ML20245E419

Issuance of Amendments Nos. 218 and 218 Revision of Technical Specifications for the Ultimate Heat Sink

ML20245E419
Person / Time
Site:	Braidwood
Issue date:	09/24/2020
From:	Joel Wiebe Plant Licensing Branch III
To:	Bryan Hanson Exelon Generation Co
Wiebe J
References
EPID L-2020-LLA-0159
Download: ML20245E419 (27)

Text

September 24, 2020 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)

Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

BRAIDWOOD STATION, UNITS 1 AND 2, - ISSUANCE OF AMENDMENTS NOS. 218 AND 218 RE: REVISION OF TECHNICAL SPECIFICATIONS FOR THE ULTIMATE HEAT SINK (EPID L-2020-LLA-0159)

Dear Mr. Hanson:

The U.S. Nuclear Regulatory Commission (the Commission) has issued the enclosed Amendment No. 218 to Renewed Facility Operating License No. NPF-72 and Amendment No. 218 to Renewed Facility Operating License No. NPF-77 for the Braidwood Station, Units 1 and 2, respectively. The amendments are in response to your application dated July 15, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20197A434), as supplemented by letter dated August 14, 2020 (ADAMS Accession No. ML20227A375).

The amendments revise Technical Specifications Surveillance Requirement 3.7.9.2 to allow an ultimate heat sink (UHS) temperature of less than or equal to 102.8 degrees Fahrenheit (°F) until September 30, 2020. The amendments also permanently change the completion time for the Required Action of both Braidwood Station, Units 1 and 2, 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 /> when the UHS is inoperable due to average water temperature.

B. Hanson A copy of the Safety Evaluation is also enclosed. A Notice of Issuance will be included in the Commissions biweekly Federal Register notice.

Sincerely,

/RA/

Joel S. Wiebe, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456, STN 50-457

Enclosures:

1. Amendment No. 218 to NPF-72

2. Amendment No. 218 to NPF-77

3. Safety Evaluation cc: Listserv

EXELON GENERATION COMPANY, LLC DOCKET NO. STN 50-456 BRAIDWOOD STATION, UNIT 1 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 218 Renewed License No. NPF-72

1. The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by Exelon Generation Company, LLC (the licensee) dated July 15, 2020, as supplemented by letter dated August 14, 2020, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance: (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

Enclosure 1

2. Accordingly, the renewed operating license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 2.C.(2) of Renewed Facility Operating License No. NPF-72 is hereby amended to read as follows:

(2) Technical Specifications The Technical Specifications contained in Appendix A as revised through Amendment No. 218 and the Environmental Protection Plan contained in Appendix B, both of which are attached hereto, are hereby incorporated into the renewed license. The licensee shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

3. This license amendment is effective as of the date of its issuance and shall be implemented within 5 days of the date of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION Robert F. Digitally signed by Robert F. Kuntz Kuntz Date: 2020.09.24 09:39:21 -04'00' Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Technical Specifications and Renewed Facility Operating License Date of Issuance: September 24, 2020

EXELON GENERATION COMPANY, LLC DOCKET NO. STN 50-457 BRAIDWOOD STATION, UNIT 2 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 218 Renewed License No. NPF-77

1. The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by Exelon Generation Company, LLC (the licensee) dated July 15, 2020, as supplemented by letter dated August 14, 2020, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance: (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

Enclosure 2

2. Accordingly, the renewed operating license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 2.C.(2) of Renewed Facility Operating License No. NPF-77 is hereby amended to read as follows:

(2) Technical Specifications The Technical Specifications contained in Appendix A as revised through Amendment No. 218 and the Environmental Protection Plan contained in Appendix B, both of which are attached to Renewed License No. NPF-72, dated January 27, 2016, are hereby incorporated into the renewed license. The licensee shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

3. This license amendment is effective as of the date of its issuance and shall be implemented within 5 days of the date of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION Robert F. Digitally signed by Robert F. Kuntz Kuntz Date: 2020.09.24 09:39:44 -04'00' Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Technical Specifications and Renewed Facility Operating License Date of Issuance: September 24, 2020

ATTACHMENT TO LICENSE AMENDMENT NOS. 218 AND 218 RENEWED FACILITY OPERATING LICENSE NOS. NPF-72 AND NPF-77 BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. STN 50-456 AND STN 50-457 Replace the following pages of the Renewed Facility Operating Licenses and Appendix A, Technical Specifications, with the attached revised pages. The revised pages are identified by amendment number and contain marginal lines indicating the areas of change.

REMOVE INSERT License No. NPF-72 License No. NPF-72 Page 3 Page 3 License No. NPF-77 License No. NPF-77 Page 3 Page 3 TSs TSs Page 3.7.9 - 1 Page 3.7.9 - 1 Page 3.7.9 - 2

(2) Exelon Generation Company, pursuant to the Act and 10 CFR Part 70, to receive, possess and use at any time special nuclear material as reactor fuel, in accordance with the limitations for storage and amounts required for reactor operation, as described in the Final Safety Analysis Report, as supplemented and amended; (3) Exelon Generation Company, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use at any time any byproduct, source and special nuclear material as sealed neutron sources for reactor startup, sealed sources for reactor instrumentation and radiation monitoring equipment calibration, and as fission detectors in amounts as required; (4) Exelon Generation Company, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use in amounts as required any byproduct, source or special nuclear material without restriction to chemical or physical form, for sample analysis or instrument calibration or associated with radioactive apparatus or components; and (5) Exelon Generation Company, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to possess, but not separate, such byproduct and special nuclear materials as may be produced by the operation of the facility.

C. This renewed license shall be deemed to contain and is subject to the conditions specified in the Commissions regulations set forth in 10 CFR Chapter I and is subject to all applicable provisions of the Act and to the rules, regulations, and orders of the Commission now or hereafter in effect; and is subject to the additional conditions specified or incorporated below:

(1) Maximum Power Level The licensee is authorized to operate the facility at reactor core power levels not in excess of 3645 megawatts thermal (100 percent rated power) in accordance with the conditions specified herein.

