B10885, Final Deficiency Rept SD-36 Re Design & Const of Main Control Board Welds.Initially Reported on 830513.Welds Repaired & Approved by S&W & Reliance.Welds Analyzed by Reliance & Approved by S&W

Final Deficiency Rept SD-36 Re Design & Const of Main Control Board Welds.Initially Reported on 830513.Welds Repaired & Approved by S&W & Reliance.Welds Analyzed by Reliance & Approved by S&W

ML20080F240
Person / Time
Site:	Millstone
Issue date:	09/08/1983
From:	Counsil W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, B10885, SD-36, NUDOCS 8309190231
Download: ML20080F240 (8)

Text

gg General Offices

• Seldon Street, Berlin, Connecticut ErY e,s$a w.", P.O. BOX 270

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September 8,1983 Docket No. 50-423 B10885 Dr. Thomas E. Murley, Regional Administrator Region i U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406

Reference:

(1) W. G. Counsil letter to J. M. Allar, Millstone Nuclear Power Station, Unit No. 3, Reporting of Potential Significant Deficiencies in Design and Construction: Main Control Board Welds (SD-36), dated May 13,1983.

Dear Dr. Murley:

Millstone Nuclear Power Station, Unit No. 3, Reporting of Potential Significant Deficiencies in Design and Construction: Main Control Board Welds (SD-36)

In Reference (1), Northeast Nuclear Energy Company (NNECO) reported a potential significant deficiency as required by 10CFR50.55(e) involving inadequate welds on main control board panels supplied by Reliance Electric Company.

On May 17,1983, Reliancu Electric Company with the assistance of Stone &

Webster implemented an inspection and repair program for all boards supplied by Reliance. Unacceptable welds as identified by Reliance were listed in two categories. The first category included welds requiring rework and the second was for welds requiring analysis to determine if they possess sufficient structural integrity to survive a design basis earthquake. The following is a listing of the two groups.

Main Control Board Repair - 200 Analysis - 234 Primary Relay Board Repair - 2 Analysis - 24 Termination Cabinets Repair - 21 Analysis - 114 830919023183090g3 -

DR ADOCK 05000 qe

- An agreement was made between Stone & Webster Engineering Corporation and Reliance Electric Company to ;use Stone & Webster welding procedures to perform field repairs on the centrol board panels. - The Reliance Q.A.' Manual was revised to include the nece sary field repair work. This revised Q. A. document

. became a controlled document on file at Stone & Webster in Boston.

Attachment I contains -' the justification for inspection of painted welds.

Reliance stated .that throughout their inspections of suspect welding, the deficiency discovered with welding involved dimensional problems, i.e., welds which were undersize, concave, or not filled out. Attachments 2 & 3 address inspection of inaccessible weld areas.

- All welds requiring repair have been completed by' Stone & Webster and accepted by Reliance and Stone & Webster Q. A. All welds requiring analysis have been analyzed by Reliance and approved by Stone & Webster and Northeast Utilities Service Company (NUSCO) as having sufficient structural integrity to withstand a design basis earthquake.

i NNECO considers these corrective actions sufficient to resolve this deficiency.

As such, this letter constitutes our final report closing out all items related to SD-36. We trust the above information satisfactorily addresses your concerns.

Please feel free to contact my staff if you have any further questions.

Very_truly yours, J

NORTHEAST NUCLEAR ENERGY COMPANY Wo ff W. G. CounsF Senior Vice President

• R s e RCMtA Et0T i RELIANCE ELECTRIC S 4900 Lewis Rd.

Stone Mountain. GA 30083 (404) 938-4888 INSPECTION OF PAINTED WELDS When the weld problem was first discovered, we had several control boards in our shop which were already painted. We performed an inspection of 100% of the welds (4500 welds) with the paint on. One of the panels was chosen to be subjected to an additional sample inspection. The number of welds in the lot size were 4000. Five hundred painted welds had already been identified as needing repair. We chose a random sample of 315 welds. This corresponds to an Inspection Level III of MIL-STD-105D which is single sampling for tightened inspection. The 315 welds were wire brushed to remove all paint.

