Text

Request for a License Amendment, Technical Specification 3.7.3, Ultimate Heat Sink
	ML12200A330
Person / Time
Site:	LaSalle
Issue date:	07/12/2012
From:	Gullott D; Exelon Generation Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	RS-12-084
	Download: ML12200A330 (56)
	v • d • e

RS-12-084 July 12, 2012 10 CFR 50.90 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-1 1 and NPF-1 8 NRC Docket Nos. 50-373 and 50-374

Subject:

Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, "Ultimate Heat Sink" In accordance with 10 CFR 50.90, "Application for amendment of license or construction permit," Exelon Generation Company, LLC (EGC) is requesting a change to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2. Currently, Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Ultimate Heat Sink (UHS) is

<_ 101.25 OF. If the UHS indicated temperature exceeds 101.25 OF, TS 3.7.3 Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. Meteorological conditions in the future may continue challenging the current TS limit of

<_ 101.25 OF.

As described in Regulatory Guide 1.27, "Ultimate Heat Sink for Nuclear Power Plants,"

Revision 1, the predicted response of the UHS temperature to the design basis event is a function of the historical weather including the diurnal variations in air temperature. This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle. The TS limit will be graphical with the UHS temperature limit varying as a function of time of day. The purpose of the UHS TS temperature limit is to restrict the initial UHS temperature such that the maximum UHS temperature experienced during the UHS design basis event (i.e., the temperature of the cooling water supplied to the plant safety systems from the UHS) would not exceed the design limit of 107 OF. The proposed TS temperature limit will therefore vary with the diurnal cycle to limit the maximum temperature of the UHS supplied to plant safety systems to <_ 107 O F. If the temperature of the cooling water supplied to the plant from the UHS exceeds the TS limit, Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

1 RS-12-084 July 12, 2012 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374 10 CFR 50.90

Subject:

Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, "Ultimate Heat Sink" In accordance with 10 CFR 50.90, "Application for amendment of license or construction permit," Exelon Generation Company, LLC (EGC) is requesting a change to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2. Currently, Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Ultimate Heat Sink (UHS) is s; 101.25 oF. If the UHS indicated temperature exceeds 101.25 of, TS 3.7.3 Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. Meteorological conditions in the future may continue challenging the current TS limit of s; 101.25 of.

As described in Regulatory Guide 1.27, "Ultimate Heat Sink for Nuclear Power Plants,"

Revision 1, the predicted response of the UHS temperature to the design basis event is a function of the historical weather including the diurnal variations in air temperature. This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle. The TS limit will be graphical with the UHS temperature limit varying as a function of time of day. The purpose of the UHS TS temperature limit is to restrict the initial UHS temperature such that the maximum UHS temperature experienced during the UHS design basis event (i.e., the temperature of the cooling water supplied to the plant safety systems from the UHS) would not exceed the design limit of 107 of. The proposed TS temperature limit will therefore vary with the diurnal cycle to limit the maximum temperature of the UHS supplied to plant safety systems to s; 107 oF. If the temperature of the cooling water supplied to the plant from the UHS exceeds the TS limit, Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

1 RS-12-084 July 12, 2012 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374 10 CFR 50.90

Subject:

Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, "Ultimate Heat Sink" In accordance with 10 CFR 50.90, "Application for amendment of license or construction permit," Exelon Generation Company, LLC (EGC) is requesting a change to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2. Currently, Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Ultimate Heat Sink (UHS) is s; 101.25 oF. If the UHS indicated temperature exceeds 101.25 of, TS 3.7.3 Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. Meteorological conditions in the future may continue challenging the current TS limit of s; 101.25 of.

As described in Regulatory Guide 1.27, "Ultimate Heat Sink for Nuclear Power Plants,"

Revision 1, the predicted response of the UHS temperature to the design basis event is a function of the historical weather including the diurnal variations in air temperature. This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle. The TS limit will be graphical with the UHS temperature limit varying as a function of time of day. The purpose of the UHS TS temperature limit is to restrict the initial UHS temperature such that the maximum UHS temperature experienced during the UHS design basis event (i.e., the temperature of the cooling water supplied to the plant safety systems from the UHS) would not exceed the design limit of 107 of. The proposed TS temperature limit will therefore vary with the diurnal cycle to limit the maximum temperature of the UHS supplied to plant safety systems to s; 107 oF. If the temperature of the cooling water supplied to the plant from the UHS exceeds the TS limit, Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

July 12, 2012 U. S. Nuclear Regulatory Commission Page 2 The attached amendment request is subdivided as follows: provides an evaluation of the proposed change. provides the current TS pages with the proposed changes indicated with markups. provides the current TS Bases pages with the proposed changes indicated with markups. The TS Bases pages are provided for information only and do not require NRC approval. provides a revised copy of the TS pages with the proposed changes incorporated. provides a discussion of LaSalle County Station Core Standby Cooling System-Equipment Cooling Water System (CSCS-ECWS) cooling capabilities at 107 OF provides the worst 24-hour and 30-day weather data resulting in the maximum plant intake temperature that was used in LaSalle County Station Analysis L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," Revision 7 EGC requests approval of the proposed change by July 12, 2013, with the amendment being implemented within 30 days of issuance.

The proposed amendment has been reviewed by the LSCS Plant Operations Review Committee and approved by the Nuclear Safety Review Board in accordance with the requirements of the EGC Quality Assurance Program.

July 12, 2012 U. S. Nuclear Regulatory Commission Page 2 The attached amendment request is subdivided as follows: provides an evaluation of the proposed change. provides the current TS pages with the proposed changes indicated with markups. provides the current TS Bases pages with the proposed changes indicated with markups. The TS Bases pages are provided for information only and do not require NRC approval. provides a revised copy of the TS pages with the proposed changes incorporated. provides a discussion of LaSalle County Station Core Standby Cooling System-Equipment Cooling Water System (CSCS-ECWS) cooling capabilities at 107 of provides the worst 24-hour and 30-day weather data resulting in the maximum plant intake temperature that was used in LaSalle County Station Analysis L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," Revision 7 EGC requests approval of the proposed change by July 12, 2013, with the amendment being implemented within 30 days of issuance.

The proposed amendment has been reviewed by the LSCS Plant Operations Review Committee and approved by the Nuclear Safety Review Board in accordance with the requirements of the EGC Quality Assurance Program.

