ML19317F482

Forwards Hydrologic Engineering Questions on Facility & Suggests Informal Meeting W/Applicant to Discuss Requested Matl

ML19317F482
Person / Time
Site:	Oconee
Issue date:	03/23/1972
From:	Nunn D US ATOMIC ENERGY COMMISSION (AEC)
To:	Schwencer A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8001140713
Download: ML19317F482 (8)

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1 I;OIE FOR A. SCGECER, FROJEC2 IW;AGER, WR BRtdiOI 4, DRL W. GA!EIILL, GIIEF, SITE SAFETY EPAI;Cll, DRL T}IRU:

S ON OCOSEE IRJCLEAR STATION, UNITS

- !!YDROIDGIC ErGII;EERII;G QUESTIOI; 2 14 3, DOCKET 1:0S. 50-270, 287 Encioned are hydrologic engineering questions prepared by L.

They are on the subject plant for your trancmittal to the applicant.

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neccenitated by a review of both the IEAR and pSAR based on flood

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review plan where it was found that the caterini presented on potential and the dependability of the ultinate he the curnary based on present licensing practice a Powe Plante," (February, 1972).

However, vc note that by our concultant, the USG8, in 1967 and 1970.their r t

ply We note that dependability considered in precent licensing practice.

the cpplicant han recently completed responses to similar questi h

his McGuire plant and, therefore, chould be quite knowledgeab It in our understanding that these questions 2

are =cheduled to be furniched the applicant en April 19, 197 cpecific subject areas.

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We concider it desirable to have an informal meeting with the app informa-to discuce the requected caterial, and to obtai i

cnnlysin ci:mtitaneously with the applicant. It in poncible that the en-is cucgented to help capedite the review. closed questio t & nceting.

Finally, we note that any potential changes t

ie D. E. Puna Chief Earth Scientist Division of_ Reactor Licensing

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80011407(3

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Enclosure Ilydrologic Engineering Question:

ccw/encli R. DeYoung, DPL G. Arlotto, DR3 D. Lange, DRS Dictribution-

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)IYDROLOGIC ENGINEERING OUESTIONS

_0CONEE NUCLEAR _ STATION, ' UNITS 2 & 3 DOC. NOS. 50-270. 287 1.

To' fully substantiate the capability of the plant to sustain the mos t severe flooding reasonably possible at the site without a loss. of safety related function, twe distinctly different conditions should I

a be anclyzed in addition to those presented in the PSAR.

The two con-l ditions' are the occurrence of a probable maximum flood (PMF), and the

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_ possibility of a seismically induced flood caused by the failure of I

e upstream river control structures and/or landslides.

The following questions in this area should be answered in sufficient detail and include the basic information necessary to allow an independent hydro logic engineering review to be made in a manner directly analogous to similar questions and responses on your McGuire Nuclear Station:

The PSAR flood analysis has been compared with PMF estimates by a.

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the Corps of Engi::eers for other locations and for other nuclear power plant sites in the general region ><ad is substantiallyThi higher in peak discharge than the severe flood analyzed in the PSAR.

Two methods of estimating the w> te.h ade of the PMF may be used for the Oconee site because di

e letailed estimates by others in the area (only one anaf rica:

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technique would suffice at other locations where such estimates are not available) as follows :

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1) ; Using modi,fications of the probable maximum storm estimated for Hartwell Dam by the Hydrometeorological Branch of the Weather Bureau.(now NOAA) for the Corps of Engineers or.

generalized probable maximum precipitation values, verifi-able unit hydrographs, and routing characteristics, estimate i

the separate runoff hydrographs for the Jacassee Dam drainage I

and the intervening area between Jacassee Dam and Keowee Dam for (a) a local probable maximum storm critically centered above Jacassee Dam; (b) a local probable maximum storm critically centered above Keowee Dam; and (c) a local prob-able maximum storm critically centered above the intervening area between dams.

For each of these three cases, determine the most severe stillwater conditions at the plant site resulting from the separate reservoir regulation of each flood with an assumed antecedent flood about half as severe occurring 3-5 days previously.

The integrity of both darm should be analyzed to ascertain td. ether there is any possibility that they could fail during such severe events.

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If failure is considered possible, the resulting conserva-tively severe effects should be included in the estinates of the static and dynamic flood level considerations at the plant site.

