Text

2024 Radiological Environmental Operating Report (AREOR)
	ML25133A032
Person / Time
Site:	Byron
Issue date:	05/12/2025
From:	Welt H; Constellation Energy Generation
To:	; Office of Nuclear Reactor Regulation, Document Control Desk
References
	2025-0029
	Download: ML25133A032 (1)
	v • d • e

C on May 12, 2025 L TR:

BYRON 2025-0029 File:

10.101 2C.111 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Consteilation Ener9y Generation, LLC {CEG)

Byron Station 4450 N. Gerrnan Chtm:h Road Byron, IL 61010-979'1 www.constellationenergy.com Renewed Facility Operating License Nos. NPF-37 and NPF-66 N RC Docket Nos. STN 50-454 and STN 50-455

Subject:

2024 Annual Radiological Environmental Operating Report (AREOR)

In accordance with Technical Specification 5.6.2, "Annual Radiological Environmental Operating Report," we are submitting the Annual Radiological Environmental Operating Report (AREOR) for Byron Station, Units 1 and 2. This report is required to be submitted to the NRG by May 15th of each year and contains the results of the radiological environmental and meteorological monitoring programs. The Radioactive Effluent Release Report was submitted under separate cover.

Also included are the results of groundwater monitoring conducted in accordance with Constellation's Radiological Groundwater Protection Program (RGPP), which is a voluntary program implemented in 2006. This information is being reported in accordance with a nuclear industry initiative.

If you have any questions regarding this information, please contact Ms. Zoe Cox, Regulatory Assurance Manager, at (779) 231-6606.

Respectfully, Harris Welt Site Vice President Byron Generating Station HW/EM/JA/VE

Attachment:

AREOR Report cc:

John Geisner Regional Administrator - NRG Region Ill

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page O of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 2024 Annual Radiological Environmental Operating Report Document Number: 50-454/50-455

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 1 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 TABLE OF CONTENTS 1.0 LIST OF ACRONYMS AND DEFINITIONS................................................................................ 3 2.0 EXECUTIVE

SUMMARY

............................................................................................................ 4 2.1 Summary of

Conclusions:

............................................................................................... 5

3.0 INTRODUCTION

........................................................................................................................ 6 4.0 SITE DESCRIPTION AND SAMPLE LOCATIONS..................................................................... 7 5.0 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM REQUIREMENTS................ 8 6.0 MAPS OF COLLECTION SITES.............................................................................................. 16 7.0 REPORTING LEVELS FOR RADIOACTIVITY CONCENTRATIONS IN ENVIRONMENTAL SAMPLES................................................................................................. 21 8.0 SAMPLING PROGRAM, PROGRAM MODIFICATION AND INTEPRETATION OF RESULTS................................................................................................................................ 22 8.1 Environmental Direct Radiation Dosimetry Results....................................................... 22 8.2 Air Particulate and Radioiodine Sample Results........................................................... 23 8.3 Waterborne Sample Results......................................................................................... 24 8.4 Ingestion Pathway Sample Results............................................................................... 25 9.0 LAND USE CENSUS............................................................................................................... 27 10.0 SAMPLE DEVIATIONS, ANOMALIES AND UNAVAILABILITY................................................ 28 11.0 OTHER SUPPLEMENTAL INFORMATION............................................................................. 30 11.1 NEI 07-07 Onsite Radiological Groundwater Monitoring Program................................. 30 11.2 Corrections to Previous Reports................................................................................... 30 12.0 BIBLIOGRAPHY...................................................................................................................... 31 TABLES Table 1, Radiological Environmental Sampling Program - Exposure Pathway - Direct Radiation......... 8 Table 2, Radiological Environmental Sampling Program - Exposure Pathway - Waterborne................. 9 Table 3, Radiological Environmental Sampling Program - Exposure Pathway - Waterborne............... 10 Table 4, Radiological Environmental Sampling Program - Exposure Pathway - Ingestion................... 11 Table 5, REMP Sampling Locations-Direct Radiation........................................................................ 12 Table 6, Reporting Levels for Radioactivity Concentrations in Environmental Samples....................... 21 Table 7, Maximum Values for the Limit of Detection............................................................................ 21 Table 8: Land Use Census - Nearest Receptors within 5 miles........................................................... 28 Table 9: Sample Deviation Summary................................................................................................... 29 Table 10: Byron Station Data Summary Table..................................................................................... 33 Table 11: Weekly Air Particulate Gross Beta (E-3 pCi/m3).................................................................... 40 Table 12: Quarterly Air Particulate Gamma Isotopic (pCi/m3+/- 2 Sigma).............................................. 43 Table 13: Weekly Air Iodine 1-131 (E-3 pCi/m3)..................................................................................... 45 Table 14: Monthly/Bi-Weekly Milk 1-131 (pCi/L +/- 2 Sigma)................................................................... 48 Table 15: Monthly/Bi-Weekly Milk Gamma Isotopic (pCi/L +/- 2 Sigma)................................................. 49 Table 16: Annual Food Products Gamma Isotopic (pCi/kg Wet+/- 2 Sigma)........................................... 51 Table 17: Monthly Surface Water Gross Beta and Nickel-63 (pCi/L +/- 2 Sigma)................................... 52 Table 18: Monthly Surface Water Gamma Isotopic (pCi/L +/- 2 Sigma).................................................. 53

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 2 of 74 Company: Constellation I Plant: Byron Clean Ener~y Center Units 1 and 2 Table 19: Quarterly Surface Water Tritium (pCi/L +/- 2 Sigma)............................................................. 55 Table 20: Quarterly Ground Water Tritium (pCi/L+/- 2 Sigma).............................................................. 56 Table 21: Quarterly Ground Water Gamma Isotopic (pCi/L +/- 2 Sigma)............................................. 57 Table 22: Semi-Annual Fish Nickel-63 and Gamma Isotopic (pCi/kg Wet+/- 2 Sigma).......................... 59 Table 23: Semi-Annual Shoreline Sediment Nickel-63 and Gamma Isotopic (pCi/kg Dry+/- 2 Sigma)... 60 Table 24: Analytics Environmental Radioactivity Cross Check Program.............................................. 64 Table 25: DO E's Mixed Analyte Performance Evaluation Program (MAPEP)...................................... 66 Table 26: ERA Environmental Radioactivity Cross Check Program..................................................... 68 FIGURES Figure 1, Potential exposure pathways to Members of the Public due to Plant Operations [7]............... 6 Figure 2, Inner Ring and Special Interest OSLO Locations of the Byron Clean Energy Center, 2024... 16 Figure 3, Outer Ring OSLO Locations of the Byron Clean Energy Center, 2024................................. 17 Figure 4, Onsite Air Sampling Locations of the Byron Clean Energy Center, 2024............................. 18 Figure 5, Offsite Air Sampling Locations of the Byron Clean Energy Center, 2024.............................. 19 Figure 6, Ingestion and Waterborne Exposure Pathway Sampling Locations of the Byron Clean Energy Center, 2024........................................................................................................................................ 20 Figure 7, Air Particulate: Analysis for Gross Beta, Average for All Indicator vs. Control Location......... 23 Figure 8: Surface Water Tritium Results.............................................................................................. 24 ATTACHMENTS : Data Table Summary............................................................................................... 33 : Complete Data Table for All Analysis Results Obtained In 2024.

........................... 40 : Cross Check lntercomparison Program.........................

....................... 61 : Environmental Direct Radiation Dosimetry Results..................................................... 70

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 3 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 1.0 LIST OF ACRONYMS AND DEFINITIONS

1.

Airborne Activity Sampling: Continuous sampling of air through the collection of particulates and radionuclides on filter media.

2.

ARERR: Annual Radioactive Effluent Release Report

3.

AREOR: Annual Radiological Environmental Operating Report

4.

BWR: Boiling Water Reactor

5.

Composite Sample: A series of single collected portions (aliquots) analyzed as one sample. The aliquots making up the sample are collected at time intervals that are very short compared to the composite period.

6.

Control: A sampling station in a location not likely to be affected by plant effluents due to its distance and/or direction from the station.

7.

Curie (Ci): A measure of radioactivity; equal to 3.7 x 1010 disintegrations per second, or 2.22 x 1012 disintegrations per minute.

8.

Direct Radiation Monitoring: The measurement of radiation dose at various distances from the plant is assessed using Thermoluminescent Dosimeters (TLD), Optically Stimulated Luminescence Dosimeters (OSLO) and pressurized ionization chambers.

9.

EPA: Environmental Protection Agency

10.

GPI: Groundwater Protection Initiative

11.

Grab Sample: A single discrete sample drawn at one point in time.

12.

Indicator: A sampling location that is likely to be affected by plant effluents due to its proximity and/or direction from the plant.

13.

Ingestion Pathway: The ingestion pathway includes milk, fish, drinking water and garden produce. Also sampled (under special circumstances) are other media such as vegetation or animal products when additional information about particular radionuclides is needed.

14.

ISFSI: Independent Spent Fuel Storage Installation

15.

Lower Limit of Detection (LLD): An a priori measure of the detection capability of a radiochemistry measurement based on instrument setup, calibration, background, decay time, and sample volume. An LLD is expressed as an activity concentration. The MDA is used for reporting results. LLD are specified by a regulator, such as the NRC and are typically listed in the ODCM.

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 4 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2

16.

MDA: Minimum Detectable Activity. For radiochemistry instruments, the MDA is the a posteriori minimum concentration that a counting system detects. The smallest concentration or activity of radioactive material in a sample that will yield a net count above instrument background and that is detected with 95%

probability, with only five% probability of falsely concluding that a blank observation represents a true signal.

17.

MDC: Minimum Detectable Concentration. Essentially synonymous with MDA for the purposes of radiological monitoring.

18.

Mean: The sum of all of the values in a distribution divided by the number of values in the distribution, synonymous with average.

19.

Microcurie: 3.7 x 104 disintegrations per second, or 2.22 x106 disintegrations per minute.

20.

N/A: Not Applicable

21.

NEI: Nuclear Energy Institute

22.

NIST: National Institute of Standards and Technology.

23.

NRG: Nuclear Regulatory Commission

24.

ODCM: Offsite Dose Calculation Manual

25.

OSLO: Optically Stimulated Luminescence Dosimeter

26.

pCi/L: picocuries / Liter

27.

PWR: Pressurized Water Reactor

28.

REMP: Radiological Environmental Monitoring Program

29.

TLD: Thermoluminescent Dosimeter 2.0 EXECUTIVE

SUMMARY

Byron Clean Energy Center Units 1 and 2 Radiological Environmental Monitoring Program (REMP) was established prior to the station becoming operational to provide information on background radiation present in the area. The goal of Byron Clean Energy REMP is to evaluate the impact of the station on the environment.

Environmental samples from different media are monitored as part of the program in accordance with specifications detailed in the Offsite Dose Calculation Manual (ODCM). The program compares data from Indicator locations near the plant, to Control locations farther away from the site to assess operation impacts.

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 5 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 2.1 The Annual Radiological Environmental Operating Report (AREOR) provides data obtained through analyses of environmental samples collected at Byron Clean Energy for the reporting period of January 1st through December 31st, 2024. During that time period 1,430 analyses were performed on 1,268 samples. In assessing all the data gathered for this report and comparing these results with preoperational data and/or 10-year average values, it was concluded that the operation of Byron Clean Energy, had no adverse radiological impact on the envirement.

Summary of

Conclusions:

No measurable activities above background levels were detected. All values were consistent with historical results which indicate no adverse radiological environmental impacts associated with the operation of Byron Clean Energy. Naturally occurring radionuclides are present in the Earth's crust and atmosphere and exists in detectable quantities throughout the world. It is common to detect naturally occurring radionuclides in many of the samples collected for REMP. Some examples of naturally occurring radionuclides that are frequently seen in samples are potassium-40, beryllium-?, actinium-228 (present as a decay product of radium-228), and radium-226. Additionally, some relatively long-lived anthropogenic radioisotopes, such as strontium-90 and cesium-137, are also seen in some REMP samples; these radionuclides exist in measurable quantities throughout the world as a result of fallout from historic atmospheric nuclear weapons testing. Detailed information on the exposure of the U.S. population to ionizing radiation can be found in NCRP Report No. 160 [1].

Annual Radiological Environmental Operating Report I

YEAR: 2024 I

Page 6 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2

3.0 INTRODUCTION

The Radiological Environmental Monitoring Program (REMP) provides data on measurable levels of radiation and radioactive materials in the environment. This program also evaluates the relationship between quantities of radioactive materials released from the plant and resultant doses to individuals from principal pathways of exposure. In this capacity, REMP provides a check on the effluent release program and dispersion modeling to ensure that concentrations in the environment due to radioactive effluents conform to the "As Low as Is Reasonably Achievable" (ALARA) design objectives of 10 CFR 50, Appendix I [2], and implements the requirements of Section IV.B.2 and IV.B.3 of Appendix I. REMP is designed to conform to the Nuclear Regulatory Commission (NRC) Regulatory Guide 4.1 [3], NUREG 1301/1302

[4] [5], and the 1979 NRC Branch Technical Position [6].

0 Gaseous effiuents 0 ~f

\\ Inhalation

~ Depo!<ition 0**~0/

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Radiation O

Radionuclides

- - - : Behavior of radionuclides Figure 1, Potential exposure pathways to Members of the Public due to Plant Operations [7]

Quality assurance aspects of the sampling program and TLD/OSLD data collection are conducted in accordance with Regulatory Guides 4.15 [8] and 4.13 [9]. REMP also adheres to the requirements of Illinois, Byron Clean Energy Technical Specifications, and Offsite Dose Calculation Manual (ODCM). These governing documents dictate the environmental sampling, sample analysis protocols, data reporting and quality assurance requirements for the environmental monitoring program.

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 7 of 74 Company: Constellation

/ Plant: Byron Clean Energy Center Units 1 and 2 The Annual Radiological Environmental Operating Report provides summaries of the environmental data from exposure pathways, interpretations of the data, and analyses of trends of the results. Routinely monitored pathways include ingestion, inhalation, and direct radiation. Routes of exposure are based on site specific information such as meteorology, receptor locations, and water usage around the plant.

4.0 SITE DESCRIPTION AND SAMPLE LOCATIONS Byron Station, a two-unit PWR station, is located about two miles east of the Rock River and approximately three miles southwest of Byron in Ogle County, Illinois. The reactors are designed to have capacities of 1,268 and 1,241 MW gross, respectively.

Unit One loaded fuel in November 1984 and went online February 2, 1985. Unit Two went online January 9, 1987. The station has been designed to keep releases to the environment at levels below those specified in the codes of federal regulations Byron Clean Energy sampling media are selected based on site specific information such as meteorology, receptor locations, and water usage around the plant.

Sampling and analysis frequencies are documented in the Offsite Dose Calculation Manual and site procedures. Required sampling, analysis frequencies and location of sample collected are captured in the following tables and figures:

Table 1, Radiological Environmental Sampling Program - Exposure Pathway -

Direct Radiation Table 2, Radiological Environmental Sampling Program - Exposure Pathway -

Waterborne Table 3, Radiological Environmental Sampling Program - Exposure Pathway -

Waterborne Table 4, Radiological Environmental Sampling Program - Exposure Pathway -

Ingestion Table 5, REMP Sampling Locations - Direct Radiation Figure 2, Inner Ring and Special Interest OSLO Locations of the Byron Clean Energy Center, 2024 Figure 3, Outer Ring OSLO Locations of the Byron Clean Energy Center, 2024 Figure 4, Onsite Air Sampling Locations of the Byron Clean Energy Center, 2024 Figure 5, Offsite Air Sampling Locations of the Byron Clean Energy Center, 2024 Figure 6, Ingestion and Waterborne Exposure Pathway Sampling Locations of the Byron Clean Energy Center, 2024

Annual Radiological Environmental Operating Report l YEAR: 2024 j Page 8 of 74 Company: Constellation l Plant: Byron Clean Energy Center Units 1 and 2 5.0 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM REQUIREMENTS Table 1, Radiological Environmental Sampling Program - Exposure Pathway - Direct Radiation Sample Location Description, Sampling Requirement Distance, and Direction Collection/

Type and Frequency of Analyses Frequency Direct Radiation 65 OSLO monitoring stations with two dosimeters placed as follows:

An inner ring of stations, one in each compass sector in the general area of the site boundary.

An outer ring of stations, one in each compass sector Table 5 Quarterly Gamma dose/Quarterly at approximately 5 miles from the site; and Special interest areas to measure on-site storage facilities.

An "other" set at locations where air samplers are present.

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 9 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 2, Radiological Environmental Sampling Program - Exposure Pathway - Waterborne Sample Location Description, Sampling Requirement Distance, and Direction Collection/

Type and Frequency of Analyses Frequency Airborne Radioiodine and Particulates BY-01 Byron, 3.0 miles N Continuous Samples from 8 locations:

BY-04 Paynes Point, 5.0 miles SE sampler Particulate sampler: Gross Beta operation with BY-06 Oregon, 4.7 miles SSW sample analysis following weekly filter change Four locations close to the site boundary in different sectors BY-08 Leaf River(C), 7.0 miles WNW collection and Gamma isotopic quarterly on of the highest calculated annual average ground level D/Q.

weekly or more composite filters by location on near BY-21 Byron Nearsite North, 0.3 miles N frequently by field and control samples.

Three samples from the vicinity of a community having the BY-22 Byron Nearsite Southeast, 0.4 dust loading, highest calculated annual average D/Q.

miles SE and Radioiodine canister: 1-131 analysis BY-23 Byron Nearsite South, 0.6 miles S radioiodine cannister weekly on near field and control One samples from Control Locations between 4 - 8 miles BY-24 Byron Nearsite Southwest, 0.7 collection samples.

away in the least predominant wind direction.

miles SW weekly

Annual Radiological Environmental Operating Report l YEAR: 2024 I Page 10 of 74 Company: Constellation l Plant: Byron Clean EnerQV Center Units 1 and 2 Table 3, Radiological Environmental Sampling Program - Exposure Pathway - Waterborne Requirement Sample Location Description, Distance, Sampling Collection/ Frequency Type and Frequency of and Direction Analyses Surface Water BY-12 Oregon Pool of Rock River, Monthly composite sample from Gamma isotopic Monthly One sample upstream Downstream, 4.5 miles SSW weekly grab samples; quarterly Gross beta Monthly (control) and one sample BY-29 Byron, Upstream(C), 3.0 miles N composite from weekly grab H-3 Quarterly downstream samples Ni-63 Monthly BY-14-1 3200 North German Church Road, 1.0 miles SSE Groundwater/Well Water BY-18-1 Calhoun, 0.7 miles SSW Gamma isotopic Six indicator locations down gradient from the plant, only if BY-32 Krueger Well, 1.9 miles W Quarterly grab samples Quarterly likely to be affected.

