RS-11-042, Request for License Amendment to Technical Specifications Section 3.7.3, Ultimate Heat Sink.

Request for License Amendment to Technical Specifications Section 3.7.3, Ultimate Heat Sink.

ML111290197
Person / Time
Site:	LaSalle
Issue date:	05/06/2011
From:	Hansen J Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-11-042
Download: ML111290197 (20)

Text

RS-1 1-042 10 CFR 50.90 May 6, 2011 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 Technical Specifications Section 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 - 1 1 and NPF- 1 8 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 Core Standby Cooling System (CSCS) pond (i.e., the Ultimate Heat Sink (UHS)) is <_ 101.25 OF and SR 3.7.3.2 verifies the sediment level in the CSCS pond is <_ 1.5 feet. If the sediment level in the CSCS pond cannot be restored to <_ 1.5 feet within 90 days, or 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 <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

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. Weather conditions in the future may result in the temperature of the CSCS pond challenging the current TS limit of 101.25 OF.

This license amendment is being sought to limit the CSCS pond sediment level to <_ 1.0 feet, which will reduce the post- accident heatup in the CSCS pond from 2.0 OF to 1.3 OF, and allow an increase of the TS temperature limit of the cooling water supplied to the plant from the CSCS pond to s 101.95 O F. If the sediment level in the CSCS pond cannot be restored to <_ 1.0 feet within 90 days, or if the temperature of the cooling water supplied to the plant from the CSCS pond exceeds 101.95 O F, Required Actions 8.1 and 8.2 would be entered concurrently, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

The proposed change is supported by a Design Analysis of the maximum allowable UHS temperature for <_ 1.0 feet of sedimentation depth, and historical surveillance results for average sedimentation depth.

May 6, 2011 U. S. Nuclear Regulatory Commission Page 2 The attached amendment request is subdivided as follows:

Attachment 1 provides an evaluation of the proposed change.

Attachment 2 provides the current TS pages with the proposed changes indicated with markups.

Attachment 3 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.

EGC requests approval of the proposed change by May 6, 2012, 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.

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).

Should you have any questions concerning this letter, please contact Mr. Mitch Mathews at (630) 657-2819.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 6th day of May 2011.

Jeffrey. Hansen Manager, Licensing and Regulatory Affairs : Evaluation of Proposed Change : Mark-up of Proposed Technical Specifications Page Change : Markup of Proposed Technical Specifications Bases Page Changes - For Information Only cc: Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT 1 Evaluation of Proposed Change

Subject:

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

2.0 PROPOSED CHANGE

S

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 11

ATTACHMENT 1 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-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 Core Standby Cooling System (CSCS) pond (i.e., the Ultimate Heat Sink (UHS)) is _< 101.25 IF and SR 3.7.3.2 verifies that the sediment level in the CSCS pond is <_ 1.5 feet. If the sediment level in the CSCS pond cannot be restored to <_ 1.5 feet within 90 days, or if the UHS indicated temperature exceeds 101.25 OF, TS 3.7.3 Required Actions B.1 and B.2 would be entered, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

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. Weather conditions in the future may result in the temperature of the CSCS cooling pond challenging the current TS limit of <_ 101.25 OF.

This license amendment is being sought to limit the sediment level in the CSCS pond to

<_ 1.0 feet, which ensures a higher volume of water is available in the CSCS pond. The higher volume of water reduces the amount of post-accident heatup in the CSCS pond from 2.0 OF to 1.3 OF, which provides for an increase of the TS temperature limit of the cooling water supplied to the plant from the CSCS pond to <_ 101.95 OF. If the sediment level in the CSCS pond cannot be restored to <_ 1.0 feet within 90 days, or if the UHS indicated temperature exceeds 101.95 OF, Required Actions B.1 and B.2 would be entered concurrently, and both units would be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

The proposed reduction in the allowable sediment level in the CSCS pond results in greater volume of cooling water in the CSCS pond available to cool plant loads. This greater volume of cooling water reduces the post-accident temperature rise and provides for an increase in the allowable cooling water temperature supplied to the plant from the CSCS pond. Consequently, there is no change in the containment pressure response, Loss of Coolant Accident (LOCA) and non-LOCA analyses, and there is no increase in the risk associated with the post-accident heat removal. In addition, there are no identified adverse influences on risk associated with any other Design Basis Accident (DBA) and therefore a Probabilistic Risk Analysis (PRA) assessment is not necessary for this change.

