ML19309H071

Interim Deficiency Rept Re Broken Anchor Bolts in Reactor Vessel Support Skirt Flange.Cause Unstated.Teledyne Engineering Svcs Is Preparing Rept on Investigation of Failed Studs.Potential Solutions Include Replacing Studs

ML19309H071
Person / Time
Site:	Midland
Issue date:	04/11/1980
From:	Baily K, Boyak C, Curtis L CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML19309H068	List: ML19309H067 ML19309H071
References
NUDOCS 8005080304
Download: ML19309H071 (2)

Text

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Bechtel Associates Professional Corporation

SUBJECT:

HCAR 37 (Issued 12/28/79)

Broken Reactor Vessel Anchor Stud in Unit 1 INTERUI REPORT 2 DATE: April 11, 1980 PROJECT: Consumers Power Company Midland Plant Units 1 and 2 .

Bechtel Job 7220 Discrepancy The discrepancies discussed in this report are the failed reactor vessel anchor studs in Unit 1.

Background

The anchor studs in question are 2-1/2 inches in diameter and 7 feet 4 inches long, cabedded in the reinforced concrete reactor vessel pedestal. The anchor studs were purchased from lussissippi fabricated by Valley Structural Steel (MVSS) of St. Lou is , 111s souri ,

Southern Bolt and Fastener (SB&F) of Shreveport, Louisiana, and heat-treated by J.W. Rex of Lansdale, Pennsylvania. These studs were received on site by Bechtel in early 1976, embedded in concrete by Bechtel in April 1977, and tensionco by Babcock & Wilcox Construction Company in late July 1979. The failure of the first stud was discovered on September 14, 1979. Failures of the second and third studs were The reported on December 20, 1979, and February 5, 1980, respectively.

third stud was removed during the week of March 31, 1980 and showed that the failure occurred in the stud approximately 1/2 inch below the top of the bottom heavy hex nut.

Investigative Action Tcledync Engineering Services (TES) of Waltham, Ibssachusetts is preparing This report will a report based on its investigation of the failed studs.

provide acceptability for service criteria of the zeactor vessel anchor studs.

The quality verification document packrges for high strength, low alloy, quenched and tempered anchor bolts with a diameter greater than 1 inch used on the ludland project nre being reviewed.

An NRC investigative team has visited the ludland jobsite, the Ann Arbor office, and vendor locations. To date, the team's concerns have been focused on the history of the stud procurement, fabrication, testing, and quality documentation.

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Bechtel Associates Professional Corporation liCAR 37 Interium Report 2 April 11, 1980 Page 2 Preventive Action The detensioning of the anchor studs is presently underway. The Unit I studs will be entirely detensioned while the tension in the Unit 2 studs will be lowered to the intended value of 75 kai on the ef f ective tensile stress area of 4.0 square inches (a more detailed discussion was presented in Interim Report 1). The actual, tension in the studs will be determined by the lift-off force during detensioning.

Corrective Action Two options are being considered as potential solutions for Unit 1.

• These options are:

1) Shim the existing shield plug support brackets tight to the reactor vessel to provide additional support.

2) Replacement of the studs At present, these options are being reviewed and Bechtel met with Babcock &

Wilcox on April 9,1980, in Ann Arbor to discuss technical details regarding these potential solutions.

Safety Implications This deficiency, if uncorrected, could adversely affect the safety of the operations of the liidland plant at any time throughout the expected life of the plant.

Reportability This condition was reported by Consumee Power Company under 10 CFR 50.55(e) on September 14, 1979.

Submitted by: Ordf8afak

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Approved by:hof M f d J.J4. (u RTIJ

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Concurrence by: // M// ,

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