(2) Technical Specifications The Technical Specifications contained in Appendix A as revised through Amendment No. 218 and the Environmental Protection Plan contained in Appendix B, both of which are attached hereto, are hereby incorporated into the renewed license. The licensee shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

Renewed License No. NPF-72 Amendment No. 218

(2) Exelon Generation Company, LLC, pursuant to the Act and 10 CFR Part 70, to receive, possess and use at any time special nuclear material as reactor fuel, in accordance with the limitations for storage and amounts required for reactor operation, as described in the Final Safety Analysis Report, as supplemented and amended; (3) Exelon Generation Company, LLC, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use at any time any byproduct, source and special nuclear material as sealed neutron sources for reactor startup, sealed sources for reactor instrumentation and radiation monitoring equipment calibration, and as fission detectors in amounts as required; (4) Exelon Generation Company, LLC, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use in amounts as required any byproduct, source or special nuclear material without restriction to chemical or physical form, for sample analysis or instrument calibration or associated with radioactive apparatus or components; and (5) Exelon Generation Company, LLC, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to possess, but not separate, such byproduct and special nuclear materials as may be produced by the operation of the facility.

C. The renewed license shall be deemed to contain and is subject to the conditions specified in the Commissions regulations set forth in 10 CFR Chapter I and is subject to all applicable provisions of the Act and to the rules, regulations, and orders of the Commission now or hereafter in effect; and is subject to the additional conditions specified or incorporated below:

(1) Maximum Power Level The licensee is authorized to operate the facility at reactor core power levels not in excess of 3645 megawatts thermal (100 percent rated power) in accordance with the conditions specified herein.

(2) Technical Specifications The Technical Specifications contained in Appendix A as revised through Amendment No. 218 and the Environmental Protection Plan contained in Appendix B, both of which are attached to Renewed License No. NPF-72, dated January 27, 2016, are hereby incorporated into the renewed license. The licensee shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

Renewed License No. NPF-77 Amendment No. 218

UHS 3.7.9 3.7 PLANT SYSTEMS 3.7.9 Ultimate Heat Sink (UHS)

LCO 3.7.9 The UHS shall be OPERABLE.

APPLICABILITY: MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. UHS inoperable due to A.1 Be in MODE 3. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> average water temperature. AND A.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> B. UHS inoperable for B.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> reasons other than Condition A. AND B.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.9.1 Verify water level of UHS is t 590 ft Mean In accordance Sea Level (MSL). with the Surveillance Frequency Control Program SR 3.7.9.2 Verify average water temperature of UHS is In accordance d 102.8qF until September 30, 2020. After with the September 30, 2020, verify average water Surveillance temperature of UHS is d 102qF. Frequency Control Program BRAIDWOOD UNITS 1 & 2 3.7.9 1 Amendment



UHS 3.7.9 SURVEILLANCE REQUIREMENTS (cont.)

SURVEILLANCE FREQUENCY SR 3.7.9.3 Verify UHS contains a water volume of In accordance t 555.8 acre-feet with the Surveillance Frequency Control Program BRAIDWOOD UNITS 1 & 2 3.7.9 2 Amendment 

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 218 TO RENEWED FACILITY OPERATING LICENSE NO. NPF-72 AND AMENDMENT NO. 218 TO RENEWED FACILITY OPERATING LICENSE NO. NPF-77 EXELON GENERATION COMPANY, LLC BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. STN 50-456, STN 50-457

1.0 INTRODUCTION

By letter dated July 15, 2020 (Agencywide Documents Access and Management System (Reference 1), as supplemented by letter dated August 14, 2020) (Reference 2), Exelon Generation Company, LLC, (the licensee), requested changes to technical specification (TS) 3.7.9 Ultimate Heat Sink (UHS). The proposed changes would modify SR 3.7.9 to allow an UHS temperature of less than or equal to 102.8 degrees Fahrenheit (°F) between July 15 and September 30, 2020. The licensee also requested to permanently change the completion time for the Required Action of both Braidwood Station, Units 1 and 2, 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 /> when the UHS is inoperable due to average water temperature.

The supplement dated August 14, 2020, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the Nuclear Regulatory Commission (NRC or the Commission) staffs original proposed no significant hazards consideration determination as published in the Federal Register on August 19, 2020 (85 FR 51075).

2.0 REGULATORY EVALUATION

2.1 System Description The UHS consists of an excavated essential cooling pond (ESCP) integral with the main cooling pond. The Updated Safety Analysis Report (UFSAR), Section 2.4.11.6 (ADAMS Accession No. ML19169A114), states that the volume of the UHS is sized to permit the safe shutdown and cooldown of both Braidwood Station units for a minimum 30-day period during a design basis accident (DBA) without requiring makeup water. The UHS is designed to withstand the separate occurrence of either the safe shutdown earthquake or the probable maximum flood on the cooling pond. 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 Enclosure 5

licensee states in the UFSAR Section 2.4.1.1 that the ESCP is located in the northwestern corner of the cooling pond in an area excavated below the surrounding pond bottom, to an elevation of 584 feet. The ESCP has a surface area of 99 acres and a depth of 6.0 feet at a pool elevation of 590 feet.

The UHS dissipates residual heat after reactor shutdown and after an accident through the cooling components of the essential service water (SX) system and the component cooling water (CC) system, which are the principal systems at Braidwood Station that utilize the UHS to dissipate residual heat. The UHS also provides a source of emergency makeup water for the spent fuel pool and can provide water for fire protection equipment. Non-essential service water (SW) pumps and circulating water (CW) pumps also take suction from the UHS during normal operation, however, operation for post-accident conditions is not considered since the WS and CW pumps are shut down before the UHS level reaches the minimum required water level for plant operation at 590 feet.

