ML20024B798

Final Part 21 Rept Re Potential Problems W/Loop Power Supply Card Heat Sinks of Westinghouse 7300 Process Protection Sys (SD-40).Initially Reported on 830602.Concurs W/Westinghouse Hardware Changes

ML20024B798
Person / Time
Site:	Millstone
Issue date:	07/01/1983
From:	Counsil W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
REF-PT21-83-002-000 10CFR-50.55E, B10832, PT21-83-002-000, PT21-83-2, NUDOCS 8307110390
Download: ML20024B798 (3)

Text

g General Offices

• Seldon Street. Berlin, Connecticut q P.O. BOX 270

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July 1,1983 Decket No. 50-423 B10832 Dr. Thomas E. Murley, Regional Administrator Region I U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406

Dear Sir:

Millstone Nuclear Power Station, Unit No. 3 Reporting of Potential Significant Deficiencies in Design and Construction: Westinghouse 7300 Process Protection System Potential Problems with NLP Card Heat Sinks (SD-40)

As required by Title 10, Code of Federal Regulations Part 50, Paragraph 5)(e),

Northeast Nuclear Energy Company (NNECO) reported a potential significant deficiency in the design of Millstone Unit No. 3 in a June 2,1983 telephone conversation between your Mr. Johnson and our Mr. R. E. Lefebvre.

Our notification to you was made under the advice of Westinghouse, who on June 1,1983 notified affected customers and provided an initial notification of a potential problem to the NRC.

Attached is a copy of Westinghouse letter NS-EPR-2774 from E. P. Rahe to R. C. DeYouag, dated June 8,1983. We have reviewed the subject problem concerning the failure of adhesive bonds for thermal heat sinks on the inverter transistors associated with loop power supply (NLP) cards. We agree with the Westinghouse assessment of the failure mode and concur with the corrective action of hardware changes which eliminates the adhesive. As such, it is our position that this letter, including the attached Westinghouse report / correspondence, constitutes our final report on this significant deficiency.

We trust the above information satisfactorily responds to your concerns.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY

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• Project Engineer NORTHEAST UTILITIES SERVICE COMPANY P.O. Box 270 Hartford, Connecticut 06141 '

NORTHEAST UTILITIES SERVICE COMPANY MILLSTONE NUCLEAR POWER STATION UNIT NO. 3 7300 Process Protection System Potential ProbTems With NLP Card Heat Sinks and NTC Card Relays

Dear Mr. Orefice:

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With reference to the subject sotential problems, attached is a copy of

= Westinghouse sent on June 8,1983. letter NS-EPR-2774 from E. P. Rahe to R. C. DeYoung which was TheYe"pWt#iit'f ar ~ problems were verbally discussed with a member of your projects organization on June 1, 1983.

Please foregoing. feel free to contact us if there are further questions regarding the J.b.;,,x- _..

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Very truly yours, ,

J WESTINGHOUSE ELECTRIC CORPORATION 1r.ht= 1 - A A R. L. Hofe'r , fnager NUSCO Projects Gregg/nnc/12510: 1 Attachment ec: S. Orefice 4L 4A R. W. Ackley 6L, 3A enum

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Division of Inspection and Enforcement U.S. Nuclear Regulatory Commission Phillips Building

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Bethesda, MD 20014

Dear Mr. DeYoung:

This is to confirm the, telephone conversation of June 1, 1983, between ,

Messrs. D. H. Rawlins and C. G. Draughon of Westinghouse and Mr. N.

V111alva of the NRC. In that conversation, Westinghouse notified the f NRC of two potential problems within the Westinghouse 7300 Process Protection System. This was re plants and under 10CFR 50.55(e)for ported plantsunder under10CFR 21 for operating construction.

Westinghouse has advised its NSSS utility custor.ers of this determination. The two concerns are described below.

1. Heat $1nks on NLP Card Description of Problem .

Heat sink adhesive failures have been identified at several utilities and were reported to Westinghouse as field deficiencies.

