Text

Response to Request for Additional Information Regarding Request for a License Amendment to Technical Specification 3.7.9, Ultimate Heat Sink.
	ML15364A369
Person / Time
Site:	Braidwood
Issue date:	12/16/2015
From:	Kaegi G; Exelon Generation Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	RS-15-329
	Download: ML15364A369 (38)
	v • d • e

~4300

~Warrenvifle, Winfield Road Exeton Generation 3 5 IL 60555 00Ofc RS-l15-329 10 CFR 50.90 December 16, 2015 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. N.PF-72 and NPF-77 NRC Docket Nos. 50-456 and 50-457

Subject:

Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, "Ultimate Heat Sink"

References:

1) Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,"'"

dated August 19, 2014 (ML14231A902)

2) Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, "Ultimate Heat Sink," dated April 30, 2015 (ML15120A396)

3) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC)

Additional RAI Regarding Containment Analysis for Braidwood UHS LAR (MF4671 and MF4672), dated July 22, 2015

4) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC)

Need Clarification Conference Call Regarding Your April 30, 2015 Response to SCVB-RAI-I(a), dated August 12, 2015 (ML15224B548)

5) Emnail from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC)

Additional RAIs Regarding Braidwood Ultimate Heat Sink Temperature Amendment, dated September 29, 2015

6) Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,"'" dated October 9, 2015

7) Letter D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information ThcI-

December 16, 2015 U.S. Nuclear Regulatory Commission Page 2

7) Letter D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,"'" dated October 30, 2015

8) Letter D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,"'" dated November 9, 2015

9) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC)

Preliminary Balance of Plant RAIs for Braidwood Ultimate Heat Sink LAR, dated October 26, 2015 In Reference 1, Exelon Generation Company, LLC, (EGC) requested an amendment to the Technical Specifications (TS) of Facility Operating License Nos. NPF-72 and NPF-77 for Braidwood Station, Units 1 and 2. The proposed amendment would modify TS 3.7.9, "Ultimate Heat Sink (UHS)," by changing the maximum allowable temperature of the UHS from 100 0 F to a maximum UHS temperature of 102°F. The U. S. Nuclear Regulatory Commission (NRC) requested additional information related to its review of Reference 1 and additional information was provided in Reference 2.

Subsequent to submittal of Reference 2, the NRC requested additional information to support the review of the subject License Amendment Request (i.e., Reference 1) in References 3, 4 and 5. In response to the requested information, Exelon responded in References 6, 7 and 8.

Just prior to submittal of Reference 8, the NRC provided an additional request for information from the Balance of Plant reviewers in Reference 9. The Reference 9 questions were discussed with the NRC in a teleconference on November 16, 2015, and it was agreed that a response to the questions would be provided by December 16, 2015. The requested information is contained in Attachment 1 to this submittal.

EGC has reviewed the information supporting a finding of no significant hazards consideration that was previously provided to the NRC in Attachment 1 of Reference 1. The information provided in this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b), a copy of this letter and its attachment is being provided to the designated State of Illinois official.

Should you have any questions concerning this letter, please contact Ms. Jessica Krejcie at (630) 657-2816.

December 16, 2015 U.S. Nuclear Regulatory Commission Page 3 I declare under penalty of perjury that the foregoing is true and correct. Executed on the 16th day of December 2015.

Respectfully, Glen T. Kaegi Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC : Response to Request for Additional Information : Braidwood Station UHS Lake Aerial Photograph : UFSAR figures 2.4-47 and 2.4-48 : Supporting Data Files Provided on Compact Disc cc: NRC Regional Administrator, Region Ill NRC Senior Resident Inspector, Braidwood Station Illinois Emergency Management Agency - Division of Nuclear Safety

Attachment 1 Response to Request for Additional Information

Attachment 1 Response to Request for Additional Information In Reference 1, Exelon Generation Company, LLC, (EGC) requested an amendment to the Technical Specifications (TS) of Facility Operating License Nos. NPF-72 and NPF-77 for Braidwood Station, Units I and 2. The proposed amendment would modify TS 3.7.9, "Ultimate Heat Sink (UHS)," by changing the maximum allowable temperature of the UHS from 100 0F to a maximum UHS temperature of 102°F. The. U. S. Nuclear Regulatory Commission (NRC) requested additional information related to its review of Reference I and additional information was provided in Reference 2.

Subsequent to submittal of Reference 2, the NRC requested additional information to support the review of the subject License Amendment Request (i.e., Reference 1) in References 3, 4 and 5. In response to the requested information, Exelon responded in References 6, 7 and 8.

Just prior to submittal of Reference 8, the NRC provided an additional request for information from the Balance of Plant reviewers in Reference 9. The Reference 9 questions were discussed with the NRC in a teleconference on November 16, 2015, and it was agreed that a response to the questions would be provided by December 16, 2015. The requested information is below.

SBPB RAI-I- Atmospheric heat transfer relationships in licensee model Backgiround The licensee states in Section 6.3 of ATD-109 "The initial natural temperature for each case is taken to be the natural temperature of the lake at the time step of the start date of the weather file. The natural lake temperature at these time steps is found in the results of the

'Worst_Weather_110' case from the file 'Worst_Weather_1 10.pltX'. These natural lake temperatures will be used to set the initial natural lake temperature in the worst weather LAKET-PC runs made in the main body of this calculation."

It also states, "The natural lake temperature refers to the temperature of the lake if it is reacting to purely natural influences. The initial natural lake temperature is the initial temperature of the lake that is not in the participating part of the UHS."

Issue The initial lake temperature for all the runs as shown in the figures of attachment E is the proposed TS limit of I102°F. Section 6.3 states the natural lake temperature is used to set the initial natural lake temperature in the worst weather LAKET-PC runs made in the main body of this calculation.

The use of natural lake temperature, initial lake temperature at the start of a DBA and the proposed TS limits are not clearly explained in the application.

ReQ ulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that The UHS has the capability to dissipate the maximum possible total heat load by conducting independent check calculations. An understanding of the LAR's analysis is required.

Page 1 of 28

Attachment 1 Response to Request for Additional Information Request Explain how natural lake temperature is used in LAKET-PC and how it relates to initial lake temperature at the start of the DBA and the proposed TS limit of 1020 F.

Explain why the natural lake temperature, which is stated to be the temperature of the lake reacting to purely natural influences, is a function of the number of pumps running as stated in Table 6-7?

Clarify how the natural temperature is used in the UHS analysis and how natural lake temperature is used in the heat transfer equations for the LAKET-PC?

