Condensate Storage Tank (CST) lov leval alarm was received and suction to llPCI transferred from CST to the Torus. Approximately 15 minutes later at.1025 hours0.0119 days <br />0.285 hours <br />0.00169 weeks <br />3.900125e-4 months <br />, after. reviewing plant parameters (proper. CST level), operators returned HPCI t

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l suction back to the CST.

I l

A functional test was performed on the all L

The root cause of the - event is unknovn.

l applicable llPCI suction transfer logic. The tests did not reveal-any failed components, out of calibration components, or any other abnormalities which would allow for root cause analysis.-

The event was determined to be not-reportable by Vermont Yankee. However, as a result of subsequent-discussions With.the on-site resident inspector this event is being voluntarily considered as an Engineered Safety Feature (ESF) actuation and reported under 50.73 (a)(2)(iv),

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3 TEXT (If more space is required, use additional NRC Forra 366A) (17)

MERifII.0LOF EYXNJ On.12/19/91 at 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br />, during normal operation with Reactor power at 100%, a spurious

- High Pressure Coolant Injection (HPCI) (*BJ) Condensate Storage Tank (CST) lov level alarm came in and out. Valves to HPCI transferred to align the system suction from the CST to the i

Torus. This was the expected system response upon receipt of a CST low level signal. No i

ir.itiation of other !!PCI system equipment occurred.

Approximately 15 minutes later at 1025 hours0.0119 days <br />0.285 hours <br />0.00169 weeks <br />3.900125e-4 months <br />, after verifying proper CST level, operators successfully returned llPCI suction back to the CST to perf orm a functional test and verify operability of HPCI. A successful f unctional test was completed at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />. The HPCI system remained operable throughout the event.

CME orEYMT An extensive testing and troubleshooting ef fort was performed to determine the cause of the HPCI suction transfer. The functional test consisted of the testing of both CST level i

transmitters loops including all associated level switches, power supplies, level recorders and process-computer monitoring. The applicable HPCI pump suction control logic, HPCI suction transfer valve control, and llPCI Condensate Storage Tank lov level annunciation vere also tested. All equipment responded properly, tests results were reviewed as satisfactory and there vas no evidence of component failure.

The root cause of the event is unknown. However, the circuitry that performs the valve transfer is normally energized and momentary interruption of power or circuit continuity would cause the resultant HPCI suction transfer. There was no evidence of a CST low level signal on the process computer or the level recorder. This is consistent with expected indications if i

a momentary loss of power or circuit continuity occurred. Initial and subsequent interviews with plant personnel did not reveal any ongoing activities which would have c.wsed a power interruption or loss of circuit continuity. There were no testing, surveillances or systems i

operations being conducted at the time of the event. Due to the single occurrence and the successful testing performed, this is considered as an isolated event.

MAMBISOY MM1 The events of this report did not have adverse safety implications. The HPCI system remained operable throughout the event. Proper CST and Torus levels vere available. 1:PCI suction transferred as designed on receiving a transfer signal. Operators successfully transferred the HPCI suction back to CST fifteen minutes later.

- This event was determined to be not reportable by Vermont Yankee on 1/3/92. However, the onsite NRC hesident inspector thought it was reportable as an Engineered Safety Feature (ESF) actuation and as such meetings vere held on 1/17/92 and 1/21/92 to discuss VY's basis for datermination. Vermont Yankee's basis was the f act that al though HPCI is an ESF, the HPCI suction transfer to the Torus is not an ESF and actuation of a non ESF part of an ESF system was therefore not reportable. This conclusion was a result of a review of the applicable FSAR sections, NUREG-1022. and Supplements 1 and 2. Since Vermont Yankee and the NRC Resident

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FACIL1TT NAM (1)

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3 VERMONT Y A N lt t t NUCLEAR FOWER STATION 0

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TEXT (If more space is required, use additional NRC Form 366A) (n)

ANALYSIS 0F EVFNr fgyn.t,fd)

Inspector did not agree on this issue, VY committed to conservatively assess the event as an ESF actuation and submit this as an LER vithin 30 days of 1/21/92.

C(Li@l;CIIVE ACTIDMS fil101tT_JULLCulMECT1YE ACTIONS Immediate corrective actions included verifying proper CST level, transf erring liPCI suction to its pref erred source the CST and functional testing of all 11PCI suction circuitry.

10Nft,,TfRM CHRHECI1Y.tLACT3.DNii Long term corrective actions vill consist of continued monitoring of HPCI suction transfer circuitry. If any sitnilar events occur, additional investigation and corrective actions vill be initiated as appropriate.

AEE1Il0NAt,1NEOM61103 There have been no similar events of this type reported to the commission in the past five

years, i