ML20214A411

Forwards Response to 870306 Request for Addl Info on Proposed Tech Spec Changes Re Min River Level.Setdown Induced by 100-yr Recurrent Wind Velocity Should Not Be Considered in Determining Low River Level for Safe Shutdown

ML20214A411
Person / Time
Site:	Hatch
Issue date:	05/08/1987
From:	Gucwa L GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
SL-2245, TAC-62127, TAC-62128, NUDOCS 8705190443
Download: ML20214A411 (6)

Text

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, .. Geccgia Power Company 333 Piedmont Annue eph$na 526 6526 Of x 545 Atlanta, Georgia 30302 Georgia Power L. T. Gucwe tre southem entre system Manager Nuclear Safety and Licensing SL-2245 1259C X7GJ17-H600 May 8, 1987 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Hashington, D. C. 20555 PLANT HATCH - UNITS 1, 2 NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION -

RIVER LEVEL TECHNICAL SPECIFICATIONS Gentlemen:

By letter of September 9, 1986, Georgia Power Company (GPC) proposed certain changes to the Technical Specifications for Plant Hatch - Units 1 and 2 regarding minimum river level. Your letter of March 6, 1987, requested responses to eight specific questions. Questions #1-5 deal with a temporary weir, which could be constructed under authority of the Corps of Engineers, to artificially increase the river stage. Since your questions assume the existence of a weir, we would like to clarify that our proposed Technical Specifications changes are conservatively established such that they do not assume the presence of a weir. In all cases, river level at the intake structure with a weir would be equal to or greater than the river level would be without a weir. Accordingly, we request that you review and evaluate the proposed changes considering the existing situation.

Enclosure 1 provides GPC responses to your questions #6-8. As a fundamental consideration, like most Technical Specifications, we feel that regulatory requirements on minimum river level should be based on safety implications and not operational considerations. The current Technical Specifications on minimum river level are incorrectly based on requirements for normal plant operations instead of safety considerations.

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Georgia Powerd U. S. Nuclear Regulatory Comission May 8,.1987 Page Two The sumer season is traditionally a period of low river level in south Georgia. Accordingly, in order to avoid potential expedited submittals, we request your prompt review to resolve this issue.

If you have additional questions or concerns, please contact this office at any time.

Sincerely, f&-

L. T. Gucwa MJB/lc

Enclosure:

Response to Request for Additional Information - River Level Technical Specifications c: Georata Power Comp 3By Mr. J. P. O'Reilly Mr. J. T. Beckham, Jr.

GO-NORMS U. S. Nuclear Regulatory Comission. Washinaton Mr. L. P. Crocker, Licensing Project Manager - Hatch l

U. S. Nuclear Reaulatory Comission. Region II Dr. J. N. Grace, Regional Administrator Mr. P. Holmes-Ray, Senior Resident Inspector - Hatch 1259C toorts

Georgia Powerkn ENCLOSURE PLANT HATCH - UNITS 1, 2 WRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION -

RIVER LEVEL TECHNICAL SPECIFICATIONS

6. QUESTION:

Section 2.4.11.5 of the FSAR and the staff's SER for Hatch Unit 2 refer to the minimum operating elevation of the RHR service water pumps of 59.0 feet above mean seal [ sic] level datum (ft. msl.) with regard to minimum water requirements for the plant. Your letter of September 9,1986, refers to elevation 59.9 f t. ms1. with regard to minimum operating level for the Plant Service Hater (PSW) pump providing the required flow for safe shutdown. Is elevation 59.9 f t.

msl. the controlling water level consideration over the long term of the accident? If not, describe the most severe accident considerations considered in terms of water requirements and necessary river levels over at least a 30 day period.

RESPONSE

Elevation 59.9 ft. ms1. is the controlling water level consideration aver the long term of the hypothetical accident. The minimum submergence requirement for the RHR service water pumps for normal operation is less than the proposed safe shutdown requirement for the PSH pumps. The submergence requirements for the PSH pumps will be the controlling water level within the pump well. Therefore, the RHR service water pumps submergence requirements will be met.