Exelon Response to SBPB RAI-I:

The initial lake temperature for each analysis case is set equal to 102 0 F, which is independent of the natural lake temperature. A lake reacting to purely natural influences (i.e., no heat rejection from the plant) is at the natural lake temperature, which is a function of the weather and lake profile. The natural lake temperature at time zero is a required input in the LAKET-PC input file. The LAKET-PC runs in Attachment A of ATD-01 09 (ATD-01 09 is included as of Reference 1, herein referred to as ATD-01 09) evaluate the response of the Braidwood UHS to the entire range of weather data (July 1948 - Dec 2012), and thus contain natural lake temperatures for each time step. This calculated natural temperature for the time and date at the start of the worst weather file is used as the initial natural lake temperature for each analysis case run.

The natural lake temperature is independent of the number of SX pumps in operation.

Table 6-7 in Attachment A of ATD-01 09 presents the natural lake temperature at each accident start time for each operating scenario (i.e., 2, 3, or 4 SX pumps). The natural lake temperatures vary for each start time and operating scenario not because of the number of pumps .in operation, but because the start date for the worst weather file (and thus, the date and time from which the initial natural lake temperature is taken) varies with the number of pumps in operation (since the flow rate determines the transit time). This can be seen in Tables 6-3 through 6-5 in Attachment A of ATD-01 09 which show that the start date for the worst weather file can vary with the number of pumps in operation. The initial natural lake temperature used in the input file for each analysis case is the natural lake temperature at the date and time of the first entry in the worst weather file (as documented in Attachment A of ATD-01 09).

LAKET-PC utilizes the natural lake temperature to determine the natural evaporation rate from the entire lake. Additionally, for the effective portion of the lake, a forced evaporation rate is calculated as the increase above the natural evaporation caused by the influence of the plant.

The total evaporation rate is the sum of the natural and forced evaporation terms.

The evaporation from the water surface is calculated per the following equation:

Page 2 of 28

Attachment 1 Response to Request for Additional Information E = d F(w) ( e* - ea)

Where:

E = mass flux (mass/area/time) d = water density w = wind speed F(w) = a wind speed function, includes free and forced convection effects es = saturated vapor pressure at water surface temperature ea = vapor pressure of water vapor in the atmosphere When calculating the natural evaporation using the equation above, the wind speed function is the Lake Hefner model, the water surface temperature is taken to be the natural lake temperature, and consequentially, the saturated vapor pressure at the water surface is taken at the natural lake temperature.

SBPB RAI Hydraulic model(s) for Braidwood UHS pond

Background

The analysis of UHS thermal performance presented in the LAR portrays the pond as a series of equal-sized segments with water flowing through at a fixed rate, with no mixing laterally, longitudinally or vertically. The licensee calculated the effective area and volume of the UHS pond on the basis of an empirical method that was developed for cooling ponds in general (MAD 83-0239 (Reference 5.1), "Effective Area of Cooling Lakes," MESI11.1, Sargent and Lundy Rev IA, 11/3/2014). The effective area and volume of the pond is taken as a large fraction (82.3%) of the actual volume and area to account for non-idealized flow and transport of hot water.

Issue NRC staff needs to determine whether the licensee's plug flow analysis results in a conservative evaluation of peak return temperature, in light of the evidence from review of the LaSalle UHS pond that the hydraulics of the pond may not be well represented by a one-dimensional plug flow with each plug corresponding to 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months of pump flow. Evidence of the complex circulation caused by jet discharge can be found in the CFD analysis done by the licensee for the LaSalle UHS pond. The licensee responded to NRC's Request for Additional Information (RAI) number 5 (Gullot, 2015) with a detailed description of their methodology for estimating effective area and volume. This approach may or may not be conservative and this cannot be determined without further analysis and attention to details of the actual Braidwood UHS pond. For example, based on information in the licensee's application, discharged water would enter the pond through submerged pipes at speeds up to 8.51 ft/sec, depending on the number of SX pumps in operation. Based on an audit conducted at the Braidwood site in July 2015, the NRC staff believes that the water is discharged straight up and above the lake level. The drawings and LAR do not clearly describe how the discharge enters the pond. This discharge could lead to a Page 3 of 28

Attachment 1 Response to Request for Additional Information high rate of vertical and horizontal mixing, and the inducement of significant circulation throughout the pond. Furthermore, irrespective of mixing caused by the jets, the discharged water would result in a wide distribution of travel times between the discharge and intake, caused by the spread of the discharged water to conform to the rectangular shape of the pond rather than a single travel time as portrayed in the plug-flow model. The licensee's analysis recognizes the spread and the distribution of travel times, but their method for determining the effective area and volume may not adequately account for the type of discharge. It also assumes that the velocity profile of flow through the pond varies linearly between zero and twice the average velocity in the center.

Recqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that The UHS has the capability to dissipate the maximum possible total heat load by conducting independent check calculations. An understanding of the LAR's analysis is required.

Request Provide any evidence, based on actual measurements of circulation in the UHS pond, model studies, or analogs, on the actual pond hydraulics. Alternatively, perform sensitivity studies with your performance model over a range of effective volumes and surface areas that encompass and exceed the current estimate of 83.2% efficiency. Present your reasoning for why the LAKET-PC model is an accurate or conservative model for the purpose of calculating peak return temperature Exelon Response to SBPB RAI-2:

Actual measurements, model studies, or analogs for the actual pond hydraulics are not available. A sensitivity study utilizing higher and lower pond effectiveness inputs has been run in LAKET-PC to determine the impact on the calculated peak temperature at the plant intake.

A significant parameter in the peak temperature calculation is the transit time, which is rounded to the nearest 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months increment in the LAKET-PC runs in ATD-0109 (ATD-0109 is included as of Reference 1, herein referred to as ATD-01 09). The transit time is calculated as the effective volume of the pond divided by the flow rate. In order to demonstrate the impact of a change in transit time, an effectiveness value drastic enough to change the transit time (when rounded to the nearest 3-hour increment) is chosen for the sensitivity cases. As a result, varying the effectiveness changes the transit time, which is also a parameter in defining the worst weather file. Thus, the worst weather files were updated to reflect the change in transit time. Additionally, the accident start time has also been adjusted accordingly in order to maximize the peak pond temperature. The table below presents the effectiveness, the transit time, and the accident start time for the sensitivity cases.

Page 4 of 28

Attachment 1 Response to Request for Additional Information Table 1: Sensitivity Case Parameters for RAI-2 Response Case Effectiveness TastWeather File Time*

76% Effectiveness 76% 33 hrs 6AM Start: Worst 33 hrs + Worst 24 hrs + Worst 30 days 82.3% Effectiveness (Case 3_3AM from ATD- 82.3% 36 hrs 3AM Start: Worst 36 hrs + Worst 24 hrs + Worst 30 days 0109 )

87% Effectiveness 87% 39 hrs 12AM Start: Worst 39 hrs + Worst 24 hrs + Worst 30 days

Transit time rounded down to an increment of 3-hrs.

The results (i.e., lake outlet temperature I plant inlet temperature) as a function of hours after the accident are presented in the figure below for each case considered. The peak temperatures are documented in the table below.

