Text

Response to Request for Additional Information Related to License Amendment Request to Technical Specification 3.7.3, Ultimate Heat Sink
	ML13022A476
Person / Time
Site:	LaSalle
Issue date:	01/18/2013
From:	Simpson P; Exelon Generation Co
To:	; Office of Nuclear Reactor Regulation, Document Control Desk
References
	RS-13-002, TAC ME9076, TAC ME9077
	Download: ML13022A476 (114)
	v • d • e

RS-13-002 10 CFR 50.90 January 18, 2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject:

Response to Request for Additional Information Related to License Amendment Request to Technical Specification 3.7.3, "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 LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, 'Ultimate Heat Sink,"'

dated July 12, 2012 2)

Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Supplemental Information Related to License Amendment Request to LaSalle County Station, Units 1 and 2 Technical Specification 3.7.3, 'Ultimate Heat Sink,"' dated September 17, 2012

3) Letter from N. J. DiFrancesco (U. S. Nuclear Regulatory Commission) to M. J. Pacilio (Exelon Generation Company, LLC), "LaSalle County Station, Units 1 and 2 - Request for Additional Information Related to License Amendment Request to Technical Specification 3.7.3 Ultimate Heat Sink (TAC Nos. ME9076 and ME9077)," dated January 9, 2013 In Reference 1, Exelon Generation Company, LLC, (EGC) requested an amendment to the Technical Specifications (TS) of Facility Operating License Nos. NPF-1 1 and NPF-1 8 for LaSalle County Station, Units 1 and 2 (LSCS). The license amendment would allow the TS temperature limit of the cooling water supplied to the plant from the Ultimate Heat Sink (UHS) to vary with the observed diurnal cycle. EGC supplemented Reference 1 with a letter dated September 17, 2012 (Reference 2).

The U. S. Nuclear Regulatory Commission (NRC) requested additional information to complete its review of the proposed license amendment request in Reference 3. Attachments 1, 2 and 3 provide the requested information, with the exception of Questions 3 and 5 of Reference 3. As discussed with the NRC on January 17, 2013, it was agreed that EGC would provide the response for those questions in a separate submittal by February 11, 2013.

1 RS-13-002 10 CFR 50.90 January 18, 2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject:

Response to Request for Additional Information Related to License Amendment Request to Technical Specification 3.7.3, "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 LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, 'Ultimate Heat Sink,'"

dated July 12, 2012

2) Letter from D. M. Gullott (Exelon Generation Company, LLC) to u. S. Nuclear Regulatory Commission, "Supplemental Information Related to License Amendment Request to LaSalle County Station, Units 1 and 2 Technical Specification 3.7.3, 'Ultimate Heat Sink,'" dated September 17,2012

3) Letter from N. J. DiFrancesco (U. S. Nuclear Regulatory Commission) to M. J. Pacilio (Exelon Generation Company, LLC), "LaSalle County Station, Units 1 and 2 - Request for Additional Information Related to License Amendment Request to Technical Specification 3.7.3 Ultimate Heat Sink (TAC Nos. ME9076 and ME9077)," dated January 9,2013 In Reference 1, Exelon Generation Company, LLC, (EGC) requested an amendment to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station, Units 1 and 2 (LSCS). The license amendment would allow the TS temperature limit of the cooling water supplied to the plant from the Ultimate Heat Sink (UHS) to vary with the observed diurnal cycle. EGC supplemented Reference 1 with a letter dated September 17, 2012 (Reference 2).

The U. S. Nuclear Regulatory Commission (NRC) requested additional information to complete its review of the proposed license amendment request in Reference 3. Attachments 1, 2 and 3 provide the requested information, with the exception of Questions 3 and 5 of Reference 3. As discussed with the NRC on January 17, 2013, it was agreed that EGC would provide the response for those questions in a separate submittal by February 11, 2013.

January 18, 2013 U. S. Nuclear Regulatory Commission Page 2 During the development of the response, a previously incorporated refinement was identified related to the computer program used to model the LSCS UHS, LAKET-PC. It was identified that the equation in Reference 1 associated with net solar radiation to the UHS had been revised to utilize a more detailed approach. This refinement is described in Attachment 2 of 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 2. The additional information provided in this submittal does not affect the bases for concluding that the proposed license amendments do 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 attachments are being provided to the designated State of Illinois official.

There are no regulatory commitments contained in this submittal.

Should you have any questions concerning this letter, please contact Ms. Lisa A. Simpson at (630) 657-2815.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 18th day of January 2013.

Patrick R. Simpson Manager - Licensing Exelon Generation Company, LLC Attachments:

1)

Response to Request for Additional Information

2) Supporting Information - Response to NRC Question 1

3) Supporting Information - Requested Plant Data cc:

Illinois Emergency Management Agency - Division of Nuclear Safety Respectfully, January 18, 2013 U. S. Nuclear Regulatory Commission Page 2 During the development of the response, a previously incorporated refinement was identified related to the computer program used to model the LSCS UHS, LAKET-PC. It was identified that the equation in Reference 1 associated with net solar radiation to the UHS had been revised to utilize a more detailed approach. This refinement is described in Attachment 2 of 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 2. The additional information provided in this submittal does not affect the bases for concluding that the proposed license amendments do 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 attachments are being provided to the deSignated State of Illinois official.

There are no regulatory commitments contained in this submittal.

Should you have any questions concerning this letter, please contact Ms. Lisa A. Simpson at (630) 657-2815.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 18th day of January 2013.

Res~R Patrick R. Simpson Manager - Licensing Exelon Generation Company, LLC Attachments:

c:

1) Response to Request for Additional Information

2) Supporting Information - Response to NRC Question 1

3) Supporting Information - Requested Plant Data cc:

Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT 1 Response to Request for Additional Information By letter to the U. S. Nuclear Regulatory Commission (NRC) dated July 12, 2012, Exelon Generation Company, LLC, (EGC) requested an amendment to the Technical Specifications (TS) of Facility Operating License Nos. NPF-1 1 and NPF-18 for LaSalle County Station, Units 1 and 2 (LSCS). The license amendment would allow the TS temperature limit of the cooling water supplied to the plant from the Ultimate Heat Sink (UHS) to vary with the observed diurnal cycle. This letter was supplemented by EGC letter dated September 17, 2012. In a letter dated January 9, 2013, the NRC requested additional information to complete its review of the proposed license amendment request.

NRC Question 1:

Review of Inputs

Background:

Section 4, item (1), "Surface Weather Observations" of Attachment K, pages K2 and K3 states:

"Raw surface weather observations (Reference 2) from KPIA [weather station in Peoria, Illinois] covered the period of record from January 1, 1995 through December 31, 2004.

NCDC [National Climatic Data Center] subjects meteorological data to rigorous quality control checks before archiving it. Nevertheless, meteorological databases still typically include gaps and data values outside of valid ranges. The archived data included most of the weather parameters required by Laket [LakeT-PC computer model] (Table 1), with the following exceptions: freezing precipitation code, solar radiation, atmospheric radiation, and partial pressure of water vapor. S&L [Sargent and Lundy] estimated those parameters using standard methods. To check the thermodynamic consistency of the input data, S&L estimated hourly wet bulb temperature, dew point temperature and humidity to ensure consistency between those parameters and the (on-site) dry-bulb temperature. In instances when the dew point temperature at KPIA exceeded the dry-bulb temperature at the on-site meteorological tower, the dew point temperature at KPIA was set equal to the dry-bulb temperature observed at the on-site tower. This ensured thermodynamic consistency between the relative humidity and the dry-bulb, wet-bulb temperature and dew point temperatures."

Requests: For each of the estimated parameters (particularly for solar radiation and atmospheric radiation), please provide a detailed description of the methodology, inputs, assumptions, and bases used to make the estimates. Additionally, provide an example calculation demonstrating how each type of estimate was generated.

EGC Response to Question 1:

The response to Question 1 is provided in Attachment 2 to this submittal.

NRC Question 2:

Background:

The treatment of wind speed is an important consideration for UHS analysis heat transfer. Section M4.2 of Attachment M, states that the meteorological tower measurement height is 33 feet (ft) above ground level (or 752 ft. above mean sea level [MSL]) and the base of the meteorological tower is at 719 ft MSL. The 33-ft (10 meter) measurement height is used in the LakeT-PC model is not discussed. Thus, assuming: (1) the meteorological measurements Page 1 of 23 ATTACHMENT 1 Response to Request for Additional Information By letter to the U. S. Nuclear Regulatory Commission (NRC) dated July 12, 2012, Exelon Generation Company, LLC, (EGC) requested an amendment to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station, Units 1 and 2 (LSCS). The license amendment would allow the TS temperature limit of the cooling water supplied to the plant from the Ultimate Heat Sink (UHS) to vary with the observed diurnal cycle. This letter was supplemented by EGC letter dated September 17, 2012. In a letter dated January 9, 2013, the NRC requested additional information to complete its review of the proposed license amendment request.

NRC Question 1:

Review of Inputs

Background:

Section 4, item (1), "Surface Weather Observations" of Attachment K, pages K2 and K3 states:

"Raw surface weather observations (Reference 2) from KPIA [weather station in Peoria, illinoiS] covered the period of record from January 1, 1995 through December 31, 2004.

NCDC [National Climatic Data Center] subjects meteorological data to rigorous quality control checks before archiving it. Nevertheless, meteorological databases still typically include gaps and data values outside of valid ranges. The archived data included most of the weather parameters required by Laket [LakeT-PC computer model] (Table 1), with the following exceptions: freezing precipitation code, solar radiation, atmospheric radiation, and partial pressure of water vapor. S&L [Sargent and Lundy] estimated those parameters using standard methods. To check the thermodynamic consistency of the input data, S&L estimated hourly wet bulb temperature, dew point temperature and humidity to ensure consistency between those parameters and the (on-site) dry-bulb temperature. In instances when the dew point temperature at KPIA exceeded the dry-bulb temperature at the on-site meteorological tower, the dew point temperature at KPIA was set equal to the dry-bulb temperature observed at the on-site tower. This ensured thermodynamic consistency between the relative humidity and the dry-bulb, wet-bulb temperature and dew point temperatures."

Reguests: For each of the estimated parameters (particularly for solar radiation and atmospheric radiation), please provide a detailed description of the methodology, inputs, assumptions, and bases used to make the estimates. Additionally, provide an example calculation demonstrating how each type of estimate was generated.

EGC Response to Question 1:

The response to Question 1 is provided in Attachment 2 to this submittal.