July 12, 2012 U. S. Nuclear Regulatory Commission Page 2 The attached amendment request is subdivided as follows: provides an evaluation of the proposed change. provides the current TS pages with the proposed changes indicated with markups. provides the current TS Bases pages with the proposed changes indicated with markups. The TS Bases pages are provided for information only and do not require NRC approval. provides a revised copy of the TS pages with the proposed changes incorporated. provides a discussion of LaSalle County Station Core Standby Cooling System-Equipment Cooling Water System (CSCS-ECWS) cooling capabilities at 107 of provides the worst 24-hour and 30-day weather data resulting in the maximum plant intake temperature that was used in LaSalle County Station Analysis L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," Revision 7 EGC requests approval of the proposed change by July 12, 2013, with the amendment being implemented within 30 days of issuance.

The proposed amendment has been reviewed by the LSCS Plant Operations Review Committee and approved by the Nuclear Safety Review Board in accordance with the requirements of the EGC Quality Assurance Program.

July 12, 2012 U. S. Nuclear Regulatory Commission Page 3 EGC is notifying the State of Illinois of this application for a change to the TS by sending a copy of this letter and its attachments to the designated State Official in accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b).

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mitch Mathews at (630) 657-2819.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 12th day of July 2012.

Respectfully, David M. Gullott Manager, Licensing Evaluation of Proposed Change Mark-up of Proposed Technical Specifications Page Change Markup of Proposed Technical Specifications Bases Page Changes - For Information Only Revised Technical Specifications Pages A Discussion of the LaSalle County Station Core Standby Cooling System-Equipment Cooling Water System (CSCS-ECWS) Heat Transfer Capabilities at 107 OF Worst 24-Hour and 30-Day Weather Data Resulting in the Maximum Plant Intake Temperature Used in LaSalle County Station Analysis L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," Revision 7 : : : : : :

cc: Illinois Emergency Management Agency - Division of Nuclear Safety July 12, 2012 U. S. Nuclear Regulatory Commission Page 3 EGC is notifying the State of Illinois of this application for a change to the TS by sending a copy of this letter and its attachments to the designated State Official in accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b).

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mitch Mathews at (630) 657-2819.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 12th day of July 2012.

Respectfully, David M. Gullott Manager, Licensing : Evaluation of Proposed Change :

Mark-up of Proposed Technical Specifications Page Change : Markup of Proposed Technical Specifications Bases Page Changes - For Information Only : Revised Technical Specifications Pages : A Discussion of the LaSalle County Station Core Standby Cooling System-Equipment Cooling Water System (CSCS-ECWS) Heat Transfer Capabilities at 107 OF : Worst 24-Hour and 30-Day Weather Data Resulting in the Maximum Plant Intake Temperature Used in LaSalle County Station Analysis L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," Revision 7 cc: Illinois Emergency Management Agency - Division of Nuclear Safety July 12, 2012 U. S. Nuclear Regulatory Commission Page 3 EGC is notifying the State of Illinois of this application for a change to the TS by sending a copy of this letter and its attachments to the designated State Official in accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b).

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mitch Mathews at (630) 657-2819.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 12th day of July 2012.

Respectfully, David M. Gullott Manager, Licensing : Evaluation of Proposed Change :

Mark-up of Proposed Technical Specifications Page Change : Markup of Proposed Technical Specifications Bases Page Changes - For Information Only : Revised Technical Specifications Pages : A Discussion of the LaSalle County Station Core Standby Cooling System-Equipment Cooling Water System (CSCS-ECWS) Heat Transfer Capabilities at 107 OF : Worst 24-Hour and 30-Day Weather Data Resulting in the Maximum Plant Intake Temperature Used in LaSalle County Station Analysis L-002457, "LaSalle County Station Ultimate Heat Sink Analysis," Revision 7 cc: Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT I Evaluation of Proposed Change

Subject:

Request for a License Amendment to Technical Specification 3.7.3, "Ultimate Heat Sink"

1.0 DESCRIPTION

2.0 PROPOSED CHANGE

S

3.0 BACKGROUND

4.0 TECHNICAL ANALYSIS

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration 5.2 Applicable Regulatory Requirements/Criteria 6.0 ENVIRONMENTAL EVALUATION

7.0 REFERENCES

Page 1 of 21 ATTACHMENT 1 Evaluation of Proposed Change

Subject:

Request for a License Amendment to Technical Specification 3.7.3, "Ultimate Heat Sink"

1.0 DESCRIPTION

2.0 PROPOSED CHANGE

S

3.0 BACKGROUND

4.0 TECHNICAL ANALYSIS

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration 5.2 Applicable Regulatory Requirements/Criteria 6.0 ENVIRONMENTAL EVALUATION

7.0 REFERENCES

Page 1 of 21 ATTACHMENT 1 Evaluation of Proposed Change

Subject:

Request for a License Amendment to Technical Specification 3.7.3, "Ultimate Heat Sink"

1.0 DESCRIPTION

2.0 PROPOSED CHANGE

S

3.0 BACKGROUND

4.0 TECHNICAL ANALYSIS

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration 5.2 Applicable Regulatory Requirements/Criteria 6.0 ENVIRONMENTAL EVALUATION

7.0 REFERENCES

Page 1 of 21

ATTACHMENT I Evaluation of Proposed Change

1.0 DESCRIPTION

In accordance with 10 CFR 50.90, "Application for amendment of license or construction permit," Exelon Generation Company, LLC (EGC) is requesting a change to the Technical Specifications (TS) of Facility Operating License Nos. NPF-1 1 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2. Currently, Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Ultimate Heat Sink (UHS) is

<< 101.25 OF. If the UHS indicated temperature exceeds 101.25 OF, TS 3.7.3 Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. 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. Should the postulated event occur during the day, the allowable UHS temperature would be different (i.e., lower) than if the postulated event occurs at night.

The physical configuration of the UHS pond influences its capability to transfer heat to the environment. The UHS design analysis has been improved to account for the surface area and volume of the UHS pond that are not effective. The effective surface area and volume were determined using computational fluid dynamics (CFD) which determined the UHS flow pattern during the design basis event. The recirculation areas of the UHS are identified and the UHS volume actively involved in the main water flow is determined along with the associated surface area.

