05000423/LER-1993-011

LER 93-011-00:on 930731,MSSV Lift Setpoint Drift Occurred Due to Unknown Cause.Reduced Setpoint for Power Range Neutron Flux High Trip to 10%.W/930830 Ltr

ML20056H454
Person / Time
Site:	Millstone
Issue date:	08/30/1993
From:	Scace S, Young J NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-011, LER-93-11, MP-93-684, NUDOCS 9309090353
Download: ML20056H454 (3)

LER-2093-011,

Event date:
Report date:
4232093011R00 - NRC Website

text

. -

"[~ORTHEAST UT1UTIES oenerat == saen s=m Berno conne==

l $e' sher N aSIner N tI Y. $ c Un7 P O. Box 270

( *

'I' P[asIbi sYIc5Yo3cma, HARTFORD. CONNECTICUT 06141-0270 rev as: Naceae Enew cms"> (203)6E5-5000 August 30, 1993 MP-93-684 Re: 10CFR50.73(a)(2)(i)

U.S. Nuclear Reculatorv Commission Document Control Dess Washincton. D.C. 20555

Reference:

Facility Operating License No. NPF-49 Docket No. 50-423 Licensee Event Report 93-011-00 Gentlemen:

This letter fonvards Licensee Event Report 93-011-00 required to be submitted within thirty (30) days pursuant to 10CFR50.73 (a)(2)(i).

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY p

/ Stephen L Sdee Vice President - Millstone Station SES'JSY:dir

Attachment:

LER 93-011-00 cc: T. T. Martin Region I Administrator P. D. Swetland, Senior Resident Inspector, Millstone Unit Nos.1, 2 and 3 V. L. Rooney, NRC Project Manager, Millstone Unit No. 3 080si 9309090353 DR 93083o r3 ADOCK 05000423 i r PDR Q fs ) ;

dr/4 pgy&Q gi

4

.s -

'*jag)o-m x6 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3160-0104

• ' EXPIRES: 5/31/95 ESTIMATED BURDEN PE A AE SPONSE TC OOMPLY wTe T 4 s FFO4MAHON COLLECTION PEOJE ST. 50 0 HAS FORWAAD t co'e s aEa> = s suceN E s-e Tc T*

LICENSEE EVENT REPORT (LER)  !'70 A V A TION AND RECOR?S MANAGEMENT BRANOd i iVUEE 7774 U$ NUOLE AR P E GUL A T om O C'MS S CN.  !

AASwNG'ON DC 2350-030 AND TO THE FAPEAA'DA( i (See reverse for recur ed number of d:gris/charactere for eacn clock) REDS 0' ion c40. E c ta so-c,.cun orrict oc MANAsEMENT i A'JO MUDGET AA$aCN3TDN DC 2Dfd3 FACILIW NAME til DOCKET NUMBER (21 FAGE (3) '

E!: stone Nuc:ea* Power Station Un:t 3 05000423 1 OF 2 i TITLE (4; Ma:n Steam Safety VeNe Utt Setooint Dnft E WNT DATE c5: LE A NUMBE A #Ea AEPORT OATF (71 CTMER FAOiUTIE S INVOLVED EE)

V ONh LA*

• EAR *EAA H,9R[a#+ $E %,({- ugNT- gas vgAn FACCTV NAVE DOCnET NJnER 05000

• ^ 0" " *E "E 7 ""EE" 08 30 93 07 31 93 93 011 - 00 05000 OPE R ATING TH:S REPORT IS EDNG SUBM:TTED PUASUANT TO THE REQUIREMENTS OF 10 CFR L : #Cneck one or more) (11)

Em 3 21 A 2: 2 4 3E : c ' 5 . 73. a i .! n 73 7' *!

POWER E 4M'a : ir M 36.t ' 50 73;a) @ s) 73 71 ci LEvct oc, 000 .- ' 4ra < o ' E: x >2 st 73,an2.s OTHEA 2D 4:F:a Y K 73.a. E ; m K 73 a .i M-li A; ispe; $ ,. %t33.aa tea ancmTec N=: '

20 405. a ; ret M 73 ' ai 21 ' h ' $C 73 3 ) :2; f i t 'E , bC* M Af  !

t n 4:' a, is 6r 73 a3 2.n so 72. a ,,2. o LICENSEE CONTACT FOR THis LER f12)

NAME r . r :>cw: u we n u - f., A.,3 enw Jettrey S. Young, Eng,neer, Ext. 6442 (203) 447-1791 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRfBED IN THIS REPORT (13)

REoD M Ae;E REPOAT AB E C AuSE D ETEU 0 r/PDN R T vW d AC7 UREA "O M4DS C AUSE SYSTEV COMDONENT MANJF A C T V4E A T O NPROS SUPPLEMENTAL REPORT EXPECTED (14) EXPE CTE D

1. O D* #E*"

yrs gg SUBM!SSION f' yes co~o tte EM ECTED SJEMTSON D ATE: X WE W ABSTRACT tm : u ec unces i e awc.cmase", 's s ve spacea meuraten enes; 06)

On July 31.1093 at 2]OO wnh the plant m Mode 3 (Hot Standby), ten of twent) Main Steam Safety Yahes did not lift wnhin the tolerance allowed by Technical Spec;hcanons. (One of the ten did not lif t withm +/-39 of s the (etpomt. ) The dncmery was made durmg the plant shutdown for a refuelmg outape.

