Text

Independent Spent Fuel Storage Installation - Annual Radiological Environmental Operating Report
	ML25135A003
Person / Time
Site:	Calvert Cliffs
Issue date:	05/15/2025
From:	; Constellation Energy Generation
To:	; Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation
Shared Package
ML25135A001	List: ML25135A002; ML25135A003;
References
	Download: ML25135A003 (1)
	v • d • e

Calvert Cliffs Nuclear Power Plant 2024 Document Number: 50-317/50-318/72-8 Annual Radiological Environmental Operating Report

Annual Radiological Environmental Operating Report YEAR: 2024 Page 1 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant TABLE OF CONTENTS 1.0 LIST OF ACRONYMS AND DEFINITIONS.................................................................................. 3 2.0 EXECUTIVE

SUMMARY

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

Conclusions:

................................................................................................. 6

3.0 INTRODUCTION

........................................................................................................................... 7 4.0 SITE DESCRIPTION AND SAMPLE LOCATIONS....................................................................... 8 5.0 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM REQUIREMENTS............... 10 6.0 MAPS OF COLLECTION SITES................................................................................................. 17 7.0 REPORTING LEVELS FOR RADIOACTIVITY CONCENTRATIONS IN ENVIRONMENTAL SAMPLES................................................................................................... 20 8.0 SAMPLING PROGRAM, PROGRAM MODIFICATION AND INTEPRETATION OF RESULTS.................................................................................................................................... 21 8.1 Environmental Direct Radiation Dosimetry Results......................................................... 21 8.2 Air Particulate and Radioiodine Sample Results............................................................. 23 8.3 Waterborne Sample Results........................................................................................... 24 8.4 Ingestion Pathway Sample Results................................................................................. 26 9.0 LAND USE CENSUS.................................................................................................................. 27 10.0 SAMPLE DEVIATIONS, ANOMALIES AND UNAVAILABILITY................................................. 28 11.0 OTHER SUPPLEMENTAL INFORMATION................................................................................ 29 11.1 NEI 07-07 Onsite Radiological Groundwater Monitoring Program.................................. 29 11.2 Independent Spent Fuel Storage Installation (ISFSI) Monitoring Program..................... 29 11.3 Corrections to Previous Reports..................................................................................... 30 12.0 BIBLIOGRAPHY......................................................................................................................... 31 TABLES Table 1: Radiological Environmental Monitoring Program and ISFSI - Direct Radiation....................... 10 Table 2: Radiological Environmental Monitoring Program and ISFSI - Airborne................................... 11 Table 3: Radiological Environmental Monitoring Program and ISFSI - Waterborne and Terrestrial..... 12 Table 4: Radiological Environmental Monitoring Program - Ingestion................................................... 13 Table 5: REMP and ISFSI Sampling Locations - Direct Radiation......................................................... 14 Table 6: Reporting Levels for Radioactivity Concentrations in Environmental Samples........................ 20 Table 7: Lower Limits of Detection for Environmental Sample Analysis................................................. 20 Table 8: Land Use Census - Nearest Receptors within 5 miles............................................................. 28 Table 9: Sample Deviation Summary..................................................................................................... 29 Table 10: Monthly Sampling Bay Water (pCi/L) and Garden Vegetation (pCi/kg).................................. 36 Table 10 Continued: Monthly Sampling Bay Water (pCi/L) and Vegetation (pCi/kg)............................. 37 Table 11: Weekly Air Monitoring Particulate and I-131 Filters (pCi/m3)................................................. 39 Table 11 Continued: Weekly Air Monitoring Iodine131 Cartridge Filters (pCi/m3)................................. 45 Table 12: Quarterly isotopic data - Air (pCi/m3), Oysters (pCi/kg), and ISFSI Veg (pCi/kg wet) ISFSI Soil (pCi/kg)............................................................................................................................................ 47 Table 13: Complete REMP Results, Sediment and Fish........................................................................ 48 Table 14: Cross Check Intercomparison Results.................................................................................... 52

Annual Radiological Environmental Operating Report YEAR: 2024 Page 2 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 15: Alpha Isotopic and Pu-241 in Groundwater (pCi/L)................................................................ 79 Table 16: Gross Alpha and Strontium Monitoring Results (pCi/L).......................................................... 80 Table 17: Annual Well Monitoring Gamma Emitters (pCi/L)................................................................... 80 Table 18: Quarterly Monitoring Tritium (pCi/L)........................................................................................ 81 Table 18 Continued: Annual Well Monitoring Tritium (pCi/L).................................................................. 81 Table 19: Quarterly Precipitation Monitoring Tritium (pCi/L)................................................................... 81 Table 20: Locations of Radiological Groundwater Environmental Sampling Stations............................ 82 FIGURES Figure 1: Potential exposure pathways to Members of the Public due to Plant Operations [7]................ 7 Figure 2: REMP Sample Locations (Near Field/Site Boundary)............................................................. 17 Figure 3: REMP Sample Locations (Far Field)....................................................................................... 18 Figure 4: REMP Nearest Residence and Garden Locations.................................................................. 19 Figure 5: Air Particulate: Analysis for Gross Beta, Average for All Indicator vs. Control Location......... 24 Figure 6: Surface Water Tritium Results................................................................................................. 25 Figure 7: REMP Quarterly (91 day) Exposure of Environmental Dosimeters......................................... 76 Figure 8: REMP Mean Dosimeter Gamma Dose 10 Year History.......................................................... 77 Figure 9: ISFSI Mean Dosimeter Gamma Dose 10 Year History........................................................... 78 Figure 10: Site Map Groundwater Monitoring Wells............................................................................... 83 Figure 11: Site Map Precipitation Recapture Locations.......................................................................... 84 ATTACHMENTS, Data Table Summary....................................................................................................... 34, Complete Data Table for All Analysis Results Obtained In 2024..................................... 35, Cross Check Intercomparison Program........................................................................... 49, Environmental Direct Radiation Dosimetry Results......................................................... 74, Radiological Groundwater Protection Program............................................................... 79

Annual Radiological Environmental Operating Report YEAR: 2024 Page 3 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 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 (OSLD) 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 YEAR: 2024 Page 4 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

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.

NRC: Nuclear Regulatory Commission

24.

ODCM: Offsite Dose Calculation Manual

25.

OSLD: 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

Calvert Cliffs Nuclear Power Plant Radiological Environmental Monitoring Program (REMP) was established in 1970 prior to the station becoming operational to provide information on background radiation present in the area. The goal of CCNPP 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) and the Environmental Technical Specifications and the Independent Spent Fuel Storage Installation (ISFSI) Technical Specifications. The entire monitoring program in place around CCNPP is divided into three parts: the original REMP, the ISFSI monitoring program, and the Non-ODCM Radiological Environmental Monitoring 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 YEAR: 2024 Page 5 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant The Annual Radiological Environmental Operating Report (AREOR) provides data obtained through analyses of environmental samples collected at CCNPP for the reporting period of January 1st through December 31st, 2024. During that time period 1434 were performed on 1390 samples.

A dose assessment based on the onsite meteorological data and radwaste release information for this time period was performed. The results of these calculations indicate:

Gaseous Pathways A maximum thyroid dose of 6.42E-05 mrem to a child via the plume, ground, vegetable, and inhalation pathways at 1.5 miles WSW of the containments at Calvert Cliffs.

This is about 0.000000856% of the acceptable limit of 75 mrem/yr as specified in 40CFR190 and 10CFR72.104.

A maximum whole-body gamma dose of 5.64E-05 mrem to a child at 1.4 miles W of the containments at Calvert Cliffs. This is about 0.00000226% of the acceptable dose limit of 25 mrem/yr as specified in 40CFR190 and 10CFR72.104.

A maximum dose to any other organ, in this case skin, of 3.81E-05 mrem to a teen at 1.1 miles SW of the containments at Calvert Cliffs. This is about 0.00000152% of the acceptable dose limit of 25 mrem/yr as specified in 40CFR190 and 10CFR72.104.

Liquid Pathways A maximum thyroid dose of 8.09E-04 mrem to a teen for all liquid pathways, which is about 0.00108% of the acceptable dose limit of 75 mrem/yr as specified in 40CFR190 and 10CFR72.104.

A maximum whole-body dose of 9.40E-04 mrem to a teen via all liquid pathways, which is about 0.00125% of the acceptable dose limit of 25 mrem/yr as stated in 40CFR190 and 10CFR72.104.

A maximum dose to any other organ, in this case GI, of 1.83E-03 mrem to an adult for all pathways, which is 0.00244% of the acceptable dose limit of 25 mrem/yr specified in 40CFR190 and 10CFR72.104.

