ML20137Z500

Interim Deficiency Rept 86-03 Re Defective Spot Welds on Cable Tray Hanger Strut Matl.Initially Reported on 860121. Unit 2 Containment Hangers Will Be Replaced & Unit 1 Hangers Will Be Repaired or Replaced

ML20137Z500
Person / Time
Site:	Braidwood
Issue date:	03/06/1986
From:	Miosi A COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
1387K, 86-03, 86-3, NUDOCS 8603130056
Download: ML20137Z500 (5)

Text

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^N Commonwealth Edison

) One First Nitional Plata Chicago. Ilknois V Address R ply to Post Othce Box 767 Chicago, liknois 60690 March 6, 1986 Mr. James G. Keppler Regional Administrator Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137

SUBJECT:

Braidwood Station Units 1 and 2 10 CFR50.55(e) No. 86-03 30-Day Interim Report Defective Spot Welds on Cable Tray Hangers NRC Docket Nos. 50-456 and 50-457

Dear Mr. Keppler:

On January 21, 1986, Commonwealth Edison Company notified Mr. R. Gardner of your office of a deficiency reportable pursuant to 10 CFR 50.55(e) regarding defective spot welds on cable tray hanger strut material at the Braidwood Station. An extension in submitting this response was discussed with W.S. Little of your office. This

letter provides information to fulfill the thirty-day reporting requirement and is considered an interim report.

DescriDtion of Deficiency During the installation of cable tray in Unit 2 containment, the Unit 2 electrical contractor G. K. Newberg l identifiad installed cable tray hangers which had discrepant spot l l welds. G. K. Newberg initiated NCR 331-00001 and NCR 331-00002 which together identified thirty (30) 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 P1000 single channels held together by side plates which are spot welded to the channel at 3" on center. Some of the spot welds on the cable tray hangers which join the side plates to the channel as identified by G. K. Newberg appear to be improperly fused. G. K. Newberg submitted the two NCR's to Commonwealth Edison Company for their evaluation.

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Upon review of the G. K. Newberg NCR's 331-00001 and 331-00002, CECO initiated NCR 793. In performing the 50.55e reportability review of NCR 793 Ceco determined that the identified problem was' reportable. In addition, CECO notified Unistrut Corporation 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 weld has not been fully. assessed. Scoping analysis to date for cable tray hangers with significant discrepant spot welds in heavily-loaded applications indicates that there is no safety significance. This preliminary conclusion will be verified as a result of the engineering evaluation.

Corrective Action Taken 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 rolled, the operator of the rolling machine and the steel coil I

number. Furthermore, Unistrut Q.C. documentation references the control number. The results of this walkdown are summarized in 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 welds. This information was passed along to Unistrut for their review. A review of the control numbers of the discrepant 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.

r Based on this records review Unistrut Corporation has established that 580 feet of rejected P1004A material was inadvertently shipped to 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') was received by SCC in August 1979. This material consisted of rejected 20 foot pieces of P1004A material that were accumulated for rework 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 SCC. Prior to the 1,000 foot shipment received in August of 1979, SCC had received P1004A shipments totaling 2,000 feet (1,500' - 1977, 500' - March 1979). 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 tne August 1979 shipment.

A comprehensive review of records by Unistrut indicates that the inadvertent shipment of 500 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 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 construction schedule considerations, it was determined to replace the Unit 2 Containment hangers which contained discrepant welds. The Unit I hangers will either be repaired or replaced. An engineering evaluation will be completed to assess the remaining hangers without discrepant wolds but fabricated of the suspect control numbers. An evaluation will also be done to assess the adequacy of adjacent intact spot welds.

It is apparent that. in addition to the 580' of suspect material, there exist occasional discrepant spot welds. Unistrut expects that occasional discrepant spots may not be detected by their Quality Assurance program. An engineering evaluation will be completed to assess this condition on a generic basis.

r In order to confirm our conclusion that this problem is isolated to cable tray hangers supplied by SCC, a walkdown was also completed for all installed conduit hangers in Units 1 & 2 which utilize Unistrut P1004A. There are 1275 conduit hangers utilizing P1004A of which discrepant welds were observed on only five hangers. Due to this low frequency of occurrence these discrepant wolds are considered isolated cases. These hangers will be repaired or replaced. Conduit and junction box haagers have been fabricated in a later time period as compared to cable tray 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.

In summary, results of the Unistrut P1004A demonstrate that:

1. The scope of the issue is 580 feet of discrepant material 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 cable tray hangers are primarily in Unit 2.

2. Occasional discrepant spot welds are expected by Unistrut for nonsuspect material. An engineering evaluation will be performed which should accept this condition on a generic basis.

3. An engineering evaluation will be performed for all cable tray hangers remaining with suspect control numbers. The control numbers shown in the attached table with an 8 prefix are considered suspect.

Please address any questions that you or your staff may have concerning this matter to this office.

Very truly yours

&cby DIIjw Anthony D. Mioni Nuclear Licensing Administrator ADM/ pay att.

cc: NRC Resident Inspector - Byron NRC Resident Inspector - Braidwood Director of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 1387K

e a g ATTAC10 LENT UNISTRUT P1004A WALEDOWN BRAIDWOOD 1 & 2 CABLE TRAY SUPPORTS CONTROL NUMBER HANGER MEMBERS _

NUMBERS DISCREPANT TOTAL INSPECTED UNIT 1 &

ColNION UNIT 2 7P3167 1 0 79 7P3351 2 0 16 8E7806 0 35 53 8N7830 2 0 9 8E7829 1 10 22 8N1791 1 1 40 8N1792 1 0 30 l

! OTHERS 0 0 146 TOTAL 8 46 395 l.

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