RS-20-104, Supplement to the Request for a License Amendment Technical Specification 3.7.3, Ultimate Heat Sink

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

ML20259A454
Person / Time
Site:	LaSalle
Issue date:	09/11/2020
From:	Demetrius Murray Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
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ML20259A452	List: RS-20-104, Supplement to the Request for a License Amendment Technical Specification 3.7.3, Ultimate Heat Sink
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RS-20-104
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PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office RS-20-104 10 CFR 50.90 September 11, 2020 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 LaSalle County Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject:

Supplement to the Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, "Ultimate Heat Sink"

References:

1) Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, 'Ultimate Heat Sink,'" dated July 17, 2020 (ADAMS Accession No. ML20204A775)

2) Letter from B. K. Vaidya (U.S. Nuclear Regulatory Commission) to B. C.

Hanson (Exelon Generation Company, LLC), "LaSalle County Station, Units 1 and 2 - Supplemental Information Needed for Acceptance of Requested Licensing Action Regarding Request for a License Amendment to Technical Specification 3.7.3, 'Ultimate Heat Sink' (EPID L-2020-LLA-0165)," dated August 27, 2020 (ADAMS Accession No. ML20239A726)

In Reference 1, Exelon Generation Company, LLC (EGC) submitted a License Amendment Request (LAR) for LaSalle County Station , Units 1 and 2 proposing changes to Technical Specifications (TS) 3.7.3, "Ultimate Heat Sink," to expand the TS temperature limit of the cooling water supplied to the plant from the ultimate heat sink (UHS) to vary with the diurnal cycle by changing the average sediment level limit in the UHS to 6 inches.

In Reference 2, the NRC requested additional information necessary to complete its acceptance review of the referenced application. A clarification call was held on August, 25, 2020 between EGC and the NRC to gain clarity and understanding of the information request.

EGC has reviewed the information supporting the no significant hazards consideration and the environmental consideration that was previously provided to the NRC in Attachment 1 of Reference 1 letter. The additional information provided in this submittal does not affect the conclusion that the proposed license amendment does not involve a significant hazards consideration. This additional information also does not affect the conclusion that there is no need for an environmental assessment to be prepared in support of the proposed amendment.

Attachment 4 contains Proprietary Information.

When separated from Attachment 4, this document is decontrolled.

U.S. Nuclear Regulatory Commission September 11, 2020 Page 2 contains information proprietary to EGC. EGC requests that the contents of be withheld from public disclosure in accordance with 10 CFR 2.390(a)(4).

There are no regulatory commitments contained within this letter. Should you have any questions concerning this letter, please contact Phillip Henderson at (630) 657-4727.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 11th day of September 2020.

Respectfully, Dwi Murray Sr. Manager - Licensing Exelon Generation Company, LLC Attachments:

1. Response to Supplemental Information Request

2. Affidavit for Withholding of Exelon Proprietary Document

3. EC 632116, Revision 0, Evaluation of UHS Initial Temperature for Support of License Amendment Request for TS 3.7.3

4. Proprietary Information - Applicable Sections of Design Analysis L-002457, Revision 8, LaSalle County Station Ultimate Heat Sink Analysis cc: Illinois Emergency Management Agency - Division of Nuclear Safety NRC Regional Administrator - Region III NRC Senior Resident Inspector - LaSalle County Station

ATTACHMENT 1 Response to Supplemental Information Request

ATTACHMENT 1 Response to Supplemental Information Request By letter dated July 17, 2020 (Reference 1) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20204A775), Exelon Generation Company, LLC (EGC) submitted a License Amendment Request (LAR) for LaSalle County Station, Units 1 and 2 proposing changes to Technical Specifications (TS) 3.7.3, "Ultimate Heat Sink," to expand the TS temperature limit of the cooling water supplied to the plant from the ultimate heat sink (UHS) to vary with the diurnal cycle by changing the average sediment level limit in the UHS to 6 inches.

