ML19220B723
| ML19220B723 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/07/1975 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Moore V Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7904270253 | |
| Download: ML19220B723 (2) | |
Text
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'275 V'. A. Moore, Assistant Director for Light Water Reactors, Group 2, RL Q-2'S !.ND POSITION C'I FOUNDATIONS FLANT NAME: Three Mile Island LICENSING STACZ: OL DOCIET NO. STN--50-320 RES?ONSI3LE BRANCH:
L'4R 2-2; 3. Washburn, LPM 2Equ m sa COMPLETION DATE: April 25,1975 APPLICLVIS RESPONS2 DATE NECESSARY FOR L'EIT ACTION PLAL'ED: As soon as practical DESCRIPTION OF RESPONSI: Answer questions RZ7IIJ STATUS: Site Analysis Branch - Avaiting Response Enclosed are our final Q-2 questions on foundation engineering for the subject plant. These questions were prepared by L. Hel.ler.
Our primary cor.cern is ths stability of the dika sections adj acent to the Category I river intake structures. These slopes are unusually steep and their failure might cause a blockage of the water intake
- area, Dtt;1nal S: ped h H. R. Osat:m Harold R. Denton, Assistant Director for Site Safety Division of Technical Reviev Office of Nuclear Reactor Regulation
Enclosure:
DISTRI3UTION:
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THRIE MII.E ISLAND - UNIT 2 DOC ~v~.T 50. 50-320 Q-2 's ON FOUNDATIONS 3Y L. HILLER, SA3 13-43/2.5.5 13-44/2.5.5 13-45/2.5.5 Dike Stability Amendrent 25, Page 51-129 indicates that embank =ent dry density values of 113 psf were used for stability calculations, and that strength assu=ptions were 1000 psf cohesion and 30 degrees friction angle.
Shelby tube sa=ples (Figure 32.3-7 and 32.3-6) taken from this e=barJc=ent indicate dry densities of 105.7 psf and 111.2 psf, which are less than 113 psf. The two unconfined com-pression tests (Figure 32.3-6) do not cocfirm the assu=ed strengths used for fill under draw down and earthquake con-dicions because the fill vould be saturated for these conditions and cohesion values would be reduced.
ne ICES slope stability analyses indicates factors of safety, in some cases, which are higher than those obtained by a si=ple vedge =ethod of m,1ysis.
This indicates that uncon-servative safety factors were obtained for these slopes by using the ICES results.
3:ent:0 th: ::.==d fill d---itice end ctren;;the he.v 20: b ::
substantiated by investigation, test, 1nd the analytical results are questionable, the staff concludes that the stability of the dike slope is undetermined.
(RSP) The staff has-concluded that further efforts toward an analytical de=onstration of the stability of the dike slopes in the vicinity of the intake structures, by additional assessments of fill densities and soil tests =ay not be practical, and that an alternative reans of assuring the safety of these slopes is ncv appropriate.
It is our position that the applicant should assess the hazards associated 'ith a dike slope failure that would flatten the 1 vertical to 2 horizontal slope to an af ter failure slope of 1 vertical to 3.5 hori: ental. He should de=onstrate that the water intake structure vill continue to fulfill its function under the slope change and that the supply of water to the plant will not be endangered.
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