ML12297A246

Request for Additional Information

ML12297A246
Person / Time
Site:	Hatch
Issue date:	10/31/2012
From:	Martin R Plant Licensing Branch II
To:	Ajluni M Southern Nuclear Operating Co
Martin, Robert
References
TAC ME9004, TAC ME9005
Download: ML12297A246 (4)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 31,2012 Mr. M. J. Ajluni Nuclear Licensing Director Southern Nuclear Operating Company, Inc.

40 Inverness Center Parkway Post Office Box 1295. Bin - 038 Birmingham. AL 35201-1295

SUBJECT:

EDWIN I. HATCH NUCLEAR PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. ME9004 AND ME9005)

Dear Mr. Ajluni:

By letter dated July 5, 2012 (Agencywide Documents Access and Management System Accession No. ML12188A721), Southern Nuclear Operating Company, Inc., submitted a license amendment request to change the Technical Specification to revise the minimum water level in the plant service water pump well. The U.S. Nuclear Regulatory Commission staff finds that additional information in the hydrology area is needed as set forth in the Enclosure.

Please provide the additional information within thirty (30) days of the date of this letter.

Sincerely,

() ~fYl.~

f ~ert E. Martin, Senior Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366 cc w/encl: Distribution via Listserv

REqUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION EDWIN I. HATCH NUCLEAR PLANT. UNITS 1 AND 2 SOUTHERN NUCLEAR OPERATING COMPANY DOCKET NOS. 50-321 AND 50-366

1. As stated in the license amendment request (LAR), Edwin I. Hatch Nuclear Plant, Units 1 and 2 (HNP 1 and 2), uses a recession formula equation to compute the projected time (in days) for the plant service water (PSW) pump well level to reach 60.0 ft mean sea level (MSL), which is the minimum level required for post-Ioss-of-coolant accident cooling requirements as limited by the Standby Service Water Pump. This formula contains a recession constant represented by the letter "k" (also known as depletion factor) which represents the type of flow (surface runoff, interflow, or base flow) that dominates the area being studied. Furthermore, the LAR states that it uses a value of 0.995 (base flow in stream flow is dominant) for the recession constant when using the equation.

However, reference 3 of the LAR states that the overlapping ranges for the selection of "k" values represent the inherent difficulties in identifying a particular recession as being surface runoff, interflow, or base flow. Furthermore, Reference 3 also lists the range for baseflow as being between 0.93 - 0.995 and the LAR states that its baseflow "k" range goes from 0.995 - 0.997.

a) Please provide additional information on the general process, criteria and analysis that has been used by the licensee in order to determine the recession constant "k" value of 0.995 for the site, with special emphasis on how the aforementioned limitations of Reference 3 were resolved, if applicable. These limitations include, but are not limited to, establishing distinctions between interflow and baseflow, seasonally variable components of baseflow analyzed over a specified period of time, etc.

b) Please provide an explanation on what effect or consequences, if any, is presented by the licensee selecting a baseflow range (0.995 - 0.997) for uk" that is higher than that stated by the source reference listed in the LAR (0.93 - 0.995). The explanation should also have a special emphasis on the acceptability of the licensee selecting values higher than those stated in the reference paper (Reference 3 of the LAR).

Additionally, the LAR states that the recession formula has been used for a number of years. Therefore past precedence and/or references should be included as part of the response, if available.

c) Please clarify if the recession formula was used using the same uk" value (0.995) for each river level in the discharge rating table or if different "k" values, as permitted by the HNP 1 and 2 range (0.995 - 0.997), were used when determining the projected time to reach 60.0 ft MSL. If a range of values were used, additional information that Enclosure

-2 justifies this method and demonstrates added conservatisms should be included. In addition, past precedence and/or references should be included as part of the response, if available.

2. Reference 3 of the LAR states that any individual recession is a short-term event that varies from successive recessions based on several factors. Therefore, for longer period events, it is necessary to combine individual base flow recessions in order to provide an average characterization of base flow, called a master recession curve (MRC). Furthermore, it states that the MRC represents the most frequent depletion simulation since recession rates are influenced by antecedent recharge conditions.

a) Please provide a detailed explanation that clarifies the threshold of what constitutes a short-term event versus a long-term event in terms of having to calculate a single recession or a MCR curve. The response should emphasize why the option selected to characterize baseflow at HNP 1 and 2 is acceptable in comparison to the single versus average methods and demonstrate that the most frequent depletion simulation has been obtained based on the method selected and, therefore, used to determine the projected time to reach 60.0 ft MSL. In addition, past precedence and/or references should be included as part of the response, if available.

3. The LAR states that, based on Table 2 of the LAR and the use of the recession equation, the time (in days) for the water level to drop to 60.0 ft MSL would be 66 days.

However, it is not clear from Table 2 how this value was obtained.

a) Please provide a summary of the calculations performed in order to obtain the value of 66 days from Table 2 of the LAR.

b) Please provide a graphical representation, similar to the example of Figure 3 provided in the LAR, which visually shows the "River Level versus Time" plot using the obtained results from the recession equation and discharge table. This figure should clearly demonstrate the availability of water for 66 days before reaching river level 60.0 ft MSL, as required by the limiting Standby Service Water Pump.

October 31, 2012 Mr. M. J. Ajluni Nuclear Licensing Director Southern Nuclear Operating Company, Inc.

40 Inverness Center Parkway Post Office Box 1295, Bin - 038 Birmingham, AL 35201-1295

SUBJECT:

EDWIN I. HATCH NUCLEAR PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. ME9004 AND ME9005)

Dear Mr. Ajluni:

By letter dated July 5,2012 (Agencywide Documents Access and Management System Accession No. ML12188A721), Southern Nuclear Operating Company, Inc., submitted a license amendment request to change the Technical Specification to revise the minimum water level in the plant service water pump well. The U.S. Nuclear Regulatory Commission staff finds that additional information in the hydrology area is needed as set forth in the Enclosure.

Please provide the additional information within thirty (30) days of the date of this letter.

Sincerely, IRA!

Robert E. Martin, Senior Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366 cc w/encl: Distribution via Listserv DISTRIBUTION PUBLIC RidsNrrDorlLpl2-1 Resource RidsAcrsAcnw MailCTR Resource RidsNrrDorlDpr Resource RidsRgn2MailCenter Resource RidsNrrLASFigueroa Resource RidsOgcRp Resource G. Purciarello, NRR G. Casto, NRR RidsNrrPMHatch Resource LPL2-1R/F

. N0.: ML12297A246 ADAMS A ccesslon *Bsyemal'1 dated ** V'la Emal'I OFFICE DORULPL2-1/PM DORULPL2-1/LA ** DLR/RERBIIBC* DORULPL2-1/BC DORULPL2-1/PM NAME RMartin SFigueroa MMurphy RPascarelii RMartin DATE 10/24112 10/24/12 10/22112 10/26/12 10/31/12 OFFICIAL RECORD COPY