Table 2: Results of Sensitivity Study for RAI-2 Response Peak Calculated Lake Outlet!/ Plant Inlet Case Temperature (0F) 76% Effectiveness Case 105.9 82.3% Effectiveness (Case 3_3AM from Calc)10.

87% Effectiveness Case 104.4 Reducing the effectiveness by 6.3% (i.e., enough to reduce the transit time by 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ) results in an increase of 0.7°F in the peak calculated temperature. Increasing effectiveness to 87% (i.e.,

increasing by 4.7%) reduces the peak calculated lake outlet temperature by 0.8°F.

Page 5 of 28

Attachment I Response to Request for Additional Information Figure 1: Plant Inlet Temperature Sensitivity Results for RAI-2 Response Plant Inlet Temperature 108

-U1-82.3% Effectiveness (Transit Time ~36hrs) 3AM Start 106

-- (-76% Effectiveness (Transit Time ~33 hrs) 6AM Start S87% Effectiveness (Transit Time ~39 hrs) 12AM Start 104 0.

S 100 a)J I,-

C S98 96 94 92 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 Hours Conservatisms within the Existingq Analysis (i.e., ATD-0109)

Per thetheresults 2014, actualofgross a hydrographic survey of area and volume conducted by DLZ Industrial Surveying Inc in October the lake at the maximum lake elevation (approximately 590-ft) is greater than modeled in Calculation ATD-01 09. According to survey data, the gross lake area is 101.4 acres and the gross volume is 591.5 acre-ft at an elevation 590-ft. These values are approximately 6% greater than what is modeled in ATD-0109.

An additional sensitivity case utilizing the updated area and volume with a 76% effectiveness determined that the peak UHS temperature is 105.2°F, which is effectively the same as the peak UHS temperature determined in ATD-0109 for "Case 3_3AM" with 82.3% effectiveness.

Pond Effectiveness Sensitivity Study - Conclusions The results of the sensitivity study show that a reduced pond effectiveness value of 76%

decreases the transit time and increases the peak lake outlet temperature to 105.9°F. However, the results in the existing analysis (i.e., Calculation ATD-0109)) are conservative relative to the results of a recent hydrographic survey of the Braidwood UHS which showed that the gross Page 6 of 28

Attachment 1 Response to Request for Additional Information area and volume values used at the maximum lake elevation in Calculation ATD-0109 are approximately 6% less than measured in the survey. Therefore, modeling the UHS with a slightly lower pond effectiveness value is not expected to change the results or conclusions of the LAKET-PC model of the maximum UHS temperature.

SBPB RAI-3 - Raw and processed data on meteorolocqy. heat load, and physical Dond measurements Back qround The LAR does not provide details in most cases of the raw and processed data used in the UHS analyses.

Concern Staff needs to verify that meteorological inputs for the analysis, particularly wind speeds, dry bulb and dew point temperatures, are realistic or conservative. This is especially important because the Braidwood site is significantly closer to Lake Michigan than are either Peoria or Springfield. Also, data files on heat loads would be necessary should NRC proceed with a confirmatory analysis of its own.

Regulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that The UHS has the capability to dissipate the maximum possible total heat load under the worst environmental conditions by conducting independent check calculations. The staff needs the meteorological input data.

Request Provide (in machine-readable form whenever possible) the following information:

Onsite meteorological data

Data from off-site weather stations used in the analyses

Heat loads and flow rates of plant discharges to the UHS pond

Detailed pond geometry, including the height of any berms or structures that could impact wind speed over the water's surface.

Exelon Response to SBPB RAI-3:

Meteorologqical Data/ Data from Off-Site Weather Stations used in the Analyses Meteorological data used in the Braidwood UHS analysis is documented in Attachment B of ATD-01 09 (ATD-01 09 is included as Attachment 5 of Reference 1, herein referred to as ATD-0109). The weather data consists of a combination of data from the National Weather Service (NWS) in Peoria IL (KPIA), Springfield IL (KSPI), and an on-site multi-level instrument tower at Braidwood Generating Station. The source of the weather data is summarized in Table 2 of Attachment B to ATD-0109 as reproduced below:.

Page 7 of 28

Attachment 1 Response to Request for Additional Information Table 3: Source of Weather Data from Attachment B of ATD-01 09 Table 2. Primary and Secondary Data Sources Beining Ending Date Parameter Prmary Data Secondary Date Source Data

_______ ______ ___ ___ ___ ___Source July 5. 1948 December 31. All parameters NWS-Peoria None

__________1951 _________(KPIA) _____

Januar-y 1, December 31. All parameters NWS- None 1952 1956 Springfield

_______ _____ -KSPI)

Januaiy 1. December 31. All parameters NWS-Peoria None 1957 1989 ________(KPIA)

Januaiy, 1. December 31. Dry"bulb On-site N'WS-1990 2012 temperature, meteorological Peoria dewv point tower (KPIA) temperatture.

wind speed.

___________________________wind direction ________________

January 1. December 31. Cloud cov er, NWS-Peoria None 1990 2012 cloud height. (KPIA) precipitation

________________ precipitation _________ _______

The combined meteorological data used as input to LAKET-PC is documented in a text file generated in Attachment B to ATD-0109 and is transmitted as part of this RAI response (Attachment 4, Supporting Data Files Provided on Compact Disc). The file transmitted is:

Name: PIABDW48 12.TXT Type: ASC text Size: 87,231 Kb File creation date/time: 1/30/20 14 8:18 AM Since PIABDW4812.TXT combines data measured at several locations, the wind speed /

direction sensor height varies with the date. The wind sensor height is an input to LAKET-PC.

The wind sensor height for the data contained in the combined weather file is presented below (Table 5 of Attachment B of ATD-0109 ).

Page 8 of 28

Attachment 1 Response to Request for Additional Information Table 4: Wind Sensor Height from Table 5 of Attachment B of ATD-01 09 Table 5. Historical Wind Sensor Height Input for LAKT-PC Be~nin*n Endin2 Sensor Primary Wind Date Date Height Data Source

,(feet) 7/5/1948 11/21/1948 26 NWS-Peoria

_____ _ ___(KPIA) 11/22/1948 12./3*1/ 1951 50 NWS-Peoria

______(KPIh) 1,/1/1952 12/31/1956 49 NWS-Spiingfield

____________(KSPI) 1./1/1957 9/30/1959 50 NWS-Peoria

______(KPLA) 10/ 1/ 1959 12/31 /1989 20 NWS-Peonia

____________(KPIA) (Note 1) 1/1/1990 12/31/2012 34 On-site meteorological

_______________________tower (Note 2)

Note 1: The anenmometer height at .NWS-Peoriawas 20 feet through 9/30/1995.

Starting on 10/1/1995. the anemometer height at NxWS-Peoria was increased to its current height of 32.8 feet.

Note 2: The wind sensor hei ~1t inl LAKET-PC is 34 feet whfich is the anemometer hei~ht of the lowest wind speed level of the on-site tower.

