RS-21-060, Post-Shutdown Decommissioning Activities Report

Post-Shutdown Decommissioning Activities Report

ML21209A031
Person / Time
Site:	Byron
Issue date:	07/28/2021
From:	Simpson P Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation
References
RS-21-060
Download: ML21209A031 (1)

Text

Exelon Generation 4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office 10 CFR 50.82(a)(4)

RS-21-060 July 28, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Byron Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454. STN 50-455. and 72-068 Byron Station, Units 1 and 2 - Post-Shutdown Decommissioning Activities Report

References:

1)

Letter from J. Bradley Fewell (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Certification of Permanent Cessation of Power Operations for Byron Station, Units 1 and 2," dated September 2, 2020 (NRC Accession No. ML20246G613)

2)

Regulatory Guide 1.185, Revision 1, "Standard Format and Content for Post-Shutdown Decommissioning Activities Report," dated June 2013 (NRC Accession No ML13140A038)

Pursuant to 10 CFR 50.82(a)(4)(i), Exelon Generation Company, LLC (Exelon) is submitting the post-shutdown decommissioning activities report (PSDAR) for Byron Station, Units 1 and 2. On September 2, 2020, Exelon informed the U.S. Nuclear Regulatory Commission (NRC) that Byron will permanently cease power operations on or before September 30, 2021 (Reference 1 ). In accordance with 10 CFR 50.82(a)(4)(i), Exelon is required to submit a PSDAR and site specific Decommissioning Cost Estimate (DCE) and in accordance with 10 CFR 50.54(bb) a Spent Fuel Management Plan (SFMP), all within two years of permanent cessation of operations.

The Attachment to this letter provides the Byron PSDAR. The Byron SFMP and DCE are being submitted separately.

The PSDAR has been developed consistent with Regulatory Guide 1.185, Revision 1, "Standard Format and Content for Post-Shutdown Decommissioning Activities Report" (Reference 2). The Byron PSDAR includes: 1) a description of the planned decommissioning activities; 2) a schedule for their accomplishment; 3) a summary of the site specific decommissioning cost estimate; and 4) a discussion that provides a basis for concluding that the environmental impacts associated with site specific decommissioning will be bounded by appropriate, previously issued, environmental impact statements. The PSDAR also includes a discussion of the schedule and costs associated with the management of spent fuel and site restoration.

July 28, 2021 U.S. Nuclear Regulatory Commission Post-Shutdown Decommissioning Activities Report Page 2 In accordance with 10 CFR 50.82(a)(4)(i), a copy of the Byron PSDAR is being provided to the State of Illinois by transmitting a copy of this letter and its attachment to the designated State Officials.

This letter contains no new regulatory commitments.

If you have any questions concerning this submittal, please contact John Hilditch at (267) 533-5120.

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

Attachment:

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report cc:

w/Attachment Regional Administrator - NRC Region Ill NRC Senior Resident Inspector-Byron Station NRC Project Manager, NRR - Byron Station Illinois Emergency Management Agency - Division of Nuclear Safety

Attachment Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report

POST-SHUTDOWN DECOMMISSIONING ACTIVITIES REPORT (PSDAR)

Byron Station, Units 1 and 2 July 2021

Contents Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report ACRONYMS............................................................................................................................................. 1 1 INTRODUCTION AND

SUMMARY

..................................................................................................... 3 1.1 Introduction................................................................................................................................. 3 1.2 General Description.................................................................................................................... 4 1.3 Summary of Decommissioning Alternatives............................................................................... 4 2 DESCRIPTION OF PLANNED DECOMMISSIONING ACTIVITIES.................................................... 7 2.1 Discussion of Decommissioning Activities.................................................................................. 9 2.1.1 Preparations for Dormancy......................................................................................... 10 2.1.2 Dormancy................................................................................................................... 12 2.1.3 Decommissioning Preparations.................................................................................. 12 2.1.4 Decommissioning Operations (Active Decontamination and Dismantlement)............ 12 2.1.5 Site Restoration.......................................................................................................... 14 2.2 General Decommissioning Considerations............................................................................... 15 2.2.1 Major Decommissioning Activities.............................................................................. 15 2.2.2 Decontamination and Dismantlement Activities.......................................................... 16 2.2.3 Radioactive Waste Management................................................................................ 16 2.2.4 Removal of Mixed Wastes.......................................................................................... 16 2.2.5 Site Characterization.................................................................................................. 17 2.2.6 Groundwater Protection and Radiological Decommissioning Records Program........ 17 2.2.7 Changes to Management and Staffing....................................................................... 17 3 SCHEDULE OF PLANNED DECOMMISSIONING ACTIVITIES...................................................... 18 4 ESTIMATE OF EXPECTED DECOMMISSIONING AND SPENT FUEL MANAGEMENT COSTS.. 19 4.1 Cost Estimate Adjustments....................................................................................................... 20 4.2 Means of Adjusting Cost Estimates and Associated Funding Levels....................................... 20 5 ENVIRONMENTAL IMPACTS........................................................................................................... 21 5.1 Environmental Impact of Byron Decommissioning................................................................... 22 5.1.1 Onsite I Offsite Land Use........................................................................................... 22 5.1.2 WaterUse................................................................................................................... 23 5.1.3 Water Quality.............................................................................................................. 24 5.1.4 Air Quality................................................................................................................... 25 Page i of ii

5.1.5 5.1.6 5.1.7 5.1.8 5.1.9 5.1.10 5.1.11 5.1.12 5.1.13 5.1.14 5.1.15 5.1.16 5.1.17 5.1.18 Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Aquatic Ecology.......................................................................................................... 26 Terrestrial Ecology...................................................................................................... 27 Threatened and Endangered Species........................................................................ 28 Radiological................................................................................................................ 30 Radiological Accidents............................................................................................... 31 Occupational Issues................................................................................................... 32 Cost............................................................................................................................ 33 Socioeconomics......................................................................................................... 33 Environmental Justice................................................................................................ 33 Cultural, Historical, and Archaeological Resources.................................................... 34 Aesthetic Issues......................................................................................................... 35 Noise.......................................................................................................................... 36 Transportation............................................................................................................ 37 Irreversible and Irretrievable Commitment of Resources........................................... 38 5.2 Environmental Impacts of License Termination - NUREG-1496.............................................. 38 5.3 Discussion of Decommissioning in the SEIS............................................................................ 39 5.4 Additional Considerations......................................................................................................... 39 5.5 Conclusions.............................................................................................................................. 39 6 REFERENCES................................................................................................................................... 41 List of Tables Table 2.1 : Decommissioning Schedule and Plant Status Summary........................................................ 8 Table 2.2: Decommissioning Cost Summary............................................................................................ 9 Table 5.1: Protected Species Potentially Occuring in Byron Vicinity Through 2020............................. 288 Table 5.2: Estimated Radioactive Waste Associated with Byron Decommissioning............................ 377 Page ii of ii

AIF A LARA BMP CFR CWA D&D DCE DOE DSAR DTF EcoCAT ER-OLS Exelon FES FP FSS GEIS GTCC GW HVAC IAC IAS llAS IDNR IEPA IL-SH PO IPaC ISFSI LLC Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report ACRONYMS Atomic Industrial Forum As Low as Reasonably Achievable Best Management Practices Code of Federal Regulations Clean Water Act Decontamination and Dismantlement Decommissioning Cost Estimate Department of Energy Defueled Safety Analysis Report [the UFSAR is commonly referred to as the DSAR during decommissioning]

Decommissioning Trust Fund Ecological Compliance Assessment Tool (Illinois Department of Natural Resources]

Byron Station Environmental Report Operating License Stage Exelon Generation Company, LLC Final Environmental Statement related to the proposed Byron Station Units 1 and 2 Fire Protection Final Status Survey Generic Environmental Impact Statement on Decommissioning of Nuclear Facilities (NUREG-0586)

Greater than Class C Groundwater Heating Ventilating Air Conditioning Illinois Administrative Code Illinois Archaeological Survey Illinois Inventory of Archaeological Sites Illinois Department of Natural Resources Illinois Environmental Protection Agency Illinois State Historic Preservation Office Information for Planning and Consultation [United States Fish and Wildlife Service]

Independent Spent Fuel Storage Installation Limited Liability Company Page 1 of 42

LLRW LTP MARSSIM MWt NEI NESP NPDES NPS NRG NRHP ODCM OSHA PS DAR PWR REMP ROW SEIS SFP SS Cs UFSAR USAGE USFWS Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Low-Level Radioactive Waste License Termination Plan Multi-Agency Radiation Survey and Site Investigation Manual Megawatt-thermal Nuclear Energy Institute National Environmental Studies Project National Pollutant Discharge Elimination System United States National Park Service United States Nuclear Regulatory Commission National Register of Historic Places Offsite Dose Calculation Manual Occupational Safety and Health Administration Post-Shutdown Decommissioning Activities Report Pressurized Water Reactor Radiological Environmental Monitoring Program Right-of-way Generic Environmental Impact Statement for License Renewal of Nuclear Plants (NUREG-1437), Supplement 54, "Regarding Byron Station, Units 1 and 2" Spent fuel pool Structures, Systems, and Components Updated Final Safety Analysis Report U.S. Army Corps of Engineers United States Fish and Wildlife Service Page 2 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 1

INTRODUCTION AND

1.1 INTRODUCTION

In accordance with the requirements of Title 10 of the Code of Federal Regulations (CFR), Part 50, Section 50.82, "Termination of license," paragraph (a)(4)(i), [10 CFR 50.82(a)(4)(i)] this report constitutes the Post-Shutdown Decommissioning Activities Report (PSDAR) for the Byron Station, Units 1 and 2 (Byron). This PSDAR addresses the following:

1.

A description of the planned decommissioning activities along with a schedule for their accomplishment.

2.

A discussion that provides the reasons for concluding that the environmental impacts associated with site-specific decommissioning activities will be bounded by appropriate previously issued environmental impact statements.

3.

A summary of the site-specific decommissioning cost estimate (DCE), including the projected cost of managing spent fuel and the post-decommissioning site restoration cost. The site specific DCE will be submitted to the NRC under a separate cover letter.

The PSDAR has been developed consistent with Regulatory Guide 1.185, "Standard Format and Content for Post-Shutdown Decommissioning Activities Report," (Reference 1 ). This report is based on currently available information and the plans discussed herein may be modified as additional information becomes available or conditions change. As required by 10 CFR 50.82(a)(7), Exelon Generation Company, LLC (Exelon) will notify the Nuclear Regulatory Commission (NRC) in writing, with copies sent to the State of Illinois, before performing any decommissioning activity inconsistent with, or making any significant schedule change from, those actions and schedules described in the PSDAR, including changes that significantly increase the decommissioning cost. Additionally, to comply with its continuing obligation under 10 CFR 50.82(a)(6)(ii) to assure that any decommissioning activity that would result in significant environmental impacts would be previously reviewed by the NRC, Exelon will provide the NRC with updates of site-specific impact assessments after decommissioning activities that could cause such effects have been finally determined and scheduled.

A brief history of the major milestones related to Byron Station construction and operational history is as follows:

Construction Permit Issued:

Full Term Operating License Issued:

Commercial Operation:

Original License Expiration:

Renewed License Expiration:

Unit 1 12/31/1975 2/14/1985 9/16/1985 10/31/2024 10/31/2044 Unit 2 12/31/1975 1/30/1987 8/2/1987 11/6/2026 11/6/2046 By letter dated September 2, 2020 (Reference 2), Exelon provided formal notification to the NRC that it intended to permanently cease power operations of Byron Station on or before September 30, 2021, in accordance with 10 CFR 50.82(a)(1 )(i) and 10 CFR 50.4(b)(8). Upon docketing of the certifications required by CFR 50.82(a)(1 )(i) and 10 CFR 50.82(a)(1 )(ii),

pursuant to 10 CFR 50.82(a)(2), the 10 CFR Part 50 licenses for Byron will no longer authorize operation of the reactor or emplacement or retention of fuel in the reactor vessel.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Pursuant to 10 CFR 50.51 (b), "Continuation of license," the license for a facility that has permanently ceased operations continues in effect beyond the expiration date to authorize ownership and possession of the utilization facility until the Commission notifies the licensee in writing that the license has been terminated.

During the period that the license remains in effect, 10 CFR 50.51 (b) requires that the licensee:

Take actions necessary to decommission and decontaminate the facility and continue to maintain the facility including, where applicable, the storage, control, and maintenance of the spent fuel in a safe condition, and Conduct activities in accordance with all other restrictions applicable to the facility in accordance with NRG regulations and the 10 CFR Part 50 facility license.

1 O CFR 50.82(a)(9) states that all power reactor licensees must submit an application for termination of the license at least two years prior to the license termination date and that the application must be accompanied or preceded by a license termination plan to be submitted for NRG approval.