Gaseous and Liquid Pathways Combined A maximum thyroid dose of 8.73E-04 mrem via liquid and gaseous pathways, which is about 0.0000116% of the acceptable limit of 75 mrem/yr as specified in 40CFR190 and 10CFR72.104.

A maximum whole-body dose of 9.96E-04 mrem via liquid and gaseous pathways, which is about 0.0000399% of the acceptable limit of 25 mrem/yr as specified in 40CFR190 and 10CFR72.104.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 6 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant A maximum calculated dose to all other organs via liquid and gaseous pathways was equal to 1.87E-03 mrem. This dose was about 0.0000747% of the allowable limit of 25 mrem/yr as specified in 40CFR190 and 10CFR72.104.

In all cases, the calculated doses are a small fraction of the applicable limits specified in 40CFR190 and 10CFR72.104.

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 CCNPP, did not result in detection of plant related radionuclides in the environment There was Facility related dose from the ISFSI observed at OSLDs located around the ISFSI. As spent fuel casks are installed during the year and due to the close proximity of these OSLDs to the spent fuel storage structures, they detect the small increase in radiation exposure each year. However, it is clear from the review of the results from the ISFSI and other REMP dosimeters when compared to control Dosimeters that there is no observable direct radiation exposure to the public.

2.1 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 CCNPP. 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-7, 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 YEAR: 2024 Page 7 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

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].

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

Quality assurance aspects of the sampling program and OSLD data collection are conducted in accordance with Regulatory Guides 4.15 [8] and 4.13 [9]. REMP also adheres to the requirements of Maryland, CCNPP 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 YEAR: 2024 Page 8 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 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 Calvert Cliffs Nuclear Power Plant is a commercial nuclear power plant consisting of Unit 1 that achieved initial criticality on October 7, 1974, and Unit 2 that achieved criticality on November 30, 1976. The plant is located in Southern Maryland on the shore of the Chesapeake Bay. The surrounding area includes the Calvert Shore Sanctuary to the south, the community of White Sands to the west, and Saint Leonard to the North. All distance and direction measurements are from the center point between the two units and the nearest residence is two miles to the northwest.

The plant effluents and meteorological data are used to plot the expected D/Q and displayed in the map below.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 9 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant CCNPP 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 Monitoring Program and ISFSI - Direct Radiation Table 2, Radiological Environmental Monitoring Program and ISFSI - Airborne Table 3, Radiological Environmental Monitoring Program and ISFSI -

Waterborne and Terrestrial Table 4, Radiological Environmental Monitoring Program - Ingestion Table 5, REMP Sampling Locations - Direct Radiation Figure 2, REMP Sample Locations (Near Field/Site Boundary)

Figure 3, REMP Sample Locations (Far Field)

Figure 4, REMP Nearest Residence and Garden Locations

Annual Radiological Environmental Operating Report YEAR: 2024 Page 10 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 5.0 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM REQUIREMENTS Table 1: Radiological Environmental Monitoring Program and ISFSI - Direct Radiation Requirement Sample Location Description, Distance, and Direction Sampling Collection/

Frequency Type and Frequency of Analyses Direct Radiation 23 Routine monitoring stations with two or more 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 at approximately 5 miles from the site; and Special interest areas, such as population centers, nearby recreation areas, and control stations 19 additional ISFSI monitoring stations with two or more dosimeters placed in each sector around the centerpoint of the ISFSI and a Control location shared with REMP.

See Table 5 Quarterly Gamma dose/Quarterly

Annual Radiological Environmental Operating Report YEAR: 2024 Page 11 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 2: Radiological Environmental Monitoring Program and ISFSI - Airborne Requirement Sample Location Description, Distance, and Direction Sampling Collection/

Frequency Type and Frequency of Analyses Airborne Radioiodine and Particulates Samples from 5 locations for REMP and additional 4 locations common to REMP and ISFSI:

Three locations (A1, A2, A3) close to the site boundary in different sectors of the highest calculated annual average ground level D/Q.

One sample (A4) from the vicinity of a community having the highest calculated annual average D/Q.

Additional indicator locations common to REMP and ISFSI monitoring, (SFA1, SFA3, SFA4)

One sample (A5) from a Control Location, approximately 10 to 20 miles away in the least predominant wind direction One sample (SFA2) for air particulates only as a Control location for the ISFSI monitoring program A1: On site before entrance to Camp Conoy. 0.5 miles S sector A2: Camp Conoy Rd., at emergency siren. 1.5 miles SSE sector A3: Bay Breeze Rd. 1.6 miles SE sector A4: Route 765, Lusby near Larrys Garage 1.8 miles SSW sector SFA1: Meteorological Station. 0.4 miles SW sector SFA3: NNW of ISFSI. 0.4 miles SSW sector SFA4: SSE of ISFSI. 0.5 miles SSW sector A5: Emergency Operations Facility.

12.1 miles 19.3 KM WNW sector SFA2: Visitors Center - Overlook.

0.2 miles N sector Continuous sampler operation with sample collection weekly Particulate sampler: Analyze for gross beta radioactivity 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following filter change /

Weekly. Perform gamma isotopic analysis on each sample when gross beta activity is > 10 times the yearly mean of control samples.

Perform gamma isotopic analysis on composite sample (by location)/Quarterly.

Radioiodine canister: I-131 analysis/Weekly.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 12 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 3: Radiological Environmental Monitoring Program and ISFSI - Waterborne and Terrestrial Requirement Sample Location Description, Distance, and Direction Sampling Collection/ Frequency Type and Frequency of Analyses Surface Water One sample upstream (Wa1) (control) and one sample downstream (Wa2)

(indicator)

Wa1: at the intake area 0.1 miles NNE sector Wa2: at the discharge area 0.2 miles N sector Composite sample over one-month period; samples from monthly composites are combined to form quarterly composite samples to be analyzed for H-3.

Gamma isotopic

/Monthly, H-3 /Quarterly Sediment from Shoreline One sample downstream area with existing or potential recreational value.

(Wb1)

Wb1 Downstream of Discharge on site at Barge Road Semiannual Gamma isotopic Semiannually Bottom Sediment (Supplemental)

One sample downstream (indicator)

One sample upstream (control)

Wbs2: Discharge area 0.2 miles N sector Wbs4: Camp Conoy/Rocky Point 1.9 miles SE sector Semiannual Gamma isotopic Semiannually Soil (ISFSI)

Four samples around the ISFSI in the vicinity of air samplers SFS1, SFS3, SFS4, and SFS5 (Indicator)

One sample SFS2 (control)

SFS1: Meteorological Station NW of ISFSI SFS3: NNW of the ISFSI SFS4: SSE of the ISFSI SFS5: On Site before entrance to Camp Conoy 0.19 miles ESE sector SFS2: CCNPP Visitors Center Overlook 0.5 miles N sector Quarterly Gamma isotopic Quarterly Vegetation (ISFSI)

Four samples around the ISFSI in the vicinity of air samplers SFB1, SFB3, SFB4, and SFB5 (Indicator)

One sample SFB2 (control)

SFB1: Meteorological Station NW of ISFSI SFB3: NNW of the ISFSI SFB4: SSE of the ISFSI SFB5: On Site before entrance to Camp Conoy 0.19 miles ESE sector SFB2: CCNPP Visitors Center Overlook 0.5 miles N sector Quarterly Gamma isotopic Quarterly

Annual Radiological Environmental Operating Report YEAR: 2024 Page 13 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 4: Radiological Environmental Monitoring Program - Ingestion Requirement Sample Location Description, Distance, and Direction Sampling Collection/

Frequency Type and Frequency of Analyses Fish and Invertebrates:

3 samples of each commercially and recreationally important species (2 fish species and 1 invertebrate species) in vicinity of site discharge (Ia1, Ia2, Ia3).

3 samples of same species in areas not influenced by plant discharge Ia4, Ia5, Ia6).

Ia1, Ia2: Discharge Area 0.2 miles N sector Ia3: Camp Conoy 0.6 miles E sector Ia4, Ia5: Patuxent River, Area not influenced by Plant Discharge Ia6: Kenwood Beach 6.7 miles NNW sector Sample in season, or semiannually if they are not seasonal Gamma isotopic analysis on edible portions, each sample Food Products:

3 different samples of broad leaf vegetation grown near the site boundary at two different locations of highest predicted annual average ground level D/Q, (Ib4, Ib5, Ib6, Ib10, Ib11, Ib12) 1 sample of each of the similar broad leaf vegetation grown 15-30 km distant in the least prevalent wind direction (Ib7, Ib8, Ib9) control location.

