ML20003B128

Final Deficiency Rept Re Cracks in Electrical Hanger Hardware Supplied by Midland-Ross/Superstrut Co,Originally Reported 800625 & in Subsequent 800728,1022,1126 Submittals. Revised Shop Methods Initiated by Vendor

ML20003B128
Person / Time
Site:	Clinton
Issue date:	01/30/1981
From:	Koch L ILLINOIS POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, 1605, Q37-81(01-30)-L, U-0213, NUDOCS 8102100387
Download: ML20003B128 (3)

Text

, T.TC 1605 U-0213 ILLINDIS POWER COMPANY Q37'81(01'30)"L

• 500 SOUTH 27TH STREET, DECATUR, ILLINOIS 62525 January 30, 1981 D

Mr. James G. Keppler /\ "~

Director, Region III pq s s Office of Inspectica and Enforcement U.S. Nuclear Regulatory Commission A 'hD W J ' ,g 799 Roosevelt Road C FE8 0 91981 w , -

Glen Ellyn, IL 60137 g;l v. , g ,

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Dear Mr. Keppler:

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Clinton Power Station Unit Docket No. 50-461 qy' Construction Permit No. CPPR-137 On June 25, 1980, Illinois Power Company verbally notified Mr. H.

M. Wescott, U.S. NRC Region III, of a potential reportable deficiency per 10CFR50.55(e) regarding suspect cracking in certain electrical hanger hardware supplied by Midland-Ross/Superstrut. Interim reports were submitted July 28, 1980; October 22, 1980; and November 26, 1980. This letter is intended to serve as the final report on cracked fittings, but it will be treated as an interim report on the total subject of electrical hanger hardware to permit the evalua-tion of any potential impact of revised vendor load criteria which resulted from tests of the cracked fittings.

Investigation of Suspect Hardware on Electrical Hangers

1. Statement of Reportable Deficiency Several styles of framing fittings for commercial strut electrical hanger assemblies--those fittings which are formed by bending on perpendicular axes--were discovered to have cracks at the bends.

Additionally, some were found to have been weld repetred in the factory. The reliability of such fittings under design-based conditions was suspect.

In the process of testing the suspect fittings in typical connection assemblies and replicate hanger assemblies, the supplier found some discrepancies in the holding capabilities of certain fitting fasteners. As a result, Midland-Ross Corporation has revised some bolt loading cr~ eria. These revised design loads may impact the design hangers for the Clinton Power Station.

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', 1605 U-0213 Q37-81(01-30)-L Mr. James G. Keppler January 30, 1981 Page 2

2. Investigation Results The investigation of the . racked fittings entailed tensile tests and on-site visual inspection of all stock hardware, followed by testing of typical connection assemblies and replicate hanger assemblies to more conclusively determine load bearing and transfer characteristics of the fittings.

Fittings in stock at the-Clinton site were visually inspected and all cracked and weld-repaired fittings were removed from stock.

Tests were performed using cracked fittings removed from the site and similar fittings from the supplier's stock. Original testing was performed to determine the loading values of individual fittings. These tests were followed by load tests on typical connection assemblies and replicate hanger assemblies of Clinton Power Station electrical hangers, again using cracked fittings, for loading values and load transfer characteristics.

The Architect-Engineer (Sargent & Lundy), Constructor (Baldwin Associates), and Owner (Illinois Power) monitored these tests.

No fittings caused the deflection or failure of replicate hanger assemblies.

Test results were used by Midland-Ross Corporation as the basis for revised design loads per bolt. Midland-Ross has transmitted new data to Sargent & Lundy, which include'these new design loads.

Sargent & Lundy will reevaluate the electrical hanger design co deternine any impact of the change.

3. Corrective Action As related in the pre"ious interim reports, revised shop produc-tion methods have beci initiated by the Midland-Ross/Superstrut Company to eliminate cracking and to ensure that no fittings with cracks, or weld repairs, vill be shipped in the future to Clinton Power Station.

The testing program demonstrated that cracked fittings within the supplier-established acceptance criteria are adequate for use.

Although Illinois Power has accepted these criteria, we have determined that for Clinton Power Station in the present stage of construction more effective control can be exercised by replacing the fittings in Category I installations which show evidence of significant cracking orLwhich have been repaired by

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1605 U-0213 Q37-81(01-30)-L Mr. Jamec G. Keppler January 30, 1981 Page 3

3. Corrective Action (continued) welding. In the event that it is determined that any cracked fittings should be retained in Category I installations, they will be required to conform to the approved acceptance criteria. 4 1

4. Safety Implication / Significance During testing of replicate hanger assemblies, the cracked fittings did not cause any failures or deflection of the assemblies.

Though many tested fittings were cracked in excess of the accept-ance criteria now established, the " worst case" in plant instal-lations could not be assured.

Similarly, since weld repairs to fittings were not controlled, their limitations are indeterminate. Therefore, it is possible that a fitting failure could have occurred during a design basis event. An estimate of the effects of such a failure would be purely speculative; however, in the worst case, they might have been significant.

We expect to submit a final report which will include our evaluation of any impact of the revised design loads by April 15, 1981. I trust that this letter'provides sufficient information for your final review and analysis of the cracked fitting problem.

! Sincerely, L J . 1;och Vice President dl-cc: H. H. Livermore, USNRC Resident Inspector Director, Office'of I&E, USNRC, Washington, D.C. 20013 Director-Quality Assurance

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