NRC Question 2:

Background:

The treatment of wind speed is an important consideration for UHS analysis heat transfer. Section M4.2 of Attachment M, states that the meteorological tower measurement height is 33 feet (ft) above ground level (or 752 ft. above mean sea level [MSLJ) and the base of the meteorological tower is at 719 ft MSL. The 33-ft (10 meter) measurement height is used in the LakeT-PC model is not discussed. Thus, assuming: (1) the meteorological measurements Page 1 of 23

ATTACHMENT 1 Response to Request for Additional Information were made at 752 ft MSL, (2) the Ryan wind function is applicable at 2 meters (6.6 ft) above the water surface (Section 2.3, NUREG-0693, "Analysis of Ultimate Heat Sink Cooling Ponds,"

November 1980, (ADAMS Accession No. 8012120331)), and (3) the nominal lake surface level is 690 ft MSL during a UHS heatup event, please answer the following:

Requests:

a.

How does the analysis account for the difference in heights between LSCS's meteorological measurements (752 ft MSL) and the nominal lake surface level (690 ft MSL) during a UHS heatup event?

b. How were the wind gradients modeled and why are they conservative for LSCS's site characteristics for UHS cooling performance?

c. Justify the applicability of the Hefner and Ryan wind function to the LSCS's site characteristics. Additionally, discuss the rational and effect of switching between the wind functions when the Ryan predicted lake temperature is within 2.5 OF of the natural lake temperature (as calculated by the Hefner function).

EGC Response to Question 2a:

Both the Ryan and Lake Hefner wind functions utilized within LAKET-PC are based on a wind speed 2 meters (6.56 ft) above the water level. The wind speed and the elevation (above ground level) at which it was measured are necessary inputs to LAKET-PC. The program then corrects the wind speed based on the measured elevation to a reference elevation of 2 meters above ground per the following equation:

WNDCOR =1.15 mph 1 * (6.5WINDZ )0 3 (Reference 1) knots

where, WNDCOR = wind correction factor to 2m (6.56 ft) above ground level WINDZ

= measurement elevation above ground level (ft) 1.15

= Conversion factor from knots to mph This equation, used to model the wind gradient, is discussed in further detail in the response to question 2b. The wind speed is corrected to 2 meters above the ground level at the location where it is measured. The UHS pond is located at a site other than where the wind is measured. The inherent assumption in using wind data not measured precisely at the location of the UHS pond is that the wind profile at the measured location is applicable to the location of the pond. This is a reasonable assumption for LSCS because 1) the wind speed is measured at LSCS, relatively close to the UHS pond and 2) the topography of the area is generally flat with no significant obstructions that would cause significant changes in the wind profile across this relatively small distance.

For these reasons, the differences in wind profiles at the wind measurement site and the UHS pond site are considered to be insignificant. The wind profile is a function of the relative height above the ground. Although the UHS pond is located at a lower elevation, the wind profile is Page 2 of 23 ATTACHMENT 1 Response to Request for Additional Information were made at 752 ft MSL, (2) the Ryan wind function is applicable at 2 meters (6.6 ft) above the water surface {Section 2.3, NUREG-0693, "Analysis of Ultimate Heat Sink Cooling Ponds,"

November 1980, (ADAMS Accession No. 8012120331>>, and (3) the nominal lake surface level is 690 ft MSL during a UHS heatup event, please answer the following:

Requests:

a. How does the analysis account for the difference in heights between LSCS's meteorological measurements (752 ft MSL) and the nominal lake surface level (690 ft MSL) during a UHS heatup event?

b. How were the wind gradients modeled and why are they conservative for LSCS's site characteristics for UHS cooling performance?

c. Justify the applicability of the Hefner and Ryan wind function to the LSCS's site characteristics. Additionally, discuss the rational and effect of switching between the wind functions when the Ryan predicted lake temperature is within 2.5 of of the natural lake temperature (as calculated by the Hefner function).

EGC Response to Question 2a:

Both the Ryan and Lake Hefner wind functions utilized within LAKET -PC are based on a wind speed 2 meters (6.56 ft) above the water level. The wind speed and the elevation (above ground level) at which it was measured are necessary inputs to LAKET-PC. The program then corrects the wind speed based on the measured elevation to a reference elevation of 2 meters above ground per the following equation:

where, WNDCOR = 1.15[ mPh]. (6.56/

)0.3 knots

!WINDZ (Reference 1)

WNDCOR WINDZ 1.15

= wind correction factor to 2m (6.56 ft) above ground level

= measurement elevation above ground level (ft)

= Conversion factor from knots to mph This equation, used to model the wind gradient, is discussed in further detail in the response to question 2b. The wind speed is corrected to 2 meters above the ground level at the location where it is measured. The UHS pond is located at a site other than where the wind is measured. The inherent assumption in using wind data not measured precisely at the location of the UHS pond is that the wind profile at the measured location is applicable to the location of the pond. This is a reasonable assumption for LSCS because 1) the wind speed is measured at LSCS, relatively close to the UHS pond and 2) the topography of the area is generally flat with no significant obstructions that would cause significant changes in the wind profile across this relatively small distance.

For these reasons, the differences in wind profiles at the wind measurement site and the UHS pond site are considered to be insignificant. The wind profile is a function of the relative height above the ground. Although the UHS pond is located at a lower elevation, the wind profile is Page 2 of 23

ATTACHMENT 1 Response to Request for Additional Information similar to the wind profile at the measurement site and thus, the measured wind speed corrected to 2 meters above the ground is a reasonable value for the wind speed at 2 meters above the nearby UHS pond water level.

EGC Response to Question 2b:

LAKET-PC models wind gradients (as a function of the elevation above ground level) per the following equation:

WNDCOR =1.15 knots mph-(6.SWINDZ)o.3 (Reference 1)

where, WNDCOR = wind correction factor to 2m (6.56 ft) above ground level WINDZ

= measurement elevation above ground level (ft) 1.15

= Conversion factor from knots to mph The wind speed extrapolation is a power law equation correcting the wind speed to an elevation of 2 meters above the ground level (the reference wind speed elevation used for wind functions in MIT Report No. 161 (Reference 2)). There are a variety of exponential factors that have been used over the years in the power law equation, which are introduced in Section 2.2.4 of the structural engineering book, "Wind Effects on Structures" (Reference 1). The original LAKET -

PC program was developed in 1971 - 1972, and the only reference for the power law exponent cited in the book pre-dating LAKET-PC recommends an exponent of 0.28 for suburban terrain, and 0.16 for open terrain.

As the wind measurement height is always expected to be above 2 meters, a higher exponent is more conservative for extrapolating wind speeds to 2 meters since lower wind speeds are conservative for the UHS analysis. The two other (more recent) references for the exponent in "Wind Effects on Structures" (Reference 1) suggest even lower exponents for the suburban terrain. Thus, LAKET-PC uses a conservatively bounding value of 0.3 for the exponent.

EGC Response to Question 2c:

Attachment N of Calculation L-002457 (Reference 3) reviewed the methodology utilized in LAKET-PC and confirmed its acceptability when compared to NUREG -0693, "Analysis of Ultimate Heat Sink Cooling Ponds," (Reference 4). The attachment reviewed the LAKET-PC manual and source code and compared the LAKET-PC analysis approach to NUREG-0693.

The use of the Ryan and Lake Hefner wind functions was discussed in detail.

LAKET-PC calculates evaporation based on both natural and forced evaporation rates. The natural lake temperature is defined as the temperature of the lake reacting purely to natural influences (no additional heat added to the lake). The natural evaporation is calculated as the evaporation from the total surface area of the lake at its natural temperature. Section 2.4.1 of MIT Report No. 161 (Reference 2) discusses evaporation from a free (natural) water surface.

The MIT report notes that test data from several lakes (Lake Hefner, Lake Mead, and Lake Eucumene in Australia) confirms that the Lake Hefner evaporation wind function performed satisfactorily. Thus, LAKET-PC utilizes the Lake Hefner wind function when characterizing the natural evaporation.

Page 3 of 23 ATTACHMENT 1 Response to Request for Additional Information similar to the wind profile at the measurement site and thus, the measured wind speed corrected to 2 meters above the ground is a reasonable value for the wind speed at 2 meters above the nearby UHS pond water level.

EGC Response to Question 2b:

LAKET-PC models wind gradients (as a function of the elevation above ground level) per the following equation:

where, WNDCOR = 1.15[ mPh]. (6.56/

)0.3 knots IWINDZ (Reference 1)

WNDCOR WINDZ 1.15

= wind correction factor to 2m (6.56 ft) above ground level

= measurement elevation above ground level (ft)

= Conversion factor from knots to mph The wind speed extrapolation is a power law equation correcting the wind speed to an elevation of 2 meters above the ground level (the reference wind speed elevation used for wind functions in MIT Report No. 161 (Reference 2)). There are a variety of exponential factors that have been used over the years in the power law equation, which are introduced in Section 2.2.4 of the structural engineering book, "Wind Effects on Structures" (Reference 1). The original LAKET-PC program was developed in 1971 - 1972, and the only reference for the power law exponent cited in the book pre-dating LAKET-PC recommends an exponent of 0.28 for suburban terrain, and 0.16 for open terrain. As the wind measurement height is always expected to be above 2 meters, a higher exponent is more conservative for extrapolating wind speeds to 2 meters since lower wind speeds are conservative for the UHS analysis. The two other (more recent) references for the exponent in "Wind Effects on Structures" (Reference 1) suggest even lower exponents for the suburban terrain. Thus, LAKET-PC uses a conservatively bounding value of 0.3 for the exponent.

EGC Response to Question 2c:

Attachment N of Calculation L-002457 (Reference 3) reviewed the methodology utilized in LAKET-PC and confirmed its acceptability when compared to NUREG-0693, "Analysis of Ultimate Heat Sink Cooling Ponds," (Reference 4). The attachment reviewed the LAKET-PC manual and source code and compared the LAKET-PC analysis approach to NUREG-0693.

The use of the Ryan and Lake Hefner wind functions was discussed in detail.

LAKET -PC calculates evaporation based on both natural and forced evaporation rates. The natural lake temperature is defined as the temperature of the lake reacting purely to natural influences (no additional heat added to the lake). The natural evaporation is calculated as the evaporation from the total surface area of the lake at its natural temperature. Section 2.4.1 of MIT Report No. 161 (Reference 2) discusses evaporation from a free (natural) water surface.

The MIT report notes that test data from several lakes (Lake Hefner, Lake Mead, and Lake Eucumene in Australia) confirms that the Lake Hefner evaporation wind function performed satisfactorily. Thus, LAKET -PC utilizes the Lake Hefner wind function when characterizing the natural evaporation.

Page 3 of 23

ATTACHMENT 1 Response to Request for Additional Information The Lake Hefner wind function is presented below:

F,H (w) = 17W (Reference 2)

FLH(W) = Lake Hefner wind function (BTU/ft2 day/mmHg)

W

= wind speed measured 2 meters above the water surface (mph)

Forced evaporation is defined in LAKET-PC as the increase over the natural evaporation caused by the influence of the plant. Only the portion of the lake deemed effective is used in calculating the forced evaporation.