The file (i.e., PIABDW4812.TXT) is a matrix of data, with each row representing a one hour time step. Each column represents a different meteorological parameter, which is presented in the table below (Table 1 of Attachment B of ATD-01 09 ).

Page 9 of 28

Attachment 1 Response to Request for Additional Information Table 5: Meteorological Parameters from Table 1 of Attachment B of ATD-01 09 Table 1. Parameters and Digital Record Format of the Standard W.*eather Data

____File Used by S&L's LAKT~-PC roam Field Parameter Units Lower Upper ]FORTRAN No. Limit Limit Format

______________ ____Specifier 1 Station Code Numlber F7.0

____ (5 digits) _____________

2 Year (4 digits) _____F6.0 3 Month _____F4.0 4 Day ______F4.0 5 Hour"of Day ,F9 .2

[00 (nfidnight)-23 (11 pro)] ___________

6 Clotud Ceiling Height above feet 0 70.000 F9.2 Ground Level 7 Direction Sector from 116 F9.2 which Wind Blows [ 1() -

___1 6(NN )]______

8 Wind speed Knots 0 96 F9.2 9 Dry Bulb Temperature dgF -129 136 F9.2 10 Wet Bulb Temperature deg F -129 136 F9.2 11 Dew Point Temperature deg F -129 136 F9.2 12 Relative Humnidity percent 0 100 F9.2 13 Station Atmospheric inches Hg 25.69 32.01 F9.2 Pressure 14 Cloud Cover Tenths 00 10 F9.2 15 Freezing Precipitation Code 0 1 F9.2 16 One-Hour" Total Liquid 100ths 0 1.200 F9.2

____Equivalent Precipitation inches _______

17 Solar"Radiation BiTU t- 0 4.000 F9.2

______________________ hourn 18 Atmospheric Radiation BTUift'- 220 F9.2 hourn 19 Partial Pressure of Water inches Hg 02.00 F9.2 Vapor___________

Page 10 of 28

Attachment 1 Response to Request for Additional Information Raw meteorological data is also provided in the files (i.e., in Attachment 4 Compact Disc) as documented below.

Directory of \Raw Weather Files 12/04/2015 03:20 PM <DIR> Braidwood Tower 12/04/2015 03:20 PM <DIR> Hourly Precipitation 12/04/2015 03:20 PM <DIR> Hourly Surface Data - Peoria Directory of \Raw Weather Files \Braidwood Tower 01/24/2014 02:07 PM Brwd9098.xlsx 11/22/2013 03:17 PM Weather Data.xlsx The above folder (i.e., "Braidwood Tower") contains raw meteorological data from the on-site meteorological tower at Braidwood. The data are in two Excel spreadsheets and collectively cover 1990 -2012. The on-site tower contractor, Murray & Trettel, supplied the spreadsheets.

SDirectory of \Raw Weather Files\Hourly Precipitation 12/03/2013 09:55 AM. KPIA~precip_95_1 2.txt 01/29/2014 04:32 PM PIA_PRECIP_90_02.txt The above folder (i.e., "Hourly Precipitation") contains raw hourly precipitation data from Peoria, IL from the National Climatic Data Center. The data is in TD-3240 fixed record-length format.

The data is contained in two text files that collectively cover 1990 - 2012.

Directory of \Raw Weather Files \Hourly Surface Data - Peoria 11/19/2004 04:30 PM KPIA_1990.txt 02/05/2009 08:05 AM KP IA_1991 .txt 02/05/20 09 02:44 PM KPIA_1992.txt 01/12/2009 03:10 PM KPIA_1993.txt 10/21/2004 01:31 PM KPIA_1994.txt 11/21/2013 10:24 AM KPIA_1995.txt 11/21/2013 10:25 AM KPIA_1996.txt 01/26/2009 12:10 PM KPIA_1997.txt 02/11/2009 01:57 PM KPIA_1998.txt 01/26/2009 02:12 PM KPIA_1999.txt 01/27/2009 06:55 AM KPIA_2000.txt 01/27/2009 07:53 AM KPIA_2001 .txt 01/27/2009 09:01 AM KPIA_2002.txt 11/21/2013 10:30 AM KPIA_2003.txt 11/21/2013 10:31 AM KPIA_2004.txt 11/21/2013 10:31 AM KPIA_2005.txt 11/21/2013 10:31 AM KPIA_2006.txt 01/13/2012 10:29 PM KPIA_2007.txt 11/21/2013 10:33 AM KPIA_2008.txt 11/21/2013 10:33 AM KPIA_2009.txt Page 11 of 28

Attachment 1 Response to Request for Additional Information 11/21/2013 10:34 AM KPIA_2010.txt 11/21/2013 10:34 AM KPIA_2011 .txt 11/21/2013 10:35 AM KPIA_2012.txt 11/21/2013 10:37 AM KPIA_2013.txt The above folder (i.e., "Hourly Surface Data - Peoria") contains raw hourly surface data from Peoria, IL from the National Climatic Data Center. The data is in DS-3505 "full archive" format.

Each file contains one year of data. The data is contained in 24 annual files that cover the period from 1990 - 2013. Note that because of the time convention used in DS-3505 files

[GMT], a small part of 2013 data is required to process data for all of 2012.

Heat Loads / Flow Rates of Plant Discharcies to the UHS Pond Flow rates of plant discharges for each operating scenario (2, 3, and 4 SX pumps) are documented in Table 6-1 in ATD-01 09 Table 6: Flow Rates from Table 6-1 of ATD-01 09 Table 6-I: Plant Flow _________

~Number of SX Plant Volumetric Flow Plant Volumetric Flow Pumps (gpm) (cfs) 2 f48,000 j106.94 3!_____ 64,000 j142.59 4 96,000 213.89 The total heat load to the UHS as a function of time as presented in the table below:

Page 12 of 28

Attachment 1 Response to Request for Additional Information Table 7: Total Heat Load as a Function of Time TimeTime Total Heat Load (hr) (s) to UHS (BTU/hr) 0.00 10 8.30E+07 0.01 21 5.85E+08 0.01 33 5.75E+08 0.01 50 5.68E+08 0.03 102 5.54E+08 0.04 131 5.47E+08 0.06 199 5.33E+08 0.08 289 5.22E+08 0.10 349 5.17E+08 0.13 459 5.08E+08 0.17 599 4.99E+08 0.19 695 4.94E+08 0.19 695.0012 7.87E+08 0.25 899 7.93E+08 0.28 999 7.96E+08 0.31 1099 7.95E+08 0.33 1199 7.86E+08 0.36 1299 7.77E+08 0.39 1399 7.68E+08 0.49 1764 7.34E+08 0.64 2299 6.35E+08 0.81 2899 5.60E+08 1.00 3599 5.19E+08 1.39 4999 4.58E+08 1.94 6999 3.79E+08 2.78 9999 3.32E+08 5.56 19999 2,67E+08 8.33. 29999 5.51E+08 11.11 39999 4.80E+08 13.89 49999 3.36E+08 16.67 59999 3.28E+08 22.22 79999 3.12E+08 25.00 89999 3.04E+08 27.78 99999 2.97E+08 222.22 799999 2.23E+08 Detailed Pond Geometry Two attachments to this letter are included that show the detailed UHS geometry: Lake Aerial Photograph which is included as Attachment 2 and UFSAR figures 2.4-47 and 2.4-48 which are included as Attachment 3.