Previous revisions of the design analysis utilized historical weather data from 1948 to 1996.

This analysis has been updated to include weather data through September 30, 2010, which includes the period where the maximum indicated cooling water supplied to plant from the cooling lake was observed. The UHS temperature design analysis methodology is based on Regulatory Guide 1.27, Revision 1, "Ultimate Heat sink for Nuclear Power Plants," and NUREG-0693, "Analysis of Ultimate Heat Sink Cooling Ponds," dated November 1980.

This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle and to reflect the effect of more severe weather. Regulatory Position C.1.b of RG 1.27, Revision 1 states that the UHS temperature transient analysis should include diurnal variations during the 1-day and 30-day evaluation periods. The purpose of the UHS temperature limit is to ensure the initial 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 during the 30 day worst weather period. The UHS temperature limit varies with the diurnal cycle such that the most restrictive temperature occurring in the morning hours ensures that the maximum temperature of the cooling water supplied to the plant remains below the 107 °F design limit regardless of when the postulated event occurs. The current LaSalle TS uses the most restrictive temperature as the limit independent of the time of day. This results in an excessive reduction in available margin during recent meteorological conditions. This proposed license amendment Page 2 of 21

1.0 DESCRIPTION

ATTACHMENT 1 Evaluation of Proposed Change In accordance with 10 CFR 50.90, "Application for amendment of license or construction permit," Exelon Generation Company, LLC (EGC) is requesting a change to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2. Currently, Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Ultimate Heat Sink (UHS) is

101.25 oF. If the UHS indicated temperature exceeds 101.25 of, TS 3.7.3 Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. 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. Should the postulated event occur during the day, the allowable UHS temperature would be different (Le., lower) than if the postulated event occurs at night.

The physical configuration of the UHS pond influences its capability to transfer heat to the environment. The UHS design analysis has been improved to account for the surface area and volume of the UHS pond that are not effective. The effective surface area and volume were determined using computational fluid dynamics (CFD) which determined the UHS flow pattern during the design basis event. The recirculation areas of the UHS are identified and the UHS volume actively involved in the main water flow is determined along with the associated surface area.

Previous revisions of the design analysis utilized historical weather data from 1948 to 1996.

This analysis has been updated to include weather data through September 30, 2010, which includes the period where the maximum indicated cooling water supplied to plant from the cooling lake was observed. The UHS temperature design analysis methodology is based on Regulatory Guide 1.27, Revision 1, "Ultimate Heat sink for Nuclear Power Plants," and NUREG-0693, "Analysis of Ultimate Heat Sink Cooling Ponds," dated November 1980.

This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle and to reflect the effect of more severe weather. Regulatory Position C.1.b of RG 1.27, Revision 1 states that the UHS temperature transient analysis should include diurnal variations during the 1-day and 30-day evaluation periods. The purpose of the UHS temperature limit is to ensure the initial 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 during the 30 day worst weather period. The UHS temperature limit varies with the diurnal cycle such that the most restrictive temperature occurring in the morning hours ensures that the maximum temperature of the cooling water supplied to the plant remains below the 107 of design limit regardless of when the postulated event occurs. The current LaSalle TS uses the most restrictive temperature as the limit independent of the time of day. This results in an excessive reduction in available margin during recent meteorological conditions. This proposed license amendment Page 2 of 21

1.0 DESCRIPTION

ATTACHMENT 1 Evaluation of Proposed Change In accordance with 10 CFR 50.90, "Application for amendment of license or construction permit," Exelon Generation Company, LLC (EGC) is requesting a change to the Technical Specifications (TS) of Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2. Currently, Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Ultimate Heat Sink (UHS) is

101.25 oF. If the UHS indicated temperature exceeds 101.25 of, TS 3.7.3 Required Actions B.1 and B.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. 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. Should the postulated event occur during the day, the allowable UHS temperature would be different (Le., lower) than if the postulated event occurs at night.

The physical configuration of the UHS pond influences its capability to transfer heat to the environment. The UHS design analysis has been improved to account for the surface area and volume of the UHS pond that are not effective. The effective surface area and volume were determined using computational fluid dynamics (CFD) which determined the UHS flow pattern during the design basis event. The recirculation areas of the UHS are identified and the UHS volume actively involved in the main water flow is determined along with the associated surface area.

Previous revisions of the design analysis utilized historical weather data from 1948 to 1996.

This analysis has been updated to include weather data through September 30, 2010, which includes the period where the maximum indicated cooling water supplied to plant from the cooling lake was observed. The UHS temperature design analysis methodology is based on Regulatory Guide 1.27, Revision 1, "Ultimate Heat sink for Nuclear Power Plants," and NUREG-0693, "Analysis of Ultimate Heat Sink Cooling Ponds," dated November 1980.

This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle and to reflect the effect of more severe weather. Regulatory Position C.1.b of RG 1.27, Revision 1 states that the UHS temperature transient analysis should include diurnal variations during the 1-day and 30-day evaluation periods. The purpose of the UHS temperature limit is to ensure the initial 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 during the 30 day worst weather period. The UHS temperature limit varies with the diurnal cycle such that the most restrictive temperature occurring in the morning hours ensures that the maximum temperature of the cooling water supplied to the plant remains below the 107 of design limit regardless of when the postulated event occurs. The current LaSalle TS uses the most restrictive temperature as the limit independent of the time of day. This results in an excessive reduction in available margin during recent meteorological conditions. This proposed license amendment Page 2 of 21

ATTACHMENT I Evaluation of Proposed Change will implement a UHS temperature versus time of day graph to limit the allowable UHS temperature. The TS graph is conservatively based on the UHS temperature response assuming the UHS sedimentation level at the TS limit of 18 inches.

If the UHS indicated temperature exceeds the allowable UHS temperature at a given time, Required Actions B.1 and B.2 would be entered concurrently, and both LSCS units would be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and in Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

The proposed license amendment will ensure the maximum temperature of the cooling water supplied to the plant during the UHS design basis event remains 5 107 OF, LaSalle's current safety-related cooling water design temperature.

Therefore, there is no impact of this change on LaSalle safety analyses including the long term suppression pool temperature.