2.2 Description of the Proposed Changes The proposed change permanently changes the completion time for the Required Action of both Braidwood Station, Units 1 and 2, 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 /> when the UHS is inoperable due to average water temperature. The proposed change to SR 3.7.9.2 allows an average UHS temperature of less than or equal to 102.8°F from the time of approval of this application until September 30, 2020.

The proposed changes to TS 3.7.9 are as follows:

Original TS 3.7.9 Condition A:

CONDITION REQUIRED ACTION COMPLETION TIME A. UHS inoperable A.1 Be in MODE 3 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND A.2 Be in MODE 5 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> Revised TS 3.7.9 Condition A and added Condition B:

CONDITION REQUIRED ACTION COMPLETION TIME A. UHS inoperable due A.1 Be in MODE 3 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to average water temperature AND A.2 Be in MODE 5 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> B. UHS inoperable for B.1 Be in MODE 3 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> reasons other than Condition A AND B.2 Be in MODE 5 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> The added Condition B continues to address the inoperability of the UHS for reasons other than average water temperature which is now addressed by Condition A.

Original SR 3.7.9.2:

Verify average water temperature of UHS is 102°F.

Revised SR 3.7.9.2:

Verify average water temperature of the UHS is 102.8 °F until September 30, 2020.

After September 30, 2020, verify average water temperature of UHS is 102 °F.

2.3 Regulatory Requirements and Guidance Used in the Evaluation of the Changes Licensing Basis Requirements In Braidwood Station, Units 1 and 2, UFSAR, Section 3.1.1 (ADAMS Accession No. ML19170A316), the licensee concludes that Braidwood Station, Units 1 and 2, fully satisfies, and is in compliance with the General Design Criteria (GDC). The following GDC are relevant to the design of the UHS:

GDC 2 - Design bases for protection against natural phenomena; GDC 5 - Sharing of structures, system, and components; GDC 44 - Cooling water.

Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.36(c)(2), states that limiting conditions for operation (LCOs) are the lowest functional capability or performance levels of equipment required for safe operation of the facility, and when an LCO is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TSs until the LCO can be met.

Paragraph 50.36(c)(3) of 10 CFR states that SRs are requirements relating to test, calibration, or inspection, to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met.

Regulatory Guidance NUREG-0800 Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 9.2.5, Ultimate Heat Sink, Revision 2, July 1981 (Reference 5)Section IV, Acceptance Criteria and Evaluation Findings, contain the following, in part:

a. GDC 2, as related to structures housing the system and the system itself being capable of withstanding the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, and floods. Acceptance is based on meeting the guidance of Regulatory Guide 1.29, Seismic Design Classification, Revision 3, September 1978 (ADAMS Accession No. ML031470286), Position C-1 and Regulatory Guide 1.27, Ultimate Heat Sink for Nuclear Power Plants, Revision 2, January 1976 (ADAMS Accession No. ML003739969), Positions C-2 and C-3.

b. GDC 5, as related to sharing of structures, systems, and components. Acceptance is based on demonstrating that such sharing does not affect the safe shutdown of either unit in the event of an active or passive failure.

c. GDC 44, as related to UHS requirements. Acceptance is based upon meeting the guidance of Regulatory Guide 1.27 and demonstrating the capability to transfer heat loads from safety-related SSCs to the heat sink under both normal operating and accident conditions.

3.0 TECHNICAL EVALUATION

The UHS provides a heat sink for the removal of process and operating heat from safety-related components during a transient or accident, as well as during normal operation. The UHS dissipates residual heat after reactor shutdown and after an accident through the cooling components of the SX system and the CC system, which are the principal systems at Braidwood Station, Units 1 and 2, that use the UHS to dissipate residual heat. The UHS also provides a source of emergency makeup water for the spent fuel pool and can provide water for fire protection equipment.

The limit on the UHS pond temperature is meant to restrict the initial UHS temperature such that the maximum temperature of the SX system supplied to the plant safety systems from the UHS experienced during the UHS design basis event would not result in plant equipment cooled by the UHS to operate outside design limits. If the requirement for temperature of the SX system supplied by the UHS exceeds the TS 102 °F limit in the existing TS, then both units would be placed in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

The SX system takes suction from intake lines running from the Safety Category I ESCP to the auxiliary building where four SX system pumps (two per unit) supply safety-related loads and components essential to safe shutdown. These include cubicle coolers, pump coolers, diesel engine coolers, CC system heat exchangers, reactor containment fan coolers (RCFC) and chiller condensers.

The CC system provides cooling water to the residual heat removal (RHR) system, chemical and volume control system, reactor coolant system and process sampling system.

As indicated in Reference 1, the limiting DBA includes three sources of heat energy to be transferred by the SX system after a loss-of-coolant accident (LOCA):

1. containment heat removal via the RCFCs,

2. containment heat removal via the containment sumps [from containment spray] and reactor residual heat removal [via RHR system heat exchanger], and

3. engineered safety features (ESF) equipment heat loads (e.g., ESF equipment coolers and room coolers) and the Main Control Room chiller.

The licensee evaluated these sources with respect to the 106 °F peak post-accident temperature. In its evaluation, the licensee considered the impact of a 102.8 °F UHS temperature on the safety related components being credited in the accident analyses.

The NRC staff questioned inclusion of the July 15, 2020, start date proposed for SR 3.7.9.2 acceptance criteria. In Reference 2, the licensee revised the acceptance criteria to read until September 30, 2020 without including start date of July 15, 2020.

The revised TS SR 3.7.9.2 allows a UHS temperature of less than or equal to 102.8 °F until September 30, 2020. This change allows operation with a higher UHS temperature of up to 102.8 °F during normal operation. The UHS requirements are based on the estimated analyzed

post-accident limit of 105.2 °F which provides 0.8 °F margin for the equipment temperature limit of 106 °F.