By letter dated August, 27, 2020 (Reference 2), the NRC requested additional information necessary to complete its acceptance review of the referenced application. A clarification call was held on August, 25, 2020 between EGC and the NRC to gain clarity and a mutual understanding of the information request.

References:

1) Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, "Ultimate Heat Sink," dated July 17, 2020 (ADAMS Accession No. ML20204A775)

2) Letter from B. K. Vaidya (U.S. Nuclear Regulatory Commission) to B. C. Hanson (Exelon Generation Company, LLC), " LaSalle County Station, Units 1 and 2 - Supplemental Information Needed for Acceptance of Requested Licensing Action Regarding Request for a License Amendment to Technical Specification 3.7.3, 'Ultimate Heat Sink' (EPID L-2020-LLA-0165)," dated August 27, 2020 (ADAMS Accession No. ML20239A726)

3) Design Analysis L-002457, Revision 8, "LaSalle County Station Ultimate Heat Sink Analysis"

4) EC 632116, Revision 0, "Evaluation of UHS Initial Temperature for Support of License Amendment Request for TS 3.7.3"

5) Letter from NRC to B. Hanson, "LaSalle County Station, Units 1 and 2, Issuance of Amendment Revising the Ultimate Heat Sink Temperature Limit (CAC Nos. ME9076 and ME9077)," dated November 19, 2015 (ADAMS Accession No. ML15202A578)

NRC Supplemental Information Request The licensee application dated July 17, 2020 (ADAMS Accession No. ML20204A775), does not provide sufficient information with respect to any reference, calculation or basis for how the reduction of sedimentation and increase in UHS volume corresponds to the resulting development of temperatures in the proposed curve shown in Figure 3.7.3-1 and Figure 1 of application.

Please provide all necessary references, calculations, or bases to support staff technical review of the revision to the proposed figure.

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ATTACHMENT 1 Response to Supplemental Information Request EGC Response to Supplemental Information Request In Reference 1, information provided in the Technical Analysis section provides the design input associated with the UHS analysis which resulted in the proposed Figure 3.7.3-1 and Figure 1 in Reference 1. Proposed Figure 3.7.3-1 shows the adjusted diurnal curve utilizing the transient heat-up for the 6 inches siltation levels in combination with 0.75ºF allowance for instrument uncertainty (i.e. Maximum peak cooling water temperature - Transient Heat-up Rate -

Instrument Uncertainty - 0.25ºF adjustment = Adjusted Initial UHS Temperature). This results in the maximum peak cooling water temperature of 107ºF under post-accident conditions. The current TS Figure 3.7.3-1 curve is also displayed in Figure 1 of Reference 1 to show the increased margin obtained from the increase in UHS volume using the 6 inches siltation levels.

A 0.25ºF adjustment factor was used in generating the curve to ensure that the peak initial UHS temperature does not exceed 106ºF which is the highest evaluated temperature for non-safety related systems.

EC 632116, Revision 0, "Evaluation of UHS Initial Temperature for Support of License Amendment Request for TS 3.7.3," is provided in Attachment 3 as the basis for the technical analysis in Reference 1. Attachment 3 contains references to the applicable sections of the UHS analysis provided in Attachment 4 as the relevant design inputs. Applicable sections of Design Analysis L-002457, Revision 8, "LaSalle County Station Ultimate Heat Sink Analysis," provided in Attachment 4 describes the effects of UHS volumetric changes due to sediment depth and impact on final UHS temperatures The following design inputs are associated with the UHS analysis provided in Attachment 4.

Each input is discussed below and how the changes in sedimentation level affect the values used in Attachment 4.

UHS Geometry The total surface area and volume of the UHS was 83.8 acres and 465.4 acre-feet, respectively.

The decrease in sedimentation does not directly affect the total UHS geometry. No physical changes have been made to the UHS to increase or decrease the UHS geometry. Therefore, there are no changes to this design input as a result of changes in sedimentation level.