This proposed change is supported by a Design Analysis of the maximum allowable UHS temperature for <_ 1.0 feet of CSCS pond sedimentation (i.e., Reference 1) and historical surveillance results for average CSCS pond sedimentation depth.

Page 2 of 11

ATTACHMENT 1 Evaluation of Proposed Change

2.0 PROPOSED CHANGE

S The proposed changes to SR 3.7.3.1 and SR 3.7.3.2 are as follows:

U S 3.7.3 1T URVEICLA CE FREQUENCY Surveillance Fr Cart

.7.3.2 Verify seimert leve' is ^ In accordance intake flume arc the CSCS with the Surveillance Frequency Control Rrogr

3.0 BACKGROUND

The UHS provides a heat sink for process and operating heat from safety related components during a transient or accident, as well as during normal operation. The Residual Heat Removal Service Water (RHRSW) 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 CSCS pond integral with the cooling lake. The volume of the CSCS pond is sized to permit the safe shutdown and cooldown of both LSCS units for a 30-day period with no additional makeup water source available for normal and accident conditions. The UHS is the heat sink for heat removed from both units' reactor cores following all postulated accidents and anticipated operational occurrences in which the units are cooled down and Residual Heat Removal (RHR) is placed in service. The function of the CSCS pond is to provide for cooling of the RHR heat exchangers, diesel generator coolers, CSCS cubicle area cooling coils, RHR pump seal coolers, and Low Pressure Core Spray (LPCS) pump motor cooling coils. The CSCS pond provides indirect heat rejection for the containment through the RHR heat exchangers. The CSCS pond also provides a backup source of emergency makeup water for spent fuel pool cooling and can provide water for fire protection equipment. Neither the ability to provide emergency makeup water for spent fuel pool cooling nor fire protection is limited by heat rejection considerations. The operating limits for heat rejection capability are based on conservative heat transfer analyses for the design basis LOCA.

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ATTACHMENT 1 Evaluation of Proposed Change There are four temperature measuring instruments used for monitoring the temperature of the CSCS temperature 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 UHS cooling water temperature supplied to the plant from the CSCS pond via the PPC, and are utilized in verifying the requirement of SR 3.7.3.1 is met.

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. Weather conditions in the future may result in the temperature of the CSCS cooling pond challenging the current TS limit of _<101.25 OF.

This license amendment is being sought to reduce the allowable sediment level of the CSCS pond from < 1.5 feet to 5 _ 1.0 feet, which reduces the amount of post-accident heatup in the CSCS pond from 2 .0 OF to 1. 3 OF, and provides for an increase of the TS temperature limit of the cooling water supplied to the plant from the CSCS pond from < 101.25 OF to <_ 101.95 OF.

This change ensures a greater volume of water will be available within the UHS to support the cooling of post - accident heat loads for 30 days following the design basis accident. The reduction in the permissible sedimentation level does not affect the results of the heat removal calculations that verify that the post accident heat loads can be removed for 30 days without challenging the design bases of the mitigation systems. Following approval of the proposed change, TS 3.7. 3, Required Actions B.1 and B.2 would be entered if the sediment level in the CSCS pond cannot be restored to <_ 1.0 feet within 90 days, or if the UHS temperature exceeds 101.95 O F, requiring both LSCS units to be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

4.0 TECHNICAL ANALYSIS

The UHS removes heat from both units' reactor cores following all postulated accidents and anticipated operational occurrences in which the units are cooled down and placed in Residual Heat Removal (RHR) operation. The function of the CSCS pond is to provide for cooling of the RHR heat exchangers, Diesel Generator (DG) coolers, CSCS cubicle area cooling coils, RHR pump seal coolers, and Low Pressure Core Spray (LPCS) pump motor cooling coils. The CSCS pond provides indirect heat rejection for the containment through the RHR heat exchangers.