BY-35 Vancko Well, 1.9 miles WNW H-3 Quarterly BY-37 Cavage Well, 2.0 miles WNW BY-38 Steve Storz Well, 2.0 miles WNW Sediment from Shoreline BY-12 Oregon Pool of Rock River, One sample upstream Downstream, 4.6 miles SSW Gamma isotopic (control) and one sample BY-34 Rock River, Upstream of Semiannual grab samples Semiannually downstream (indicator)

Discharge(C), 2.6 miles WNW Ni-63 semiannually

Annual Radiological Environmental Operating Report l YEAR: 2024 I Page 11 of 74 Company: Constellation l Plant: Byron Clean Energy Center Units 1 and 2 Table 4, Radiological Environmental Sampling Program - Exposure Pathway - Ingestion Requirement Sample Location Description, Distance, and Sampling Collection/

Type and Frequency Direction Frequency of Analyses Milk One sample from milking animals in three locations within 5km distance having the highest dose potential. If there are none, then one sample from milking animals in each of Biweekly: May through Gamma isotopic and I-three areas between 5 to 8 km BY-20-1 Ron Snodgrass Farm, 4.8 miles WSW distant where doses are calculated BY-26-2 Joseph Akins Farm(C), 12.2 miles WNW October; Monthly:

131 analysis on each to be greater than 1 mrem per yr.

November through April sample One of samples from milking animals at a control location 15 to 30 km distant and in the least prevalent wind direction.

Fish One sample upstream of each commercially and recreationally Gamma isotopic important species in vicinity of site BY-29 Byron, Upsteam(C), 3.0 miles N Semiannually analysis on edible discharge.

BY-31 Byron, Discharge, 2.6 miles WNW portions One of sample of same species in Ni-63 on edible portions areas not influenced by plant discharge.

Quadrant 1: 5186 Cox Road, Stillman Valley, 4.6 miles E Food products Quadrant 2: 4834 Brick Road, Oregon, 4.9 miles SE Six locations producing vegetables Quadrant 2: 410 Red Oak Lane, Chana, IL, 5.7 miles from areas irrigated by water in SE Gamma isotopic on which liquid plant wastes have been Quadrant 3: 555 Park Rd, Oregon, 3.7 miles SW Annually each sample discharged and one sample Quadrant 4: 4615 N Razorville Road, Byron, 2.7 collected from a control location.

miles SW Quadrant 4: 880 Equestrian Dr., Byron, 1.8 miles W Control: 2327 Route 251, Rochelle, 20.7 miles SE

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 12 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 5, REMP Sampling Locations - Direct Radiation Site#

Location Type Sector Distance Description BY-101-1 Inner Ring N

0.3 miles and -2 BY-102-1 Inner Ring NNE 1.0 miles BY-102-2 Inner Ring NNE 1.0 miles BY-103-1 Inner Ring NE 1.7 miles and -2 BY-103-3 Inner Ring NE 0.4 miles BY-104-1 Inner Ring ENE 1.4 miles and -2 BY-104-3 Inner Ring ENE 0.3 miles BY-105-1 Inner Ring E

1.3 miles and -2 BY-106-1 Inner Ring ESE 1.4 miles and -2 BY-107-1 Inner Ring SE 1.4 miles and -2 BY-107-3 Inner Ring SE 0.4 miles BY-108-1 Inner Ring SSE 0.7 miles BY-108-2 Inner Ring SSE 0.6 miles BY-109-1 Inner Ring s

0.6 miles and -2 BY-110-1 Inner Ring SSW 0.7 miles and -2 BY-111-3 Inner Ring SW 0.8 miles BY-111-4 Inner Ring SW 0.9 miles BY-112-3 Inner Ring WSW 0.8 miles and -4 BY-113-1 Inner Ring w

0.7 miles and -2

Annual Radiological Environmental Operating Report I YEAR: 2024-I Page 13 of 74 Company: Constellation I Plan~yron Clean Enffgy Center Units 1 and 2 Table 5, REMP Sampling Locations - Direct Radiation Site#

Location Type Sector Distance Description BY-114-1 Inner Ring WNW 0.8 miles and -2 BY-115-1 Inner Ring NW 1.0 miles and -2 BY-116-1 Inner Ring NNW 1.4 miles and -2 BY-116-3 Inner Ring NNW 0.9 miles BY-201-3 Outer Ring N

4.4 miles BY-201-4 Outer Ring N

4.4 miles BY-202-1 Outer Ring NNE 4.4 miles BY-202-2 Outer Ring NNE 4.8 miles BY-203-1 Outer Ring NE 4.8 miles BY-203-2 Outer Ring NE 4.7 miles BY-204-1 Outer Ring ENE 4.1 miles BY-204-2 Outer Ring ENE 4.0 miles BY-205-1 Outer Ring E

3.8 miles and -2 BY-206-1 Outer Ring ESE 4.0 miles BY-206-2 Outer Ring ESE 4.3 miles BY-207-1 Outer Ring SE 4.2 miles BY-207-2 Outer Ring SE 3.9 miles BY-208-1 Outer Ring SSE 4.0 miles BY-208-2 Outer Ring SSE 3.8 miles BY-209-1 Outer Ring s

4.0 miles and -4 BY-210-3 Outer Ring SSW 3.9 miles and -4 BY-211-3 Outer Ring SW 4.9 miles and -4

Annual Radiological Environmental Operating Report I

YEAR: 2024 I

Page 14 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 5, REMP Sampling Locations - Direct Radiation Site#

Location Type Sector Distance Description BY-212-3 Outer Ring WSW 4.7 miles and -4 BY-213-1 Outer Ring w

4.7 miles BY-213-4 Outer Ring w

4.7 miles BY-214-1 Outer Ring WNW 4.7 miles BY-214-4 Outer Ring WNW 4.6 miles BY-215-1 Outer Ring NW 4.2 miles BY-215-4 Outer Ring NW 4.2 miles BY-216-1 Outer Ring NNW 4.5 miles BY-216-2 Outer Ring NNW 4.7 miles BY-301-1 Special Interest N

0.3 miles BY-301-2 Special Interest N

0.2 miles BY-309-1 Special Interest s

0.3 miles BY-309-2 Special Interest s

0.4 miles BY-309-3 Special Interest s

0.4 miles BY-309-4 Special Interest SSW 0.4 miles BY-314-2 Special Interest WNW 0.3 miles BY-01-1 Other N

0.3 miles and -2 BY-04-1 Other SE 0.2 miles and -2 BY-06-1 Other SSW 0.3 miles and -2 BY-21-1 Other N

0.4 miles and -2 BY-22-1 Other SE 0.4 miles and -2 BY-23-1 Other s

0.4 miles and -2

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 15 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 5, REMP Sampling Locations - Direct Radiation Site#

Location Type Sector Distance Description BY-24-1 Other SW 0.3 miles and -2 BY-08-1 Control WNW 7.0 miles and -2

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 16 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 6.0 MAPS OF COLLECTION SITES Figure 2, Inner Ring and Special Interest OSLO Locations of the Byron Clean Energy Center, 2024

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 17 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 Leaf River Figure 6 3b Stlllman Valley Outer Ring Dosimeter Locat,ons Inner circle distance = 3.7 m, Outer circle a,stance = 5. 0 m, Figure 3, Outer Ring OSLO Locations of the Byron Clean Energy Center, 2024 H

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Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 18 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2

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Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 19 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 MT.

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Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 20 of 7 4 Company: Constellation I Plant: Bvron Clean Enerav Center Units 1 and 2 Lf: :,J ill\\, [ ct f

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Figure 6, Ingestion and Waterborne Exposure Pathway Sampling Locations of the Byron Clean Energy Center, 2024

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 21 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 7.0 REPORTING LEVELS FOR RADIOACTIVITY CONCENTRATIONS IN ENVIRONMENTAL SAMPLES Table 6, Reporting Levels for Radioactivity Concentrations in Environmental Samples Water Air Particulates Fish (pCi/kg-Food Radionuclide or Gases Milk (pCi/L)

Products (pCi/L)

(pCi/m3) wet)

(pCi/Kg-wet)

H-3 20,000 (1)

NA NA NA NA Mn-54 1,000 NA 30,000 NA NA Fe-59 400 NA 10,000 NA NA Co-58 1,000 NA 30,000 NA NA Co-60 300 NA 10,000 NA NA Zn-65 300 NA 20,000 NA NA Zr-Nb-95 400 NA NA NA NA 1-131 2 (2) 0.9 NA 3

100 Cs-134 30 10 1,000 60 1,000 Cs-137 50 20 2,000 70 2,000 Ba-La-140 200 NA NA 300 NA Table 7, Maximum Values for the Limit of Detection Water Air Particulates Fish Milk Food Products Sediment Radionuclide or Gases (pCi/L)

(pCi/m3)

(pCi/kg-wet)

(pCi/L)

(pCi/Kg-wet)

(pCi/Kg-dry)

H-3 2,000 (3)

NA NA NA NA Mn-54 15 NA 130 NA NA Fe-59 30 NA 260 NA NA Co-58, Co-60 15 NA 130 NA NA Zn-65 30 NA 260 NA NA Zr-Nb-95 15 NA NA NA NA 1-131 1 (4) 0.07 NA 1

60 Cs-134 15 0.05 130 15 60 Cs-137 18 0.06 150 18 80 Ba-La-140 15 NA NA 15 NA 1 For drinking water samples: If no drinking water pathway exists, a value of 30,000 pCi/L may be used.

2 If no drinking water pathway exists, a value of 20 pCi/I may be used NA NA NA NA NA NA NA 150 180 NA 3 If no drinking water pathway exists, a value of 3,000 pCi/L may be used. Some states may require a lower LLD for drinking water sources-per 40 CFR 141 Safe drinking water ACT.

4 If no drinking water pathway exists, a value of 15 pCi/1 may be used

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 22 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 8.0 SAMPLING PROGRAM, PROGRAM MODIFICATION AND INTEPRETATION OF RESULTS At most nuclear stations, data was collected prior to plant operation to determine background radioactivity levels in the environment. Annual data is routinely compared to preoperational and/or 10-year average values to determine if changes in the environs are present. Strict comparison is difficult to make due to fallout from historical nuclear weapon testing. Cesium-137 can be routinely found in environmental samples as a results of above ground nuclear weapons testing. It is important to note, levels of Cs-137 in environment are observed to fluctuate, for example as silt distributions shift due to natural erosion and transport processes, Cs-137 may or may not be observed in sediment samples. Results from samples collected and analyzed during the year, 2024, are described below.

In the following sections, results from direct radiation, air, water, and food products analyzed as part of REMP in 2024 will be discussed. Sampling program descriptions and deviations will also be discussed.

8.1 Environmental Direct Radiation Dosimetry Results Dose is measured as net exposure (field reading less transit reading) normalized to 91-day quarters. Data is treated and analyzed consistent with ANSI/HPS N13.37-2014, which compares the measured dose for each location to the baseline background dose for that location. Environmental dose rates vary by location, depending on geological and land use considerations, and remain relatively constant for any given location (unless land use changes). Some facilities observe seasonal variation in environmental doses. Baseline Background Doses have been determined for both quarterly and annual measurements at each location using historical field measurements.

ANSI/HPS N13.37-2014 uses the concept of minimum differential dose (MOD), which is the minimum facility-related dose that can be detected above background. Due to natural background variations and measurement sensitivities and uncertainties, minimum differential dose is not zero. MOD is calculated based on statistical performance of the dosimetry system in the environment and is site specific.

Normalized doses that exceed the Minimum Differential Dose value above the Baseline Background Dose are considered to indicate Facility-Related Dose; a quality assurance review is performed to verify that any results indicating Facility-Related Dose are accurate.

During the calendar year 2024, a total of 46 locations were monitored and data analyzed in accordance with the requirements in Attachment 4: Environmental Direct Radiation Dosimetry Results, provides the annual direct radiation dosimetry analysis.

There was no direct radiation dose detected from the facility. All OSLO measurements were analyzed, and none were found to have radiation levels that had increased over normal background radiation levels.

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 23 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 8.2 Air Particulate and Radioiodine Sample Results Air particulate filters and charcoal canisters were collected from locations specified in Table 2, Radiological Environmental Sampling Program - Exposure Pathway -

Waterborne. During the calendar year 2024, a total of 416 samples were collected and analyzed for gross beta, gamma emitters and iodine Particulate samplers are used to continuously collect airborne particulates on a filter. The samples are analyzed for gross beta activity following filter changeout which occurs weekly.

Gamma isotopic analysis is also performed on the samples collected at each location and is analyzed quarterly. Naturally occurring beryllium-? was detected on all the control and indicator samples at concentrations consistent with previous years.

Radioiodine (1-131) analysis is performed weekly on radioiodine sample cartridges.

All gross beta analyses of air particulate filters detected gross beta activity at levels consistent with previous years. All air particulate quarterly gamma composite samples were below the detection limit except for naturally occurring radionuclides.

25.0 200 E 3 15.0 0

Q.

"':' 10.0 w

5.0 0.0 Air Particulate: Analysis for Gross Beta, Indicator vs. Control 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 Year

.......,Indicator Control Figure 7, Air Particulate: Analysis for Gross Beta, Average for All Indicator vs. Control Location Air particulate and radioiodine results from this monitoring period, 2024, were compared to 10-year average as shown in Figure 7, and there were no significant changes

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 24 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 8.3 Waterborne Sample Results 8.3.1 Surface Water (i.e., Bay, Lake etc.)

Composite water samples are collected monthly at the upstream control (BY-29) location and at the downstream indicator (BY-12) locations. Monthly composite samples are analyzed for gamma emitters. Aliquots from the monthly composites are combined to form a quarterly composite which is then analyzed for tritium. During the calendar year 2024, a total of 32 surface water samples were collected and analyzed in accordance with the requirements in the ODCM and shown in Table 3, Radiological Environmental Sampling Program - Exposure Pathway - Waterborne. Gross Beta was detected in 23 of the 24 samples with a range of 3 to 6 pCi/L. The required LLD for Gross Beta was met for all samples. Samples from both locations were analyzed for gamma-emitting nuclides. No nuclides were detected and all required LLDs were met Tritium was detected in two samples. The concentrations ranged from 392 to 3,790 pCi/L (Table 19: Quarterly Surface Water Tritium (pCi/L +/- 2 Sigma)). Tritium concentrations in surface water were well below the EPA tritium drinking water limit of 20,000 pCi/L and were consistent with expected levels as a result of permitted liquid discharges.

u Q_

.µ 20000.0

~

2000.0 u

<(

E

J

1=

200.0 Surface Water Tritium Data 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 BY-12 EPA Limit

There are no detected tritium results for BY-29(Control). If there is a detected result in the future, it will be added to the graph.

Figure 8: Surface Water Tritium Results

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 25 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 8.3.2 REMP Groundwater Groundwater samples were collected from control location upgradient from the plant and indicator location down gradient from the plant. During the calendar year 2024, a total of 24 groundwater water samples were collected from offsite monitoring wells and analyzed in accordance with the requirements in the ODCM and shown in Table 3: Radiological Environmental Sampling Program - Exposure Pathway - Waterborne.

A total of six indicator samples were collected. These samples were analyzed for tritium and gamma quarterly. All samples were collected in new unused plastic bottles, which were rinsed with source water prior to collection.

Samples from all locations were analyzed for gamma-emitting nuclides. No nuclides were detected and all required LLDs were met. Tritium concentrations in groundwater were well below the EPA tritium drinking water limit of 20,000 pCi/L. There has been no detectable tritium in any REMP groundwater samples in 2024 or the previous 10 years, therefore, no trend has been established above the detection limit to plot on a trending graph.

8.3.3 Sediment from Shoreline Shoreline sediment collections were made in May and October 2024 and analyzed for gamma-emitting isotopes and nickel-63. Samples are collected at both indicator and control locations. A total of 4 shoreline samples were analyzed in accordance with requirements in the ODCM and shown in Table 3, Radiological Environmental Sampling Program - Exposure Pathway - Waterborne.

Naturally occurring potassium-40 was identified in all shoreline sediment samples from the indicator and control locations with concentrations consistent with previous years.

8.4 Ingestion Pathway Sample Results 8.4.1 Milk Milk samples from milking animals were collected at 2 locations within 5 km having the highest dose potential, along with samples collected from control locations 15-30 km in the least prevalent wind direction. Samples were collected monthly from November-April and bi-weekly through the rest of the year. Samples were analyzed for gamma-emitting isotopes and l-131(Low Level).

Naturally occurring potassium-40 was identified in all milk samples with concentrations consistent with previous years.

8.4.2 Fish A total of 8 fish samples were collected in 2024. These samples were analyzed for gamma emitting radionuclides and nickel-63 in edible portions, in accordance with requirements of the ODCM and summarized in Table 4, Radiological Environmental Sampling Program - Exposure Pathway - Ingestion. These samples are collected from the indicator and control areas as required by the ODCM.

Annual Radiological Environmental Operating Report

[ YEAR: 2024 [

Page 26 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Naturally occurring potassium-40 was identified in all fish samples with concentrations consistent with previous years.

8.4.3 Food Products A total of 10 food product type samples were analyzed in 2024, for gamma emitting radionuclides in accordance with requirements of the ODCM, as summarized in Table 4, Radiological Environmental Sampling Program - Exposure Pathway - Ingestion.

Naturally occurring potassium-40 was identified in all food product samples from the indicator and control locations with concentrations consistent with previous years.

Beryllium-?, also naturally reoccurring, was detected in one of the indicator samples and two of the control locations in 2024.

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 27 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 9.0 LAND USE CENSUS An annual land use census is required by the Offsite Dose Calculation Manual and is performed to ensure that changes in the use of areas at or beyond the site boundary are identified and modifications to REMP are made if required by changes in land use. The land use census satisfies the requirements of Section IV.B.3 of Appendix I to 10 CFR 50 [2]. NUREG-1301/1302 Control 3.12.2 specifies that "a Land Use Census shall be conducted and shall identify within a distance of 8 km (5 mi.) the location in each of the 16 meteorological sectors of the nearest milk animal, the nearest residence and the nearest garden of greater than 50 m2 (500 ft2) producing broad leaf vegetation. Note, per NUREG-1301/1302, Broad leaf vegetation sampling of at least three different kinds of vegetation may be performed at the SITE BOUNDARY in each of two different direction sectors with the highest predicted D/Qs in lieu of the garden census.

A Land Use Census was conducted during the calendar year, 2024, within the growing season to identify changes in land use, receptor locations, and new exposure pathways. The results for the 2024 Land Use Census are listed in Table 8: Land Use Census - Nearest Receptors within 5 miles. In summary, the highest D/Q locations for nearest livestock, nearest residence and nearest milk animal did not change following the 2024 census.

The land use census included the addition of a new livestock location found on 9/3/2024 that is 5.1 miles away from the station. All other locations remain the same.

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 28 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 I

Table 8: Land Use Census - Nearest Receptors within 5 miles Sector Direction Nearest Distance Nearest Milk Distance Livestock Residence (Miles)

Animal (Miles)

A N

5362 N. Kufalk 1.21 2779 Lynn Road, Byron, Road, Byron, IL IL 3519 E. Whitaker Lynn Rd West of Baker B

NNE Road, Byron, IL, 1.57 dead end road Rd, Byron, IL 4963 German Reeverts Farm. German C

NE Church Rd. Byron, 1 08 Church Road, Byron, IL IL D

ENE 4754 Black Walnut 1.40 5886 Stillman Road, Road Byron, IL Stillman Valley, IL.