Seepage Rate The UHS seepage rate used is 0.2 cubic feet per second. This value has been used since Revision 4 of Design Analysis L-002457. Since no physical changes have been made to the UHS or changes to the volumetric flows during the accident case has occurred, the change in sedimentation level does not affect this design input.

Core Standby Cooling System (CSCS) Pond Length The CSCS pond length is 5500 feet. This value has been used since Revision 4 of Design Analysis L-002457. Since no physical changes have been made to the UHS or changes to the volumetric flows during the accident case has occurred, the change in sedimentation level does not affect this design input.

Anemometer Height For the worst net evaporation weather data, which is obtained from the Peoria weather data from 1948 to 1996, the anemometer height is 20 feet. For the worst weather data, which is obtained from the LaSalle County Station weather data from 1995 to 2010, the anemometer is at a height of 33 feet. Since the change in sedimentation utilizes the same weather data from Page 2 of 4

ATTACHMENT 1 Response to Supplemental Information Request 1948 to 2010, no changes in anemometer height have been made and this design input remains unaffected by changes in sedimentation level.

CSCS Volumetric Flow The total plant flow during the UHS analysis is 29,300 gpm (65.3 ft3/s) for the first 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> of the event. The total plant flow is 38,600 gpm (86.0 ft3/s) after 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. The total flow after 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> is based upon the cumulative flow contribution from thirteen CSCS pumps operating at design flow conditions (eight Residual Heat Removal (RHR) Service Water pumps at 4,000 gpm each; three Diesel Generator (DG) pumps with two pumps at 1,300 gpm and one pump at 2,000 gpm; and two High Pressure Core Spray DG pumps at 1000 gpm each). Prior to 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />, two RHR Service Water pumps and one of the 1,300 gpm DG pumps are not in operation. No changes have been made to how the accident progress is analyzed or with regard to how much flow is drawn from the UHS during the accident scenario. Therefore, there are no changes to this design input as a result of changes in sedimentation level.

Maximum Allowable UHS Temperature The maximum allowable UHS temperature is 107°F. No changes have been made to the maximum allowable temperature the safety-related heat exchangers can envelop. Therefore, there are no changes to this design input as a result of changes in sedimentation level.

UHS Heat Load The UHS heat load is presented in Attachment P, Appendix P9.1 of Attachment 4. It shows the plant temperature rise caused by the heat rejected to the UHS during a postulated accident. No changes have been made to the postulated accident scenario. Since the maximum allowable UHS temperature and CSCS volumetric flow rate have not been changed, the change in sedimentation level does not affect this design input.

UHS Inventory for Fire Fighting Purposes Following an accident, 440,400 gallons of water from the UHS must be available for fire fighting as discussed in LaSalle County Station Updated Final Safety Analysis Report Section 9.2.6.3, "Safety Evaluation". No changes have been made to this input and this remains unaffected by the change in sedimentation level.

Additionally, during the clarification call held with the NRC on August, 25, 2020, the NRC requested that EGC reconcile weather information since the completion of the original license amendment (Reference 5) for the diurnal curve to verify weather conditions are still bounded.

As discussed in Attachment 4, the current weather data range is from 1948 to 2010. The first weather data file considered was used in previous revisions of Design Analysis L-002457 including weather station data from Peoria, IL and Springfield, IL for the dates between July 4, 1948 through June 30, 1996. The second weather data file considered contained weather station data from LaSalle County Station and Peoria, IL from January 1, 1995 to September 30, 2010.

