ML19290C103

Final Deficiency Rept Re Overstress Condition of Lowest of Three Cooler Supports.Caused by Design of Letdown Cooler Platform & Supports.Util Studying Feasibility of Utilizing Equipment & Structures in Design & Const of Coal Units

ML19290C103
Person / Time
Site:	North Anna
Issue date:	01/04/1980
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
004, NUDOCS 8001090446
Download: ML19290C103 (3)

Text

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Vepco .. _ . _ ,... _ _ . _ . .. _ _ . . _ . .....

January 4, 1980 Mr. James P. O'Reilly, Director Se.ial No. 004 Office of Inspection & Enforcement PSE&C/WBR:mac: wang U. S. Nuclear Regulatory Commission Region II Docket Nos. 50-404 101 Marietta Street, Suite 3100 50-405 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

On January 2,1980, a report was made under the provisions of 10CFR50.55(e) concerning the Letdown Cooler Supports for North Anna Units 3 & 4.

In accordance with the reporting requirements of 10CFR21, the following information is submitted:

A. Name and address of reporting individual:

Mr. E. A. Baum, Executive Manager Licensing and Quality Assurance Virginia Electric and Power Company P. O. Box 26666 Richmond, Virginia 23261 B. Facility, activity and/or component affected:

North Anna Power Station, Units 3&4 Letdown Cooler Supprts C. Name of firm constructing the facility or supplying the component, activity or service:

Babcock & Wilcox Company P. O. Box 1260 Lynchburg, Virginia 24505 D. Description of defect, deficiency, or failure to comply:

It was determined that the combination of the Letdown Cooler's support platform and supports would result in an overstressed condition in the lowest of the three cooler supports. The basic problem can be nost easily explained by the simplified sketch of the lower cooler support and support brackets shown on the attached figure. The axial load is restrained entirely by the lower support since the two upper supports are sliding supports to allow for thermal expansion. Because the lower support bracket extends just beyond the bolt hole in the direction of the vessel,, the cooler's lower support becomes a cantilever beam required to sustain a very large moment. The axial load produces a moment in the neighborhood of 160,000 in.-lbs. and a bending stress in the support in excess of 100 KSI.

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E. Date of determination of reportability:

January 2, 1980 F. Similar components, activities, or services:

None G. Corrective action which has been, is being or will be taken, the individual responsible and the length of time to complete the action:

As stated previously in other correspondence to the NRC, Vepco has undertaken a study of the feasibility of utilizing the existing North Anna 3 & 4 equipment and structures in the design and construction of coal units. In the event that we decide to continue with the construction of North Anna Units 3 and 4 as nuclear units, we will modify the current support design to eliminate the overstressed condition.

H. Other information:

Since no other actions will be required to correct the problem described in section D of this report, we consider this to be the final report under the provisions of 10CFR50.55(e).

Should you require further information, lease contact this office.

r truly 6u ,

( 'S Senio'r Vic President - Power ation Attachment Engin ering and Construct 4on

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