2.0 PROPOSED CHANGE

S The proposed changes to TS 3.7.3 are shown in Figures 1, 2, and 3 below:

Required Actic associated C Time of Condition A not met.

B.

Cooling water temperature supplied to the pant from the CSCS pond > 1o1°F_

Perform SR 3.7.3.2_

Once per hour Figure 1:

New TS 3.7.3 Condition Requiring Hourly Cooling Water Temperature Monitoring When Cooling Water Temperature is 101 OF or Higher Page 3 of 21 ATTACHMENT 1 Evaluation of Proposed Change will implement a UHS temperature versus time of day graph to limit the allowable UHS temperature. The TS graph is conservatively based on the UHS temperature response assuming the UHS sedimentation level at the TS limit of 18 inches.

If the UHS indicated temperature exceeds the allowable UHS temperature at a given time, Required Actions B.1 and B.2 would be entered concurrently, and both LSCS units would be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and in Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

The proposed license amendment will ensure the maximum temperature of the cooling water supplied to the plant during the UHS design basis event remains s 107 of, LaSalle's current safety-related cooling water design temperature. Therefore, there is no impact of this change on LaSalle safety analyses including the long term suppression pool temperature.

2.0 PROPOSED CHANGE

S The proposed changes to TS 3.7.3 are shown in Figures 1, 2, and 3 below:

Required Action and associated Completion Time of Condition A not !I1et.

-lL 1 Be HI MODE 3.

"tZ A!ill~

Be in MODE 4.

12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months 36 hours I

cscs pond inoperable for reasons other than Condition A.

I L-J I

B.

Cooling water temperature supplied to the p'ant from the CSCS pond ~ 101°F.

B.l Perform SR 3.7.3.1.

Once per hOur Figure 1: New TS 3.7.3 Condition Requiring Hourly Cooling Water Temperature Monitoring When Cooling Water Temperature is 101°F or Higher Page 3 of 21 ATTACHMENT 1 Evaluation of Proposed Change will implement a UHS temperature versus time of day graph to limit the allowable UHS temperature. The TS graph is conservatively based on the UHS temperature response assuming the UHS sedimentation level at the TS limit of 18 inches.

If the UHS indicated temperature exceeds the allowable UHS temperature at a given time, Required Actions B.1 and B.2 would be entered concurrently, and both LSCS units would be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and in Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

The proposed license amendment will ensure the maximum temperature of the cooling water supplied to the plant during the UHS design basis event remains s 107 of, LaSalle's current safety-related cooling water design temperature. Therefore, there is no impact of this change on LaSalle safety analyses including the long term suppression pool temperature.

2.0 PROPOSED CHANGE

S The proposed changes to TS 3.7.3 are shown in Figures 1, 2, and 3 below:

Required Action and associated Completion Time of Condition A not !I1et.

-lL 1 Be HI MODE 3.

"tZ A!ill~

Be in MODE 4.

12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months 36 hours I

cscs pond inoperable for reasons other than Condition A.

I L-J I

B.

Cooling water temperature supplied to the p'ant from the CSCS pond ~ 101°F.

B.l Perform SR 3.7.3.1.

Once per hOur Figure 1: New TS 3.7.3 Condition Requiring Hourly Cooling Water Temperature Monitoring When Cooling Water Temperature is 101°F or Higher Page 3 of 21

ATTACHMENT I Evaluation of Proposed Change UHS 3-7.3 FREQUENCY SR 3.7.3-1 Veri y cc e DI g water temperature supplied from the CSCS pond is

.7 Figure 2: New Acceptance Criterion for SR 3.7.3.1 105.00 In accordance with the Surveillance Frequency Control Program 104.50 104.00 102.00 101.50 Unacceptable Operation (104.00)

(104.00) ; (104.00)

(104.00)

Acceptable Operation (103.78) 101.00

^_

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00 Time of Day Figure 3.7.3-1 (page 1 of 1)

Temperature of Cooling Water Supplied to the Plant from the CSCS Pond Versus Time of Day Requirements Figure 3: New TS Figure 3.7.3-1 Defining Acceptance Criteria for SR 3.7.3.1

3.0 BACKGROUND

The UHS provides a heat sink for process and operating heat from safety related components during the UHS design basis event. The Residual Heat Removal Service Water (RHRSW)

Page 4 of 21 ATTACHMENT 1 Evaluation of Proposed Change UHS 3.7.3 SURVEILLANCE REQUIREMENTS SURVEILLANCE Verify cooling water temperature supplied to the ant from the CSCS is Figure 2: New Acceptance Criterion for SR 3.7.3.1 FREQUENCY In accordance with the Surveillance Frequency Control Program 105. 00..,.-----,-----.,.---~,---------_r___--__r------___,

104.50 +-__

........4._

104.00 +-----i--

Unacceptable Operation (104.00) : (104.00). (104.00). (104.00)

(103.78)

~ 103.50 +-\\-----+-----------f--+.----;........--~-------

QJ

'-E 103. 00 +----\\--------~------.-+-.. -.--.------.----.. --.

QJ C.

E

~ 102.50 +----\\---,------...........;{-----i----'--

Acceptable Operation 102.00 +----Jt:-------+--

101. 50 +. -----~---'_+_---'-----,__------------___1 101. Of) -'-1---...,------------,---------....-----,------1 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21 :00 Time of Day Figure 3.7.3-1 (page 1 of 1)

Temperature of Cooling Water Supplied to the Plant from the CSCS Pond Versus Time of Day Requirements Figure 3: New TS Figure 3.7.3-1 Defining Acceptance Criteria for SR 3.7.3.1

3.0 BACKGROUND

24:00 The UHS provides a heat sink for process and operating heat from safety related components during the UHS design basis event. The Residual Heat Removal Service Water (RHRSW)

Page 4 of 21 ATTACHMENT 1 Evaluation of Proposed Change UHS 3.7.3 SURVEILLANCE REQUIREMENTS SURVEILLANCE Verify cooling water temperature supplied to the ant from the CSCS is Figure 2: New Acceptance Criterion for SR 3.7.3.1 FREQUENCY In accordance with the Surveillance Frequency Control Program 105. 00..,.-----,-----.,.---~,---------_r___--__r------___,

104.50 +-__

........4._

104.00 +-----i--

Unacceptable Operation (104.00) : (104.00). (104.00). (104.00)

(103.78)

~ 103.50 +-\\-----+-----------f--+.----;........--~-------

QJ

'-E 103. 00 +----\\--------~------.-+-.. -.--.------.----.. --.