E E

4252 Black Walnut 1.00 5785 Weld Road, Rd, Byron, IL Stillman Valley, IL.

F ESE 3525 Black Walnut 1.47 3525 Black Walnut Rd, Road, Byron, IL Byron, IL G

SE 3960 Black Walnut 170 6898 E. Brick Rd, Road, Byron, IL Chana, IL.

3485 German H

SSE Church Rd. Byron, 0.71 4232 Limerick Road IL.

J s

2761 Deer Path 0.63 2761 Deer Path Road.

Road, Byron, IL Byron, IL K

SSW 2386 Deer Path 0.69 2386 Deer Path Rd, Road, Oregon, IL Byron, IL L

SW 2277 Deer Path 0.77 1381 Pleasant Grove Road, Oregon. IL Road, Oregon, iL.

3418 Spring Creek 3082 N. Silver Razorville Road, North M

WSW 1.60 Creek Road, Mt.

4.5 Road, Byron, IL.

Morris, IL of Met Tower R Grabowski. 879 3909 Town Hall Road, N

w Equestrian Road, 1.76 Mt. Morris. IL Byron, IL.

1260 Old Wagon 7361 N. Mile Curly Cattle Ranch, p

WNW 1.56 Road, Forreston, 11.5 1260 Old Wagon Road, Road, Byron, IL IL Byron, IL Benesh, 4629 1482 Acorn Road, Q

NW Razorville Road, 0.80 Byron Byron, IL 2525 Ash Road, Swanson Shorthorns, R

NNW Byron, IL. (Near 0.92 5413 Razorville Road, moto sport park)

Byron, IL 10.0 SAMPLE DEVIATIONS, ANOMALIES AND UNAVAILABILITY Sampling and analysis are performed for media types addressed in the Offsite Dose Calculation Manual. Sampling and analysis challenges may be experienced due to a multitude of reasons including environmental factors, loss of TLDs/OSLDs, contamination of samples, etc. To aid classification of sampling and analysis challenges experienced in 2024, the following three terms are used to describe the issues: Sample Anomalies, Sample Deviation, and Unavailable Samples.

I Distance (Miles) 5.9 6.2 2.0 3.7 4.2 1.5 5.1 3.3 0.7 0.7 2.0 0.8 3.2 1.6 1.5 1.4

Annual Radiological Environmental Operating Report

[ YEAR: 2024

[

Page 29 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Media that experienced downtime (i.e., air samplers or water samplers) during a surveillance period are classified a "Sample Deviation". "Sample Anomalies" are defined as errors that were introduced to a sample once it arrived in the laboratory, errors that prevents the sample from being analyzed as it normally would or may have altered the outcome of the analysis (i.e., cross contamination, human error).

"Sample Unavailability" is defined as sample collection with no available sample (i.e.,

food crop, TLD).

All required samples were collected and analyzed as scheduled except for the following:

Table 9: Sample Deviation Summary Sample Type Collection Reason for not conducting REMP Plans for preventing Location Date or and Analysis Period sampling as required by ODCM reoccurrence AP/Al-Gross N/A Beta and 1-131 All Air Samples 6/25/24 Samples lost by FedEx during shipment Samples retrieved 7/12; 3-week delay in testing AP-Gross Beta BY-04 1 /16/24 Pump not working due to bearing failure Pump was replaced AP-Gross Beta BY-04 5/7/24 Timer indicated ran 5.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months less due to N/A power outage from storm Weather dependent AP-Gross Beta BY-06 4/2/24 Filter washed out by heavy rain NIA Weather dependent AP-Gross Beta BY-08, BY-24 7/16/24 No power at the station N/A Timer indicates loss of hours due to N/A AP-Gross Beta BY-08, BY-24 7/23/24 heavy storms in the area-possible power outage Weather dependent Timer indicates loss of hours due to N/A AP-Gross Beta BY-08, BY-01 7/16/24 heavy storms in the area-possible power outage Weather dependent AP-Gross Beta BY-21 7/9/24 Filter appears washed out by heavy rain N/A Weather dependent AP-Gross Beta BY-21 7/16/24 Filter appears washed out by heavy rain N/A Weather dependent N/A Collector was unable to collect samples Weather dependent AP-Gross Beta BY-22 1 /16/24 as scheduled due to snow accumulation around sampler.

Samples were collected until snow clearing Timer indicates lower reading due to AP-Gross Beta BY-22 1/23/24 only being 5 days due to the previous N/A week's sample not getting collected until snow clearing AP-Gross Beta BY-22 5/7/24 Timer indicated 4.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months less due to N/A power outage from a storm Weather dependent AP-Gross Beta BY-23 5/7/24 Timer indicated 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months less due to N/A power outage from a storm Weather dependent AP/Al-Gross Timer indicated 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months less than N/A Betaandl-131 BY-24 5/7/24 expected due to a power outage from a Weather dependent storm.

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 30 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 11.0 11.1 11.2 Table 9: Sample Deviation Summary Milk-Gamma BY-20-1, BY-26-2 7/2/24 Sample lost by UPS Resampled 7/9 Isotopic and 1-131 wr-Gross Beta, Sample unable to be collected due to N/A Nickel-63, BY-29 1/16/24 Gamma Isotopic river being frozen Weather Dependent wr-Gross Beta, BY-29 Sample unable to be collected due to NIA Nickel-63, 1/23/24 Gamma Isotopic river being frozen Weather Dependent wr-Gross Beta, BY-29 Sample unable to be collected due to N/A Nickel-63, 12/3/24 river being frozen Weather Dependent Gamma Isotopic wr-Gross Beta, BY-29 Sample unable to be collected due to N/A Nickel-63, 12/10/24 Gamma Isotopic river being frozen Weather Dependent wr-Gross Beta, BY-29 Sample unable to be collected due to N/A Nickel-63, 12/17/24 Gamma Isotopic river being frozen Weather Dependent wr-Gross Beta, BY-29 Sample unable to be collected due to N/A Nickel-63, 12/23/24 Gamma Isotopic river being frozen Weather Dependent OSLO BY-111-3 9/2/24 One OSLO found on ground N/A Reattached to pole OSLO BY-213-1 4th Qtr. 2024 TLD found to be missing during 4th Quarter 2024 TLD exchange OTHER SUPPLEMENTAL INFORMATION NEI 07-07 Onsite Radiological Groundwater Monitoring Program Byron Clean Energy Center Units 1 and 2 has developed a Groundwater Protection Initiative (GPI) program in accordance with NEI 07-07, Industry Ground Water Protection Initiative - Final Guidance Document. The purpose of the GPI is to ensure timely detection and an effective response to situations involving inadvertent radiological releases to groundwater in order to prevent migration of licensed radioactive material off-site and to quantify impacts on decommissioning. It is important to note, samples and results taken in support of NEI 07-07 on-site groundwater monitoring program are separate from the Radiological Environmental Monitoring Program (REMP). Results of the NEI 07-07 Radiological Groundwater Monitoring Program for onsite groundwater wells are provided in the ARERR.

Corrections to Previous Reports There were no corrections to the previous reports in 2024

Annual Radiological Environmental Operating Report J

YEAR: 2024 J

Page 31 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 12.0 BIBLIOGRAPHY (1] NCRP, "Report No. 160, Ionizing Radiation Exposure of the Population of the United States,"

National Council on Radiation Protection, Bethesda, 2009.

[2] "10 CFR 50, "Domestic Licensing of Production and Utilization Facilities"," US Nuclear Regulatory Commission, Washington, DC.

[3] "Regulatory Guide 4.1, "Radiological Environmental Monitoring for Nuclear Power Plants",

Revision 2," Nuclear Regulatory Commission, 2009.

[4] "NUREG-1301, "Offsite Dose Calculation Manual Guidance: Standard Radiological Effluent Controls for Pressurized Water Reactors,".," Nuclear Regulatory Commission, April 1991.

[5] "NUREG-1302, "Offsite Dose Calculation Manual Guidance: Standard Radiological Effluent Controls for Boiling Water Reactors,"," Nuclear Regulatory Commission, April 1991.

[6] "Branch Technical Position, Revision 1," NRC000096, Submitted March 30, 2012, November 1979.

[7] "Japan Atomic Energy Agency," 06 November 2020. [Online]. Available:

https://www.jaea.go.jp/english/04/ntokai/houkan/houkan_02.html.

[8] "Regulatory Guide 4.15, Quality Assurance for Radiological Monitoring Programs (Inception through Normal Operations to License Termination) -- Effluent Streams and the Environment,"

Nuclear Regulatory Commission, July, 2007.

[9] "Regulatory Guide 4.13, Performance, Testing, and Procedural Specifications for Thermoluminescence Dosimetry: Environmental Applications, Revision 2," Nuclear Regulatory Commision, June, 2019.

[10] "NUREG/CR-2919, "XOQDOQ Computer Program for the Meteorological Evaluation of Routine Effluent Releases at Nuclear Power Stations,"," Nuclear Regulatory Commission, September, 1982.

[11] "Measurements of Radionuclides in the environment Sampling and Analysis of plutonium in soil,"

Nuclear Regulatory Commission, 1974.

[12] "Ionizing Radiation Exposure of the Population of the United States," Bethesda, MD, 2009.

[13] Nuclear Regulatory Commission, 30 June 2015. [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/students/animated-pwr.html. [Accessed October 2020].

[14] "ICRP Publication 60, "ICRP Publication 60: 1990 Recommendations of the International Commission on Radiological Protection, 60," Annals of the ICRP Volume 21/1-3,," International Commission on Radiation Protection, October, 1991.

(15] "NRC Resource Page," [Online]. Available: http://www.nrc.gov/about-nrc/radiation.html. [Accessed 10 November 2020].

[16] "NUREG-0133, Preparation of Effluent Technical Specifications for Nuclear PowerPlants,"

Nuclear Regulatory Commission, 1987.

[17] "Regulatory Guide 1.109, "Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Demonstrating Compliance with 10 CFR Part 50, Appendix I,,"

Nuclear Regulatory Commission, Ocotober, 1977.

[18] (Online]. Available: http://hps.org/hpspublications/radiationfactsheets.html. [Accessed 2020].

[19] "NEI 07-07, "Industry Ground Water Protection Initiative-Final Guidance Document,"," Nuclear Energy Institute, Washington, D.C..

Annual Radiological Environmental Operating Report

[ YEAR: 2024 [

Page 32 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2

[20] "ANSI 13.37, Environmental Dosimetry-Criteria for System Design and Implementation," Health Physics Society (HPS), May, 2019.

[21] "40 CFR Part 141, "National Primary Drinking Water Regulations,"," US Environmental Protection Agency, Washington, DC..

[22] Nuclear Regulatory Commission, 25 June 2015. [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/students/animated-bwr.html. [Accessed October 2020].

[23] "40 CFR 190 - Environmental Radiation Protection Standards for Nuclear Power Operation," US Environmental Protection Agency, Washington, DC.

[24] "NUREG-0324 - XOQDOQ, Program for the Meteorological Evaluation of Routine Effluent Releases at Nuclear Power Stations," Nuclear Regulatory Commission, September, 1977.

[25] "NCRP Report No. 160- Ionizing Radiation Exposure of the Population of the United States,"

National Council on Radiation Protection and Measurements, Bethesda, MD, 2009.

[26] "10 CFR 20 - Standards for Protection Against Radiation," US Nuclear Regulatory Commission, Washington, DC.

Medium or Pathway Sampled (Units)

Air Particulates (E-03 pCi/m3)

Airborne Radioiodine (E-03 pCi/m3)

Direct Radiation (mrem/qtr.)

Annual Radiological Environmental Operating Report j YEAR: 2024 j

Page 33 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Type, Total Lower Number of Limit of Analyses Detection performed (LLD)

(e.g., 1-131, 400)

Gross Beta, 416 10 Mn-54 N/A Co-58 N/A Fe-59 N/A Co-60 N/A Zn-65 N/A

Gamma, Nb-95 N/A 32 Zr-95 N/A 1-131 N/A Cs-134 50 Cs-137 60 Ba-140 N/A La-140 N/A Gamma, 416 70 1-131 Gamma Dose, 328 N/A : Data Table Summary Table 10: Byron Station Data Summary Table Indicator Location with Highest Annual Mean Means; (f6).

Means Name (f6)

Ranges Distance and Direction Range5 BY-21 18 (356/364)

BYRON NEARSITE NORTH 19 (45/52)

(5/41) 0.3 MILES N OF SITE (6.3/37)

< LLD

< LLD 20.6 BY-107-2 24.2 (328/328) 1.4 miles SE (4/4)

(13.9/26)

(23.6/25. 7)

Control Means (f6).

Ranges 17 (49/52)

(5.8/34)

< LLD

< LLD N/A N/A 5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses Number of Nonroutine Reported Measurements 0

0 0

Annual Radiological Environmental Operating Report

~~ L~~AR: 2024 I Page 34 of 74 Company: Constellation l Plant: Byron Clean Enerav Center Units 1 and 2 : Data Table Summary Table 10: Byron Station Data Summary Table Type, Total Number Lower Indicator Location with Highest Annual Mean Medium or Pathway of Analyses Limit of Mean5; Sampled (Units) performed Detection (f6).

Means (e.g., 1-131, 400)

(LLD)

Range5 Name (f6)

Distance and Direction Range5 l-131(Low Level), 38 1

< LLD

< LLD Mn-54 N/A

< LLD

< LLD Co-58 N/A

< LLD

< LLD Fe-59 N/A

< LLD

< LLD Co-60 N/A

< LLD

< LLD Milk Zn-65 NIA

< LLD

< LLD (pCi/L)

Gamma, Nb-95 N/A

< LLD

< LLD 38 Zr-95 N/A

< LLD

< LLD Cs-134 15

< LLD

< LLD Cs-137 18

< LLD

< LLD Ba-140 60

< LLD

< LLD La-140 15

< LLD

< LLD 5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses Control Means (f6).

Ranges

< LLD

< LLD Number of Nonroutine Reported Measurements 0

0 0

0

Annual Radiolog!cal Environl!'ental Operating Report I YEAR: 2024 I Page 35 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Data Table Summary Table 10: Byron Station Data Summary Table Type, Total Number Lower Indicator Location with Highest Annual Mean Number of Medium or Pathway of Analyses Limit of Means; Control Nonroutine Means (f6).

Sampled (Units) performed Detection (f6).

Means Ranges Reported (e.g., 1-131, 400)

(LLD)

Ranges Name (f6)

Measurements Distance and Direction Ranges Mn-54 N/A

< LLD

< LLD 0

Co-58 N/A

< LLD

< LLD 0

Fe-59 N/A

< LLD

< LLD 0

Co-60 N/A

< LLD

< LLD 0

Zn-65 N/A

< LLD

< LLD 0

Food Products

Gamma, Nb-95 N/A

< LLD

< LLD 0

(pCi/kg Wet) 10 Zr-95 N/A

< LLD

< LLD 0

1-131 60

< LLD

< LLD 0

Cs-134 60

< LLD

< LLD 0

Cs-137 80

< LLD

< LLD 0

Ba-140 N/A

< LLD

< LLD 0

La-140 N/A

< LLD

< LLD 0

5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses

Annual Radiological Environmental Operating Report

[ YEAR: 2024 _ I Page 36 of 74 Company: Constellation l Plant: Byron Clean Energy Center Units 1 and 2 : Data Table Summary Table 10: Byron Station Data Summary Table Type, Total Lower Indicator Location with Highest Annual Mean Medium or Number of Limit of Mean5; Pathway Sampled Analyses Means (Units) performed Detection

{f6).

Name (f6)

(e.g., 1-131, 400)

(LLD)

Range5 Distance and Direction Ranges BY-12 Oregon Gross Beta, 24 4

4.3 (12/12)

Pool of Rock River-4.3 (12/12)

Downstream (3.1/5.7) 4.5 miles SSW (3.1 /5. 7)

BY-12 Oregon Pool of Rock H-3, 8 200 2584 (3/5)

River-Downstream 2584 (3/5)

(392/3790) 4.5 miles SSW (392/2790)

Ni-63, 24 30

< LLD

< LLD Surface Water Mn-54 15

< LLD

< LLD (pCi/L)

Co-58 15

< LLD

< LLD Fe-59 30

< LLD

< LLD Co-60 15

< LLD

< LLD Zn-65 30

< LLD

Gamma, Nb-95 15

< LLD

< LLD 24 Zr-95 30

< LLD

< LLD 1-131 15

< LLD

< LLD Cs-134 15

< LLD

< LLD Cs-137 18

< LLD

< LLD Ba-140 60

< LLD

< LLD La-140 15

< LLD

< LLD 5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses Control Means (f6).

Ranges 4.2 (11/12)

(3.1 /5.4)

< LLD

< LLD Number of Nonroutine Reported Measurements 0

0 0

Annual Radiological Environmental Operating Report J

YEAR: 2024 J

Page 37 of 74 Com~'!Y_:_Constellation

_ _l Plant: B_yron Clean Energy Center Units 1 and 2 : Data Table Summary Table 10: Byron Station Data Summa'}' Table Type, Total Lower Indicator Location with Highest Annual Mean Number of Medium or Pathway Number of Limit of Means; Control Non routine Sampled (Units)

Analyses Detection (f6).

Means Means (f6).

Reported performed (LLD)

Name (f6)

Ranges Measurements (e.g., 1-131, 400)

Ranges Distance and Direction Ranges H-3, 24 200

< LLD

< LLD N/A 0

Mn-54 15

< LLD

< LLD N/A 0

Co-58 15

< LLD

< LLD N/A 0

Fe-59 30

< LLD

< LLD N/A 0

Ground Water Co-60 15

< LLD

< LLD N/A 0

(pCi/L)

Zn-65 30

< LLD

< LLD N/A 0

Gamma, Nb-95 15

< LLD

< LLD N/A 0

24 Zr-95 30

< LLD

< LLD N/A 0

1-131 15

< LLD

< LLD N/A 0

Cs-134 15

< LLD

< LLD NIA 0

Cs-137 18

< LLD

< LLD N/A 0

Ba-140 60

< LLD

< LLD N/A 0

La-140 15

< LLD

< LLD N/A 0

5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses

Annual Radiological Environmental Operating Report

[ YEAR: 2024 [

Page 38 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Data Table Summary Table 10: Byron Station Data Summary Table Type, Total Number Lower Indicator Location with Highest Annual Mean Number of Medium or Pathway of Analyses Limit of Mean5; Control Nonroutine Mean 5 (f6).

Sampled (Units) performed Detection (f6).

Name Mean 5 Range5 Reported (e.g., 1-131, 400)

(LLD)

Range 5 Distance and Direction (f6)

Measurements Range5 Ni-63, 8 260

< LLD

< LLD 0

Mn-54 130

< LLD

< LLD 0

Co-58 130

< LLD

< LLD 0

Fe-59 260

< LLD

< LLD 0

Co-60 130

< LLD

< LLD 0

Zn-65 260

< LLD

< LLD 0

Fish Gamma, 8 Nb-95 NIA

< LLD

< LLD 0

(pCilkg Wet)

Zr-95 NIA

< LLD

< LLD 0

Cs-134 130

< LLD

< LLD 0

Cs-137 150

< LLD

< LLD 0

Ba-140 NIA

< LLD

< LLD 0

La-140 NIA

< LLD

< LLD 0

5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses

Annual Radiological Environmental Oper~ting Report I YEAR: 2024 I Page 39 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Data Table Summary Table 10: Byron Station Data Summary Table Type, Total Lower Indicator Location with Highest Annual Mean Number of Medium or Pathway Number of Limit of Means; Control Nonroutine Sampled (Units)

Analyses Detection (f6).