1.2 GENERAL DESCRIPTION Byron Station, Units 1 and 2 is located in northern Illinois, 3.7 miles south-southwest of the city of Byron, and 2.2 miles east of the Rock River, in Ogle County. The site is situated in the approximate center of the county in a predominately agricultural area. The site is located entirely within one political division, Rockvale Township. The station site is roughly rectangular in shape, with the plant structures occupying the southeast portion of the site.

The Byron Station occupies approximately 1782 acres of land. This area consists of the main site area and the transmission and pipeline corridor to the Rock River. The main site area occupies approximately 1398 acres, while the corridor occupies the remaining 384 acres.

Byron Station consists of two nearly identical generating units consisting of two pressurized water reactors (PWR) and turbine-generators furnished by Westinghouse Electric Corporation (Westinghouse). Unit 1 contains steam generators supplied by Babcock & Wilcox and Unit 2 contains steam generators supplied by Westinghouse. Cooling for the plant is provided by two natural draft cooling towers for nonessential service water cooling, and by mechanical draft cooling towers for essential cooling.

The principal structures of Byron include the containment buildings, turbine generator buildings, fuel handling building, the river screen house structure, the FLEX Storage Facility, two natural draft cooling towers, circulating water pump house, waste storage and handling buildings, the long-term steam generator storage building, and administrative buildings.

1.3

SUMMARY

OF DECOMMISSIONING ALTERNATIVES The NRG has evaluated the environmental impacts of three general methods for decommissioning power reactor facilities in NUREG-0586, "Generic Environmental Impact Statement on Decommissioning of Nuclear Facilities: Supplement 1, Regarding the Decommissioning of Nuclear Power Reactors" (GEIS) (Reference 3). The three general methods evaluated are summarized as follows:

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report DEGON: The equipment, structures and portions of the facility and site that contain radioactive contaminants are promptly removed or decontaminated to a level that permits termination of the license shortly after cessation of operations.

SAFSTOR: After the plant is shut down and defueled, the facility is placed in a safe, stable condition and maintained in that state (safe-storage). The facility is decontaminated and dismantled at the end of the storage period to levels that permit license termination. During SAFSTOR, a facility is left intact or may be partially dismantled, but the fuel is removed from the reactor vessel and radioactive liquids are drained from systems and components and then processed. Radioactive decay occurs during the SAFSTOR period, thereby lowering the level of contamination and radioactivity that must be disposed of during decontamination and dismantlement.

ENTOMB: Radioactive structures, systems, and components (SSCs) are encased in a structurally long-lived substance, such as concrete. The entombed structure is appropriately maintained, and continued surveillance is carried out until the radioactivity decays to a level that permits termination of the license.

The decommissioning approach that has been selected by Exelon for Byron is the SAFSTOR method. The primary objectives of the Byron decommissioning project are to remove the facility from service, reduce residual radioactivity to levels permitting unrestricted release, restore the site, perform this work safely, and complete the work in a cost-effective manner. The selection of a preferred decommissioning method is influenced by a number of factors at the time of plant shutdown. These factors include the cost of each decommissioning method, minimization of occupational radiation exposure, availability of a Department of Energy (DOE) high-level waste (spent fuel) repository or a consolidated interim storage facility, regulatory requirements, and public concerns. In addition, 10 CFR 50.82(a)(3) requires decommissioning to be completed within 60 years of permanent cessation of operations.

Currently, Exelon plans to store the spent fuel in the spent fuel pool (wet storage) until ISFSI expansion construction is completed, which is scheduled to occur in 2035. Then, spent fuel will be transferred to the ISFSI for dry storage until it can be transported offsite. Finally, the facility will be decontaminated and dismantled to levels that allow unrestricted release of the property.

In accordance with 10 CFR 50.82(a)(9), a license termination plan will be developed and submitted for NRC approval at least two years prior to termination of the license.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report The decommissioning approach for Byron is described in the following sections.

Section 2.0 describes the planned decommissioning activities and the general timing of their implementation.

Section 3.0 describes the overall decommissioning schedule, including the spent fuel management activities.

Section 4.0 provides an analysis of expected decommissioning costs, including the costs associated with spent fuel management and site restoration.

Section 5.0 describes the basis for concluding that the environmental impacts associated with decommissioning Byron are bounded by appropriate, previously issued environmental impact statements.

Section 6.0 is a list of references.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 2

DESCRIPTION OF PLANNED DECOMMISSIONING ACTIVITIES Exelon is currently planning to decommission Byron using a SAFSTOR method. SAFSTOR is broadly defined in Section 1.3 of this report. Management of spent fuel will be required over an extended period because of the DOE's failure to perform its spent fuel removal obligations under its contract with Exelon. To explain the basis for projecting the cost of managing spent fuel, a discussion of spent fuel management activities for the site is included herein.

The initial decommissioning transition activities to be performed after plant shutdown will entail preparing the plant for a period of safe-storage (also referred to as dormancy). This will entail de-fueling the reactors and transferring the spent fuel into the spent fuel pool, draining fluids from and de-energizing systems that are no longer required, reconfiguring the electrical distribution, ventilation, heating, and fire protection systems, and minor deconstruction activities.

Systems temporarily needed for continued operation of the spent fuel pool may be reconfigured for operational efficiency.

During dormancy, Byron will be staffed with personnel that will monitor, maintain, and provide security for plant facilities and the ISFSI. Staffing and configuration requirements are expected to change during the period of dormancy, principally dependent upon the status of on-site spent fuel storage, which can be characterized as follows:

Wet storage in the spent fuel pool; Dry storage in the ISFSI; and No fuel on site.

Spent fuel will initially remain in the spent fuel pool. The spent fuel will then be transferred to dry storage in the ISFSI. After all the spent fuel has been transferred to the ISFSI, the spent fuel pool and supporting systems will be drained and de-energized for the remainder of the dormancy period. The spent fuel will be stored in the ISFSI until it is transferred offsite to a consolidated interim storage facility or a DOE repository.

Decontamination and dismantlement (D&D) activities will be scheduled to enable the license to be terminated within 60 years after permanent cessation of operations. Following completion of the D&D activities, the NRC license will be terminated, and site restoration will be performed to place the site in a condition acceptable for beneficial reuse. Although Exelon is not obligated to restore the site to a greenfield condition, for purposes of this PSDAR, Exelon conservatively has made an assumption that includes restoration of the site to a greenfield condition, but that conservative assumption is not a commitment to do so. Site restoration is anticipated to be performed to place the site in a condition acceptable for beneficial reuse. The current decommissioning cost estimate assumes that remaining structures will be demolished to three (3) feet below grade and that the excavations will be backfilled with suitable material and erosion controls emplaced.

Exelon will complete radiological decommissioning and spent fuel management as required by NRC regulations and will determine the extent of site restoration at a later date.

Decommissioning activities will be performed in accordance with written, reviewed, and approved site procedures. There are no identified or anticipated decommissioning activities that are unique to the Byron site.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Compliance with applicable regulatory programs will be maintained throughout the decommissioning process to ensure the health and safety of workers, the public, and the environment. Radiological monitoring programs will be conducted in accordance with the facility's revised Technical Specifications, Renewed Facility License, Updated Final Safety Analysis Report/Defueled Safety Analysis Report (UFSAR/DSAR), Radiological Environmental Monitoring Program (REMP), and the Offsite Dose Calculation Manual (ODCM). Non-radiological environmental monitoring programs will be conducted in accordance with applicable regulatory requirements and permits.

Tables 2.1 and 2.2 below summarizes the schedule I plant status and costs for decommissioning Byron. The major decommissioning activities and general sequence are discussed in more detail in the sections that follow.

Table 2.1:

Decommissioning Schedule and Plant Status Summary Plant Status I Decommissioning Approximate Start End Duration Activities (years)

Pre-Shutdown Pre-Shutdown Planning Jan 2021 Sep 2021 0.7 Preparations for Dormancy Plant Shutdown I Defueling Outage Sep 2021 Oct 2021 0.1 Preparations for Dormancy Sep 2021 May 2023 1.6 Dormancy Dormancy w/ Wet Fuel Storage May 2023 Dec 2037 14.6 Dormancy w/ Dry Fuel Storage Jan 2038 Mar 2043 5.2 Fuel Shipping Apr2043 Dec 2046 3.8 Dormancy w/ No Fuel Jan 2047 Apr2074 27.3 Decommissioning Preparations May 2074 May 2075 1.0 Decommissioning Operations Large Component Removal May 2075 Dec 2078 3.6 Plant Systems Removal and Dec 2078 Dec 2080 2.0 Building Decontamination License Termination Dec 2080 Sep 2081 0.8 Total from Shutdown to Completion of License 60 Termination Site Restoration Sep 2081 Mar 2084 2.5 Page 8 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Table 2.2:

Decommissioning Cost Summary (December 31, 2020, dollars - thousands)

Decommissioning Periods Radiological Decommissioning Pre-Shutdown Pre-Shutdown Planning [aJ 13,942 Preparations for Dormancy Plant Shutdown I Defueling Outage 1220 Preparations for Dormancy 194, 157 Dormancy Dormancy w/ Wet Fuel Storage 403,373 Dormancy w/ Dry Fuel Storage 49,406 Fuel Shipping 27,442 Dormancy w/ No Fuel 225,983 Decommissioning Preparations 74,325 Decommissioning Operations Large Component Removal 535,237 Plant Systems Removal and 218,544 Building Decontamination License Termination 29,720 Site Restoration TotallbJ 1,773,350 2.1 DISCUSSION OF DECOMMISSIONING ACTIVITIES Spent Fuel Management 321 584,422 20,572 39,997 645,311 Site Restoration 184 217 183 185 14,628 13,220 168,337 196,954 The following narrative describes the basic activities associated with decommissioning Byron.

The site specific DCE, as further discussed in Section 4, is divided into phases or periods based upon major milestones within the project or significant changes in the annual projected expenditures. The following sub-sections correspond to the major decommissioning periods within the estimate.

Costs represent projected spend in 2021 only.

Columns may not add due to rounding Page 9 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 2.1.1 Preparations for Dormancy The NRC defines SAFSTOR as, "A method of decommissioning in which a nuclear facility is placed and maintained in a condition that allows the facility to be safely stored and subsequently decontaminated (deferred decontamination) to levels that permit release for unrestricted use."

The facility is left intact (during the dormancy period), with most structures maintained in a stable condition; some outbuildings not related to power production will be removed. Systems that are not required to support the spent fuel, HVAC, Emergency Plan, or site security are drained, de-energized, and secured. Some cleaning I removal of loose contamination and or fixation and sealing of remaining contamination is performed. Access to contaminated areas is maintained secure to provide controlled access for inspection and maintenance.

The process of placing the plant in safe-storage will include, but is not limited to, the following activities:

Creation of an organizational structure to support the decommissioning plan and evolving emergency planning and site security requirements.

Revision of Technical Specifications, plans, and operating procedures appropriate to the operating conditions and requirements.

Characterization of the facility and major components as may be necessary to plan and prepare for the dormancy phase.

Management of the spent fuel pool and reconfiguring spent fuel pool support systems so that draining and de-energizing may commence in other areas of the plant.

Deactivation (de-energizing and/or draining) of systems that are no longer required during the dormancy period.

Processing and disposal of water and water filter and treatment media (resins) not required to support dormancy operation.

Expansion of the ISFSI and acquisition of the dry fuel storage casks for off-load of the spent fuel pool.

Disposition of incidental waste that may be present and is ready to ship prior to the start of the dormancy period, such as excess tools and equipment and waste produced while deactivating systems and preparing the facility for dormancy.

Reconfiguration of power, lighting, heating, ventilation, fire protection, and any other services needed to support long-term storage and periodic plant surveillance and maintenance.

Stabilization by fixing or removing loose incidental surface contamination to facilitate future building access and plant maintenance. Decontamination of high-dose areas is not anticipated.

Performance of interim radiation surveys of the plant, posting caution signs and establishing access requirements, where appropriate.

Maintenance of appropriate barriers for contaminated and radiation areas.

Reconfiguration of security boundaries and surveillance systems, as needed to support efficiency during the dormancy period.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report The following is a general discussion of the planned reconfiguration expected after plant shutdown.

2. 1. 1. 1 Electrical Systems The electrical systems will undergo a series of reconfigurations between shutdown and the time all spent fuel has been transferred to the ISFSI. The reconfigurations will be performed to reduce operating and maintenance expenses, while maintaining adequate power for station loads, and backup power for spent fuel pool-related systems and critical security equipment.

2. 1. 1. 2 Mechanical Systems Following shutdown, as applicable, fluid filled systems will be placed in layup conditions, drained and abandoned, and resins removed based on an evaluation of system category, functionality, and plant configuration. The plant configuration and functionality of each system within the plant configuration as it evolves will determine when a system can be drained and abandoned.