The worst 30-day net evaporation weather period was determined to be from June 18, 1954 to July 18, 1954. The worst 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> weather period was determined to be from June 22, 2009 to June 23, 2009, and the worst 30 day weather period was determined to be from July 21, 1995 to August 22, 1995. The worst weather period consists of days with little to no cloud cover maximizing solar radiation. The days also have high levels of humidity and low variable winds in combination with steady air temperatures from day to night. The air temperatures within the worst weather periods are in the mid 70s to low 80s and remain consistent throughout the Page 3 of 4

ATTACHMENT 1 Response to Supplemental Information Request accident scenario. This climate ensures solar radiation heat input creates heat-up during the day, but the constant temperatures do not allow for nighttime cooling that would normally occur with higher air temperatures.

The worst weather modeling has been independently verified through confirmatory analysis as discussed in the NRC Safety Evaluation Report for LaSalle County Station Amendment No. 218 to Facility Operating License No. NPF-11 and Amendment No. 204 to Facility Operating License No. NPF-18 (Reference 5).

As discussed in Reference 5, the absence of accident heat as a determining factor of peak UHS temperature is attributed to a large heat sink that dissipates the accident heat before the affected water reaches plant intake. Heat waves where weather extremes have persisted for multiple consecutive days have occurred in the area. Thus, considering a heat wave in progress and a first critical time period of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the first day of the worst 30-day period may not be representative of the actual second day of a heat wave after a design basis accident of loss of coolant accident. However, the temperature values for more severe weather adds some margin for possible long term climatic change resulting from human or natural causes based on the sensitivity studies performed by both LaSalle County Station and the NRC in the confirmatory analysis.

A review was performed of meteorological data from Peoria International Airport from October 1, 2010 to August 1, 2020 obtained from the National Climate Data Center. The review did not identify any periods with unique conditions that create the worst weather conditions for the UHS.

The data set discussed in Attachment 4 contains 62 years of meteorological data. Since the UHS worst weather periods are not affected by hot weather conditions but by periods of high humidity and steady air temperatures between night and day, it is unlikely that the addition of 9 years of meteorological data will produce different results than that provided in Attachment 4.

Therefore, the diurnal curve proposed in Reference 1 bounds weather conditions since completion of Reference 5.

Page 4 of 4

ATTACHMENT 2 Affidavit for Withholding of Exelon Proprietary Document

ATTACHMENT 2 Affidavit for Withholding of Exelon Proprietary Document I, Dwi Murray, Sr. Manager - Licensing, Exelon Generation Company, LLC (EGC), do hereby affirm and state:

1. I am Sr. Manager - Licensing for EGC and I am authorized to execute this affidavit on behalf of EGC.

2. I am further authorized to review the documents sought to be withheld from public disclosure in connection with submittals to the Nuclear Regulatory Commission (NRC).

3. I am also authorized to apply to the NRC for the withholding of the aforementioned documents from public disclosure under 10 CFR 2.390(a)(4) and 9.17(a)(4) on the grounds that the documents contain privileged or confidential or proprietary commercial information. The documents EGC seeks to withhold from public disclosure have been marked "Proprietary."

4. On behalf of EGC, I request that the following document marked by EGC as "Proprietary" be withheld, in its entirety, by the NRC from public disclosure:

Attachment 4 of letter from EGC to NRC, Supplement to the Request for a License Amendment to LaSalle County Station, Units 1 and 2, Technical Specification 3.7.3, "Ultimate Heat Sink" (Tracking No. RS-20-104).

5. In making this application for withholding of proprietary and confidential information of which EGC is the owner, EGC relies on 10 CFR 2.390(a)(4) and 10 CFR 9.17(a)(4). The proprietary documents contain privileged or confidential or proprietary commercial information.