Ib4, Ib5, Ib6: Onsite, before entrance to Camp Conoy 0.5 miles S sector Ib10, Ib11, Ib12: Meteorological Station 0.4 miles SW sector Ib7, Ib8, Ib9: Emergency Offsite Facility 12.1 miles WNW sector Sample monthly during growing season Gamma isotopic and I-131 analysis/ each sample

Annual Radiological Environmental Operating Report YEAR: 2024 Page 14 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 5: REMP and ISFSI Sampling Locations - Direct Radiation Site #

Location Type Sector Distance (Miles)1 Description DR 01 Inner Ring NW 0.4 On Site, along north cliffs, on tree DR 02 Inner Ring WNW 1.7 Route 765, along road at junk yard, on TP pole DR 03 Inner Ring W

1.4 Route 765, front of Plumbing business, on TP pole DR 04 Inner Ring WSW 1.2 Route 765, across from Veras Beach Club, on TP pole DR 05 Inner Ring SW 1.5 Route 765, Johns Creek, on TP pole DR 06 Inner Ring SSW 1.8 Route 765, Larrys Garage, on TP pole DR 7*

Inner Ring S

0.5 On Site, plant site garden DR 8 Inner Ring SSE 1.5 Camp Conoy Rd., near Emergency Siren DR 9 Inner Ring SE 1.6 Bay Breeze Rd., on TP pole DR 10 Outer Ring NW 4.0 Decatur & Calvert Beach Rds., on TP pole DR 11 Outer Ring WNW 4.1 Mackall & Parran Rds, 1 mile back dirt rd., on TP pole DR 12 Outer Ring W

4.2 Bowan & Mackall Rds., on TP pole DR 13 Outer Ring WSW 3.8 Mackall Rd., near Wallville, on TP pole DR 14 Outer Ring SW 4.0 Rodney Point, on TP pole DR 15 Outer Ring SSW 3.9 Mill Bridge & Turners Rds., on TP pole DR 16 Outer Ring S

4.1 Across from Appeal School, near rd., on TP pole

Annual Radiological Environmental Operating Report YEAR: 2024 Page 15 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 5: REMP and ISFSI Sampling Locations - Direct Radiation Site #

Location Type Sector Distance (Miles)1 Description DR 17 Outer Ring SSE 3.7 Cove Pt. & Little Cove Pt. Rds., on TP pole DR 18 Outer Ring SE 4.5 Cove Point, at entrance to Lighthouse, on TP pole DR 19 Special Interest NW 2.8 Long Beach Rd. on TP pole DR 20 Special Interest NNW 0.3 On Site, north of Overlook, behind jersey wall, on pole DR 21 Control WNW 12.1 Emergency Operations Facility, at air sampler DR 22 Control S

7.8 Solomons Isl., across road from Science College, on TP pole DR 23 Control ENE 7.7 Taylors Island, Andersons Property, on TP pole DR30 ISFSI NW 0.2 Meteorological Station SFDR1 ISFSI SW 0.1 Southwest of ISFSI SFDR2 ISFSI N

0.1 North of ISFSI SFDR3 ISFSI N

0.1 North of ISFSI SFDR4 ISFSI NE

<0.1 Northeast of ISFSI SFDR5 ISFSI E

<0.1 East of ISFSI SFDR6 ISFSI ESE 0.1 East Southeast of ISFSI SFDR7 ISFSI N

0.5 CCNPP Visitors Center SFDR8 ISFSI NNW 0.1 North Northwest of ISFSI

Annual Radiological Environmental Operating Report YEAR: 2024 Page 16 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 5: REMP and ISFSI Sampling Locations - Direct Radiation Site #

Location Type Sector Distance (Miles)1 Description SFDR9 ISFSI SSE 0.1 South Southeast of ISFSI SFDR10 ISFSI NW 0.1 Northwest of ISFSI SFDR11 ISFSI WNW 0.1 West Northwest of ISFSI SFDR12 ISFSI WSW

<0.1 West Southwest of ISFSI SFDR13 ISFSI S

<0.1 South of ISFSI SFDR14 ISFSI SE 0.1 Southeast of ISFSI SFDR15 ISFSI ENE

<0.1 East Northeast of ISFSI SFDR16 ISFSI SW

<0.1 Southwest of ISFSI SFDR17 ISFSI NNE 0.1 North Northeast of ISFSI SFDR18 ISFSI W

< 0.1 West of ISFSI 1 Distance and direction from the central point of the two containment buildings except when designated as ISFSI which are distance and direction to the centerpoint of the ISFSI.

Common to REMP and ISFSI

Annual Radiological Environmental Operating Report YEAR: 2024 Page 17 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 6.0 MAPS OF COLLECTION SITES Figure 2: REMP Sample Locations (Near Field/Site Boundary)

Annual Radiological Environmental Operating Report YEAR: 2024 Page 18 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 3: REMP Sample Locations (Far Field)

Annual Radiological Environmental Operating Report YEAR: 2024 Page 19 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 4: REMP Nearest Residence and Garden Locations

Annual Radiological Environmental Operating Report YEAR: 2024 Page 20 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 7.0 REPORTING LEVELS FOR RADIOACTIVITY CONCENTRATIONS IN ENVIRONMENTAL SAMPLES Table 6: Reporting Levels for Radioactivity Concentrations in Environmental Samples Radionuclide Water (pCi/L)

Air Particulates or Gases (pCi/m3)

Fish (pCi/Kg-wet)

Milk (pCi/L)

Food Products (pCi/Kg-wet)

H-3 20,000 (1)

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

100 Cs-134 30 10 1,000 60 1,000 Cs-137 50 20 2,000 70 2,000 Ba-La-140 200 300 Table 7: Lower Limits of Detection for Environmental Sample Analysis Radionuclide Water (pCi/L)

Air Particulates or Gases (pCi/m3)

Fish (pCi/Kg-wet)

Milk (pCi/L)

Food Products (pCi/Kg-wet)

Sediment (pCi/Kg-dry)

Gross Beta 4.0 0.01 H-3 2,000 (3)

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

60 Cs-134 15 0.05 130 15 60 150 Cs-137 18 0.06 150 18 80 180 Ba-La-140 15 15 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/l may be used 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/l may be used

Annual Radiological Environmental Operating Report YEAR: 2024 Page 21 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 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. Calvert Cliffs Nuclear Power Plant (CCNPP)

Radiological Effluent Control (REC) Program was established to limit the quantities of radioactive material that may be released based on calculated radiation doses or dose rates. Dose to Members of the Public due to radioactive materials released from the plant is limited by Appendix I of 10 CFR 50 and by 40 CFR 190. Operational doses to the public during 2024 were calculated to be very small compared to the limits required by regulation and compared to other sources of radiation dose and pose no health hazard.

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 (MDD), 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. MDD 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.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 22 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant During the calendar year 2024, a total of 42 REMP and ISFSI locations were monitored and data analyzed in accordance with the requirements in Table 1, Radiological Environmental Monitoring Program - Direct Radiation. Monitoring station locations are described in Table 5. REMP and ISFSI Sampling Locations -

Direct Radiation. Attachment 4, Environmental Direct Radiation Dosimetry Results, provides the annual direct radiation dosimetry analyses. There was one location, DR04, where dosimeters were lost during the quarter and no data could be collected.

This deviation is described in Table 9 Sample Deviation Summary.

There was no Facility-related dose detected at any of the 20 REMP indicator locations, DR01-DR20, in 2024 as a result of the operation of Units 1 and 2. There is a slight bias towards higher exposure at the 3 control locations, DR21, DR22, and DR23. This is due to higher natural background radiation at DR23 (Taylor's Island, 7.8 miles from CCNPP). This slight bias is due to normal variations in background radiation levels and is consistent with pre-operational data.

Facility-related dose was detected at 8 of the 19 indicator locations, NE of ISFSI (sample code SFDR4); East of ISFSI (sample code SFDR5); ESE of ISFSI (sample code SFDR6); SSE of ISFSI (sample code SFDR9); South of ISFSI (sample code SFDR13); SE of ISFSI (sample code SFDR14); ENE of ISFSI (sample code SFDR15); SW of ISFSI (sample code SFDR16). This is expected as additional spent fuel casks are generally installed at the ISFSI each year. The ISFSI OSLDs are located directly around the perimeter of the ISFSI. Due to the proximity of these OSLDs to the spent fuel storage structures, they detect the small increase in radiation exposure each year as compared to the control location, Visitors Center (SFDR07).