2.1.1.3 Ventilation and Heating Systems Ventilation will be reconfigured to support remaining systems and habitability. Fluid filled systems will either be drained or freeze protection installed, and the heating steam secured. The ventilation system will be reconfigured to maintain building temperature to support habitability and the functioning of Spent Fuel Pool Cooling systems, Fire Protection systems, Security systems, and Dry Fuel Storage systems as needed.

2. 1. 1. 4 Fire Protection Systems Fire Protection (FP) systems will be reconfigured based on a fire hazards analysis. The fire hazards analysis provides a comprehensive evaluation of the facility's fire hazards, the fire protection capability relative to the identified hazards, and the ability to protect spent fuel and other radioactive materials from potential fire induced releases. The fire hazards analysis will be reevaluated and revised as necessary to reflect the unique or different fire protection issues and strategies associated with decommissioning. It is expected that as the plant's systems are drained and the combustible loading footprint shrinks, the FP requirements will be reduced.

2. 1. 1. 5 Maintenance of Systems Critical to Decommissioning There are no mechanical systems that will be critical to the final decommissioning process. As such, mechanical systems will be abandoned as appropriate. All mechanical systems required to safely maintain the spent fuel in the spent fuel pool will be maintained while the spent fuel is in wet storage. Those mechanical systems will then be abandoned after all spent fuel has been transferred to the ISFSI, with the exception of systems required to maintain habitability during dormancy. The site power distribution system will be abandoned with the possible exception of motor control centers that are required to support ventilation and lighting.

The organization responsible for the final dismantlement will be expected to establish temporary services, including electrical and cranes.

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2.1.2 Dormancy Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Activities required during the early dormancy period while spent fuel is stored in the spent fuel pool will be substantially different than those activities required during dry fuel storage.

Early activities include operating and maintaining the spent fuel pool and its associated systems, and transferring spent fuel from the spent fuel pool to the ISFSI. Once the ISFSI expansion is complete (estimated in 2035), the spent fuel will be transferred from the spent fuel pool to the ISFSI. Spent fuel transfer to the ISFSI is expected to be complete in 2037. After all of the spent fuel is removed from the spent fuel pool, the spent fuel pool and supporting systems will be drained and de-energized for long-term storage.

Dormancy activities will include security, preventive and corrective maintenance on security systems, area lighting, general maintenance of buildings, freeze protection heating, ventilation of buildings for periodic habitability, routine radiological inspections of contaminated structures, maintenance of structural integrity, and a site environmental and radiation monitoring program.

A 24-hour/7-day per week security force will be present during the dormancy period. Security during the dormancy period will be conducted primarily to safeguard the spent fuel stored on site and prevent unauthorized entry. Security barriers, sensors, alarms, and other surveillance equipment will be maintained as required to provide security.

An environmental surveillance program will be carried out during the dormancy period to monitor for radioactive material in the environment. Appropriate procedures will be established and initiated for potential releases that exceed prescribed limits. The environmental surveillance program will consist of a version of the program in effect during normal plant operations that will be modified to reflect the plant's conditions and risks at the time.

During the dormancy period, additional activities will include transferring the spent fuel from the ISFSI to the DOE. For planning purposes, Exelon's Spent Fuel Management Plan reflects the dates described in Table 2.1. It is acknowledged that the plant owner will seek the most expeditious means of removing spent fuel from the site when DOE commences spent fuel receipt. The ISFSI pad and associated facilities will be decommissioned along with the power block structures during the decontamination and dismantlement phase.

2.1.3 Decommissioning Preparations Prior to the commencement of decommissioning operations, preparations will be undertaken to reactivate site services and prepare for decommissioning. Preparations include engineering and planning, a site characterization, and the assembly of a decommissioning management organization. This would likely include the development of work plans, specifications, and procedures.

2.1.4 Decommissioning Operations (Active Decontamination and Dismantlement)

Following the preparations for decommissioning, physical decommissioning activities will take place. This includes the removal and disposal of contaminated and activated components and structures, leading to the termination of the 10 CFR 50 operating licenses. Although much of the radioactivity will decrease during the dormancy period due to decay of 6°Co and other short-Page 12 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report lived radionuclides, the internal components of the reactor vessels will still exhibit radiation dose rates that will likely require remote sectioning under water due to the presence of long-lived radionuclides such as 94Nb, 59Ni, and 63Ni. Portions of the biological shield walls may also be radioactive due to the presence of activated trace elements with longer half-lives (such as 152Eu and 154Eu). It is assumed that radioactive contamination on SSC surfaces will not have decayed to levels that will permit unrestricted release. These surfaces will be surveyed, and items dispositioned in accordance with the license termination release criteria.

Significant decommissioning activities in this phase include:

Reconfiguration and modification of site structures and facilities, as needed, to support decommissioning operations. Modifications may also be required to the containment or other buildings to facilitate movement of equipment and materials, support the segmentation of the reactor vessels and reactor vessel internals, and for large component removal.

Design and fabrication of temporary and longer-term shielding to support removal and transportation activities, construction of contamination control envelopes, and the procurement of specialty tooling.

Procurement or leasing of shipping cask, cask liners, and industrial packages for the disposition of low-level radioactive waste.

Disposition of legacy waste, including retired Steam Generators and Hot Leg piping.

Decontamination of components and piping systems, as required, to control worker exposure to levels as low as reasonably achievable.

Removal of piping and components no longer essential to support decommissioning operations.

Removal of control rod drive housings and the head service structures from reactor vessel heads. Segmentation of the vessel closure heads.

Removal and segmentation of the plenum assemblies. Segmentation will maximize the loading of the shielded transport casks (i.e., by weight and activity). The segmentation operations will be conducted underwater using remotely operated tooling and contamination controls.

Disassembly and segmentation of the remaining reactor internals, including the core barrel and lower core support assembly. Some material is expected to exceed Class C disposal requirements. As such, the segments will be packaged in modified fuel storage canisters for future geologic disposal.

Removal of the Reactor Vessels. If segmentation of the reactor vessels is necessary, a shielded platform will be installed for cutting operations, which will be performed using remotely operated equipment within a contamination control envelope.

Removal of the activated portions of the concrete biological shields and accessible contaminated concrete surfaces. If dictated by the steam generator and pressurizer removal scenarios, those portions of the secondary shield wall necessary for access and component extraction will be removed.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Removal of the steam generators and pressurizers for material recovery and controlled disposal. The steam generators will be moved to an on-site processing center and prepared for transport to the waste processor. It may be necessary to cut the steam generators in half, across the tube bundles, with the exposed ends capped and sealed to facilitate transport. It is expected that the pressurizers will be disposed of intact.

Remediation and removal of the contaminated equipment and material from the auxiliary building and any other contaminated areas. Radiation and contamination controls will be utilized until residual levels indicate that the structures and equipment can be released for unrestricted access and conventional demolition. This activity may necessitate the dismantling and disposition of most of the systems and components (both clean and contaminated) located within these buildings. This activity facilitates surface decontamination and subsequent verification surveys required prior to obtaining release for demolition.

Surface soil, sub-surface media and groundwater will meet the unrestricted use criteria in 10 CFR 20.1402.

Underground piping (or similar items) and associated soil will be removed as necessary to meet license termination criteria.

At least two years prior to the anticipated dates of each license termination, a License Termination Plan (L TP) will be submitted to the NRC. That plan will include: a site characterization, description of the remaining dismantling I removal activities, plans for remediation of remaining radioactive materials, developed site-specific Derived Concentration Guideline Levels, methodology and criteria for the final status (radiation) survey (FSS),

designation of the end use of the site, an updated cost estimate to complete the decommissioning, and associated environmental concerns.

The FSS plan will identify the radiological surveys to be performed once the decontamination activities are completed, and it will be developed using the guidance provided in NUREG-1575, "Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)" (Reference 16). As stated in the abstract to the MARSSIM, 'The MARSSIM provides information on planning, conducting, evaluating, and documenting building and surface soil final status radiological surveys for demonstrating compliance with dose or risk-based regulations or standards." The MARSSIM uses the Data Quality Objective I Analysis processes tool for data collection activities and provides a basis for balancing decision uncertainty with available resources. This document incorporates statistical approaches to survey design and data evaluation. It also identifies commercially available instrumentation and procedures for conducting radiological surveys. Use of this guidance ensures that the surveys are conducted in a manner that provides a high degree of confidence that applicable NRC criteria are satisfied. Once the FSS is complete, the results will be submitted to the NRC, along with a request for termination of the NRC license.

Exelon may release unaffected portions of the site on a partial site release basis, as they become available, before all site decommissioning work has been completed.

2.1.5 Site Restoration Site restoration is assumed to begin after license termination, at the licensee's discretion.

Exelon currently assumes that all remaining structures will be removed to a nominal depth of Page 14 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report three feet below the surrounding grade level. Affected area(s) would then be backfilled with suitable fill materials, graded, and appropriate erosion controls established.

Non-contaminated concrete remaining after the demolition activities may be used for backfilling subsurface voids or may be transported to an offsite area for appropriate disposal as construction debris.

Although Exelon is not obligated to restore the site to a greenfield condition, for purposes of this PS DAR, Exelon conservatively has made an assumption that includes restoration of the site to a greenfield condition, but that conservative assumption is not a commitment to do so. Exelon will complete radiological decommissioning and spent fuel management as required by NRC regulations and will determine the extent of site restoration at a later date.

2.2 GENERAL DECOMMISSIONING CONSIDERATIONS 2.2.1 Major Decommissioning Activities As defined in 10 CFR 50.2, "definitions," a "major decommissioning activity" is "any activity that results in permanent removal of major radioactive components, permanently modifies the structure of the containment, or results in dismantling components for shipment containing greater than class C waste in accordance with§ 61.55 of this chapter." The following discussion provides a summary of the major decommissioning activities currently planned for decommissioning Byron. These activities are envisioned to occur in the Decommissioning Operations Period. The schedule may be modified as conditions dictate.

Prior to starting a major decommissioning activity, the affected components will be surveyed and decontaminated, as required, in order to minimize worker exposure, and a plan will be developed for the activity. Shipping casks and other equipment necessary to conduct major decommissioning activities will be procured.

The following approach will be similar for both Byron Unit 1 and Byron Unit 2.

The initial major decommissioning activity inside the containment building will be the removal, packaging, and disposal of systems and components attached to the reactor, to provide access and allow it to be removed.

The reactor vessel internals will be removed from the reactor vessel and segmented, if necessary, for packaging, transport, and disposal, or to separate greater than Class C (GTCC) waste. Internals classified as GTCC waste will be segmented and packaged into containers similar to spent fuel canisters for storage at the ISFSI and/or transfer to the DOE. Removal of the reactor vessel follows the removal of the reactor vessel internals. Industry experience indicates that there may be several options available for the removal and disposal of the reactor vessel (i.e., segmentation or disposal as an intact package). The viability of these options will be analyzed as a part of future planning and preparation activities. If the reactor vessel is segmented, it is likely that the work would be performed remotely using a contamination control envelope.

2. 2. 1. 1 Other Decommissioning Activities Page 15 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Other major decommissioning activities that would be conducted include the removal and disposal of the turbine, condenser, pressurizer, steam generators, reactor coolant piping, reactor coolant pumps and motors, spent fuel pool support equipment, and neutron activated I contaminated concrete or metals.

In addition to the reactor and large components discussed above, all other plant components will be removed from the Containment, Auxiliary, Turbine, and associated support buildings (including the long-term steam generator storage building), radiologically surveyed and dispositioned appropriately.

2.2.2 Decontamination and Dismantlement Activities The overall objective of D&D is to ensure that radioactively contaminated or activated materials will be removed from the site to allow the site to be released for unrestricted use. This is achieved in part by radioactive decay during the SAFSTOR period which will significantly reduce the quantity of radioactive material that must be disposed of during decontamination and dismantlement. The disposition of remaining radioactive materials will be accomplished by the decontamination and I or dismantlement of contaminated structures. This may be accomplished by decontamination in place, off-site processing of the materials, or direct disposal of the materials as radioactive waste. A combination of these methods may be utilized. The methods chosen will be those deemed most appropriate for the particular circumstances.

Low-level radioactive waste (LLRW) will be managed in accordance with approved procedures and commercial disposal facility requirements. This includes characterizing contaminated materials, packaging, transporting and disposal at a licensed LLRW disposal facility.

