ML20198E898

Final Deficiency Repts 86-01 & 86-03 Re Defective Spot Welds on Cable Tray Hanger Strut Matl.Initially Reported on 860306.Engineering Evaluation Performed for Hangers Remaining W/Suspect Control Numbers

ML20198E898
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	05/20/1986
From:	Miosi A COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
1690K, 86-01, 86-03, 86-1, 86-3, NUDOCS 8605280324
Download: ML20198E898 (7)

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i CommonweaMh EC* son e

j/ C One First National Plaza, Chicago, Ilknois k ("O 7 Address Azply to: Post Office Box 767.

Chicago, llhnois 60690 7

l May 20, 1986 l

Mr. James G. Keppler j

Regional Administrator Region III

)

U.S. Nuclear Regulatory Commission j

799 Roosevelt Road j

Glen Ellyn, IL 60137 I

1 1

Subject:

Byron Station Unit 2 l

j Braidwood Station Units 1'and 2 10 CFR 50.55(e) Nos. 86-01 and 86-03 Final Report

[

Defective Spot Welds on Cable Tray Hangers l

j NRC Docket Nos. 50-455. 50-456 and 50-457 k

References:

(a)

A.D. Miosi to J.G. Keppler, dated March 6, 1986 I

(b)

K.A. Ainger to J.G.

Keppler, dated March 12, 1986 1

i j

Dear Mr. Keppler:

The above reference provided information concerning a i

deficiency reportable pursuant to 10 CFR 50.55(e) regarding i

defective spot welds on cable tray hanger strut material at Byron l

Unit 2'and Braidwood Stations.

This letter provides an update to j

our previous response and is considered to be a final report.

DESCRIPTION OF DEFICIENCY t

i During the installation of cable tray in Braidwood Unit 2 i

containment,.the Unit 2 electrical contractor, G.K. Newberg

{

(GKN),. identified. installed cable tray hangers which had j

discrepant spot welds.

GKN initiated Nonconformance Reports j

(NCR) 331-00001 and 331-00002 which together identified 30 3'

cable tray hangers with discrepant spot welds.

The cable tray hangers in question were prefabricated by Systems Control Corporation (SCC) utilizing P1004A Unistrut material.

The P1004A is a spaced.back-to-back channel fabricated out of two-j P1000 single channels held together by side ~ plates which are 4

spot welded to the channel at 3 inches on center.

Some of the spot welds'on the cable tray hangers which join the side plates j'

to the channel as identified by GKN appear to be improperly j

fused.

GKN submitted the two NCR s to Commonwealth Edison j

Company (Ceco)'for their evaluation.

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. Upon review of the GKN NCR's 331-00001 and 331-00002, Ceco initiated NCR 793.

In performing the 50.55e reportability

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review of NCR 793, Ceco determined that the identified problem was reportable.

In addition, CECO notified Unistrut Corporation (Unistrut) of the problem.

Unistrut made a visit to the Braidwood site and confirmed.the P1004A material in question was their product and would review their records to help identify the source of the problem.

ANALYSIS OF SAFETY IMPLICATIONS The safety significance of the discrepant spot welds has been fully assessed.

An engineering evaluation, based on destructive testing, of hangers with discrepant spot welds and suspect material with no discrepant spot welds indicates that there is no safety significance.

CORRECTIVE ACTION TAKEN-BRAIDWOOD In order to determine the scope of this problem, CECO decided to perform a walkdown of the installed cable tray hangers comprised of P1004A Unistrut members in Braidwood Units 1 & 2.

Sargent & Lundy developed an inspection criteria to be used on the walkdown.

Each of the members were inspected for spot weld fusion by observing for gaps between the side plate and base channel and then attempting to pass thin mylar through the welded area.

Welds were considered discrepant if the thin mylar could be passed through the welded area.

The hangers in which discrepant welds have been observed were mapped indicating the location of each discrepant weld.

The base channel control numbers were recorded for all hangers inspected.

The base channel control number indicates the year it was i

rolled, the operator of the rolling machine and the steel coil number.

Furthermore, Unistrut QC documentation references the control number.

The results of this walkdown are summarized in i

the attached table.

The number of hanger members in which discrepant welds were found and the total number of hanger members inspected are shown for each control number identified'with discrepant i

welds.

This information was passed along to Unistrut for their i

review.

A review of the control numbers of the discrepant i

material shows that the majority of the material was manufactured in the 1978 time frame.

Unistrut concentrated their efforts on reviewing production and quality control records.

Based on this record review, Unistrut has established that 580 feet of rejected P1004A material was inadvertently shipped to l

SCC and used to supply cable tray hangers for the Byron /Braidwood project which was primarily used for Braidwood Unit 2.

This shipment (1,000 feet) was received by SCC in August 1979.

This material consisted of rejected 20. foot pieces of P1004A material that were accumulated for rework l

l during 1979.

This material was partially reworked in July of 1979.

The control numbers shown in the attached table with an 8 prefix would be considered suspect since they were produced in this time period.

However, a significant number of adjacent discrepant spot welds have been observed only on. control numbers 8E7806, 8E7829 and 8N7791.

It appears that the suspect material was utilized primarily for Braidwood Unit 2 cable tray hangers.

This is supported by the results of the walkdown.

In addition, Braidwood Unit 2 were the last hangers fabricated by the SCC.

Prior to the 1,000 foot shipment, shipments totaling 2,000 feet (1,500 feet - 1977, 500 feet - March 1979) were received by SCC.

This 2,000 feet of nonsuspect material would be consumed by the earlier scheduled units (Braidwood 1, Byron 1 & 2) before the suspect material was received by SCC in the August 1979 shipment.