The NRC staff notes that in the month of September the average daily weather temperatures near the plant location will have reduced likelihood of potential overtemperature condition and challenges to the TS temperature limit for the UHS. In Reference 1, the licensee stated that it is performing an additional detailed margin analyses and considering equipment modifications to increase margins and indicated that these analyses and modifications will not be completed in time to support potential impacts through the period of this request. Therefore, the licensee requested this TS temperature change to cover a limited period of time.

3.1 Equipment Supported by SX The licensee states in Reference 1 that the SX system supplies the safety related loads and components required for safe shutdown. These include cubicle coolers, pump coolers, diesel engines coolers, containment coolers, component cooling water heat exchangers, RCFC and chiller condensers. The purpose of the UHS TS temperature limit is to restrict the initial UHS temperature such that the maximum UHS temperature (i.e., the temperature of the cooling water supplied to the plant safety systems from the UHS) experienced during the UHS design basis event would not exceed the design limit of the plant equipment cooled by the UHS. The post-accident performance of the equipment served by SX system has been analyzed for a SX supply temperature of 106 °F.

The licensee states in Section 3.0 of Reference 1, that the current design basis analyses support an initial SX system temperature of less than or equal to 102 °F, as previously approved through TS amendment 189 (Reference 3). In support of TS amendment 189, the licensee used 106 °F to analyze the post-accident performance of the equipment served by SX, except for the RCFC which used 104 °F. The licensee in UFSAR, Section 9.2.1.2.1 (ADAMS Accession No. ML19170A384), states that the heat transfer equipment has been evaluated for the bounding temperature of 106 °F. The licensees UHS analysis of record, approved as part of the TS change to 102 °F, calculated the highest resulting UHS temperature following the design basis event would be less than or equal to 105.2 °F. The licensee, in Reference 1 provides a figure showing the temperature response for the worst-case LOCA. The licensee in Reference 1 states, An evaluation has been completed that supports a 0.8 °F increase in SX temperature on accident analyses and containment response and analyses of the components served by SX. The licensee concludes that an increase of 0.8 °F in allowable UHS TS temperature limit would result in a corresponding increase in the highest calculated design basis event UHS temperature to 106°F.

As documented in Reference 3, the NRC staffs previous review included sensitivity runs performed at 102 °F. Additionally, the NRC staff performed sensitivity runs for a starting temperature greater than 102 °F and 75 percent heat transfer efficiency and found that peak return temperature exceeds 105.2 °F, but did not exceed 106 °F for the evaluated runs. Since the runs used starting temperatures greater than 102 °F and the results did not exceed 106 °F, the NRC staff determined that the previous evaluation supports the acceptability of temperatures above 102 °F.

3.2 Impacts on Accident Analysis 3.2.1 Containment Integrity (UFSAR Chapter 6)

The licensee stated in Reference 1, that the SX system supplies the RCFCs post-accident and that the temperature of the SX is an important factor in the heat removal capability of the RCFCs. The licensees analysis done for containment integrity, as described in the UFSAR (ADAMS Accession No. ML19170A012), assumes an SX temperature of 104°F. The figure on page 6 of Reference 1 shows the UHS temperature profile for the limiting design basis analysis.

In this figure, it is seen that the starting temperature is 102 °F and does not reach 104 °F until a little after 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> later. Assuming the initial temperature is increased to 102.8 °F, as proposed in the LAR, the temperature response would be expected to follow the same trends as seen in the figure, only reach 104 °F a few hours earlier. During a LOCA or main steam line break (MSLB), the containment pressure and temperature would initially increase rapidly, then decrease over time as seen in UFSAR, Figures 6.2-1 through 6.2-15. As stated in Reference 1, the peak containment temperature and pressure occur early in the accident, well before the UHS post-accident temperature exceeds the RCFC analyzed temperature of 104 °F. The NRC staff notes that this justification was accepted by the NRC in Reference 3 for the initial temperature of 102 °F, and that this justification remains valid for the initial temperature being 102.8 °F because the UHS temperature exceeds the RCFC analyzed temperature after the RCFCs are needed to remove heat from the containment to reduce the peak temperature and pressure.

In addition, the licensee states in Reference 1 that the heat removal curve used for the RCFCs is conservative because it is based on a tube plugging level of 10 percent, while the actual tube plugging is less than 2 percent. Given that the containment pressures and temperatures have been significantly reduced from their respective calculated peak values by the time the UHS temperature exceeds the RCFC analyzed temperature of 104 °F, and the heat transfer of the RCFCs is conservatively modelled, NRC staff finds that the proposed increase in the UHS temperature will not result in exceeding any design criteria related to post-LOCA containment requirements.

3.2.2 Peak Clad Temperature Analyses Peak cladding temperature (PCT) is calculated for LOCAs in order to demonstrate compliance with the requirements of 10 CFR 50.46. During a LOCA, the emergency core cooling system (ECCS) water is initially drawn from the refueling water storage tank (RWST). When the RWST is nearly empty, the pumps are realigned to the containment sump (i.e., cold leg recirculation).

The licensee stated in Reference 1 that assuming no single failure and full runout flow from all the pumps, the earliest time the RWST can empty is in excess of 10 minutes. Given that the large break LOCA PCTs occur very early in the accident (102 seconds for Braidwood Station, Unit 1, and 96 seconds for Braidwood Station, Unit 2), and that the UHS temperature has no effect on the RWST water temperature, the staff finds that the proposed increase of 0.8°F to the UHS temperature limit has no effect on the PCT for large break LOCAs while the ECCS is drawing water from the RWST..

During the long-term response to a large break LOCA, when the ECCS is drawing water from the containment sump, the UHS temperature can have an effect on cladding temperatures.