Page 13 of 28

Attachment 1 Response to Request for Additional Information SBPB RAI-4 - Description of the UHS outfall Backgqround Based on the application, the thermal discharge to the UHS pond would take place from two submerged 48-inch diameter pipes. There is little or no information on the configuration of these pipes.

Concern The complex circulation that would be caused by discharge from submerged pipes is not described in the UHS analysis and based on an audit conducted at the Braidwood site in July 2015, the NRC staff believes that the water is discharged straight up and above the lake level Regqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that The UHS has the capability to dissipate the maximum possible total heat load by conducting independent check calculations. An understanding of the outfall configuration is needed.

Req uest Provide a detailed description of the UHS outfall, pipe drawings to outfall, results of any testing of the circulation in and around the outfall, and any model or prototype studies (e.g., dye tracer experiments) conduction with regard to its operation. To the extent that your response to the NRC staffs RAI dated September 29, 2015, addresses this request, a reference to that response is acceptable.

Exelon Response to SBPB RAI-4:

EGC does not test the circulation in or around the UHS outfall. Therefore, there are no results of any testing of the UHS outfall that can be provided, nor analytical models or prototype studies that have been performed. EGC provided a description of the UHS outfall, including plant drawing M-900 Sh. 1Y, Revision K, Outdoor Piping Arrangement Units 1 and 2 (see response to GeneraI-RAl-1 and Attachment 2 of Reference 7) which shows the configuration of the two submerged 48-inch diameter pipes.

SBPB RAI Heat Removal Methods on the Shutdown Plant Backgqround A significant heat load on the SX system is provided by the plant that is in a normal shutdown condition following an extended full power run.

Section 4.6 and Attachment C of ATD-0109 specify the heat rejected to the UHS during the DBA Page 14 of 28

Attachment 1 Response to Request for Additional Information Reciulatorv Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that General Design Criterion 5 is met with respect to providing a safe and orderly shutdown of a unit while mitigating an accident in the other unit.

Issue It is not clear that all of the decay heat from the shutdown plant is being removed by the SX system for the duration of the shutdown.

Request Discuss the heat removal and cooldown of the non-accident unit as it relates to the heat load rejected to the UHS [Section 4.6 and Attachment C of ATD-01 09] during the DBA.

Exelon Response to SBPB RAI-5:

Braidwood UFSAR Section 2.4.11.6 discusses the Essential Service Cooling Pond (i.e., the Essential Service Cooling Pond is the alternate reference for the Ultimate Heat Sink):

The ESCP has been reviewed to determine its ability to handle the total heat dissipation requirements of the station assuming a LOCA coincident with a loss of offsite power on one unit and the concurrentorderly shutdown and cooldown from maximum power to cold shutdown of the other unit using normal shutdown operatingprocedures, a single active failure of equipment (to determine the limiting heat input to the UHS), and a coincident design basis seismic event.

The design heat load from the non-accident unit is conservatively calculated as the energy required to reduce the unit from maximum to zero power and reduce the reactor coolant temperature to cold shutdown conditions (<2000 F). The heat load from the non-accident unit is added to the Essential Service Water system, and thus the Ultimate Heat Sink, when the Residual Heat Removal (RHR) System is placed in Shutdown Cooling operation (at approximately 350°F). The heat load input to the UHS models the start of RHR operation at approximately 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months into the event (Reference 1 and 2).

If the Main Condenser is not available, heat is removed from the Reactor Coolant System for maintaining primary temperature or for cooldown by steaming water in the secondary side of the Steam Generators using the Steam Generators Power Operated Relief Valves (PORVs). The Auxiliary Feedwater (AF) System supplies water from the Condensate Storage Tank to the Secondary Side of the Steam Generators.

If the Condensate Storage Tank is not available, water is automatically supplied by the Essential Service Water system from the Ultimate Heat Sink to the suction of the AF pumps. The required volume of cooling water (i.e., less than 300,000 gallons) is insignificant with respect to the entire volume of the UHS (i.e., over 181 million gallons).

Page 15 of 28

Attachment I Response to Request for Additional Information SBPB RAI Surveillance 3.7.9.2 Backgqround Proposed Surveillance Requirement 3.7.9.2 states to verify average water temperature of UHS is < I102°F in accordance with the Surveillance Frequency Control Program.

Regqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that the design of the sensing instrumentation is adequate.

Issue The UHS becomes inoperable with a temperature > 102°F.

Request Discuss how Exelon will ensure that operators become aware, within a reasonable amount of time, that the UHS has exceeded 102°F. What is the maximum time that the UHS could exceed I102°F before the operators became aware of the condition.

Exelon Response to SBPB RAI-6:

Section 3.7 of the Reference 1 submittal describes that in the event that there is an increase in UHS temperature such that a high alarm is received on the SX pump discharge temperature (i.e., high alarm setpoint is 96°F), operators log the SX pump discharge temperature on an hourly basis. Therefore, the maximum period that the UHS temperature may exceed 102°F before operators became aware of the condition is 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months . However, it is not likely that the operators would be unaware of exceeding 102°F for a full hour because, as the SX temperature approaches 102°F, it is expected that the operators will monitor the SX temperature continuously.

SBPB RAI Model Heat Input in 3 Hour Time Segments Backgqround Table 7-3 of ATD 0109 shows an initial temperature of 96.40 F to achieve a maximum of plant inlet temperature of 104 °F. For an initial temperature of 1 02°F the maximum plant inlet temperature is 105.9 °F Table 2 of the LAR shows 13 segments for the 3 pump case and 9 segments for the 4 pump case.

Table 02 of Attachment C of ATD 0109 shows plant temperature rises in intervals of 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months which is used as input data for each segment of the LAKET-PC model.

Page 16 of 28

Attachment 1 Response to Request for Additional Information The calculation output for the limiting case is shown in Attachment 1 of the LAR showing a peak of I105.2°F. The LAR justified 105.2 0 F as a cooling water supply to the equipment cooled by the UHS during a DBA.

Regqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that The UHS has the capability to dissipate the maximum possible total heat load by conducting independent check calculations. An understanding of the sensitivity of the LAR's analysis to the segment size is required.

Issue Table 7-3 shows a relatively large delta between initial temperatures (96.4°F vs 102°F) of the UHS when compared to the delta for the corresponding maximum plant inlet temperatures (1 04°F vs 105.9°F). This could be indicative of coarse input data/coarse methodology.