The safety design bases for UHS are documented in the LSCS Updated Final Safety Analysis Report (UFSAR) Section 9.2.6. In the unlikely event that the cooling lake dike is breached, the submerged pond (i.e., the CSCS cooling pond) is designed to provide the UHS for LSCS. The UHS is designed in accordance with Regulatory Guide 1.27, "Ultimate Heat Sink for Nuclear Power Plants," Revision 1, dated March 1974, which requires a 30-day supply of cooling water in the UHS. The basis provided in Regulatory Guide 1.27 was employed for the temperature analysis of the LSCS UHS to implement General Design Criteria 2, "Design bases for protection against natural phenomena," and Criteria 44, "Cooling water," of Appendix A to 10 CFR Part 50, "General Design Criteria for Nuclear Power Plants." Compliance with GDC Criteria 2 and 44 is discussed in LSCS UFSAR Sections 3.1.2.1.2 and 3.1.2.4.15, respectively.

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ATTACHMENT 1 Evaluation of Proposed Change Verification of the temperature of the water supplied to the plant from the CSCS pond (i.e., the UHS) in conjunction with verification of CSCS pond sedimentation levels ensures that the heat removal capabilities of the RHRSW System and DGCW System are within the assumptions of the Design Basis Analysis. To ensure that the maximum post-accident temperature (i.e., 104 °F) of water supplied to the plant is not exceeded, the temperature during normal plant operation must be maintained less than the TS limit. This TS limit accounts for the CSCS pond design requirement that it provide adequate cooling water supply to the plant for 30 days without makeup, while taking into account plant decay heat during the worst historical weather conditions. In addition, since the lake temperature follows a diurnal cycle (i.e., it heats up during the day and cools off at night), the allowable initial UHS temperature varies with the time of day. The allowable initial UHS temperature, based on sediment level and the time of day have been determined by analysis (i.e., Reference 1). The limiting initial UHS temperature determined in this analysis ensures the maximum post-accident temperature of 104 OF is not exceeded. This calculated initial temperature is an analytical limit that does not include instrument uncertainty or additional margin.

The proposed increase in the allowable indicated temperature is based on decreasing the limit on sedimentation in the CSCS pond. The most current sedimentation surveillance, performed in 2010, indicated that the average sediment depth is less than six inches, and that changes since previous surveys dating back to 1997 have been insignificant. The survey results from 1997 were used to determine the volume of the UHS versus the original survey data from 1981. This is due to the fact that the 1997 survey was performed utilizing instrumentation with higher accuracy than the instrumentation that was used for the 1981 survey. The UHS surface area and volume determinations resulting from the 1997 survey met all 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 TS SRs.

The rate of temperature change of the UHS is relatively slow. Additionally, the UHS temperature is constantly available for viewing and trending in the Main Control Room using the PPC. This allows an increase in the monitoring frequency of the parameter as it approaches the TS limit. The PPC can display each of the four temperatures as a single point and the average for each unit. In addition, each of the CW inlet temperature data points are set to provide a PPC alarm at the TS limit. The alarm consists of an audible alert and an associated message on the PPC. Upon approval of the proposed change, the individual PPC computer alarm points will be set to the new limit of 101.95 OF.

The Design Analysis (i.e., Reference 1) demonstrates that for a sedimentation depth of one foot or less, an initial UHS temperature of _< 102.7 OF will still maintain the CSCS pond temperature within the maximum 30-day post-accident temperature limit of 104 OF. A single instrument channel uncertainty of 0.74 IF as discussed in Reference 2 yields a limiting initial UHS temperature limit of _< 101.96 IF. This limiting initial temperature remains bounded by the proposed TS SR 3.7.3.1 limit of < 101.95 OF.