When considering the additional heat rejected from the water, the wind function must account for forced convection at the water / air surface layer in addition to the wind alone. The MIT report (Reference 2) introduces the Ryan wind function, which is dependent on the wind speed, the atmospheric pressure, dry bulb air temperature, water surface temperature, and relative humidity of the air. Section 2.4.2.6 of MIT Report No.

161 (Reference 2) presents field performance data compared to the wind function equations and shows that the proposed Ryan wind function fits the data quite well. NUREG-0693 also presents the Ryan wind function as an alternative to the simplified Brady wind function. For these reasons, LAKET-PC utilizes the Ryan wind function for calculating the forced evaporation.

The explicit equation for the Ryan wind function is presented below:

where 1/3 FR(w)=22.4 Fr r

TS + 460 TA + 460 1 _ 0.378es 1 _ 0.378e, P

P

+14W (Reference 2) where FR(w)

= Ryan wind function (BTU/ft2 day/mmHg)

Ts

= water surface temperature (°F)

TA

= dry bulb air temperature (°F) es

= saturated vapor pressure at Ts (mmHg) ea

= partial vapor pressure at TA and relative humidity (mmHg)

P

= atmospheric pressure (mmHg)

W

= wind speed measured 2 meters above the water surface (mph)

Note that since the Lake Hefner model is applied to the entire lake, the forced evaporation term is calculated only in the effective area of the lake as the forced evaporation (per the Ryan wind function) minus the natural evaporation (per the Lake Hefner wind function). Thus, the forced evaporation value presented in the output of LAKET-PC is the increase over the natural evaporation caused by the influence of the plant.

When the calculated lake temperature approaches the natural lake temperature, LAKET-PC switches to the Lake Hefner wind function for the entire lake and conservatively ignores the forced evaporation term. A review of the code shows that the forced evaporation term is dropped and the natural wind function (Lake Hefner function) is used when the calculated lake temperature is within 2.5°F of the natural lake temperature. Although there is no explicit criterion for the switch from forced to natural evaporation, 2.5°F is conservative as any water Page 4 of 23 ATTACHMENT 1 Response to Request for Additional Information The Lake Hefner wind function is presented below:

(Reference 2) where FLH(W) = Lake Hefner wind function (BTU/ft2 day/mmHg)

W

= wind speed measured 2 meters above the water surface (mph)

Forced evaporation is defined in LAKET-PC as the increase over the natural evaporation caused by the influence of the plant. Only the portion of the lake deemed effective is used in calculating the forced evaporation. When considering the additional heat rejected from the water, the wind function must account for forced convection at the water I air surface layer in addition to the wind alone. The MIT report (Reference 2) introduces the Ryan wind function, which is dependent on the wind speed, the atmospheric pressure, dry bulb air temperature, water surface temperature, and relative humidity of the air. Section 2.4.2.6 of MIT Report No.

161 (Reference 2) presents field performance data compared to the wind function equations and shows that the proposed Ryan wind function fits the data quite well. NUREG-0693 also presents the Ryan wind function as an alternative to the simplified Brady wind function. For these reasons, LAKET-PC utilizes the Ryan wind function for calculating the forced evaporation.

The explicit equation for the Ryan wind function is presented below:

FR (w) = 22.4(( Ts + 460 ]_[ TA +460 ))/3 + 14W 1- 0.378es 1- 0.378ea p

p (Reference 2) where FR(w) = Ryan wind function (BTU/ft2 day/mmHg)

Ts

= water surface temperature (OF)

TA

= dry bulb air temperature (OF) es

= saturated vapor pressure at T s (mmHg) ea

= partial vapor pressure at T A and relative humidity (mmHg)

P

= atmospheric pressure (mmHg)

W

= wind speed measured 2 meters above the water surface (mph)

Note that since the Lake Hefner model is applied to the entire lake, the forced evaporation term is calculated only in the effective area of the lake as the forced evaporation (per the Ryan wind function) minus the natural evaporation (per the Lake Hefner.. wind function). Thus, the forced evaporation value presented in the output of LAKET-PC is the increase over the natural evaporation caused by the influence of the plant.

When the calculated lake temperature approaches the natural lake temperature, LAKET -PC switches to the Lake Hefner wind function for the entire lake and conservatively ignores the forced evaporation term. A review of the code shows that the forced evaporation term is dropped and the natural wind function (Lake Hefner function) is used when the calculated lake temperature is within 2.soF of the natural lake temperature. Although there is no explicit criterion for the switch from forced to natural evaporation, 2.soF is conservative as any water Page 4 of 23

ATTACHMENT 1 Response to Request for Additional Information temperature above the natural temperature will exhibit some forced evaporation. In neglecting the forced term for temperatures up to 2.5°F above the natural lake temperature, LAKET-PC is reducing the evaporative heat flux from the lake. This results in slightly higher calculated lake temperatures, which is conservative for the UHS analysis.

NRC Question 3:

Review of Weather Screening

Background:

The purpose of the LakeT-PC model analysis is to ensure that the temperature of the UHS during the design basis event will not result in the UHS exceeding the design limit for the cooling water supplied to the plant safety systems. Attachment 1 to the proposed license amendment request (LAR) states that the transit time of the plant accident energy through the UHS is approximately 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months . Section 4.0 of the proposed LAR describes the selection of the worst-case meteorological conditions for 1-day and 30-day periods.

Request: Justify the selection and use of a 24-hour worst-case meteorological period when analyzing a 30-hour transit time.

EGC Response to Question 3:

The response to Question 3 will be provided in a separate submittal.

NRC Question 4:

Background:

Attachment 3, L-002457 (L-002457), Revision 7, assumes a lake temperature and plant discharge of 100 OF for weather screening purposes. Attachment I, Figure 17.8, page 120, shows that during the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , the LSCS UHS pond temperature varies from approximately 140 OF to 101 OF (UHS inlet to UHS outlet).

Section M3.1, "Initial Lake Temperature," of Attachment M states:

"For the worst weather evaluation, the initial lake temperature is set at 100 OF. This is an arbitrary reference value for determining the relative weather severity and does not influence the results of this analysis."

Section M3.3, "Station Thermal Boundary Condition," of Attachment M states:

"The plant discharge water temperature when determining the worst-weather day and month is assumed to be 100°F. Since the lake is modeled as open cycle, the lake starts at this temperature at the start of each 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time interval. A constant initial temperature allows for isolation of the meteorological effects on the lake."

Page 5 of 23 ATTACHMENT 1 Response to Request for Additional Information temperature above the natural temperature will exhibit some forced evaporation. In neglecting the forced term for temperatures up to 2.5°F above the natural lake temperature, LAKET-PC is reducing the evaporative heat flux from the lake. This results in slightly higher calculated lake temperatures, which is conservative for the UHS analysis.

NRC Question 3:

Review of Weather Screening

Background:

The purpose of the LakeT-PC model analysis is to ensure that the temperature of the UHS during the design basis event will not result in the UHS exceeding the design limit for the cooling water supplied to the plant safety systems. Attachment 1 to the proposed license amendment request (LAR) states that the transit time of the plant accident energy through the UHS is approximately 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months . Section 4.0 of the proposed LAR describes the selection of the worst-case meteorological conditions for 1-day and 30-day periods.

Request: Justify the selection and use of a 24-hour worst-case meteorological period when analyzing a 30-hour transit time.

EGC Response to Question 3:

The response to Question 3 will be provided in a separate submittal.

NRC Question 4:

Background:

Attachment 3, L-002457 (L-002457), Revision 7, assumes a lake temperature and plant discharge of 100 OF for weather screening purposes. Attachment I, Figure 17.8, page 120, shows that during the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , the LSCS UHS pond temperature varies from approximately 140 OF to 101°F (UHS inlet to UHS outlet).

Section M3.1, "Initial Lake Temperature," of Attachment M states:

"For the worst weather evaluation, the initial lake temperature is set at 100 OF. This is an arbitrary reference value for determining the relative weather severity and does not influence the results of this analysis."

Section M3.3, "Station Thermal Boundary Condition," of Attachment M states:

"The plant discharge water temperature when determining the worst-weather day and month is assumed to be 100°F. Since the lake is modeled as open cycle, the lake starts at this temperature at the start of each 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months time interval. A constant initial temperature allows for isolation of the meteorological effects on the lake."

Page 5 of 23

ATTACHMENT 1 Response to Request for Additional Information Requests:

a.

Please justify how the current screening approach of assuming an initial lake temperature of 100 OF, as described in Sections M3.1 and M3.3, is appropriate for application to the LSCS UHS design given that the calculated lake inlet and outlet temperatures range from 101 OF to 140 OF during the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months after an accident. Also, please justify how the use of an initial lake temperature of 100°F identifies the worst meteorological conditions for the UHS critical time periods corresponding to minimum water cooling and the applicable conditions for maximum water evaporation.

b.

If a different set of meteorological conditions is identified as limiting as a result of revising the screening approach, please confirm that the resultant cooling water temperatures (using the revised meteorological conditions) remain bounded by the proposed TS limits.

EGC Response to Question 4a:

For determining the worst 24-hour and 30-day weather, a specific UHS model was created in LAKET-PC with a transit time corresponding to the three hour time step period. The model is an open cycle, which means water exiting the lake is discarded and new water enters the lake at predetermined conditions independent of the existing lake conditions. The UHS is set to the same initial temperature at the beginning of each three hour time step. Since initial conditions are the same for each time step, there are no residual effects due to the weather from the preceding time step. The UHS outlet temperature for each 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months period corresponds to the environmental effects on the UHS during these three hours. From these results, it can be implied that higher UHS outlet temperatures represent worse (hotter) weather conditions.

Calculation L-002457 (Reference 3) Section M3.1 corresponds to the LAKET-PC input of the initial lake temperature for the first time step in the weather file (in this case January 1, 1995).

L-002457 Section M3.3 corresponds to the LAKET-PC input of the plant discharge water temperature. Since the lake is modeled as an open cycle, this corresponds to the lake temperature at the start of a time step. A value of 100°F was chosen as the plant discharge water temperature for determining the worst weather conditions of the UHS since this temperature is approximately equal to the average lake temperature for the 30 days following an accident of 102.1 OF.

