ML20090J222

Forwards Comments on Bechtel Responses to Confirmed Items C-101 & C-117-2,3 Re Comparison of Auxiliary Bldg Finite Element & Seismic Stick Models.Comments Define Addl Info Needs

ML20090J222
Person / Time
Site:	Midland
Issue date:	05/16/1984
From:	Levin H TERA CORP.
To:	Lauren Gibson CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
References
NUDOCS 8405220385
Download: ML20090J222 (4)

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FHe t-W Mr. Louis Gibson Manager, Engineering Midland Project Consumers Power Company 1945 West Parnall Road Jackson, MI 49201

Subject:

TERA Comments on Bechtel Response to Confirmed items C-101, C-117-2,3

Dear Lou:

TERA has reviewed Bechtel's April 23,1984 letter (No. 148825) which contains the response to Confirmed items C-101 and C-117-2,3. Our comments, which define our additional information needs, are attached.

Should you require any clarification of our discussion, please contact Mr. Joseph Martore at our Bethesda office. Information pertaining to the disposition of this item may either be discussed at our next review meeting in mid-June or via correspondence.

Sinc rely, p%

Howard A. Levin Project Manager Midland IDCVP Attachment ec: - J. Cook, CPC J. Keppler, NRC, Reg lil D. Eisenhut, NRC, NRR R. Erhardt, CPC D. Budzik, CPC D. Quamme, CPC (site)

R. Whitaker, CPC (site)

D. Hood, NRC, NRR -

J. Taylor, NRC, I&E T. Ankrum, NRC, l&E J. Milhoan, NRC, l&E E. Poser, Bechtel R. Burg, Bechtel J. Agar, B&W J. Korr, S&W (site)

IDCVP Service List

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t SERVICE LIST FOR MIDLAlO INDEPEtOENT DESIGN AlO CONSTRUCTION VERIFICATION PROGRAM cc:

Harold R. Denton, Director Ms. Barbara Stomiris Office cf Nuclear Reactor Regulation 5795 N. River U.S. Nuenor Regulatory Commissim Freeland, Michigan 4'B623 Washingtoa, D.C. 20555 Mr. Wendell Marshall James G. Keppler, Regional Administrator Route 10 U.S. Nuclear Regulatory Commission, Midland, Michigan 48440 Reg, ion ill 799 Roosevelt Road Mr. Steve Godler Glen Ellyn, Illinois 60137 2120 Corter Avenue U.S. Nuclear Regulatory Commission Resident inspectors Office Ms. Billie Pirner Garde d* Michi on 48640 for Accountable Government I

9 Government Accountability Project Mr. J. W. Cook Institute for Policy Studies Vice President 1901 Que Street, N.W.

Consumers Power Company Washington, D.C. 20009 1945 West Parnall Road Jackson, Michigan 49201 Charles Bechhoefer, Esq.

Atomic Sofety & Licensing Board Michael I. Miller, Esq.

U.S. Nuclear Regulatory Commission Isham, Lincoln & Beale Washington, D.C. 20555 Three First National Plaza, Chic o, 11 is 60602 p,

S 6l25 N. Verde Trail James E. Brunner, Esq.

Boca Roton, Florido 33433 Consumers Power Company 212 West Michigan Avenue Jerry Harbour, Esq.

Jackson, Michigan 49201 Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission f7 W shingion, D.C. 20555

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set M ve Midland, Michigan 48640 Mr. Ron Collen Michigan Public Service Commission Cherry & Flynn 6545 Mercontile Way Suite 3700 P.O. Box 30221 Three First National Plaz Lansing, Michigon 48909 Chicago, Illinois 60602 Mr. Paul Rou Ms. Lynne Bernobei Midland Daily News Government Accountability Project 124 Mcdonald Street 1901 G Street, NW Midland, Michigan 48640 Washington, D.C. 20009 9

r TERA CommdNTS ON BECHTEL RESPONSES TO OCR ITEMS (C-101, C-117-2,3) i 1.

C-101 i

Comparison of the auxiliary building finite element and seismic stick models represents good practice and serves os a verification tool during the design / analysis process. While comparison is also useful as a verification tool within the IDVP, the need for comparison is somewhat different.

Accordingly, IDVP reviewers have not raised the issue simply on the basis of good practice or that a more rigorous comparison may have enhanced the project's design verification effort. IDVP reviewers have focused on this comparison to gain insight into the significance of noted items documented in a series of civil / structural and civil / soils Confirmed items.

The response indicated that several parameters had been compared to verify consistency between the stick model and the finite element model.

With respect to verifying the consistency of building stiffnesses representation, a significant parameter to be evaluated is building I

fundamental mode shapes or dispiccement. To assure that the two models accurately and consistently represent the building response, the relative difference in building displacements for similar loading should be small.

However, displacement comparisons provided in the Bechtel response do not at this time support this conclusion. The reasons presented to explain the differences require clarification and additional detail. For example, the fundamental differences in the two models (e.g., crocked vs. uncracked properties, differences in soil springs, location of compared displacements, amount of slab rotation, etc.) should be specified and evaluated, in terms of the impact they may have on the response inconsistencies.

i 2.

C-1 I 7-2,3 While the Bechtel response adequately describes the physical pheonomenon and existence of stress redistribution, it does not describe how thIs physical behavior is accounted for in the methodology used to perform the redistribution for overstressed elements. Nor does the response provide any clarification of the guidance or procedures given to engineers which would describe when and where stress redistribution may be used and to i

what extent. It is not clear how the limits on the amount of acceptable stress redistribution are specified.

We believe that such procedures should be founded on accepted methods or on special sensitivity studies.

Furthermore, the extent of the i

redistribution should be considered to ossess its potential impact on the behavior of the model.

i in addition, the initial response indicated that "for a limited number of structural elements where the tensile and shear stresses exceeded the values of 44 f'c and 3 4 f'c, respectively, concrete elements were assumed to crack, resulting in reduction in stiffness and redistribution of l

forces in localyzed areas." It is unclear whether or not a reduction in stiffness is applied in g cases where element concrete stresses exceed these threshold values.

If this stiffness reduction is not consistently applied, the basis for selective element stiffness reduction should be specified. - This would also imply that should additional concrete element overstress exist offer the initial stiffness reduction, a subsequent stiffness reduction / stress redistribution is appropriate. Therefore, the number of redistribution iterations should be ~specified, along with the number of '

overstressed elements resulting from each run.

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