The proposed change will not result in a change in the actual peak post-accident UHS temperature of 104 IF, nor will it result in a change to the containment pressure response or LOCA and non-LOCA analyses. Further, there is no increase in risk associated with the post-Page 5 of 11

ATTACHMENT 1 Evaluation of Proposed Change accident heat removal. No identified adverse influences on risk associated with any other DBA exist; therefore, a PRA assessment is not necessary for this change.

This license amendment is being sought to reduce the allowable sediment level of the CSCS pond from <_ 1.5 feet to < 1.0 feet, which ensures a greater volume of cooling water is available to cool plant loads. The greater volume of water reduces the amount of post-accident heatup in the CSCS pond from 2.0 OF to 1.3 OF and provides for an increase of the TS temperature limit for the cooling water supplied to the plant from the CSCS pond from 5 101.25 IF to <_ 101.95 OF.

Increasing the allowable indicated UHS temperature to <_ 101.95 IF will reduce the likelihood of the necessity to impose simultaneous and unnecessary transients on two large reactors.

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration 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, Units 1 and 2 (LSCS). Surveillance Requirement (SR) 3.7.3.1 verifies the cooling water temperature supplied to the plant from the Core Standby Cooling System (CSCS) pond (i.e., the Ultimate Heat Sink (UHS)) is !5 101.25 IF and SR 3.7.3.2 verifies that the CSCS pond sediment level is <_ 1.5 feet. Currently, if the sediment level in the CSCS pond exceeds 1.5 feet, or if the temperature of the cooling water supplied to the plant from the CSCS pond exceeds 101.25 OF, the UHS must be declared inoperable in accordance with TS 3.7.3. TS 3.7.3 Required Action B.1, requires that both units be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and Required Action B.2 requires that both units be placed in Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

This license amendment is being sought to limit the sediment level in the CSCS pond to

<_ 1.0 feet, which allows an increase to the TS temperature limit of the cooling water supplied to the plant from the CSCS pond to _< 101.95 I F. If the sediment level in the CSCS pond cannot be restored to <_ 1.0 feet within 90 days, or if the indicated UHS temperature exceeds 101.95 OF, TS 3.7. 3 Required Actions B.1 and B.2 would be entered, and both units would be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

Since the proposed limit to CSCS pond sediment level maximizes the volume of cooling water available in the CSCS pond, which reduces CSCS pond heatup and allows for an increase in the allowable cooling water temperature supplied to the plant from the CSCS pond, there is no change in the containment pressure response, Loss of Coolant Accident (LOCA) and non-LOCA analyses, and there is no increase in risk associated with the post-accident heat removal. In addition, there are no identified adverse influences on risk associated with any other Design Basis Accident (DBA) and; therefore, a Probabilistic Risk Analysis (PRA) assessment is not required for this change.

This proposed change is supported by an engineering Design Analysis, L-002457, Revision 6, "LaSalle County Station Ultimate Heat Sink Analysis," dated April 1, 2011 (i.e., Reference 1).

Page 6 of 11

ATTACHMENT 1 Evaluation of Proposed Change According to 10 CFR 50.92, "Issuance of amendment," paragraph (c), a proposed amendment to an operating license involves no significant hazards consideration if operation of the facility in accordance with the proposed amendment would not:

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety.

In support of this determination, an evaluation of each of the three criteria set forth in 10 CFR 50. 92 is provided below:

1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed change will reduce the allowed sedimentation in the Core Standby Cooling System (CSCS) pond from <_ 1.5 feet to <_ 1.0 feet, which allows the indicated temperature of the cooling water supplied to the plant from the CSCS pond to be increased from :< 101.25 IF to <_ 101.95 OF based on reduction in post-accident heatup from 2.0 OF to 1.3 OF due to a resulting higher volume of cooling water available in the CSCS pond.