Table 1 of Reference 3 Attachment 1 describes the heat load equations used in the LAKET-PC program. The net heat transfer to the UHS is:

Q=QSN+QAN-QBR-QE-QC+QRJ where:

QSN = net incident short wave solar radiation QAN = net incident long wave atmospheric radiation QBR = net rate of long wave back radiation from the lake surface QE = net rate of heat loss due to evaporation Qc = net rate of heat loss due to conduction and convection QRJ = net rate of heat rejected to the lake by the plant Page 6 of 23 ATTACHMENT 1 Response to Request for Additional Information Requests:

a. Please justify how the current screening approach of assuming an initial lake temperature of 100 of, as described in Sections M3.1 and M3.3, is appropriate for application to the LSCS UHS design given that the calculated lake inlet and outlet temperatures range from 101°F to 140 of during the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months after an accident. Also, please justify how the use of an initial lake temperature of 100°F identifies the worst meteorological conditions for the UHS critical time periods corresponding to minimum water cooling and the applicable conditions for maximum water evaporation.

b. If a different set of meteorological conditions is identified as limiting as a result of revising the screening approach, please confirm that the resultant cooling water temperatures (using the revised meteorological conditions) remain bounded by the proposed TS limits.

EGC Response to Question 4a:

For determining the worst 24-hour and 30-day weather, a specific UHS model was created in LAKET-PC with a transit time corresponding to the three hour time step period. The model is an open cycle, which means water exiting the lake is discarded and new water enters the lake at predetermined conditions independent of the existing lake conditions. The UHS is set to the same initial temperature at the beginning of each three hour time step. Since initial conditions are the same for each time step, there are no residual effects due to the weather from the preceding time step. The UHS outlet temperature for each 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months period corresponds to the environmental effects on the UHS during these three hours. From these results, it can be implied that higher UHS outlet temperatures represent worse (hotter) weather conditions.

Calculation L-002457 (Reference 3) Section M3.1 corresponds to the LAKET-PC input of the initial lake temperature for the first time step in the weather file (in this case January 1, 1995).

L-002457 Section M3.3 corresponds to the LAKET-PC input of the plant discharge water temperature. Since the lake is modeled as an open cycle, this corresponds to the lake temperature at the start of a time step. A value of 100°F was chosen as the plant discharge water temperature for determining the worst weather conditions of the UHS since this temperature is approximately equal to the average lake temperature for the 30 days following an accident of 102.1 OF.

Table 1 of Reference 3 Attachment 1 describes the heat load equations used in the LAKET-PC program. The net heat transfer to the UHS is:

where:

Q SN = net incident short wave solar radiation QAN = net incident long wave atmospheric radiation QSR = net rate of long wave back radiation from the lake surface QE = net rate of heat loss due to evaporation Qc = net rate of heat loss due to conduction and convection QRJ = net rate of heat rejected to the lake by the plant Page 6 of 23

ATTACHMENT 1 Response to Request for Additional Information The terms of this equation that are affected by the assumed initial UHS temperature during environmental (weather) screening are QBR, QE, and Qc. These terms determine the amount of energy rejected to the environment by the UHS. The environmental impacts on these terms are wind speed, dry-bulb temperature, and relative humidity. The back radiation term is increased as the UHS water temperature is increased. The evaporation and conduction/convection terms are increased as the difference between the UHS water temperature and the dry-bulb temperature/relative humidity is increased. The screening process evaluates the UHS model for each three-hour period as described in Attachment M of L-002457. The environmental conditions that would be evaluated as limiting (worst 24-hour or 30-day period) would be those that maximize the net heat transfer to the UHS water - create the maximum Q in the above equation. In order to maximize the net heat transfer to the UHS, QBR, QE, and Qc must be minimized. For a given UHS water temperature, the environmental conditions with the highest dry-bulb temperature, the highest relative humidity, and the lowest wind speed would minimize the terms QBR, QE, and Qc. The same environmental conditions would also minimize these terms when an initial UHS temperature of 110°F or 120°F is assumed. Therefore, the use of 100°F as the initial UHS water temperature is acceptable to screen environmental data.

EGC Response to Question 4b:

Because a different set of meteorological conditions was not identified during review of the screening approach, the resulting cooling water temperatures remain bounded by the proposed technical specification limits.

NRC Question 5:

Review of UHS Transient Heatup

Background:

The licensee has stated that the transit time for core standby cooling system (CSCS) flow across the UHS pond during a design-basis accident loss-of-coolant accident (DBA-LOCA) is 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months with the UHS sediment level of 1.5 feet. In the DBA-LOCA analysis, the licensee considered the worst 24-hour period of meteorological conditions for controlling parameters in determining peak UHS temperature. By considering the worst 24-hour period, the licensee's analysis showed that the peak temperature of the UHS after a LOCA, which started at 6:00 a.m., would be approximately 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months after the LOCA, which occurs 18 hours2.083333e-4 days 0.005 hours 2.97619e-5 weeks 6.849e-6 months before any of the UHS water that is affected by accident heat input enters the plant intake.

Attachments I [Figure 17.7] and L [Appendix L9.4] of Calculation L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," show the effects of the heat added to the UHS by the DBA-LOCA, whose effects do not reach the UHS outlet to the plant until 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months after the DBA -

LOCA. Figure 17.7 shows temperatures near 140 OF initially entering the UHS immediately after the DBA and shows the UHS inlet temperature to be well above 120 OF for most of the first day after the DBA-LOCA, yet, the UHS outlet to the plant has already peaked at 107 OF at about 3:00 p.m. on the first day. According to Figure 4 of the LAR, the maximum temperature of the UHS outlet temperature on the second day is below the maximum temperature on the first day, indicating that the heat added by the DBA-LOCA has little effect on the UHS outlet temperature.

The seeming lack of influence upon peak UHS temperature by the accident heat and the meteorological conditions of second day after the accident could be attributed to a relatively cool, cloudy, or windy day after the first day following the DBA-LOCA, which is the first day of the 30-day critical period.

Page 7 of 23 ATIACHMENT1 Response to Request for Additional Information The terms of this equation that are affected by the assumed initial UHS temperature during environmental (weather) screening are OBR, QE, and Oc. These terms determine the amount of energy rejected to the environment by the UHS. The environmental impacts on these terms are wind speed, dry-bulb temperature, and relative humidity. The back radiation term is increased as the UHS water temperature is increased. The evaporation and conduction/convection terms are increased as the difference between the UHS water temperature and the dry-bulb temperaturelrelative humidity is increased. The screening process evaluates the UHS model for each three-hour period as described in Attachment M of L-002457. The environmental conditions that would be evaluated as limiting (worst 24-hour or 30-day period) would be those that maximize the net heat transfer to the UHS water - create the maximum 0 in the above equation. In order to maximize the net heat transfer to the UHS, OBR, OE, and Oc must be minimized. For a given UHS water temperature, the environmental conditions with the highest dry-bulb temperature, the highest relative humidity, and the lowest wind speed would minimize the terms OBR, OE, and Oc. The same environmental conditions would also minimize these terms when an initial UHS temperature of 110°F or 120°F is assumed. Therefore, the use of 100°F as the initial UHS water temperature is acceptable to screen environmental data.

EGC Response to Question 4b:

Because a different set of meteorological conditions was not identified during review of the screening approach, the resulting cooling water temperatures remain bounded by the proposed technical specification limits.

NRC Question 5:

Review of UHS Transient Heatup

Background:

The licensee has stated that the transit time for core standby cooling system (CSCS) flow across the UHS pond during a design-basis accident loss-of-coolant accident (DBA-LOCA) is 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months with the UHS sediment level of 1.5 feet. In the DBA-LOCA analysis, the licensee considered the worst 24-hour period of meteorological conditions for controlling parameters in determining peak UHS temperature. By considering the worst 24-hour period, the licensee's analysis showed that the peak temperature of the UHS after a LOCA, which started at 6:00 a.m., would be approximately 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months after the LOCA, which occurs 18 hours2.083333e-4 days 0.005 hours 2.97619e-5 weeks 6.849e-6 months before any of the UHS water that is affected by accident heat input enters the plant intake.

Attachments I [Figure 17.7] and L [Appendix L9.4] of Calculation L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," show the effects of the heat added to the UHS by the DBA-LOCA, whose effects do not reach the UHS outlet to the plant until 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months after the DBA-LOCA. Figure 17.7 shows temperatures near 140 OF initially entering the UHS immediately after the DBA and shows the UHS inlet temperature to be well above 120 OF for most of the first day after the DBA-LOCA, yet, the UHS outlet to the plant has already peaked at 107 OF at about 3:00 p.m. on the first day. According to Figure 4 of the LAR, the maximum temperature of the UHS outlet temperature on the second day is below the maximum temperature on the first day, indicating that the heat added by the DBA-LOCA has little effect on the UHS outlet temperature.

The seeming lack of influence upon peak UHS temperature by the accident heat and the meteorological conditions of second day after the accident could be attributed to a relatively cool, cloudy, or windy day after the first day following the DBA-LOCA, which is the first day of the 30-day critical period.

Page 7 of 23

ATTACHMENT 1 Response to Request for Additional Information Issues: Heat waves where weather extremes have persisted for multiple consecutive days are not uncommon. Considering that a heat wave is in progress and the first critical time period of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months as used by the licensee, the first day of the worst 30-day period may not be representative of the actual second day after an accident. Also, in a letter dated May 6, 2011, the licensee stated that high temperatures and humidity during the daytime, in conjunction with minimal cooling at night and little precipitation during the summer months, results in elevated water temperatures in the LSCS UHS.

The NRC staff is not certain that the licensee has chosen appropriate critical time periods unique to the specific design of the CSCS pond. According to Regulatory Position 1 of Regulatory Guide (RG) 1.27, the meteorological conditions resulting in minimum water cooling should be the worst combination of controlling parameters, including diurnal variations where appropriate, for the critical time period(s) unique to the specific design of the sink," and "sufficient conservatism should be provided to ensure that a 30-day cooling supply is available and that design basis temperatures of safety related equipment are not exceeded." In RG 1.27 it also states that "meteorological conditions considered in the design of the UHS should be selected with respect to the controlling parameters (i.e., wind speed, humidity, dew point, air temperature, solar radiation, etc.)."

The licensee selected a first critical time period of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , independent of the time of the accident and the UHS transit time. However, the NRC staff believes that the first critical time period would be 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months or greater, dependent upon time of accident initiation and UHS transit time. Using these variable and first critical time periods would yield more limiting and accurate results. The staff also believes that the first critical time period should be verified by assuming greater first critical time periods and performing the analysis and comparing results. The staff also believes that the analysis for each assumed accident start time, i.e., 6:00 a.m. - 9 a.m.,

etc., would have its own set of worst-weather data for its particular critical time period.

Requests:

a.

The NRC staff requests that the licensee justify their selection of weather data and critical time periods or propose new analysis that would address the NRC staff concerns presented in Issues above.

b. Justify the constant transit time across the UHS pond that is used in your analysis, since reduction in UHS volume over the 30-day recovery period would cause transit time to decrease. If the decrease in transit time is modeled, justify whether the effective UHS volumes, surfaces, and transit times predicted in Attachment J remain applicable.

EGC Response to Question 5:

The response to Question 5 will be provided in a separate submittal.