Plant temperature rise data every 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months in a model with 9 and 13 segments seems to be coarse for output data measured in terms of a tenth of a degree, since each segment is filled and averaged over a 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time period.

The 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time segment of input data may not provide appropriate accuracy for calculation output measured in fractions of a degree Fahrenheit.

The NRC staff notes from the licensee's response to RAI 5 of the April 30, 2015 letter that each plug represents the volume produced by 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months of SX pump run time after the DBA. The staff also notes from Table C1 and Section 2.1.3 of ATD-01 09, if each time step were 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months instead of 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , the initial plug would be 5°F warmer than the plug produced from a 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time step.

Request To evaluate the sensitivity of the analysis to the time step, provide data from performing the limiting cases of 3 SX pump operation using data from plant temperature rise every 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months (with corresponding heat input on an hourly basis, instead of 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ) with an apparent LAKET-PC segment quantity of 36 to 39 segments. Provide a table and figure similar to Table 7-2 [Worst Temperature Cases - 3 SX Pumps] and Figure 7-1 [Limiting 3 SX Pump Case] of ATD 0109 and provide a corresponding Tables similar to Attachment C of ATD-01 09.

Exelon Response to SBPB RAI-7:

Sensitivity analyses were performed to evaluate the impact of the time step on the LAKET-PC results in ATD-0109 (included as Attachment 5 of Reference 1, herein referred to as ATD-01 09).

"Case 3_3AM" of ATD-0109 (i.e., 3 SX pumps in service, accident starting time 3AM) was re-run with a 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months time step to determine the impact of a 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months time step on the results. In addition to changing the time step in LAKET-PC, the temperature difference across the plant must be re-calculated for each time step given the UHS heat load profile. The figure below presents the temperature rise across the plant calculated for a 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time step (as used in ATD-01 09) and a 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months time step.

Page 17 of 28

Attachment 1 Response to Request for Additional Information Figure 2: Plant Temperature Rise (i.e., plant outlet temperature minus plant inlet temperature) 21 .. .................... ........ . . . . . . . ... . . ...... ... .. . .. ... .. . . . .. . . .. ... ......... .............. .... . . . . . .. . . .. . . .. . .. . . . .. . .. ....

20 -4e-New DT (per 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months ) 19 -Ull-Old DT (per 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ) 18

-. 17

.* 15

- 12 11 10 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time After DBA LAKET-PC case runs determined that decreasing the time step from 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months to 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months for "Case 3_3AM" of ATD-0109 increased the peak lake outlet / plant inlet temperature to 106.05°F (see results below).

Table 8: Results of Sensitivity Study for RAI Response 7 TransitPeak CaeiasmesritinTime* Weather File Grs oue& Temp CsCaeDsrpin Step Area (F No. (hr) (F Case 3_3AM from 3AM Start Worst 36 hr + Per ATD-01 09:

1 ATD-0109 - 3 hr time 3 hr 36 Worst 24 hr + Worst 30 day 95.6acres & 105.2 step 555.8 acre-ft Case 3_3AM from 3A tr:Wrt3 r+ Per ATD-01 09:

2 ATD-0109 - 1 hr time 1 hr 36 3AMStrst:2 h Worst 36hray 95.6 acres & 106.05

___step Wos 4h os 0dy 555.8 acre-ft

Transit time rounded down to an increment of 3-hrs.

Page 18 of28

Attachment 1 Response to Request for Additional Information Figure 3: Lake Outlet/ Plant Inlet Temperature for Sensitivity Study for RAI Response 7 Lake Outlet / Plant Inlet Temperature (original area and volume) 10 7 . .. .. . . . . . ................... ...... . ... . .. .. . . ............... ...... .. ............. .... . .. .............. ..... . . .. . .... ...........

106 3hr Timestep 105 -U-I-lhr Timestep 104 S103 W 102 i 01

a. 100 99 98 97 96 0 10 20 30 40 50 60 Hours after Accident Additional Conservatisms for Increased UHS Area and Volume The results of a hydrographic survey conducted by DLZ Industrial Surveying Inc in October 2014 indicated that the actual gross area and volume of the lake at the maximum lake elevation is greater than modeled in Calculation ATD-0 109. Therefore, additional LAKET-PC cases were run with a gross lake area of 101.4 acres and a gross volume of 591.5 acre-ft at an elevation 590-ft. The increased volume also increases the transit time, which in turn requires the weather file to be updated to reflect the longer transit time. The accident start time is also adjusted accordingly in order to maximize the peak UHS temperature. Results for these cases, including the new transit time and new accident start time, are presented in the tables and figures below.

Results show that the peak lake outlet / plant inlet temperature is reduced from 106. 05°F to 105.5°F for the 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months time step case with increased area and volume.

Page 19 of 28

Attachment 1 Response to Request for Additional Information Table 9: Results of Sensitivity Study for RAI Response 7, with Consideration of Additional Lake Volume CaeTime TastGross Volume & Pa Temp Cae Case Description Time Weather File No. Step Area (F (hr) (F Case 1 w/ new area &

volume

- New area and vol New Area &Vol.

Worst Start:

12AM + Worst3930hrday 24 hr Worst + 101.4 acres & 104.5 33 hr 39

- New weather file for 39 hr 591.5 acre-ft transit time

- 12AM accident start time Case 2 wI/new area &

volume

- New area and vol New Area & Vol:

12AM Start. Worst 39 hr +

-Nwwahrfiefr3 r 1 hr 41 Worst 24 hr + Worst 30 day 101 .4 acres & 105.5 transit time

-12AM accident start time Page 20 of 28

Attachment 1 Response to Request for Additional Information Figure 4: Lake Outlet/ Plant Inlet Temperature for Sensitivity Study for RAI Response 7 with Consideration of Additional Lake Volume Lake Outlet / Plant Inlet Temperature (updated area and volume) 10 7 .. . ... .. . . . . . .

16 -,.--3hr Timestep

-U-II-lh r Timestep 105 *-

C* 101 99 ........ ..

98 ..... . . ... ... ... ... . . ... ...... .

97 . .. . . ... .. ... ......... ... ...... ... . ...

96 .. . . .. . . .. . . . . . .. .. . . . . . . . .. . . . ... . . . . . . . .. .. . . . .. . . . . . .. . ... . . .. . .

0 10 20 30 40 50 60 Hours after Accident Conclusion The use of the 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time step is considered acceptable because a smaller time step breaks the pond up into more discreet cells, which reduces the impact of mixing on the temperature rise calculation. As shown above, there are significant conservatisms in the pond area and volume values used in the existing analysis (i.e., ATD-0109). A 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time step divides the pond into fewer, but slightly larger discreet cells which is akin to modeling mixing of water (within each discreet cell) discharged into the UHS. Given the geometry of the pond, accounting for some mixing via a 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time step is considered appropriate.