However, as stated in the LAR, at this point in the transient, the PCTs are significantly lower, and a 0.8 °F variance in UHS temperature will not result in the clad temperatures challenging the calculated peak. Therefore, NRC staff finds that during the long-term response to the large

break LOCA, the PCT will not be changed as a result of increasing the UHS temperature limit to 102.8 °F.

For the small break LOCA analysis, the licensee states that the UHS is not explicitly modeled, and, therefore, the proposed increase in UHS temperature does not directly impact the analysis.

However, the licensee, in Reference 1, identified other items which could affect the small break LOCA analysis as described below.

The SX system is the safety-related backup to the auxiliary feedwater (AFW) system. With the proposed increase to the UHS temperature limit, the AFW temperature could reach a maximum of 106 °F. The licensee stated that the AFW is modeled in the small break LOCA analysis with a temperature of 125 °F. Therefore, NRC staff finds that the analysis temperature is bounding and the change to the UHS temperature would not impact the small break LOCA analysis due to an increase in AFW temperature.

The licensee stated that the temperature of the safety injection water in the small break LOCA analysis is assumed to be at 120 °F, based on the RWST as the source. As noted above for large break LOCA, the UHS temperature change does not impact the RWST. Therefore, NRC staff finds that the safety injection water temperature in the small break LOCA analysis is not impacted by the proposed increase to the UHS temperature limit.

The licensee stated that the temperature of the recirculation water in the small break LOCA is set at 212 °F and that design analyses completed in support of TS Amendments No. 189 (Reference 3) have calculated the RHR heat exchanger discharge temperature to be below 212

°F. The licensee also stated that the CC heat exchanger has been evaluated and has been found to be able to remove the required heat load that supports the assumptions of the calculation with an SX supply temperature of 106 °F. Given that an initial UHS temperature of 102.8 °F results in a maximum UHS temperature of less than or equal to 106 °F, the NRC staff finds that the CC heat exchanger will remove the required amount of heat and the resulting temperature of the recirculation water will remain less than 212 °F. In summary, the staff finds that the proposed 0.8 °F increase to the UHS temperature limit will have no detrimental impact on the small break LOCA analysis results.

The licensee also identified three non-LOCA events including MSLB, feedwater line break and steam generator tube rupture where ECCS is modeled and assumed to operate. The licensee stated that these events are terminated well before the RWST is drained. Therefore, NRC staff finds that the proposed 0.8 °F increase in UHS temperature limit will have no detrimental impact on these non-LOCA events.

3.2.3 Long Term Core Cooling and Hot Leg Switchover Analysis As stated in Reference 1, the limiting UHS design basis accident that results in the maximum heat load on the UHS is one unit undergoing post-LOCA cooldown concurrent with a loss of off-site power (LOOP), in conjunction with the other unaffected unit undergoing a safe non-accident shutdown. During the long-term response to a LOCA, the operator is instructed by procedure to align the ECCS to cold leg recirculation when the RWST level reaches the auto switchover level setpoint and to hot leg recirculation at 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, as stated in Section 15.0.14 of the UFSAR (ADAMS Accession No. ML19170A347). In Section 3.1 of Reference 1, the licensee presented a figure showing the UHS temperature response following the worst-case LOCA that assumes a start time of 3 AM and an initial temperature of 102 °F. In this figure, it is seen that the temperature of the UHS decreases over 2 °F during the first 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of the event. Using the

licensees figure and assuming a starting temperature of 102.8 °F, as proposed in the LAR, the NRC staff determined that the temperature at 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> would still be expected to be below that of the starting temperature. Given that this temperature is below the 106 °F analysis limit for performance of the equipment served by SX and the 104 °F analysis limit for the RCFC, the NRC staff finds that the existing design analysis for hot leg switchover remain acceptable with a maximum UHS starting temperature of 102.8 °F.

3.2.4 CC System to Reactor Coolant Pumps (RCPs)

The CC system adds heat to the UHS during normal plant operation and during accident conditions. The licensee states in Section 3.3.4 of Reference 1:

The maximum CC temperature to the Reactor Coolant Pumps (RCP) is 105 °F during normal plant operation. This temperature limit is raised to 120 °F for a short period (3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />) when the Residual Heat Removal system is first used during RCS cooldown. The postulated increase in CC temperature of 0.8 °F is found acceptable by Engineering Judgement. This is based on the small increase and the short duration considering the diurnal cycle of the UHS temperature profile.

In a previous NRC staff review (Reference 3), the staff concluded that the CC heat exchangers will satisfactorily function under design basis accident conditions with an SX temperature of 106 °F and will satisfactorily function under normal operating conditions with an SX temperature of 102 °F. The licensee provided engineering judgement to conclude the small increase and short duration at an elevated UHS temperature during normal operation is acceptable. Based on the above, the staff agrees with the licensees determination that the 0.8 °F increase of CC temperature is reasonable pertaining to the RCP function.

3.2.5 Other Analyses In Section 3.3.5 of the LAR, the licensee also evaluated other considerations, such as the impact of increasing the UHS temperature to 102.8 °F on Generic Letter (GL) 96-06, "Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," and station blackout (SBO).

GL 96-06:

In reference to NRC GL 96-06, "Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions" (ADAMS Accession No. ML031110021), the licensee identified a concern for possible water hammer following either a LOCA or a MSLB concurrent with a LOOP during the first few minutes post-accident while the pumps and fans are restarting following the LOOP. The licensee performed a detailed analysis to address the concern. The NRC staff previously concluded in Reference 3 that the licensee satisfactorily addressed the GL-96-06 issue for the proposed increase in the UHS temperature to less than or equal to 102°F.

In Reference 1, the proposed TS UHS temperature limit is 102.8 °F. The licensee states in Section 3.3.5 of Reference 1 that a slight increase in fluid temperature will not result in significant changes to the amount of voiding and thus negligible impacts to void collapse and the existing results of the previous analysis. Because the temperature increase is small, the

NRC staff concludes that the 0.8 °F increase does not change the previous staff finding pertaining to GL 96-06.

