ML19347B050
| ML19347B050 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/30/1980 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML19347B048 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, AEC-MP3-213, NUDOCS 8010010423 | |
| Download: ML19347B050 (3) | |
Text
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July 30, 1980 Docket No. 50-423 AEC-MP3-213 B10044 Mr. B. H. Grier, Director United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Gentlemen:
Millstone Unit No. 3 Reporting of Deficiencies in Design and Construction This letter provides final reporting as committed by NNECO in its 3 Q' yf
)(g) previous letter of Jent-3,1980, on the structural problems encountered in the Service, Auxiliary, and Turbine Buildings at Millstone Unit h
No. 3.
As previously reported, the Service Building was reportable under 10CFR50.55(e)(1)(ii).and has been corrected.
Further analysis has shown that the Turbine Building problem is not safety related, and therefore not : eportable.
The review of the Auxiliary Building structural analysis has concluded that it is reportable under 10CFR50.55(e)(1)(ii).
The remainder of this report will deal with the details of the Auxiliary Building problem and corrective changes instituted by Stone & Webster Engineering Corporation.
The review of the Auxiliary Building design determined that horizontal seismic loads were distributed to shear walls according to their relative stiffness at each ficor.
However, the analysis was incomplete in that the moments and vertical forces at each level of the building resulting from horizontal seismic forces were not carried down through the structure in a consistent manner.
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. To resolve the proLlem, an independent seismic review of the Auxiliary Building was~ performed.
A response spectrum modal analysis using a three-dimensional lumped mass model was employed.
Three orthogonal directions of excitation were used (two horizontal and one vertical),
with vertical excitation taken as two-thirds of the horizonal excita-tion. The seismic responses were used in conjunction with the detailed structural model to determine the seismic stress resultants in the structural walls in the building.
The primary structural elements of the building were reviewed on this basis, and it was determined that certain modifications are required to resist seismic loads.
These modifications include increasing the reinforcing in certain walls and slabs, installing rock anchors on the building perimeter and providing additional interior columns and walls.
The structural changes required in the Service Building and Auxiliary Building are a result of the incompleteness of the calculational methods and models employed originally.
These methods and models were selected by the individual who performed the building calculations and were independently checked by a similarly qualified individual not previously involved with the work.
In this situation, the preparers and checkers who were associated with the Millstone 3 project, produced a consistent project calculational method, but did not detect the incomplete aspect of the method.
In order to preclude the recurrence of the use of a similar inappropriate analytical method, Stone & Webster has reinforced its Structural Technical Review Program. This corporate program, under the direction of an Assistant Chief Structural Engineer includes a review and approval of all design criteria to be used in the design of structures as well as the analytical approach and methods to be used.
The program also includes the scheduling of a series of reviews during the design process to assure proper application of the criteria and methods and to determine the acceptability of the final design.
This program is staffed with senior engineers and consultants with extensive experience in the areas of dynamic analysis, design, and engineering of various types of structures.
In addition to the scheduled involvement of these individuals, they are available to the project groups whenever their particular expertise might be required.
The implementation of this program will assure a proper and uniform design.
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We trust that this report addresses any remaining concerns you may have on this sutject.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY l
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W. G. Couns11 Senior Vice President i
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cc:
Nuclear Regulatory Commission Office of Inspection & Enforcement Division of Reactor Operations Inspection
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Whshington, D.C.
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