Page 8 of 23 ATTACHMENT 1 Response to Request for Additional Information Issues: Heat waves where weather extremes have persisted for multiple consecutive days are not uncommon. Considering that a heat wave is in progress and the first critical time period of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months as used by the licensee, the first day of the worst 30-day period may not be representative of the actual second day after an accident. Also, in a letter dated May 6, 2011, the licensee stated that high temperatures and humidity during the daytime, in conjunction with minimal cooling at night and little precipitation during the summer months, results in elevated water temperatures in the LSCS UHS.

The NRC staff is not certain that the licensee has chosen appropriate critical time periods unique to the specific design of the CSCS pond. According to Regulatory Position 1 of Regulatory Guide (RG) 1.27, "the meteorological conditions resulting in minimum water cooling should be the worst combination of controlling parameters, including diurnal variations where appropriate, for the critical time period(s} unique to the specific design of the sink," and "sufficient conservatism should be provided to ensure that a 30-day cooling supply is available and that design basis temperatures of safety related equipment are not exceeded." In RG 1.27 it also states that "meteorological conditions considered in the design of the UHS should be selected with respect to the controlling parameters (i.e., wind speed, humidity, dew point, air temperature, solar radiation, etc.}."

The licensee selected a first critical time period of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , independent of the time of the accident and the UHS transit time. However, the NRC staff believes that the first critical time period would be 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months or greater, dependent upon time of accident initiation and UHS transit time. Using these variable and first critical time periods would yield more limiting and accurate results. The staff also believes that the first critical time period should be verified by assuming greater first critical time periods and performing the analysiS and comparing results. The staff also believes that the analYSis for each assumed accident start time, i.e., 6:00 a.m. - 9 a.m.,

etc., would have its own set of worst-weather data for its particular critical time period.

Requests:

a. The NRC staff requests that the licensee justify their selection of weather data and critical time periods or propose new analysis that would address the NRC staff concerns presented in Issues above.

b. Justify the constant transit time across the UHS pond that is used in your analysis, since reduction in UHS volume over the 30-day recovery period would cause transit time to decrease. If the decrease in transit time is modeled, justify whether the effective UHS volumes, surfaces, and transit times predicted in Attachment J remain applicable.

EGC Response to Question 5:

The response to Question 5 will be provided in a separate submittal.

Page 8 of 23

ATTACHMENT 1 Response to Request for Additional Information NRC Question 6:

Background:

In the licensee's LAR submittal dated July 12, 2012, it states that, "The current TS temperature limit does not reflect the diurnal effect that weather conditions have upon the allowable UHS temperature. Since the UHS heats up during the day and cools off during the night, the allowable UHS temperature is dependent upon the time of day when the design basis event occurs."

Therefore, the licensee has proposed new TS temperature limits as shown in Figure 3.7.3, based on diurnal variations. Figures 4, 5, and 6, of the LAR show the calculated effects of the diurnal cycle and, particularly, the first 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months show the cycle before any heat from the postulated accident has an effect.

Issue: Although the diurnal effects of the weather on the temperature of the cooling water supplied to the plant from the CSCS pond, when the cooling lake is intact, would not be identical to the diurnal effects on the CSCS pond during a DBA, the licensee did not provide actual plant data that shows that diurnal variation would exist at LSCS.

Request: The NRC staff requests the following plant data - recordings of cooling water temperature supplied to the plant from the CSCS pond (from the same source that is used for Surveillance Requirement (SR) 3.7.3.1) every hour on the hour for every day in June, July, and August for 2012. For every recording also include reactor power for both units and ambient temperature. If available, also provide a measure of humidity with each recording (i.e., relative humidity, or dew point, or wet bulb temperature).

EGC Response to Question 6:

The data sets provided consist of onsite measured ambient temperature and windspeed, cooling water temperature used to meet SR 3.7.3.1 (average of both Units), and instantaneous core thermal power (CTP) data on an hourly basis for LSCS Units 1 and 2 for June, July, and August of 2012. The data sets are contained in Attachment 3. On site data for relative humidity, dew point, and wet bulb temperature are not available.

NRC Question 7:

Review of LaSalle Design Basis Capabilities

Background:

The actual equipment temperature limit of the UHS was originally 100 OF. By reducing margin, the licensee subsequently increased the actual equipment temperature limit to 104 OF. The original design fouling factor for the residual heat removal (RHR) heat exchangers is 0.0025. The original design fouling factor for the diesel generators (DG) coolers is 0.00285.

In the proposed LAR, the licensee has proposed new UHS TS limits which are based on an allowable actual equipment temperature limit of 107 OF. Attachment 5 of the LAR shows the licensee's calculated heat transfer capabilities of the heat exchangers cooled by CSCS at 107 OF.

Page 9of23 ATTACHMENT 1 Response to Request for Additional Information NRC Question 6:

Background:

In the licensee's LAR submittal dated July 12, 2012, it states that, "The current TS temperature limit does not reflect the diurnal effect that weather conditions have upon the allowable UHS temperature. Since the UHS heats up during the day and cools off during the night, the allowable UHS temperature is dependent upon the time of day when the design basis event occurs."

Therefore, the licensee has proposed new TS temperature limits as shown in Figure 3.7.3, based on diurnal variations. Figures 4, 5, and 6, of the LAR show the calculated effects of the diurnal cycle and, particularly, the first 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months show the cycle before any heat from the postulated accident has an effect.

Issue: Although the diurnal effects of the weather on the temperature of the cooling water supplied to the plant from the eses pond, when the cooling lake is intact, would not be identical to the diurnal effects on the eses pond during a DBA, the licensee did not provide actual plant data that shows that diurnal variation would exist at LSeS.

Request: The NRC staff requests the following plant data - recordings of cooling water temperature supplied to the plant from the eses pond (from the same source that is used for Surveillance Requirement (SR) 3.7.3.1) every hour on the hour for every day in June, July, and August for 2012. For every recording also include reactor power for both units and ambient temperature. If available, also provide a measure of humidity with each recording (Le., relative humidity, or dew point, or wet bulb temperature).

EGC Response to Question 6:

The data sets provided consist of onsite measured ambient temperature and windspeed, cooling water temperature used to meet SR 3.7.3.1 (average of both Units), and instantaneous core thermal power (eTP) data on an hourly basis for LSeS Units 1 and 2 for June, July, and August of 2012. The data sets are contained in Attachment 3. On site data for relative humidity, dew point, and wet bulb temperature are not available.

NRC Question 7:

Review of LaSalle Design Basis Capabilities

Background:

The actual equipment temperature limit of the UHS was originally 100 of. By reducing margin, the licensee subsequently increased the actual equipment temperature limit to 104 of. The original design fouling factor for the residual heat removal (RHR) heat exchangers is 0.0025. The original design fouling factor for the diesel generators (DG) coolers is 0.00285.

In the proposed LAR, the licensee has proposed new UHS TS limits which are based on an allowable actual equipment temperature limit of 107 OF. Attachment 5 of the LAR shows the licensee's calculated heat transfer capabilities of the heat exchangers cooled by eses at 107 OF.

Page 9 of 23

ATTACHMENT 1 Response to Request for Additional Information Issues: The licensee used a design fouling factor of 0.00147 in order to qualify RHR heat exchanger (HX) for the design heat removal rate at 107 OF. Attachment 5 shows the required heat transfer rate of 165,564,000 Btu/hr for the DBA-LOCA. The calculated rate using a fouling factor of.00147 and cooling water at 107 OF is 166,468,480 BTU/hr, which provides a small heat transfer margin of 0.55 percent. The licensee states that the Generic Letter (GL) 89-13 testing verifies a lower fouling factor while using a 107 OF UHS temperature.

The licensee is using a design fouling factor of 0.0022 in order to qualify DG coolers for the design heat removal rate at 107 OF. Attachment 5 shows a heat transfer margin of 1.5 percent.

The licensee states that the GL 89-13 testing verifies a lower fouling factor while using 107 OF UHS temperature.

Requests:

a.

Describe the GL 89-13 testing for the RHR HXs and discuss the accuracy of the testing with respect to design conditions. With a low heat transfer margin for the RHR HXs, please justify your reliance of GL 89-13 testing as a means of assuring that the required heat transfer capability of the RHR heat exchangers is maintained.

b.

Describe the GL 89-13 testing for the DG coolers and discuss the accuracy of the testing with respect to design conditions. With a low heat transfer margin for the DG coolers, please justify your reliance of GL 89-13 testing as a means of assuring that the required heat transfer capability of the DG coolers is maintained.

EGC Response to Question 7a:

GL 89-13 testing of the RHR HXs is completed in accordance with the LSCS Generic Letter 89-13, "Service Water System Problems Affecting Safety-Related Equipment," program, which utilizes the guidelines for the heat transfer test method established in EPRI Technical Report TR-107397 (Reference 6), Section 2.2. This test method allows testing at conditions far removed from limiting (design) conditions and is highly reliable. The testing apparatus includes multiple precision resistance temperature detectors (RTDs) evenly spaced around the circumference of the piping. The RTDs are installed with thermal paste and are also insulated during the test to minimize the effects of the surrounding environment.

The RHR HXs are tested in the safety related containment cooling mode of the RHR system.

To complete the test, suppression pool water is pumped via the RHR system pumps through the shell side of the RHR HX while cooling water is pumped via the RHR Service Water System pumps through the tube side of the RHR HX. By procedure, test conditions are set to ensure sufficient heat load and proper flow conditions occur during the test. Fluid temperature stability is verified for a requisite amount of time prior to the commencement of the test. Process water and cooling water flow rates and temperatures are then recorded for a period of 30 minutes.

This test data is averaged and input to commercially available software (Proto-HX) that uses a heat exchanger model that has been benchmarked to the heat exchanger data sheet. The heat transfer capability and fouling factor of the heat exchanger is determined at the user input test conditions. Once this is complete, the same software then extrapolates the heat transfer capability of the heat exchanger utilizing user specified design conditions and standard heat transfer equations. The design conditions consist of the minimum required cooling water and Page 10 of 23 ATTACHMENT 1 Response to Request for Additional Information Issues: The licensee used a design fouling factor of 0.00147 in order to qualify RHR heat exchanger (HX) for the design heat removal rate at 107 of. Attachment 5 shows the required heat transfer rate of 165,564,000 Btu/hr for the DBA-LOCA. The calculated rate using a fouling factor of.00147 and cooling water at 107 of is 166,468,480 BTU/hr, which provides a small heat transfer margin of 0.55 percent. The licensee states that the Generic Letter (GL) 89-13 testing verifies a lower fouling factor while using a 107 OF UHS temperature.

The licensee is using a design fouling factor of 0.0022 in order to qualify DG coolers for the design heat removal rate at 107 OF. Attachment 5 shows a heat transfer margin of 1.5 percent.

The licensee states that the GL 89-13 testing verifies a lower fouling factor while using 107 OF UHS temperature.

