ML19276H473
| ML19276H473 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/11/1971 |
| From: | Hulman L US ATOMIC ENERGY COMMISSION (AEC) |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19276H472 | List: |
| References | |
| NUDOCS 7911130526 | |
| Download: ML19276H473 (2) | |
Text
JUN 11 1971 Files TliREE MILE ISLAND NUCLEAR POffER PLANT LEVEE INTEGRITY 1.
The applicant has summarized his design analysis for the levee and its rock riprap protection in the FSAR. De FSAR material and the basic computations have been reviewed and the followint conclusions are presented:
s.
De water surface provile computations performed by the applicant's consultant may be considered accurate within a tolerance of approximately + 1 foot; b.
De prediction of mean velocity for the portions of river along the leves is highly dependent on the computational assumptions made as to what the split in flow would be for the several island channels. Although the computations of water surface proviles should not be materially affected by substantial errors in essinates of flow in each channel, mean channel velocity deter-ainatiens could vary widely (perhaps 50 percent or more);
c.
We upstream bend and the islands in the Susquehanna itpose a nonuniform velocity distribution on flow past the icveed island which could substantially increase local velocities adjacent to the riprap; d.
De design of the levee riprap protection is based en average channel velocities and assumes uniform flow which is not affected by river bonds or islands; e.
The method of analysis used by the soplicant's consultant to design the riprap is generally satisfactory, but is highly dependent en assumptions made to estimate local flow velocities; f.
We accuracy of ficw velocity estimates cannot bo increased wi.thout recourse to a combination of very extensive data collection programs, hydraulic model and analysis studies; g.
Local flow velocities may be as such as Ino percent creater than mean channel velocities due to nenuniform flow conditions imposed by river bends and islands; h.
Riprap desigr. should not be 'Jased on velocities which can occur with the levee design flood, but rather should be sized for velocities associated with the PMF. We reason for this is that the protection against floods greater than the, levee design;
--flood-is-predicted--on--allowine-water--fren--these larger -floods--to---- -- - -
overtop the levee at its downstream end and back un{ to the plant'.
--Safetymisted-facilitiesjwould4e waterproofed--to prevent--the-- L -- --
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2-backed-up water from flooding the interior of the structures.
We levee is also required to protect the plant for floods which are between the levee design flood and those which will overtop the levee at its downstream end. Although the levee may be considered expendable with respect to the plant for large infrequent floods, no provision has been made for the possibility that erosion of the riprsp could trigger a levee failure and cause a flood wave to impinge on safety related structures.
- i. An analysis of local velocities associated with floods greater than the Icvee desimi flood, and perfor=ed in the same manner as those for the FS AR, would also discount the effects of non-uniform flow induced by bends and islands. We conclusions fron such an analysis would also tend to confirm that the riprap would be stable.
2 The applicant has designed the levee riprap protection trsing analysis techniques which are subject to question. I!owever, he has voluntarily stated that the riprap will be periodically inspected and any remedial action required will be taken inmediately. This action is considered satisfactory, provided the tech specs aid in assuring compliance, since it is anticipated that any rock design deficiencies will show up within several years of construction and probably before a flood occurs which could cause a levee failure.
L. G. Ifulman Special Projects Branch Divisica of Reactor Standards OFDCE >
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