Name Means Means (f6).

Reported performed (LLD)

Ranges Distance and Direction (f6)

Ranges Measurements (e.g., 1-131, 400)

Ranges Ni-63, 4 260

< LLD

<LLD

<LLD 0

Mn-54 N/A

< LLD

< LLD 0

Co-58 N/A

< LLD

< LLD 0

Fe-59 N/A

< LLD

< LLD 0

Co-60 N/A

< LLD

< LLD 0

Zn-65 N/A

< LLD

< LLD 0

Sediment Gamma, 4 Nb-95 N/A

< LLD

< LLD 0

(pCi/kg Dry)

Zr-95 N/A

< LLD

< LLD 0

Cs-134 150

< LLD

< LLD 0

Cs-137 180

< LLD

< LLD 0

Ba-140 N/A

< LLD

< LLD 0

La-140 N/A

< LLD

< LLD 0

5 Mean and range are based on detectable measurements only.

6 Fraction are based on detectable measurements at specified locations is indicated in parentheses

Annual Radiological Enviromnental Oper~ting Report I YEAR: 2024 I Page 40 of 74 Collection Date 01/02/2024 01/09/2024 01/16/2024 01/23/2024 01/30/2024 02/06/2024 02/13/2024 02/20/2024 02/27/2024 03/05/2024 03/12/2024 03/19/2024 03/26/2024 04/02/2024 04/09/2024 04/16/2024 04/23/2024 04/29/2024 05/07/2024 05/14/2024 05/21/2024 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 BY-21 18

+/-

18

+/-

24

+/-

8

+/-

13

+/-

19

+/-

19

+/-

24

+/-

28

+/-

20

+/-

21

+/-

15

+/-

10

+/-

6

+/-

13

+/-

14

+/-

16

+/-

11

+/-

14

+/-

17

+/-

16

+/- : Complete Data Table for All Analysis Results Obtained In 2024 Note: Throughout Attachment 2, bold data entries are for the reported concentration Table 11: Weekly Air Particulate Gross Beta (E-3 pCi/m3)

BY-22 BY-23 BY-24 BY-01 BY-04 BY-06 5

22

+/-

5 18

+/-

5 11

+/-

4 21

+/-

5 17

+/-

5 14

+/-

5 4

4 18

+/-

4 21

+/-

4 22

+/-

5 18

+/-

5 25

+/-

5 5

23

+/-

6(1) 24

+/-

5 14

+/-

4 25

+/-

5 23

+/-

4(1) 24

+/-

4 3

13

+/-

4(1) 10

+/-

4 10

+/-

4 13

+/-

4 9

+/-

3 12

+/-

4 4

13

+/-

4 13

+/-

4 17

+/-

4 16

+/-

4 16

+/-

4 15

+/-

4 4

19

+/-

4 17

+/-

4 17

+/-

4 16

+/-

4 20

+/-

4 18

+/-

4 4

17

+/-

4 16

+/-

4 18

+/-

4 19

+/-

5 15

+/-

4 19

+/-

5 5

23

+/-

5 24

+/-

5 25

+/-

5 13

+/-

4 21

+/-

5 22

+/-

5 5

18

+/-

4 16

+/-

4 18

+/-

4 16

+/-

4 19

+/-

4 19

+/-

4 4

18

+/-

4 15

+/-

4 16

+/-

4 18

+/-

4 14

+/-

4 15

+/-

4 4

13

+/-

4 22

+/-

4 14

+/-

4 17

+/-

4 18

+/-

4 17

+/-

4 4

17

+/-

4 15

+/-

4 16

+/-

4 15

+/-

4 14

+/-

4 11

+/-

4 3

13

+/-

4 14

+/-

4 13

+/-

4 12

+/-

4 13

+/-

4 4

3 10

+/-

4 7

+/-

3 4

5

+/-

3 6

+/-

3 5(1) 4 11

+/-

4 12

+/-

4 12

+/-

4 11

+/-

4 9

+/-

4 4

4 16

+/-

4 16

+/-

4 14

+/-

4 14

+/-

4 12

+/-

4 10

+/-

3 5

18

+/-

5 15

+/-

4 16

+/-

5 14

+/-

4 17

+/-

5 7

+/-

4 3

12

+/-

3 10

+/-

3 9

+/-

3 10

+/-

3 9

+/-

3 8

+/-

3 4

14

+/-

4(1) 14

+/-

4(1) 13

+/-

4(1) 13

+/-

4 13

+/-

4(1) 12

+/-

4 4

14

+/-

4 13

+/-

4 10

+/-

4 13

+/-

4 14

+/-

4 10

+/-

4 4

12

+/-

4 17

+/-

4 13

+/-

4 14

+/-

4 15

+/-

4 12

+/-

4 (1> Refer to Sample Deviation Summary Table 9 11 24 20 11 15 16 17 22 15 16 18 13 10 6

11 13 16 10 10 13 14 BY-08

+/-

4

+/-

5

+/-

4

+/-

4

+/-

4

+/-

4

+/-

4

+/-

5

+/-

4

+/-

4

+/-

4

+/-

4

+/-

3

+/-

3

+/-

4

+/-

4

+/-

5

+/-

3

+/-

4

+/-

4

+/-

4

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 41 of 74 Company: Constellation I Plant: Byron Cl~an_En~rgy_ Center Units 1 and 2 Table 11: Weekly Air Particulate Gross Beta (E-3 pCi/m3) Cont'd Collection BY-21 BY-22 BY-23 BY-24 BY-01 BY-04 BY-06 BY-08 Date 05/28/2024 13

+/-

4 15

+/-

4 15

+/-

4 15

+/-

4 14

+/-

4 15

+/-

4 14

+/-

4 12

+/-

4 06/04/2024 10

+/-

4 10

+/-

4 10

+/-

4 11

+/-

4 8

+/-

4 10

+/-

4 7

+/-

3 10

+/-

4 06/11/2024 19

+/-

4 20

+/-

4 15

+/-

4 16

+/-

4 23

+/-

4 18

+/-

4 21

+/-

4 15

+/-

4 06/18/2024 8

+/-

4 15

+/-

4 19

+/-

4 13

+/-

4 17

+/-

4 22

+/-

5 17

+/-

4 14

+/-

4 06/25/2024 5(1) 14

+/-

4(1) 11

+/-

4(1) 9

+/-

4(1) 14

+/-

4(1) 13

+/-

4(1) 12

+/-

4(1) 13

+/-

4(1) 07/02/2024 5

16

+/-

4 12

+/-

4 15

+/-

4 14

+/-

4 14

+/-

4 16

+/-

4 14

+/-

4 07/09/2024 6(1) 13

+/-

4 8

+/-

4 13

+/-

5 14

+/-

5 10

+/-

4 12

+/-

4 15

+/-

5 07/16/2024 15

+/-

4(1) 19

+/-

4 15

+/-

4 16

+/-

4(1) 15

+/-

4(1) 17

+/-

4 15

+/-

4 7

+/-

3(1) 07/23/2024 20

+/-

4 15

+/-

4 19

+/-

4 14

+/-

4(1) 17

+/-

4 14

+/-

4 17

+/-

4 18

+/-

4(1) 07/30/2024 22

+/-

5 19

+/-

4 20

+/-

4 18

+/-

4 21

+/-

5 6

+/-

3 21

+/-

4 18

+/-

4 08/06/2024 14

+/-

4 16

+/-

4 10

+/-

4 14

+/-

4 17

+/-

4 14

+/-

4 19

+/-

4 12

+/-

4 08/13/2024 22

+/-

5 20

+/-

5 22

+/-

5 20

+/-

5 23

+/-

5 21

+/-

5 22

+/-

5 19

+/-

5 08/19/2024 25

+/-

5 19

+/-

4 25

+/-

5 19

+/-

4 24

+/-

4 22

+/-

4 25

+/-

4 25

+/-

4 08/27/2024 20

+/-

4 20

+/-

4 15

+/-

4 17

+/-

4 22

+/-

4 18

+/-

4 19

+/-

4 17

+/-

4 09/03/2024 18

+/-

4 17

+/-

4 20

+/-

4 17

+/-

4 17

+/-

4 18

+/-

4 19

+/-

4 20

+/-

4 09/10/2024 37

+/-

5 30

+/-

5 32

+/-

5 35

+/-

5 41

+/-

6 35

+/-

5 33

+/-

5 34

+/-

5 09/17/2024 29

+/-

5 28

+/-

5 25

+/-

5 25

+/-

5 31

+/-

5 28

+/-

5 30

+/-

5 29

+/-

5 09/24/2024 21

+/-

4 15

+/-

4 24

+/-

5 18

+/-

4 26

+/-

5 20

+/-

4 26

+/-

5 22

+/-

5 10/01/2024 23

+/-

4 19

+/-

4 22

+/-

4 21

+/-

4 26

+/-

5 22

+/-

4 28

+/-

5 24

+/-

5 10/08/2024 22

+/-

4 21

+/-

4 22

+/-

4 22

+/-

4 24

+/-

5 19

+/-

4 21

+/-

4 25

+/-

5 10/15/2024 24

+/-

4 26

+/-

4 29

+/-

5 22

+/-

4 23

+/-

4 24

+/-

4 29

+/-

5 23

+/-

4 10/22/2024 25

+/-

5 30

+/-

5 26

+/-

5 20

+/-

4 29

+/-

5 24

+/-

5 26

+/-

5 26

+/-

5

<1J Refer to Sample Deviation Summary Table 9

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 42 of 74 Company: Constellation

~

lt=>JanJ:J;~yron Clean Energy Center Units 1 and 2 Table 11: Weekly Air Particulate Gross Beta (E-3 pCi/m3) Cont'd Collection BY-21 BY-22 BY-23 BY-24 BY-01 BY-04 BY-06 BY-08 Date 10/29/2024 18

+/-

4 22

+/-

5 16

+/-

4 17

+/-

4 23

+/-

5 20

+/-

5 21

+/-

5 17

+/-

4 11/05/2024 17

+/-

4 21

+/-

5 19

+/-

4 18

+/-

4 17

+/-

4 18

+/-

4 12

+/-

4 20

+/-

4 11/12/2024 21

+/-

5 21

+/-

5 28

+/-

5 22

+/-

5 19

+/-

4 25

+/-

5 18

+/-

4 22

+/-

5 11/19/2024 14

+/-

4 14

+/-

4 17

+/-

4 11

+/-

4 13

+/-

4 11

+/-

4 16

+/-

4 17

+/-

4 11/26/2024 22

+/-

5 12

+/-

4 22

+/-

5 24

+/-

5 24

+/-

5 23

+/-

5 25

+/-

5 21

+/-

4 12/03/2024 21

+/-

4 25

+/-

5 23

+/-

5 26

+/-

5 24

+/-

5 25

+/-

5 23

+/-

5 22

+/-

4 12/10/2024 28

+/-

5 26

+/-

4 29

+/-

5 20

+/-

4 26

+/-

4 25

+/-

4 27

+/-

5 28

+/-

5 12/17/2024 25

+/-

5 30

+/-

6 27

+/-

5 21

+/-

5 26

+/-

5 25

+/-

5 28

+/-

5 20

+/-

5 12/23/2024 26

+/-

4 24

+/-

4 23

+/-

4 22

+/-

4 21

+/-

4 25

+/-

4 24

+/-

4 21

+/-

4

Annual Radiological Environmental Operating Report l.. YEAR: 202~ J Page 43 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 12: Quarterly Air Particulate Gamma Isotopic (pCi/m3+/- 2 Sigma)

Station Nuclide Q1 Q2 Q3 Q4 Station Nuclide Q1 Q2 Q3 Q4 Mn-54 1

2 5

4 Mn-54 2

3 2

3 Co-58 3

5 8

4 Co-58 3

4 3

5 Fe-59 6

13 17 9

Fe-59 7

10 10 15 Co-60 2

2 4

3 Co-60 3

1 2

4 Zn-65 6

< 7 11 7

Zn-65 6

7 6

10 BY-01 Nb-95 3

3 7

5 BY-06 Nb-95 3

4 4

6 Zr-95 6

6 12 8

Zr-95 6

8 7

11 Cs-134 2

3 4

3 Cs-134 2

2 3

4 Cs-137 2

1 5

3 Cs-137 2

2 2

3 Ba-140 1

166 309 167 Ba-140 115 164 132 215 La-140 52 82 115 75 La-140 54 65 67 112 Mn-54 2

2 2

2 Mn-54 2

2 4

2 Co-58 4

3 2

3 Co-58 3

4 6

4 Fe-59 8

9 8

8 Fe-59 5

8 12 12 Co-60 2

2 2

3 Co-60 3

2 4

3 Zn-65 5

6 5

5 Zn-65 8

7 6

8 BY-04 Nb-95 3

3 4

4 BY-08 Nb-95 3

4 5

4 Zr-95 5

5 5

7 Zr-95 4

6 9

7 Cs-134 2

2 2

2 Cs-134 3

2 4

2 Cs-137 2

2 2

2 Cs-137 2

2 3

3 Ba-140 97 142 162 168 Ba-140 87 140 226 143 La-140 51 67 66 60 La-140 58 97 99 44

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 44 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 12: Quarterly Air Particulate Gamma Isotopic (pCi/m3+/- 2 Sigma) Cont'd Station Nuclide Q1 Q2 Q3 Q4 Station Nuclide Q1 Q2 Q3 Q4 Mn-54

< 4 3

2 3

Mn-54 3

3 3

< 2 Co-58 5

< 4 3

< 3 Co-58

< 4 3

Fe-59 15 11 11 12 Fe-59 10 12 12 10 Co-60 3

3

< 2

< 2 Co-60

< 2

< 2 3

< 2 Zn-65 9

< 7 7

< 7 Zn-65

< 6 9

< 7

< 4 BY-21 Nb-95

< 6 5

< 4

< 4 BY-23 Nb-95

< 4

< 4 5

3 Zr-95 10 9

< 6

< 6 Zr-95

< 8 7

< 6 5

Cs-134

< 4 3

< 2 3

Cs-134 3

2

< 2

< 2 Cs-137 3

3

< 2

< 2 Cs-137 3

< 2

< 2 2

Ba-140 169

< 213 136 174 Ba-140 154 135 178 140 La-140 54

< 73 79 54 La-140 53 99

< 65 36 Mn-54 2

3

< 2 3

Mn-54

< 2 2

3

< 2 Co-58

< 2 5

3 3

Co-58

< 4 3

5

< 4 Fe-59

< 4 13 9

9 Fe-59 12

< 7 13 8

Co-60

< 2

< 2 1

Co-60 3

3 3

< 2 Zn-65 5

< 9 5

< 6 Zn-65

< 6

< 9

< 7 BY-22 Nb-95 3

5

< 4 3

BY-24 Nb-95 3

3 5

< 4 Zr-95 5

9

< 4

< 6 Zr-95 5

5 8

7 Cs-134 2

3 2

< 2 Cs-134

< 2

< 2 3

2 Cs-137 2

3 2

< 2 Cs-137 3

< 2 3

< 2 Ba-140 104

< 205 104 139 Ba-140 118 112 195 118 La-140 41

< 79 55

< 43 La-140 52 79 72

< 76

Annual Radiological Environmental Operating Report J

YEAR: 2024 J

Page 45 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 13: Weekly Air Iodine 1-131 (E-3 pCi/m 3)

Collection BY-21 BY-22 BY-23 BY-24 BY-01 BY-04 BY-06 BY-08 Date 01/02/2024 58 59 59 58 41 41 41 41 01/09/2024 39 33 39 27 68 37

< 42 42 01/16/2024

< 36 30(1) 36 35 51 52 51 51 01/23/2024 23 23

< 23 23 13 13 13 13 01/30/2024 35 36 16 36 43 43 43

< 43 02/06/2024 38 38 38 38 21 21 21 21 02/13/2024

< 49

< 49 21 37 38 38 38 02/20/2024

< 38 38 38 38 36 36 36 17 02/27/2024

< 53 53 22 53

< 42 42 42 42 03/05/2024 58 58 58 58 41 41 41 41 03/12/2024

< 53 53 53 53 24 58 58 58 03/19/2024

< 36 36 36 36 39

< 40

< 40 40 03/26/2024 53 53 53 53 58 58 58 58 04/02/2024

< 28 28 28 28 40 39 19

< 40 04/09/2024

< 54 54 54 22 66 67 67 67 04/16/2024 34 35 35

< 26 58 58 58 58 04/23/2024

< 40

< 40 19 19 19 19 04/29/2024 53 54 54 54

< 48 50 48

< 49 05/07/2024

< 40

< 40 50 50 50 50 05/14/2024 37 37 37 37 39 39 39 39 05/21/2024

< 45 45

< 45

< 45 22 22 22 22 (1)

Refer to Sample Deviation Summary Table 9

Annual Radiological Environmental Operating Report j )'_EA~:_20~4 _l Page 46 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 13: Weekly Air Iodine 1-131 (E-3 pCi/m 3) Cont'd Collection BY-21 BY-22 BY-23 BY-24 BY-01 BY-04 BY-06 BY-08 Date 05/28/2024 52

< 52 52

< 52

< 46 46 46 46 06/04/2024

< 44

< 34 34 35 34 06/11/2024

< 37

< 37 37 18

< 37 37 37 38 06/18/2024

< 50

< 50 50

< 50 51 52 52 52 06/25/2024

< 65

< 34 34 17

< 65 66 66 28 07/02/2024

< 48

< 49

< 48

< 38 38 39 39 07/09/2024

< 38

< 38 38 41

< 45

< 43

< 47 07/16/2024 37

< 25

< 37

< 39

< 48

< 49

< 48 51 07/23/2024

< 48

< 32

< 48

< 43

< 43 07/30/2024

< 37

< 38 38

< 36 36 36 36 08/06/2024

< 48

< 24

< 50 50 51 51 08/13/2024

< 29

< 29 32 32 32

< 23 08/19/2024

< 43

< 42

< 36 36 36 36 08/27/2024

< 26

< 29 29

< 29

< 29 09/03/2024

< 63

< 60

< 62

< 40 39

< 40

< 40 09/10/2024

< 45

< 46

< 23

< 40

< 40 09/17/2024

< 44

< 25 38 38 38 09/24/2024

< 32 32 32 32 31 31 31 31 10/01/2024 21

< 22

< 22 14 21 21 21 10/08/2024

< 43

< 33 33 33 33 10/15/2024

< 39

< 43

< 23

< 23 23 23 10/22/2024 39 39

< 39

< 39 36 36 36 15

Annual Radiological Environmental Operating Report J

YEAR: 2024 J

Page 47 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 13: Weekly Air Iodine 1-131 (E-3 pCi/m 3) Cont'd Collection BY-21 BY-22 BY-23 BY-24 BY-01 BY-04 BY-06 BY-08 Date 10/29/2024