6. The proprietary information should be withheld from disclosure by the NRC pursuant to the policy reflected in 10 CFR 2.390(a)(4), and for the following reasons to be considered pursuant to 10 CFR 2.390(b)(4):

i. The documents are each either a policy, procedure, process, technical requirements document, or other document that forms part of the Exelon Nuclear Management Model (ENMM).

ii. The ENMM is a set of confidential policies and procedures that enable EGC to consistently achieve excellence in all key dimensions of its business. It documents proven ways of achieving excellence and defines how EGC executes and manages performance and assesses results. EGC expended significant resources, in terms of time and money, to develop, implement, and update the ENMM. EGC derives economic benefit from the ENMM in terms of increased efficiency and improved results as well as revenue generated from EGC's sale or licensing of the ENMM.

iii. The documents are now, and have been, held in confidence by EGC. EGC does not customarily make these documents available to the public. EGC has not authorized making the documents available through public sources.

iv. EGC is providing the NRC with the documents and information in confidence.

v. Economic harm would come to EGC with the publication of the individual documents that form the ENMM, as it would reduce or eliminate the need for any third party to purchase or license the ENMM from EGC, and would reduce the competitive position of EGC based on the benefits that the ENMM provides to EGC in the management of its own nuclear plants. The ENMM is considered by EGC to be a very valuable part of our intellectual property and it would be very difficult, costly and time-consuming for another to duplicate it without access to these documents.

7. EGC requests that each of the documents listed above in paragraph 4 be withheld from public disclosure based on the reasons stated above in paragraph 6.i. through 6.v.

Page 1 of 2

ATTACHMENT 2 Affidavit for Withholding of Exelon Proprietary Document I declare under penalty of perjury that the foregoing affidavit and statements therein are true and correct to the best of my knowledge, information, and belief.

Dwi Murray Sr. Manager - Licensing Exelon Generation Company, LLC Date: September 11, 2020 Page 2 of 2

ATTACHMENT 3 EC 632116, Revision 0, Evaluation of UHS Initial Temperature for Support of License Amendment Request for TS 3.7.3

EC 632116, Rev. 0 Page 1 of 7 EVALUATION OF UHS INITIAL TEMPERATURE FOR SUPPORT OF LICENSE AMMENDMENT REQUEST FOR TS 3.7.3 Reason for Evaluation / Scope:

This evaluation is being performed to support a License Amendment Request (LAR) for Technical Specification (TS) Surveillance Requirement (SR) 3.7.3.1 and 3.7.3.2 (Ref.

1). The proposed change would revise TS SR 3.7.3.1 to provide a new diurnal temperature curve based on changes to TS SR 3.7.3.2 which would change the sediment level requirement in the intake flume and CSCS pond, also known as the Ultimate Heat Sink (UHS), to 6 inches. The purpose of this evaluation is the evaluate the proposed changes in siltation levels and provide a new diurnal temperature curve for incorporation into the LAR submittal.

Detailed Evaluation:

For safety related systems, the applicable components are part of the CSCS cooling system. The current cooling water temperature used in the design basis analyses for these components is 107°F (Refs. 2 and 3). 1 The UHS follows a diurnal cycle where it warms up during the day and cools off at night. Because of this diurnal cycle, its thermal response following an accident is dependent upon the temperature of the lake and the time of day when the postulated failure of the dike occurs. The results of the analysis (Ref. 4) for the worst-case historical weather effect on the temperature of cooling water supplied to the plant from lake/UHS indicate the peak temperature of cooling water from the lake occurs late in the afternoon (approximately 6 pm). After it occurs, the lake follows the diurnal cycle and cools off until the next morning where it begins to heat up again. A parametric study evaluating key parameters that affect UHS performance was completed. The key parameters are the UHS sediment level, the time of day when the postulated failure of dike occurs, and the initial UHS temperature (i.e., temperature of the lake when the postulated failure of dike occurs). The results show that the most severe time for the dike to fail is early in the morning (approximately 6 am). This is the start time which results in the highest peak UHS temperature. The referenced analysis shows that the temperature of cooling water supplied to the plant from the UHS during accident conditions will not exceed 107°F, if the maximum initial temperature of the UHS is between 102°F and 104.75°F, depending on the time of day. These temperatures do not include instrument uncertainty. The limiting case is 18 inches of sedimentation. (Reference 2 and 4) 2 1