7. QUES 11011:

The FSAR does not address events which could cause additional lowering of the river level such as wind induced setdown or clogging of the intake screens by debris. Calculate the setdown at the pump well resulting from a 100 year recurrent wind, critically oriented with regard to the intake structure, or provide a discussion which shows significant wind setdown to be highly unlikely based on fetch length, bathymetry, wind speeds, wind directions, etc. In addition, discuss the likelihood of debris blockage during low flow periods and the effects on pump well water level.

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Georgia Powerkh ENCLOSURE (Continued)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION -

RLVER LEVEL TECHNICAL SPECIFICATIONS

RESPONSE

A. Hind Induced Setdown During Low Flow:

During dry periods, the flow is contained in the main channel of the river. Therefore the critical orientation of wind with regard to the Hatch intake resulted in an effective fetch, Fe, of 0.22 miles. The 100-year recurrent extreme wind velocity, U, over water at the Hatch site is about 106 miles per hour

(" Journal of the Structural Division", ASCE 1968). The average river depth, D, at the intake for flow elevation 59.9 f t. ms1.

is about 4 ft. The wind setup (equal to setdown), S, of 0.9 ft.

was calculated by:

U2 X 2 Fe S- --------------

1400 X D However, occurrence of such setdown at the Hatch site is highly unlikely because of the following:

1. The recurrence interval of low flow level decreasing to E1.

59.9 is greater than 100-yr. (The lowest flow of record is 1430 cfs which corresponds to a river elevation of 61.8 ft.

msl. at the intake). The probability of a 100 year recurrent wind occurring at the time of such low flow is one in more than 10,000.

2. The 106 mile per hour extreme wind is for a short duration (i .e. , one minute). Therefore, the resulting setdown at the intake for such short time would have negilgible affect on pumping.

3. Extreme winds may result from four meteorological systems:

Extra tropical cyclones, tropical cyclones, thunderstorms, and tornadoes. These systems are usually accompanied by rain, which will result in increased river flow and raise the water level at the intake.

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Georgia Power b ENCLOSURE (Continued)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION -

RIVER LEVEL TECHNICAL SPECIFICATIONS The American Nuclear Society report ANS 2.8, recommends using a two-year recurrent extreme wind for wave and setup analyses during probable maximum flood. Using this approach, the wind at the Hatch site would be approximately 50 mph, with a duration of about 6 minutes with a fetch length of 0.22 miles. If the same criterion is used for lowering of intake level during low flows, a setdown of about 0.2 ft. will result.

In light of the above, the additional lowering of the river level due to wind induced setdown for a short duration will not have any adverse effect on pumping. Therefore, setdown induced by a 100-year recurrent wind velocity should not be considered in determining the low river level for safe shutdown of the Hatch Nuclear Plant.

B. Clogging of Intake by Debris During Low Flow:

The blockage of the Hatch intake by debris during drought periods is not likely. The debris in the river usually comes as a result of heavy rain or high river level.

8. QUISIl0H:

Under low flow conditions and the proposed Technical Specifications, do you intend to operate in a manner which will always preclude cavitation in the PSH pumps? Hill pump cavitation be allowed in order to carry out an orderly shutdown as opposed to an emergency shutdown in the event of a rapidly lowering water level? If so, what will be the effect on the pumps, and what steps will be taken to keep such effects to a minimum?

ESP _0 HSE:

The proposed Technical Specifications would preclude cavitation of the PSH pumps. Under the proposed safe shutdown limit, a flowrate of 1259C E-3 5/8/87 7 , ,, SL-2245

Georgia Power A l

ENCLOSURE (Continued)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION -

RIVER LEVEL TECHNICAL SPECIFICATIONS RESPONSE: (Con't) 4500 gpm from one PSH pump is required to achieve an orderly

, safe shutdown. This limit includes an additional margin to l

allow for continued river level depletion for 30 days. Under low flow conditions, the proposed Technical Specifications 4

requirements for the PSH system, a minimum of 2 pumps will be available for plant operation or shutdown. The 4500 gpm requirement for safe shutdown can be achieved with one pump t without detriment to the pump at the proposed safe shutdown limit. The proposed Technical Specifications are sufficiently conservative as to preclude the potential for cavitation during credible shutdown events.

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