< 37

< 28

< 43

< 43 11/05/2024

< 21 21

< 22

< 21

< 35

< 35 11/12/2024

< 37

< 37 37 37

< 42

< 42 11/19/2024

< 57

< 60

< 60 11/26/2024

< 46 46

< 46

< 22

< 36

< 37

< 37 12/03/2024

< 34

< 29

< 29 12/10/2024

< 50

< 50 51

< 24

< 45

< 45 12/17/2024

< 53

< 54

< 26

< 40

< 41

< 41 12/23/2024

< 49 49

< 49

< 52

< 25

Annual Radiological Environmental Operating Report l YEAR: 2024 [

Page 48 of 74 Company: Constellation l Plant: Byron Clean Enerav Center Units 1 and 2 Table 14: Monthly/Bi-Weekly Milk 1-131 (pCi/L +/- 2 Sigma)

Collection Control Farm Indicator Farm Date BY-26-2 BY-20-1 01/02/2024 0.8 0.8 02/06/2024 0.8 0.8 03/05/2024 0.8 0.8 04/02/2024 0.8 0.8 05/07/2024 0.8 0.9 05/21/2024 0.8 0.7 06/04/2024 0.7 0.8 06/18/2024 0.9 0.9 07/09/2024 0.8 0.8 07/16/2024 0.9 0.9 07/30/2024 0.9 0.8 08/13/2024 0.9 0.8 08/27/2024 0.8 0.7 09/10/2024 0.9 0.9 09/24/2024 0.5 0.6 10/08/2024 0.9 0.9 10/22/2024 0.7 0.8 11/05/2024 0.8 0.9 12/03/2024 0.9 0.8

Annual Radiological Environmental Operating Report I YEA~: 2~24 _I Page 49 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 15: Monthly/Bi-Weekly Milk Gamma Isotopic (pCi/L +/- 2 Sigma)

Station Collection Dates Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 Cs-134 Cs-137 Ba-140 La-140 01/02/2024 7

7 15 9

16 7

11 7

6 30 10 02/06/2024 7

9 17 8

21 8

15 8

7 33 9

03/05/2024 7

6 17 8

18 8

12 6

8 32 9

04/02/2024 8

7 17 10 21

< 7 14 9

8 32 10 05/07/2024 8

7 16 7

21 9

14 8

9 32 9

05/21/2024 8

9 16 8

21 9

14 8

9 26 9

06/04/2024 5

6 18 9

17 7

9 6

8 23 7

06/18/2024 8

8 23 10 22 7

11 9

8 30 9

07/09/2024 9

8 19 8

15 8

13 9

7 32 10 BY-20-1 07/16/2024 7

7 17 9

17 8

12 9

7 27 11 07/30/2024 6

6 16 11 22 8

14 6

9 33 14 08/13/2024 7

6 16 9

15 8

8 28 7

08/27/2024 7

< 7 14 9

14 7

12 8

7 24 7

09/10/2024 8

6 18 12 25 7

12 8

8 24 11 09/24/2024 9

9 18 8

23 9

13 8

9 36 13 10/08/2024 9

10 25 14 21 9

17 11 11 38 12 10/22/2024 6

6 14 6

15 6

10 6

5 20 8

11/05/2024 5

6 10 6

12 5

10 6

5 20 6

12/03/2024 7

8 16 7

17 6

14 9

9 28 8

Annual Radiological Environmental Operating Report

[ YEAR: 2024 [

Page 50 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 15: Monthly/Bi-Weekly Milk Gamma Isotopic (pCi/L +/- 2 Sigma) Cont'd Station Collection Dates Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 Cs-134 Cs-137 Ba-140 La-140 01/02/2024 7

9 18 11 21 9

15 9

7 37 9

02/06/2024 5

8 16 8

21 7

11 6

8 25 9

03/05/2024 9

7 20 12 18 9

14 8

8 28 5

04/02/2024 8

8 14 5

19 8

14 9

9 30 9

05/07/2024 6

5 12 6

11 6

10 6

5 18 4

05/21/2024 6

8 19 8

16 7

11 8

7 27 11 06/04/2024 9

6 18 9

17 9

11 8

8 31 9

06/18/2024 9

7 17 11 16 8

12 7

7 24 7

07/09/2024 8

9 20 9

20 11 14 9

7 42 5

BY-26-2 07/16/2024 7

9 17 8

18 6

13 9

7 27 11 07/30/2024 7

7 18 8

15 7

13 10 9

35 9

08/13/2024 11 10 23 11 23 9

18 10 14 36 10 08/27/2024 5

5 12 7

16 6

10 6

5 19 4

09/10/2024 7

6 16 7

16 8

12 8

8 27 9

09/24/2024 6

6 17 7

15 7

10 7

7 26 10 10/08/2024 9

9 17 12 14 8

15 10 8

36 9

10/22/2024 5

7 16 6

13 7

6 22 8

11/05/2024 6

8 13 8

17 8

12 8

7 26 9

12/03/2024 7

8 18 10 18 8

12 8

7 23 8

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 51 of 74 Company: Constellation __ lPlant: l:!Y_ron Clean Energy Center Units 1 and 2 Table 16: Annual Food Products Gamma Isotopic (pCi/kg Wet+/- 2 Sigma)

Station Collection Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 1-131 Cs-134 Cs-137 Ba-140 La-140 Dates BY-Cabbage 08/12/2024

< 25

< 26

< 48 23 54 25

< 47 42

< 26 22 107

< 27 CONTROL Corn Leaves 08/12/2024 30 27

< 45

< 44 90 36 58 53

< 49 38 167

< 59 BY-QUAD-Cabbage 08/05/2024 18 16

< 42

< 23 39 19 28 20 19 19

< 58

< 26 1

Onions 08/05/2024 21 24 39

< 22

< 40 19 29 24 22 15 59

< 29 BY-QUAD-Onions/Potatoes 08/05/2024 13 12 33 10 36 15

< 22 15 16 13

< 45 16 2

Kale 08/12/2024

< 27 26

< 63 30 57

< 26

< 42 44 30 24

< 112 35 BY-QUAD-Beet 08/05/2024

< 20 22

< 60 25 56 23

< 47 30 28 30 97

< 29 3

Cabbage 08/05/2024 13 16 33

< 20

< 44 14

< 23 19 16 16 61 24 BY-QUAD-Carrot 08/05/2024 13 13 30 12 35 12 22 16 15 14

< 47 11 4

Kohlrabi 08/12/2024 35

< 42 83

< 49 88 37 72 52 43 35 183

< 67

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 52 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 17: Monthly Surface Water Gross Beta and Nickel-63 (pCi/L +/- 2 Sigma)

Station Collection Dates Gr-8 Ni-63 1/2/2024 1/30/2024 6

+/-

2 29 2/6/2024 -

2/28/2024 5

+/-

2 22 3/5/2024 3/26/2024 3

+/-

2 22 4/2/2024 4/29/2024 4

+/-

2 26 5/7/2024 5/28/2024 5

+/-

2 8

6/4/2024 6/25/2024 5

+/-

2 27 BY-12 7/2/2024 7/30/2024 3

+/-

2 16 8/6/2024 8/27/2024 5

+/-

2 19 9/3/2024 9/24/2024 5

+/-

2 23 10/1/2024 10/29/2024 5

+/-

3 20 11/5/2024 11/26/2024 3

+/-

2 25 12/3/2024 12/31/2024 4

+/-

2 21 1/2/2024 1/30/2024 5

+/-

2 28 2/6/2024 2/28/2024 3

22 3/5/2024 3/26/2024 5

+/-

2 25 4/2/2024 4/29/2024 3

+/-

2 28 5/7/2024 5/28/2024 4

+/-

2 8

6/4/2024 6/25/2024 4

+/-

2 27 BY-29 7/2/2024 7/30/2024 4

2 16

+/-

8/6/2024 8/27/2024 4

+/-

2 18 9/3/2024 9/24/2024 4

+/-

2 23 10/1/2024 10/29/2024 4

+/-

3 17 11/5/2024 11/26/2024 3

+/-

2 29 12/3/2024 -

12/31/2024 5

+/-

2 21

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 53 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 18: Monthly Surface Water Gamma Isotopic (pCi/L +/- 2 Sigma)

Station Collection Dates Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 1-131 Cs-134 Cs-137 Ba-140 La-140 01/02/2024 01/30/2024 2

2 4

2 3

6 2

2 13 4

02/06/2024 02/28/2024 6

6 10

< 7 10 8

11 14 5

6 39 11 03/05/2024 03/26/2024 4

4 11

< 6 13 6

10 14 6

6 35 13 04/02/2024 04/29/2024 2

2 5

2 4

9 2

2 18 6

05/07/2024 05/28/2024 2

2 5

2 3

< 13

< 2 2

20

< 7 06/04/2024 06/25/2024 1

1 3

1 2

13 1

1 17 6

BY-12 07/02/2024 07/30/2024 1

1 4

2 3

1 3

6 1

1 11 4

08/06/2024 08/27/2024 5

5 12 6

10 6

10 15 5

5 34 8

09/03/2024 09/24/2024 3

3 6

3 5

8 3

3 18 6

10/01/2024 10/29/2024 2

2 6

3 5

13 2

2 25 8

11/05/2024 11/26/2024 1

1 3

6 1

1 11 4

12/03/2024 12/31/2024 2

2 5

2 4

2 3

9 2

2 17 7

Annual Radiological Environmental Operating Report

] YEAR: 2024. [

Page 54 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 18: Monthly Surface Water Gamma Isotopic (pCi/L +/- 2 Sigma) Cont'd Station Collection Dates Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 1-131 Cs-134 Cs-137 Ba-140 La-140 01/02/2024 01/30/2024 1

2 3

6 1

2 12 4

02/06/2024 02/28/2024 5

5 12 4

12 4

10 12 6

5 36 9

03/05/2024 03/26/2024 5

5 10 4

11 6

9 14 5

5 27 9

04/02/2024 04/29/2024 3

3 7

3 6

3 5

11 3

3 22 8

05/07/2024 05/28/2024 2

2 5

2 4

10 2

2 18 6

06/04/2024 06/25/2024 1

1 3

1 2

14 1

1 19 6

BY-29 07/02/2024 07/30/2024 2

2 4

7 2

2 14 5

08/06/2024 08/27/2024 4

4 7

5 8

11 5

4 24 11 09/03/2024 09/24/2024 3

3 7

4 6

3 6

9 4

3 22 6

10/01/2024 10/29/2024 2

2 5

2 4

11 2

2 19 6

11/05/2024 11/26/2024 2

2 5

2 4

2 3

9 2

2 15 6

12/21/2024 12/31/2024 5

4 8

5 12 5

8 11 6

4 27 10

Annual Radiological Environmental Operating Report I _ '!'_EAR:_2024 _J Page 55 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 19: Quarterly Surface Water Tritium (pCi/L +/- 2 Sigma)

Station Collection Dates H-3 01/02/2024 03/26/2024 392

+/-

130 BY-12 04/02/2024 06/25/2024 199 07/02/2024 09/24/2024 3570

+/-

423 07/02/2024 09/24/2024 3790

+/-

443 10/01/2024 12/31/2024 179 01/02/2024 03/26/2024 190 04/02/2024 06/25/2024 199 BY-29 07/02/2024 09/24/2024 183 10/01/2024 12/31/2024 178

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 56 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 20: Quarterly Ground Water Tritium (pCi/L+/- 2 Sigma)

Collection BY-14-1 BY-18-1 BY-32 BY-35 BY-37 BY-38 Date 01/09/2024 191 193 185 185 184 187 04/09/2024 187 191 189 194 192 191 07/09/2024 189 190 190 190 187 185 10/08/2024 183 185 182 182 183 189

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 57 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 21: Quarterly Ground Water Gamma Isotopic (pCi/L +/- 2 Sigma)

Station Collection Dates Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 1-131 Cs-134 Cs-137 Ba-140 La-140 01/09/2024 01/09/2024 5

5 10 5

11 7

9 6

5 6

18 8

04/09/2024 04/09/2024 7

8 16 8

16 8

12 12 9

7 33 13 BY-14-1 07/09/2024 07/09/2024 4

5 11 6

11 6

8 8

6 5

24 6

10/08/2024 10/08/2024 9

8 14 9

15 10 15 11 11 9

34 14 01/09/2024 01/09/2024 8

5 16 11 18 8

14 9

8 9

25 8

04/09/2024 04/09/2024 7

4 11 6

12 5

9 10 6

5 22 8

BY-18-1 07/09/2024 07/09/2024 7

7 14 8

17 6

13 13 8

8 32 13 10/08/2024 10/08/2024 7

6 12 8

16 9

12 9

7 6

27 11 01/09/2024 01/09/2024 5

5 9

5 8

6 9

5 5

6 17 6

04/09/2024 04/09/2024 7

4 12 8

10 6

8 9

7 7

35 7

BY-32 07/09/2024 07/09/2024 7

7 19 8

14 8

9 10 7

7 35 12 10/08/2024 10/08/2024 8

8 17 7

18 11 14 9

10 9

31 13

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 58 of 74 Compariy: ConstellatioJl~ ~ ~

Plant: Byron Clean Energy Center Units 1 and 2 Table 21: Quarterly Ground Water Gamma Isotopic (pCi/L +/- 2 Sigma) Cont'd.

Station Collection Dates Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 1-131 Cs-134 Cs-137 Ba-140 La-140 01/09/2024 01/09/2024 5

5 12 6

10 5

9 6

5 5

18 8

04/09/2024 04/09/2024 6

7 13 8

12 7

13 10 6

6 32 8

BY-35 07/09/2024 07/09/2024 8

7 9

7 14 8

9 10 7

7 27 14 10/08/2024 10/08/2024 8

9 17 11 19 13 16 11 11 10 40 13 01/09/2024 01/09/2024 4

5 9

5 11 6

8 6

5 5

21 6

04/09/2024 04/09/2024 6

10 16 8

15 8

11 10 9

7 27 12 BY-37 07/09/2024 07/09/2024 5

5 10 5

9 5

8 8

5 5

24 7

10/08/2024 10/08/2024 9

8 18 12 19 14 18 12 10 8

35 12 01/09/2024 01/09/2024 5

4 10 5

11 5

8 6

5 4

18 6

04/09/2024 04/09/2024 6

6 13 6

12 6

10 10 7

6 24 7

BY-38 07/09/2024 07/09/2024 6

5 11 5

11 5

10 8

7 6

21 8

10/08/2024 10/08/2024 8

8 13 8

16 10 13 10 8

9 26 11

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 59 of 74 Company: Constellation I Plant: B_yron Clean Energy Center Units 1 and 2 Table 22: Semi-Annual Fish Nickel-63 and Gamma Isotopic (pCi/kg Wet+/- 2 Sigma)

Station Collection Ni-63 Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 Cs-134 Cs-137 Ba-140 La-140 Dates Bigmouth 06/04/2024 67 42 37 91 53 100 46 83 42 37 205 68 Buffalo River 06/04/2024 88 45 43 84 43 101 41 86 49 48 258 87 Carpsucker BY-29 Common Carp 09/24/2024 152 76 85 221 88 204 90 167 73 68 761 225 River Carpsucker 09/24/2024 123 56 73 167 80 112 86 123 67 67 725 197 Common 06/04/2024 69 44 53 117 58 Carp 137 59 95 62 47 274 75 River 06/04/2024 79 64 80 124 71 165 69 92 77 68 346 114 Carpsucker BY-31 Bigmouth Buffalo 09/24/2024 134 66 56 178 68 134 77 147 83 68 600 220 River 09/24/2024 174 45 57 125 50 Carpsucker 118 55 99 51 36 456 174

Annual Radiological Environmental Operating Report J _YE~R: 20_24 J Page 60 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 23: Semi-Annual Shoreline Sediment Nickel-63 and Gamma Isotopic (pCi/kg Dry+/- 2 Sigma)

Station Collection Ni-63 Mn-54 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 Cs-134 Cs-137 Ba-140 La-140 Dates 05/07/2024 221 103 86 193

< 89

< 213 101 143 98 119 373 136 BY-12 10/15/2024 239

< 74

< 63 189 77 192 99 137 96 104 341 149 05/07/2024 233 52 51 114

< 47 122 56 79 51 61

< 248

< 60 BY-34 10/15/2024 161 37 36 81 41

< 93 47

< 74

< 42

< 45 176

< 67

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 61 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Cross Check lntercomparison Program Participation in cross check intercomparison studies is mandatory for laboratories performing analyses of REMP samples satisfying the requirements in the Offsite Site Dose Calculation Manual. lntercomparison studies provide a consistent and effective means to evaluate the accuracy and precision of analyses performed by a laboratory.

Study results should fall within specified control limits and results that fall outside the control limits are investigated and corrected.

Teledyne Brown Engineering Inc. (TBE) participated in the following proficiency testing studies provided by Eckert Ziegler Analytics, DOE's Mixed Analyte Performance Evaluation Program (MAPEP), and/or Environmental Resource Associates (ERA) in 2024. The Laboratory's intercomparison program results for 2024 are summarized below.

For the TBE laboratory, 152 out of 167 analyses performed met the specified acceptance criteria. Fifteen analyses did not meet the specified acceptance criteria and were addressed through the TBE Corrective Action Program. A summary is found below:

I.

NCR 24-02: ERA March MRAD-40 study with Air Particulate AM-241 evaluated as "Not Acceptable." TBE reported 38.8 pCi/filter and the known value returned at 55.0 pCi/filter (range 39.3-73.3). The root cause investigation determined that the sample was not logged into the system correctly and therefore not prepared with the required tracer. To correct and prevent recurrence, personnel involved are to utilize a template to ensure all analyses are logged as required and the QA Manager will perform sample log review as a back up to ensure accuracy. Acceptable results returned in a later sample study, supporting effectiveness of corrective action.

II.

NCR 24-03: ERA March MRAD-40 air particulate study GR-B evaluated as "Not Acceptable." TBE reported 42.1 pCi/filter and the known value returned at 22.2 pCi/filter (range 13.5-33.5). The root cause investigation determined that alpha-to-beta crosstalk was more significant than normal which caused the beta activity to report falsely high data. To correct and prevent recurrence, personnel involved are to adjust the alpha-to-beta crosstalk via correction calculation measures when high alpha activities are observed. Acceptable results returned in a later sample study, supporting effectiveness of corrective action.

111.

NCR 24-05: ERA April RAD-137 water study GR-A evaluated as "Not Acceptable."

TBE reported 35.2 pCi/L and the known value returned at 52.6 pCi/L (range 39.6-65.6). The root cause investigation determined that the provided samples contained a solids content that was significantly higher than the typical client samples tested by the laboratory. A set aliquot volume for prior ERA samples was used and not adjusted to account for the sudden increase in solid content. To correct and prevent recurrence, new sample types were ordered from ERA that used Am-241 to better reflect client sample testing and acceptable results were achieved. Acceptable results returned in a later sample study, supporting effectiveness of corrective action.

IV.

NCR 24-06: E&Z Analytics March E14092 air particulate study Co-60 evaluated as

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 62 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 "Not Acceptable." TBE reported 168 pCi and the known value returned at 126 pCi.