The comparison table below summarizes the observed direct radiation at the ISFSI from spent fuel casks in storage there and 5 additional spent fuel casks that were transported to the ISFSI in 2024. The observed dose in those quarters when the casks were moved is higher and returns to a lower level in the quarters when no casks are being added to the ISFSI. It is clear from a review of the data in, Environmental Direct Radiation Dosimetry Results, that there is no observable direct radiation exposure to the public from the ISFSI, as the other REMP dosimeters (on-site, 4 miles, and beyond) show no observable increase in exposure when compared to control Dosimeters.

2024 ISFSI Facility-related Dose Quarterly (91-Day) Summary Location Type Mean Exposure (mrem) Range (mrem)

Indicator Locations 72.6 21.9 - 174 Control Location Not Detected N/A Highest Overall Location (SFDR14) 174 79.1 - 332

Annual Radiological Environmental Operating Report YEAR: 2024 Page 23 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 8.2 Air Particulate and Radioiodine Sample Results Air particulate filters and charcoal canisters were collected from locations specified in Table 2, Radiological Environmental Monitoring Program and ISFSI - Airborne.

During the calendar year 2024, a total of 972 samples were collected and analyzed for gross beta, gamma emitters and iodine. This includes 52 additional samples for radioiodine at SFA2 which are not required by the ISFSI or REMP but are included in sampling schedule for additional background monitoring of the site. 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. Radioiodine (I-131) analysis is performed weekly on radioiodine sample cartridges.

All radioiodine samples were below the detection limit.

All air particulate samples contained detectable amounts of naturally occurring radionuclides within trend as compared to the control location. Gross beta activity at REMP indicator locations averaged 2.01E-2 pCi/m3 and ranged from 6.72E-3 to 5.09E-2 pCi/m3. This is comparable with the REMP control location A5 which averaged 2.09E-2 pCi/m3 and ranged from 6.93E-3 to 3.98E-2 pCi/m3.

Specific to the ISFSI, Gross beta activity at indicator locations averaged 2.03E-2 pCi/m3 and ranged from 7.18E-3 to 4.80E-2 pCi/m3. This is comparable with the ISFSI control location SFA2 which averaged 1.97E-2 pCi/m3 and ranged from 7.16E-3 to 3.73E-2 pCi/m3.

Gamma spectrometric analyses of all quarterly composited air particulate weekly samples exhibited no detectable concentrations of any plant-related radionuclides in any of these samples. Naturally occurring radionuclides, such as Be-7, were detected in nearly all samples.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 24 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 5: 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 annual averages as shown in Figure 5, and there were no significant changes in the baseline.

8.3 Waterborne Sample Results CCNPP is located on the shore of the Chesapeake Bay which is a brackish water source. As such there is no drinking water pathway for potential exposure to the public. There is also no groundwater pathway that could result in exposure to the public. There is contained onsite a geological groundwater system which is monitored as part of the onsite radiological groundwater monitoring program that is discussed in section 11.1 of this report.

8.3.1 Surface Water (i.e., Bay, Lake etc.)

Composite water samples are collected monthly at the upstream control location, CCNPP Intake (Wa1), and at the downstream indicator location, CCNPP Discharge (Wa2). 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 24 surface water samples were collected and analyzed in accordance with the requirements in the ODCM and shown in Table 3, Radiological Environmental Monitoring Program -

Waterborne. Tritium was detected in one sample during the year.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 25 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant At the CCNPP Discharge (Wa2), collected from 12/28/2023 to 03/29/2024, tritium was observed at 740 +/- 156pCi/L and is well below the reporting level of 20,000pCi/L.

There were no other samples with detectable quantities of tritium.

Figure 6 compares tritium observed in the plant discharge and intake with annual effluent releases as reported in the Radioactive Effluent Release Report. Monthly analyses of bay water samples from both locations for gamma emitters exhibited no detectable concentrations of any plant-related radionuclides. There is no drinking water pathway for tritium in the brackish Chesapeake Bay water.

Figure 6: Surface Water Tritium Results 8.3.2 REMP Shoreline Sediment Shoreline sediment collections were made in June and October 2024 and analyzed for gamma-emitting isotopes. The semiannual samples are collected at one location at Barge Road (Wb1). A total of 2 shoreline samples were analyzed in accordance with requirements in the ODCM and shown in Table 3, Radiological Environmental Monitoring Program and ISFSI - Waterborne and Terrestrial.

Gamma spectrometric analyses of these samples exhibited naturally occurring radionuclides, but no detectable concentration of any plant-related radionuclides.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 26 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 8.3.3 Bottom Sediment Bottom sediment collections were made in June and October 2024 and analyzed for gamma-emitting isotopes. The semiannual samples are collected at two locations at CCNPP Discharge Area (WBS2) 0.2 miles from the centerpoint of units 1 and 2 in the North sector. The second location is at Camp Conoy/Rocky Point (WBS4) 1.9 miles from the centerpoint of units 1 and 2 in the SE sector. A total of 4 bottom sediment samples were analyzed as supplemental monitoring and shown in Table 3, Radiological Environmental Monitoring Program and ISFSI - Waterborne and Terrestrial.

Gamma spectrometric analyses of these samples exhibited naturally occurring radionuclides, but no detectable concentration of any plant-related radionuclides.

8.4 Ingestion Pathway Sample Results 8.4.1 Fish A total of 4 fish samples were collected in 2024. These samples were analyzed for gamma emitting radionuclides in edible portions, in accordance with requirements of the ODCM and summarized in Table 4, Radiological Environmental Monitoring Program - Ingestion. These samples are collected from the indicator and control areas as required by the ODCM. Only the edible portions are analyzed excluding head, tail, bones.

Samples of fish, when in season, are normally collected from the Discharge Area (sample codes IA1 and IA2) and from the Patuxent River (sample codes IA4 and IA5). As shown in Table 13, Spanish Mackerel and Blue Fish were obtained to meet the annual requirement.

Gamma spectrometric analyses of the fish exhibited naturally occurring K-40 but no detectable concentrations of any plant-related radionuclides.

8.4.2 Invertebrates - Oysters A total of 8 oyster samples were collected in 2024. These samples were analyzed for gamma emitting radionuclides in edible portions, in accordance with requirements of the ODCM and summarized in Table 4, Radiological Environmental Monitoring Program - Ingestion. These samples are collected from the indicator and control areas as required by the ODCM. Only the edible portions are analyzed excluding shell fragments.

Oyster samples were obtained quarterly from Camp Conoy (sample code IA3) to the south and Kenwood Beach (IA6) to the north.

Gamma spectrometric analyses of the oysters exhibited naturally occurring K-40 but no detectable concentrations of any plant-related radionuclides.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 27 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 8.4.3 Food Products - Leafy Vegetation In accordance with the ODCM and as described in Table 4, Radiological Environmental Monitoring Program - Ingestion, 36 broad leaf vegetation samples were collected from growing locations nearest site boundary in areas of highest predicted annual average ground level D/Q. Samples are collected and analyzed for gamma emitters and I-131 from the indicator and control locations monthly during growing season. It is common to detect Cs-137 in broadleaf samples at both indicator and control locations. Cs-137 can be attributed to offsite sources such as weapons testing, Chernobyl, and Fukushima events. While Cs-137 is periodically found in vegetation samples, the historical relationship between the indicator and control locations demonstrate that the plant is not the source of activity detected.

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. 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 the nearest milk animal, the nearest residence and the nearest garden of greater than 50 m2 (500 ft2) producing broad leaf vegetation.

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 Land Use Census was performed as required in the 9 meteorological sectors over land. The locations for nearest residence did not change following the 2024 census. The nearest garden in the WNW sector changed in 2024 from 1.7 miles to 1.9 miles from the center line of containment. There are no animals producing milk for public consumption within the 5-mile radius. There were goats observed at three farms in SW, SSW, and a farm that spans the W and WNW sectors. They were identified as family pets and not used for milk, or dairy consumption. One of the farms did identify that goats were occasionally used for meat consumption. Beef cattle were identified at five farms in the SSW, S, WSW, and a farm that spans the W and WNW sectors. There are no cows producing milk for human consumption within the 5-mile radius. There is no evidence of licensed milk-producing farm animals inside the 10-mile Emergency Planning Zone (EPZ). This was confirmed with the local agricultural officials of the Calvert County Farm Bureau and Government.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 28 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 8: Land Use Census - Nearest Receptors within 5 miles Sector Direction Nearest Residence (Miles)

Nearest Garden (Miles)

A N

ND ND B

NNE ND ND C

NE ND ND D

ENE ND ND E

E ND ND F

ESE ND ND G

SE 1.5 4.5 H

SSE 1.6 3.9 J

S 1.6 1.8 K

SSW 1.6 2.2 L

SW 1.1 2.4 M

WSW 1.2 1.5 N

W 1.3 1.4 P

WNW 1.7 1.9*

Q NW 2.0 2.1 R

NNW ND ND ND is used to designate sectors over water. Due to CCNPPs proximity to the Chesapeake Bay, the sectors do not have land use receptors so there is No Data (ND).