The liartwell Dam probable maximum storm estimate is discussed in a memo from D. R. Harris, Ilydrometeorological Section of the Weather Bureau (now NOAA), to G. A. Hathaway, Corps-of Engineers, dated Jan. 5, 1951. Generalized probable maximum precipitation values are available from Ilydrometeoro-logical Report No. 33, " Seasonal Variation of the Probable Maximum Precipitation East of the 105th Meridian for Areas from 10 to 1,000 Square Miles and Durations of 6,12, 24 and 48 llours," Weather Bureau (now NOAA), April 1956, which may be reduced by 10-15 percent for basin shape.

In addition to the basic supporting documentation required for this analysis present a topographic map of the plant site area showing the i

finished grading and pertinent elevations to allow an indepen-dent review to be made of the potential for floods to flank the dam and flood the site.

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2) - Because of the number and proximity of detailed PMF estimate the upper limit of the worst conditions discussed above is i

considered to be a Jacassee inflow hydrograph with a peak dis-I charge of 170,000 'cfs and an intervening area Keowee inflow hydrograph of 130,000 cfs.

Hydrographs with these peaks may t..

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be readily approximated by. multiplying all ordinates of less severe historic.a1 or reliabic hypothetical hydrographs by the ratio of peak discharges. Provide the same analysis of plant flood potential. discussed in 1) daove.

b.

Substantiate that Jacassee Dam will be capable of sustaining a

' I local OBE and a coincident flood about half as severe as a PMF; or a local SSE with a full flood control reservoir and a coinci-i i

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dent downstream adverse hydrologic condition (such as a 25 year i

flood). Alternatively, demonstrate that there would be no loss of any plant safety related function as the result of a pos tu-lated severe failure of Jacassee Dam coincidentally with a flood -

dbout half as severe as a PMF.

Present your assumptions and pro-vide sufficient information to allow an independent review to be made of your analysis and conclusions,

Superimpose the effects of coincident wind wave activity on the c.

worst of the d)ove "stillwater" conditions.

The significant and '

maximum wave heights, resulting runup and resulting static and dynamic forces may be readily determined by using a 45 mph over-water wind speed from any critical direction, and the analysis techniques ' presented in U. S. Army Coastai Engineering Research l

I Center " Technical Report 'lho. 4, Shore Protection, Planning and I

Design," third edition.

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Provide the following analyses in sufficient depth to allow an independent review to be made of your assumptions and conclusions on the adequacy of your source of emergency cooling water.

I Provide an analysis of the hydraulic stability of the intake a.

channel weir during the rapid drawdown which would result from a postulated failure of either or both Keowee Lake dans and a con-i t

current low river flow condition. Describe the construction of

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grouted riprap cover, and how you intend to periodically inspect this underwater structure to assure its continued dependability and integrity during the life of the plant.

This analysis may refer to the material presented in Supplement 6 to the PSAR, but should include estimates of the maximum velocity on the downstream side of the weir based on the use of the concept of maxinum veloc-ity at normal depth with a roughness parameter realistically reficcting the coarse riprap you have used.

Discuss the ability of the riprap to withstand these maximum velocities.

A prelini-nary independent review of the hydraulic capability of this rip-rap indicates it may be insuf ficient to protect the weir embankment in the event of sudden drawdown.

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l Postulate a mecitanistic failure of either Ecowee Lake dan and b.

provide a detailed analysis of the duration of water supply available from the intake canal.

If recirculation is proposed, the analysis should include consideration of this postulated

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accident using severe evaporative meteorological conditions, and should include the bases for effective pond coolinC arca a

where circulation patterns could reduce the availabic surface If the available supply is less than 120 days, describe

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area.

k' the location, dependability, and use of any alternative sources.

State the minimum submergence requirements for all reservoir intake pumps.

Postulate a mechanistic failure of the intake canal dike fran c.

Discuss the methods to be employed and the unknown causes.

capability of other sources of water supply to shut down all three units and maintain than in a shutdown mode for 30 days; and for 120 days, Postulate a mechanistic failure of the side slopes of the intake d.

canal and discuss the methods to be employed to shut the three units down and maintain them in a shutdown mode for 30 days; and for 120 days.

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