2.2.3 Radioactive Waste Management A major component of the decommissioning work scope for Byron is the packaging, transportation and disposing of primarily contaminated I activated equipment, piping, concrete, and in some cases soil. A waste management plan will be developed to incorporate the most cost-effective disposal strategy, consistent with regulatory requirements and disposal I processing options for each waste type at the time of the D&D activities. Decommissioning wastes from Byron may be disposed of at the Waste Control Specialists, LLC facility in Andrews, Texas and the EnergySolutions, Inc. facility in Clive, Utah. If other licensed disposal facilities become available in the future, Exelon may elect to use them. Some low-level radioactive waste may also be shipped for processing to the EnergySolutions Bear Creek Processing Facility near Oak Ridge, Tennessee. Radioactive wastes from Byron will be transported by licensed transporters. The waste management plan will be based on the evaluation of available methods and strategies for processing, packaging, and transporting radioactive waste in conjunction with the available disposal facility options and associated waste acceptance criteria.

2.2.4 Removal of Mixed Wastes If mixed wastes are generated, they will be managed in accordance with applicable federal and state regulations, and transported by authorized licensed waste transporters to authorized licensed waste management facilities. If technology, resources, and approved processes are available, these processes will be evaluated to render the mixed waste non-hazardous.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 2.2.5 Site Characterization During the decommissioning process, site characterization will be performed in which radiological, regulated, and hazardous wastes will be identified, categorized, and quantified.

Surveys will be conducted to establish hazardous and radioactive material contamination levels and radiation levels throughout the site. This information will be used in developing procedures, surveys, and sampling plans to ensure that hazardous, regulated, and radiologically contaminated areas are remediated and to ensure that worker exposure is controlled. As decontamination and dismantlement work proceeds, radiological surveys will be conducted to maintain a current site characterization and to ensure that decommissioning activities are adjusted accordingly.

As part of the site characterization process, a neutron activation analysis calculation study of the reactor internals and the reactor vessel will be performed. Using the results of this analysis (along with benchmarking surveys), neutron irradiated components will be classified (projected for the future D&D time-frame) in accordance with 10 CFR 61, "Licensing requirements for land disposal of radioactive waste." The results of the analysis form the basis of the plans for removal, segmentation, packaging, and disposal.

2.2.6 Groundwater Protection and Radiological Decommissioning Records Program A Radiological Groundwater Protection Program (RGPP) currently exists at Byron in accordance with the Nuclear Energy Institute (NEI) Technical Report 07-07, "Industry Groundwater Protection Initiative - Final Guidance Document" (Reference 4 ). This program is directed by procedures and will continue during decommissioning.

Neither the monitoring results of the radiological groundwater protection program nor events noted in 10 CFR 50.75(g) reports indicate the presence of radionuclides in concentrations sufficient to preclude unrestricted release under 10 CFR 20.1402, "Radiological criteria for unrestricted use."

Exelon will also continue to maintain the existing radiological decommissioning records program required by 10 CFR 50.75(g). The program is directed by procedures.

2.2.7 Changes to Management and Staffing Throughout the decommissioning process, plant management and staffing levels will be adjusted to reflect the ongoing transition of the site organization. Staffing levels and qualifications of personnel used to monitor and maintain the plant during the various periods after plant shutdown will be subject to appropriate Technical Specifications and Emergency Plan requirements. These staffing levels do not include contractor staffing which may be used to carry out future spent fuel activities, plant modifications in preparation for SAFSTOR, and the D&D I license termination I site restoration work. Contractors may also be used to provide general services, staff augmentation, or replace permanent staff. The monitoring and maintenance staff will be comprised of radiation protection, radiological environmental monitoring program, plant engineering and craft workers as appropriate for the anticipated work activities.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 3

SCHEDULE OF PLANNED DECOMMISSIONING ACTIVITIES Exelon intends to pursue the decommissioning of Byron utilizing a SAFSTOR methodology and will make appropriate submittals with the NRC to obtain authorization prior to beginning radiological decommissioning. The SAFSTOR method involves removal of radioactively contaminated or activated material from the site following an extended period of dormancy.

Work activities associated with the planning and preparation period began before the plant was permanently shutdown and continues until all fuel is removed from the reactor vessels and stored in the SFP. The schedule of spent fuel management and major decommissioning activities is provided in Table 2.1. Additional detail is provided in the site-specific DCE. Dates in the site-specific DCE are based on a September 2021 shutdown date. The schedule accounts for spent fuel being in wet storage and then stored in the ISFSI until the assumed date of transfer to the DOE.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 4

ESTIMATE OF EXPECTED DECOMMISSIONING AND SPENT FUEL MANAGEMENT COSTS 10 CFR 50.82(a)(4)(i) requires the submission of a PSDAR prior to or within two years following permanent cessation of operations that contains a site-specific DCE, including the projected cost of managing irradiated (also called spent) fuel.

Exelon has prepared a site specific DCE for both Byron units, which provides the site-specific projected costs of radiological decommissioning, managing spent fuel, and site restoration; each category accounted for separately. The site-specific DCE will be submitted in a separate submittal. Section 4.1 describes the projected expenditures in the DCE to produce Table 2.2.

The methodology used to develop the site-specific DCE follows the basic approach originally advanced by the Atomic Industrial Forum (AIF) in its program to develop a standardized model for DCEs. The results of this program were published as AIF/NESP-036, "A Guideline for Producing Commercial Nuclear Power Plant Decommissioning Cost Estimates," (Reference 5).

The AIF document presents a unit cost factor method for estimating direct activity costs, simplifying the estimating process. The unit cost factors used in the study reflect the latest available data, at the time of the study, concerning worker productivity during decommissioning.

Under NRC regulations (10 CFR 50.82(a)(8)), a licensee must provide reasonable assurance that funds will be available (or "financial assurance") for decommissioning (i.e., radiological decommissioning) costs. The regulations also describe the acceptable methods a licensee can use to demonstrate financial assurance. Most licensees do this by funding a nuclear decommissioning trust fund (DTF).

Exelon maintains four separate trusts for this purpose, a tax qualified fund (Qualified Trust) and a non-tax qualified fund (Non-Qualified Trust) for each unit. The trustee for all four funds is Northern Trust Bank. As of December 31, 2020, the DTF for Byron Unit 1 has a total balance of

$475,341,000 and the DTF for Byron Unit 2 has a total balance of $458,906,000 (Reference 6).

The adequacy of these funds to cover all radiological decommissioning costs shown in Table 2.2 is described in the Byron site specific DCE. As of December 31, 2020, Byron Station, Units 1 and 2 did not meet the minimum funding assurance criteria under 10 CFR 50.75, 10 CFR 50.82, and 10 CFR 72.30 using the NRC formula in 10 CFR 50.75(c) to calculate costs and based solely on the trust fund balance. Prior to permanent shutdown, Exelon will evaluate the alternate funding mechanisms allowed by 10 CFR 50.75(e)(1) and the guidance provided in Regulatory Guide 1.159, "Assuring Availability of Funds for Decommissioning Nuclear Reactors," Revision 2, (Reference 7) and will provide the NRC with additional information describing how the minimum funding requirements will be met.

The 10 CFR 50.75(c) minimum formula amount for Byron as of December 31, 2020 is

$523, 785,000 for each unit (Reference 6). The estimated cost of radiological decommissioning (including ISFSI license termination costs) at Byron Unit 1 is $880,602,000 and Byron Unit 2 is

$892,603,000. In accordance with Regulatory Guide 1.185 (Reference 1 ), the site-specific DCE exceeds the minimum formula amount.

1 O CFR 50.82(a)(6)(iii) states that, "Licensees shall not perform any decommissioning activities," as defined in 10 CFR 50.2 that, "Result in there no longer being reasonable assurance that adequate funds will be available for decommissioning." Exelon does not intend Page 19 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report to perform any decommissioning activities that would jeopardize the availability of adequate funds for the completion of decommissioning.

10 CFR 50.82(a)(8)(iv) states that, "For decommissioning activities that delay completion of decommissioning by including a period of storage or surveillance, the licensee shall provide a means of adjusting cost estimates and associated funding levels over the storage or surveillance period." Section 4.2 details how Exelon will meet this requirement.

4.1 COST ESTIMATE ADJUSTMENTS Table 2.2 reflects the projected expenditures required for decommissioning Byron Unit 1 and Byron Unit 2 from the OGE escalated to December 31, 2020 dollars. The updated projected costs for radiological decommissioning, spent fuel management, and site restoration (non-radiological decommissioning) efforts are separately reflected in Table 2.2. Items to note relative to the costs are:

(1) The OGE is in June 2020 dollars. The costs reflected in Table 2.2 have been escalated to December 31, 2020, dollars. The escalation was determined using a forecasted average annual escalation rate of 2.59% (based on the most recent data at the time of this submittal). This rate was calculated using the Employment Cost Index Total Compensation Private Industry Workers United States from the North American Industry Classification System (NAICS).

(2) Projected radiological decommissioning planning costs and spent fuel management costs incurred in 2021 prior to permanent shutdown are included in Table 2.2 under "Pre-Shutdown Planning." Decommissioning Planning costs for prior years, associated with radiological decommissioning planning performed by a dedicated site organization, are not reflected in Table 2.2.

4.2 MEANS OF ADJUSTING COST ESTIMATES AND ASSOCIATED FUNDING LEVELS During the SAFSTOR period, the site-specific OGE will be periodically updated in compliance with Exelon procedures and applicable regulatory requirements.

In accordance with 10 CFR 50.82(a)(8)(v), decommissioning funding assurance will be reviewed and reported to the NRG annually during the SAFSTOR period. The latest site specific OGE adjusted for inflation, in accordance with applicable regulatory requirements, will be used to demonstrate funding assurance. In addition, actual radiological and spent fuel management expenses will be included in the annual report in accordance with the applicable regulatory requirements.

If the funding assurance demonstration during the SAFSTOR period shows the DTF is again not sufficient, then an alternate funding mechanism allowed by 10 CFR 50.75(e) and the guidance provided in Regulatory Guide 1.159 (Reference 7) will be put in place as previously discussed in Section 4.0.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 5

ENVIRONMENTAL IMPACTS To support the PSDAR environmental impacts review, the environmental effects of decommissioning activities planned for Byron, as currently understood, were evaluated to determine if potential environmental impacts are bounded by previously issued environmental impact statements (Reference 9). NRC regulation 10 CFR 50.82(a)(4)(i) requires that the PSDAR include"... a discussion that provides the reasons for concluding that the environmental impacts associated with site-specific decommissioning activities will be bounded by appropriate previously issued environmental impact statements." To determine if the estimated potential environmental impacts associated with Byron decommissioning activities are bounded, the potential environmental impacts were compared to those in:

NUREG-0586, Final Generic Environmental Impact Statement on Decommissioning of Nuclear Facilities, Supplement 1, Regarding the Decommissioning of Nuclear Power Reactors (Reference 3) (Referred to as the Decommissioning GEIS or GEIS).

NUREG-1496, Generic Environmental Impact Statement in Support of Rulemaking on Radiological Criteria for License Termination of NRG-Licensed Nuclear Facilities (Reference 10).

Atomic Energy Commission, Final Environmental Statement related to the Proposed Byron Station Units 1 and 2 (Reference 11) (Referred to as the FES).

NUREG-1437, Generic Environmental Impact Statement for License Renewal of Nuclear Plants, Supplement 54, Regarding Byron Station Units 1 and 2 ((Reference 13)

(Referred to as the SEIS).

As required, site-specific impact assessments were conducted for threatened and endangered species and environmental justice. A site-specific assessment was conducted for the use of offsite land and site-specific assessments were also performed for aquatic ecology, terrestrial ecology, and cultural and historic resources for decommissioning activities beyond the operational area. For the purpose of assessing decommissioning environmental impacts, the Byron operational area comprises the main site area and most of the surrounding land that lies west of German Church Road, and the right-of-way extending to the Rock River containing the intake and discharge pipelines. This area encompasses the reactor and surrounding buildings, intake structure and discharge pipe, parking lots, laydown yards, landscaped maintained areas, the meteorological tower and transportation infrastructure. The levels of significance assigned to site-specific environmental impacts are classified as small, moderate, or large, as defined by NRC in the Decommissioning GEIS (Reference 3).

Byron's decommissioning plans are consistent with the methods assumed by NRC in the Decommissioning GEIS. No unique site-specific features or unique aspects of the planned decommissioning have been identified. Also, Exelon has concluded that the environmental impacts associated with planned Byron decommissioning activities are either bounded by the impacts addressed by previously issued environmental impact statements or are expected, based on site specific reviews, to be small. In the latter cases, after decommissioning plans mature and before decommissioning activities occur that could be potentially impactful to the environmental resource or would be otherwise inconsistent with those actions or activities described in the PSDAR, Exelon will notify the NRC in writing and seek appropriate environmental review in accordance with applicable NRC regulations.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 5.1 ENVIRONMENTAL IMPACT OF BYRON DECOMMISSIONING The following is a summary of the reasons for reaching the conclusions that the environmental impacts of decommissioning Byron are (1) bounded by the Decommissioning GEIS or (2) site specific, small, and bounded by other previously issued environmental impact statements, or (3) expected to be site-specific and small, and Exelon will notify the NRC in writing and seek appropriate environmental review in accordance with applicable NRC regulations before decommissioning activities occur that could be potentially impactful to the environmental resource. Each environmental resource evaluated in the GEIS is addressed. Further, no unique site-specific environmental features or unique aspects of the planned decommissioning activities have been identified.

