05000336/LER-1993-016

LER 93-016-00:on 930729,reportability Determination Made Re Analysis for Boron Dilution Event.Caused by Inadequate Review of Results of Boron Dilution in Relation to Plant Operating Conditions.Boron Results revised.W/930827 Ltr

ML20056G500
Person / Time
Site:	Millstone
Issue date:	08/27/1993
From:	Doboe S, Scace S, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-016, LER-93-16, MP-93-674, NUDOCS 9309030197
Download: ML20056G500 (4)

LER-2093-016,

Event date:
Report date:
3362093016R00 - NRC Website

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NORTHEAST UTlWTIES ce=='o" = 'S**a$ = Se"'acoa*" "

Tne cmeticat U71 And Pow Crpnpany I wester- vissmenvaens E.ectne compaay P.O Box 270

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HARTFORD. CONNECTICUT 05141-0270 (203)5E5-5000 4

August 27, 1993 ,

MP-93-674 '

Re: 10CFR50.73(a)(2)(v)  :

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U.S. Nuclear Regulatory Commission l Document Control Desk ,

Washington, D.C. 2055, ,

Reference:

Facility Operating License No. DPR-65 Docket No. 50-336  :

Licensee Event Report 93-016-00  !

Gentlemen: I This letter forwards Licensee Event Report 93-016-00 required to be submitted within thirty (30) days pursuant to 10CFR50.73(a)(2)(v)-

t Very truly yours, l I

NORTllEAST NUCLEAR ENERGY COMPANY <

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Step er E. cace Vice President - Millstone Station i

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Attachment:

LER 93-016-00 cc: T. T. Martin. Recion 1 Administrator P. D. Swetland, Senior Resident inspector. Millstone Unit Nos.1, 2 and 3  !

G. S. Vissing, NRC Project Manager, Millstone Unit No. 2  !

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F ACLlTv NAME ($; DOCAE T NJMSti- :2) W"F Millstone Nuclear Power Station Unit 2 o f 5! of ol 01313 l 6 1lod0l3 ,

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Inconsistency Between Safety Analyns and Plant Operatmp Procedures E VE W A T E 'E LE A NUWE A W C{PDA' LA'E .7i ONEO. FACtAr 5 FNVO; VED ts 4 Mot Te D a v' VEAA YEAR . .

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%E A CODE Sandra Doboe Associate Engmeer. Ext. 46%  ; 9 3 4 4 7 )y 7 9 3 C OMRETE OM LINE FOR E ACs COMDONENT F Aku:E DE SORGED IN TH=$ AEPORT M3, 1

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VE S P' p s enmme'e EXPECTED SJBM'E SLON O ATE) NO l l l AesTPA T u.mq ; m t spaces ,e ana w aeymeen sages:.a:. tvoew te meo oci l On July 29,1993, at 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br />, with the plant operatmg m Mode 1 at 100cc pouer, a reportabihty l determmanon was made concern:nc the anahsis for a boron diluuon esent. The result of this analysis and plant operatmg procedures p: aced confhetme requuements on the operat. ion of the Shutdown Coolmg (SDC) system.

The October 1955 boron diluuon exent analp:s reqmred a minimum SDC flow of 2450 gallons per minute (gpm) m modes 4 and 5. Plant operaung procedures regt, ire the SDC flowrate to be less than 1500 gpm to present vortexine at the SDC sucuan line when in mode 5 and with the Reactor Coolant System (RCS) dramed to the centerhoe of the reactor reael hodeg.

The boron ddution exem was reanalyzed. The following assumptions were changed:

The nurnber of operable charpmg pumps was changed from 3 to 2 for RCS cold leg temperatures less than 300 degrees Fahrenheit.

The shutdown margin requirement for mode 5 was increased from 2P r ak/k to 3.6"cak/k The revised analysts requires no SDC flowrate restrictions for modes 4 and 5. and a mmimum SDC fiowrate of 950 rpm m mode 6.