Diesel Driven Auxiliary Feedwater Pump Operation during Loss of All AC Power:

The licensee states in Section 3.3.5 of Reference 1:

In the event of a loss of all AC power (i.e., Station Blackout or SBO), a diesel driven SX booster pump operates to provide cooling water to the diesel driven AF pump and engine cooler. Due to the configuration of the discharge piping to the lake, there is insufficient booster pump head to maintain once-through flow to the lake during this event. Thus, flow recirculates through various components back to the diesel driven SX booster pump suction. This results in isolation of the cooling water heat sinks and heat-up of the isolated SX loop during the SBO coping period.

Design analysis evaluates this transient and concludes that AF diesel engine jacket water temperature will not exceed the engine trip setpoint in 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The calculation evaluates a maximum UHS temperatures of 102 °F. The analysis used a plugging level of 5 tubes for the 102 °F case. The analysis also determined that the allowed tube plugging decreases by two (2) tubes for each

°F increase in the SX temperature. The actual numbers of tubes that are plugged for the heat exchangers (1/2SX01K) is zero (0) for Unit 1 and one (1) for Unit 2. The actual plugging level supports a maximum SX temperature of 104 °F.

Therefore, raising the SX temperature to 102.8 °F is acceptable.

Based on the actual tube plugging being significantly less than the assumption being used for the design analysis, the NRC staff finds the licensees determination is acceptable.

3.2.6 Conclusion Based on the above the NRC staff concludes that raising the TS max UHS temperature to 102.8

°F until September 30, 2020, has no impact on the accident analysis.

3.3 Extension of Completion Time The LAR also proposes to increase the Required Action completion time for both Braidwood Station units to be in Mode 3 from 6 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, if the UHS is inoperable due to average UHS water temperature. The licensee states in Reference 1 that, This proposed change would allow the natural diurnal cooling behavior of the lake to occur in restoring the UHS temperature below the TS limit without having to shutdown both Braidwood Station units and place each unit through an unnecessary thermal cycle evolution. The NRC staff requested the licensee to justify acceptability of operating outside of the design basis for up to an additional 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, including potentially every day during the summer In response (Reference 2), the licensee provided historical temperature data for the last three summers as well as the diurnal temperature cycle for the July 7 to July 9, 2020, period. The licensee stated that the highest UHS temperature recorded at Braidwood Station, Units 1 and 2, was 101.15°F and occurred on July 7, 2020, at ~6:30 PM.

The table on Page 7 of Reference 1 shows the resulting maximum UHS temperature as a result of the DBA starting at different times of day. This table shows the limiting DBA occurs at 3 AM.

At this point in time, the temperature would be reduced from the maximum as seen in the diurnal temperature data for the July 7 to July 9, 2020, period. The results from the table also show that the maximum UHS temperature will remain below the currently analyzed equipment limit of 106 °F, provided the UHS temperature is below 103.3 °F for an event starting at 6:00 PM (around when the peak temperature is expected to occur).

Based on the historical temperature data provided by the licensee, the NRC staff finds that allowing the natural diurnal cooling of the UHS is an appropriate action to take as it will ultimately reduce the UHS temperature.

An additional change proposed to TS Condition A was the clarification of due to average water temperature. As proposed by the licensee, the changes in TS 3.7.9 would increase the Required Action completion time for Condition A to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, if the UHS is inoperable due to average UHS water temperature. The NRC staff requested the licensees clarification of the term, average UHS water temperature.

The licensee clarified in its response (Reference 2) that the "average UHS temperature" is the average of the temperatures measured at the discharge of the running SX pumps on Braidwood Station, Units 1 and 2. The licensee explained how the surveillance is procedurally controlled to require that if the temperature of any operating SX pump is 99 °F, a precision temperature instrument is used to verify the temperature to address inaccuracies of measuring devices. The control room operator is required to record and compare the average SX pump discharge temperature from both units to the limits in TS SR 3.7.9.2. The SX pump discharge temperature (i.e., used to verify the TS SR 3.7.9.2 limit) is the average of each unit's running SX pump discharge temperature and could result in both units entering the required actions at the same time should SX temperature exceed the TS limit. Based on above, the NRC staff finds the licensees clarification reasonable and the process for monitoring temperature acceptable.

The licensee provided, in Reference 1, qualitative information related to the risk of the proposed 12-hour completion time to support its request. The licensee stated that the possibility of the DBA LOCA coupled with the failure of the manmade structure surrounding the UHS during a 12-hour completion time is not measurably increased from the same event occurring during the original 6-hour completion time. In addition, the licensee stated that a 12-hour completion time to reach Mode 3 is consistent with other plants with cooling lakes affected by diurnal variations.

The licensee stated that the proposed extension of completion time to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> would allow for the natural diurnal cycle to cool the UHS and to avoid Braidwood Station, Units 1 and 2, being in the transition period between modes that would cause an unnecessary plant transient without a corresponding benefit in safety. The licensee explained that Braidwood Stations continued operation during infrequent short periods of increased UHS temperature while allowing the natural diurnal cycle to cool the UHS would not have an adverse impact to safety and not cause risk to exceed the level of risk determined to be acceptable during normal operation. As stated in Appendix F, Notice of Enforcement Discretion, of the NRC Enforcement Manual (Reference 4), the NRC has historically recognized that the two safest modes for operating a nuclear power plant are either Mode 5 (shut down) or Mode 1 (operating at power) and that transitions between these two modes may introduce situations or configurations that involve an increase in risk. The licensees intent to reduce transitions between Modes by its requested change is consistent with NRC policy.

The NRC staff is familiar with the temperature characteristics of the Braidwood Station UHS and performed a review of the effect a 12-hour completion time has on peak UHS temperature.

