ML19259A742

Forwards Interim Rept Re Deficiency in Tendons Used to pre-stress Primary Containment.Final Rept Will Be Submitted by 790415

ML19259A742
Person / Time
Site:	Byron
Issue date:	01/05/1979
From:	Naughton W COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 7901100251
Download: ML19259A742 (4)

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% Commonwealth Edison s 't% s One First National Plaza. Chicago, lilinois .

,/ '. Address Rep y to: Post Office Box 767

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Chicago, Illinois.60690 ,

1 January 5, 1979 Mr. J. G. Keppler, Director Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Comission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Subject:

Byron Station Unita 1 and 2 Post-Tensioning System NRC Docket Nos. 50-454 and 50-455

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Dear Mr. Keppler Corznonwealth Edison notified your office on November 28, 1978 of a deficiency in the tendons used to pre-stress the concrete (primary) containment on Byron Units 1 and 2. That I notification was made under 10 CFR 50.55 (e) . On December 20, i

1978 Mr. J. conklin of your office reviewed the status of the evaluation of this deficiency and, upon the request of I comonwealth Edison, agreed to c3ttend the 30-day written report i

requiremont under 10 CFR 50.55(e) to allow for the submittal of

that written report on January 5, 1979. The attached interim report fulfills the 30-day reporting requirement under the j Regulation. As is indicated in the attachment, the final report i shall be suhaitted by April 15, 1979 at which time the evaluation i

initiated to determine that action, if any, necessary to resolvc this deficiency will have been completed.

Please address any questions you may have to this i office.

f Very truly yours,

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,/7 [Jgo//

c/ M W. F. Naughton'yL

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Nuclear Licensing Administrator Pressurized Water Reactors attachment cca C. Reed Comuonwealth Edison Company Director of Inspection & Enforcement U.S. Nuclear Regulatory Comnission 9\

7904100 m \

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Commonwealth Edison NRC Docket Nos. 50-454

50-455 3

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ATTACINENT

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BYRON STATION UNITS 1 AND 2 INTERIM REPORT CONTAINMENT TENDON DEFICIENCY INRYCO, Inc. submitted Nonconformance Report No. 781-9, dated November 30, 1978, for Byron Unita 1 and 2. This nonconfonnance concerned a field inspection of the tendons shipped to the Byron site which do not meet the INRYCO Button Head Acceptance Criteria 1610.

The tendons which are the subject of this nonconformance report are those used to post-tension the containment Buildings for Byron Units 1 and 2. The post-tensioning system selected for Byron Units 1 and 2 is a 170 wire BBRV system supplied by INRYCO, Inc. The post-tensioning system for each containment Building is comprised of 120 individual dome tendons, 162 individual vertical tendons, and 201 individual horizontal tendons. Each tendon is comprised of 170, 0.250 inch diameter wire conforming to the chemical and physical properties o. ASTM A-421, Grade BA steel, having a minimum ultimate tensile strength of 240,000 psi. Metal sheathing is embedded in the Containment Building concrete to serve as a condcit for the installa-tion of the tendons. A steel anchor head is provided at each end of the tendon to serve as a termination and anchor point for the tendon wires. Each tendon wire end is upset, forming a button head to seat the individual wires on the anchor head. One end of each wire is button headed in the shop, while the other end is button headed in the field after the tendon has been installed in the metal sheathing. The tendons are hydraulically tensioned after the installation of the field applied button heads to approximately 70%

of its ultimate strength.

Field Inspection INRYCO made field inspections on November 16, 1978 and November 17, 1978 on the excessible button heads of 46 tendons using a feeler gauge and found 13 rejectable tendons based upon the crack criteria in INRYCO Specification 1610. The rejections were based upon the existence of splits oriented between 30 and 45 , and greater than 0.002" wide; and the sum total of all splits or the opening in excess of 0.060" of one (1) split oriented at less than 300

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Commonwealth Edison NRC Docket Hos. 50-454

.. 50-455

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t Discussion Imperfections in both shop and field applied button heads are to be expected. The acceptable imperfections, such as splits and slips, are defined in the INRYCO Button Head Acceptance Criteria 1610. The INRYCO, Inc. OA/QC procedure recuires that the shop applied button heads be inspected in accordance with their Button Head Acceptance Criteria 1610, prior to th shipment of the tendons to the job site. This inspection consists of a 100% visual inspection for cracks, and a minimum 10% examination for button head size with a go-no-go gauge. Shop applied button heads which fail to meet the Button Head Acceptance Criteria 1610 are to be rejected by IURYCO and cither repaired cr rcplaccd prior to shipment to the jobsito.

The INRYCO Nonconformance Report 781-9 has notified Commonwealth Edison Company t' int shop applied button heads were shipped to the Byron jcb site which do not meet the INRYCO Button Head Acceptance Criteria 1610. The primary concern of Commonwealth Edison Company is the failure of the INRYCO, Inc. QLrlity Assuranco procedures to prevent this occurrence.

INRYCO, Inc. has contended that the existing Button Head Acceptance Criteria 1610 is conservative and has stated that, in their opinion, flaws of the type and number observed in the Byron button heads do not impair the structural capacity of the tendons to serve their intended function. In this regard, IURYCO, Inc. has proposed to conduct a test program to substantiate that a more liberal acceptance criteria will not jeoperdize the adequacy of the tendons delivered to the Byron job site. The results of this test program and modifica button head acceptance criteria will be made available to Commonwealth Edison Company by INRYCO, Inc. on January 31, 1979. In the interim, INRYCO, Inc. will conduct field inspections of the shop applied button heads at the Byron site using the current acceptance criteria in order to quantify the nature and extent of the button head defects. This list will be compared to the revised button head acceptance criteria, and those button heads which fail to meet the revised button head acceptance criteria will be rejected.

Commonwealth Edison Company will also conduct an audit of the INRYCO Quality Assurance program to assess INRYCO, Inc.'s deficiencies.

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".., Commonwcaltn aison NRC Docket Nos. 50-454

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50-455

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This test progr am is expected co be concluded and the results evaluated by Commonwealth Edison in the first quarter of 1979. A final report to complete the reporting requirements of 10 CFR 50.55 (e) will be submitted to Region III by April 15, 1979.

The vendor nonconformance report that documents the deficiencies observed on Byron Station Units 1 and 2 is on file at the plant site for review (Inland Ryerson Report NC/CA No. 781-9 dated 11/30/78). A complete report on the wire test program results and wire inspection results shall be submitted by April 15, 1979 as a part of the final report.