ML20024D427

Forwards Request for Addl Info Re Util 830701 Discussion of Potential Mudflow from Hypothetical Spirit Lake Blockage. Response Requested within 60 Days of Receipt of Ltr

ML20024D427
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	07/25/1983
From:	Clark R Office of Nuclear Reactor Regulation
To:	Withers B PORTLAND GENERAL ELECTRIC CO.
References
TAC-49636, NUDOCS 8308050015
Download: ML20024D427 (4)

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NRC PDR RBallard L PDR RCodell Docket No. 50-344 JUL 2 51983 NSIC WJohnston ORB #3 Rdg RVollmer DEisenhut GClainas Mr. Bart D. Withers OELD Vice President Nuclear EJordan Portland General Electric Company JTaylor ACRS-10 121 S. W. Salmon Street Portland, Oregon 97204 Gray File RAClark-PMKreutzer-3

Dear Mr. Withers:

CTrammeli In conducting our review o'f your_. letter, of July 1,1983_ relating to Spirit Lake, we have determined that we will need the additional infomation identified in th' _ e'nclosure to' continue our review.

e In order for us to maintal' hur review schedule, your response is n

requested within 30 days of your receipt of this'le.tter..

Following receipt of your 're3ponse, we request that a meeting be held in Bethesda with you,an_d your. consultant to discuss this matter in more detail. Weplantoalsohaveourconsultan't(USGS). attend.

For planning purposes, the, meeting should be held about two weeks after we receive your response.

Please contact.your NRC Project Manager who can make detaile~d arrangements..

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; themfore, OMB clearance is not required under P.L.,96-511.

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Please contact us if you h'av'e any questions concerning this request.

Sincerely, Original slaned by Robert A. Clark Robert A. Clark, Chief Operating Reactors Branch f3 Division of Licensing

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Enclosure:

Request for Additional Information cc w/ enclosure:

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Portland G:neral Electric Company Michael Malmros, Resident Inspector

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U. S. Nuclear Regulatory Commission Trojan Nuclear Plant P. O. Box 0 Rainier, Oregon 97048 Robert M. Hunt, Chairman Board of County Commissioners Columbia County St. Helens, Oregon 97501 Donald W. Godard, Supervisor Siting and Regulation Oregon Department of Energy Labor and Industries Building Room 111 Salem, Oregon 97310 Regional Administrator Nuclear Regulatory Commission, Region V Office of Executive Director for Operations 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 i

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HYDROLOGIC ENGINEERING SECTION

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Additional Questions " Potential Mudflow 1

from a Hypothetical Failure of: Spirit Lake Blockage" (July 1,1983 response from PGE)

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1.

The report appears to be a summary of a more detailed analysis and report.

F As such, however, it does not contain the information necessary to enable us to evaluate it.

If you have a more complete report please provide'it.

I 2.'

The important case of a mu'dflow during a low Columbia: River flowrate,

-with consequent high sedimentation in the Columbia River, followed by -

a large flowrate has been neglected.- Records have shown that high flow-rates (1,000,000 CFS) have followed periods of low flow by only a few days.

Analyse the potential-for flooding of the site by'this scenario, or justify why this case was not considered..

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'3.

Item 1.3 The procedure used to reduce the sediment concentrations from 39, 52, 'and 65 percent to 20, 30, and 45 percent respectively, as summarized in Table 1 should be discussed and all assumptions should be justified.

3 For example, what is the basis for reducing the volume of material into j

the Cowlitz by 40% (column 2)? What is the basis for the ratio of sand to finer material of 2 to 1-(columns 3 and 4)? Etc.

4.

Item-1.4 Please explain the basis' for the 30 percent moisture assumption.

p Is this figure based on available pore volume or on total volume of. dry-

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solid? What porosity was used and what is its basis?

5.

Item.1.6 What is the basis for assuming a Columbia River sediment

concentration of 500 ppm? What effect would varying'this concentration l

have onLyour results?

6.

Several references are used in the. text, but are not documented. For example, the "Colby method" in item 2.4.

Provide the references.

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7.

Item 2.5 Define the tenn " bulking factor",

8.

Item 2.6 Give basis for your assumption that the shape of the mudflow sedi-ment deposit at the confluence of the Cowlitz and Columbia rivers can be ratfoed from the configuration of the deposition following the May 18, 1980 t-mudflow.

That mudflow deposition was rather flat compared to other known mudflow slopes.

What is the sensitivity of your results to variations in y:

the slope of deposited sediments?

9.-

Item 3.4 Give basis for calculations of sediment load. Were formulas employed derived from relationships for sediment transport in rivers?

If so, justify that these formulas are acceptable for the very-high sediment loads of the present case.

10. Item 3.8 Why is 400,000 CFS the "most reasonable Columbia River flow i_

to evaluate"? Is there a probabilistic basis for this conclusion?

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_,,. 11. Table 1 (a) Column 8 is unclear. Arithmetically, it appears that the expression should be (col 6 + col 4)/1.4. Explain the meaning of the value 1.4, and why it is used here.

l (b) - Explain the difference between column 1 and 2.-

Also, why is " material"'

used in column 1 and " sand, silt and clay" used in column 2?

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