Figure 1 of Reference 2 shows the typical diurnal cycle for the Braidwood Station UHS. The UHS typically operates at a temperature in the low to mid-nineties during the summer months.

During adverse weather conditions of high ambient temperature, low wind speed, high humidity, little cloud cover, and no rain, the peak UHS temperature slowly increases while maintaining its diurnal cycle. If the weather conditions are adverse for several days in a row, the peak temperature (typically occurring in the early evening) can approach the TS UHS limit. As the licensee stated in its application, the maximum temperature recorded was estimated at 101.15

°F and adverse weather typically does not last long enough to cause the UHS temperature to reach the TS limit. As described in Reference 2, the UHS temperature approached the TS limit in July of 2012, and again in July of 2020. If the UHS temperature does exceed the limit, it would be the result of a slow increase typical of that shown in Figure 1 of Reference 2 and the licensee would be required to initiate action to bring the plant to MODE 3. Because the UHS temperature limit is applied to the peak temperature of the diurnal cycle, the diurnal cycle would likely cause the temperature to decrease below the TS limit in a short period of time. If adverse weather conditions continued during the next diurnal cycle temperature peak, the time period during which the UHS is above the TS limit may increase. The diurnal cycle during the summer months typically causes the Braidwood Station UHS to vary about 2 °F from peak to peak in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> completion time to be in MODE 3 (in the worst case when the peak temperature would be above the TS limit for the entire 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> period) would limit the allowed temperature above the TS limit to half the peak to peak value, or about 1 °F. The NRC staff compared 1 °F above the TS limit (i.e., the worst-case allowed) to the licensees proposed 0.8

°F above the limit. Based on the above, the NRC staff finds that the actual risk of plant operation resulting from permanently revising the completion time to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is very small because in the worst-case, it only results in about a 0.2 °F short term temperature increase above the temperature determined to be acceptable.

Given that the historical operational data shows, the natural diurnal cooling, the minimal change in operating risk with an increased UHS temperature, and the avoidable risk from infrequent and short-duration operational transients, the NRC staff finds the proposed 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> completion time for LCO 3.7.9, Action A.1, acceptable.

3.4 Margin In Section 4.2 of Reference 1, the licensee specifies that there is no reduction in the margin of safety of the plant. It stated that the proposed change continues to ensure that the maximum temperature of the cooling water supplied to the plant systems, structures, and components (SSCs) during a UHS design basis event remains within the evaluated equipment limits and capabilities assumed in the accident analysis. However, increasing the allowable temperature of the UHS to 102.8 °F reduces the margin between the UHS temperature and the analyzed equipment limits (106 °F).

The licensee stated in Reference 1 that it is performing detailed margin analyses and considering modifications to some equipment to increase margins. It further indicated that these analyses and modifications will not be completed in time to support this amendment. The possibility of approaching the existing temperature limit of 102 °F is significantly reduced beyond the month of September. As a result, the licensee requested the TS change applicability to expire after September 30, 2020.

As indicated in UFSAR 9.2.5.3, the UHS analysis of record utilizes meteorological data from July 5, 1948, to December 31, 2012. More current data may be available but the average ambient outdoor temperatures in the area is historically lower than proposed TS temperature

during month of September. This results in a low risk of a UHS over-temperature condition during TS applicable period.

Based on the limited duration of applicability for this SR 3.7.9.2 surveillance requirement and the understanding that licensee will further evaluate margin, there is reasonable assurance that the reduction in margin is acceptable during the limited duration requested.

3.5 Technical Conclusion Based on the above, the NRC staff finds that the TS and SR changes only affect temperature and therefore have no impact on structures housing the system and the system capability of withstanding the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, and floods. The NRC staff, therefore, concludes that the licensee continues to meet the requirements of GDC 2.

Based on the above, the NRC staff finds that the TS and SR changes only affect temperature and have no impact on sharing of SSCs. The NRC staff, therefore, concludes that the licensee continues to meet the requirements of GDC 5.

Based on the above, the NRC staff finds that increasing the TS UHS temperature limit to 102.8 °F has no impact on the accident analysis. The NRC staff also finds that increasing the TS UHS temperature limit to 102.8 °F does not significantly affect the equipment that is cooled by the UHS. The NRC staff also finds that increasing the TS UHS temperature limit to 102.8 °F has no effect on the structure of the UHS nor the amount of water available to the UHS. The NRC staff also finds that increasing the time allowed to be in MODE 3 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> upon exceeding the average UHS maximum temperature has no effect on the UHS structure and contributes little to operational risk. The NRC staff, therefore, concludes that the licensee continues to meet the requirements of GDC 44.

Based on the technical acceptability of the TS changes as discussed in Section 3 of this SE, the NRC staff finds that the revised TS 3.7.9, Condition A, and the added Condition B, continue to represent the lowest functional capability or performance level of equipment required for safe operation of the facility, and when an LCO is not met, the licensee is required to shutdown the reactor or follow any remedial action permitted by the TSs until the LCO can be met. The NRC staff, therefore, concludes that 10 CFR 50.36(c)(2) is met.

Based on the technical acceptability of the SR 3.7.9.2 change as discussed in Section 3 of this SE, the NRC staff finds that the revised SR 3.7.9.2 assures that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met. The NRC staff, therefore, concludes that 10 CFR 50.36(c)(3) is met.

Based on the above, the NRC staff concludes that the TS and SR changes listed in Section 2.2 of this SE are acceptable.

4.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION

The NRCs regulation in 10 CFR 50.92(c) states that the NRC may make a final determination, under the procedures in 10 CFR 50.91, that a license amendment involves no significant hazards consideration if operation of the facility, in accordance with the 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.

An evaluation of the issue of no significant hazards consideration provided by the licensee is presented below:

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

Response: No.