An asterisk denotes a change in this sector since the 2023 Land Use Census 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.

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).

Annual Radiological Environmental Operating Report YEAR: 2024 Page 29 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 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 and Analysis Location Collection Date or Period Reason for not conducting REMP sampling as required by ODCM Plans for preventing reoccurrence OSLD /

Dosimetry DR04 Quarter 1 2024 Dosimeters and cage were missing on arrival for servicing due to the telephone pole they were placed on had been replaced during the quarter.

Entered into corrective action tracking to document occurrence.

11.0 OTHER SUPPLEMENTAL INFORMATION 11.1 NEI 07-07 Onsite Radiological Groundwater Monitoring Program Calvert Cliffs Nuclear Power Plant 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 Attachment 5, Table 15 Radiological Groundwater Protection Program.

11.2 Independent Spent Fuel Storage Installation (ISFSI) Monitoring Program In August 1990 BGE initiated a program of additional radiological environmental monitoring around the site for the Independent Spent Fuel Storage Installation (ISFSI). The first dry fuel storage canister was loaded into the ISFSI in November of 1993 with more canisters being loaded in subsequent years. In 2021, the site transitioned to Holtec Hi-storm (Holtec International Storage Module) vertically ventilated storage overpack system for Independent Spent Fuel Storage installation.

In 2024 there were five such canisters of spent fuel transferred to the ISFSI.

Results of the monitoring program for the ISFSI for the current period are included in this report. The results were compared with that generated during the previous ISFSI pre-operational periods and the current and previous CCNPP REMP periods.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 30 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant In 2024 there were 280 analysis performed on 260 weekly composite air particulate filter samples were collected from five locations during the period. These locations are On Site Before the Entrance to Camp Conoy (sample code A1), Meteorological Station (sample code SFA1), CCNPP Visitors Center (sample code SFA2), NNW of the ISFSI (sample code SFA3), and SSE of the ISFSI (sample code SFA4). Sample locations A1, SFA1, SFA3, and SFA4 are in common with CCNPP REMP Program as shown in Table 2. Radiological Environmental Monitoring Program and ISFSI -

Airborne. All samples were analyzed for beta radioactivity and gamma emitting radionuclides.

Weekly analyses for beta activity on air particulate filters collected from all five locations showed values characteristic of levels routinely observed in the REMP.

These values ranged from 7.18E-3 to 4.80E-2 pCi/m3 for the indicator locations and 7.16E-3 to 3.73E-2 pCi/m3 for the control location. The location with the highest overall mean of 2.11E-2 pCi/m3 was SFA4, SSW of the ISFSI.

Gamma spectrometric analyses of the quarterly composite filter samples exhibited naturally occurring radionuclides, but no detectable concentration of any plant-related radionuclides.

A total of 40 vegetation and soil samples were analyzed from locations shown in Table 3, Radiological Environmental Monitoring Program and ISFSI - Waterborne and Terrestrial. The terrestrial environment was monitored by analyzing 5 samples of vegetation, SFB1, SFB2, SFB3, SFB4, SFB5 and 5 samples of soil, SFS1, SFS2, SFS3, SFS4, SFS5 collected quarterly from the vicinity of the air sampling locations surrounding the ISFSI.

No detectable concentrations of plant-related radionuclides were found in any of these samples. Naturally occurring radionuclides such as K-40 were detected in all samples.

A network of OSLDs is deployed quarterly at 19 indicator locations and one control location as shown in Table 1, Radiological Environmental Monitoring Program and ISFSI - Direct Radiation. The ISFSI locations are SFDR1-SFDR6, SFDR8-SFDR18, DR30 placed around the perimeter of the ISFSI. In addition, DR7 (On Site Before the Entrance to Camp Conoy) is common to both the CCNPP REMP Program and the ISFSI Program. The control location at the Visitors Center, SFDR7. Details of these results are discussed in 8.1 Direct Radiation of this report and data reported in Environmental Direct Radiation Dosimetry Results.

11.3 Corrections to Previous Reports There are no errata to report at this time.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 31 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant 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 Power Plants,"

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 InitiativeFinal Guidance Document,," Nuclear Energy Institute, Washington, D.C..

Annual Radiological Environmental Operating Report YEAR: 2024 Page 32 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

[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] "NEI 07-07, Industry Ground Water Protection InitiativeFinal Guidance Document, Rev. 1,"

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

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

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

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

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

[27] "NRC Resource Page," [Online]. Available: http://www.nrc.gov/about-nrc/radiation.html.

[Accessed 10 November 2020].

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

Nuclear Regulatory Commission, 1987.

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

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

[31] "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.

[32] "10 CFR 50 - Domestic Licensing of Production and Utilization Facilities," US Nuclear Regulatory Commission, Washington, DC.

[33] "40 CFR 190 - Environmental Radiation Protection Standards for Nuclear Power Operation," US Environmental Protection Agency, Washington, DC.

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

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

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

[36] "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.

[37] "40 CFR 141 - National Primary Drinking Water Regulations," US Environmental Protection Agency, Washington, DC.

[38] "10 CFR 20 - Standards for Protection Against Radiation," US Nuclear Regulatory Commission, Washington, DC.

[39] Cohen, L. K., Preoperational Environmental Radioactivity Monitoring Program at Calvert Cliffs Units 1 and 2, NUS No. 882 Semiannual Report January-June 1971, December 1971; NUS No.

1025 Annual Report 1971, March 1973.

[40] Cohen, L. K., Preoperational Environmental Radioactivity Monitoring Program at Calvert Cliffs Units 1 and 2, NUS No. 1137 Annual Report 1972, December 1973.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 33 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

[41] Cohen, L. K. and Malmberg, M.S., Preoperational Environmental Radioactivity Monitoring Program at Calvert Cliffs Units 1 and 2, NUS No. 1188, Annual Report 1973, October 1974.

[42] Malmberg, M. S., Preoperational Environmental Radioactivity Monitoring Program at Calvert Cliffs Units 1 and 2, NUS No. 1333, Data Summary Report, September 1970 to September 1974, July 1975

[43] Calvert Cliffs Nuclear Power Plant, Units 1 and 2, License Nos. DPR-53 and DPR-69, Technical Specification 5.6.2; Annual Radiological Environmental Operating Report.

[44] CY-CA-170-301 Current Revision, Offsite Dose Calculation Manual for the Calvert Cliffs Nuclear Power Plant.

[45] CY-AA-170-1000, Radiological Environmental Monitoring Program (REMP) and Meteorological Program Implementation.

[46] Baltimore Gas and Electric Company, Radiological Environmental Monitoring Program Pre-Operational Report for the Calvert Cliffs Independent Spent Fuel Storage Installation, August 1990 - November 1993, February 1994.

[47] Calvert Cliffs Independent Spent Fuel Storage Installation Technical Specifications, Appendix A to Materials License SNM-2505

[48] Land Use Census Around Calvert Cliffs Nuclear Power Plant, August 2024.

[49] EN-CA-408-4160 Current Revision, RGPP Reference Material for Calvert Cliffs

[50] Teledyne Brown Engineering Environmental Services. "4th Quarter 2024 Quality Assurance Report", January - December 2024.

[51] AMO Environmental Decisions, "2024 Annual RGPP Monitoring Report Summary of Results and Conclusions Calvert Cliffs Generating Station Lusby, Maryland

Annual Radiological Environmental Operating Report YEAR: 2024 Page 34 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

, Data Table Summary Medium or Pathway Sampled (Units)

Type, Total Number of Analyses performed (e.g., I-131, 400)

Lower Limit of Detection (LLD)

Indicator Mean5; (f6).

Range5 Location with Highest Annual Mean Control Mean5 (f6).

Range5 Number of Nonroutine Reported Measurements Name Distance and Direction Mean5 (f6)

Range5 Air Particulates (pCi/m3) REMP Beta, 416 0.01 2.01E-2 (364/364) 6.72E 5.09E-2 SFA4 SSE of ISFSI.