SBPB RAI-8 - Description of Sedimentation in UHS Pond Backgqround The LAR considered 3 inches of sedimentation in the UHS calculations for a sensitivity analysis. UFSAR Figure 2.4-48 shows a bottom/pond elevation of 584'-0". SR 3.7.9.3 verifies bottom level < 584 ft MSL in accordance with the Surveillance Frequency Control Program.

Page 21 of 28

Attachment 1 Response to Request for Additional Information The licensee's sensitivity analysis showed insignificant effect on peak UHS temperature with 3 inches of sedimentation.

Other licensees have considered as much as 18 inches of sedimentation in their submerged UHS pond.

Regqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify that The UHS has the capability to dissipate the maximum possible total heat load by conducting independent check calculations. An understanding of the basis for 3 inches of sedimentation is required.

Request Discuss whether SR 3.7.9.3 verifies validity of the design input of less than 3 inches of sedimentation for the UHS calculation by addressing accuracy of measurements, how often measurements are taken and any historical trends that support the frequency of measurements.

Exelon Response to SBPB RAI-8:

Procedure BwVSR 3.7.9.3 implements Surveillance Requirement 3.7.9.3. In accordance with the surveillance frequency control program, the surveillance frequency is 18 months.

The last survey for the Ultimate Heat Sink (UHS) was performed by DLZ Industrial in October of 2014. DLZ setup a Global Positioning System (GPS) Real Time Kinematic (RTK) base station and checks were made by the contractor to ensure accurate locations and elevations were being observed. Prior to beginning the survey, a bar check, sound velocity casts, and manual polling was performed to verify accurate depth measurements. The surveillance recorded over 35,000 depth points and reported the mean value as 583.7 feet. No adjustments are applied to this value due to measurement accuracy.

Surveillance procedure BwVSR 3.7.9.3 verifies the validity of the design input of a maximum depth of 3 inches for the sedimentation layer. No historical trend of sedimentation build-up above elevation 584 ft has been recorded.

In addition, as discussed in UFSAR Section 2.4.11.6, the Braidwood Ultimate Heat Sink has low susceptibility to sedimentation build-up above elevation 584 ft.

SBPB RAI-9 - Define limiting oil temperature Backgqround Oil coolers are discussed as having at least 10°F margin between the maximum oil temperature reached and the limiting oil temperature.

Issue*

It is not clear what is meant by "limiting oil temperature."

Page 22 of 28

Attachment I Response to Request for Additional Information Regqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify the capability of the system to provide adequate cooling to equipment.

Reauest Clarify the term "limiting oil temperature" as to whether this is the temperature at which immediate bearing damage will begin to occur or whether this is a temperature at which the associated oil will begin to degrade more quickly or is a limit with margin imposed by the vendor or other limit.

Exelon Response to SBPB RAI-9:

Each oil cooler cooled by the SX system was evaluated for the ability to reject the design heat load at the maximum UHS temperature while maintaining oil temperatures below limiting values.

The limiting oil temperatures are based on analyzed limits for continued pump operation and limits provided by the vendors above which equipment shutdown is recommended.

SBPB RAI-10 - Thermodynamic simplified models, design calculations

Background

The licensee has stated in Section 3.5 of the LAR:

A formal engineering evaluation has been completed to review the impact of the increase in the UHS TS maximum temperature of 102°F and the increase in the maximum post-accident SX inlet temperature to 105.2°F. This was completed by reviewing the evaluations and design calculations for equipment cooled by the SX and CC systems and developing simplified models which were validated against the results of the existing calculations. The models replicated the analyses contained in the existing evaluations and design calculations with the increased SX temperature. Resulting margins were reviewed and it was determined that equipment cooled by the SX and CC systems have adequate margin at the elevated UHS temperature without physical plant modifications. The specific component analyses impacted by this evaluation have been identified and will be updated in accordance with the existing Engineering Change processes and as outlined in Regulatory Commitment #1.

Concern The staff cannot make a reasonabie assurance determination of acceptability based on simplified models that replicate the design calculations. The specific design work performed in accordance with 10OCFR 50 Appendix B which justifies the amendment request, must be satisfactorily completed before NRC can make this determination.

Page 23 of 28

Attachment 1 Response to Request for Additional Information Recjulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify the capability of the system to provide adequate cooling to equipment.

Reaquest The licensee is requested to complete the license amendment process by completing design calculations per 10 CFR 50 Appendix B for equipment cooled by the UHS. Section 3.5 of the LAR should be resubmitted basing the evaluation of equipment on the design calculations, not simplified models.

Exelon Response to SBPB RAI-10:

Exelon will complete design calculations in accordance with 10 CFR 50 Appendix B for the equipment that is cooled by the Ultimate Heat Sink via the Essential Service Water System.

The calculations will be completed by January 29, 2016.

Section 3.5 of the UHS LAR will be revised based on the results of the design calculations and will be resubmitted by February 12, 2016.

SBPB RAI-11I - Main Control Room Chiller Backaqround provides the vendor data sheet for the Main Control Room Chiller Condenser and shows a flow rate of 950 GPM at 100 F inlet temperature.

Issue The licensee states that over 25% margin exists at maximum SX inlet temperature of 105.2 F using reduced fouling factors based on as found fouling factors of other heat exchangers in the GL-89-1 3 program. The Main Control Room Chiller operates frequently; some GL 89-13 heat exchangers operate infrequently and thus have small fouling factors.

Regqulatory Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify the capability of the system to provide adequate cooling to equipment.

Request Identify the equipment associated with the "as found fouling factors of other heat exchangers in the GL-89-13 program," that were used to determine that the MCR chillers have over 25 %

margin. Compare running times with the MCR chillers (if necessary). Discuss and provide validation of the evaluation which shows "over 25 % margin" at the maximum post-accident SX inlet temperature to 105.2 F.

Page 24 of 28

Attachment I Response to Request for Additional Information Exelon Response to SBPB RAI-I11:

The original evaluation of the Main Control Room Chiller as discussed in Reference 1, consisted of two models: one for the chiller condenser and one for the chiller evaporator. These were decoupled using defined refrigerant pressures in the condenser and evaporator based on a single operating point. The evaluation of increased SX inlet temperature to the chiller condenser at this pressure necessitated crediting a reduced fouling factor of 0.0010 hr-ft2 -°F/Btu from the design fouling factor of 0.0015 hr-ft 2-°F/Btu.

Since the original LAR submittal, a new detailed calculation has been performed using a model which integrates the chiller condenser and evaporator including detailed modeling of the refrigerant cycle. This model allows for variation of the pressure in the chiller condenser and evaporator (within the machine operational limits) and thus demonstrates greater margin.

Within the integrated model, the original design fouling factor of 0.0015 hr-ft2 -°F/Btu has been utilized and the results show that the Main Control Room Chiller has margin to accommodate SX inlet water temperatures of up to 106°F. The margin at the current worst tube plugging level is 339,967 BTU/hr or 18% (2,180,000 BTU/hr capacity vs 1,840,033 BTU/hr required).

