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POWER REACTOR EVENT NUMBER: 31890

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i FACILITY: BYRON REGION: 3 NOTIFICATION DATE: 03/04/97j UNIT: [1] [2] [] STATE: IL NOTIFICATION TIME: 16:22 [ET)

RX TYPE: [1] W-4 -LP, [2] W-4-LP EVENT DATE: 03/03/97EVENT TIME: 00:00(CST)

I NRC NOTIFIED BY: PAUL WENC LAST UPDATE DATE: 03/04/97HQ OPS OFFICER: HENRY BAILEY

NOTIFICATIONSEMERGENCY CLASS: NOT APPLICABLE10 CFR SECTION:CCCC 21.21 UNSPECIFIED PARAGRAPH

VERNON HODGE, RVIB NRR

UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE CURR PWR CURR RX MODE

1 N N O HOT SHUTDOWN 0 HOT SHUTDOWN ~

2 N Y 100 POWER OPERATION 100 POWER CPERATION

EVENT TEXT

10 CFR PART 21 NOTIFICATION - CRACKING OF VITEC TRANSFORMER CORES

THESE TRANSFORMERS ARE INSTALLED IN VARIOUS SAFETY-RELATED CIRCUITS BOARDS.TEMPERATURE CHANGES IN THESE CIRCUIT BOARDS COULD CAUSE ASSOCIATEDINSTRUMENTATION ~!O DRIFT OUT OF RANGE. THE SAFETY-RELATED APPLICATIONSWHERE THIS TRANSFORMER HAS THE MOST POTENTIAL IMPACT ARE THE DELTATEMPERATURE PROTECTION FUNCTIONS (NRA CARDS) IN THE REACTOR PROTECTIONSYSTEM (RPS). THE DRIFT IN THE RPS COULD CAUSE A CHANNEL TO TRIP RESULTING l

IN A LOSS OF REDUNDANCY IN THE DIVERSE TRIP FUNCTION.1 i

NOTE: THIS ISSUE ALSO APPLIES TO BRAIDWOOD UNITS 1 AND 2 AND TO ZIONUNITS 1 AND 2.

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LTR: BYRON 97 5045HLE- 2.01.0703

U. S. Nuclear Regulatory CommissionWashington,DC 20555

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Attention: Document ControlDoak

Subject: Byron Station Units 1 and 2Braidwood StationUnits 1 and 2Zion Station Units 1 and 2

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10 CFRPart 21 Noti 6 cationCrackingof VITEC TransfonnorsNRC Dockets 50-454 and 50455

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NRC Dockets 50-456 and 50-457NRC Dockets 50-295 and 50-304

Reference: "Transfonner Crackmg", Westinghouse Potential Issue NS AL-96 006,dated De=M 26,1996.

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This notiBcation is submitted in accordance with the requirements of 10 CFR Part 21,

Section 21.21(a),21.3a(3), and 21.3d(l)..

Idsntification of Fari1Mn and Cem,anents

Byron Nuclear Generating Station Units 1 and 2Braidwood Nuclear Generating Station Units 1 and 2

Zion Nuclear Generatin8 tation Units 1 and 2S

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| 7300 Process Protection System Integrated Circuit Cards (h% NLP, NSC, NLL,'

NMD,NCH, NVP, am!NSA applications)i

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NRA card model #: 2837A15001, various date codes supplied by Westinghouse kom

October 1991 through 1993.

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! During innentiatian and testag of the RTD By-Pass =ndificarian at Braidwood Station,a output driR was observed with increasing temperature on several RID angdidor

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(NRA) cards Investigation revealed that it appeared to be a problem ==aalaw witha new revision of this model circuit card. The vendor (Westinghouse) was ihrmallynouSed and seven (7) examples of the suspect cards were sent by ConiEd to

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Westinghouse for evahastion.'

A Nuclear Safety Advisory Letter (NSAL) noti 8 cation from Westinghouse was4

provided to potentinDy adEscted liosasses on December 26,1996 (reference).,

WsM= determined that the drit on these cards ranged flrom 140 mV to 1.763

volts (10 volt span) after several minutes at exposures to temperatures of1407.i|

Westinghouse traced the y.J.S;a to a transformer that isolates the input and output.,

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stages of the NRA card. M::;1My, Westinghouse returned the suspect jitransformers to the vendor eens which they were supplied. 'Ilie vendor, VITEC,

. determined that the core of the transformers had been arsobed during the 1

| manufheturing process, and that an increased temperature could cause tbs i=dna=e* !:to decrease resulting in a change in the output of the card. Westingbouse did indicate

| that any driR in the cards would be detectable when the cards were instaued andcalibrated in the ranks aAer preliminary calibration on an outender eerd. The!' j temperature in the racks is estimated to be 100 - 110 T.