0.5 miles SSW 2.11 (52/52) 9.18E 4.06E-2 2.09E-2 (52/52) 6.93E-3 - 3.98E-2 0

Air Particulates (pCi/m3) ISFSI Beta, 260 0.01 2.03E-2 (208/208) 7.18E 4.80E-2 SFA4 SSE of ISFSI.

0.5 miles SSW 2.11 (52/52) 9.18E 4.06E-2 1.97E-2 (52/52) 7.16E-3 - 3.73E-2 0

Direct Radiation (mrem/qtr.)

Gamma Dose, 334 N/A 33.0 (64/304) 9.41 - 192 SFDR14 SSE of ISFSI 0.1miles SE 192(8/8) 97.1 - 350 13.0 (16/16) 11.3 - 16.2 0

Surface Water (pCi/L)

Tritium, 8 200 740 (1/4) 740 +/- 156 Wa2 CCNPP Discharge 0.2 miles N 740 (1/4) 740 +/- 156

<MDA 0

5 Mean and range are based on detectable measurements only.

6 Fraction of detectable measurements at specified locations is indicated in parentheses.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 35 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

, Complete Data Table for All Analysis Results Obtained In 2024 Due to the overall complexity and variation in REMP designs across the industry, it is not feasible to prescribe a certain format that will fit all situations at a given plant or across the industry.

The expectation for all licensees is to present data in an understandable format, that allows for trending of results over time. Sample results are grouped within tables by sample frequency and media type and sorted by sample period:

1.

Table 10: Monthly Waterborne Sample Results

2.

Table 11 Weekly Airborne Sample Results

3.

Table 12 Quarterly Isotopic Sample Results

4.

Table 13 Complete REMP Results

Annual Radiological Environmental Operating Report YEAR: 2024 Page 36 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 10: Monthly Sampling Bay Water (pCi/L) and Garden Vegetation (pCi/kg)

Monthly Radionuclides in Bay Water (pCi/L)

Location WA1 (Intake)

WA2 (Discharge)

Date Gamma Emitters Tritium 1 Gamma Emitters Tritium 1 1/31/2024 740 +/- 156 3/1/2024 3/29/2024 4/30/2024 5/31/2024 6/28/2024 8/1/2024 8/30/2024 9/27/2024 11/1/2024 11/29/2024 1/2/2025

All Non-Natural Radionuclides <MDA 1 Monthly samples composited for a Quarterly Tritium analysis

Annual Radiological Environmental Operating Report YEAR: 2024 Page 37 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 10 Continued: Monthly Sampling Bay Water (pCi/L) and Vegetation (pCi/kg)

Monthly Radionuclides in Vegetation (pCi/kg)

Sample Code Date Sample Type Gamma Emitters IB4 6/24/2024 Kale (Control) 7/22/2024 Kale 8/19/2024 Kale 9/16/2024 Kale IB5 6/24/2024 Cabbage (Control) 7/22/2024 Cabbage 8/19/2024 Cabbage 9/16/2024 Cabbage IB6 6/24/2024 Collards (Control) 7/22/2024 Collards 8/19/2024 Collards 9/16/2024 Collards IB7 6/24/2024 Kale 7/22/2024 Kale 8/19/2024 Kale 9/16/2024 Kale IB8 6/24/2024 Cabbage 7/22/2024 Cabbage 8/19/2024 Cabbage 9/16/2024 Cabbage

Annual Radiological Environmental Operating Report YEAR: 2024 Page 38 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 10 Continued: Monthly Sampling Bay Water (pCi/L) and Vegetation (pCi/kg)

Monthly Radionuclides in Vegetation (pCi/kg)

Sample Code Date Sample Type Gamma Emitters IB9 6/24/2024 Collards 7/22/2024 Collards 8/19/2024 Collards 9/16/2024 Collards IB10 6/24/2024 Kale 7/22/2024 Kale 8/19/2024 Kale 9/16/2024 Kale IB11 6/24/2024 Cabbage 7/22/2024 Cabbage 8/19/2024 Cabbage 9/16/2024 Swiss Chard IB12 6/24/2024 Collards 7/22/2024 Collards 8/19/2024 Collards 9/16/2024 Collards

All Non-Natural Radionuclides <MDA

Annual Radiological Environmental Operating Report YEAR: 2024 Page 39 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 11: Weekly Air Monitoring Particulate and I-131 Filters (pCi/m3)

Weekly Air Monitoring Particulate Filters (pCi/m3)

A1 A2 A3 A4 A5 (Control)

Date Gross Beta Activity (2-)

Gross Beta Activity (2-)

1/8/2024 1.80E-02 1.34E-03 1.73E-02 1.36E-03 1.48E-02 1.28E-03 1.61E-02 1.32E-03 1.66E-02 1.35E-03 1/16/2024 2.65E-02 1.40E-03 2.52E-02 1.36E-03 2.45E-02 1.37E-03 2.47E-02 1.38E-03 2.36E-02 1.32E-03 1/22/2024 2.45E-02 1.60E-03 2.36E-02 1.60E-03 2.17E-02 1.58E-03 2.35E-02 1.63E-03 2.39E-02 1.60E-03 1/29/2024 1.06E-02 1.06E-03 1.11E-02 1.09E-03 1.06E-02 1.09E-03 9.33E-03 1.05E-03 1.22E-02 1.12E-03 2/5/2024 1.67E-02 1.24E-03 1.48E-02 1.20E-03 1.42E-02 1.21E-03 1.34E-02 1.18E-03 1.63E-02 1.24E-03 2/12/2024 1.78E-02 1.25E-03 1.84E-02 1.27E-03 1.70E-02 1.22E-03 1.88E-02 1.29E-03 1.77E-02 1.26E-03 2/19/2024 2.40E-02 1.44E-03 2.20E-02 1.39E-03 2.13E-02 1.38E-03 2.16E-02 1.38E-03 2.14E-02 1.35E-03 2/26/2024 2.42E-02 1.45E-03 2.40E-02 1.45E-03 2.07E-02 1.36E-03 2.44E-02 1.45E-03 2.55E-02 1.51E-03 3/4/2024 1.94E-02 1.30E-03 2.00E-02 1.34E-03 1.86E-02 1.28E-03 2.00E-02 1.34E-03 2.04E-02 1.35E-03 3/11/2024 7.92E-03 9.49E-04 6.72E-03 9.01E-04 7.12E-03 9.68E-04 7.86E-03 9.46E-04 6.93E-03 9.10E-04 3/18/2024 2.85E-02 1.56E-03 2.74E-02 1.54E-03 2.57E-02 1.50E-03 2.66E-02 1.52E-03 2.77E-02 1.56E-03 3/25/2024 1.57E-02 1.18E-03 1.72E-02 1.24E-03 1.60E-02 1.19E-03 1.63E-02 1.20E-03 1.60E-02 1.20E-03 4/1/2024 2.07E-02 1.34E-03 1.72E-02 1.26E-03 2.04E-02 1.35E-03 1.84E-02 1.29E-03 1.94E-02 1.34E-03 4/8/2024 8.36E-03 1.01E-03 8.03E-03 9.80E-04 7.69E-03 9.68E-04 8.46E-03 9.96E-04 7.91E-03 9.68E-04 4/15/2024 1.73E-02 1.23E-03 1.68E-02 1.23E-03 1.59E-02 1.20E-03 1.66E-02 1.22E-03 1.73E-02 1.24E-03 4/22/2024 1.80E-02 1.28E-03 1.74E-02 1.27E-03 1.56E-02 1.21E-03 1.69E-02 1.26E-03 1.64E-02 1.25E-03 4/29/2024 1.97E-02 1.30E-03 1.98E-02 1.31E-03 1.88E-02 1.29E-03 1.91E-02 1.29E-03 1.83E-02 1.28E-03 5/6/2024 1.60E-02 1.20E-03 1.45E-02 1.18E-03 1.44E-02 1.16E-03 1.49E-02 1.19E-03 1.51E-02 1.20E-03 5/13/2024 1.19E-02 1.08E-03 1.18E-02 1.14E-03 1.11E-02 1.08E-03 1.26E-02 1.13E-03 1.17E-02 1.12E-03 5/20/2024 1.28E-02 1.12E-03 1.25E-02 1.12E-03 1.28E-02 1.12E-03 1.20E-02 1.11E-03 1.18E-02 1.11E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 40 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Weekly Air Monitoring Particulate Filters (pCi/m3)

A1 A2 A3 A4 A5 (Control)

Date Gross Beta Activity (2-)

Gross Beta Activity (2-)