Requests:

a. Describe the G L 89-13 testing for the RH R HXs and discuss the accuracy of the testing with respect to design conditions. With a low heat transfer margin for the RHR HXs, please justify your reliance of GL 89-13 testing as a means of assuring that the required heat transfer capability of the RHR heat exchangers is maintained.

b. Describe the G L 89-13 testing for the DG coolers and discuss the accuracy of the testing with respect to design conditions. With a low heat transfer margin for the DG coolers, please justify your reliance of GL 89-13 testing as a means of assuring that the required heat transfer capability of the DG coolers is maintained.

EGC Response to Question 7a:

GL 89-13 testing of the RHR HXs is completed in accordance with the LSCS Generic Letter 89-13, "Service Water System Problems Affecting Safety-Related Equipment," program, which utilizes the guidelines for the heat transfer test method established in EPRI Technical Report TR-107397 (Reference 6), Section 2.2. This test method allows testing at conditions far removed from limiting (design) conditions and is highly reliable. The testing apparatus includes multiple precision resistance temperature detectors (RTDs) evenly spaced around the circumference of the piping. The RTDs are installed with thermal paste and are also insulated during the test to minimize the effects of the surrounding environment.

The RHR HXs are tested in the safety related containment cooling mode of the RHR system.

To complete the test, suppression pool water is pumped via the RHR system pumps through the shell side of the RHR HX while cooling water is pumped via the RHR Service Water System pumps through the tube side of the RHR HX. By procedure, test conditions are set to ensure sufficient heat load and proper flow conditions occur during the test. Fluid temperature stability is verified for a requisite amount of time prior to the commencement of the test. Process water and cooling water flow rates and temperatures are then recorded for a period of 30 minutes.

This test data is averaged and input to commercially available software (Proto-HX) that uses a heat exchanger model that has been bench marked to the heat exchanger data sheet. The heat transfer capability and fouling factor of the heat exchanger is determined at the user input test conditions. Once this is complete, the same software then extrapolates the heat transfer capability of the heat exchanger utilizing user specified design conditions and standard heat transfer equations. The design conditions consist of the minimum required cooling water and Page 10 of 23

ATTACHMENT 1 Response to Request for Additional Information process water flow rates and the maximum cooling water and process water temperatures.

Instrument uncertainties for flow and temperature measuring instruments are also input by the user.

Per EPRI document TR-107397, factors such as spatial bias are taken into account to statistically determine the uncertainty in the test results. The results previously reported in, Table A5-1 of the original submittal were the worst case heat transfer and worst case fouling factor when considering the worst case test uncertainty. Taking into account this worst case scenario, the GL 89-13 testing accurately predicts the performance of the RHR heat exchangers during design conditions. Additionally, the most recent worst case results for the GL 89-13 tests of the RHR HXs show approximately 10-19% thermal margin at design conditions.

EGC Response to Question 7b:

GL 89-13 testing of the DG jacket water coolers is completed in accordance with the LSCS Generic Letter 89-13, "Service Water System Problems Affecting Safety-Related Equipment,"

program, which utilizes the guidelines for the heat transfer test method established in EPRI document TR-107397, Section 2.2. This test method allows testing at conditions far removed from limiting (design) conditions and is highly reliable. The testing apparatus includes multiple precision RTDs evenly spaced around the circumference of the piping. The RTDs are installed with thermal paste and are also insulated during the test to minimize the effects of the surrounding environment. To complete the test, the Diesel Generator is started and fully loaded in accordance with station procedures. The jacket water is pumped via the jacket water pump through the shell side of the DG jacket water cooler while cooling water is pumped via the DG Cooling Water System pump through the tube side of the DG jacket water cooler. By procedure, test conditions are set to ensure sufficient heat load and proper flow conditions occur during the test. Fluid temperature stability is verified for a requisite amount of time prior to the commencement of the test. Process water and cooling water flow rates and temperatures are then recorded for a period of 30 minutes.

This test data is averaged and input to commercially available software (Proto-HX) that uses a heat exchanger model that has been benchmarked to the heat exchanger data sheet. The heat transfer capability and fouling factor of the heat exchanger is determined at the user input test conditions. Once this is complete, the same software then extrapolates the heat transfer capability of the heat exchanger utilizing user specified design conditions and standard heat transfer equations. The design conditions consist of the minimum required cooling water and process water flow rates and the maximum cooling water and process water temperatures.

Instrument uncertainties for flow and temperature measuring instruments are also input by the user.

Instrument uncertainty is taken into account to determine the uncertainty in the test results. The results previously reported in Attachment 5, Table A5-1 of the original submittal were the worst case heat transfer and worst case fouling factor when considering the worst case instrument uncertainty. Taking into account this worst case scenario, the GL 89-13 testing accurately predicts the performance of the DG coolers during design conditions. Additionally, the most recent worst case results for the GL 89-13 tests of the DG jacket water coolers show approximately 37-78% thermal margin at design conditions.

Page 11 of 23 ATTACHMENT 1 Response to Request for Additional Information process water flow rates and the maximum cooling water and process water temperatures.

Instrument uncertainties for flow and temperature measuring instruments are also input by the user.

Per EPRI document TR-107397, factors such as spatial bias are taken into account to statistically determine the uncertainty in the test results. The results previously reported in, Table A5-1 of the original submittal were the worst case heat transfer and worst case fouling factor when considering the worst case test uncertainty. Taking into account this worst case scenario, the GL 89-13 testing accurately predicts the performance of the RHR heat exchangers during design conditions. Additionally, the most recent worst case results for the GL 89-13 tests of the RHR HXs show approximately 10-19% thermal margin at design conditions.

EGC Response to Question 7b:

GL 89-13 testing of the DG jacket water coolers is completed in accordance with the LSCS Generic Letter 89-13, "Service Water System Problems Affecting Safety-Related Equipment,"

program, which utilizes the guidelines for the heat transfer test method established in EPRI document TR-107397, Section 2.2. This test method allows testing at conditions far removed from limiting (design) conditions and is highly reliable. The testing apparatus includes multiple precision RTDs evenly spaced around the circumference of the piping. The RTDs are installed with thermal paste and are also insulated during the test to minimize the effects of the surrounding environment. To complete the test, the Diesel Generator is started and fully loaded in accordance with station procedures. The jacket water is pumped via the jacket water pump through the shell side of the DG jacket water cooler while cooling water is pumped via the DG Cooling Water System pump through the tube side of the DG jacket water cooler. By procedure, test conditions are set to ensure sufficient heat load and proper flow conditions occur during the test. Fluid temperature stability is verified for a requisite amount of time prior to the commencement of the test. Process water and cooling water flow rates and temperatures are then recorded for a period of 30 minutes.

This test data is averaged and input to commercially available software (Proto-HX) that uses a heat exchanger model that has been benchmarked to the heat exchanger data sheet. The heat transfer capability and fouling factor of the heat exchanger is determined at the user input test conditions. Once this is complete, the same software then extrapolates the heat transfer capability of the heat exchanger utilizing user specified design conditions and standard heat transfer equations. The design conditions consist of the minimum required cooling water and process water flow rates and the maximum cooling water and process water temperatures.

Instrument uncertainties for flow and temperature measuring instruments are also input by the user.

Instrument uncertainty is taken into account to determine the uncertainty in the test results. The results previously reported in Attachment 5, Table A5-1 of the original submittal were the worst case heat transfer and worst case fouling factor when considering the worst case instrument uncertainty. Taking into account this worst case scenario, the GL 89-13 testing accurately predicts the performance of the DG coolers during design conditions. Additionally, the most recent worst case results for the GL 89-13 tests of the DG jacket water coolers show approximately 37-78% thermal margin at design conditions.

Page 11 of 23

ATTACHMENT 1 Response to Request for Additional Information NRC Question 8:

Background:

The updated safety analysis report (UFSAR), Section 6.5.1.1.1, states that the standby gas treatment system (SGTS) is designed to automatically start in response to any one of the following signals: (1) high pressure in Unit 1 or Unit 2 drywell, (2) low-water level in Unit 1 or Unit 2 reactor, (3) high radiation in exhaust air from over the fuel handling pools in the reactor building for either Unit 1 or Unit 2, (4) high radiation in the ventilation exhaust plenum for reactor building for either Unit 1 or Unit 2, and (5) manual activation from the main control room.

Issue: The UHS model does not consider heat removal from the spent fuel pool (SFP) during abnormal events. No heat removal is modeled for SFP cooling through the available safety-related RHR system lineup. Safety-related makeup water is provided to maintain pool level during such events. Consider abnormal events listed above when the reactor building ventilation system is isolated with automatic start of SGTS, coincident with no heat removal from the SFP, and, therefore is allowed to boil, which takes place within a few hours (UFSAR Table 9.1-6).

Requests:

a.

Please provide the results of evaluation of the capability of the operation SGTS during these events. Discuss whether the SGTS can meet its design basis functions for the entire 30-day period, e.g., draw down and maintain negative pressure of 0.25-inch water gage in the secondary containment, capture of radioactive gases and particles leaking from primary containment after a LOCA, limiting incoming saturated air-steam mixtures to less than 150 OF, and prevention of charcoal desorption.

b.

Please confirm whether the safety-related RHR system lineup for SFP cooling is available following a loss of off site power (LOOP) and/or seismic event. As appropriate, discuss whether the safety-related RHR alignment for SFP cooling can be accomplished for both units under design basis conditions (as LSCS Units 1 and 2 share a common reactor building floor).

EGC Response to Question 8a:

As stated in RG 1.27, Revision 1, the UHS should be able to dissipate the heat from an accident in one unit and to permit the concurrent safe shutdown and cooldown of the remaining unit. The total decay heat transmitted to the UHS from the plant includes the reactor decay heat and the fuel pool decay from each unit. If the reactor decay heat is maximized, then the fuel pool decay heat would not include any recent refuel decay heat - it would be the normal decay heat in the pools with available margin for batch offloads. Conversely, if the fuel pool decay heat is maximized by assuming recent batch off loads, then the reactor decay heat would be reduced by the new fuel batch load. The LSCS UHS heat load model assumes the maximum reactor decay heat load. In addition, the LSCS model assumes the fuel pool decay heat load is dissipated by pool boiling while maintaining fuel pool level with the fuel pool emergency makeup systems instead of transmitting the energy to the UHS through pool cooling.

It is not the intent of this model to alter the LSCS existing fuel pool design or licensing bases.