LSCS UFSAR Section 9.2.6.1.1 2

LSCS UFSAR Section 9.2.6.3.2

EC 632116, Rev. 0 Page 2 of 7 UHS Volume The volume of the UHS used as part of design bases analyses was determined utilizing the 1997 Contours Hydrographic Survey, 97ES083.1, performed by Ocean Surveys, Inc. (Ref. 5). The volume of the UHS was determined by using AUTOCAD and the calculated volume and surface area did not correct to account for accumulated sediment. The analysis determined that the surface area and volume of the UHS was 83.8 acres and 465.4 acre-feet, respectively. 3 In the UHS transient analysis (Ref. 4), 1.35 acre-ft is subtracted from the UHS volume to account for fire-fighting measures. Additionally, due to the Y-shape of the UHS, a portion of the UHS is stagnant during accident conditions due to the flow patterns from where the water enters the UHS and travels back to the intake.

This results in an effective surface area and volume of 48.52 acres and 293.89 acre-feet, respectively, or 57.9% of total free surface area and 63.4% of total volume. 4 UHS Siltation Approved design analyses (Ref. 4, Section 7.1.5) have been completed to show that reduced siltation levels in the UHS support a higher UHS starting temperature.

The limitations for siltation of the UHS are based on the average height of the silt and are correlated to the overall reduction of the effective UHS water volume. The table below shows the results of these evaluations for the most severe time that results in the highest peak UHS temperature of approximately 6 am in the morning for the limiting case of 18 inches of sedimentation. 5 Siltation Starting UHS Peak UHS Inlet Total Transient Heat Depth Temperature at 6am Temperature Up 0 102.0 °F 103.12 °F 1.12 °F 6 102.0 °F 103.21 °F 1.21 °F 12 102.0 °F 105.33 °F 3.33 °F

• 18 102.0 °F 106.15 °F 4.15 °F

• Current TS 3.7.3.2 limit The 3 most recent siltation surveillances (Refs. 6-8) were reviewed. These surveillances were completed in 2014, 2016, and 2018. They indicate that the average siltation depth is less than 6 inches and that changes since the baseline survey in 1997 have been insignificant. While there are localized peaks and valleys within the UHS in excess of 6, the average siltation depth remains unaffected. The top water elevation of 690 feet based on contour depths at the perimeter of the 3

Design Analysis L-002457, Rev. 8, Section 4.1 Page 20 and 6.2 Page 24 4

Design Analysis L-002457, Rev. 8, Attachment J, Section J7.0 Page J18 5

Design Analysis L-002457, Rev. 8, Section 7.1.5 Table Page 31, where the transient heat-up is the difference between the starting and peak temperatures

EC 632116, Rev. 0 Page 3 of 7 UHS has been verified to ensure adequate volume remains within the UHS following dike breach.

Safety Related Component Cooling Capability For safety related systems, the applicable components are part of the CSCS cooling system and are as follows:

• RHR heat exchangers

• Diesel generator jacket water coolers

• ECCS cubicle coolers

• LPCS motor coolers

• RHR pump seal coolers The above components have all been analyzed for a cooling water temperature of 107

°F per Reference 3 and show margin. The cooling capability of these components was determined with a maximum cooling water temperature (107 °F), maximum process fluid temperature, minimum cooling water flow rate, minimum process fluid flow rate, maximum tube plugging, and maximum design basis fouling factors.

