ML20005A561
| ML20005A561 | |
| Person / Time | |
|---|---|
| Site: | Hartsville  |
| Issue date: | 06/02/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8106300455 | |
| Download: ML20005A561 (2) | |
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Mr. James P. O'Reilly, Director
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Office of Inspection and Enforcement ccmur.es U.S. Nuclear Regulatory Commission
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Atlanta, Georgia 30303
Dear Mr. O'Reilly:
HARTSVILLE NUCLEAR PLANT UNIT A1 - REPORTABLE DEFICIENCY - UNFUSED MATERIAL IN DRYWELL VENT STRUCTURE FRAME NO. 7 CLOSURE PLATE '4 ELD -
HTRD-50-518/81-10 The subject deficiency was initially reoorted to NRC-0IE, Region II, In'Jpector P. A. Taylor on March ?O, I'981, as NCR HUPA-136. The first interim report was submitted on April 27, 1981.
In compliance with paragraph 50.55(e) of 'O CFR Part 50, we are enclosint.( the final report on the subject ueficiency. If you have any questions, please call Jim Domer at FTS 857,2014 V<.ry truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure co:
Mr. Victor Stello, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Nashington, DC 20555 ht1
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-4 HARTSVILLE NUCLEAR PLANT A UNIT 1 UNFUSED MATERL IN DRYWELL VENT STRUCTURE FRAME NO. 7 CLOSURE PLATE WELD 10CFR50.55(e) REPORT NO. 2 (FINAL)
HTRD-50-518/81-10 Description of Deficiency On March 25, 1981, the Quality Control Welding Unit (QCW) was notified by the ironworkers that unfused material had been discovered in the inner closure plates for the Frame No. 7 in the unit A-1 Drywell Vent Structure. Investigar.on by QCW personnel identified a triangular piece of metal which appeared to be a " slug" in the end of two, six-inch inner closure plates. This was the deficiency as originally reported to OIE Region II.
However, further investigation into this matter has revealed that the unfused material was not caused by the vendor, Atlas Machine and Iron Works. The apparent unfused material was formed during thermal cutting by TVA to prepare base plate sections for welding. The unfused material was a plug between kerfs which had extended through the material intended to be cut and into the intersecting closure plates that were welded to the base plate.
Metallurgical analysis indicates that the vendor weld was partially severed by the thermal cutting operation. The presence of unfused material has been determined to be an attempt to conceal this error. A seal weld was applied over the accidental cuts to conceal the damage.
Safety Implications Presence of unfused material degrades the strength of the weld and reduces the safety margin for the Drywell Vent Structure frames. This condition might cause a structural failure during a design basis earthquake and, thereby, jeopardize plant safety had it remained uncorrected.
Corrective Action A patch plate will be fabricated from A-36 steel, welded by approved procedure, and radiographed as required. Because of the nature of the error which resulted in this condition, TVA believes this to be an isolated instance. Recurrence control will be the identification of those responsible for the attempted coverup. Disciplinary measures commensurate with the involvement will be taken. The repair and all disciplinary action will be complete by July 1, 1981.
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