ML19343C325
| ML19343C325 | |
| Person / Time | |
|---|---|
| Issue date: | 07/24/1978 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| IEB-78-11, NUDOCS 8103090481 | |
| Download: ML19343C325 (5) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE Oc INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 IE Bulletin No. 78-11 Date: July 24, 1978 Page 1 cf 3 EXAMINATION OF MARK I CONTAINMENT TORUS WELDS Description of Circumstances:
On June 28, 1978, Vermont Yankee Power Company (VYPC) reported that five non-penetrating surface crack indications and one nine-inch long surface crack were found in the overlay weld-to-torus base metal heat affected zones during the process of performing modifications (addition
-of strengthening gussets) to the torus support columns at the Vermont Yankee Nuclear Facility. These modifications were being performed as part of VYPC's overall program to restore the originally intended design safety margins for the Vermont Yankee Mark I containment system (re:
Mark I Containment Long Term Program).
Based upon initial indications of the depth, VYPC performed an analysis of the structural capability of the torus shells in the affected areas to support continued operation of the facility and proceeded to attempt to grind out the nine-inch crack. On June 30, 1978, the crack was still apparent after grinding to the calculated depth of 0.25 inches. The plant was placed in a cold shutdown condition on July 2, 1978. An evalu-ation is in progress.
The welding operations at Vermont Yankee were performed at locations on the torus shell which were lower than the water level in the torus.
Although the underlying causes of the cracking have not yet been deter-mined, the presence of water on the opposite side of the torus shell during the welding operations appears to have been a primary contributor.
Con-sequently, a generic concern has arisen that the potential for cracking j
could exist when welding is performed on a torus containing water.
In view of the above, on July 7, 1978, the.NRC Office of Inspection and Enforcement verbally requested licensees to perform close visual in-spections on similarly made torus weldments at Peach Bottom Unit Nos.
2 and 3, Quad Cities Unit Nos. 1 and 2, Hatch Unit No. 1, and Monticello facilities. These inspections revealed no apparent linear indications through the painted surface. However, Monticello reported that magnetic I
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i IE Bulletin No. 78-11 Date: July 24, 1978 Page 2 of 3 particle examination, together with visual inspection, revealed two relevant surface linear indications 1/2 inch long and 1-1/2 inches long, respectively, which were verified by liquid penetrant tests after removal of the paint.
Both indications were reportedly removed by grinding at less than 1/8 inch depth.
Action to be Taken by Licensee:
Licensees for Peach Bottom Unit Nos. 2 and 3, Quad Cities Unit Nos.
-1 and 2, Hatch Unit No. 1, and Monticello are further requested to pro-vide the following information:
Item A:
1.
Provide descriptions of the welding procedures, procedure qualifi-cations, welder qualifications, and electrode controls employed in strengtheni.1g the support column to torus connections (i.e.,
additien of gussets, saadle supports, webs, etc.).
2.
Provide a description of the preventive measures used to assure that condensation did nct occur on surfaces to be welded prior to and during the welding.
3.
Describe the chronology of nondestructive examinations performed subsequent to such welding operations.
Include procedures, methods, and techniques, the time period of NDE application after specific
. welds completed have been at ambient temperature, and the results of these examinations.
Item B:
Where the NDE documentation (Item A3) is not sufficiently definitive to show that welding ~to the torus was nondestructively examined after the completed welds were at ambient temperature for a minimum period of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the following measures should be taken:
1.
Remove paint from surfaces of the overlay weld and torus base metal heat affected zones (if not already done so) by rotary wire brushing or equivalent means.
I
IE Bulletin No. 78-11 Date: July 24, 1978 Page 3 of 3 2.
Examine the exposed interbead fusion zone of the overlay weld and the associated base metal heat affected zones utilizing magnetic particle techniques in accordance with the applicable section of the ASME Code.
3.
Any indications detected as a result of MT are to be evaluated as to their acceptability in accordance with the applicable ASME Code.
Examinations that detect relevant linear indications may be supple-mented by other nondestructive methods and techniques to determine the character of the flaws (i.e., estimated size, shape, depth, orientation,etc.).
4.
Results of the field examination of individual weldments are to be documented.
Within ten days of the date of issue of this Bulletin, report in writing to the Director of the appropriate NRC Regional Office, the information requested in Item A, and your proposed plan of action and schedule re-quested in Item B if the:72 hour minimum period described above was not met. A copy of your report as submitted to the Regional Office should be sent to the United States Nuclear Regulatory Commission, Office of Inspection and Enforcement, Division of Reactor Operations Inspection, Washington, D.C., 20555.
-Approved by GAO, B180225(R0072); clearance expires July 31, 1980.
Approval was given under a blanket clearance specifically for identi-
- fied generic problems.
I l
i e-
IE Bulletin No. 78-11 July 24, 1978 Page 1 of 2 LISTING OF BULLETINS ISSUED IN 1978 Bulletin Subject Date Issued Issued To No.
78-01 Flammable Contact -
1/16/78 All Power Reactor Arm Retainers in G.E.
Facilities with an CR120A Relays Operating License (0L) or Construction Permit (CP) 78-02 Terminal Block 1/30/78 All Power Reactor Qualification Facilities with an Operating License (0L) or Construction Permit (CP) 78-03 Potential Explosive 2/8/78 All BWR Power Gas Mixture Accumula-Reactor Facilities tions Associated with with an Operating BWR Offgas System License (0L) or Operations Construction Permit (CP) 78-04 Environmental Quali-2/21/78 All Power Peactor fication of Certain Facilities with an Stem Mounted Limit Operating License Switches Inside-(OL) or Construction Reactor Containment Permit (CP) 78-05 Malfunctioning of.
4/14/78 All Power Reactor Circuit Breaker Facilities with an Auxiliary Contact Operating License
. Mechanism-General (OL) or Construction Electric Model CR105X Permit (CP) 78 Defective Cutler-Hammer 5/31/78 All Power Reactor Type M Relays with Facilities with an DC Coils Operating License (0L) or Construction Permit (CP) t
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5 IE Bulletin No. 78-11 July 24, 1978 Page 2 of 2 LISTING OF BULLETINS (CONTINUED)
ISSUED IN 1978 Bulletin Subject Date Issued Issued To No.
78-07 Protection Afforded By 6/12/78 All Power Reactor Air-Line Respirators Facilities with and Supplied-Air Hoods an Operating License (0L),
all Class E and F research reactors with an operating license, all fuel cycle facilities with an operating license, and all Priority I material licensees 78-08 Radiation Levels from 6/12/78 All Power, Tes't, Fuel Element Transfer and Research Reactor Tubes Facilities with an Operating License (0L) having Fuel Element Transfer Tubes 78-09 BWR Drywell Leakage Paths 6/14/78 All BWR Power Reactor
-Associated with Inadequate Facilities with an Drywell Closures Operating License (OL)
(for Action), or.
Construction Permit (CP)(forinformation) 78-10 Bergen-Paterson Hydraulic 6/27/78 All Power Reactor Shock Suppressor Accumu-Facilities with an lator Spring coils Operating License (0L) or Construction Permit (CP) t
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