The root cau'e of ihn esent s unknown. Setpomt drift is a problem that has occurred previously but the cause a ha no, been determmed No immediate correctn e act:on was required because the plant was already m Hot Standby and the setpomt for the Power Range Neutron Flux H ph Tnr was alreach reduced to HF~c. However, a!] ten vahes were reset and senhed to be w:thm the requ: red tolerance.

As action to prevent recurrence, the umt is pursump relaxation of the 4/- 19 tolerance to + - 3%. This would

, hase caused tune of the ten sahes to be withm thn specthcanon.

]

6

• l

a NAc Fvm 3%^ U.S. NUCLEAR REGULATORY COMM!SSION APPROVED BY OMB NO. 3150-0104 i

' ** EXPIRES: 5/31/95  :

ESTIMATED BUADEN PER RE SPONFE To covFLY W'Tt* TH!$

LICENSEE EVENT REPORT (LER) woauccN ecuEcTcN nEcuEsr se e Has sonwAne CoVVDC S AE G A RD'NG BURDEN ESTMATE To THE

- TEXT CONTINUATION IN:ORMATON AND RECORDS MANAGEVENT BRANON t e dMNBR 7741 U S. NUC_E AF< RE G;iAT c,RY OoMM:SSCM l' W A St UNGT ON D 205ss-CDD1 AND To THE PAPERWORK AEDUOTON PAoJECT (3150-01CA 04tcE oc h/,ANAGEMENT un euc cET wAs m oToN oc 2 Deca ,

F ACUTY NWf it) Joc%ET NJVBEA f2; LE A NJVEc A 61 PAGEf3' i YEAP kd^' b[5 '

Mastone Nuolear Power Station U 13 05000423 93 - 011 - 00 02 OF 02 i TEXT 4 we spaa i , ewes ae aceto a eemer c' NA: cem 3M A. 07)

1. Deccnnuon of Etern ,

On July 31.1993 at 2100 wnh the plant m Mode 3 (545 degrees Fahrenheit and 2250 psia), ten of the twents Mam Steam Safet3 Vahes did not hit within the tolerance (+/-1W required by Techrucal Specificanons. One of the ten hited at +4. lr c. The discovery was made dunng performance of the 16 month sunetHance for the hit settmps of the safenes. Five of the vahes hited below the tolerance and fue vahes hfied above the tolerance Eight of the vahes required adjustment and were retested to senf t that they we,e wnlun the e ster tolerance. The other two sahes lihed othm the 1cc tolerance on subsequent tests without adnutment. The one vahe which lif ted at +4.19 did not require adiustment.

No immediate correcove acuan was required because the plant was m Hot Standby and the setpomt for the Power Range Neutron Flux High Tnp was already reduced to 109 by procedure when the discovery u at made. H ow ever the vahes were adjusted as necessary and verified to be withm the 15 tolerance.

II. Cause of Esent ,

The root cause of the safety vahes dnftmp from it "r setpomts is not known. Setpomt dnft is a ,

returnng problem but the cause remams undeterr 111. Anahw of Esent This event is being reported m accordance with 10CFR50.73(a)(D(i)(B), as a condition prohibited by Techrucal Specificanons. Limitmg Condinon for Operanon (LCO) Tabie 3.7-3 requires that all Steam Lme Safety Valves hft at +/-1"c of the lih setting. The hit setung pressure corresponds to ambient condinons of the vahe at nommal operaung temperature and pressure. It is assumed that the setpoint dnh occurred someume dunng plant operanons as the vahes were tested immediateh upon reachmg Hot >

Standby.

This esent posed no sigmficant safe 13 hazard. The safety valves hfted withm the lower pressure bounds anahred for a Steam Generator tube rupture coincident with loss of offsne power and the high pressure bounds of the Vain Steam System design.

Setpomt dnit on Main Steam Safeties is a recurnng condnion. This phenomenon is not a problem L umque to M:Ustone 3. It has been recogmzed b3 c,ther utihties. Histancal mformanon pronded by the  ;

Nuclear Network has shown that there is a concern that the hmns of +/-19 are too restncuve. Millstone j 3 is pursumg a relaxauon of the +/-19 cntena in fasor of +/-39 tolerance. The Accident Anahsis in  !

the FSAR assumes a 39 drift j i

IV. Correcth e Acuen i

All vah es w ere reset to withm the required tolerance.

I As acuan to present recurrence. the una is pursump relaxation of the as found tolerance to +/-39. A l request for a change to Technical Specificauons will be submitted before December 31,1993 i V. Addnional Informati.e.n Other Licensee Esent Reports (LERs) for setpoint drift of Mam Steam Safety Vahes are 91-002. ,59-010, 57-036 and 67-009-02. i Ells todes .i S gnps Component Mam! Reheat Steam System - RB Rehef Yahe - RV Nuc w mA wi