All reported field failures have occurred only on the loop power supply (NLP) cards. Westinghouse has determined that NLP printed circuit cards shipped from Westinghouse Industry Electronics Division (WIED) between August 1,1980, and September 1,1982, were equipped with a thermal heat sink assembly on the inverter transistors that are subject to potential failures in the adhesive bond in the thermal link assembly. The adhesive bond is between an insulating washer and the thernal link (see Attachment 1). Failure of the band can cause the heat sink plate to separata from the thernal ifnks and fall off of the printed circuit board. The plate is conductive metal and under certain circumstances could cause shorting of low level signals if it became wedged between cards in the card frame. The affected printed circuit boards are:

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( Note: Previous Sub-Teveis did not contain heat sinks.' Th's assembly sub-TeveT jdentification sticker is attached to the solder side of the card near the front edge. It is not the revision identified on the front edge.

The adhesive failure mechanism or expected number of hours of system operation before failure is not defined. All reported problems have occurred under normal system usage or storage. To date, these heat sink adhesive failures have not resulted in any damage to the Westinghouse 7300 Process Protection System nor have these failures resultedinanyJossofsystemsafetyfunctions.

CorrahtiveAction Weskinghouse has committed to provide replacements for the heat sinks that are subject to this potential adhesive fa1Ture meenanism. These heat sinks can be identified by inspection of the printed circuit card for hex nuts visible on the top side of the assembly. See attached drawing 404A605 (superceded) (Attschment li) . The new style heat sink has screw heads visibTe from the top side of the assembly (see Drawing 403A947 Attachment 2).

NTo justify continued piant operat. ion until these heat sinks can be -

p replaced with the new design, Westinghouse reconnends that utilities inspect their 7300 Process Protection System for separated heat t

sinks and remove any heat sinks that are separated. This inspection should be conducted during each periodic system test until the heat

. sinks are replaced. In addition, Westinghouse has determined that:

a. Tne NLP card can operate satisfactorily without the heat sink.

b. If a heat sink disiocates during operation and causes a failure,

, the probability of the failure being detectable is high. .

Attachment 3 to this letter is a Tisting of piants which have been i shipped the potentia 1Ty defective NLP cards. In addition to t

WIED supplies this type of equipnent Westinghouse direct y to Architect NSSS Engi plants, iieers for utility balance of plant (BOP) use and also to other N555 vendors.

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2. NTC Card Relay Description of Problem During seismic testing of the Temperature Channel Test (NTC) card, contact bounce was experienced in the mercury relay utilized on this card. This intermittent contact bounce will result in signal l saturation of the downstream RTD Amplifier (NRA) card in the That and Tcold circuits of the Westinghouse 7300 Process Protection l ( System. In these systems, filters are adjusted to maintain a total l

time constant of approximately two seconds for the R7D/ filter combination. Since the filter is downstream of the relay, the e ' *

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characterist.. f of the channei response depb s on the time constant

~ of the filter. For RTD's specified by Westinghouse, the filter has been set at either zero or two seconds depending on the type of RTD i

(fast or slow response) ut1712_ed. For applications utilizing unfiltered signals, saturation of the NRA card could delay initiation of the Overtemperature - Detta T and Overpower - Delta T l

trips. ' For applications utilizing a fi'itered signal, NRA card saturation would not spur 1ous piant trip. prevent plant only trips,occurs but could as a result result ic of a

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This problem contact bounce induced by a seismic event. A list of piants  :

utiliz'ing filtered and non-filtered circuitry are provided in .i Attachments 4A and B. This Tist also provides a reference for all Westinghouse piants utilizing 7300 process protection equipment. '

Corrective Action Attachment 48 Tists the plants utilizing unfiltered signals which may experience trip delays due to intermittant relay contact bounce during a seismic event. A replacement relay is being developed and tested and most of these plants will have the replacement reiays installed prior to operation.