Analyzed accidents are assumed to be initiated by the failure of plant structures, systems, or components. An inoperable ultimate heat sink (UHS) is not considered as an initiator of any analyzed events. As such, there is not a significant increase in the probability of a previously evaluated accident. Allowing the UHS to operate with a lower allowance for sedimentation at a higher allowable indicated temperature, will not affect the failure probability of any equipment. The current heat analysis calculations of record for LSCS, Units 1 and 2, assume a UHS post-accident peak inlet temperature of 104 °F.

The proposed temperature increase is based on an adjustment to post accident UHS heatup due to restricting the level of sedimentation allowed in the CSCS pond. The current analysis bounds the proposed change. This higher allowable indicated temperature does not impact the loss of coolant accident (LOCA) Peak Clad Temperature Analysis, LOCA Containment Analysis or the non-LOCA analyses; therefore, continued operation with a UHS temperature > 101.25 IF but <_ 101.95 OF will not increase the consequences of an accident previously evaluated in the Updated Final Safety Analysis Report (UFSAR).

Based on the information discussed above, the reduction in the allowable CSCS pond sedimentation depth to <_ 1.0 feet in concert with an allowable UHS temperature of

< 101.95 O F, has no effect on the results of the design basis event, and will continue to assure that each required heat exchanger can perform its safety function. The plant heat exchangers will continue to provide sufficient cooling for the heat loads during the Page 7 of 11

ATTACHMENT I Evaluation of Proposed Change most severe 30-day period. Since the proposed change has no impact on any analyzed accident, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No.

The proposed change involves reducing the allowable sedimentation of the CSCS pond from <_ 1.5 feet to < 1.0 feet. This proposed action will not alter the manner in which equipment is operated, nor will the functional demands on credited equipment be changed. Reducing the CSCS pond sedimentation limit does not introduce any new or different modes of plant operation, nor does it affect the operational characteristics of any safety-related equipment or systems; as such, no new failure modes are being introduced. The proposed action does not alter assumptions made in the safety analysis.

Increasing the allowable indicated temperature of the cooling water supplied to the plant from the CSCS pond from <_ 101.25 OF to <_ 101.95 OF has no impact on safety related systems. The plant is designed such that the residual heat removal (RHR) pumps on the unit undergoing the LOCH/ loss of offsite power (LOOP) conditions would start upon the receipt of a signal, and would load onto their respective Emergency Diesel Generators' emergency bus during the LOOP event. The increase in the allowable indicated temperature of the cooling water supplied to the plant from the CSCS pond will not require operation of additional RHR pumps; therefore, system operation is unaffected by the proposed change.

Based on the above information, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. Does the proposed change involve a significant reduction in a margin of safety?

Response: No.

The proposed change reduces the allowable sedimentation levels in the CSCS pond to

<_ 1.0 feet and consequently allows an increase in the allowable indicated temperature of the cooling water supplied to the plant from the CSCS pond to < _ 101.95 OF. The margin of safety is determined by the design and qualification of the plant equipment, the operation of the plant within analyzed limits, and the point at which protective or mitigative actions are initiated. The proposed action does not impact these factors as the analyzed peak post accident inlet temperature of the UHS is unaffected based on the reduced allowable sediment depth in the CSCS pond. This change is supported by an engineering analysis that determined that existing post-accident CSCS pond heatup rates calculations were overly conservative based on observed CSCS pond sedimentation being significantly less than predicted. No setpoints are affected, and no other change is being proposed in the plant operational limits as a result of this change.

All accident analysis assumptions and conditions will continue to be met. Adequate Page 8 of 11

ATTACHMENT 1 Evaluation of Proposed Change design margin is available to ensure that the required margin of safety is not significantly reduced.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above evaluation, Exelon Generation Company, LLC concludes that the proposed amendment presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c).