5.1.1 Onsite I Offsite Land Use In Section 4.3.1 of the GEIS, the NRC generically determined land use impacts to be small for facilities having land-use changes only within the site boundary. For decommissioning that involves land use changes beyond the site boundary, the GEIS concluded that impacts could not be predicted generically and must be evaluated on a site-specific basis.

5. 1. 1. 1 Onsite Land Use The previously disturbed area surrounding the power block offers substantial space to support decommissioning activities. Decommissioning activities include backfill of excavations. The fill needed will be obtained from material (e.g., crushed concrete) resulting from onsite demolition.

If additional fill is needed, it could be excavated from onsite or, if more appropriate or practical, fill could also be purchased from offsite borrow areas that are approved for that land use. The Illinois Environmental Protection Agency (IEPA) regulates the use of clean construction or demolition debris as fill for certain applications. Exelon will comply with state regulations regarding the use of fill materials and will obtain permits as needed.

Exelon has determined that onsite land to be used to support decommissioning at Byron has been previously disturbed and decommissioning activities at Byron would not result in changes in onsite land use patterns. After the site is released for unrestricted use, the land could continue as industrial use or be available for other non-industrial uses. Exelon concludes that anticipated onsite land use impacts are bounded by the GEIS.

5. 1. 1. 2 Off site Land Use Exelon decommissioning activities potentially include the use of offsite land to support rail shipment of radiological waste. The offsite land is the offsite portions of the rail spur and temporary use of land near the Rock River railroad bridge for staging in the event of repair or replacement of the bridge. Exelon will comply with applicable local and state regulations and obtain and comply with any federal, state, and local permits required to support the repair of the railroad bridge. The offsite land used to support rail shipment would be used for a short duration and the land has previously been used for shipments. Any land used for temporary staging would not be a permanent land use change.

As a site restoration activity and in consultation with U.S. Army Corps of Engineers (USACE),

given its jurisdiction over the Rock River as a navigable river, Exelon would, as appropriate, Page 22 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report remove the in-river structures of its sediment management system. This activity would be outside the scope of plant decommissioning. Offsite land would be used to support the removal of the wing dams on the west bank of the Rock River and the riverbed itself is offsite. The use of offsite land would be temporary and not a permanent land use change. Exelon will obtain all required federal, state, and local permits for the work and implement any required site restoration permit conditions.

The Decommissioning GEIS determined for nuclear facilities that utilize offsite land to support decommissioning, a site-specific assessment for offsite land use is required. Because the temporary use of offsite land would not result in changes to offsite land use patterns, Exelon concludes the impact to offsite land use would be small to none.

5.1.2 Water Use The GEIS observes that quantities of water required during decommissioning are trivial compared to those used when a plant is operating. The GEIS mentions construction dust abatement and decontamination (flushing systems or pressure-washing components) as typical decommissioning water uses. NRG asserted in Section 4.3.2 of the GEIS that potential impacts of decommissioning on water use at all plants are neither detectable nor destabilizing and made the generic conclusion that impacts in all cases are small.

Byron obtains surface water from the Rock River for circulating water and service water cooling and discharges to the river downstream from the intake structure. Onsite groundwater wells supply water for domestic water consumption, cooling water makeup, and other industrial uses.

Exelon expects to reduce Rock River water and groundwater withdrawals substantially following plant shutdown. Upon plant shutdown, the discharge of waste heat via the cooling towers or to the Rock River will end, which will eliminate most evaporative losses resulting from station operation. Water consumption will be further reduced when it is no longer necessary to provide secondary cooling for the spent fuel pool. The spent fuel pool will be used until all the spent fuel is moved into dry storage. Surface water withdrawals and discharges will continue at reduced rates until the water from the spent fuel pool has been processed and released, and other plant discharges (e.g., sewage treatment effluent) dependent on the circulating water system blowdown flow are completed.

Exelon assumes the Byron service water system will be shut down when no longer required by the spent fuel pool or other plant systems, and that onsite wells will provide potable drinking water and non-potable water for a variety of uses. Based purely on staffing projections, the demand for potable water at the plant will be substantially lower during decommissioning years than during operational years, but it is conceivable that well water may also be required during decommissioning for dust abatement and decontamination. Nevertheless, Exelon expects groundwater use during Byron decommissioning to be much lower than water use during operational years, consistent with the statements made in the Decommissioning GEIS.

Because Exelon expects water use during Byron decommissioning to be much lower than water use during operational years, which is consistent with the statements made in the GEIS, and because there is nothing about Byron's design, location, configuration, operating history, or decommissioning plans that would alter or contradict this generic conclusion, Exelon concludes Page 23 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report that decommissioning water use impacts for Byron are bounded by the analysis in the GEIS.

5.1.3 Water Quality Decommissioning activities with potential for impacting surface water quality include spent fuel removal, stabilization, large component removal, decontamination and dismantlement, and structure dismantlement. Stormwater runoff and accidental releases (spills) are the most likely sources of pollutants entering surface waters during decommissioning. The GEIS asserts that regulatory programs applicable to permitted substance releases plus the application of Best Management Practices (BMPs) for controlling stormwater runoff and erosion will render any change in surface water quality from decommissioning activities non-detectable and non-destabilizing. With respect to groundwater, the GEIS noted that demolishing concrete structures and storing rubble on site could result in changes (higher alkalinity) in local water chemistry, but the non-radiological effects of such changes on water quality would be non-detectable offsite at all nuclear power plants. Furthermore, NRC noted in the GEIS that the Resource Conservation and Recovery Act would apply to concentrated subsurface placement of demolition debris, which would limit water quality effects from using rubble and soil as fill material.

During Byron decommissioning, compliance with permits and adherence to erosion and sediment controls, soil stabilization practices, structural practices, and pollution prevention measures would ensure that water quality impacts from decommissioning are small and temporary. Any land-disturbing activities would be of relatively short duration, permitted and overseen by responsible regulatory agencies, and guided by IEPA Erosion and Sediment Control BMPs. Exelon will continue to comply with applicable regulations which require reporting of hazardous material spills. All reasonable precautions will be taken to prevent or mitigate spills of hazardous materials. Exelon will comply with IEPA regulations regarding fill and obtain waste permits as needed. The IEPA encourages reuse and recycling of clean demolition debris and when carried out in accordance with IEPA requirements, would not adversely affect the groundwater quality in the area. In the license renewal SEIS (Reference 13), the NRC concluded that Byron has not impacted and is not reasonably expected to impact the quality of groundwater in any aquifers that are a current or potential future source of water for offsite users. Groundwater movement in the Byron vicinity is generally toward the Rock River. If any localized alteration in the groundwater chemistry associated with the use of crushed concrete as clean fill were to occur, it is unlikely to impact the quality of groundwater in any aquifers that are a current or potential future source of water for offsite users.

Demolition of Byron structures and buildings and related earth-moving work has at least a limited potential to result in erosion and sedimentation that could affect water quality, but these kinds of construction activities routinely take place around operating nuclear power plants and are subject to the provisions of state-issued permits. Current plans call for removal of the river screen house and the sediment management structures within the Rock River. BMPs would be employed to limit erosion while the shoreline structures are being demolished/removed.

Dredging and demolition associated with the removal of the Iowa vanes and wing dams would result in increased turbidity, but the effects would be localized and of limited duration. A Clean Water Act (CWA) Section 404 permit would be obtained as needed for activities within the Rock River and Exelon would comply with any permit conditions imposed by the U.S. Army Corps of Engineers and cooperating state agencies.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report In Section 4.3.3 in the GEIS, NRC concluded generically that for all facilities, decommissioning impacts to surface and groundwater quality would be small. Because there is nothing about Byron's design, location, configuration, operating history, or decommissioning plans that would alter or contradict this generic conclusion and Exelon would comply with regulatory and permit requirements to protect surface water and groundwater resources, Exelon concludes that decommissioning water quality impacts would be small and bounded by the Decommissioning GEIS.

5.1.4 Air Quality The GEIS identified decommissioning activities that may affect air quality, including worker transportation to and from the site, dismantling of systems and removal of equipment, movement, and open storage of material onsite, demolition of buildings and structures, shipment of material and debris to offsite locations, and operation of concrete batch plants. NRC considered the potential for adverse impacts from these activities, the greatest of which would be fugitive dust, for the range of decommissioning plants and generically determined air quality impacts to be small.

IEPA permits and regulates air emissions under Title 35 of the Illinois Administrative Code (IAC)

Parts 201 and 212. Construction and demolition equipment including portable engines and portable concrete crushers would be subject to IEPA air emission unit regulations and permitting requirements. During Byron decommissioning, reasonable and appropriate control measures such as wetting of soil piles, covering loads, and staging areas, and seeding of bare areas would be implemented to control fugitive dust so that emissions do not extend offsite in compliance with IEPA regulations (35 IAC 212.301 ). Permits governing air emissions from the decommissioning activities and equipment would be obtained as required, and as needed, Exelon will maintain existing air permits for equipment that will continue to be used during Byron decommissioning. The exhaust from commuting and shipping vehicles could affect air quality somewhat, but it is unlikely that air quality would be degraded sufficiently to be noticeable beyond the immediate vicinity of German Church Road.

Demolition of Byron's cooling towers would involve the use of explosives. The GEIS considered the use of explosives and stated in Section 0.1.3 that control measures would be implemented during demolition to keep releases, including those associated with fugitive dust, within regulatory limits regardless of the methods used during demolition. The use of explosives will take place under the control of licensed personnel as required by the Illinois Explosives Act (225 ILCS 210). The necessary explosive use requirements and demolition industry BMPs would be implemented.

In Section 4.3.4 in the GEIS, NRC concluded that the impacts of decommissioning on air quality would be neither detectable nor destabilizing and that current and commonly used mitigation measures should be sufficient. Because (1) the air quality impacts from decommissioning activities at Byron are expected to be temporary and localized, (2) reasonable and appropriate control measures would be employed, and (3) the appropriate permits would be obtained, and (4) there is nothing about Byron's location or decommissioning plans that would alter or contradict the generic conclusion in Section 4.3.4 of the GEIS, Exelon concludes that air quality impacts from Byron decommissioning activities are bounded by the analysis.in the GEIS.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report 5.1.5 Aquatic Ecology Aquatic communities may be directly or indirectly impacted by decommissioning activities.

Direct impacts are possible from shoreline or in-water construction or from dredging. Indirect impacts may result from construction-related erosion and stormwater runoff. These impacts are typically undetectable (or barely discernible) and do not destabilize any important attributes of the resources. The GEIS determined that such decommissioning activities within the operational areas of nuclear power plants, including removal of shoreline or in-water structures, would have only minor impacts on aquatic communities, provided all appropriate BMPs are employed.

Therefore, the GEIS concluded generically that aquatic impacts from decommissioning activities within a defined operational area would be small. However, the GEIS noted that if disturbance beyond the operational area is anticipated, potential impacts must be determined through site-specific analysis.

Exelon intends to remove the Iowa vanes and riprap wing dams that were installed in the Rock River in 1993 to prevent sedimentation at Byron's river screen house. Removal of the Iowa vanes and wing dams would require authorization from the USACE, the Illinois Department of Natural Resources (IDNR) Office of Water Resources, and the IEPA. Benthic macroinvertebrates and fish immediately downstream of the construction zone would be exposed to elevated levels of dissolved/suspended solids and increased turbidity during the construction phase. Fish normally move away from areas with high silt/sediment loads, so are affected only to the extent that they lose access to potential foraging and spawning habitats.

Benthic communities are more likely to be affected, but typically recover once construction ceases and water quality conditions return to normal.

The Byron rail spur includes a railroad bridge that crosses the Rock River a short distance upstream of the State Route 72 highway bridge. It may be necessary to repair parts of the bridge as well as the rail spur. Assuming mitigation measures recommended (or required) by state and federal permitting agencies are employed, impacts to aquatic communities from bridge repair are expected to be localized and temporary.