For operating plants with unfiltered signals. Westinghouse recom= ends that the existing filters be set for a one second response. This will eliminate the potential delay and ensure that the plant will trip on demand. If the plant does not have -

sufficient time response margin to accomodate the one second -

response, then the relays must be bypassed with permanently f installed jun,pers until the replacement relay is installed.

If you require additional information on these subjects, please contact C. G. Draughan of my staff at 412-374-5761.

Very truly yours, ..

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E. P. Rahe, Manap r Nuclear Safety Department

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ATTACHMENT 3 (1 a 0220 '00/06/15 08:51

( Plants Having Potentially Defective NLP Cards '

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IED records shcw the following projects have scme NLP Cards with the old style heat sink assemblies which should be replaced. -

I. Supplied with Original of NSSS Process Protaction Systens:

SITE P.S. OF N.H. - SEABROOK KO-RI #2 - KOREA NAPOT PT. - PHILIPPINES VANDELLOS - SPAIN WOLF CREEK CALLAWAY #2 NAP 0T PT. - PHILIPPINES TAIWAN POWER - MAANSHAN #1 TAIWAN POWER - MAANSHAN #2 KO-RI #5 - KOREA CP&L - SHEARON HARRIS #1 DUKE POWER - CATAWBA #1 C DUKE POWER CATAWBA #2 N.E. UTILITIES - MILLSTONE #3 -

S.C. ELECTRIC & GAS - SUMMER LEMONIZ, SPAIN ASCO SPAIN .

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COMM. EDISON - BYRON #1 COMM. EDISON - SYRON #2 COMM. EDISON - BRAIDWOOD #1 c COMM. EDISON - BRAIDWOOD #2 TEXAS UTILITIES - COMANCHE PEAK #1 TEXAS UTILITIES - CDMANCHE PEAK #2 CALLAWAY #1 WOLF CREEK #1 CALLAWAY #2 P.S. OF N.H. - SEABROOK II. Supplied in Other Than NSSS Systens:

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VEPCO - NORTH ANNA i VEPC0 - NORTH ANNA l 50. CAROLINA ELECTRIC & GAS - SUMMER

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l $0. CAROLINA ELECTRIC & GAS - SUMMER .

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50. CAROLINA ELECTRIC & GAS - SUMMER AMERICAN ELECTRIC POWER IND. & MICH. POWER ,

KANSAS GAS & ELECTRIC ,

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PHILIPPINES - NAPOT PT.

TAIWAN POWER - MAANSHAN ALMARAZ - SPAIN PHILIPPINES - NAP 0T PT.

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f, SITE CON ED - INDIAN PT. #2 TEXAS ' UTILITIES - COMANCHE PEAK IND. & MICH. POWER (AEP) RVLS

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TVA - SEQUDYAH TVA - SEQUDYAH NOTE: - = WNSD ALSO BEING NOTIFIE0 AS THIS WAS AN NSD ORDER

• = THIS SITE IS ALSO ON THE SYSTEMS LIST

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. ATTACHMENT 4A 0{# '00/06/1508558

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FlitarefPlants' .

(Utilize a Fast Response RTD)

• Joseph M. Farley Unit 1

• Joseph M. Farley Unit 2 North Anna Unit i

, Wm. B. McGpire Unit 1 North Ann.a Unit 2

• Wm. B. McGuire Unit 2

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Non-Ffitered Plants

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Comanche Peak Units 1 and 2

, Seabrook Units 1 and 2 Beaver Valley Unit 2 i

Byron Units 1 and 2 Braidwood Units 1 and 2 Vogtie Units 1 and 2 Shearon Harris Units 1 and 2 Catawba Units 1 and 2 South Texas Units 1 and 2 M1Tistone Unit 3 Marbie Hill Units 1 and 2

• Virgil C. Sue:r.er -

Callaway Unit 1 f Wolf Creek Unit 1 4

• Operating Plants .,

Overtemperature N-16 channels for these plants utilize Tcold signal. HRA card saturation would not prevent plant trips, but could result in a spurious plant trip.

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