Of the 315 welds, three butt welds were found to have a slight concavity. All of the filltets were good. MIL-STD-105D shows that the panel would be accepted based on the sample inspection. For the Millstone III boards, this translates U into an 0.065 AQL, which means that 195 defective welds (6.5 per 1000) could remain undetected (based on an estimated 30,000 welds in the Main Control Board, panels 1-8). These findings adequately support our proposal for inspecting the welds in the other sections with the paint on. We have used this approach with GA Power FL Power & Light, LA Power & Light, LILCO and Texas Utilir.tes; all of which were built in the same time period as the' Millstone boards. The inspector qualifications for the sample inspection are the same as those being used in the control boards for Millstone 111.

t2*r Richard Morrow, Q.A. Manager Custom Panels Division

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V H e Mark No.3CES 9 MCQ Mfg. Reliance Electric Co.

4900 Lewis Rd. St. Mtn. Ga TD /*bt99

DACM MEN 7 1 RELIANCE ELECTRIC S U

INACCESSIBLE AREAS FOR WELDING INSPECTION The areas in the Main Control Boards which are not accessible for weld inspection are those vertical surfaces covered by subpanels and wireways. The accessible vertical areas were surveyed in order to establish the relationship between the '

vertical areas and the good / bad welds. The type of weld hidden behind the sub- '

panels and wireways is the fillet described by our drawing WS-1-NU-C (SWEC I welding tech sheet W70G). '

A sunanary of the survey follows:

! Total Accessible Total No. Total Defective Total Area l MCB'No. Vert. Area (Sq Ft) of Welds Welds Inaccessible (Sq Ft)

MB1, 2 224 428 4 49 )

MB3 122 238 11 32 MB4 110 279 5 95 O

V MB5.6,7 219 447 2 79 MB8 147 378 4 28 TOTALS 822 1770 26 283 The projection for the inaccessible areas follows:

Defects per Total Area Expected No.

[ MCB No. Square Foot --

Inaccessible Of Defects MB1,2 .018 49 1 MB3 .090 32 3 MB4 .046 95 5 MBS,6,7 .009 79 1 MB8 .027 28 1 SWEc> aA a Northeast Utiliti e Millstone Unit 3 K..ehf /h)

Mark No'4CES#flIQ3 SL 7 Mfg. Reliance Electrio Co.

O V 4900 Lewis Rd. St. Mtn. Ga.

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O MB 1 & 2 INACCESSIBLE AREAS FOR WELD INSPECTION There is a total Of 273 square feet of vertical surface in this section, of which 49 square feet is not accessible for weld inspection.

Of the 428 welds inspected on these vortical surfaces, the following were found to be defective:

l

! Weld No. Defect Description l .

145-A WS-1-NU-C W70G. Wald is 1 3/4" long. It has 1/8" of overlap at each end. The required length is 1".

t 130-A WS-1-NU-C, W700. Tack weld (1/4" long) is between j two fillet welds of proper size, length & spacing.

I 125-A WS-1-NU-C W70G. The 2" fillet has a small hole in one end (1/32" Us). AWS D1.1 allows more porosity than is present.

l 123-R WS-1-NU-C, W70G. Excessive porosity was removed by l grinding. Rewelding was not necessary.

l l

• l MB3 i

There is a total of 154 square feet of vertical surface in this section, I

of which 32 square feet is not accessible for weld inspection. .

Of the 238 welds inspected on the vertical surfaces, the following were

, found to be defective:

l  :

l Weld No. Defect Description l

100-R WS-1-NU-C, W70G. Incomplete fusion.

l 102-R WS-1-NU-C W70G. Incomplete fusion.

l 104-R WS-1-NU-C, W70G. Incomplete fusion.

110-R WS-1-NU-C W70G. Incomplete fusion.

103-R WS-1-NU-C, W70D. Incomplete fusion.

The repair did not include welding.

105-R WS-1-NU-C, W70G. Incomplete fusion.

115-R WS-1-NU-C, W70G. Incomplete fusion. g gM 1, The repair did not include welding. Millstone Unit 3 118-R WS-1-NU-C, W70G. Incomplete fusion. P.O. 2424 10 - 45 A 117-R WS-1-NU-C, W70G. Incomplete fusion. ,,,, y} E ,, 6s Bea:Er j q 116-R WS-1-NU-C, W70G. Incomplete fusion.