Additionally, March E14093 soil Ce-141 evaluated as "Not Acceptable." TBE reported 0.106pCi/g and the known value returned at 0.071pCi/g. The root cause investigation was unable to determine any anomaly thus no proposed corrective action. No recurrence has occurred.

V.

CAR 24-02 (CAR 23-31): MAPEP February 24-MaS50 soil study Fe-55 evaluated as "Not Acceptable." TBE reported 297 Bg/Kg and the known value returned at 650 Bg/Kb (range 455-845). The root cause investigation suspects that the current analytical procedure is not sufficient to add the interferences added to the sample by MAPEP.

This investigation is still ongoing (See NCR 24-16) as the suggested corrective action did not provide desired results.

VI.

NCR 24-08: MAPEP February 24-MaS50 soil study Ni-63 evaluated as "Not Acceptable." TBE reported 1070 Bg/Kg and the known value returned at 1530 Bg/Kb (range 1071-1989). The root cause investigation suspected that the sample contained added interferences that are not typically seen in client samples. All QC efforts associated with the sample were acceptable and no anomalies found, even after reanalysis. To correct and prevent recurrence, samples suspected of additional interferences will include the addition of Ni-59 tracer to determine yield results when calculating results. TBE analytical procedure TBE-2013 was updated to include this change.

VII.

NCR 24-09: MAPEP February 24-MaSU50 urine study Zn-65 evaluated as "Not Acceptable." The root cause investigation determined that the sample was spiked lower than TBE's typical detection limit and client requirements. The report was revised by MAPEP indicating "Not Evaluated," resulting in this nuciide to not be considered a failure.

VIII.

NCR 24-10: MAPEP February 24-MaW50 water study Tc-99 evaluated as "Not Acceptable." TBE reported 9.95Bg/L and the known value returned 7.47Bg/L (range 5.23-9. 71 ). The root cause investigation suspects Thorium interference that was not removed during the column separation process of the analytical procedure; however, it cannot be confirmed as all QC efforts associated with the sample were acceptable and with no anomalies found. To potentially correct and prevent recurrence, an additional rinse step was added to the procedure. Acceptable results returned in a later sample study, supporting effectiveness of corrective action.

IX.

NCR 24-11: MAPEP February 24-RdV50 vegetation study Sr-90 evaluated as "Not Acceptable." TBE reported 0.276Bg/sample and the known value returned 0.529Bg/sample (range 0.370-0.688). The root cause investigation determined a laboratory accident resulting in a spilled (loss) of sample. No corrective action was performed as the cause was an unintentional sample spill.

X.

NCR 24-14: ERA September MRAD-41 air particulate study U-234/238 evaluated as "Not Acceptable." TBE reported 14.0/14.2 pCi/filter and the known value returned at

31. 1/30.9 pCi/filter (range 23.1-36.9). The root cause investigation determined that the laboratory technician placed double the amount of tracer in the sample by error. To correct and prevent recurrence, samples that have been digested/leached with carrier/tracer added will have a label placed over the cap indicating it has already been

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 63 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 added. Additionally, the beaker that aliquot is put in should have markings to indicate carrier/tracer has already been added to the sample.

XI.

NCR 24-15: ERA September MRAD-41 water study Fe-55 evaluated as "Not Acceptable." TBE reported 615 pCi/L and the known value returned at 1230 pCi/L (range 723-1790). The root cause is still under investigation.

XI I.

NCR 24-16: MAPEP August 24-MaS50 soil study Fe-55 evaluated as "Not Acceptable." TBE did not report a value and the known value returned 780Bg/Kg (range 546-1014). The root cause is still under investigation.

XIII.

NCR 24-17: MAPEP August 24-RdV51 vegetation study Sr-90 evaluated as "Not Acceptable." TBE reported 0.95Bg/sample and the known value returned 2.39Bg/sample (range 1.67-3.11). The root cause is still under investigation.

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 64 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 24: Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services Identification TBE Known Ratio of TBE Evaluation Month/Year Number Matrix Nuclide Units Reported Value (a) to Analytics (b)

Value Result March 2024 E14089 Milk Sr-89 pCi/L 79.6 78.2 1.02 A

Sr-90 pCi/L 12.6 11.9 1.06 A

E14090 Milk Ce-141 pCi/L 75.6 85.0 0.89 A

Co-58 pCi/L

-0 069 Not Measured Co-60 pCi/L 139 158 0.88 A

Cr-51 pCi/L 212 230 0.92 A

Cs-134 pCi/L 167 198 0.84 A

Cs-137 pCi/L 158 171 0.93 A

Fe-59 pCi/L 81.1 86.5 0.94 A

1-131 pCi/L 80.9 90.8 0.89 A

Mn-54 pCi/L 173 183 0.95 A

Zn-65 pCi/L 165 176 0.93 A

E14091 Charcoal 1-131 pCi 90.1 90.3 1.00 A

E14092 AP Ce-141 pCi 68.1 67.5 1.01 A

Co-58 pCi 1.73 Not Measured Co-60 pCi 168 126 1.34 Nl1I Cr-51 pCi 182 183 0.99 A

Cs-134 pCi 157 157 1.00 A

Cs-137 pCi 132 136.0 0.97 A

Fe-59 pCi 70.3 68.6 1.02 A

Mn-54 pCi 144 145 0.99 A

Zn-65 pCi 125 140 0.89 A

E14093 Soil Ce-141 pCi/g 0106 0.071 1.48 NI1I Co-58 pCi/g

-0 005 Not Measured Co-60 pCi/g 0.121 0.133 0.91 A

Cr-51 pCi/g 0.198 0.194 1 02 A

Cs-134 pCi/g 0.206 0.166 1.24 w

Cs-137 pCi/g 0.207 0.209 0.99 A

Fe-59 pCi/g 0.063 0.073 0.87 A

Mn-54 pCi/g 0.140 0.153 0.91 A

Zn-65 pCi/g 0.149 0.148 1.01 A

E14094 AP Sr-89 pCi 83.9 90.6 0.93 A

Sr-90 pCi 11.7 13.8 0.85 A

(a) The Analytics known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) Analytics evaluation based on TBE internal QC limits A= Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within 0.70-0.80 or 1.20-1 30 N = Not Acceptable - reported result falls outside the ratio limits of< 0.70 and> 1.30

( 1) See NCR 24-06

Annual Radiological Environmental Operating Report l YEAR: 2024 l Page 65 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 Table 24: Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services Identification TBE Reported Known Ratio of TBE to Evaluation Month/Year Matrix Nuclide Units Value Number Value (a)

Analytics Result (b)

September 2024 E14095 Milk Sr-89 pCi/L 88.0 92.3 0.95 A

Sr-90 pCi/L 124 15.2 0.82 A

E14096 Milk Ce-141 pCi/L 124 124 1.00 A

Co-58 pCi/L 154 150 1 03 A

Co-60 pCi/L 232 236 0.98 A

Cr-51 pCi/L 284 274 1 04 A

Cs-134 pCi/L 180.0 187 0.96 A

Cs-137 pCi/L 126 127 0.99 A

Fe-59 pCi/L 127.0 113 1.12 A

1-131 pCi/L 85.3 89.0 0.96 A

Mn-54 pCi/L 162 162 1.00 A

Zn-65 pCi/L 294 275 1 07 A

E14097 Charcoal 1-131 pCi 98.8 92.6 1 07 A

E14098 AP Ce-141 pCi 82.0 76.7 1 07 A

Co-58 pCi 91.0 92.6 0.98 A

Co-60 pCi 180 146 1.23 w

Cr-51 pCi 208 170 1.22 w

Cs-134 pCi 116 116 1.00 A

Cs-137 pCi 83.1 78.9 1 05 A

Fe-59 pCi 75.6 70.2 1.08 A

Mn-54 pCi 101 100 1 01 A

Zn-65 pCi 167 170 0.98 A

E14099 Soil Ce-141 pCi/g 0.224 0.222 1 01 A

Co-58 pCi/g 0.249 0.268 0.93 A

Co-60 pCi/g 0420 0423 0.99 A

Cr-51 pCi/g 0492 0492 1.00 A

Cs-134 pCi/g 0.278 0.336 0.83 A

Cs-137 pCi/g 0.276 0.295 0.94 A

Fe-59 pCi/g 0.233 0.204 1.14 A

Mn-54 pCi/g 0.279 0.290 0.96 A

Zn-65 pCi/g 0.538 0494 1 09 A

E14100 AP Sr-89 pCi 79.8 82.7 0.96 A

Sr-90 pCi 12.0 13.6 0.88 A

Gr-A E14197 Liquid (Am241) pCi/L 47.6 50.1 0.95 A

Gr-B (Cs137) pCi/L 248 270 0.92 A

(a) The Analytics known value Is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) Analytics evaluation based on TBE internal QC limits A= Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within 0.70-0.80 or 1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of< 0.70 and> 1.30

( 1) See NCR 24-06

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 66 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 25: DOE's Mixed Analyte Performance Evaluation Program (MAPEP)

Teledyne Brown Engineering Environmental Services Identification TBE Known Acceptance Evaluation Month/Year Number Matrix Nuclide Units Reported Value Range (b)

Value (a)

February 2024 24-MaS50 Soii Fe-55 Bq/kg 297 650 455 - 845 N(3)

Ni-63 Bq/kg 1070 1530 1071 - 1989 N(4)

Tc-99 Bq/kg 325 336 235 - 437 A

Th-228 Bq/kg 34.6 48.8 34.2 - 63.4 w

Th-230 Bq/kg 49.7 54.0 38.0 - 70.0 A

Th-232 Bq/kg 36.4 45.1 31.6 - 58.6 A

24-MaSU50 Urine Cs-134 Bq/L 1.12 1.36 0.95-1.77 A

Cs-137 Bq/L 2.00 2.23 1.56 - 2.90 A

Co-57 Bq/L 1 06 1.26 0.88 - 1.64 A

Co-60 Bq/L 2.26 2.38 1.67-309 A

K-40 Bq/L

-1.80 NR Mn-54 Bq/L 1.44 1.51 1 06 - 1. 96 A

U-234 Bq/L 0.00101 (1)

A U-238 Bq/L 0.00228 (1)

A Zn-65 Bq/L

-0.42 0.84 0.59 - 1.09 NE(5l 24-MaW50 Water Ni-63 Bq/L 0.338 0.80 (2)

A Tc-99 Bq/L 9.95 7.47 5.23 - 9.71 N(6) 24-RdV50 Vegetation Cs-134 Bq/sample 2.80 3.67 2.57 - 4.77 w

Cs-137 Bq/sample 2.21 2.57 1.80 - 3.34 A

Co-57 Bq/sample 2.23 2.53 1.77 - 3.29 A

Co-60 Bq/sample 2.42 2.96 207-3.85 A

Mn-54 Bq/sample 0.033 (1)

A Sr-90 Bq/sample 0.276 0.529 0.370 - 0.688 N(7)

Zn-65 Bq/sample 6.83 8 02 5.61-10.43 A

(a) The MA PEP known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) OOE/MAPEP evaluation.*

A = Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within O 70-0. 80 or 1. 20-1. 30 N = Not Acceptable - reported result falls outside the ratio limits of< 0. 70 and> 1.30 (1) False positive test (2) Sensitivity evaluation (3) See CAR 23 Analyte not on XCHK list (4) See NCR 24-08 (5) Not Evaluated (6) See NCR 24-10 (7) See NCR 24-11 (8) Not Reported (9) See NCR 24-16 (10) See NCR 24-17

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 67 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 25: DOE's Mixed Analyte Performance Evaluation Program (MAPEP)

Teledlne Brown Engineering Environmental Services Identification TSE Known Acceptance Evaluation Month/Year Number Matrix Nuclide Units Reported Value Range (b)

Value (a)

August 2024 24-MaS51 Soil Fe-55 Sq/kg (8) 780 546 - 1014 N(9) 1140.0 Ni-63 Sq/kg 0

1450.00 1015-1885 w

Tc-99 Sq/kg 155.00 171.00 120 - 222 A

Th-228 Sq/kg 38.00 43.30 30.3 - 56.3 A

Th-23O Sq/kg 46.10 44.00 30.8 - 57.2 A

Th-232 Sq/kg 38.90 42.60 29.8 - 55.4 A

24-MaW51 Water Ni-63 Sq/L 0.60 (1)

A Tc-99 Sq/L 11.90 11.20 7.8 - 14.6 A

24-RdV51 Vegetation Cs-134 Sq/sample 3.12 2.89 2.02 - 3.76 A

Cs-137 Sq/sample 2.18 1.91 1.34 - 2.48 A

Co-57 Sq/sample 0.00 (1)

A Co-6O Sq/sample 2.24 2.01 1.41 -2.61 A

Mn-54 Sq/sample 3.76 3.53 2.47 - 4.59 A

Sr-9O Sq/sample 0.95 2.39 1.67 - 3.11 N(10)

Zn-65 Sq/sample 10.30 9.13 6.39 - 11.87 A

(a) The MAPEP known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) DOEIMAPEP evaluation:

A = Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within 0.70-0.80 or 1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of< 0. 70 and> 1.30 (1) False positive test (2) Sensitivity evaluation (3) See CAR 23-31 -Analyte not on XCHK list (4) See NCR 24-08 (5) Not Evaluated (6) See NCR 24-10 (7) See NCR 24-11 (8) Not Reported (9) See NCR 24-16 (10) See NCR 24-17

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 68 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 Table 26: ERA Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services Identification TBE Known Acceptance Evaluation Month/Year Number Matrix Nuclide Units Reported Value (aJ Limits (bi Value March 2024 MRAD-40 Water Am-241 pCi/L 101 139 954 - 178 A

Fe-55 pCi/L 2185 2480 1460- 3610 A

Pu-238 pCi/L 62.0 704 42.3 - 91.2 A

Pu-239 pCi/L 61.2 76.5 47.3 - 94.3 A

Soil Am-241 pCi/kg NR 1880 1020 - 2660 Pu-238 pCi/kg 667 512 255 - 778 A

Pu-239 pCi/kg 562 545 297 - 784 A

Sr-90 pCi/kg 4050 3630 1130 - 5650 A

U-234 pCi/kg 3040 4360 2040-5710 A

U-238 pCi/kg 3270 4320 2370 - 5800 A

AP Am-241 pCi/filter 38.8 55.0 39.3 - 73.3 N(11 Fe-55 pCi/filter 387 386 141 - 616 A

Pu-238 pCi/filter 45.9 41.1 31.0 - 50.5 A

Pu-239 pCi/filter 54.9 56.1 41.9-67.7 A

U-234 pCi/filter 11.1 11.6 8.60 - 13.6 A

U-238 pCi/filter 12.8 11.5 8.68 - 13.7 A

GR-A pCi/filter 116 95.9 50.1 - 158 A

GR-B pCi/filter 42.1 22.2 13.5-33.5 N(2J April 2024 RAD-137 Water Ba-133 pCi/L 62.8 65.9 50.1 - 817 A

Cs-134 pCi/L 51.0 57.8 42.8 - 72.8 A

Cs-137 pCi/L 153 186 149 - 223 A

Co-60 pCi/L 92.1 98.8 79.7-118 A

Zn-65 pCi/L 208 240 188 - 292 A

GR-A pCi/L 35.2 52.6 39.6 - 65.6 Nl3J GR-B pCi/L 49 46.5 33.9 - 59.1 A

U-Nat pCi/L 56.0 59.3 52.8-65.8 A

H-3 pCi/L 19,000 21,300 18,200 - 24,400 A

Sr-89 pCi/L 48.9 52.2 37.8 - 66.6 A

Sr-90 pCi/L 32.6 37.6 32.0 - 43.2 A

1-131 pCi/L 21.8 25.1 21.7 - 28.5 A

(a) The ERA known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) ERA evaluation A = Acceptable - Reported value falls within the Acceptance Limits N = Not Acceptable - Reported value falls outside of the Acceptance Limits (1) See NCR 24-02 (2) See NCR 24-03 (3) See NCR 24-05 (4) See NCR 24-15 (5) See NCR 24-14

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 69 of 74 Company: Constellation I Plant: Byron Clean Enerav Center Units 1 and 2 Table 26: ERA Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services Identification TBE Known Acceptance Month/Year Matrix Nuclide Units Reported Evaluation (bJ Number Value Value (aJ Limits September 2024 MRAD-41 Water Am-241 pCi/L 108.0 117.0 80.3 - 150 A

Fe-55 pCi/L 615 1230 723 - 1790 N<4J Pu-238 pCi/L 99 103 61.9-133 A

Pu-239 pCi/L 123 133 82.3-164 A

Soil Am-241 pCi/kg 1320 1110 599-1570 A

Pu-238 pCi/kg 1380 1860 928 - 2830 A

Pu-239 pCi/kg 796 1030 561 - 1480 A

Sr-90 pCi/kg 3240 4730 1470 - 7370 A

U-234 pCi/kg 2540 2860 1340 - 3750 A

U-238 pCi/kg 2390 2840 1560 - 3810 A

AP Am-241 pCi/filter 27.0 29.1 20.8 - 38.8 A

Fe-55 pCi/filter 644 800 292 - 1280 A

Pu-238 pCi/filter 22.3 21.5 16.2 - 26.4 A

Pu-239 pCi/filter 30.6 32.4 24.2 - 39.1 A

U-234 pCi/filter 14.0 31.1 23.1 - 36.4 N<SJ U-238 pCi/filter 14.2 30.9 23.3 - 36.9 N<sJ GR-A pCi/filter 80.0 72.4 37.8-119 A

GR-B pCi/filter 57.5 47.9 29.0 - 72.4 A

October 2024 RAD-139 Water Ba-133 pCi/L 30.3 27.4 15.5 - 39.3 A

Cs-134 pCi/L 73.3 80.2 63.0 - 97.4 A

Cs-137 pCi/L 46.6 46.3 23.3 - 69.3 A

Co-60 pCi/L 44.2 45.3 31.6 - 59.0 A

Zn-65 pCi/L 104 114.0 75.0- 153 A

GR-A pCi/L 47.6 51.7 38.9 - 64.5 A

GR-B pCi/L 44.2 48.1 35.2 - 61.0 A

U-Nat pCi/L 28.3 26.90 23.6 - 30.2 A

H-3 pCi/L 4,690 5,320 3870 - 6770 A

Sr-89 pCi/L 57.5 44.2 30.6 - 57.8 A

Sr-90 pCi/L 37.3 35.6 30.2-41.0 A

1-131 pCi/L 28.3 26.3 22.7 -29.9 A

(a) The ERA known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation.

