ML17325A233

Part 21 Rept Re Corrosion on Leads to Transformers Supplied by Brown Boveri Corp.Initially Reported on 870727.Corrosion Sufficient to Create Safety Hazard Had Transformers Been Installed W/O Repair.Brown Boveri Corp 870526 Ltr Encl

ML17325A233
Person / Time
Site:	Cook
Issue date:	07/31/1987
From:	Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	Murley T NRC, NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
REF-PT21-87, REF-PT21-87-132-000 AEP:NRC:0971B, AEP:NRC:971B, PT21-87-132, PT21-87-132-000, NUDOCS 8708050209
Download: ML17325A233 (9)

Text

p~ ~ REGULATO INFORMATION DISTRIBUTION STEM (RIDS)

ACCESSION NBR: 8708050209 DOC. DATE: 87/07/31 NOTARIZED: NO DOCKET ¹ FACIL: 50-315 Donald 50-316 Donald C. Cook Nuc lear Power Cook Nuclear Power P lant'nit Planti Unit ii 2>

Indiana 5 Indiana 8c 05000315 05000316 C.

AUTH. NAME AUTHOR AFFILIATION ALEXICHiM. P. Indiana & Michigan Electric Co.

RECIP. NAME RECIPIENT AFFILIATION MURLEYi T. E. Document Control Branch (Document Control Desk>

SUBJECT:

Part 21 rept re notification made concerning transformer lead corrosioni per 870727 telcon. Corrosion discovered on leads to transformers sufficient to create potential safety hazards had transformers been installed w/o repair.

DISTRIBUTION CODE: IE19D COPIES RECEIVED: LTR ENCL SIZE:

TITLE: Part 21 Rept (50 DKT)

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD3-3 LA 1 0 PD3-3 PD 1 1 WIQQINGTONi D 1 INTERNAL: AEOD/DOA 1 1 *EOD/DSP/TP*B 1 1 ARM TECH ADV 1 1 NRR CRUTCHF IELD 1 1 NRR VARQAe S 1 1 NRR/DEST/ADE 1 1 NRR/DEST/ADS 1 1 NRR/DLPG/GAB 1 1 NRR/DOEA/EAB 1 NRR/DOEA/QCB 1 NR R B 1 1 NRR/PMAS/ILRB 1 1 FI 01 1 1 RES DEPY QI 1 1 E/EIB 1 1 RGN1 1 1 RGN2 1 1 RQN3 1 1 RQN4 1 1 RGN5 1 EXTERNAL: INPO RECORD CTR 1 1 LPDR 1 1 NRC PDR 1 1 NSIC SILVERe E 1 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 27 ENCL 26

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INDIANA 8 MICHIGAN ELECTRIC COMPANY P.O. BOX 16631 COLUMBUS, OHIO 43216 July 31, 1987 AEP:NRC:0971B Donald C. Cook Nuclear Plant Units 1 and 2 Docket Nos. 50-315 and 50-316 License Nos. DPR-58 and DPR-74 PART 21 - TRANSFORMER LEAD CORROSION U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Attn: T. E. Murley

Dear Dr. Murley:

This letter is to confirm the telephone conversation of July 27, 1987 between Mr. P. A. Barrett of American Electric Power Service Corporation and Mr. D. L. Wigginton of the NRC Office of Nuclear Reactor Regulation regarding notification made pursuant to 10 CFR 21. Specifically, on July 27, 1987 we concluded that corrosion discovered on the leads to transformers (ITE dry-type transformers; 4KV/600V-2000KVA and 4KV/480V-1000KVA), supplied to the D. C. Cook Nuclear Plant by Brown Boveri Corporation, was sufficient to create a potential safety hazard, had the transformers been installed without repair.

In May 1987, we were preparing to install transformers which had been in storage for approximately one year. During the preparation, corrosion and pitting were observed on the leads to bus contact surfaces. The cause of the corrosion was flux residue (ammonium chloride) on the leads, which forms hydrochloric acid in the presence of moisture. The moisture present in a normal storage environment (for electrical equipment:) is sufficient to support the chemical reaction needed to form hydrochloric acid. The acid reacts with the tin-plating, copper, and aluminum at the lead to bus lug contact surface, producing corrosive effects.

The degraded transformers leads have not presented any actual threat to the safety of the D. C. Cook Plant. The degraded transformer leads were identified, cleaned and reterminated prior to installation in Unit 1. The Unit 2 transformers were not placed in extended storage and have been energized; thus, enough heat has been available to sublime the flux residue. 'We have made resistance checks and visual inspections, which have revealed no indication of degradation on the Unit 2 transformers.

We believe that although failure of the Unit 1 transformers could have occurred if the corrosion had gone undetected, this issue did not 870805aa09 87o73i~~-

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Dr. T. E. Murley P:NRC:0971B constitute a substantial safety hazard to the Donald C. Cook Nuclear Power Plant. In addition, we are not aware of other facilities or activities subject to 10 CFR 21 for which any of these transformers have been supplied.