5/28/2024 1.93E-02 1.19E-03 1.71E-02 1.28E-03 1.66E-02 1.13E-03 1.80E-02 1.18E-03 2.02E-02 1.26E-03 6/3/2024 1.93E-02 1.45E-03 1.67E-02 1.38E-03 1.66E-02 1.37E-03 1.88E-02 1.45E-03 1.80E-02 1.46E-03 6/10/2024 1.95E-02 1.35E-03 1.85E-02 1.32E-03 1.76E-02 1.29E-03 1.86E-02 1.32E-03 1.85E-02 1.35E-03 6/17/2024 1.67E-02 1.25E-03 1.65E-02 1.26E-03 1.45E-02 1.19E-03 1.66E-02 1.26E-03 1.71E-02 1.27E-03 6/24/2024 1.67E-02 1.27E-03 1.63E-02 1.26E-03 1.30E-02 1.17E-03 1.44E-02 1.21E-03 1.53E-02 1.25E-03 7/1/2024 1.57E-02 1.19E-03 1.74E-02 1.27E-03 1.47E-02 1.19E-03 1.48E-02 1.19E-03 1.76E-02 1.32E-03 7/8/2024 2.02E-02 1.38E-03 1.88E-02 1.33E-03 1.68E-02 1.29E-03 1.78E-02 1.31E-03 2.00E-02 1.39E-03 7/15/2024 1.62E-02 1.24E-03 1.44E-02 1.20E-03 1.44E-02 1.20E-03 1.43E-02 1.20E-03 1.59E-02 1.26E-03 7/22/2024 3.19E-02 1.66E-03 3.01E-02 1.64E-03 2.44E-02 1.50E-03 3.10E-02 1.63E-03 2.81E-02 1.57E-03 7/29/2024 1.92E-02 1.32E-03 1.63E-02 1.25E-03 1.67E-02 1.26E-03 1.68E-02 1.27E-03 1.76E-02 1.31E-03 8/5/2024 2.41E-02 1.46E-03 2.37E-02 1.46E-03 2.29E-02 1.44E-03 2.40E-02 1.47E-03 2.33E-02 1.45E-03 8/12/2024 1.73E-02 1.29E-03 1.56E-02 1.24E-03 1.52E-02 1.24E-03 1.39E-02 1.19E-03 1.67E-02 1.27E-03 8/19/2024 2.56E-02 1.49E-03 2.29E-02 1.43E-03 2.11E-02 1.38E-03 2.45E-02 1.47E-03 2.46E-02 1.47E-03 8/26/2024 1.99E-02 1.35E-03 1.71E-02 1.28E-03 1.61E-02 1.25E-03 1.76E-02 1.29E-03 1.82E-02 1.31E-03 9/3/2024 3.32E-02 1.55E-03 2.68E-02 1.41E-03 2.82E-02 1.44E-03 2.87E-02 1.45E-03 3.07E-02 1.50E-03 9/9/2024 1.61E-02 1.36E-03 1.49E-02 1.33E-03 1.30E-02 1.26E-03 1.49E-02 1.33E-03 1.44E-02 1.31E-03 9/16/2024 3.19E-02 1.63E-03 3.07E-02 1.62E-03 3.07E-02 1.61E-03 3.26E-02 1.65E-03 3.50E-02 1.70E-03 9/23/2024 1.90E-02 1.30E-03 1.95E-02 1.39E-03 1.98E-02 1.33E-03 1.87E-02 1.31E-03 2.14E-02 1.39E-03 9/30/2024 1.13E-02 1.05E-03 1.38E-02 1.12E-03 1.38E-02 1.14E-03 1.10E-02 1.05E-03 1.12E-02 1.05E-03 10/7/2024 2.32E-02 1.40E-03 2.22E-02 1.38E-03 2.18E-02 1.37E-03 2.18E-02 1.39E-03 2.08E-02 1.36E-03 10/14/2024 4.24E-02 1.85E-03 5.09E-02 1.97E-03 3.94E-02 1.77E-03 3.69E-02 1.72E-03 3.98E-02 1.75E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 41 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Weekly Air Monitoring Particulate Filters (pCi/m3)

A1 A2 A3 A4 A5 (Control)

Date Gross Beta Activity (2-)

Gross Beta Activity (2-)

10/21/2024 1.86E-02 1.31E-03 1.80E-02 1.29E-03 1.80E-02 1.29E-03 1.66E-02 1.26E-03 1.75E-02 1.27E-03 10/28/2024 3.35E-02 1.70E-03 3.09E-02 1.63E-03 3.12E-02 1.64E-03 3.39E-02 1.69E-03 3.71E-02 1.76E-03 11/4/2024 2.34E-02 1.46E-03 3.33E-02 1.66E-03 2.41E-02 1.44E-03 2.71E-02 1.52E-03 3.90E-02 1.78E-03 11/11/2024 1.97E-02 1.35E-03 1.98E-02 1.35E-03 1.86E-02 1.32E-03 2.14E-02 1.42E-03 2.35E-02 1.45E-03 11/18/2024 1.63E-02 1.24E-03 1.51E-02 1.21E-03 1.66E-02 1.28E-03 1.63E-02 1.25E-03 1.95E-02 1.33E-03 11/25/2024 2.99E-02 1.57E-03 2.97E-02 1.57E-03 3.22E-02 1.62E-03 2.94E-02 1.56E-03 3.34E-02 1.65E-03 12/2/2024 3.43E-02 1.67E-03 3.05E-02 1.59E-03 3.12E-02 1.60E-03 3.34E-02 1.65E-03 3.27E-02 1.64E-03 12/9/2024 2.73E-02 1.53E-03 2.59E-02 1.48E-03 2.41E-02 1.44E-03 2.87E-02 1.55E-03 2.78E-02 1.53E-03 12/16/2024 2.43E-02 1.44E-03 2.23E-02 1.39E-03 2.42E-02 1.44E-03 2.47E-02 1.45E-03 2.49E-02 1.46E-03 12/23/2024 1.75E-02 1.27E-03 1.48E-02 1.19E-03 1.64E-02 1.23E-03 1.68E-02 1.25E-03 1.66E-02 1.24E-03 12/30/2024 2.14E-02 1.38E-03 2.06E-02 1.38E-03 2.22E-02 1.41E-03 2.09E-02 1.36E-03 2.34E-02 1.43E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 42 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 11 Continued: Weekly Air Monitoring Particulate Filters (pCi/m3)

SFA1 SFA2 (ISFSI Control)

SFA3 SFA4 Date Gross Beta Activity (2-)

Gross Beta Activity (2-)

1/8/2024 1.55E-02 1.30E-03 1.62E-02 1.29E-03 1.48E-02 1.27E-03 1.63E-02 1.28E-03 1/16/2024 2.51E-02 1.37E-03 2.42E-02 1.33E-03 2.43E-02 1.35E-03 2.33E-02 1.24E-03 1/22/2024 2.44E-02 1.61E-03 2.44E-02 1.58E-03 2.28E-02 1.57E-03 2.42E-02 1.56E-03 1/29/2024 9.89E-03 1.05E-03 1.00E-02 1.01E-03 9.68E-03 1.04E-03 1.06E-02 1.01E-03 2/5/2024 1.43E-02 1.18E-03 1.40E-02 1.18E-03 1.44E-02 1.19E-03 1.57E-02 1.22E-03 2/12/2024 1.77E-02 1.26E-03 1.70E-02 1.24E-03 1.71E-02 1.24E-03 2.33E-02 1.41E-03 2/19/2024 2.03E-02 1.34E-03 2.22E-02 1.40E-03 2.07E-02 1.35E-03 2.38E-02 1.38E-03 2/26/2024 2.29E-02 1.43E-03 2.28E-02 1.42E-03 1.96E-02 1.31E-03 2.68E-02 1.52E-03 3/4/2024 1.94E-02 1.33E-03 1.47E-02 1.17E-03 1.99E-02 1.34E-03 2.50E-02 1.47E-03 3/11/2024 7.18E-03 9.18E-04 7.16E-03 9.19E-04 8.53E-03 9.70E-04 9.79E-03 1.02E-03 3/18/2024 2.74E-02 1.54E-03 2.68E-02 1.52E-03 2.83E-02 1.56E-03 3.28E-02 1.66E-03 3/25/2024 1.53E-02 1.18E-03 1.40E-02 1.14E-03 1.60E-02 1.20E-03 2.00E-02 1.31E-03 4/1/2024 1.98E-02 1.40E-03 1.85E-02 1.29E-03 1.91E-02 1.31E-03 2.25E-02 1.39E-03 4/8/2024 8.03E-03 1.01E-03 8.58E-03 1.01E-03 7.94E-03 9.85E-04 9.18E-03 1.04E-03 4/15/2024 1.69E-02 1.23E-03 1.56E-02 1.19E-03 1.53E-02 1.18E-03 1.79E-02 1.16E-03 4/22/2024 1.47E-02 1.19E-03 1.73E-02 1.27E-03 1.65E-02 1.24E-03 1.78E-02 1.28E-03 4/29/2024 1.77E-02 1.25E-03 1.90E-02 1.29E-03 1.82E-02 1.26E-03 2.27E-02 1.40E-03 5/6/2024 1.47E-02 1.16E-03 1.49E-02 1.19E-03 1.46E-02 1.17E-03 1.65E-02 1.24E-03 5/13/2024 1.05E-02 1.01E-03 1.27E-02 1.13E-03 1.25E-02 1.12E-03 1.35E-02 1.15E-03 5/20/2024 1.02E-02 1.03E-03 1.29E-02 1.13E-03 1.24E-02 1.10E-03 1.30E-02 1.12E-03 5/28/2024 1.58E-02 1.13E-03 1.93E-02 1.22E-03 1.92E-02 1.21E-03 2.02E-02 1.22E-03 6/3/2024 1.73E-02 1.39E-03 1.92E-02 1.46E-03 2.00E-02 1.48E-03 1.98E-02 1.44E-03 6/10/2024 1.67E-02 1.27E-03 1.68E-02 1.27E-03 1.71E-02 1.28E-03 1.72E-02 1.25E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 43 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 11 Continued: Weekly Air Monitoring Particulate Filters (pCi/m3)