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1. Deccmnon of Esem On July 29.1093, at 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br />, wnh the plant operaung m Mode 1 at 100cc power, a reportabihty determmanon was made concernmg the analps for a boron diluuon esent. The resuh of this analysis and plant operatmg procedures placed confheung requirements on the operation of the Shutdown Coohng (SDCJ system The inconsivtencies between the boron dilution event analysis and the plant operaung procedures were discosered dunny a general renew of the Final Safety Analyss Report (FSAR).

There vere no maior operator actions or automauc or manually imtiated safety responses resulting from ths es ent.

The October 19M baron diluuon event analysis required a mirumum SDC flow of 2450 gallons per mmute f gpm) m modes 4 and 5. Plant operatmg procedures require the SDC flowrate to be less than 1500 ppm to prevent vortexmg at the SDC (ucuon hne when m mode 5 and with the Reactor Coolant Ssstem (RCS) drained to the cemerhne of the reactor vessel hotleg.

The boron diluuon event was reanalyzed. The followmp assumptions were changed:

The number of operable charpmg pumps was changed from 3 to 2 for RCS cold leg temperatures less than 300 degrees Fahrenheit I The shutdown margm requirement for mode 5 was increased from c2rak/k to 3.6"cak/k Th- revned analvss requires no SDC flowrate restocuens for modes 4 and 5, and a mmimum SDC flourate of c50 gpm in mode 6.

11. Crse of Event l The root cause of the event has been determmed to be an inadequate renew of the results of the boron  ;

ddution esent analyns m relation to plant operatmg conditions and procedures.

111. Anahss of Dent Ths esent is bemp reported in accordance with 10CFR50.73(aH2Mvj(D), which requires the reporung of any event or cond: tion that alone could hase presented the fulfillment of the safety function of systems that are needed to mi*igate the consequences of an accident. ,

The potennal safety consequence of this event is erosion of shutdown margin leadmg to enucahty, if the boron dilanon event occurred with the RCS dramed to the centerhne of the reactor sessel hotleg and  !

wnh the shutdown marpm at its mmimum s alue of 2rc akm. l l

The safety consequence of this event is rninimized by pl ant operatmp procedures. The procedures for plant cooidown and refuehng operations close and tag all valves which are sources of di!uuon water to the RCS i The safety consequence of this event is funher minimr J oy the normal operaury pract Ce of mamtammg the mode 4 required shutdown boron cons ration in mode 5. The mode 4 shutdown margin requirement is 3.6cc ak/k.

IV. Conecthy Acuon The corrective acuons are based on the changes m the assumptions and resuhs of the revised boron dihtuon event analyss.

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ol 5l 0l 0l ol3 l3 l6 9l3 Oj1l6 0l0 0l 3 OF 0l3 v n,we n-s ,e-n a. ,o= .r.nn w s , a Techmcal Specificanon changes are being submnted to the NRC to meet the following requirements:

A max: mum of 2 charpmg pumps are ciperable when the temperature of one or more of the RCS cold legs is less than 300 degrees Fahrenheit.

The flowrate through the reactor core must be greater than or equal to 1000 ppm in mode m The flouTate through the reactor core must be greater than or equal to 1000 ppm in all modes whenever RCS baron concentranon is beme reduced.

l The Core Operatmp Limns Report is being rev: sed to increase the mode 5 shutdown margm requirement  ;

from 2Gak/k to 3Fcak/k.

The pertmern operating procedures will be revised to compl) with the Technical Specification changes.

The FSAR is bemy changed to reflect the revised boron dilution analysis.

1 V. A d6tional Irif orration I There were no faded components durmg this esent i

i Simdar LERs: 80-05.56-10  :

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Ells Codes for referenced systems and components:

BP - Shutdown Cochng System AB - Reactor Coolant System CD-P-G045 - Charging Pumps N*C hr'Y; 3til 46-% ;