Predicted Post Accident UHS Transient Heat Up Approved design analyses (Ref. 4) have determined that the current diurnal curve utilizing 18 of siltation is conservative since the actual average siltation levels of the UHS are less than 6 over the UHS area. This results in an increase in UHS effective volume of 24% which decreases temperature response due to the increased volume. 6 The table below provides the total transient heat-up values associated with the 6 siltation levels at each given time of day. Figure 1 shows the adjusted diurnal curve utilizing the transient heat-up for the 6 siltation levels in combination with 0.75 oF allowance for instrument uncertainty (i.e. Maximum peak cooling water temperature -

Transient Heat-up Rate - Instrument Uncertainty - 0.25oF adjustment) = Adjusted Initial UHS Temperature). This results in the maximum peak cooling water temperature of 107 o

F under post-accident conditions. The current TS 3.7.3-1 curve is also displayed to show the increased margin obtained from the increase in UHS volume. A 0.25oF adjustment factor was used in generating the curve to ensure that the peak initial UHS temperature does not exceed 106oF which is the highest evaluated temperature for non-safety related systems which is further discussed in Other Considerations. 7 Time Initial UHS Maximum Plant Total Transient Temperature Inlet Temperature Heat-Up 0:00 104.53 oF 105.21 oF 0.68 oF 3:00 102.72 oF 104.54 oF 1.82 oF 6:00 102.00 oF 103.21 oF 1.21 oF 9:00 103.19 oF 104.42 oF 1.23 oF 6

Design Analysis L-002457, Rev. 8, Attachment O, Section O2.1.3 Page O3 7

Design Analysis L-002457, Rev. 8, Section 7.1.5 Table Page 31

EC 632116, Rev. 0 Page 4 of 7 12:00 104.75 oF 104.99 oF 0.24 oF 15:00 104.75 oF 104.75 oF 0.00 oF 18:00 104.75 oF 104.75 oF 0.00 oF 21:00 104.75 oF 104.75 oF 0.00 oF The design analysis utilizes a 0.3 constant wind coefficient in the modeling of the transient heat up which is conservative. Wind sensitivities performed in Reference 4 have shown that when the UHS water surface temperature exceeds 100oF unstable atmospheric conditions will exist over the UHS, consequently the wind coefficients will remain less than 0.3 for all hours of the day which is shown to reduce the maximum UHS temperature by 1 oF for 18 sediment levels. This results in additional analytical margin within the analysis that also ensures that the maximum peak cooling water temperature will not exceed 107 oF. 8 Figure 1: Proposed UHS Diurnal Temperature Curve As shown, the 6 inch sedimentation temperature switch from 6am to 3am is driven by the larger temperature response between the two times where the temperature response rise is dependent on the limiting start time for a given sedimentation level (effective volume).

8 Design Analysis L-002457, Rev. 8, Attachment O, Section O6.8 Page O19

EC 632116, Rev. 0 Page 5 of 7 Modeling Changes Affected The analytical modeling of the UHS is not affected by the change in siltation levels from 18 to 6 inches. This is because the 18 inches case provides the most limiting results for all cases and bounds all other cases and is therefore conservative. Effects on mixing, transit time, and worst weather analysis have been reviewed and are summarized below (Reference 4):

UHS Mixing - Attachment O performed sensitivity studies on UHS mixing. It determined that the highest maximum UHS temperature occurs when no mixing zone is considered for the 18 inches of sedimentation case. Therefore, current modeling remains bounded and conservative. 9 Higher UHS Temperature - As stated in Attachment M, Section M3.1, for worst weather evaluation the initial lake temperature was set to 100oF and does not influence the results of the analysis. Therefore, the use of a higher UHS initial temperature would not affect the worst weather evaluation. 10 Transit Time - As stated in Attachment O, Section O6.4.1, shorter transit times were considered to not miss a short span of bad weather whereas the change from 18 to 6 will increase the transit time. The screenings also considered higher initial temperatures and concluded essentially the same worst average periods. The 18-inch sedimentation case (approximately 33 hour3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> transit time) was considered the most limiting case. The Ryan wind function will dominate at higher lake temperatures. 11 Temperature Response - Based on Attachment N, Section N6.2, Heat Transfer Model, heat sources contributing to the cooling pond, higher initial water surface temperatures will result in a decrease in net incident radiation (based on the same weather input data) and an increase in net rate of heat loss. This results in a reduced initial temperature response rise due to the heat loss. By using a lower initial temperature response rise of a lower initial temperature with the higher initial temperature is conservative. 12 Evaporative Losses The UHS must be designed to provide cooling water to maintain the two units in a safe shutdown condition for a 30-day period. In addition to the temperature limit discussed above, evaporative losses must be considered in the design of the UHS; the volume of 9