Attached is a letter dated May 26, 1987 from Mr. Tom Marner of Brown Boveri Corporation (BBC) to Mr. Jim Markham of D. C. Cook Nuclear Plant and a Statement of Conformance dated June 19, 1987 from BBC. The letter and the Statement of Conformance address BBC's confirmation of the cause of the corrosion and action that can be taken to resolve the effects of the corrosion.

If you need further information please contact Mr. P. A. Barrett, Nuclear Safety and Licensing (614-223-2034).

This document has been prepared following Corporate procedures which incorporate a reasonable set of controls to insure its accuracy and completeness prior to signature by the undersigned.

Very truly yours, M... P. Al xich

,Vice President cm cc: John E. Dolan W. G. Smith; Jr.'- Bridgman R. C. Callen G. Bruchmann G. Charnoff NRC Resident Inspector - Bridgman A. B. Davis - Region III

Attachment to AEP:NRC:0971B Letter, T. Harner (BBC) to J. Markham (D. C. Cook Plant),

Dated May 26, 1987 Statement of Conformance from BBC, Dated June 19, 1987

tray 27,87 09t34 BBC-BROMN-BOVERI-INC P.02

'; Vrsnetcrmer a Switch Dleicn BBC Brown Bovert Power Equipment, )nc.

Trttalonnot & StNltch DMslon Btovrn Bovel Powttt Bplptttttttl, ltto, Slate Route 42 P. O. Box 38 Bland, VA 24315 Hay 26, 1987

~,HEET y g7 Mr, Jim Hnrkhattt p D, C. COOK NUClelAR PLANT CK Red Arrow Highway 'gv Bridgtnan, MI 49n16 7 OA~<

Dear Hr. Marldtam SUB J: Corrosion This letter is to confirm our conversation on 5-22-87, concerning the corrosion on the aluminum bus on the transforttters supplied on our 8.0. f24-30985S thru 24-30999S.

After vciwiag the photographs that you seat, wc can confirm that this corrosion was caused by the acid flux used on the braided flexes during thc tinning process, The flexes were not cleaned's thoroughly as they should have been after they were t3nned, The acid flux residue on the flexes attacked the aluminum bus and caused the corrosion. The flux that was used is STAY-CT.P~

soldering and tinning flux made by the J. V. Harris Co. of Cincinnati, Ohio.

This f1ux can be removed using l>ot water. Ne suggest that you c1can the flexes that you have using a stainless steal wire brush'and hot water only, The aluminum bu-". Should also bc cleaaed witTi a stainless steel wire brush to rcmove the corrosion and provide a smooth contact surface. A corrosion inhibftor should be applied to both surfaces before re-connecting. Hc recomtttend PFHRTROX "A", made by the Surndy Co. of Norwalk, Conn. However, any inhibitor ruitable for this type of connection may be used.

Ve apologize for the inconvenience th1s has caused. However, the electHcn1 nor the mechanical reJiability hag in any way been harmed by this incident, I

Regards

+~)'t Tom Harner Pield Service Coordinator Mes Patterson Engineering Manager

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BBC BROWN BOVERI POWER EQUIPMENT, INC.

P.O. Box 38 BLAND, VA. =-. 24315 BROW'0vER>

STATEMENT OF CONFORY~CE We certify that the listed equipment and required documentation for same meet the requirements of the purchase and applicable specifications:

P.O. No: 02875-821-5X Rev.

SPECIFICATION: DCCEE-199- CN 6 200 CN Rev.

PRIME VENDOR: BBC Brown Boveri, Inc.

SUPPLIER: BBC Brown Boveri, Inc.

ADDRESS: P.O. Box 38. Bland, VA. 24315 IDENTIFICATION: This Statement of Conformance covers the material and workmanshio to re air the transformer bus corrosion roblem on Bland S.O. No.'s 24-30985 S to 30989 S, 30993 S, 30995 S to 30997 S.

NOTE: The repair process of these transformers have been reviewed and approved by BBC. The modification will not affect the equipments integrity. The following repair process procedure is required.

Sand the terminations smooth with a hand held power sander or sanding block at least as large as the termination area to insure a smooth and uniform surface. After sanding, the following procedure should be followed to reconnect the braided flexes.

1. Clean aluminum contact area with a stainless steel- wire brush.

2. Immediately coat the contact area with Alco g2 Electrical Joint Compound. Abrade contact area through compound with a stainless steel wire brush. Do not remove compound from contact area.

3. Clean the tinned copper braided flexes with a stainless steel wire brush and hot water. After cleaning, coat the contact area with Alcoa g2 Electrical Joint Compound.

4. Hake connection. Torque bolts to 50 ft./lbs.

We certify that field repairs were performed in accordance with the above procedure under Brown Boveri d'irection.

Rev., 1 - Dated 6/19/87 Si ature -.

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