A comprehensive review of records by Unistrut indicates that the inadvertent shipment of 580 feet of discrepant material was an isolated occurrence.

Quality Control (QC) records are maintained for all material produced by Unistrut.

All material which is rejected by QC is tagged and held for disposition.

The 580 feet of suspect material was accumulated during 1979, tagged as rejected, and held for rework.

The walkdown shows that some of the material was partially reworked.

The disposition for this reject tag was never completed by Unistrut QC.

The material was apparently shipped prior to the completion of the rework and final QC acceptance.- Unistrut QC records show this to be the only case of.a material reject tag with incomplete QC disposition, and therefore, considers it to be an isolated case.

Based on the construction schedule considerations, it was determined to replace the Unit 2 containment hangers which contained discrepant welds.

The Unit 1 hangers with discrepant spot welds have been evaluated case-by-case based on a spot weld strength determined from destructive testing of a sample of discrepant material.

Even though the' case-by-case review determined the hangers to be acceptable, all of the Unit 1 hangers with the exception of one will be repaired or replaced.

The remaining hanger had only one spot weld broken and will be left as is.

Hangers with a suspect control' number, but no discrepant spot welds, were evaluated generically based on the allowable spot weld strength determined from testing.

These hangers were determined to be acceptable with a design margin'of 2.0, or more.

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It is apparent that, in addition to the 580 feet of suspect material, there exist occasional discrepant spot welds.

Unistrut expected that occasional discrepant spots may not be detected by their Quality Assurance program.

An engineering evaluation was completed to assess this condition on a generic basis.

The maximum allowable spacing between intact spot welds was determined to be 9 inches.

Therefore, two consecutive spot welds could be discrepant on all four rows of welds and still be acceptable.

In order to confirm our conclusion that this problem is isolated to cable tray hangers supplied by SCC, a walkdown was i

also completed for all installed conduit and junction box hangers in Units 1 & 2 which utilize Unistrut P1004A.

There are 2357 conduit and junction box hangers utilizing P1004A of f

which discrepant welds were observed on only seven hangers.

Due to this low frequency of occurrence, these discrepant welds are considered isolated cases.

These hangers will be repaired or replaced.

Conduit and junction box hangers have been fabricated in a later time period as compared to cable tray i

hangers.

They have also been fabricated by a different contractor, Mechanical, Inc.

For these reasons, it has been concluded that the scope of the P1004A issue is isolated to cable tray hangers received from SCC.

Therefore, no further action is planned for conduit and junction box hangers.

CORRECTIVE ACTION TAKEN-BYRON A walkdown of all cable tray hangers comprised of PlOO4A Unistrut members has been completed for Byron Unit 2.

The members were inspected using the same inspection technique at Braidwood Station and all discrepant welds were recorded.

The results of this walkdown are summarized in the attached table.

The number of hanger members in which discrepant welds were 4

found and the total number of hanger members inspected are shown for each control number.

Only 13 members of 233 inspected were found to have discrepant welds.

Commonwealth Edison Company Nonconformance Report F-1045 has been initiated to track this concern.

The scope of the suspect P1004A material is limited and has been established at Braidwood Station per 55(e) No. 86-03.

The suspect material appears to have been utilized primarily for cable tray hangers at Braidwood Unit 2.

The results of the Byron Unit 2 walkdown support this conclusion, t

I

.. 4 The Byron Unit 2 hangers with discrepant spot welds have been evaluated case-by-case, based on a spot weld shear strength determined from destructive testing of a sample of discrepant 4

material.

They were determined to be acceptable.

Hangers with a suspect control number but no discrepant spot welds, were evaluated generically based on the allowable spot weld strength i

determined from testing.

These hangers were determined to be l

acceptable with a design margin of 2.0, or more.

SUMMARY

In summary, results of the Unistrut PlOO4A. demonstrate that:

1.

The scope of the issue is 580 feet of discrepant material i

which was inadvertently shipped to SCC and used to fabricate cable tray hangers.

Walkdown data, supplemented by vendor information, leads to the conclusion that these i

cable tray hangers were primarily in Braidwood Unit 2.

2.

Occasional discrepant spot welds are expected by Unistrut for nonsuspect material.

An engineering evaluation was performed which accepts this condition on'a generic basis.

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3.

An engineering evaluation was performed for all cable tray hangers remaining with suspect control numbers.

The evaluation was based on a weld strength determined from destructive testing of a sample of discrepant material.

All hangers with suspect control numbers were determined to l

be acceptable.

Please address any questions that you or your staff may I

have concerning this matter to this office.

Very truly yours, k

l i

AnthonV D. Miosi Nuclear Licensing Administrator 1

ADM/ pay

{

1690K Enclosures cc:

NRC Resident Inspector - Braidwood

- Byron I

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l ATTACletENT BRAIDWOOD STATION UNISTRUT P1004A WALKDOWN CABLE TRAY HANGERS NUMBER OF HANGER MEMBERS CONTROL DISCREPANT TOTAL NUMBER UNIT 1 UNIT 2 INSPECTED 79k 7P3167 1

0 7P3351 2

0 16 8E7806*

O 35 53 8E7829*

1 10 22 8N7791*

1 1

40 8N7792*

1 0

30 8N7830*

2 0

9 Others 0

0 146 TOTAL 8

46 395

• Suspect Material 1690K J

o ATTACHMENT BYRON 2 UNISTRUT P1004A WALKDOWN-CABLE TRAY HANGERS NUMBER OF HANGER MEMBERS TOTAL CONTROL INSPECTED NUMBER DISCREPA E 47 7P3167 1

7P3351 3

48 i

8E7828*

5 15 8E7791*

3 41 8N7792*

1 44 Others 0

38 TOTAL 13 233 j

Suspect Material 1690K