(b) ERA evaluation:

A = Acceptable - Reported value falls within the Acceptance Limits N = Not Acceptable - Reported value falls outside of the Acceptance Limits (1) See NCR 24-02 (2) See NCR 24-03 (3) See NCR 24-05 (4) See NCR 24-15 (5) See NCR 24-14

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 70 of 74 Company: Constellation J Plant: Byron Clean Energy Center Units 1 and 2 : Environmental Direct Radiation Dosimetry Results Ba+MDDa Quarterly Normalized Quarterly Monitoring Data, Ma Monitoring

Baseline, Location Bo (mrGm)

(rnrem)

(mrem) 1 2

BY-01 14.6 21.1 16.2 15.2 BY-04 17.8 24.3 18.1 16.8 BY-06 14.6 21.1 15.2 12.9 BY-08 14.4 20.9 13.6 14.8 BY-101-1 12.7 19.2 11.2 12.3 BY-101-2 12.8 19.3 10.6 10.9 BY-102-1 19.1 25.6 19.3 16.6 BY-102-2 19.7 26.2 16.5 20.6 BY-103-1 17.8 24.3 14.7 17 BY-103-2 18.7 25.2 18.1 16.1 BY-103-3 17.4 23.9 17.1 15.2 BY-104-1 19.2 25.7 15.8 19.6 BY-104-2 19.4 25.9 17.6 17.7 BY-104-3 16.7 23.2 14.4 13 BY-105-1 19.2 25.7 16.5 18.6 BY-105-2 19.7 26.2 16.4 19.4 BY-106-1 18.8 25.3 17.7 17.7 BY-106-2 18 24.5 17.7 18.7 BY-107-1 20.3 26.8 17 19.2 BY-107-2 20.5 27 20 19.9 MDDo = Quarterly Minimum Differential Dose= 6.5 mrem MDDA = Annual Minimum Differential Dose= 19.4 mrem 3

15.4 18.2 14.2 15.2 11.5 13.4 19.3 20.5 17.7 18.6 17.9 19.7 19.7 17.2 18.8 20.8 18.4 18.5 19.4 22 ND = Not Detected, where Mo :5 (Bo+MDDo) or MA :5 (BA+MDDA) 4 13.7 17.9 14.6 13.8 12.9 10.8 19.7 21.2 17.5 19.2 17 18.3 18.6 15.5 20.1 19.5 17.1 18.2 18.9 20.1 Bo = Quarterly Normalized Mean Background for a monitoring location (mrem)

BA= Annual Normalized Mean Background for a monitoring location (mrem)

MA= Normalized Annual Dose (mrem)

Quarterly Facility Dos8, Fa=Ma-Ba (mrem, or "ND" if Fo S MDDo) 1 2

3 4

ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND Annual

Baseline, BA (mrem) 58.4 71.3 58.5 57.5 50.7 51.1 76.4 78.6 71.2 74.9 69.5 76.8 77.6 66.8 77 78.9 75.1 72.1 81 81.9 BA+

MDDA (mrem) 77.8 90.7 77.9 76.9 70.1 70.5 95.8 98 90.6 94.3 88.9 96.2 97 86.2 96.4 98.3 94.5 91.5 100.4 101.3 Annual Facility

Dose, Annual FA=MA-BA Monitoring (mrem, or Data, MA "ND" if (mrem)

FAS MDDA) 60.5 ND 71 ND 56.9 ND 57.4 ND 47.9 ND 45.7 ND 74.9 ND 78.8 ND 66.9 ND 72 ND 67.2 ND 73.4 ND 73.6 ND 60.1 ND 74 ND 76.1 ND 70.9 ND 73.1 ND 74.5 ND 82 ND

Annual Radiological Environmental Operating Repoit -~ l YEAR: 2024 I

Page 71 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Environmental Direct Radiation Dosimetry Results Cont'd Ba+

MDDo Quarterly Normalized Quarterly Monitoring Data, Mo Monitoring

Baseline, Location Ba (mrem)

(mrem)

(mrem) 1 2

3 BY-107-3 16.6 23.1 15.1 14.6 17.1 BY-108-1 19 25.5 19.4 19.4 20.7 BY-108-2 17.3 23.8 15.1 15.7 17.2 BY-109-1 17.6 24.1 15.8 16.2 18.9 BY-109-2 17.7 24.2 15.2 16.1 16.5 BY-110-1 16.3 22.8 15.3 16.3 16 BY-110-2 17.3 23.8 15.5 16.7 17.9 BY-111-3 18.9 25.4 16.9 18.4 20.7 BY-111-4 18.1 24.6 15.7 17.1 18 BY-112-3 18 24.5 17.4 14.3 18.7 BY-112-4 18 24.5 17.4 16.5 19.8 BY-113-1 18.5 25 16.1 17.2 18.6 BY-113-2 15.5 22 12.5 12.7 15.7 BY-114-1 14.5 21 15.1 11 15 BY-114-2 17.3 23.8 15.9 14.6 17.7 BY-115-1 18 24.5 16.6 15.9 19.1 BY-115-2 16.7 23.2 14.2 15.7 16.4 BY-116-1 15.9 22.4 15.2 14.7 16.8 BY-116-2 15.8 22.3 15.9 16.1 16 MDDo = Quarterly Minimum Differential Dose= 6.5 mrem MDDA = Annual Minimum Differential Dose= 19.4 mrem ND= Not Detected, where Mo :5 (Bo+MDDo) or MA :5 (BA+MDDA) 4 16.7 17.3 18.1 17.3 17.9 16.2 18.1 18 16.6 17.7 17.8 18.7 14.9 15.5 17.2 18.1 16.2 16.1 16.2 Bo= Quarterly Normalized Mean Background for a monitoring location (mrem)

BA= Annual Normalized Mean Background for a monitoring location (mrem)

MA= Normalized Annual Dose (mrem)

Quarterly Facility Dose, Annual

Baseline, Fa=Ma-Ba BA (mrem)

(mrem, or "ND" if Fa :5 MD Do) 1 2

3 4

ND ND ND ND 66.5 ND ND ND ND 76.1 ND ND ND ND 69 ND ND ND ND 70.3 ND ND ND ND 70.6 ND ND ND ND 65.4 ND ND ND ND 69.4 ND ND ND ND 75.7 ND ND ND ND 72.6 ND ND ND ND 71.9 ND ND ND ND 72.1 ND ND ND ND 74.1 ND ND ND ND 62.2 ND ND ND ND 58.1 ND ND ND ND 69.1 ND ND ND ND 71.9 ND ND ND ND 67 ND ND ND ND 63.5 ND ND ND ND 63.1 BA+

MDDA (mrem) 85.9 95.5 88.4 89.7 90 84.8 88.8 95.1 92 91.3 91.5 93.5 81.6 77.5 88.5 91.3 86.4 82.9 82.5 Annual Facility

Dose, Annual FA=MA-BA Monitoring (mrem, Data, MA or"ND" (mrem) if FA :5 MDDA) 63.5 ND 76.8 ND 66.1 ND 68.2 ND 65.7 ND 63.8 ND 68.2 ND 74 ND 67.4 ND 68.1 ND 71.5 ND 70.6 ND 55.8 ND 56.6 ND 65.4 ND 69.7 ND 62.5 ND 62.8 ND 64.2 ND

Annual Radiological Environmental Operating Report I

YEAR: 2024 I

Page 72 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Environmental Direct Radiation Dosimetry Results Cont'd Bu+ MDDu Quarterly Normalized Quarterly Monitoring Data, Mu Monitoring

Baseline, Location Bu (mrem)

(mrem)

(mrem) 1 2

BY-116-3 16.4 22.9 15 14.6 BY-201-3 17.8 24.3 19.4 15.5 BY-201-4 19.2 25.7 17.6 16.5 BY-202-1 17.6 24.1 17.6 14.2 BY-202-2 19.9 26.4 18.8 18.4 BY-203-1 14.5 21 13.7 10.3 BY-203-2 16.8 23.3 16.9 14.7 BY-204-1 15.6 22.1 13.9 13.6 BY-204-2 18.9 25.4 18.5 17.2 BY-205-1 19.3 25.8 19.8 16.7 BY-205-2 17 23.5 13.9 14.6 BY-206-1 19.2 25.7 18.3 15.1 BY-206-2 19.7 26.2 18.9 17.6 BY-207-1 20.2 26.7 19.3 16.6 BY-207-2 18.6 25.1 17 14.2 BY-208-1 20.2 26.7 15.7 18 BY-208-2 19 25.5 16.6 13.9 BY-209-1 19.5 26 17.7 17.2 BY-209-4 20 26.5 20.5 14.5 MDDo = Quarterly Minimum Differential Dose= 6.5 mrem MDDA = Annual Minimum Differential Dose = 19.4 mrem 3

17.4 18 19.1 18.3 20.8 14 18.9 16.3 20.8 20.2 17.6 21 20 19.8 17.9 19.9 19.6 21.6 20 ND= Not Detected, where Mo :cc; (Bo+MDDo) or MA s (BA+MDDA) 4 15.1 18.1 17.7 19.1 19.4 15.1 15.6 15.1 19.4 19.4 16.5 16.7 19.1 18.6 16.9 20.2 17.2 17.9 18.9 Bo = Quarterly Normalized Mean Background for a monitoring location (mrem)

BA= Annual Normalized Mean Background for a monitoring location (mrem)

MA= Normalized Annual Dose (mrem)

Quarterly Facility Dose, Annual Fu=Mu-Bu

Baseline, BA (mrem)

(mrem, or "NO" if FuS MDDu) 1 2

3 4

ND ND ND ND 65.5 ND ND ND ND 71.2 ND ND ND ND 76.6 ND ND ND ND 67 ND ND ND ND 79.8 ND ND ND ND 58 ND ND ND ND 67.2 ND ND ND ND 62.4 ND ND ND ND 75.5 ND ND ND ND 77.4 ND ND ND ND 67.9 ND ND ND ND 76.7 ND ND ND ND 78.7 ND ND ND ND 80.7 ND ND ND ND 74.2 ND ND ND ND 80.6 ND ND ND ND 76.1 ND ND ND ND 78 ND ND ND ND 80 BA+

MDDA (mrem) 84.9 90.6 96 86.4 99.2 77.4 86.6 81.8 94.9 96.8 87.3 96.1 98.1 100.1 93.6 100 95.5 97.4 99.4 Annual Facility

Dose, Annual FA=MA-BA Monitoring (mrem, or Data, MA "NO" if (mrem)

FA$

MDDA) 62.1 ND 71 ND 70.9 ND 69.2 ND 77.4 ND 53.1 ND 66.1 ND 58.9 ND 75.9 ND 76.1 ND 62.6 ND 71.1 ND 75.6 ND 74.3 ND 66 ND 73.8 ND 67.3 ND 74.4 ND 73.9 ND

Annual Radiological Environmental Operating Report I YEAR: 2024 I

Page 73 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Environmental Direct Radiation Dosimetry Results Cont'd Ba+

MDDa Quarterly Normalized Quarterly Monitoring Data, Ma Monitoring

Baseline, Location Ba (mrem)

(mrem)

(mrem) 1 2

3 BY-21 12.7 19.2 13.7 12.2 12.9 BY-210-3 18.6 25.1 17.1 15.8 19.3 BY-210-4 17.6 24.1 17.3 13.8 17.9 BY-211-1 18.8 25.3 15.7 17.4 20.6 BY-211-4 19.2 25.7 18.5 17 19.9 BY-212-1 20.1 26.6 19.9 19.4 21.1 BY-212-4 20.5 27 18.6 17.4 22.4 BY-213-1 19.2 25.7 17.7 19.5 19.2 BY-213-4 19.4 25.9 18.1 16.3 19.7 BY-214-1 18.7 25.2 16.8 16.4 18.9 BY-214-4 18.9 25.4 16.3 15.3 19.2 BY-215-1 18.3 24.8 17.9 16.4 18.2 BY-215-4 19.1 25.6 17.4 15.8 20.4 BY-216-1 20.3 26.8 21.9 18.9 21.3 BY-216-2 19 25.5 17.1 13.7 19.3 BY-22 18.3 24.8 16.3 16.3 19.4 BY-23 17.8 24.3 16.4 15.4 17.9 BY-24 16 22.5 13.9 16.1 16.1 BY-301-1 12.8 19.3 12.8 11.4 13.6 MDDo = Quarterly Minimum Differential Dose= 6.5 mrem MDDA = Annual Minimum Differential Dose= 19.4 mrem ND= Not Detected, where Mo :5 (Bo+MDDo) or MA :5 (BA+MDDA) 4 12.5 16.7 16.9 17.1 19 19.1 19.5 21.3 18.5 18.2 18.6 17.2 19 19.2 19.3 17.3 16.7 16.6 12.8 Bo = Quarterly Normalized Mean Background for a monitoring location (mrem)

BA= Annual Normalized Mean Background for a monitoring location (mrem)

MA= Normalized Annual Dose (mrem)

Quarterly Facility Dose, Annual

Baseline, Fa=Ma-Ba BA (mrem)

(mrem, or "ND" if Fa S MDDa) 1 2

3 4

ND ND ND ND 50.8 ND ND ND ND 74.4 ND ND ND ND 70.5 ND ND ND ND 75.1 ND ND ND ND 76.6 ND ND ND ND 80.2 ND ND ND ND 82.1 ND ND ND ND 76.6 ND ND ND ND 73.9 ND ND ND ND 74.9 ND ND ND ND 75.5 ND ND ND ND 73.2 ND ND ND ND 76.5 ND ND ND ND 81.4 ND ND ND ND 75.8 ND ND ND ND 73.4 ND ND ND ND 71.3 ND ND ND ND 63.9 ND ND ND ND 51.2 BA+

MDDA (mrem) 70.2 93.8 89.9 94.5 96 99.6 101.5 96 93.3 94.3 94.9 92.6 95.9 100.8 95.2 92.8 90.7 83.3 70.6 Annual Facility

Dose, Annual FA=MA-BA Monitoring (mrem, Data, MA or"ND" (mrem) if FAS MDDA) 51.3 ND 68.9 ND 65.9 ND 70.8 ND 74.4 ND 79.5 ND 77.9 ND 77.7 ND 72.6 ND 70.3 ND 69.4 ND 69.7 ND 72.6 ND 81.3 ND 69.4 ND 69.3 ND 66.4 ND 62.7 ND 50.6 ND

Annual Radiological Environmental Operating Report I YEAR: 2024 I Page 74 of 74 Company: Constellation I Plant: Byron Clean Energy Center Units 1 and 2 : Environmental Direct Radiation Dosimetry Results Cont'd Ba+ MDDa Normalized Quarterly Monitoring Data, Ma Quarterly Monitoring

Baseline, Location Ba (mrem)

(mrem)

(mrem) 1 2

BY-301-2 15 21.5 15.3 12.7 BY-309-1 17.1 23.6 17 14.6 BY-309-2 18.1 24.6 17.1 16.3 BY-309-3 16.5 23 15.1 13.7 BY-309-4 15.2 21.7 16.2 13.4 BY-314-2 14 20.5 13 10.3 MDDo = Quarterly Minimum Differential Dose= 6.5 mrem MDDA = Annual Minimum Differential Dose= 19.4 mrem 3

14.3 17.6 19 17.6 17.3 14 ND = Not Detected, where Mos; (Bo+MDDo) or MA s; (BA+MDDA) 4 13.6 15.2 17.6 15.4 15.4 12.3 Bo = Quarterly Normalized Mean Background for a monitoring location (mrem)

BA= Annual Normalized Mean Background for a monitoring location (mrem)

MA= Normalized Annual Dose (mrem)

Quarterly Facility Dose, Annual Fa=Ma-Ba

Baseline, BA (mrem)

(mrem, or "ND" if Fas MDDa) 1 2

3 4

ND ND ND ND 60.2 ND ND ND ND 68.4 ND ND ND ND 72.2 ND ND ND ND 66.1 ND ND ND ND 61 ND ND ND ND 56.1 BA+

MDDA (mrem) 79.6 87.8 91.6 85.5 80.4 75.5 Annual Facility

Dose, FA=MA-BA Annual Monitoring (mrem, or Data, MA "ND" if (mrem)

FA :S MDDA) 55.9 ND 64.4 ND 70 ND 61.8 ND 62.3 ND 49.6 ND

Intentionally left blank

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page O of 18 Company: Constellation I Plant: Byron Clean Energy Center 2024 Annual Radiological Groundwater Protection Program Report Document Number: 0CAN10001

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Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 1 of 18 Company: Constellation I Plant: Byron Clean Energy Center TABLE OF CONTENTS 1.0 LIST OF ACRONYMS AND DEFINITIONS................................................................................ 2

2.0 INTRODUCTION

........................................................................................................................ 4 2.1 About Nuclear Power...................................................................................................... 4 2.2 About Radiation Dose..................................................................................................... 6 2.3 About Dose Calculation.................................................................................................. 8 3.0 NEI 07-07 ONSITE RADIOLOGICAL GROUNDWATER MONITORING PROGRAM............... 10 4.0 BIBLIOGRAPHY...................................................................................................................... 18 TABLES Table 1, Groundwater Protection Program Monitoring Well Sampling Locations.................................. 1 O Table 2, Groundwater Protection Program Monitoring Well Tritium, Strontium, and Gross Alpha in Groundwater Samples (pCi/L +/- 2 sigma)............................................................................................. 13 Table 3, Groundwater Protection Program Monitoring Well Gamma Isotopic in Groundwater Samples (pCi/L +/- 2 sigma)................................................................................................................................. 15 Table 4, Groundwater Protection Program Monitoring Well Hard-To-Detect in Groundwater Samples (pCi/L+/- 2 sigma).................................................................................................................................. 16 FIGURES Figure 1, Pressurized Water Reactor (PWR) [1]..................................................................................... 4 Figure 2, Boiling Water Reactor (BWR) [2]............................................................................................. 5 Figure 3, Sources of Radiation Exposure (NCRP Report No. 160) [3].................................................... 6 Figure 4, Potential exposure pathways to Members of the Public due to Plant Operations [6]............... 8 Figure 5, Monitoring Well Locations, Byron Clean Energy Center, 2024.............................................. 11

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 2 of 18 Company: Constellation I Plant: Byron Clean Energy Center 1.0 LIST OF ACRONYMS AND DEFINITIONS

1.

Alpha Particle (a): A charged particle emitted from the nucleus of an atom having a mass and charge equal in magnitude of a helium nucleus.

2.

BWR: Boiling Water Reactor

3.

Composite Sample: A series of single collected portions (aliquots) analyzed as one sample. The aliquots making up the sample are collected at time intervals that are very short compared to the composite period.

4.

Control: A sampling station in a location not likely to be affected by plant effluents due to its distance and/or direction from the Plant.

5.

Counting Error: An estimate of the two-sigma uncertainty associated with the sample results based on total counts accumulated.

6.

Curie (Ci): A measure of radioactivity; equal to 3.7 x 1010 disintegrations per second, or 2.22 x 1012 disintegrations per minute.

7.

Direct Radiation Monitoring: The measurement of radiation dose at various distances from the plant is assessed using thermoluminescent dosimeters (TLDs), optically stimulated luminescent dosimeters (OSLDs), and/or pressurized ionization chambers.

8.

Grab Sample: A single discrete sample drawn at one point in time.

9.

Indicator: A sampling location that is potentially affected by plant effluents due to its proximity and/or direction from the plant

10.

Ingestion Pathway: The ingestion pathway includes milk, fish, drinking water and garden produce. Also sampled (under special circumstances) are other media such as vegetation or animal products when additional information about particular radionuclides is needed.

11.

ISFSI: Independent Spent Fuel Storage Installation

12.

LLD: Lower Limit of Detection. An a priori measure of the detection capability of a radiochemistry measurement based on instrument setup, calibration, background, decay time, and sample volume. An LLD is expressed as an activity concentration. The MDA is used for reporting results. LLD are specified by a regulator, such as the NRC and are typically listed in the ODCM.