5.2 Applicable Regulatory Requirements/Criteria The design of the UHS satisfies the requirements of 10 CFR 50.36, "Technical Specifications,"

paragraph (c)(2)(ii), Criterion 3. This criterion states the following:

(ii) A Technical Specification Limiting Condition for Operation (TS LCO) of a nuclear reactor must be established for each item meeting one or more of the following criteria:

Criterion 3. A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.

The proposed change does not remove or relocate the CSCS pond temperature or sedimentation limits from TS 3.7 .3, "Ultimate Heat Sink;" therefore, Criterion 3 of 10 CFR 50.36(c)(2)(ii) continues to be met.

General Design Criteria 2, "Design bases for protection against natural phenomena," and General Design Criteria 44, "Cooling water," of Appendix A to 10 CFR Part 50, "General Design Criteria for Nuclear Power Plants," provides design considerations for the UHS. Regulatory Guide 1.27, "Ultimate Heat Sink for Nuclear Power Plants," Revision 1, dated March 1974, provides an acceptable approach for satisfying this criterion. The basis provided in Regulatory Guide 1.27, Revision 1, was employed for the temperature analysis of the LSCS UHS.

The reduction in the allowable sedimentation of the CSCS pond from <_ 1.5 feet to <_ 1.0 feet does not affect the results of the heat removal calculations that ensure the post accident heat loads can be safely cooled for 30 days following an accident without challenging the design bases of the mitigation systems.

Since the proposed temperature increase is based on a reduction of the post-accident heatup of the CSCS pond due to limiting the allowable CSCS pond sedimentation, there is no change in the containment pressure response, LOCA and non-LOCA analyses. In addition, there are no identified adverse influences on risk associated with any other Design Basis Accident (DBA) and therefore, a Probabilistic Risk Analysis (PRA) assessment is not required for this change.

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ATTACHMENT I Evaluation of Proposed Change 6.0 ENVIRONMENTAL EVALUATION EGC has evaluated this proposed operating license amendment consistent with the criteria for identification of licensing and regulatory actions requiring environmental assessment in accordance with 10 CFR 51.21, "Criteria for and identification of licensing and regulatory actions requiring environmental assessments." EGC has determined that this proposed change meets the criteria for a categorical exclusion set forth in paragraph (c)(9) of 10 CFR 51.22, "Criterion for categorical exclusion; identification of licensing and regulatory actions eligible for categorical exclusion or otherwise not requiring environmental review," and as such, has determined that no irreversible consequences exist in accordance with paragraph (b) of 10 CFR 50.92, "Issuance of amendment." This determination is based on the fact that this change is being proposed as an amendment to the license issued pursuant to 10 CFR 50, "Domestic Licensing of Production and Utilization Facilities," which changes a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, "Standards for Protection Against Radiation," or which changes an inspection or a surveillance requirement, and the amendment meets the following specific criteria:

(I) The amendment involves no significant hazards consideration.

As demonstrated in Section 5.1, "No Significant Hazards Consideration," the proposed change does not involve any significant hazards consideration.

(ii) There is no significant change in the types or significant increase in the amounts of any effluent that may be released offsite.

The proposed change does not result in an increase in power level, does not increase the production nor alter the flow path or method of disposal of radioactive waste or byproducts. The proposed action would allow the operation of LSCS Units 1 and 2 with an increase in the allowable indicated temperature of the cooling water supplied to the plant from the CSCS pond up to < 101.95 °F; however, all accident analyses limits are met. It is expected that all plant equipment would operate as designed in the event of an accident to minimize the potential for any leakage of radioactive effluents; thus, there will be no change in the amounts of radiological effluents released offsite.

Based on the above evaluation, the proposed change will not result in a significant change in the types or significant increase in the amounts of any effluent released offsite.

) There is no significant increase in individual or cumulative occupational radiation exposure.