Another activity with potential for impacting aquatic communities is removal of the river screen house during the site restoration phase, after license termination. Strict adherence to soil and erosion control measures and pollution (spill) prevention measures prescribed by the IEPA should limit impacts to water quality impacts due to structure and building removal, thus limit indirect impacts (sedimentation) to aquatic communities. The FES (Reference 11) considered the impacts of site preparation and construction on the water quality and aquatic biota of the Rock River. Construction of the river screen house/makeup water intake and blowdown was the primary concern because construction of the generating facilities and supporting infrastructure was to take place more than 2 miles from the river. The FES acknowledged that streamside construction could produce temporary increases of particulate matter (sediment) in the river but that judicious use of sediment and erosion controls would "protect the aquatic biota." Impacts associated with the removal of the river screen house are expected to be similar and bounded by those experienced during the initial construction.

Given that (1) direct impacts from river screen house removal on benthic macroinvertebrates and fish are expected to be minor and temporary, (2) impacts from sediment management system removal and a possible bridge repair are expected to be temporary and less than Page 26 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report significant, and (3) no federally listed aquatic species has been recorded in the project area, Exelon concludes that the Decommissioning GEIS's generic conclusions relative to aquatic communities apply, and impacts are expected to be small.

5.1.6 Terrestrial Ecology Section 4.3.6 of the Decommissioning GEIS maintains that "(f)or facilities where habitat disturbance is limited to operational areas, the impacts on terrestrial ecology (i.e., plant and animal communities) are not detectable or destabilizing." NRC staff concluded that, "for such facilities... potential impacts to terrestrial ecology are small" and no further mitigation measures are warranted. Site-specific analysis is only required of licensees when decommissioning activities are likely to occur outside of the operational area.

Byron's decommissioning plans call for backfilling demolished building and structure foundations. Fill will be sourced from onsite demolition activities in compliance with IEPA fill regulations. If additional fill is needed, Exelon could obtain it from onsite (within the operational area), with preference given to previously disturbed areas with low quality soils. Exelon would avoid disturbing native vegetation, wetlands, or other high-value habitats for additional fill sourced from onsite.

The Decommissioning GEIS did not generically bound impacts to terrestrial species for decommissioning activities conducted outside the operational area. As discussed in previous sections, Exelon has identified two decommissioning activities (rail spur repair and sediment management system removal) that may take place outside of the operational area and has conducted site-specific evaluations for these activities.

The repair of the railway is not expected to disturb land outside of the rail spur's corridor; however, repair of the bridge could require temporary use of additional land for staging of materials and equipment. These temporary staging and laydown areas near the rail bridge could require some land clearing, but would be sited to avoid sensitive environmental features such as wetlands. Because no high-value terrestrial habitats will be disturbed by the repairs to the rail spur, impacts to terrestrial species are expected to be small and should not require mitigation, beyond avoiding important or sensitive habitats. Some activities associated with the removal of the sediment management system in the Rock River, such as establishing temporary work and equipment storage areas on both sides of the river, are expected to take place outside the operational area. These temporary staging areas would be sited to avoid sensitive environmental features and restored when the work is completed. Because no high-value terrestrial habitats will be disturbed and regulations protecting wetlands would be followed, if applicable, impacts to terrestrial species are expected to be small and should not require mitigation.

Because no sensitive resources (e.g., high-value wildlife habitat, rare or protected species) will be disturbed inside the operational area, Exelon concludes that decommissioning impacts at Byron would be small and should not require mitigation, beyond routine construction BMPs.

Impacts to terrestrial resources from sediment management system removal and a potential repair of the rail spur and bridge outside of the operational area are also expected to be small because no high-value terrestrial habitats or protected species will be disturbed and state and federal regulations for protection of wetlands will be followed, if applicable. Impacts from both Page 27 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report activities would be similar to those experienced during construction of the station and considered in the FES. Having established that there is nothing unique about Byron's design, operation, or location and having determined that impacts of Byron decommissioning on terrestrial resources would be similar to those described in previous NRG impact assessments, Exelon concludes that impacts of Byron decommissioning on terrestrial resources would be small, similar to those described in the FES, and bounded by the Decommissioning GEIS.

5.1. 7 Threatened and Endangered Species The GEIS lists stabilization, large component removal, decontamination, and dismantlement (removal of contaminated soil), and structure dismantlement as activities with potential to impact threatened and endangered species. The GEIS did not make a generic determination on the impact of decommissioning on threatened and endangered species, but noted that impacts to these species are expected to be minor and non-detectable when activities are confined to the site operational area. Impacts are to be determined on a site-specific basis, paying particular attention to activities outside of the developed operational area. Noise and dust generation from construction activity and increased truck traffic, rather than direct impacts such as habitat destruction, are the primary concerns.

Exelon compiled the following list of state and federally listed species that could occur in the vicinity of Byron based on a review of pertinent ecological studies, long-term monitoring studies conducted by Commonwealth Edison and Exelon, NRG National Environmental Policy Act documents related to Byron operations, and queries of state (EcoCAT) and federal (IPaC) databases.

Table 5.1:

Protected Species Potentially Occurring in Byron Vicinity Through 2020 Scientific Name Common Name Federal Status State Status Mammals I

Myotis soda/is Indiana bat E

E Myotis septentrionalis Northern long-eared bat T

T Birds I

Haliaeetus leucocephalus*

Bald eagle NL NL Sterna hirundo Common tern NL E

Plants I

Ceanothus herbaceus Red root NL E

Dalea foliosa Leafy prairie clover E

E Lespedeza /eptostachya Prairie bush clover T

E Platanthera leucophaea E. prairie fringed orchid T

E NL= not listed; E = Endangered; T =Threatened

• has full legal protection under Bald and Golden Eagle Act

5. 1. 7. 1 Protected Terrestrial Species Decommissioning activities with greatest potential for directly and indirectly affecting terrestrial Page 28 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report plant and animal communities are those scheduled for late phases when major reactor structures are to be demolished and the two Byron natural draft cooling towers are to be taken down using explosives. Excluding the sediment management system removal and rail spur/bridge refurbishment discussed in previous sections, all decommissioning activities will be confined to the operational area, which does contain some large patches of woods and some small stream drainages, but these habitats are for the most part adjacent to roads and facilities, thus exposed to a fairly constant level of noise and human activity.

Demolition of Byron power block structures and cooling towers will disturb wildlife, but common rather than rare or protected species. Demolition of buildings and structures will likely involve large cranes, excavators, pneumatic drills, concrete and rebar saws and other extremely noisy equipment. These demolition and dismantlement activities are likely to take weeks or months.

All of the activities expected to generate high noise levels will take place in areas well removed from the highest-quality wildlife habitat on the site, which are the grasslands, wetlands, and forests in the pipeline corridor. The intake and discharge pipelines themselves will be abandoned in place, so their removal is not a concern.

All decommissioning activities at Byron (with the exception of the sediment management system and rail spur/bridge refurbishment) will take place within the site operational area; therefore, impacts to terrestrial ecological resources, including threatened and endangered species, are expected to be small. Land disturbance of greater than one acre would require an individual or general construction stormwater NPDES permit. NPDES permit applicants are required to provide proof of consultation with IDNR regarding the presence of federal or state threatened or endangered species and, if applicable, measures to avoid or mitigate impacts to protected species and their habitat. State and federal resource agency staff will be consulted at the appropriate time to rule out the presence of previously undiscovered/unreported threatened or endangered species and, if present, to ascertain if any mitigation measures are warranted.

5. 1. 7. 2 Protected Aquatic Species No aquatic species listed by the United States Fish and Wildlife Service (USFWS) (or proposed for listing by the USFWS) has been observed or collected in the reach of the Rock River adjacent to the Byron site and there is no protected or critical habitat present. However, the presence of state-listed mussels cannot be ruled out, based on historical surveys. As discussed previously in the Aquatic Ecology section (Section 5.1.5), removal of the Iowa vanes and wing dams (and refurbishment of the railroad bridge, if necessary) would require authorization from USACE, the IDNR Office of Water Resources, and IEPA [i.e., a CWA 404/Section 10 of the Rivers and Harbors Act of 1899 permit and a CWA Section 401 certification]. Any concerns IDNR may have with regard to rare aquatic biota, such as state-listed mussels, will be considered at the time of the project review and be addressed, as appropriate, in permit conditions. Any project funded or authorized by a federal agency that may affect threatened or endangered species must be reviewed by the USFWS for possible impacts, in accordance with the Endangered Species Act. Based on currently available information, no federally listed species will be affected by the sediment management system removal or bridge refurbishment.

Nevertheless, USACE may choose to consult informally with the USFWS Ecological Services Field Office in Moline, Illinois, to ensure that any USFWS concerns are considered.

Further, state, and federal resource agencies will be consulted before major decommissioning activities commence to ensure that no listed aquatic species has been discovered in the intervening years and that no species previously documented in the Rock River has, in the intervening years, been afforded state or federal protection.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report

5. 1. 7. 3 Conclusion NRC has determined that potential impacts of decommissioning on threatened and endangered species must be evaluated on a site-specific basis. Exelon has determined that none of the planned decommissioning activities at Byron would disturb the natural habitat of any state or federally listed terrestrial species. Any indirect (disturbance-related) impacts from construction noise and human activity would be localized, of short duration, and ecologically insignificant.

Birds and mammals that are intolerant of noise and human activity, including protected species, are expected to simply avoid (or move away from) noisy construction sites.

With regard to the sediment management system removal and rail spur/bridge refurbishment discussed previously, agency permitting requirements and the mitigation measures discussed in previous sections should minimize impacts to protected aquatic species, if any are present. It may be necessary to first determine whether protected mussels survive in the Rock River in the vicinity of the proposed in-stream construction sites to determine if in-water and underwater construction will impact them. It may also be necessary to determine if rare mussels still occur adjacent to and immediately downstream of the intake, where cofferdams will be placed, and the river bottom will be disturbed. If special-status mussels are present, Exelon is prepared to take steps necessary to prevent harm to these populations, including collecting at-risk mussels in demolition and construction zones and moving them to suitable locations elsewhere in the Rock River chosen by the appropriate agency staff.

Based on the site-specific findings summarized in this section, Exelon concludes that Byron decommissioning activities are unlikely to adversely affect any threatened or endangered species and will have no effect on any designated critical habitat. However, in the future, when Byron decommissioning activities, such as demolition or disturbance of land areas that could affect a protected species have been finally determined and scheduled, Exelon will update the site-specific assessment of environmental impacts to protected species in the PSDAR. To comply with its continuing obligation under 10 CFR 50.82(a)(6) to assure that no decommissioning activity that would result in significant environmental impacts would be performed without NRC review, the results of the assessment would be provided to the NRC in accordance with applicable NRC regulations.

5.1.8 Radiological The GEIS considered radiological doses to workers and members of the public when evaluating the potential consequences of decommissioning activities and concludes that radiological impacts of decommissioning activities are small.

5. 1. 8. 1 Occupational Dose One conclusion of the GEIS is that, based on decommissioning experience, occupational dose during decommissioning is comparable to that observed during routine operations at the same or similar facilities. Therefore, Exelon evaluated Byron operational dose data and compared it to that of other PWRs and established that Byron operating collective dose is typical of U.S.

PWRs. Furthermore, Exelon calculated occupational collective dose expected during the decommissioning period using methodology from NUREG/CR-5884, "Revised Analyses of Decommissioning for the Reference Pressurized Water Reactor Power Station" (Reference 8).

The calculated decommissioning collective dose was lower than that reported in NUREG/CR-5884 for the reference PWR. Thus, Byron decommissioning occupational dose is expected to Page 30 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report be within or below the range of doses presented in the GEIS. There are no unique characteristics at Byron that would invalidate this conclusion.

Exelon selected a SAFSTOR decommissioning strategy, ensuring that most exposure scenarios will result in lower occupational doses than those during operations due to the fact that the plant has been defueled and a period of radioactive decay has reduced the radiological inventory.

The Byron As Low as Reasonably Achievable (or ALARA) program and regulatory limits on dose will remain in effect during decommissioning.

5. 1. 8. 2 Public Dose Section 4.3.8 in the GEIS states that radionuclide emissions in gaseous and liquid effluents are reduced in facilities undergoing decommissioning. Given that Byron public doses during operations were well within the NRC-established public dose limits, it is reasonable to expect that public doses during decommissioning would also be well within such limits. Annual reports of environmental monitoring at Byron for the years from 2015 through 2019 demonstrate that operation of Byron had no adverse radiological impact on the environment. Controls on potential radiological releases will continue to be applied during decommissioning.

5. 1. 8. 3 Conclusion Exelon concludes that radiological impacts of Byron decommissioning are small for the following reasons:

The GEIS generic evaluation of radiological impacts applies to a typical PWR. Both occupational dose and public dose from normal Byron operations are similar to those of other PWR plants, suggesting that Byron doses are typical.

The Byron collective worker dose estimate for the decommissioning periods is lower than that predicted by NUREG/CR-5884.

Exelon's selection of the SAFSTOR decommissioning option allows for radionuclides to decay over time, resulting in less dose at the time of decommissioning.

