ML19343D569
| ML19343D569 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/28/1981 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-04.F, TASK-2-4.F, TASK-RR A01452, A1452, NUDOCS 8105050329 | |
| Download: ML19343D569 (4) | |
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CONNECTICUT 06101 L <L : === ===
0dik April 28, 1981 W
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Docket No. 50-2h5 y
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A01452 9_
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g Director of Nuclear Reactor Regulation 9, h'
/J Attn:
Mr. Dennis M. Crutchfield, Chief s'
Operating Reactors Branch #5 4/6 i
'rf, W k U. S. Nuclear Regulatory Commission Washington, D.C. 20555
References:
(1)
D. G. Eisenhui letter to SEP Plant Licensees, dated January 14, 1981.
(2)
W. G. Counsil letter to D. G. Eisenhut, dated February 27, 1981.
Gentlemen:
Millstone Nuclear Power Station, Unit No. 1 SEP Topic ll 4.F, Settlement of Foundations and Buried Equipment As part of the redirection of the Systematic Evaluation Program, Reference (1),
Northeast Nuclear Energy Company (NNECO) committed to develop Safety Assessment Reports (SAR's) for certain SEP topics which would be submitted for Staff re-view. NNECO detailed this commitment and provided a schedule for submittal of SAR's in Reference (2).
In accordance with this commitment, NNECO hereby provides the Safety Assessment Report for SEP Topic 11-4.F, Settlement of Foundations and Buried Equipment, which is included as Attachment 1.
We trust the Staff will appropriately use this information to develop a Safety Evaluation Report for this SEP topic.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY W. G. Counsil Senior Vice President 810 505 032q
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r Docket No. 50-245 Safety Assessment Report SEP Topic 11-4.F, Settlement of Foundations and Buried Equipment April, 1981
b Millstone Nuclear Power Station. Unit No.1 SEP Safety Assessment Report Tbric 11-h.F'- Settlement of Foundations and Buried Equipment 1.0 Introduction This assessment reviews the protection of safety-related structures, systems, and components against excessive settlement.
2.0 Criteria Appendix A to 10CFR Part 100 states:
The geologic, seismic, and engineering characteristics of a site and its environs shall be. investigated in sufficient scope and detail to provide reasonable assurance that they are sufficient.y well understood to permit an adequate evaluation of the proposed site, and to provide sufficient information to support the determinations required by these criteria and to pernit adequate engineering solutions to actual or potential geologic and seismic effects at the proposed site.
3 0 Discussion The major structures and buried equipment are founded on bedrock, dense glacial basal till, or compacted backfill.
The rocks of the site are hard, crystalline, silicate rocks of stable mineral content and essentially no water content. The soils immediately above the bedrock consist of a dense basal till which was deposited and compacted by the ice. Above this is a somewhat stratified glacial deposit which is identified as ablation till.
The dense basal till is of low permeability. It consists of a mixture of cobble and boulder-size rock fragments, gravel-size material, sand, and some silt binder. It was overridden and compacted by ice during the glacial period and is a dense, strong, stable material, The ablation till is stratified irregularly with lenses of sand and gravel and mixtures of cobbles, gravel, sand, and silts. This deposit is slightly more
' permeable than the underlying basal till and is less dense. The basal l
till, which is denser than the ablation till, has a higher relative density and a well graded grain size distribution. The ablation tills, though less dense than the basal tills, are strong, stable materials.
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)' 3 Associated SEP Topics 114.D, Stability of Slopes 111-1, Classification of Structures, Components, and Systems 111-7.B Design Codes, Criteria, and Load Combinations h.0 Conclusions The total and differential settlements of the structures are expected to be negligible. The settlement of soil supported structures would have occurred during construction essentially at the same rate as the rate of loading.
Specifications of the backfill used for the foundations and buried equip-ment were not available during thic review. However, it is assumed that based on good engineering practice in conjunction with the underlying soils, excessive settlement has been precluded. Based on this review and the fact that no observable settlement problems have been noted to date, NNECO concludes that safety-related structures, systems, and com-ponents are adequately protected against excessive settlement.
5.0 References 1.
Standard Review Plan Section 2.5.h, Stability of Subsurface Materials and Foundations.