The model assumes maximum reactor decay heat while removing a very conservative amount of UHS volume to provide for fuel pool makeup. The assumed makeup is 300 gpm for each Page 12 of 23 ATTACHMENT 1 Response to Request for Additional Information NRC Question 8:

Background:

The updated safety analysis report (UFSAR), Section 6.5.1.1.1, states that the standby gas treatment system (SGTS) is designed to automatically start in response to anyone of the following signals: (1) high pressure in Unit 1 or Unit 2 drywell, (2) low-water level in Unit 1 or Unit 2 reactor, (3) high radiation in exhaust air from over the fuel handling pools in the reactor building for either Unit 1 or Unit 2, (4) high radiation in the ventilation exhaust plenum for reactor building for either Unit 1 or Unit 2, and (5) manual activation from the main control room.

Issue: The UHS model does not consider heat removal from the spent fuel pool (SFP) during abnormal events. No heat removal is modeled for SFP cooling through the available safety-related RHR system lineup. Safety-related makeup water is provided to maintain pool level during such events. Consider abnormal events listed above when the reactor building ventilation system is isolated with automatic start of SGTS, coincident with no heat removal from the SFP, and, therefore is allowed to boil, which takes place within a few hours (UFSAR Table 9.1-6).

Requests:

a. Please provide the results of evaluation of the capability of the operation SGTS during these events. Discuss whether the SGTS can meet its design basis functions for the entire 30-day period, e.g., draw down and maintain negative pressure of 0.25-inch water gage in the secondary containment, capture of radioactive gases and particles leaking from primary containment after a LOCA, limiting incoming saturated air-steam mixtures to less than 150 OF, and prevention of charcoal desorption.

b. Please confirm whether the safety-related RHR system lineup for SFP cooling is available following a loss of off site power (LOOP) and/or seismic event. As appropriate, discuss whether the safety-related RHR alignment for SFP cooling can be accomplished for both units under design basis conditions (as LSCS Units 1 and 2 share a common reactor building floor).

EGC Response to Question 8a:

As stated in RG 1.27, Revision 1, the UHS should be able to dissipate the heat from an accident in one unit and to permit the concurrent safe shutdown and cooldown of the remaining unit. The total decay heat transmitted to the UHS from the plant includes the reactor decay heat and the fuel pool decay from each unit. If the reactor decay heat is maximized, then the fuel pool decay heat would not include any recent refuel decay heat - it would be the normal decay heat in the pools with available margin for batch offloads. Conversely, if the fuel pool decay heat is maximized by assuming recent batch offloads, then the reactor decay heat would be reduced by the new fuel batch load. The LSCS UHS heat load model assumes the maximum reactor decay heat load. In addition, the LSCS model assumes the fuel pool decay heat load is dissipated by pool boiling while maintaining fuel pool level with the fuel pool emergency makeup systems instead of transmitting the energy to the UHS through pool cooling.

It is not the intent of this model to alter the LSCS existing fuel pool design or licensing bases.

The model assumes maximum reactor decay heat while removing a very conservative amount of UHS volume to provide for fuel pool makeup. The assumed makeup is 300 gpm for each Page 12 of 23

ATTACHMENT 1 Response to Request for Additional Information pool (600 gpm total) running continuously for the entire 31 day period while the actual amount of pool water loss due to boiling would be a small fraction of such. The purpose of assuming fuel pool makeup was to reduce the UHS inventory available for accident heat rejection. The fuel pool decay heat for the LSCS model would be approximately 6E6 Btu/hr for each pool (Reference 9). Over a 48 hour5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months period of interest, the integrated fuel pool decay heat represents approximately 4.0% of the total integrated UHS heat load. Over this same period of interest, the UHS volume would be reduced by over 1.5% due to the loss of inventory from the assumed fuel pool makeup. It is EGC's conclusion that the impact of adding the fuel pool decay heat load to the UHS and eliminating fuel pool makeup, i.e, assuming the fuel pools remain cooled and do not boil, would have an insignificant effect on the limiting initial UHS temperature profile of TS Figure 3.7.3-1.

The response of the SGTS to the UHS design event including the DBA LOCA with concurrent loss of offsite power remains unchanged as a result of this proposed license amendment. The ability of LSCS to maintain fuel pool cooling or to provide makeup to the fuel pools was a part of the LSCS original design and is unaffected by the proposed UHS temperature limit change.

The LSCS UHS model evaluates a limiting condition of accident heat load and UHS inventory loss and does not alter the design or licensing bases of the LSCS response to postulated accidents.

EGC Response to Question 8b:

The RHR system, including all piping to and from the spent fuel pool, is independent of the spent fuel pool cooling system and is seismic Category I. The safety related RHR system is powered by the Division 2 onsite emergency diesel generator. Therefore, the safety related RHR system lineup for SFP cooling is available following a LOOP or seismic event.

The NRC has reviewed the design of the LSCS spent fuel pools (SFPs) and the fuel pool cooling system several times over the life of the plant. Brief descriptions and excerpts are provided from several of the NRC reviews and licensing correspondence that occurred during the following events:

original licensing (OL) reviews modifications to the fuel pools to increase the capacity (high density rerack modifications) issuance of Information Notice (IN) 93-83 power uprate of both units performed in 2000.

OL Reviews The OL NRC reviews of the spent fuel cooling and cleanup systems (Reference 10) are described, in part, as follows:

The spent fuel cooling and cleanup systems for each unit are designed to maintain the water quality and clarity of the pool water and to remove the decay heat generated by the stored spent fuel assemblies. The cooling system is designed nonseismic and consists of redundant 100 percent capacity systems. The cooling water for the secondary side of the spent fuel pool cooling system heat exchangers is provided by the nonseismic station service water system. RG 1.13, "Fuel Storage Facility Design Basis,"

and RG 1.29, "Seismic Design Classification," guidelines state that the spent fuel pool Page 13 of 23 ATTACHMENT 1 Response to Request for Additional Information pool (600 gpm total) running continuously for the entire 31 day period while the actual amount of pool water loss due to boiling would be a small fraction of such. The purpose of assuming fuel pool makeup was to reduce the UHS inventory available for accident heat rejection. The fuel pool decay heat for the LSCS model would be approximately 6E6 Btu/hr for each pool (Reference 9). Over a 48 hour5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months period of interest, the integrated fuel pool decay heat represents approximately 4.0% of the total integrated UHS heat load. Over this same period of interest, the UHS volume would be reduced by over 1.5% due to the loss of inventory from the assumed fuel pool makeup. It is EGC's conclusion that the impact of adding the fuel pool decay heat load to the UHS and eliminating fuel pool makeup, i.e, assuming the fuel pools remain cooled and do not boil, would have an insignificant effect on the limiting initial UHS temperature profile of TS Figure 3.7.3-1.

The response of the SGTS to the UHS design event including the DBA LOCA with concurrent loss of offsite power remains unchanged as a result of this proposed license amendment. The ability of LSCS to maintain fuel pool cooling or to provide makeup to the fuel pools was a part of the LSCS original design and is unaffected by the proposed UHS temperature limit change.

The LSCS UHS model evaluates a limiting condition of accident heat load and UHS inventory loss and does not alter the design or licensing bases of the LSCS response to postulated accidents.

EGC Response to Question 8b:

The RHR system, including all piping to and from the spent fuel pool, is independent of the spent fuel pool cooling system and is seismic Category I. The safety related RHR system is powered by the Division 2 onsite emergency diesel generator. Therefore, the safety related RHR system lineup for SFP cooling is available following a LOOP or seismic event.

The NRC has reviewed the design of the LSCS spent fuel pools (SFPs) and the fuel pool cooling system several times over the life of the plant. Brief descriptions and excerpts are provided from several of the NRC reviews and licensing correspondence that occurred during the following events:

original licensing (OL) reviews modifications to the fuel pools to increase the capacity (high density rerack modifications) issuance of Information Notice (IN) 93-83 power uprate of both units performed in 2000.

OL Reviews The OL NRC reviews of the spent fuel cooling and cleanup systems (Reference 10) are described, in part, as follows:

The spent fuel cooling and cleanup systems for each unit are designed to maintain the water quality and clarity of the pool water and to remove the decay heat generated by the stored spent fuel assemblies. The cooling system is designed nonseismic and consists of redundant 100 percent capacity systems. The cooling water for the secondary side of the spent fuel pool cooling system heat exchangers is provided by the nonseismic station service water system. RG 1.13, "Fuel Storage Facility Design Basis,"

and RG 1.29, "Seismic Design Classification," guidelines state that the spent fuel pool Page 13 of 23

ATTACHMENT 1 Response to Request for Additional Information cooling system and its secondary cooling be designed to seismic Category I requirements. The applicant has provided an analysis to show that the results of a failure of the cooling system do not result in a dose release exceeding a small fraction of 10 CFR Part 100 guideline limits. We performed an independent analysis that verified the applicant's results. Based on our analysis, we conclude that the alternative to a seismic Category I designed spent fuel pool cooling system is acceptable.

Note: The response to LSCS FSAR Question 010.29 (Reference 7) provided the analysis of the release occurring during loss of cooling to the spent fuel pool with subsequent boiling of the pool. Operation of the standby gas treatment system was modeled in the analysis. Humidity of the influent air was removed by a demister and electric heater in the standby gas train which is designed to process influent air with 100% relative humidity. The results indicate the calculated doses are many orders of magnitude below 10 CFR 100 limits and only a small fraction of 10 CFR 20 guideline limits.

A permanently installed seismic Category 1 connection from the core standby cooling system-equipment cooling water system provides an alternate makeup water source to the pool.

The residual heat removal system pumps can be cross connected to the fuel pool cooling system to use the residual heat removal system to cool the spent fuel, if necessary.

Based on our review, we conclude that the design of the spent fuel pool cooling and cleanup system is in conformance with the requirements of Criteria 61 and 62 of the General Design Criteria, Branch Technical Position ASB 9-2 with respect to decay heat loads, and the positions in RG 1.13 and RG 1.29, including the positions on availability of assured makeup sources but excluding the position on seismic Category I classification which is justified by dose release analysis described above and is, therefore, acceptable.

The response to FSAR Question 010.19 (Reference 7) states, in part:

The design of the LSCS fuel pool cooling system is in compliance with the requirements of Regulatory Guide 1.13 as stated at the time of the commission's granting of a construction permit for LSCS. The present design of the RHR system and parts of the fuel pool cooling system includes piping which is designed to ASME Section III, Quality Group C, Seismic Category I requirements. The RHR system is also to be used in the event that the fuel pool cooling system should be disabled as the result of a seismic event. All piping which provides the flow path within the fuel pool cooling system to the RHR system and back to the fuel pool has been designed to Seismic Category 1 requirements up to and including the isolation valve which provides the pressure boundary for this mode of operation. All electrical equipment for this mode of operation meet Class 1 E requirements. We believe that the provision of this cross tie with the RHR system meets the guidance set forth in Regulatory Guide 1.29. Those portions of the fuel pool cooling system and the entire RHR system which act as the means of cooling the spent fuel pool meet all stated requirements. The use of the RHR system for Page 14 of 23 A IT ACHMENT 1 Response to Request for Additional Information cooling system and its secondary cooling be designed to seismic Category I requirements. The applicant has provided an analysis to show that the results of a failure of the cooling system do not result in a dose release exceeding a small fraction of 10 CFR Part 100 guideline limits. We performed an independent analysis that verified the applicant's results. Based on our analysis, we conclude that the alternative to a seismic Category I designed spent fuel pool cooling system is acceptable.