WS-1-NU-C, W70G. Incomplete fusion.

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N rth3 cst Utilttico M1110 tono Unit 3 1 2-y e 1 Maric No.3CES+ MM E @ 7 Mrg. Reliance Electrio Co.

MB4 4900 Lewis Rd. St. Mtn Ca.

~TI) 17/74 There is a total of 205 square feet of vertical surface in this section, of which 95 square feet is not accessible for weld inspection.

Of the 279 welds inspected on the vertical surfaces, the following were found to be defective:

Weld No. Defect Description 060-A WS-1-NU-C W70G. Incomplete fusiod on the last 1/4" of the 2 1/2" long weld. The weld length minimum length is 1 inch.

055-R WS-1-NU-C W70G. Incomplete fusion. The repair did not include welding.

061-R WS-1-NU-C. W70G. Incomplete fusion. The repair did not include welding.

063-R WS-1-NU-C, W70G. Incomplete fusion.

064-A WS-1-NU-C, W70G. A tack weld was left between two welds of adequate size, length & spacing.

() MB5, 6 & 7 There is a total of 298 square feet of vertical surface in this section, of which 79 square feet is not accessible for weld inspection.

Of the 447 welds inspected on these vertical surfaces, the following were found to be defective:

Defect Description Weld No.

6-204A WS-1-NU-C W70G. Incomplete fusion.

5-214R WS-1-NU-C, W70G. Two fillets 3/16" x 1" are missing.

MB8 There is a total of 175 square feet of vertical surface in this section, of which 28 square feet is not accessible for weld inspection.

Of the 378 welds inspected on these vertical surfaces, the following were found to be defective:

Weld No. Defect Description

. C, 265-R WS-1-NU-C, W70G. Incomplete fusion.

264-R WS-1-NU-C, W70G. 3/16" x 1" fillet missing.

202-A WS-1-NU-C W70G. Fillet size 1/8" rather than 3/16" 203-A WS-1-NU-C, W70G. Fillet size 1/8" rather than 3/16"

O When we complete the inspection of the other sections of the Main control Boards, we will determine a percentage of defects which will be applied to the inaccessible areas. This percentage will include an appropriate safety factor. Analysis will then be used to determine acceptability of the inaccessible areas.

Richard Morrow Q.A. Manager Custom Panels Division 6LdE C,t b Ugliti[s Northeas Millstone Unit 3 Os y a b c _

Mark No.3M6# /#O3 I l 7 Mfg. Reliance Electric Co.

4900 Lewis Rd. St. Mtn. Ga.

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, ~ During our' inspection of the Maia control Boards, it was deter =f aad l that the weld areas that were inacessaible were prada=hatly in the rear of l ,

the boards frequent.ly covered by the sub-panels and the wireways. The type l i

of weld hiidea behind these ebetructions is the fillet weld joining the stiff-ener(e) to the penal skia and fully described la our drawing No. WS-150-4.

N inspectiam of these typical joista revealed that the walds are oversised (1/4" rather than 1/8") and longar la lamath (11/2" to 2" rather thes 1")

than the =1=f- Armspectise rguirement:a.

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h analyttral evaluarica of these welds was done using both the  ;

l 1/4" and the 1/8" fillet sige. aed in all but one fastanca, the 1/8" sise wslda analysed. possessed sufficient margins of safety under the desig.

basis loading condition. N 1/8" sise weld judged to be M pts was sely .975" long campared to the =f nt===g requirsummt of oma tech langth (weld ar.omaly ammbec 007A MD-1). .

t As sock. if fifty percent of the weld area of a 1/4" aise fillet weld is missing, or every othat weld is bad. the remaining us1dm would still preseos sufficient structars1 istogrity weder the worst case ==f ==fr loading ecaditinm. .

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- Our Kaspectica of the main boards also revealed that most of these defects were readamly spread out throughout the control board and addittomally j mo two. ces bundred percest rejectable welds were found side by side. Saeed a

on our previously submitted statistical evaluation as the sapected aunbar of

), defects, and the store described evaluattaa Saliance feels that there are act F any significan: number of taurassible weld defects that woeld comerce.ine tha j aafsty and perforasace of the boards.

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