QJ C.

E

~ 102.50 +----\\---,------...........;{-----i----'--

Acceptable Operation 102.00 +----Jt:-------+--

101. 50 +. -----~---'_+_---'-----,__------------___1 101. Of) -'-1---...,------------,---------....-----,------1 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21 :00 Time of Day Figure 3.7.3-1 (page 1 of 1)

Temperature of Cooling Water Supplied to the Plant from the CSCS Pond Versus Time of Day Requirements Figure 3: New TS Figure 3.7.3-1 Defining Acceptance Criteria for SR 3.7.3.1

3.0 BACKGROUND

24:00 The UHS provides a heat sink for process and operating heat from safety related components during the UHS design basis event. The Residual Heat Removal Service Water (RHRSW)

Page 4 of 21

ATTACHMENT I Evaluation of Proposed Change system and Diesel Generator Cooling Water (DGCW) system are the principal systems at LSCS that utilize the UHS to reject heat from safety related plant loads.

The UHS consists of an excavated pond integral with the cooling lake. The volume of the pond is sized to permit the safe shutdown and cooldown of both LSCS units for a 30-day period design basis event with no additional makeup water source. The UHS design basis event includes a failure of the LSCS cooling lake dike resulting in the UHS as the remaining source of cooling water to plant safety systems. The design basis event for the LSCS UHS is a loss of offsite power (LOOP) on both units resulting in all emergency diesel generators running, while one unit experiences an accident (i.e., a design basis accident (DBA) loss of coolant accident (LOCA)) while the other unit is shutdown normally. The function of the UHS is to provide cooling of the RHR heat exchangers, diesel generator coolers, Emergency Core Cooing System (ECCS) cubicle area cooling coils, RHR pump seal coolers, and Low Pressure Core Spray (LPCS) pump motor cooling coils. The UHS provides indirect heat rejection for the containment through the RHR heat exchangers. The current maximum safety-related cooling water design temperature at LSCS has been evaluated to be 107 OF. Attachment 5 discusses the impact of 107 OF UHS cooling water on the design functions of Core Standby Cooling System -

Emergency Cooling Water System (CSCS-ECWS) components.

The UHS also provides a source of emergency makeup water for the spent fuel pools and can provide water for fire protection equipment. Loss of UHS inventory due to spent fuel pool makeup and fire protection usage is considered in the UHS analyses for both the temperature response and the inventory response.

There are four temperature measuring instruments used for monitoring the temperature of the lake cooling water provided to the plant. These instruments are located in the circulating water (CW) system inlet thermowells (i.e., two per unit), that provide input to the Plant Process Computer (PPC). The outputs of these instruments are used to monitor and trend the temperature of the lake cooling water temperature supplied to the plant via the PPC, and are utilized in verifying the requirement of SR 3.7.3.1 is met at a 24-hour frequency as required by the LSCS Surveillance Frequency Control Program (SFCP). Since the UHS is an integral part of the cooling lake, an excavated pond at the outlet of the cooling lake, UHS temperature is the same as the lake cooling water temperature. Reference 1 documents the fact that the two-channel average uncertainty in the UHS temperature measurement is less than 0.75 OF.

The calculated uncertainty for one available loop is +0.74 OF and for two available loops is

+0.53 OF. It is considered extremely unlikely that three of the four resistance temperature detectors or associated circuitry would be unavailable simultaneously. In the unlikely event this condition were to occur, the 0.75 OF allowance for conservatism bounds the instrument uncertainties associated with any combination of operable temperature measurement devices to meet the requirements of SR 3.7.3.1.

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. Weather conditions in the future may continue challenging the current TS limit of

<_ 101.25 OF.

This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle and to account for recent Page 5 of 21 ATTACHMENT 1 Evaluation of Proposed Change system and Diesel Generator Cooling Water (DGCW) system are the principal systems at LSCS that utilize the UHS to reject heat from safety related plant loads.

The UHS consists of an excavated pond integral with the cooling lake. The volume of the pond is sized to permit the safe shutdown and cooldown of both LSCS units for a 30-day period design basis event with no additional makeup water source. The UHS design basis event includes a failure of the LSCS cooling lake dike resulting in the UHS as the remaining source of cooling water to plant safety systems. The design basis event for the LSCS UHS is a loss of offsite power (LOOP) on both units resulting in all emergency diesel generators running, while one unit experiences an accident (Le., a design basis accident (DBA) loss of coolant accident (LOCA>> while the other unit is shutdown normally. The function of the UHS is to provide cooling of the RHR heat exchangers, diesel generator coolers, Emergency Core Cooing System (ECCS) cubicle area cooling coils, RHR pump seal coolers, and Low Pressure Core Spray (LPCS) pump motor cooling coils. The UHS provides indirect heat rejection for the containment through the RHR heat exchangers. The current maximum safety-related cooling water design temperature at LSCS has been evaluated to be 107 of. Attachment 5 discusses the impact of 107 of UHS cooling water on the design functions of Core Standby Cooling System-Emergency Cooling Water System (CSCS-ECWS) components.

The UHS also provides a source of emergency makeup water for the spent fuel pools and can provide water for fire protection equipment. Loss of UHS inventory due to spent fuel pool makeup and fire protection usage is considered in the UHS analyses for both the temperature response and the inventory response.

There are four temperature measuring instruments used for monitoring the temperature of the lake cooling water provided to the plant. These instruments are located in the circulating water (CW) system inlet thermowells (Le., two per unit), that provide input to the Plant Process Computer (PPC). The outputs of these instruments are used to monitor and trend the temperature of the lake cooling water temperature supplied to the plant via the PPC, and are utilized in verifying the requirement of SR 3.7.3.1 is met at a 24-hour frequency as required by the LSCS Surveillance Frequency Control Program (SFCP). Since the UHS is an integral part of the cooling lake, an excavated pond at the outlet of the cooling lake, UHS temperature is the same as the lake cooling water temperature. Reference 1 documents the fact that the two-channel average uncertainty in the UHS temperature measurement is less than 0.75 of.