Note, that the required heat load (i.e., 1,840,033 BTU/hr) has been updated from the value that was included in the LAR RAI response letter of April 30, 2015 (i.e., 1,730,735 BTU/hr). The higher heat load includes Braidwood specific equipment heat loads, and adjustments for consideration of the solar heat load.

SBPB RAI-12 - Emergiency Diesel Generators Back~qround , Emergency Diesel Generator (EDG) Jacket Water Coolers, is the vendor data sheet and shows a tube side flow rate of 1641 GPM at 100°F inlet temperature.

Issue The licensee states all engine coolers cooled by SX have margin for the increased SX temperature. The LAR states that all equipment cooled by UHS is evaluated for the limiting UHS temperature of 105.2 F.

Reaqulatorv Basis NUREG-0800, Standard Review Plan, provides guidance to the reviewer to verify the capability of the system to provide adequate cooling to equipment.

Req uest

1) The licensee is requested to provide the following information for the emergency diesel generators: a) design fouling factor, b) as tested fouling factor (Generic Letter 89-13 test results) and frequency of testing, c) tube plugging allowance, d) actual number of tubes Page 25 of 28

Attachment 1 Response to Request for Additional Information plugged, e) design heat load, f) actual SX flow rate g) calculated heat removal capability with design fouling factor and at 105.2 F (specify # tubes plugged and SX flow rate).

2) Using the calculated heat removal capability as requested above, provide the margin at the increased SX temperature.

Exelon Response to SBPB RAI-12:

1) The Emergency Diesel Generators (EDGs) Jacket Water Heat Exchangers are shell and tube type and are configured as a staked pair of TEMA Type E heat exchangers for each EDG. Cooling water from the EDG Jacket Water system flows through the shell side of the heat exchanger while Essential Service Water (SX) from the UHS flows through the tube side. Each heat exchanger is referred to as a bundle; each bundle has two passes of tubes.

a) The design fouling factor is 0.0015 hr-ft 2 -°F/BTU.

b) The Jacket Water Heat Exchangers for the EDGs are inspected and cleaned in accordance with the Braidwood Generic Letter 89-13 Program. A performance test is not performed on the heat exchangers; a tested fouling factor is not available.

c) A I0CFR Appendix B design analysis has been completed. The heat exchanger is able to remove the design heat load with a total of 54 tubes plugged per bundle. A conservative fouling factor of 0.0025 hr-ft2 -°F/BTU was used in the analysis.

d) The actual number of tubes plugged is as follows:

Table 10: EDGs Jacket Water Heat Exchangers Tubes Plugged for RAI Response 12 Jacket Water Heat Exchanger Tubes Bundle Plugged 1A EDG Upper 2 1A EDG Lower 13 1B EDG Upper 17 1B EDG Lower 30 2A EDG Upper 2 2A EDG Lower 4 2B EDG Upper 2 2B EDG JW Cooler Lower I Bundle e) The design heat load for the Emergency Diesel Generators Jacket Water Heat Exchanger is 12,214,000 BTU/hr. This is the heat associated with engine operation at 110% of rated load.

f) The SX flow rate to the Jacket Water Heat Exchanger is verified to be in the range of 1870-1920 gpm during surveillance testing of the Emergency Diesel Generators.

With this range established, the actual flow rate remains above 1,650 gpm with SX pump discharge pressure approaching post-LOCA conditions.

Additionally, a sensitivity case performed showed that the Emergency Diesel Generators Jacket Water Heat Exchanger is able to remove the design basis heat load with the SX flow rate as low as 1,400 gpm.

Page 26 of 28

Attachment 1 Response to Request for Additional Information g) The 2calculated heat removal capability with a conservative fouling factor of 0.0025 hr-ft -°F/BTU and a conservative SX temperature of 106 °F is 12,214,000 BTU/hr with 54 tubes plugged per bundle and an SX flow rate of 1,650 gpm (Reference 1).

2) The table below provides margins in terms of tubes plugged:

Table 11: EDGs Jacket Water Heat Exchanger Margin to Allowed Tubes Plugged (RAI Response 12)

Tubes Allowed Margin Plugged Tube 1A EDG JW Cooler Upper 2 54 52 Bundle 1A EDG JW Cooler Lower 13 54 41 Bundle 1 B EDG JW Cooler Upper 17 54 37 Bundle I1B EDG JW Cooler Lower 30 54 24 Bundle 2A EDG JW Cooler Upper 2 54 52 Bundle 2A EDG JW Cooler Lower 4 54 50 Bundle 2B EDG JW Cooler Upper 2 54 52 Bundle 2B EDG JW Cooler Lower 1 54 53 Bundle Page 27 of 28

Attachment 1 Response to Request for Additional Information

References:

1) Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Request for a License Amendment to Braidwood Station, Units I and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,"' dated August 19, 2014 (ML14231A902)

2) Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units I and 2, Technical Specification 3.7.9, "Ultimate Heat Sink," dated April 30, 2015 (ML15120A396)

3) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC) Additional RAI Regarding Containment Analysis for Braidwood UHS LAR (MF4671 and MF4672),

dated July 22, 2015

4) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC) Need Clarification Conference Call Regarding Your April 30, 2015 Response to SCVB-RAI-1(a), dated August 12, 2015 (ML15224B548)

5) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC) Additional RAIs Regarding Braidwood Ultimate Heat Sink Temperature Amendment, dated September 29, 2015

6) Letter from 0. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,"' dated October 9, 2015

7) Letter D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9,.

'Ultimate Heat Sink,"' dated October 30, 2015

8) Letter 0. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9,

'Ultimate Heat Sink,"'" dated November 9, 2015

9) Email from J. Wiebe (NRC) to J. Krejcie (Exelon Generation Company, LLC) Preliminary Balance of Plant RAIs for Braidwood Ultimate Heat Sink LAR, dated October 26, 2015 Page 28 of 28

Attachment 2 Braidwood Station UHS Lake Aerial Photograph

Attachment 3 UFSAR figures 2.4-47 and 2.4-48

REVISION 16 DECEMBER 2016 200 0 ~ 400 SCME hN P!ET BRAIDWOOD STATION UPDATED FINAL SAFETY ANALYSIS REPORT FIGURE 2.4-47 ESSENTIAL COOLING POND

REVISION 16 DECEMBER 2016 ROAD SECTION A-A SECTION B-B, SECTION 0-D) n STWE OA SECTION C-C SECTION E-E 20 IC 0 IO E SCALE lIN FEET BRAIDWOODSTATION UPDATEDFINAL SAFETYANALYSIS REPORT SECTION F-F FIGURE 2.4-48 ESSENTIAL COOLING POND SECTIONS

Attachment 4 Supporting Data Files Provided on Compact Disc