Design Analysis L-002457, Rev. 8, Attachment O, Section O6.9.3 Page O21 10 Design Analysis L-002457, Rev. 8, Attachment M, Section M3.1 Page M7 11 Design Analysis L-002457, Rev. 8, Attachment O, Section O6.4.1 Pages O13-O14 12 Design Analysis L-002457, Rev. 8, Attachment N, Section N6.2 Page N10

EC 632116, Rev. 0 Page 6 of 7 water must be verified to be adequate for 30 days following the accident to provide adequate NPSH to the required pumps. 13 With the increase in the UHS starting temperature, the change in evaporative losses is small. The safety related cooling water pumps and fire protection pumps have been evaluated for a water temperature of 107 °F and the reduced UHS volume. In fact, the available NPSH for the CSCS and FP pumps has been verified to be adequate with evaporative losses as high as 5 ft and 2.3 ft, respectively, with a cooling water temperature of 107 °F (Refs. 10 and 11).

Other Considerations The non-safety related fuel pool cooling heat exchangers have been evaluated for a cooling water temperature of 106 °F (Ref. 9). With the cooling water temperatures at 106 °F, they are able to maintain the fuel pool temperature below the maximum normal (batch offload) design basis limit of 140 °F. Other non-safety related heat exchangers cool plant equipment that is directly related to power production. These heat exchangers have also been qualified for a cooling water temperature of 106 °F per Reference 9. Non-safety related heat exchangers cannot be credited to mitigate any design basis events due to the lack of safety related power and safety related cooling water. Therefore, qualification beyond 106 °F is not necessary.

Non-safety related components were reviewed from an operational standpoint only, because the main concern is with their effect on power operation. They are not credited to mitigate any design basis events. Most components are reliability related and are monitored for parameters such as temperature and pressure. These components can be described as self-limiting, that is, operations personnel will respond to alarms and conditions in accordance with approved plant procedures, including load curtailment per LOA-CW-101/201, as required.

Additionally, controls are in place to monitor for fish kill. Procedure EN-LA-402-0005 directs operations to monitor the lake screen house trash basket twice per hour for indications of a fish kill. If a fish kill is observed, appropriate notifications are made and actions to remove the dead fish are initiated.

Conclusions / Findings:

The above evaluation shows that an adjusted UHS diurnal curve ranging from 104.43 -

106.25 oF can be accommodated with an average of 6 inches of sedimentation depth in the UHS. The safety related components have been qualified for a peak cooling water inlet temperature of 107 °F, which would not be exceeded as a result of the higher starting UHS temperature. The change from 18 inches to 6 inches in sedimentation does not affect the UHS modeling as the 18 inches case presents the most limiting conditions and bounds all other cases and is therefore conservative.

13 Design Analysis L-002457, Rev. 8, Attachment O, Section O6.7 Page O18

EC 632116, Rev. 0 Page 7 of 7 Limitation: Load curtailment in accordance with station procedures (i.e. LOA-CW-101/201) may be required to ensure the non-safety related components remain within their required operating parameters.

References:

1. Technical Specification 3.7.3

2. LaSalle UFSAR, Rev. 24, with approved pending changes

3. EC 388666, Rev. 001

4. L-002457, Rev. 008

5. L-001584, Rev. 001 up to and including 1A

6. WO 1568900

7. WO 1771573

8. WO 1945431

9. EC 381064, Rev. 000

10. L-001355, Rev. 007 up to and including 007I

11. L-003841, Rev. 000 (Approved)