The calculated uncertainty for one available loop is +0.74 of and for two available loops is

+0.53 of. It is considered extremely unlikely that three of the four resistance temperature detectors or associated circuitry would be unavailable simultaneously. In the unlikely event this condition were to occur, the 0.75 of allowance for conservatism bounds the instrument uncertainties associated with any combination of operable temperature measurement devices to meet the requirements of SR 3.7.3.1.

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. Weather conditions in the future may continue challenging the current TS limit of s; 101.25 oF.

This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle and to account for recent Page 5 of 21 ATTACHMENT 1 Evaluation of Proposed Change system and Diesel Generator Cooling Water (DGCW) system are the principal systems at LSCS that utilize the UHS to reject heat from safety related plant loads.

The UHS consists of an excavated pond integral with the cooling lake. The volume of the pond is sized to permit the safe shutdown and cooldown of both LSCS units for a 30-day period design basis event with no additional makeup water source. The UHS design basis event includes a failure of the LSCS cooling lake dike resulting in the UHS as the remaining source of cooling water to plant safety systems. The design basis event for the LSCS UHS is a loss of offsite power (LOOP) on both units resulting in all emergency diesel generators running, while one unit experiences an accident (Le., a design basis accident (DBA) loss of coolant accident (LOCA>> while the other unit is shutdown normally. The function of the UHS is to provide cooling of the RHR heat exchangers, diesel generator coolers, Emergency Core Cooing System (ECCS) cubicle area cooling coils, RHR pump seal coolers, and Low Pressure Core Spray (LPCS) pump motor cooling coils. The UHS provides indirect heat rejection for the containment through the RHR heat exchangers. The current maximum safety-related cooling water design temperature at LSCS has been evaluated to be 107 of. Attachment 5 discusses the impact of 107 of UHS cooling water on the design functions of Core Standby Cooling System-Emergency Cooling Water System (CSCS-ECWS) components.

The UHS also provides a source of emergency makeup water for the spent fuel pools and can provide water for fire protection equipment. Loss of UHS inventory due to spent fuel pool makeup and fire protection usage is considered in the UHS analyses for both the temperature response and the inventory response.

There are four temperature measuring instruments used for monitoring the temperature of the lake cooling water provided to the plant. These instruments are located in the circulating water (CW) system inlet thermowells (Le., two per unit), that provide input to the Plant Process Computer (PPC). The outputs of these instruments are used to monitor and trend the temperature of the lake cooling water temperature supplied to the plant via the PPC, and are utilized in verifying the requirement of SR 3.7.3.1 is met at a 24-hour frequency as required by the LSCS Surveillance Frequency Control Program (SFCP). Since the UHS is an integral part of the cooling lake, an excavated pond at the outlet of the cooling lake, UHS temperature is the same as the lake cooling water temperature. Reference 1 documents the fact that the two-channel average uncertainty in the UHS temperature measurement is less than 0.75 of.

The calculated uncertainty for one available loop is +0.74 of and for two available loops is

+0.53 of. It is considered extremely unlikely that three of the four resistance temperature detectors or associated circuitry would be unavailable simultaneously. In the unlikely event this condition were to occur, the 0.75 of allowance for conservatism bounds the instrument uncertainties associated with any combination of operable temperature measurement devices to meet the requirements of SR 3.7.3.1.

Recent summer meteorological conditions have resulted in the TS UHS temperature limit being challenged. These conditions include elevated air temperatures, high humidity, and low wind speed. Weather conditions in the future may continue challenging the current TS limit of s; 101.25 oF.

This license amendment is being sought to allow the TS temperature limit of the cooling water supplied to the plant from the UHS to vary with the diurnal cycle and to account for recent Page 5 of 21

ATTACHMENT I Evaluation of Proposed Change weather data that is more severe than historical weather data used in the current analyses. The proposed TS amendment includes a graph depicting the allowable initial UHS temperature as a function of time of day. Following approval of the proposed change, TS 3.7. 3, Required Actions C. 1 and C.2 would be entered concurrently if the UHS temperature exceeds the allowable UHS temperature at a given time, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months , and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

4.0 TECHNICAL ANALYSIS

The UHS removes heat from both units' reactor cores following the UHS design basis event in which the units are cooled down using Residual Heat Removal (RHR) operation. The function of the UHS is to provide cooling of the RHR heat exchangers, diesel generator (DG) coolers, ECCS cubicle area cooling coils, RHR pump seal coolers, and LPCS pump motor cooling coils.

The RHRSW and DGCW subsystems circulate UHS cooling water through the associated heat exchangers to maintain process temperatures within design limits. The UHS provides indirect heat rejection for the containment through the RHR heat exchangers. Attachment 5 discusses the impact of 107 OF UHS cooling water on the design functions of Core Standby Cooling System - Emergency Cooling Water System (CSCS-ECWS) components.

The drywells for LSCS, Units 1 and 2 are designed for a maximum pressure of 45 psig. The limiting piping rupture inside containment for each unit has been evaluated to be a double-ended guillotine shear of a recirculation line. Peak drywell pressure occurs within approximately 12 seconds of the recirculation line break. During this period of peak drywell pressure the UHS temperature does not impact the drywell pressure response since the pressure increase is rapidly mitigated through the containment design via the drywell floor downcomers and the suppression pool, without any support from the UHS.

As discussed in LSCS Updated Final Safety Analysis Report (UFSAR) Section 6.2.1.1.3.1.1, "Recirculation Line Rupture," the RHR heat exchanger is manually initiated at approximately 600 seconds into the event. As described in Attachment 5, once initiated, the RHR system continues to possess the capability to remove the required accident energy from containment, maintaining the long term suppression pool temperature within limits with a maximum UHS temperature of 107 OF. Impacts on the structural integrity of the UHS operating at 107 OF have been evaluated as acceptable under LSCS Engineering Change (EC) 389677. The consequences of the UHS design basis event remain unchanged because containment parameters, peak accident pressure and suppression pool temperature, remain within design limits.