Current decommissioning plans fall within decontamination, dismantlement, and waste processing activities considered by NRC, and site-specific conditions do not represent unique conditions that would lead to a conclusion different than that reached in the Decommissioning GEIS.

Therefore, Exelon further concludes that the radiological impacts of Byron decommissioning are bounded by the analysis in the GEIS.

5.1.9 Radiological Accidents Section 4.3.9 in the GEIS examined a range of radiological accidents hypothetically possible during the decommissioning period. These included external events, non-nuclear fuel-related accidents, and nuclear fuel-related accidents. The GEIS concludes that impacts of radiological accidents of all types applicable to decommissioning activities are small.

Given their potential to result in offsite doses, the GEIS considered spent fuel accidents of most concern for decommissioning. Once in dry cask storage, however, spent fuel management is no longer within the scope of decommissioning environmental review because NRC evaluated the Page 31 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report environmental impacts of continued spent fuel storage for all nuclear power plants in NUREG-2157, "Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel" (Reference 14). Consequently, the only accidents of importance to offsite doses during decommissioning are those involving spent fuel in the spent fuel pool. Spent fuel pool accidents would no longer be applicable after the spent fuel is moved to dry cask storage. The most significant of the spent fuel accidents, in terms of consequences and probability, involves spent fuel pool drainage leading to a zirconium fire. However, NRC, in both NUREG-2157 and the GEIS, determined that the risk of a zirconium fire is very low (but, should it occur, the consequences could be high).

Spent fuel at Byron will, at a minimum, remain in the spent fuel pool for as long as is required for cooling before being moved to dry storage. A zirconium fire accident is potentially possible (but very improbable) during a portion of the time that spent fuel is stored in the spent fuel pool. The Updated Final Safety Analysis Report (UFSAR) describes the abnormal operational transients and design basis accident scenarios that are applicable during plant operations. Exelon has concluded that most of the accident scenarios postulated in the UFSAR will no longer apply after Byron is in the permanently defueled condition (Reference 15).

The UFSAR accidents that will remain applicable to Byron in the permanently shutdown and defueled condition are the Fuel Handling Accident in the Fuel Handling Building, gas waste system leak or failure, radioactive liquid waste system leak or failure, postulated radioactive release due to liquid tank failure, and spent fuel cask drop accident. The UFSAR concludes that the site boundary doses associated with a Fuel Handling Accident, gas waste system leak or failure, radioactive liquid waste system leak or failure, and spent fuel cask drop accident during operations would be within the limits specified in 10 CFR 100. The postulated radioactive release due to liquid tank failure accident assumes the liquid enters the groundwater through postulated cracks in the auxiliary building. The consequences of such a release are evaluated in Section 2.4.12 of the UFSAR and the concentration of any postulated accidental release of radioactive effluents would not exceed the limits specified in 10 CFR 20 at the nearest surface water intake. Exelon will respond to events at Byron in the reduced spectrum of credible accidents in the permanently defueled condition and retain the ability to promptly implement the spent fuel pool mitigation actions.

Also, Exelon knows of no unique features or conditions at Byron that would lead to a conclusion concerning radiological accidents different than that reached in the GEIS. Therefore, Exelon concludes that accident impacts of decommissioning activities at Byron are bounded by those in the Decommissioning GEIS, resulting in small impacts.

5.1.10 Occupational Issues Section 4.3.10 of the GEIS concluded that impacts due to occupational issues would be small for all plants based on strict adherence to NRC and Occupational Safety and Health Administration (OSHA) safety standards, practices, and procedures.

Byron decommissioning will be conducted under a comprehensive non-radiological safety and health program meeting OSHA, NRC, and Exelon procedural requirements. Exelon facilities have lower rates of injuries and illness than the national average for electrical utilities, and historically, the nuclear power industry has lower rates of injuries and illnesses than other Page 32 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report industries.

Demolition of the Byron cooling towers would involve the use of explosives. NRC considered the use of explosives during decommissioning and specifically mentioned the hazards of fugitive dust and noise levels from blasting in Sections 0.1.3 and 0.1.14 of the GEIS. The use of explosives will take place under the control of licensed personnel as required by the Illinois Explosive Act (225 ILCS 210). OSHA regulations for worker protection would also ensure that the appropriate worker protection programs such as a respiratory protection plan and hearing protection plan are in place.

The Byron site-specific decommissioning activities and methods for carrying out the activities are within the range of those evaluated in the GEIS. Accordingly, Exelon concludes that anticipated impacts resulting from non-radiological occupational issues during Byron decommissioning are small and thus bounded by the analysis in the GEIS.

5.1.11 Cost A site-specific decommissioning cost estimate is summarized in Section 4.0.

5.1.12 Socioeconomics The GEIS evaluated changes in workforce and population, changes in local tax revenues, and changes in public services for decommissioning. The NRC considered the decreases in workforce and tax payments related to the cessation of operations (plant closure) outside the scope of decommissioning. The GEIS concluded that socioeconomic impacts caused by decommissioning are neither detectable nor destabilizing and that mitigation measures are not warranted.

As Byron ceases operation and transitions through the phases of decommissioning, an overall decrease in plant workforce and tax payments will occur, primarily impacting Lee, Ogle, and Winnebago Counties, where the majority (82 percent) of the permanent plant workforce resides and Ogle County whose taxing districts receive Byron property tax payments. The initial workforce reduction and the reduction in Byron's fair market value and a corresponding reduction in tax liability would be attributable to plant closure. The station workforce reduction attributable to decommissioning with the greatest impact on population would result in an approximately 0.6 percent decrease in Ogle County's population and smaller decreases in each of Lee and Winnebago Counties' populations. Changes in tax liabilities attributable to decommissioning would be minimal.

Based on the findings summarized above, Exelon concludes that impacts to socioeconomic resources attributable to Byron decommissioning would be small and thus bounded by the analysis in the GEIS.

5.1.13 Environmental Justice Section 4.3.13 of the GEIS determined environmental justice to be an environmental impact area for which no generic conclusion could be determined due to its site-specific nature.

Therefore, the GEIS indicates that site-specific assessments for each decommissioning nuclear power plant must be prepared.

Page 33 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Exelon prepared a site-specific assessment of environmental justice as it relates to the effects of Byron decommissioning. Exelon examined the geographic distribution of minority and low-income populations within a 50-mile radius of the Byron site using the 2014-2018 American Community Survey 5-year estimates. Census block groups containing minority populations were identified and are concentrated in the larger metropolitan areas of Rockford (Winnebago County), Janesville and Beloit (Rock County), and DeKalb (DeKalb County). The nearest minority population blocks are located south of the city of Rockford, about 10-15 miles northeast of Byron. Census block groups containing low-income populations are concentrated in the cities of Rockford, Janesville, Beloit, and DeKalb. The nearest low-income populations are located south of the city of Rockford, about 10-15 miles northeast of Byron.

Exelon determined that decommissioning impacts to all resource areas would be small, indicating that the effects are not detectable or are so minor that they will neither destabilize nor noticeably alter any important attribute of the resource. Because no member of the public will be substantially affected, there can be no disproportionately high and adverse impact or effects on minority and low-income populations resulting from the decommissioning of Byron. Based on these site-specific findings, Exelon concludes that the impacts of decommissioning Byron on minority and low-income populations are small. Even so, after decommissioning plans mature and before decommissioning activities occur that could be potentially impactful to minority and low-income populations or would be otherwise inconsistent with those actions or activities described in the PSDAR, Exelon would notify the NRC in writing and seek appropriate environmental review in accordance with applicable NRC regulations.

5.1.14 Cultural, Historical, and Archaeological Resources Section 4.3.14 of the GEIS determined that potential effects of decommissioning on cultural, historical, and archaeological resources would be small for all plants when the decommissioning activities are confined to the operational area. However, impacts outside the operational area "must be determined through site-specific analysis." Exelon anticipates that decommissioning activities will take place within the Byron operational area, with the exceptions of the possible rehabilitation and use of the railroad spur between Byron Station and City of Byron and removal of the sediment management system in the Rock River in the vicinity of the river screen house.

Exelon conducted a review of available information about cultural, historical, and archaeological resources for Byron and within an approximately 6-mile radius, including data from the Illinois State Historic Preservation Office (IL-SHPO), the Illinois Archaeological Survey, and the National Park Service (NPS).

Currently, five archaeological sites have been recorded within the Byron operational area, all of which represent prehistoric Native American localities. All sites are situated in the western part of the operational area. Sites 11OG155, 110G156, 11OG157, and 110G158 are small, undated plowzone scatters of lithic artifacts situated in the intake/discharge pipeline right-of-way (ROW) section of the operational area east of N. River Road. Site 11OG153, Archaic and Late Woodland period habitation site with sub-plowzone deposits, is also situated in the ROW section of the operational area but is on the western side of N. River Road closer to the Rock River than Sites 11OG155 through 11OG158a. According to the Illinois Inventory of a There is conflicting information about the precise locations of the archaeological sites. The descriptions provided here are based on the original reporting of the pre-construction archaeological investigations at Byron in 1973 and 1974.

Page 34 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Archaeological Sites (llAS), Sites 11OG155 through 11OG158, are categorized as not eligible for the National Register of Historic Places (NRHP). In the llAS, Site 110G153 is categorized as "Phase II Completed," but without an explicit determination of eligibility or non-eligibility to the NRHP.

Nine properties within 6 miles of Byron are currently listed on the NRHP, and three additional properties within the 6-mile radius have been formally identified as NRHP-eligible. The NRHP-listed properties include one historic district, five buildings (three public, one commercial, and one private dwelling), and three memorial-type landscape features. The NRHP-eligible properties include two dwellings and an archaeological site. None of the properties is located within the operational area, and the nearest is approximately 2.4 miles distant from it. Byron was constructed in the late 1970s and early 1980s, and its reactors began commercial power production in 1985 and 1987. The station is therefore less than 50 years old so has not crossed the age threshold for assessment of potential eligibility to the NRHP.

Decommissioning activities within the operational area are anticipated to occur in areas of prior ground disturbance and will not affect historic, cultural, or archaeological resources now listed on or eligible for listing on the NRHP. Use of explosives for demolition of the natural draft cooling towers will be in accordance with BMPs and will seek to minimize the generation of fugitive dust, avoiding possible adverse effects to historic properties. Vibrations associated with the explosions and controlled collapse of the towers are not expected to adversely affect currently identified historic properties.

Decommissioning activities outside the operational area would potentially be related to the rail spur and the sediment management system in the Rock River. The rail spur potentially would be repaired and then used for radiological waste shipments to support decommissioning. Repair of the rail spur would be expected to be conducted within the rail corridor and thus limited to areas of previous ground disturbance. If land is needed for temporary staging of equipment for bridge repairs and would require new land disturbance, any necessary evaluations for cultural resources would be undertaken prior to disturbance. Further, the rail spur itself could also be considered for historic significance due to its age at the time of decommissioning activities.

Exelon would comply with cultural resource regulations and statutes in existence at the time with regard to assessing or documenting the rail spur structures prior to major repair activities which could affect their historic integrity. Similarly, some activities connected with the removal of the sediment management system in the Rock River by the river screen house are expected to take place outside the operational area. The removal of the sediment management system would take place largely within areas previously disturbed by construction of the system and undisturbed areas required for disassembly of the system, would undergo any necessary evaluations for cultural resources prior to disturbance.

In sum, Exelon concludes that impacts on cultural, historical, and archaeological resources by decommissioning Byron, both within the operational area and outside it, are small and thus bounded by the Decommissioning GEIS.

5.1.15 Aesthetic Issues In Section 4.3.15 of the GEIS, the NRC singles out structure dismantlement and entombment as the only activities that may have impacts on aesthetic resources. The aesthetic impacts of Page 35 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report decommissioning fall into two categories: (a) impacts, such as noise, associated with decommissioning activities that are temporary and cease when decommissioning is complete and (b) the changed appearance of the site when decommissioning is complete. NRC drew the generic conclusion that for all plants, the potential impacts from decommissioning on aesthetics are small and that the removal of structures is generally considered beneficial to the aesthetics of the site.

During Byron decommissioning, the impact of noise and dust would be temporary and controlled to minimize impacts. The appearance of Byron will be altered as the buildings and structures are dismantled. There are clear views of the plant from the from the surrounding area. The visual intrusion during dismantlement would be temporary and would serve to reduce the aesthetic impact of the site. The changed appearance of the site when decommissioning is complete would generally be considered beneficial to the aesthetics of the site. Therefore, Exelon concludes that the impacts of Byron decommissioning on aesthetics are small and generally considered beneficial. Thus, such impacts are bounded by the analysis in the GEIS.

5.1.16 Noise Section 4.3.16 of the GEIS generically examined noise during decommissioning, concluding that noise impacts would be small.