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I IWestinghouse determined that the potentially defective transformers are used on seven1

| other 7300 cards. The cause of the defect in the transformer is believed to be due to! excessive tightening of the screw that holds the core together prior to potting the

assembly during the manufheturing process VITEC has been the supplier of these| transformers since late 1991. However, VITEC made a change to nylon screws in'

1994 and subsequent testing of these new transibrmers has demonstrated that thei

problem does not exist fbr the newer cards.

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Tuna afDiscoveryi1

Comed determined that the failure was a potential defect subject to the provisions of10CFR21 on January 7,1997. Final determination that the defbet was reportable per

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| 10CFR21 was made on March 3,1997.-

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Zion Station has not idemined any instaBations of the suspect circuit cards at Zion.The population of potendany asected cards at Byron and Braidwood Stations isestensive due to the number of circuit card applications that have been identiSed byj

W ='--d - The exact number of potentiauy delbetive components is not currently!

available due to the uncertaisy ofwhich date codes are actually instaDed in the plants.'

| Comed has deterunned that the applications of concem Dom a 10CFR21 standpointare the NRA, NLP, and NSC cards. This is due to tbs isolated output ihnetionfor the!

spplications serviced by these specific cards.

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Byron and Braidwood Stations have initiated actions to identify all circuit cards withi;

the affected date codes Once the population offmpacted cards is fully idamified, the;

j affected cards will be replaced, where appropriate. Westinghouse indicated that it is| unhkaly that many trana6mners with cracked cores asist. In addition, it has been] determined that an instaHad cards are located in rooms that are supplied by safety

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related, redundant HVAC systems that are designed to snaintain appropriatetemperatures. The safety related applications where this transformer issue has thei

most potentialimpact are the AT protection functions (NRA cards) because ofreactor:| trip concerns These applications are subjected to y#adic channel checks and it is

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| reasonable to assume that any signi5 cant non-conservative calibration drtit would bedetectable during channel checking activities. Both Byron and Braidwood Stations!

j have documented W.Miity assessments that conclude that there is reasonable,

{ assurance of operabGity fbr the potentially affected applications. Completion ofinspection and/or replacement of the l'a:=eW population ofcircuit cards for both;

Byron and Braidwood Stations wiD be completed prior to the and of the next refbaling'

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outage on each unit.,

Byron and Braidwood Stations have inspected all spare circuit cards in Stores to! ensure that no additional potentinny affected components are placed into service.j2

10 CFR 21 Ev=b= dan.

The safety related applications where this transforrner issue has the most potential?4

impact are the 4T protection functens (NRA cards), There is some potential that|

| ; defective cards would not be detected during installation and initial calibration. Anegative drift in the estibration of detective cards could result in nona:enservative&f adaan fbr both AT and the corresponding setpoissa This could result in a lack,

of redundant reactor trip fbaction. Thersibre, Comed has d-'=daad that the|

| identined delbct does represent a subseanrfal sqfety harauf per the requirements of,

| 10CFR21 and is reportableto the NRC.i

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Questions pertaining to this notification 1.hould be addressed to either,

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Bradley1 Adarna PeterI. Wicyk !

; Site Engineenns EIAC Engineering !.

Comed Byron Station Comed NES, ETW III |'

4450 N. Gennan Church head 1400 Opus Place,'

Byron, Illinois 61010 DownersGrove Blinois 60515 !

(815) 234-5441 x2979 (630) 663 7264I

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Sincerely,

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[K. L. Ormesser!

Site VicePresident ,

Byron Nuclear Station

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ec: A. B. Beach, Regional Administrator RIII j

S. Burgess, Senior Resident laspector (Byron)C. PhiHips, Senior Resident Inspector (Braidwood)

1 A. Vogel, Senior Resident Inspector (Zion)6R Assa-NRRC. Shiraki-NRROffice of Nuclear Facility Safety - IDNSDCD - Licensing, Suite 400, Downer Grove

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