The safety design bases for UHS are documented in the LSCS UFSAR Section 9.2.6, "Ultimate Heat Sink." In the unlikely event that the cooling lake dike is breached, the submerged pond is designed to provide the UHS for LSCS. All analyses performed assume that the cooling lake dike fails instantaneously concurrent with the UHS design basis event. The UHS is designed in accordance with RG 1.27, Revision 1, which requires a 30-day supply of cooling water be available during the worst period of recorded weather conditions. The basis provided in Regulatory Guide 1.27, Revision 1 and NUREG-0693 was employed for the transient analysis of the LSCS UHS.

Page 6 of 21 ATTACHMENT 1 Evaluation of Proposed Change weather data that is more severe than historical weather data used in the current analyses. The proposed TS amendment includes a graph depicting the allowable initial UHS temperature as a function of time of day. Following approval of the proposed change, TS 3.7.3, Required Actions C.1 and C.2 would be entered concurrently if the UHS temperature exceeds the allowable UHS temperature at a given time, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months , and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

4.0 TECHNICAL ANALYSIS

The UHS removes heat from both units' reactor cores following the UHS design basis event in which the units are cooled down using Residual Heat Removal (RHR) operation. The function of the UHS is to provide cooling of the RHR heat exchangers, diesel generator (DG) coolers, ECCS cubicle area cooling coils, RHR pump seal coolers, and LPCS pump motor cooling coils.

The RHRSW and DGCW subsystems circulate UHS cooling water through the associated heat exchangers to maintain process temperatures within design limits. The UHS provides indirect heat rejection for the containment through the RHR heat exchangers. Attachment 5 discusses the impact of 107 of UHS cooling water on the design functions of Core Standby Cooling System - Emergency Cooling Water System (CSCS-ECWS) components.

The drywells for LSCS, Units 1 and 2 are designed for a maximum pressure of 45 psig. The limiting piping rupture inside containment for each unit has been evaluated to be a double-ended guillotine shear of a recirculation line. Peak drywell pressure occurs within approximately 12 seconds of the recirculation line break. During this period of peak drywell pressure the UHS temperature does not impact the drywell pressure response since the pressure increase is rapidly mitigated through the containment design via the drywell floor downcomers and the suppression pool, without any support from the UHS.

As discussed in LSCS Updated Final Safety Analysis Report (UFSAR) Section 6.2.1.1.3.1.1, "Recirculation Line Rupture," the RHR heat exchanger is manually initiated at approximately 600 seconds into the event. As described in Attachment 5, once initiated, the RHR system continues to possess the capability to remove the required accident energy from containment, maintaining the long term suppression pool temperature within limits with a maximum UHS temperature of 107 of. Impacts on the structural integrity of the UHS operating at 107 of have been evaluated as acceptable under LSCS Engineering Change (EC) 389677. The consequences of the UHS design basis event remain unchanged because containment parameters, peak accident pressure and suppression pool temperature, remain within design limits.

The safety design bases for UHS are documented in the LSCS UFSAR Section 9.2.6, "Ultimate Heat Sink." In the unlikely event that the cooling lake dike is breached, the submerged pond is designed to provide the UHS for LSCS. All analyses performed assume that the cooling lake dike fails instantaneously concurrent with the UHS design basis event. The UHS is designed in accordance with RG 1.27, Revision 1, which requires a 30-day supply of cooling water be available during the worst period of recorded weather conditions. The basis provided in Regulatory Guide 1.27, Revision 1 and NUREG-0693 was employed for the transient analysis of the LSCS UHS.

Page 6 of 21 ATTACHMENT 1 Evaluation of Proposed Change weather data that is more severe than historical weather data used in the current analyses. The proposed TS amendment includes a graph depicting the allowable initial UHS temperature as a function of time of day. Following approval of the proposed change, TS 3.7.3, Required Actions C.1 and C.2 would be entered concurrently if the UHS temperature exceeds the allowable UHS temperature at a given time, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months , and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

4.0 TECHNICAL ANALYSIS

The UHS removes heat from both units' reactor cores following the UHS design basis event in which the units are cooled down using Residual Heat Removal (RHR) operation. The function of the UHS is to provide cooling of the RHR heat exchangers, diesel generator (DG) coolers, ECCS cubicle area cooling coils, RHR pump seal coolers, and LPCS pump motor cooling coils.

The RHRSW and DGCW subsystems circulate UHS cooling water through the associated heat exchangers to maintain process temperatures within design limits. The UHS provides indirect heat rejection for the containment through the RHR heat exchangers. Attachment 5 discusses the impact of 107 of UHS cooling water on the design functions of Core Standby Cooling System - Emergency Cooling Water System (CSCS-ECWS) components.

The drywells for LSCS, Units 1 and 2 are designed for a maximum pressure of 45 psig. The limiting piping rupture inside containment for each unit has been evaluated to be a double-ended guillotine shear of a recirculation line. Peak drywell pressure occurs within approximately 12 seconds of the recirculation line break. During this period of peak drywell pressure the UHS temperature does not impact the drywell pressure response since the pressure increase is rapidly mitigated through the containment design via the drywell floor downcomers and the suppression pool, without any support from the UHS.

As discussed in LSCS Updated Final Safety Analysis Report (UFSAR) Section 6.2.1.1.3.1.1, "Recirculation Line Rupture," the RHR heat exchanger is manually initiated at approximately 600 seconds into the event. As described in Attachment 5, once initiated, the RHR system continues to possess the capability to remove the required accident energy from containment, maintaining the long term suppression pool temperature within limits with a maximum UHS temperature of 107 of. Impacts on the structural integrity of the UHS operating at 107 of have been evaluated as acceptable under LSCS Engineering Change (EC) 389677. The consequences of the UHS design basis event remain unchanged because containment parameters, peak accident pressure and suppression pool temperature, remain within design limits.

The safety design bases for UHS are documented in the LSCS UFSAR Section 9.2.6, "Ultimate Heat Sink." In the unlikely event that the cooling lake dike is breached, the submerged pond is designed to provide the UHS for LSCS. All analyses performed assume that the cooling lake dike fails instantaneously concurrent with the UHS design basis event. The UHS is designed in accordance with RG 1.27, Revision 1, which requires a 30-day supply of cooling water be available during the worst period of recorded weather conditions. The basis provided in Regulatory Guide 1.27, Revision 1 and NUREG-0693 was employed for the transient analysis of the LSCS UHS.