Decommissioning activities will be primarily limited to previously disturbed land surrounding the power block and potentially along the rail spur if it is used for waste shipment. Activities would also along take place for a limited duration at the Rock River for removal of structures. The noise levels associated with these activities are not expected to be any more severe than during the initial construction of the station or refueling outages and are not expected to present an audible intrusion on the surrounding community and environment. The noise sources surrounding Byron include agricultural activities, local traffic on rural roads, etc. The closest residences are more than 0.6 mile from primary noise sources at Byron. Activities at Byron would have to follow applicable federal, state, or local guidelines and regulations on noise.

Illinois has a noise regulation with allowable octave band sound levels according to emitting and receiving land-use classification and time of day (Illinois Administrative Code (IAC), Title 35:

Environmental Protection, Subtitle H: Noise). Ogle County has ordinances with nuisance clauses (Ordinance 8-6-1994) against noise but has established no quantitative noise limits.

NRC also considered the higher noise levels of demolition methods including use of pneumatic drills or explosives and concluded that environmental effects may be minimized by proper scheduling due to the short duration and isolated use of such methods. The consideration of these higher noise activities in Section 0.1.4 of the GEIS did not alter NRC's conclusion that it is unlikely that the noise associated with most decommissioning activities will be of sufficient strength to be environmentally detectable or to destabilize the environment.

Decommissioning activities will take place within the area surrounding the power block, at the Rock River near the intake, and potentially along the rail spur. The noise levels associated with the decommissioning activities are not expected to be any more severe than during the initial construction of the station or refueling outages and are not expected to present an audible intrusion on the surrounding community and environment. Higher noise levels may occur during the demolition of the cooling towers, but that activity will be limited in duration.

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report Therefore, because Byron decommissioning activities are of the type previously considered by NRC and Byron has no site-specific conditions that would alter the NRC's prior findings, Exelon concludes that the noise impacts from decommissioning activities would be small and thus bounded by the analysis in the GEIS.

5.1.17 Transportation In Section 4.3.17 of the GEIS, NRC states that its "... regulations are adequate to protect the public against unreasonable risk from the transportation of radioactive materials." Therefore, the effects of transportation of radioactive waste on public health and safety are considered to be neither detectable nor destabilizing. Exelon will comply with NRC and Department of Transportation regulations for shipments of radioactive waste from Byron decommissioning.

The GEIS analyzes radiological shipments of waste from decommissioning and calculates incident-free doses and latent cancer fatalities to crew, the public along the route, and onlookers. The GEIS also calculates the collective dose for radiological accidents during transportation. The calculated impacts are closely related to the distance shipped, volumes shipped, and activity levels. The estimated volumes of radioactive waste associated with Byron decommissioning are summarized in the Table 5.2 using waste types from the GEIS and waste volumes from the Byron decommissioning cost estimate. The volumes presented in Table 5.2 are on a single unit basis using the higher of the estimates for Byron Unit 1 or Unit 2. This allows for comparison with the NRC's analysis in the GEIS for decommissioning of single reactor sites based on past decommissioning experience.

Table 5.2:

Estimated Radioactive Waste Associated with Byron Decommissioning Waste Type High-activity waste Class Band C Class A Low-activity waste (Class A)

Very low-activity waste (Class A)

Volume (ft3)

Per Unit 2,867 39,373 13,358 168,824 Exelon considered a bounding scenario in which the Class A wastes are shipped to the EnergySolutions, Inc. disposal site in Utah and Class Band C wastes are shipped to the Waste Control Specialists, LLC facility in Texas. All wastes were assumed to be shipped via truck.

Transportation impacts would be reduced to the extent waste is shipped to the disposal site via rail.

For the following reasons, if radiological impacts alone are considered, the conclusions in the GEIS would bound the impacts of transportation of radioactive waste from Byron decommissioning. For Byron, the volumes estimated per unit for high-activity waste and low-activity waste are less than the waste volumes that NRC assumed in the Decommissioning GEIS. Other considerations would greatly reduce worker and population exposure. The Byron Page 37 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report rail spur could be refurbished and used for radioactive waste shipments. The NRC indicates in the GEIS that use of rail reduces radiological impacts by more than a factor of 10 over truck shipments. In addition, the distances traveled to disposal sites available to Byron are significantly lower (less than half) than were analyzed in the Decommissioning GEIS. In the GEIS evaluation, the low-activity waste shipments were assumed to exhibit lower external dose rates (i.e., one-tenth of regulatory limits) and for very low-activity waste are sufficiently small that the activity may be neglected in evaluating the radiological impacts of transportation. Very low-activity waste is expected to comprise 75 percent of the overall Byron waste volume and would have negligible radiological impacts.

Section 4.3.17 of the GEIS recognizes non-radiological impacts of transportation to include increased traffic, wear and tear on area roadways, and increased traffic accidents from both radiological and non-radiological transport, including that for hazardous waste. NRC concluded that transporting materials to and from a decommissioning site would not significantly impact the overall traffic volume or compromise the safety of the public. Byron's waste shipments are not expected to be large enough in number to have a detectable or destabilizing effect on traffic flow or road wear. The number of workers during the decommissioning phases is expected to be considerably less than the current onsite workforce and well below the temporary workers during refueling outages. Consequently, challenges to the existing transportation infrastructure are not expected.

The GEIS concludes that both non-radiological and radiological impacts of decommissioning transportation are small. No unique features or site-specific conditions are present at Byron that would alter these NRC prior findings. Therefore, Exelon concludes that transportation impacts of Byron decommissioning would be small and thus bounded by the analysis in the GEIS.

5.1.18 Irreversible and Irretrievable Commitment of Resources Section 4.3.18 of the GEIS generically concluded that the impacts of decommissioning on irreversible and irretrievable commitments of resources are small. Given that Byron would be decommissioned to radiological standards for unrestricted release, the land will be available for other uses. Furthermore, the materials and fuel consumed during Byron decommissioning would be minor. The decommissioning of Byron would generate radioactive waste and non-radiological waste requiring land disposal. Land devoted to radioactive waste disposal sites or industrial landfills was not within the scope of the GEIS because such commitments are addressed in the licensing documents for the disposal sites. Therefore, Exelon concludes that the impacts of Byron decommissioning on irreversible and irretrievable commitments of resources would be small and thus bounded by the analysis in the GEIS.

5.2 ENVIRONMENTAL IMPACTS OF LICENSE TERMINATION - NUREG-1496 According to the schedule provided in Section 3 of this report, a L TP for Byron will be developed and submitted to NRC approximately two years prior to the anticipated license termination date.

The L TP will include a supplement to the Byron PSDAR Environmental Report describing any new information or significant environmental change associated with the proposed termination activities. Although the L TP, including a supplement to the Environmental Report, need not be prepared and submitted until a minimum of two years prior to the anticipated license termination date, as required by 10 CFR 50.82(a)(9), the absence of any unique site-specific factors, significant groundwater contamination, unusual demographics, or impediments to achieving Page 38 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report unrestricted release indicate that impacts resulting from Byron license termination will be similar to those evaluated in NUREG-1496 (Reference 10).

5.3 DISCUSSION OF DECOMMISSIONING IN THE SEIS Decommissioning was addressed in Sections 2.1.3 and 4.15.2 of the SEIS for Byron license renewal (Reference 13). The NRC did not identify any new and significant information during their review and, therefore, NRC concluded that there would be no impacts beyond those discussed in the 2013 GEIS for License Renewal of Nuclear Plants, NUREG-1437, Revision 1 (Reference 12). For all of the Category 1 issues applicable to decommissioning, NRC concluded that the impacts would be small. There are no contemplated decommissioning activities that would alter that conclusion.

5.4 ADDITIONAL CONSIDERATIONS The following considerations are relevant to concluding that Byron decommissioning activities prior to license termination will not result in significant environmental impacts not previously reviewed:

Continued compliance with radiological release and dose regulatory limits and adherence to plant procedures for monitoring and controlling releases and the Offsite Dose Calculation Manual Continued site access control to minimize or eliminate radiation release pathways to the public Transport of radioactive waste in accordance with plant procedures, applicable federal regulations, and the requirements of the receiving facility Continuation of the Radiological Environmental Monitoring Program until no longer necessary, and continuation of the radiological groundwater protection program as needed Continued adherence to ALARA principles during decommissioning and compliance with occupational dose limits Continued compliance with applicable regulations and permit conditions Continued storage of spent fuel in accordance with license and plant procedures

5.5 CONCLUSION

S Exelon evaluated the site-specific impacts anticipated from decommissioning of Byron for each environmental resource area in the same manner and context as used by NRC in its GEIS. This evaluation indicates that Byron decommissioning activities fall within the range of decommissioning activities considered by NRC in the GEIS. There are no unique aspects of the plant or the expected decommissioning techniques that would invalidate the applicability to Byron of the GEIS conclusions. The evaluation indicates that the impacts of Byron decommissioning are bounded by the GEIS' assessment for those environmental issues for which NRC made generic determinations. For the areas where a site-specific assessment was required, the anticipated impacts from Byron decommissioning were determined to be small. In addition, after decommissioning plans mature and before decommissioning activities occur that Page 39 of 42

Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report could be potentially impactful to the environmental resource or would be otherwise inconsistent with those actions or activities described in the PSDAR, Exelon will notify the NRC in writing and seek appropriate environmental review in accordance with applicable NRC regulations.

Page 40 of 42

6 REFERENCES Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report

1. Regulatory Guide 1.185, "Standard Format and Content for Post-Shutdown Decommissioning Activities Report," Revision 1, dated June 2013 (ADAMS Accession No. ML13140A038)

2. Letter from J. Bradley Fewell (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Certification of Permanent Cessation of Power Operations for Byron Station, Units 1 and 2," dated September 2, 2020 (ADAMS Accession No. ML20246G613)

3. U.S. Nuclear Regulatory Commission, NUREG-0586, Supplement 1, "Generic Environmental Impact Statement on Decommissioning of Nuclear Facilities, Regarding the Decommissioning of Nuclear Power Reactors" November 2002 (ADAMS Accession Nos. ML023470304 (Vol 1) and ML023470323 (Vol 2))

4. Nuclear Energy Institute (NEI) Technical Report 07-07, "Industry Groundwater Protection Initiative - Final Guidance Document," August 2007

5. Atomic Industrial Forum, AIF/NESP-036, "A Guideline for Producing Commercial Nuclear Power Plant Decommissioning Cost Estimates," May 1986

6. Letter from Patrick Simpson, (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission - "Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations," dated February 24, 2021 (ADAMS Accession No. ML21055A776)

7. U.S. Nuclear Regulatory Commission, Regulatory Guide 1.159, "Assuring the Availability of Funds for Decommissioning Nuclear Reactors," Revision 2, dated October 2011 (ADAMS Accession No. ML112160012)

8. U.S. Nuclear Regulatory Commission, NUREG/CR-5884, PNL-8742, "Revised Analyses of Decommissioning for the Reference Pressurized Water Reactor Power Station" dated.

November 1995. ML14008A187.

9. Environmental Report, Post-Shutdown Decommissioning Activities Report, Byron Station Units 1 & 2, dated April 30, 2021

10. U.S. Nuclear Regulatory Commission, NUREG-1496, "Generic Environmental Impact Statement in Support of Rulemaking on Radiological Criteria for License Termination of NRG-Licensed Nuclear Facilities," July 1997 (ADAMS Accession No. ML042310492) 11. U.S. Atomic Energy Commission. 1974. Final Environmental Statement related to the proposed Byron Station Units 1 and 2. July 1974 (ADAMS Accession No. ML13273A372)

12. U.S. Nuclear Regulatory Commission, "Generic Environmental Impact Statement for License Renewal of Nuclear Plants," NUREG-1437, Revision 1, June 2013 (ADAMS Accession No. ML13107A023)

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Byron Station, Units 1 and 2 Post-Shutdown Decommissioning Activities Report

13. U.S. Nuclear Regulatory Commission, NUREG-1437, Supplement 54, "Generic Environmental Impact Statement for License Renewal of Nuclear Plants, Supplement 54, Regarding Byron Station, Units 1 and 2," July 2015 (ADAMS Accession No. ML15196A263)

14. U.S. Nuclear Regulatory Commission, NUREG-2157, Vol. 1, "Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel," September 2014 (ADAMS Accession No. ML14196A105)

15. Letter from Patrick Simpson (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission - "License Amendment Request - Proposed Defueled Technical Specifications and Revised License Conditions for Permanently Defueled Condition," dated October 29, 2020 (ADAMS Accession No. ML20304A313)

16. NUREG-1575, "Multi-Agency Radiation and Site Investigation Manual (MARSSIM},"

Revision 1, August 2000 Page 42 of 42