ML19209C160

Discusses Plans for Optimizing Multipart Diffuser for 2-unit Operation & Dispersion Characteristics of Thermal Plume for Diffuser,In Response to 790622 Request

ML19209C160
Person / Time
Site:	Vogtle
Issue date:	09/26/1979
From:	Ehrensperger W GEORGIA POWER CO.
To:	Regan W Office of Nuclear Reactor Regulation
References
NUDOCS 7910120108
Download: ML19209C160 (4)

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W. I'. Ehrensp a rry>r September 26, 1979 Mr. William H. Regan, Jr.

Acting Assistant Director for Environmental Projects and Technology United States fluclear Regulatory Commission Division of Site Safety and Environmental Analysis Washington, D.C. 20555 f!RC DOCKET fiUMBERS 50-424 AND 50-425 C0tlSTRUCTI0tl PERMIT flUMBERS CPPR-108 AND CPPR-109 ALVIN W. V0GTLE fiUCLEAR PLAtlT-Ut1ITS 1 AtlD 2 MULTIPORT DIFFUSER

Dear Mr. Regan:

Your letter of June 22, 1979 requested that we advise you of our plans for optimizing the multiport diffuser for 2-unit operation. You also requested the dispersion characteristics of the thermal plume for that diffuser.

Our single multiport diffuser is being redesigned to optimize its per-formance for 2-unit operation. Construction drawings will be prepared following the completion of final design studies which include an in-vestigation of river sediment deposition and erosion in the vicinity of the diffuser.

Preliminary analysis of the redesigned diffuser indicates that the maxi-mum downstream extent of the05 F isotherm will be about 16 feet and the maximum predicted volume within the 50F isotherm will be approximately 1,500 cubic feet. This estimated 50F isotherm volume of 1,500 cubic feet is significantly less than the 2,400 cubic feet previously pre-dicted for the 4-unit project discharge flow and the original multiport diffuser design.

Pertinent information associated with the multiport diffuser optimization is presented in the following:

DESIGN RIVER CONDITIOilS Bottom elevation = 70' ms1 Surface elevation = 80' msl Hidth = 330' River flow = 5,800 cfs i143 115 Veloci ty = 1.7 fps Temperature =

41 F (winter) 7 910120 { b.kf i

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Mr. William H. Regan, Jr.

Nuclear Regulatory Commission Page 2 PRELIMINARY MULTIPORT DIFFUSER DESIGN The multiport diffuser will consist of either a 42 or 48-inch diameter manifold (determined by the hydraulic transient analysis being performed) with 25, 6-inch diameter nozzles spaced on 30-inch centers (Figure 1). The diffuser portion will begin about 40 feet from the river bank and extend 100 feet offshore (60-foot diffuser length). A nozzle orientation of 20 above the horizontal in the direction of the river flow was selected to minimize jet interference with the water surface and river bottom. Diffuser performance was evaluated for nozzle discharge velocities between 2.5 fps and 25 fps and a plant effluent temperature of 840F. The normal plant discharge for 2-unit operation, with no radwaste discharge, is 11,000 gpm which will result in nozzle velocities of about 5 fps. The plant operation for maximum effluent discharge is presently being re-evaluated; however, the maximum discharge will not result in nozzle velocities in excess of 25 fps nor an effluent temperature in excess of 840F.

ANALYTICAL APPROACH TO THE THERMAL PLUME COMPUTATION The submerged multiport diffuser system was designed to discharge the flow through a series of relatively small nozzles to achieve rapid mixing with the receiving water. In developing the diffuser configuration, the manifold diameter, nozzle spacing, and the nozzle diameter were selected to ensure reasonable uniformity of the discharge velocities from the nozzles and to provide the re-quired dilution performance. The jet velocity was evaluated to ensure that it was sufficiently high to provide complete mixing of the discharge flow with the river flow passing over the diffuser within a limited distance downstream of the diffuser. The characteristics of the 50 isotherm were obtained using the experi-mental results presented by Parr and Sayre (reference).

Please advise if you require additional information at this time. We are presently performing final design studies and will provide the design details in the FSAR/ER.

Sincerely,

'hb $U W. E. Ehrenspeyg ,er / l &

REFERENCE:

A. D. Parr and W. W. Sayre, " Prototype and Model Studies of the Diffuser-Pipe System for Discharging Condenser Cooling Water at the Quad-Ci ties Nuclear Power Station,"

Iowa Institute of Hydraulic Research Report No. 204.

June 1977.

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Enclosure Distribution Attached

Mr. William II. Regan, Jr.

fluclear Regulatory Conmission Page 3 cc: I . S. Mi tchell, III R. A. Thomas J. A. Bailey G. F. Trowbridge, Esquire T. E. Byerley B. L. Lex J . G. Fa rl ey , Jr.

D. E. Dutton L. T. Gucwa C. D. McCrary

!!i3 117

FIGURE 1 RE-DESIGNED MULTIPORT DIFFUSER 4 0*- O' 60*6

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'V* 8 I 3 DIFFUSER CROSS SECTION A-A[+3 }}h PROPOSED NOZZLE CONFIGURATION}}