There is no net increase in individual or cumulative occupational radiation exposure due to the proposed change. The proposed action will not change the level of controls or methodology used for processing of radioactive effluents or handling of solid radioactive waste, nor will the proposed action result in any change in the normal radiation levels within the plant.

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ATTACHMENT I Evaluation of Proposed Change Based on the above information, there will be no increase in individual or cumulative occupational radiation exposure resulting from this change.

7.0 REFERENCES

Design Analysis L-002457, Rev. 6, "LaSalle County Station Ultimate Heat Sink Analysis," dated April 1, 2011

2. Letter from S. P. Sands (U. S. NRC) to C. M. Crane (EGC), "LaSalle County Station, Units 1 and 2 - Issuance of Amendments Re: Technical Specification 3.7.3 Ultimate Heat Sink Request for Processing on an Emergency Basis (TAC Nos. MD6014 and MD6015)," dated August 2, 2007 Page 11 of 11

ATTACHMENT 2 LASALLE COUNTY STATION UNITS 1 and 2 Docket Nos. 50-373 and 50-374 License Nos. NPF-11 and NPF-18 Markup of Proposed Technical Specifications Page Changes REVISED TS PAGE 3.7.3-2

UHS 3.7.3 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.3.1 Verify cooling water temperature supplied In accordance to the plant from the CSCS pond is with the

°F. Surveillance Frequency 101.95°F Control Program SR 3.7.3.2 Verify sediment level is ft in the In accordance intake flume and the CSCS pond with the Surveillance 1 0 Frequency Control Program SR 3.7.3.3 Verify CSCS pond bottom elevation is In accordance

<_ 686.5 ft. with the Surveillance Frequency Control Program LaSalle 1 and 2 3.7.3-2 Amendment No.-2°

ATTACHMENT 3 LASALLE COUNTY STATION UNITS 1 and 2 Docket Nos. 50-373 and 50-374 License Nos. NPF-11 and NPF-18 Markup of Proposed Technical Specifications Bases Page Changes REVISED TS BASES PAGES B 3.7.3-2 B 3.7.3-3 B 3.7.3-4 B 3.7.3-5

UHS B 3.7.3 BASES APPLICABLE The UHS post-accident temperature is based on heat removal SAFETY ANALYSES calculations (Ref. 5) that analyze for a maximum allowable (continued) post-accident inlet cooling water temperature of 104°F. To account for the worst-case scenario and to apply conservatism, the post-accident CSCS pond cooling water L ____2i_

temperature maximum of 44.

temperature of 104°F consists f the CSCS pond TS OF plu OF for transient heat up plus 0.75 ° F to account fo instrument uncertainty (Ref. 6). 101.95°F There are four temperature measuring devices located in the Circulating Water inlet thermowells (i.e., two per unit).

The 0.75°F allowance bounds the instrument uncertainty associated with any combination of operable temperature measurement devices.

The UHS satisfies Criterion 3 of 10 CFR 50.36(c)(2)(ii).

101.95°F LCO OPERABILITY of the UHS is based on a maximum wate temperature being supplied to the plant of 441-.-2--&OF and a minimum pond water level at or above elevation 690 ft mean sea level. In addition, to ensure the volume of water available in the CSCS pond is sufficient to maintain adequate long term cooling, sediment deposition (in the intake flume and in the pond) must be <_ ft and CSCS pond bottom elevation must be <_ 686.5 ft.

1.0 APPLICABILITY In MODES 1, 2, and 3, the UHS is required to be OPERABLE to support OPERABILITY of the equipment serviced by the UHS, and is required to be OPERABLE in these MODES.

In MODES 4 and 5, the OPERABILITY requirements of the UHS are determined by the systems it supports. Therefore, the requirements are not the same for all facets of operation in MODES 4 and 5. The LCOs of the systems supported by the UHS will govern UHS OPERABILITY requirements in MODES 4 and 5.

