ML20029C128

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LER 91-004-00:on 910216,unexpected Trip of 'B' Steam Generator Feed Pump & Subsequent Manual Reactor Trip Occurred.Cause Unknown.Monitoring Capability Added to Sgfp Circuitry & Design Change made.W/910318 Ltr
ML20029C128
Person / Time
Site: Millstone Dominion icon.png
Issue date: 03/18/1991
From: Criscione J, Scace S
NORTHEAST NUCLEAR ENERGY CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-004-01, LER-91-4-1, MP-91-241, NUDOCS 9103260216
Download: ML20029C128 (3)
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NORTHEAST tmuTMS o.a e aca s ansu a senaconaui'eut 1 Nof.7ela'[sIed."e'ttNIY[cNa* P.O. Box 270 L 'T2 IS***II'II'YEYE*A*n, ruie.ast tww Ene p, tv vaany H ARTFORD. CONNECTICUT 06414-0270 12031665-tiODO Re: 10CFR50.73(a)(2)(iv)

March 18, 1991 MP-91-241 U.S. Nuclear Reculatory Commission Document Contr'ol Dtsk Washington, D.C. 20555

Reference:

Facility Operating License No. DPR-65 Docket No. 50-336 Licensee Event Report 91-004-00 Genoemen:

This letter forwards Licensee Event Report 91-004-00 required to be submitted within thirty (30) days pursuant to paragraph 50.73(a)(2)(iv)

Very truly yours, NORTHEAST NUCLEAR ENERGY COh1PANY f

  1. 1 No Stephe . S ace irector, hiillstone Station SES/JLC:mo

Attachment:

LER 91-004 00 cc: T. T. h1artin, Recion I Administrator W. J. Raymond. ' Senior Resident inspector, hiillstone Unit Nos.1, 2 and 3 G. S. Vissing, NRC Project hianager, hiillstone Unit No. 2 fnf

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] YE S (H vos. ctimp.ete f.w&ECTCO SUBM SSION D ATti NO b' l l l ADETR ACT lumii to 1400 sosces. i e. . awomim.te+y f4f teen smg+-sc,.co typewntlea a*nes) 116 On February 16i 1991, with the umt operatmg at 10007 power the 'B' Steam Generator Fred Pump (SGFP) unexpectedly tripped at 1731 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.586455e-4 months <br />. The pump uns reset and the speed of the 'A' SGFP was raised from 4430 to 5100 RPM. As the 'D' SOFP was accelerated, it caused low >uction pressure for both pumps. The 'B' SOFP tnpped again, was reset tripped und reset a:ain. The 'A' and 'D' pump suction pressuret, again alarrned low. The 'A' SGPP then tripped. Low level alarms occurred in both steam generators. At 1733 hours0.0201 days <br />0.481 hours <br />0.00287 weeks <br />6.594065e-4 months <br />, the l reactor was manually tripped because of decreaung SG levels. The cause of the iniual 'f.' SOFP inn is j unknown, l

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1. Determtion of I' vent l 1

On February 16. 1991. with the unit operating at 1009 power, the T Steam Generator Feed Purnp (SOFP) unexpectedly tnpped at 1731 hourt The pump was reset and the speed of the 'A' SOFP was raised from 4430 to $100 RPM. As the 'D' SOFP was accelerated. it caused low suction pressure for i both pumpn The 'B' SOFP tripped again, was reset, tnpped and reset again. The 'A' and 'D' pump .

suction pressures again alarmed low. The 'A' SOFP then tnpped. Low level alarms occurred in both steam generators. The 'A' SOFP was then reset. At 1733 hours0.0201 days <br />0.481 hours <br />0.00287 weeks <br />6.594065e-4 months <br />. the reactor was manually tripped because of decreaung 50 lesels. Operators performed EOP 2$25 " Standard Post Tnp Actions

  • Reactor Tnp Recovery". Steam Generator levels were restored using the running 'A' SOFP per procedure.

!!. Cnme of Event The cause of the initial 'D' SOFP tnp is unknown. There is no hrst hit inp system and no alarms were ,

present prior to the 'B' SOFP (np which would have indicated an unusual condition. Under normal SOFP trip scenanos, pre-tnp alartns or degrading plant conditions are expected.

The cause of the subsequent 'A' and 'B' SOFP tnps was most likely from low suction pretsure or low flow by the 'A' SOFP running at 5100(+) RPM while the 'B' SOFP was returning to speed.

Immediate follow-up activines:

The 'B' SOFP ws reset and run and the trip system was successfully tested.

- All SOFP trips and alarms were i.rsted with no ciscrepancies found.

I!!. Anahsie of Event This report is being submitted pursuant to the requirements of 10CFR5033(a)fD(iv), "any event or '

condition that resulted in the manual or automaue actuation of any Engmeere.f Safety Feature (ESF),

includmg the Reactor Protection System (RPS)*. There were no safet; we *equences resulting from this event smce normal post inp procedures were followed and all safety sMA functioned to restore the unit to a stable condnion.

IV. Corrective Action No r.orrective action was taken to resolve the 'B' SOFP tnp because the root cause is unknown.

However, the following actions were taken:

Alonitoring capab aty was added to the SOFP circu try to differentiate between a mechanical or electrical fault fa any future events.

A Plant Design Change was irutiated to add a first hit monitoring system to the SOFP circuit.

While existing procedures had no direct bearing on. the feed pump recovery, the alarrn section of OP 2321. Feedwater System, was revised to assist the operators m restoration of a tnpped feed pumn and prevent any followup trips. All shifts have been trained in these procedure changes.

Y, Additional Information Similar LER's: 5 7-002, 8 7-011, 5 7-009, b *-012, ogwm m

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