13.

MDA: Minimum Detectable Activity. For radiochemistry instruments, the MDA is the a posteriori minimum concentration that a counting system detects. The smallest concentration or activity of radioactive material in a sample that will yield a net count above instrument background and that is detected with 95%

probability, with only 5% probability of falsely concluding that a blank observation represents a true signal.

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 3 of 18 Company: Constellation I Plant: Byron Clean Energy Center

14.

MDC: Minimum Detectable Concentration. Essentially synonymous with MDA for the purposes of radiological monitoring.

15.

Mean: The sum of all of the values in a distribution divided by the number of values in the distribution, synonymous with average.

16.

Microcurie (µCi): 3.7 x 104 disintegrations per second, or 2.22 x106 disintegrations per minute.

17.

millirem (mrem): 1/1000 rem; a unit of radiation dose equivalent in tissue.

18.

Milliroentgen (mR): 1/1000 Roentgen; a unit of exposure to X-or gamma radiation.

19.

N/A: Not Applicable

20.

NEI: Nuclear Energy Institute

21.

NRC: Nuclear Regulatory Commission

22.

ODCM: Offsite Dose Calculation Manual

23.

OSLO: Optically Stimulated Luminescence Dosimeter

24.

Protected Area: A 10 CFR 73 security term is an area encompassed by physical barriers and to which access is controlled for security purposes. The fenced area immediately surrounding the plant and around ISFSI are commonly classified by the licensee as "Protected areas." Access to the protected area requires a security badge or escort.

25.

PWR: Pressurized Water Reactor

26.

REC: Radiological Effluent Control

27.

REMP: Radiological Environmental Monitoring Program

28.

Restricted Area: A 10 CFRR 20 defined term where access to which is limited by the licensee for the purpose of protecting individuals against undue risks from exposure to radiation and radioactive materials.

29.

TEDE: Total Effective Dose Equivalent (TEDE) means the sum of the effective dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).

30.

TLD: Thermoluminescent Dosimeter

31.

TRM: Technical Requirements Manual

32.

TS: Technical Specification

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 4 of 18 Company: Constellation I Plant: Byron Clean Enerav Center

33.

Unrestricted Area: An area, access to which is neither limited nor controlled by the licensee.

2.0 INTRODUCTION

2.1 About Nuclear Power Commercial nuclear power plants are generally classified as either Boiling Water Reactors (BWRs) or Pressurized Water Reactors (PWRs), based on their design. A BWR includes a single coolant system where water used as reactor coolant boils as it passes through the core and the steam generated is used to turn the turbine generator for power production. A PWR, in contrast, includes two separate water systems: radioactive reactor coolant and a secondary system. Reactor coolant is maintained under high pressure, preventing boiling. The high-pressure coolant is passed through a heat exchanger called a steam generator where the secondary system water is boiled, and the steam is used to turn the turbine generator for power production.

Containment Structtrc ri

/

Generator

/"",_* >.::.

--*~--

/

Figure 1, Pressurized Water Reactor (PWR) [1]

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 5 of 18 Company: Constellation I Plant: Byron Clean Energy Center Containment Structure Figure 2, Boiling Water Reactor (BWR) [2]

Electricity is generated by a nuclear power plant similarly to the way that electricity is generated at other conventional types of power plants, such as those powered by coal or natural gas. Water is boiled to generate steam; the steam turns a turbine that is attached to a generator and the steam is condensed back into water to be returned to the boiler. What makes nuclear power different from these other types of power plants is that the heat is generated by fission and decay reactions occurring within and around the core containing fissionable uranium (U-235).

Nuclear fission occurs when certain nuclides (primarily U-233, U-235, or Pu-239) absorb a neutron and break into several smaller nuclides (called fission products) as well as producing some additional neutrons.

Fission results in production of radioactive materials including gases and solids that must be contained to prevent release or treated prior to release. These effluents are generally treated by filtration and/or hold-up prior to release. Releases are generally monitored by sampling and by continuously indicating radiation monitors. The effluent release data is used to calculate doses in order to ensure that dose to the public due to plant operation remains within required limits.

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 6 of 18 Company: Constellation I Plant: Byron Clean Enerav Center 2.2 About Radiation Dose Ionizing radiation, including alpha, beta, and gamma radiation from radioactive decay, has enough energy to break chemical bonds in tissues and result in damage to tissue or genetic material. The amount of ionization that will be generated by a given exposure to ionizing radiation is quantified as dose. Radiation dose is generally reported in units of millirem (mrem) in the US.

Space (background)

Terrestrial (background)

(3%)

Computed

\\

tomography 1

\\\\,

(medical)

(24%)

Nuclear medicine (medical)

(12%)

\\,\\_,/./

lnterventional fluoroscopy (medical)

(7%)

(5%)

Radon & thoron (background)

(37%)

Industrial

(<0.1%)

Occupational

(<0.1%)

Consumer Conventional radiography/fluoroscopy (medical)

(5%)

(2%)

Figure 3, Sources of Radiation Exposure (NCRP Report No. 160) [3]

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 7 of 18 Company: Constellation I Plant: Byron Clean Ener~v Center The National Council on Radiation Protection (NCRP) has evaluated the population dose for the US and determined that the average individual is exposed to approximately 620 mrem per year [3]. There are many sources for radiation dose, ranging from natural background sources to medical procedures, air travel, and industrial processes. Approximately half (310 mrem) of the average exposure is due to natural sources of radiation including exposure to radon, cosmic radiation, and internal radiation and terrestrial due to naturally occurring radionuclides. The remaining 310 mrem of exposure is due to man-made sources of exposure, with the most significant contributors being medical (48% of total mrem per year) due to radiation used in various types of medical scans and treatments. Of the remaining 2%

of dose, most is due to consumer activities such as air travel, smoking cigarettes, and building materials. A small fraction of this 2% is due to industrial activities including generation of nuclear power.

Readers that are curious about common sources and effects of radiation dose that they may encounter can find excellent sources of information from the Health Physics Society, including the Radiation Fact Sheets [4], and from the US Nuclear Regulatory Commission website [5).

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 8 of 18 Company: Constellation I Plant: Byron Clean Energy Center 2.3 About Dose Calculation Concentrations of radioactive material in the environment resulting from plant operations are very small and it is not possible to determine doses directly using measured activities of environmental samples. To overcome this, dose calculations based on measured activities of effluent streams are used to model the dose impact for Members of the Public due to plant operation and effluents. There are several mechanisms that can result in dose to Members of the Public, including: Ingestion of radionuclides in food or water; Inhalation of radionuclides in air; Immersion in a plume of noble gases; and Direct Radiation from the ground, the plant or from an elevated plume.

.l;<*JJo.,ition Livestock products f"

Gaseous effiuents lnl!"l'stion *

.11 0

~I CD

\\ Inhalation

\\lll'po.,ition t A.*::... '.':~~':".1:'.1:: *** *******1

- - ********* Agricultural o \\o~

Public

~*.jt ~

Soil Soil

Jnnp,tion....

Liquid cffiuents 0

~

~larinc produce;;

&a 0

Radionuclides

.... : Behavior of radionuclides Figure 4, Potential exposure pathways to Members of the Public due to Plant Operations [6]

Each plant has an Offsite Dose Calculation Manual (ODCM) that specifies the methodology used to obtain the doses in the Dose Assessment section of this report.

The dose assessment methodology in the ODCM is based on NRC Regulatory Guide 1.109 [7] and NUREG-0133 [8]. Doses are calculated by determining what the nuclide concentration will be in air, water, on the ground, or in food products based on plant effluent releases. Release points are continuously monitored to quantify what concentrations of nuclides are being released. For gaseous releases meteorological data is used to determine how much of the released activity will be present at a given location outside of the plant either deposited onto the ground or in gaseous form.

Intake patterns and nuclide bio-concentration factors are used to determine how much activity will be transferred into animal milk or meat. Finally, human ingestion factors and dose factors are used to determine how much activity will be consumed and how much dose the consumer will receive. Inhalation dose is calculated by determining the concentration of nuclides and how much air is breathed by the individual.

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 9 of 18 Company: Constellation I Plant: Byron Clean Energy Center For liquid releases, dilution and mixing factors are used to model the environmental concentrations in water. Drinking water pathways are modeled by determining the concentration of nuclides in the water at the point where the drinking water is sourced (e.g., taken from wells, rivers, or lakes). Fish and invertebrate pathways are determined by using concentration at the release point, bioaccumulation factors for the fish or invertebrate and an estimate of the quantity of fish consumed.

Each year a Land Use Census is performed to determine what potential dose pathways currently exist within a five-mile radius around the plant, the area most affected by plant operations. The Annual Land Use Census identifies the locations of vegetable gardens, nearest residences, milk animals and meat animals. The data from the census is used to determine who is the likely to be most exposed to radiation dose as a result of plant operation.

There is significant uncertainty in dose calculation results, due to modeling dispersion of material released and bioaccumulation factors, as well as assumptions associated with consumption and land-use patterns. Even with these sources of uncertainty, the calculations do provide a reasonable estimate of the order of magnitude of the exposure. Conservative assumptions are made in the calculation inputs such as the number of various foods and water consumed, the amount of air inhaled, and the amount of direct radiation exposure from the ground or plume, such that the actual dose received are likely lower than the calculated dose. Even with the built-in conservatism, doses calculated for the maximum exposed individual due to plant operation are a very small fraction of the annual dose that is received due to other sources. The calculated doses due to plant effluents, along with REMP results, serve to provide assurance that radioactive effluents releases are not exceeding safety standards for the environment or people living near the plant.

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 10 of 18 Company: Constellation I Plant: Byron Clean Ener~v Center 3.0 NEI 07-07 ONSITE RADIOLOGICAL GROUNDWATER MONITORING PROGRAM Byron Clean Energy Center has developed a Groundwater Protection Initiative (GPI) program in accordance with NEI 07-07, Industry Ground Water Protection Initiative -

Final Guidance Document [9]. The purpose of the GPI is to ensure timely detection and an effective response to situations involving inadvertent radiological releases to groundwater in order to prevent migration of licensed radioactive material off-site and to quantify impacts on decommissioning. During 2024, Byron Clean Energy collected and analyzed groundwater samples in accordance with the requirements of requirements of approved procedures following regulatory methods.

This section is included in this report to communicate results of NEI 07-07 Radiological Groundwater Monitoring Program. Monitoring wells installed as part of GPI program are sampled and analyzed as summarized in Table 1, Groundwater Protection Program Monitoring Well Sampling Locations. In addition to reporting results from NEI 07-07 monitoring wells, voluntary communications to offsite governmental agencies for onsite leaks or spills per NEI 07-07 Objective 2.2, are also reported as part of this report. It is important to note, samples and results taken in support of NEI 07-07 groundwater monitoring program are not part of the Radiological Environmental Monitoring Program (REMP) but should be reported as part of ARERR.

Table 1, Groundwater Protection Program Monitoring Well Sampling Locations Site Site Type Temporary /Permanent Distance and Direction AR-1 Monitoring Well Permanent 0.36 miles NNW AR-2 Monitoring Well Permanent 0.6 miles NW AR-3 Monitoring Well Permanent 0.8 miles NW AR-4 Monitoring Well Permanent 1.36 miles WNW AR-5 Monitoring Well Permanent 1.92 miles WNW AR-6 Monitoring Well Permanent 2.04 miles WNW AR-7 Monitoring Well Permanent 0.04 milesW AR-8 Monitoring Well Permanent 0.12 miles S AR-9 Monitoring Well Permanent 0.24 miles E AR-10 Monitoring Well Permanent 0.28 miles NE AR-11 Monitoring Well Permanent 1.36 miles WNW AR-12 Monitoring Well Permanent 366 feetW AR-13 Monitoring Well Permanent 461 feet WSW CAR-1 Monitoring Well Permanent 2.25 miles WNW CAR-3 Monitoring Well Permanent 0.16 miles SE TW-13 Monitoring Well Permanent 2.3 miles WNW CROP Surface Water Permanent 0.2 miles NE

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I

Page 11 of 18 Company: Constellation I Plant: Byron Clean Energy Center MAP OF COLLECTION SITES

~

N CL 0

Q'

<(

0 0

0 Figure 5, Monitoring Well Locations, Byron Clean Energy Center, 2024

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 12 of 18 Company: Constellation I Plant: Byron Clean Energy Center Radiological Groundwater Monitoring Program tritium results are summarized in Table 2. Naturally occurring Potassium-40 was detected at one of the monitoring well locations.

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 13 of 18 Company: Constellation I Plant: Byron Clean Enerav Center Table 2, Groundwater Protection Program Monitoring Well Tritium, Strontium, and Gross Alpha in Groundwater Samples (pCi/L +/- 2 sigma)

Collection Site Date H-3 Sr-89 Sr-90 Gr-A(Dis)

Gr-A(Sus)

AR-1 3/6/2024

< 190 AR-1 5/22/2024

< 193

< 7

< 0.6

< 1

< 0.9 AR-1 9/13/2024

< 193 AR-1 11/8/2024

< 191 AR-2 5/23/2024

< 189 AR-3 3/7/2024

< 188 AR-3 5/23/2024

< 190

< 9

< 0.9 1

< 0.9 AR-3 9/13/2024

< 187 AR-3 11/7/2024

< 195 AR-4 3/7/2024 198

+/-

123 AR-4 5/23/2024 271

+/-

129

< 8

< 0.6

< 1

< 1 AR-4 9/13/2024

< 189 AR-4 11/7/2024

< 194 AR-7 3/5/2024

< 199 AR-7 5/20/2024

< 199

< 8

< 0.7

< 1

< 0.9 AR-7 9/13/2024

< 190 AR-7 11/6/2024

< 189 AR-8 3/5/2024

< 189 AR-8 5/22/2024

< 192

< 7

< 0.6

< 1

< 0.9 AR-8 9/13/2024

< 183 AR-8 11/6/2024

< 199 AR-9 3/6/2024

< 188 AR-9 5/22/2024

< 192

< 8

< 0.7 1

< 0.9 AR-9 9/13/2024

< 187 AR-9 11/7/2024

< 198 AR-10 5/22/2024

< 185

Annual Radiological Groundwater Protection Program Report

[ YEAR: 2024

[

Page 14 of 18 Company: Constellation I Plant: Byron Clean Energy Center Table 2, Groundwater Protection Program Monitoring Well Tritium, Strontium, and Gross Alpha in Groundwater Samples (pCi/L +/- 2 sigma) Cont'd Collection Site Date H-3 Sr-89 Sr-90 Gr-A(Dis)

Gr-A(Sus)

AR-11 5/23/2024 444

+/-

138 AR-11 11/7/2024 323

+/-

136 AR-12 3/5/2024 188 AR-12 5/20/2024 188 8

0.7

< 3

< 2 AR-12 9/13/2024 189 AR-12 11/6/2024 199 AR-13 3/5/2024 191 AR-13 5/20/2024 194

< 4 0.7

< 2 2

AR-13 9/13/2024 189 AR-13 11/6/2024 197 CAR-1 5/23/2024 194 CAR-3 3/5/2024 191 CAR-3 5/20/2024 191 7

0.6 1

0.9 CAR-3 9/13/2024 188 CAR-3 11/7/2024 192

CROP 3/6/2024 191

CROP 5/22/2024 194 7

0.6

< 0.7 0.9

CROP 9/13/2024 190

CROP 11/7/2024 193 TW-13 5/23/2024 192

Surface water

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 15 of 18 Company: Constellation I Plant: Byron Clean Energy Center Table 3, Groundwater Protection Program Monitoring Well Gamma Isotopic in Groundwater Samples (pCi/L +/- 2 sigma)

Collection Site Date Be-7 K-40 Co-58 Fe-59 Co-60 Zn-65 Nb-95 Zr-95 1-131 Cs-134 Cs-137 Ba-140 La-140 BY-AR-1 5/22/2024 16 29 2

4 2

3 3

2 2

9 3

BY-AR-2 5/23/2024 16 29 2

< 4 2

4 2

3 3

2 2

9 3

BY-AR-3 5/23/2024 15 36 2

4 2

3 3

2 2

9 3

BY-AR-4 5/23/2024 13 15 2

3 2

3 3

2 2

8 3

BY-AR-7 5/20/2024 16 18 2

4 2

< 4 4

2 2

10 3

BY-AR-8 5/22/2024 14 27 2

3 2

3 3

2 2

8 3

BY-AR-9 5/22/2024 16 36 2

4 2

3 3

2 2

9 3

BY-AR-10 5/22/2024 13 15 1

3 2

3 1

3 3

2 1

8 3

BY-AR-11 5/23/2024 19 17 2

4 2

< 4 4

2 2

10

< 4 BY-AR-12 5/20/2024 11 33

+/-

18 1

3 2

3 1

2 3

1 1

6 2

BY-AR-13 5/20/2024 16 32 2

3 2

3 4

2 2

9 3

BY-CAR-1 5/23/2024 15 33 2

4 2

3 2

3 3

2 2

8 3

BY-CAR-3 5/20/2024 16 29 2

< 4 2

4 2

3 4

2 2

10 3

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 16 of 18 Company: Constellation I Plant: Byron Clean Enerav Center Table 4, Groundwater Protection Program Monitoring Well Hard-To-Detect in Groundwater Samples (pCi/L+/- 2 sigma)

No samples collected or analyzed for hard to detects in 2024

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 17 of 18 Company: Constellation I Plant: Byron Clean EnerQV Center 3.1 Voluntary Notification During 2024, Byron Clean Energy Center did not make a voluntary NEI 07-07 notification to State/Local officials, NRC, and to other stakeholders required by site procedures.

Annual Radiological Groundwater Protection Program Report I YEAR: 2024 I Page 18 of 18 Company: Constellation I Plant: Byron Clean Energy Center 4.0 BIBLIOGRAPHY

[1] Nuclear Regulatory Commission, 30 June 2015. [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/students/animated-pwr.html. [Accessed October 2020].

[2] Nuclear Regulatory Commission, 25 June 2015. [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/students/animated-bwr.html. [Accessed October 2020].

[3] "NCRP Report No. 160 - Ionizing Radiation Exposure of the Population of the United States,"

National Council on Radiation Protection and Measurements, Bethesda, MD, 2009.

[4] Health Physics Society, [Online]. Available: http://hps.org/hpspublications/radiationfactsheets.html.

[Accessed 2020].

[5] "NRC Resource Page," [Online]. Available: http://www.nrc.gov/about-nrc/radiation.html. [Accessed 10 November 2020].

[6] "Japan Atomic Energy Agency," 06 November 2020. [Online]. Available:

https://www.jaea.go.jp/english/04/ntokai/houkan/houkan_02.html.

[7] "Regulatory Guide 1.109 - Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Demonstrating Compliance with 10 CFR Part 50, Appendix I," Nuclear Regulatory Commission, Ocotober, 1977.

[8] "NUREG-0133 - Preparation of Effluent Technical Specifications for Nuclear Power Plants,"

Nuclear Regulatory Commission, 1987.

[9] "NEI 07 Industry Ground Water Protection Initiative -

Final Guidance Document, Rev. 1,"

Nuclear Energy Institute, Washington, D.C., 2019.

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