The likelihood of a malfunction of any systems, structures or components (SSCs) supported by the Ultimate Heat Sink (UHS) is not significantly increased by increasing the allowable UHS temperature from 102°F to 102.8°F or extending the time for both Unit 1 and Unit 2 to be placed in Mode 3 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. 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 proposed change does not make any physical changes to any plant SSCs, nor does it alter any of the assumptions or conditions upon which the UHS is designed. The UHS is not an initiator of any analyzed accident. All equipment supported by the UHS has been evaluated to demonstrate that their performance and operation remains as described in the UFSAR with no increase in probability of failure or malfunction.

The SSCs credited to mitigate the consequences of postulated design basis accidents remain capable of performing their design basis function.

The change in maximum UHS temperature has been evaluated using the UFSAR described methods to demonstrate that the UHS remains capable of removing normal operating and post-accident heat. The change in UHS temperature and resulting containment response following a postulated design basis accident has been demonstrated to not be impacted. Additionally, all the UHS supported equipment, credited in the accident analysis to mitigate an accident, has been shown to continue to perform their design function as described in the UFSAR.

Therefore, 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 does not create the possibility of a new or different kind of accident from any accident previously evaluated. The proposed change does not introduce any new modes of plant operation, change the design function of any SSC, or change the mode of operation of any SSC.

There are no new equipment failure modes or malfunctions created as affected SSCs continue to operate in the same manner as previously

evaluated and have been evaluated to perform as designed at the increased UHS temperature and as assumed in the accident analysis.

Additionally, accident initiators remain as described in the UFSAR and no new accident initiators are postulated as a result of the increase in UHS temperature.

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

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

Response: No.

The proposed change continues to ensure that the maximum temperature of the cooling water supplied to the plant SSCs during a UHS design basis event remains within the evaluated equipment limits and capabilities assumed in the accident analysis. The proposed change does not result in any changes to plant equipment function, including setpoints and actuations. All equipment will function as designed in the plant safety analysis without any physical modifications. The proposed change does not alter a limiting condition for operation, limiting safety system setting, or safety limit specified in the Technical Specifications.

The proposed change does not adversely impact the UHS inventory required to be available for the UFSAR described design basis accident involving the worst case 30-day period including losses for evaporation and seepage to support safe shutdown and cooldown of both Braidwood Station units. Additionally, the structural integrity of the UHS is not impacted and remains acceptable following the change, thereby ensuring that the assumptions for both UHS temperature and inventory remain valid.

Therefore, since there is no adverse impact of this proposed change on the Braidwood Station safety analysis, there is no reduction in the margin of safety of the plant.

The NRC staff reviewed the licensees no significant hazards consideration analysis. Based on the review and on the NRC staffs evaluation of the underlying license amendment request (Reference 1, as supplemented by Reference 2) as discussed above, the NRC staff concludes that the three standards of 10 CFR 50.92(c) are satisfied. Therefore, the NRC staff has made a final determination that no significant hazards consideration is involved for the proposed amendments and that the amendments should be issued as allowed by the criteria contained in 10 CFR 50.91.

5.0 STATE CONSULTATION

In accordance with the Commissions regulations, the Illinois State official was notified of the proposed issuance of the amendment on August 25, 2020. The State official had no comments.

6.0 ENVIRONMENTAL CONSIDERATION

The NRC staff published an Environmental Assessment (EA) in the Federal Register on September 10, 2020 (85 FR 55863) related to this proposed action. In that EA, the NRC staff concluded that the proposed action would not have a significant effect on the quality of the human environment. Accordingly, the NRC staff determined that an environmental impact statement was not warranted for the proposed action.

7.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

8.0 REFERENCES

1. Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink,'" dated July 15, 2020 (ADAMS Accession No. ML20197A434).

2. Response to Request for Additional Information Regarding License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, "Ultimate Heat Sink" dated August 14, 2020 (ADAMS Accession No. ML20227A375).

3. NRC Safety Evaluation Report, Braidwood Station Units 1 and 2 - Issuance of Amendments RE: Ultimate Heat Sink Temperature Increase, dated July 26, 2016 (ADAMS Accession No. ML16133A438).

4. Nuclear Regulatory Commission Enforcement Manual, Appendix F, Notice of Enforcement Discretion, dated October 1, 2019 (ADAMS Accession No. ML19193A023).

5. NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 9.2.5, Ultimate Heat Sink, Revision 2, July 1981 (ADAMS Accession No. ML052350549).

Principle Contributor: Gordon Curran Chang Li Robert Beaton Date of issuance: September 24, 2020

B. Hanson

SUBJECT:

BRAIDWOOD STATION, UNITS 1 AND 2, - ISSUANCE OF AMENDMENTS NOS. 218 AND 218 RE: REVISION OF TECHNICAL SPECIFICATIONS FOR THE ULTIMATE HEAT SINK (EPID L-2020-LLA-0159)

DATED SEPTEMBER 24, 2020 DISTRIBUTION:

PUBLIC PM File Copy RidsNrrDssStsb Resource RidsRgn3MailCenter Resource RidsNrrDorlLpl3 Resource RidsNrrLASRohrer Resource RidsNrrPMBraidwood Resource RidsACRS_MailCTR Resource RidsNrrDssScpb Resource RidsNrrDssSnsb Resource ADAMS Accession No. ML20245E419 *via e-mail OFFICE NRR/DORL/LPL3/PM* NRR/DORL/LPL3/LA* NRR/DSS/STSB/BC* NRR/DSS/SCPB/BC*

NAME JWiebe SRohrer VCusumano* BWittick*

DATE 09/08/2020 09/03/2020 09/03/2020 08/24/2020 OFFICE NRR/DSS/SNSB/BC OGC* NRR/DORL/LPL3/BC* NRR/DORL/LPL3/PM*

NAME SKrepel* DRoth NSalgado (RKuntz for) JWiebe DATE 08/24/2020 09/21/2020 09/24/2020 09/24/2020