Note: The response to LSCS FSAR Question 010.29 (Reference 7) provided the analysis of the release occurring during loss of cooling to the spent fuel pool with subsequent boiling of the pool. Operation of the standby gas treatment system was modeled in the analysis. Humidity of the influent air was removed by a demister and electric heater in the standby gas train which is designed to process influent air with 100% relative humidity. The results indicate the calculated doses are many orders of magnitude below 10 CFR 100 limits and only a small fraction of 10 CFR 20 guideline limits.

A permanently installed seismic Category 1 connection from the core standby cooling system-equipment cooling water system provides an alternate makeup water source to the pool.

The residual heat removal system pumps can be cross connected to the fuel pool cooling system to use the residual heat removal system to cool the spent fuel, if necessary.

Based on our review, we conclude that the design of the spent fuel pool cooling and cleanup system is in conformance with the requirements of Criteria 61 and 62 of the General Design Criteria, Branch Technical Position ASB 9-2 with respect to decay heat loads, and the positions in RG 1.13 and RG 1.29, including the positions on availability of assured makeup sources but excluding the position on seismic Category I classification which is justified by dose release analysis described above and is, therefore, acceptable.

The response to FSAR Question 010.19 (Reference 7) states, in part:

The design of the LSCS fuel pool cooling system is in compliance with the requirements of Regulatory Guide 1.13 as stated at the time of the commission's granting of a construction permit for LSCS. The present design of the RHR system and parts of the fuel pool cooling system includes piping which is designed to ASME Section III, Quality Group C, Seismic Category I requirements. The RHR system is also to be used in the event that the fuel pool cooling system should be disabled as the result of a seismic event. All piping which provides the flow path within the fuel pool cooling system to the RHR system and back to the fuel pool has been designed to Seismic Category 1 requirements up to and including the isolation valve which provides the pressure boundary for this mode of operation. All electrical equipment for this mode of operation meet Class 1 E requirements. We believe that the provision of this cross tie with the RHR system meets the guidance set forth in Regulatory Guide 1.29. Those portions of the fuel pool cooling system and the entire RHR system which act as the means of cooling the spent fuel pool meet all stated requirements. The use of the RHR system for Page 14 of 23

ATTACHMENT 1 Response to Request for Additional Information cooling the fuel pool during abnormal circumstances provides a safe and adequate means of maintaining the fuel pool at acceptable temperatures.

High Density Rerack Modifications The LSCS Unit 2 rerack NRC SE (Reference 8) states, in part:

The spent fuel pool cooling system (SFPCS) consists of two identical trains of equipment. Each train consists of one 3000 gpm centrifugal pump and one 14.6 MBtu/Hr tube-and-shell heat exchanger. After water from the spent fuel pool is cooled by the heat exchangers, it is purified by the spent fuel pool cleanup system. Neither the SFPCS nor the cleanup system is seismic Category I. In the event of an excessive heat load, the "B" loop of the Residual Heat Removal (RHR) system can be used to cool the spent fuel pool. The RHR system, including all piping to and from the spent fuel pool, is independent of the SFPCS and is seismic Category I.

The SFPCS is not seismic Category I and it is not powered by a Class 1 E source (i.e.,

on-site emergency diesel generator). Under such circumstances, SRP Section 9.1.3 identifies an alternative method for cooling of spent fuel following an earthquake.

Specifically, the SRP discusses use of a seismic Category I spent fuel pool makeup water capability and a seismic Category I ventilation system to process potential radiological releases to the pool building resulting from pool boiling. The LaSalle FSAR identifies the emergency fuel pool makeup system (EFPMS) as the seismic Category I makeup water system for the spent fuel pool.

The EFPMS includes two 300 gpm pumps and is part of the seismic Category I core standby cooling system-equipment cooling water system (CSCS-EWCS).

With regard to qualified ventilation capability when seismic Category I spent fuel pool cooling is not provided, the LSCS FSAR identifies the SGTS as the qualified ventilation system. The SGTS is designed to seismic Category I criteria and consists of two redundant filter trains. This system is designed to remain operational during design basis events and is protected against natural phenomena.

The staff further concludes that the seismic Category 1 EFPMS and SGTS meet the requirements of GDC 2 for ensuring adequate spent fuel pool cooling and prevention of unacceptable radiological releases following an earthquake.

The LSCS Unit 1 rerack NRC SE (Reference 11) discusses Spent Fuel Pool Time to Boil and shows that the NRC calculated a similar SFP Time to Boil to that shown in the current UFSAR Table 9.1-6. The NRC then concluded that the guidance of the Standard Review Plan were met and that the bulk coolant time to boil was acceptable since it provided a reasonable time to allow operators to use alternative methods to cool the SFP coolant, or to provide makeup coolant in the event that the SFP coolant begins to boil.

Page 15 of 23 A IT ACHMENT 1 Response to Request for Additional Information cooling the fuel pool during abnormal circumstances provides a safe and adequate means of maintaining the fuel pool at acceptable temperatures.

High Density Rerack Modifications The LSCS Unit 2 rerack NRC SE (Reference 8) states, in part:

The spent fuel pool cooling system (SFPCS) consists of two identical trains of equipment. Each train consists of one 3000 gpm centrifugal pump and one 14.6 MBtu/Hr tube-and-shell heat exchanger. After water from the spent fuel pool is cooled by the heat exchangers, it is purified by the spent fuel pool cleanup system. Neither the SFPCS nor the cleanup system is seismic Category I. In the event of an excessive heat load, the "B" loop of the Residual Heat Removal (RHR) system can be used to cool the spent fuel pool. The RHR system, including all piping to and from the spent fuel pool, is independent of the SFPCS and is seismic Category I.

The SFPCS is not seismic Category I and it is not powered by a Class 1 E source (Le.,

on-site emergency diesel generator). Under such circumstances, SRP Section 9.1.3 identifies an alternative method for cooling of spent fuel following an earthquake.

Specifically, the SRP discusses use of a seismic Category I spent fuel pool makeup water capability and a seismic Category I ventilation system to process potential radiological releases to the pool building resulting from pool boiling. The LaSalle FSAR identifies the emergency fuel pool makeup system (EFPMS) as the seismic Category I makeup water system for the spent fuel pool.

The EFPMS includes two 300 gpm pumps and is part of the seismic Category I core standby cooling system-equipment cooling water system (CSCS-EWCS).

With regard to qualified ventilation capability when seismic Category I spent fuel pool cooling is not provided, the LSCS FSAR identifies the SGTS as the qualified ventilation system. The SGTS is designed to seismic Category I criteria and consists of two redundant filter trains. This system is designed to remain operational during design basis events and is protected against natural phenomena.

The staff further concludes that the seismic Category 1 EFPMS and SGTS meet the requirements of GDC 2 for ensuring adequate spent fuel pool cooling and prevention of unacceptable radiological releases following an earthquake.

The LSCS Unit 1 rerack NRC SE (Reference 11) discusses Spent Fuel Pool Time to Boil and shows that the NRC calculated a similar SFP Time to Boil to that shown in the current UFSAR Table 9.1-6. The NRC then concluded that the guidance of the Standard Review Plan were met and that the bulk coolant time to boil was acceptable since it provided a reasonable time to allow operators to use alternative methods to cool the SFP coolant, or to provide makeup coolant in the event that the SFP coolant begins to boil.

Page 15 of 23

ATTACHMENT 1 Response to Request for Additional Information Issuance of IN 93-83 The NRC issued IN 93-83, "Potential Loss of Spent Fuel Pool Cooling Following a Loss of Coolant Accident (LOCA)," on October 7, 1993 (Reference 12). This document notified licensees of concerns regarding the potential effects of a loss of spent fuel pool (SPC) cooling coincident with a LOCA at Susquehanna Steam Electric Station (SSES) in 1992. The document identified the potential inability to align emergency methods of SFP cooling and makeup water addition under post-LOCA conditions.

Following issuance of IN 93-83, the NRC issued a letter to LSCS dated September 25, 1996, titled, "Resolution of Spent Fuel Storage Pool Safety Issues: Issuance of Final Staff Report and Notification of Staff Plans to Perform Plant Specific, Safety Enhancement Backfit Analyses -

LaSalle Station," (Reference 13). The letter states, in part:

The staff has found existing structures, systems, and components related to the storage of irradiated fuel provide adequate protection for the public health and safety. Protection has been provided by several layers of defenses that perform accident prevention functions, accident mitigation functions (e.g., multiple cooling systems and multiple makeup water paths), radiation protection functions, and emergency preparedness functions. Design features addressing each of these areas for spent fuel storage have been reviewed and approved by the staff. In addition, the limited risk analyses available for spent fuel storage suggest that current design features and operational constraints cause issues related to spent fuel pool storage to be a small fraction of the overall risk associated with an operating light water reactor.

The September 25, 1996, letter also identified LSCS as one of seven operating plants having three design characteristics similar to SSES requiring additional staff review:

An open path from the area around the SFP to areas housing safety systems A short time for the SFP to reach an elevated temperature A reactor site with multiple operating units sharing structures and systems related to the SFP The LSCS response to this issue was contained in a letter to the NRC dated November 18, 1996 (Reference 14), which states, in part:

While LaSalle is a multi-unit site with shared systems and structures, an appreciable concern does not exist at this site. Taking into account the actual time to boil, the low probability of an initiating event, and the availability of reduced means to cool the SFP from onsite power, this concern does not warrant further consideration at this time.

The response described the reliability of SFP cooling as follows:

Following a loss of offsite power, SFP cooling can be reestablished on onsite power by either restoring the fuel pool cooling system or through the FPC assist mode of RHR.

While both methods would require alterations in their respective systems, either could be accomplished in the time frame allowed prior to bulk boiling. The availability of the relied upon systems is protected by the station's shutdown risk program, which specifically addresses risk margins for decay heat removal.

Page 16 of 23 ATTACHMENT 1 Response to Request for Additional Information Issuance of IN 93-83 The NRC issued IN 93-83, "Potential Loss of Spent Fuel Pool Cooling Following a Loss of Coolant Accident (LOCA)," on October 7,1993 (Reference 12). This document notified licensees of concerns regarding the potential effects of a loss of spent fuel pool (SPC) cooling coincident with a LOCA at Susquehanna Steam Electric Station (SSES) in 1992. The document identified the potential inability to align emergency methods of SFP cooling and makeup water addition under post-LOCA conditions.