Page 6 of 21

ATTACHMENT 1 Evaluation of Proposed Change Although, the LSCS UFSAR, Appendix B states that LSCS complies with the requirements of RG 1.27, Revision 1, previous revisions of the LSCS UHS design analysis have included the effects on the UHS model using the worst five-day period followed by the worst single-day and then the worst 30-day period (i.e., 5-1-30). Use of the 5-1-30 approach resulted in allowable initial temperatures that were 0.3 OF to 0.6 OF higher than those determined using RG 1.27, Revision 1 methodology that uses the worst 1-day followed by the worst 30-day period (i.e., 1-30). Although the use of RG 1.27, Revision 2 methodology provided additional operating margin, LSCS did not elect to alter its commitment to RG 1.27, Revision 1.

Verification of the temperature of the water supplied to the plant from the cooling lake ensures that the temperature-related aspects of the heat removal capabilities of the RHRSW Subsystem and DGCW Subsystem are within the assumptions of the design basis event analyses. To ensure that the maximum post-accident temperature (i.e., 107 °F) of water supplied to the plant is not exceeded, the temperature during normal plant operation must be maintained less than the TS limit. The proposed TS limit accounts for the UHS design requirement that it provide adequate cooling water supply to the plant for 30 days without makeup, while taking into account plant accident energy during the worst historical weather conditions with the worst case sedimentation allowed by TS (i.e., 1.5 feet).

The LSCS CSCS pond sediment deposition surveillance (i.e., SR 3.7.3.2) is conducted at a biennial frequency in accordance with the LSCS Surveillance Frequency Control Program. The surveillance is performed by certified hydrographers who assess the pond condition in accordance with the Class I hydrographic survey standards established by the U.S. Army Corps of Engineers. The accuracy of these surveys is estimated to be approximately + 0.2 ft. Once the CSCS pond survey is complete, the results are reviewed and approved by LSCS Engineering in accordance with LSCS Procedure LTS-1 000-4, "CSCS Pond Surveillance."

In response to a concern with the volume of the UHS determined using original 1981 hydrographic survey results, identified in 1997, a new hydrographic survey using more accurate instrumentation was performed. The UHS surface area and volume determinations resulting from the 1997 survey met design and licensing basis requirements. These 1997 survey results are therefore now used as the baseline for comparing subsequent survey results and determining compliance with Technical Specification Surveillance Requirements. The most current biennial UHS pond sediment deposition surveillance, performed in 2010, indicates the sediment deposition changes since the previous survey in 2008 have been insignificant, and the largest difference as compared to 1997 and 1999 results is 0.4 feet (ft) in certain areas in the southeast quadrant of the UHS. Also, as compared to 1997 and 1999 results there is minimal depth change (i.e., < 0.4 ft) throughout the UHS bottom with the exception of some very localized areas with sediment deposition of approximately one to two feet mainly at the CSCS outfall structure and along the sloped embankment areas of the UHS. Furthermore, when these areas were compared to 2006 and 2008 data, changes were negligible (i.e., +/- 0.1 feet).

The average sediment deposition across the UHS has not changed appreciably between the biennial sediment deposition surveillances. The next sediment deposition hydrographic survey is currently scheduled to be performed in July 2012.

Based on the historical UHS sedimentation trends discussed above, no change to the biennial frequency of the sediment deposition surveillance is being proposed.

Page 7 of 21 ATTACHMENT 1 Evaluation of Proposed Change Although, the LSCS UFSAR, Appendix B states that LSCS complies with the requirements of RG 1.27, Revision 1, previous revisions of the LSCS UHS design analysis have included the effects on the UHS model using the worst five-day period followed by the worst single-day and then the worst 30-day period (i.e., 5-1-30). Use of the 5-1-30 approach resulted in allowable initial temperatures that were 0.3 of to 0.6 of higher than those determined using RG 1.27, Revision 1 methodology that uses the worst 1-day followed by the worst 30-day period (Le., 1-30). Although the use of RG 1.27, Revision 2 methodology provided additional operating margin, LSCS did not elect to alter its commitment to RG 1.27, Revision 1.

Verification of the temperature of the water supplied to the plant from the cooling lake ensures that the temperature-related aspects of the heat removal capabilities of the RHRSW Subsystem and DGCW Subsystem are within the assumptions of the design basis event analyses. To ensure that the maximum post-accident temperature (Le., 107 OF) of water supplied to the plant is not exceeded, the temperature during normal plant operation must be maintained less than the TS limit. The proposed TS limit accounts for the UHS design requirement that it provide adequate cooling water supply to the plant for 30 days without makeup, while taking into account plant accident energy during the worst historical weather conditions with the worst case sedimentation allowed by TS (Le., 1.5 feet).

The LSCS CSCS pond sediment deposition surveillance (Le., SR 3.7.3.2) is conducted at a biennial frequency in accordance with the LSCS Surveillance Frequency Control Program. The surveillance is performed by certified hydrographers who assess the pond condition in accordance with the Class I hydrographic survey standards established by the U.S. Army Corps of Engineers. The accuracy of these surveys is estimated to be approximately + 0.2 ft. Once the CSCS pond survey is complete, the results are reviewed and approved by LSCS Engineering in accordance with LSCS Procedure L TS-1 000-4, "CSCS Pond Surveillance."

In response to a concern with the volume of the UHS determined using original 1981 hydrographic survey results, identified in 1997, a new hydrographic survey using more accurate instrumentation was performed. The UHS surface area and volume determinations resulting from the 1997 survey met design and licensing basis requirements. These 1997 survey results are therefore now used as the baseline for comparing subsequent survey results and determining compliance with Technical Specification Surveillance Requirements. The most current biennial UHS pond sediment deposition surveillance, performed in 2010, indicates the sediment deposition changes since the previous survey in 2008 have been insignificant, and the largest difference as compared to 1997 and 1999 results is 0.4 feet (ft) in certain areas in the southeast quadrant of the UHS. Also, as compared to 1997 and 1999 results there is minimal depth change (Le., < 0.4 ft) throughout the UHS bottom with the exception of some very localized areas with sediment deposition of approximately one to two feet mainly at the CSCS outfall structure and along the sloped embankment areas of the UHS. Furthermore, when these areas were compared to 2006 and 2008 data, changes were negligible (Le., +/- 0.1 feet).