(continued)

LaSalle 1 and 2 B 3.7.3-2 Revision

UHS B 3.7.3 BASES (continued)

ACTIONS A_1 If the CSCS pond is inoperable, due to sediment deposition ft (in the intake flume, CSCS pond, or both) or the pond bottom elevation > 686.5 ft, action must be taken to restore the inoperable UHS to an OPERABLE status within 90 1.0 days. The 90 day Completion Time is reasonable based on the low probability of an accident occurring during that time, historical data corroborating the low probability of continued degradation (i.e., further excessive sediment deposition or pond bottom elevation changes) of the CSCS pond during that time, and the time required to complete the Required Action.

B.1 and B.2 If the CSCS pond cannot be restored to OPERABLE status within the associated Completion Time, or the CSCS pond is determined inoperable for reasons other than Condition A (e.g., inoperable due to the temperature of the cooling 101.95°F water supplied to the plant from the CSCS pond > 1 OF, corrected for sediment level and time of day), the unit must be placed in a MODE in which the LCO does not apply. To achieve this status, the unit must be placed in at least MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in MODE 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.

SURVEILLANCE SR 3.7.3.1 REQUIREMENTS Verification of the temperature of the water supplied to the plant from the CSCS pond ensures that the heat removal capabilities of the RHRSW System and DGCW System are within the assumptions of the DBA analysis. To ensure that the maximum post-accident temperature of water supplied to the plant is not exceeded (i.e., 104°F determined in Ref. 4),

101.95°F the temperature during normal plant operation must be

<- °F (Ref. 3). This is to account for the CSCS pond design requirement that it provide adequate cooling water supply to the plant (i.e., temperature <_ 104°F) for 30 days (continued)

LaSalle 1 and 2 B 3.7.3-3 Revision

UHS B 3.7.3 BASES SURVEILLANCE SR 3.7.3.1 (continued)

REQUIREMENTS (continued) without makeup, while taking into account solar heat loads and plant decay heat during the worst historical weather conditions. In addition, since the lake temperature follows a diurnal cycle (it heats up during the day and cools off at night), the allowable initial UHS temperature varies with the time of day. The allowable initial UHS temperatures, based on the actual sediment level and the time of day have been determined by analysis (Ref. 5). The limiting initial 7°F UHS temperature of- 1 '°F determined in this analysis 102 / I ensures the maximu post-accident temperature of 104°F is not exceeded. These temperatures are analytical limits that do not include instrument uncertainty or additional margin.

For example, if the lake temperature uncertainty and additional margin are determined to be 0.5°F, the limiting initial UHS temperature becomeso This limiting

^V 2 . 2 0 C I initial temperature remains bounded by the SR 3.7.3.1 limit of < 441-.-^OF. The Surveillance Frequency is controlled under he Surveillance Frequency Control Program.

101.95°F I-J SR 3.7.3.2 This SR ensures adequate long term (30 days) cooling can be maintained, by verifying the sediment level in the intake flume and the CSCS pond is < _ feet. Sediment level is xl= 1.0 determined by a series of sounding cross-sections compared to as-built soundings. The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

SR 3.7.3.3 This SR ensures adequate long term (30 days) cooling can be maintained, by verifying the CSCS pond bottom elevation is

<_ 686.5 feet. The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

(continued)

LaSalle 1 and 2 B 3.7.3-4 Revision

UHS B 3.7.3 BASES (continued)

REFERENCES 1. Regulatory Guide 1.27, Revision , ^] arch 1974

2. UFSAR, Section 9.2.1.

1

3. UFSAR, Section 9.2.6.

4. EC 334017, Rev. 0, "Increased Cooling Water Temperature Evaluation to a New Maximum Allowable of 104°F."

5. L-002457, Rev. , "LaSalle County Station Ultimate Heat Sink Analysis."

6. L-003230, Rev. , "CW Inlet Temperature Uncertainty Analysis."

LaSalle 1 and 2 B 3.7.3-5 Revision