ML19347F508
| ML19347F508 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 05/11/1981 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8105190480 | |
| Download: ML19347F508 (3) | |
Text
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',a Commonwealth Edison One First National Pfaza. Chicago, ll?noy Address Reply to: Post Office Box is7 l
CNcago. Illinois 60690 May 11, 1981
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Mr. James G. Keppler, Director 9
Directorate of Inspection and L,l t.
Enforcement - Region III C'.
A M ol U.S. Nuclear Regulatory Commission T-;
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799 Roosevelt Road
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Glen Ellyn, IL 60?37
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Subject:
Braidwood Station Units 1 and 2 Containment Post-Tensioning Breakdown of Vendor QA/QC Program NRC Docket Nos. 50-456 and-50-457 l
Dear Mr. Keppler:
In accordance with 10 CFR 50.55(e), Commonwealth Edison Company notified your office on April 9, 1981 of an incident that-occurred at Braidwood Station whereby a shop anclorhaad bushing slipped out of the jacking adapter during tendon stressing, stripping threads on the bushing.
The failure occurred on March 19, l
1981, but was not considered to be a reportable item at that time.
However, the ensuing investingation revealed that the bushing did not dimensionally conform to the Vendor's (INRYCO, Inc.)
specification.
Further investigation indicated the possibility that other non-conforming anchorheads could have been shipped to Braidwood, Byron and other sites utilizing the Vendor's equipmment.
Commonwealth Edison Company deemed this to be a breakdown of INRYCO's QA/QC Program and hence a reportable incident.
The attached interim report fulfills the 30-day reporting requirement under the Regulation.
As is indicated in the Attachment, the Final Report shall be submitted by July 31, 1981, at which time the evaluation initiated to determine that action, if any, necessary to resolve this deficiency will have been completed.
Please address any questions you may have to this office.
Very truly yours, M
T. R. Tramm l
Nuclear Licensing Administrator Pressurized Water Reactors Attachment cc:
Director of Inspection & Enforcement 30/
Washing.on, DC 20555 3,
1/I 3081B h
810519'0 %.-
i NRC Docket Nos. 50-456 50-457 ATTACHMENT Interim Report Non-Conforming Anchorheads For the Post-Tensioning System Braidwood Station. Unit 1 During the stressing operation of dome tendon 02-20 in Braidwood Unit 1 Containment Building on March 19, 1981, a thread failure occurred between the shop anchorhead bushing RR327 and the stressing adapter.
The stressing jack pressure gaugs: reading was 4300 psig when the failure occurred.
Lock-off pressure for this tendon is 4350 psig which represents approximately 70% of the guaranteed ultimate tensile strength of the tendon.
This incident was reported by Commonwealth Edison Company Nonconformance Report No. 285.
Further stressing operations were immediately halted until resolution of the bushing / adapter failure.
The anchorhead which is the subject of this nonconformance is part of the post tensioning system for the Containment Buildings.
This post tensioning system is a 170 wire BBRV system supplied by INRYCO, Iac.
It is comprised of 120 dome tendons, 162 i
vertical tendons and 201 horizontal tendons for each Containment Building.
Each tendon consists of one hundrea seventy 0.25 inch diameter wires conforming to ASTM A-421, Grade BA steel.
A steel anchorhead is provided at'each end of the tendon to serve as tarmination and anchor point for the tendon.
1 Commonwealth Edison Company requested INRYC0 to provide an
)
explanation for the cause of failure with appropriate analytical justification.. Field measurements of the f ailed bushing indicated undersize, and thus material was in nonconformance with the INRYC0 oesign specifications.
INRYC0 was requested to measure and replace all nonconforming shop anchorhead beshings for the remainder of the i
dome tendons to be stressed.
l INRYC0 commenced anchorhead measurements and had difficulty finding anchorheads cnnforming to their design specifications.
l Subsequently, INRYC0 reported that they learned from their anchorhead manfacturer that ACME #4 stub threads are machined to industry tolerances for the major and pitch diameters without i
meeting the tolerances on the minor diameter.
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2 INRYC0 is currently in the process of finalizing thcir analysis to justify the minor diameter for all' threaded surfaces of anchorheads.
Based upon the results of this analysis an inspection procedure will be developed to ensure conforming ancherheads are provided for all future work.
Furthermore, ther_ results will be utilized for the disposition of the in-place. stressed anchorheads.
Commonwealth EJison Company expects that final resolution will be completco by July 31, 1981.
At that time, a final report will be submitted documenting required. corrective action and corrective action to prevent future recurrence.
30818
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