ML19338D320

Final Deficiency Rept Re Structural Problems in Auxiliary, Turbine & Svc Bldgs.Auxiliary & Svc Bldg Problems Caused by Incomplete Calculations & Models Originally Used.Stone & Webster Technical Review Program Modified

ML19338D320
Person / Time
Site:	Millstone
Issue date:	07/30/1980
From:	Counsil W NORTHEAST UTILITIES
To:
Shared Package
ML19338D319	List: ML19338D320
References
10CFR-050.55E, 10CFR-50.55E, AEC-MP3-213, B10044, NUDOCS 8009220330
Download: ML19338D320 (3)

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July 30, 1 %0 Occket No. 50-423 AEC-MP3-213 B10044 Mr. B. H. Grier, Directer United States Nuclear Regulatory Ccmission Recion I ~

63i Park Avenue King of Prussia, Pennsylvania 19406 Gentlemen:

Millstone Unit No. 3 Reporting of Deficiencies in Desian and Ccnstruction This letter provides final reporting as ccmicted by NNECO in its 3 Q7,,,.f )(p previous letter of 4e#3,1980, on tb structural probhms enccuntered in the Service, Auxiliary, and Turbine Buildings at Millstone Unit hp No. 3.

As previcusly reported, the Service Building was reportable under 10CFR50.55(e)(1)(ii).and has been corrected.

Further analysis has shcwn that the Turbine Building problem is nct safety related, and therefore not reportable.

The review of the Auxiliary Building structural analysis has ccncluded 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 hori: ental seismic loads were distributed to shear walls according to their relative stiffness at each floor. However, the analysis was incomplete in that the mcments and vertical forces at each level o.' the building resulting from horizontal seismic forces were not carried down through the structure in a consistent manner.

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. s 2-To resolve the problem, 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 artnogonal 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 detennined that j 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 inccmpleteness of the calculational methods i 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 corristent 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 methcd, 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 i' 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 i

experience in the areas of dynamic analysis, design, and engineering of I 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 subject.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY W. G. Counsil Senior Vice President cc: Nuclear Regulatory Ccmission Office of Inspection & Enforcement Division of Reactor Operations Inspection Whshington, D.C. 20555 9

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