SFA1 SFA2 (ISFSI Control)

SFA3 SFA4 Date Gross Beta Activity (2-)

Gross Beta Activity (2-)

6/17/2024 1.49E-02 1.20E-03 1.78E-02 1.30E-03 1.77E-02 1.28E-03 1.54E-02 1.16E-03 6/24/2024 1.39E-02 1.20E-03 1.46E-02 1.45E-03 1.57E-02 1.25E-03 1.44E-02 1.21E-03 7/1/2024 1.40E-02 1.17E-03 1.55E-02 1.28E-03 1.47E-02 1.19E-03 1.60E-02 1.22E-03 7/8/2024 1.72E-02 1.31E-03 1.82E-02 1.32E-03 2.11E-02 1.40E-03 1.94E-02 1.36E-03 7/15/2024 1.25E-02 1.14E-03 1.47E-02 1.21E-03 1.64E-02 1.26E-03 1.70E-02 1.28E-03 7/22/2024 2.61E-02 1.53E-03 2.94E-02 1.60E-03 2.96E-02 1.61E-03 3.18E-02 1.66E-03 7/29/2024 1.50E-02 1.24E-03 1.78E-02 1.29E-03 1.77E-02 1.29E-03 1.93E-02 1.33E-03 8/5/2024 2.18E-02 1.41E-03 2.34E-02 1.45E-03 2.40E-02 1.47E-03 2.36E-02 1.46E-03 8/12/2024 1.29E-02 1.16E-03 1.48E-02 1.21E-03 1.38E-02 1.18E-03 1.60E-02 1.25E-03 8/19/2024 2.18E-02 1.40E-03 2.48E-02 1.48E-03 2.37E-02 1.44E-03 2.62E-02 1.50E-03 8/26/2024 1.58E-02 1.24E-03 1.67E-02 1.27E-03 1.80E-02 1.30E-03 1.87E-02 1.32E-03 9/3/2024 2.71E-02 1.43E-03 3.01E-02 1.48E-03 3.09E-02 1.50E-03 3.23E-02 1.53E-03 9/9/2024 1.27E-02 1.25E-03 1.36E-02 1.48E-03 1.43E-02 1.31E-03 1.42E-02 1.31E-03 9/16/2024 4.80E-02 2.01E-03 3.14E-02 1.62E-03 3.29E-02 1.65E-03 3.12E-02 1.60E-03 9/23/2024 1.66E-02 1.29E-03 1.78E-02 1.28E-03 1.85E-02 1.29E-03 1.85E-02 1.29E-03 9/30/2024 1.09E-02 1.05E-03 1.13E-02 1.07E-03 1.01E-02 1.01E-03 1.09E-02 1.03E-03 10/7/2024 2.05E-02 1.33E-03 2.06E-02 1.37E-03 2.10E-02 1.35E-03 2.29E-02 1.39E-03 10/14/2024 3.43E-02 1.67E-03 3.33E-02 1.66E-03 3.09E-02 1.60E-03 3.60E-02 1.70E-03 10/21/2024 1.96E-02 1.33E-03 1.77E-02 1.29E-03 1.21E-02 1.12E-03 1.88E-02 1.31E-03 10/28/2024 3.74E-02 1.77E-03 2.94E-02 1.61E-03 3.66E-02 1.77E-03 4.06E-02 1.83E-03 11/4/2024 2.38E-02 1.43E-03 2.24E-02 1.43E-03 2.33E-02 1.45E-03 2.28E-02 1.40E-03 11/11/2024 1.97E-02 1.35E-03 1.90E-02 1.35E-03 1.99E-02 1.36E-03 2.04E-02 1.37E-03 11/18/2024 1.82E-02 1.29E-03 1.77E-02 1.30E-03 1.78E-02 1.28E-03 1.73E-02 1.27E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 44 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 11 Continued: Weekly Air Monitoring Particulate Filters (pCi/m3)

SFA1 SFA2 (ISFSI Control)

SFA3 SFA4 Date Gross Beta Activity (2-)

Gross Beta Activity (2-)

11/25/2024 3.34E-02 1.70E-03 3.23E-02 1.66E-03 3.13E-02 1.62E-03 2.97E-02 1.57E-03 12/2/2024 3.57E-02 1.70E-03 3.73E-02 1.73E-03 3.56E-02 1.70E-03 3.01E-02 1.58E-03 12/9/2024 3.08E-02 1.58E-03 2.83E-02 1.54E-03 2.89E-02 1.57E-03 2.83E-02 1.54E-03 12/16/2024 2.55E-02 1.47E-03 2.61E-02 1.49E-03 2.45E-02 1.45E-03 2.49E-02 1.46E-03 12/23/2024 1.78E-02 1.27E-03 1.72E-02 1.26E-03 1.71E-02 1.25E-03 1.65E-02 1.24E-03 12/30/2024 2.17E-02 1.37E-03 2.29E-02 1.40E-03 2.06E-02 1.37E-03 2.23E-02 1.40E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 45 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 11 Continued: Weekly Air Monitoring Iodine131 Cartridge Filters (pCi/m3)

Date A1 A2 A3 A4 A5 (Control)

SFA1 SFA2 1 SFA3 SFA4 1/8/2024 1/16/2024 1/22/2024 1/29/2024 2/5/2024 2/12/2024 2/19/2024 2/26/2024 3/4/2024 3/11/2024 3/18/2024 3/25/2024 4/1/2024 4/8/2024 4/15/2024 4/22/2024 4/29/2024 5/6/2024 5/13/2024 5/20/2024 5/28/2024 6/3/2024 6/10/2024 6/17/2024 6/24/2024 7/1/2024 7/8/2024

Annual Radiological Environmental Operating Report YEAR: 2024 Page 46 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 11 Continued: Weekly Air Monitoring Iodine131 Cartridge Filters (pCi/m3)

Date A1 A2 A3 A4 A5 (Control)

SFA1 SFA2 1 SFA3 SFA4 7/15/2024 7/22/2024 7/29/2024 8/5/2024 8/12/2024 8/19/2024 8/26/2024 9/3/2024 9/9/2024 9/16/2024 9/23/2024 9/30/2024 10/7/2024 10/14/2024 10/21/2024 10/28/2024 11/4/2024 11/11/2024 11/18/2024 11/25/2024 12/2/2024 12/9/2024 12/16/2024 12/23/2024 12/30/2024

<MDA, Minimum Detectable Activity 1 Not a required Sample, monitored as supplemental data for continuity of programs.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 47 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 12: Quarterly isotopic data - Air (pCi/m3), Oysters (pCi/kg), and ISFSI Veg (pCi/kg wet) ISFSI Soil (pCi/kg)

Location Q1 Q2 Q3 Q4 Quarterly Air Filter Composite for Gamma Emitters (pCi/m3)

A1

<MDAs

<MDAs A2

<MDAs

<MDAs A3

<MDAs

<MDAs A4

<MDAs

<MDAs A5

<MDAs

<MDAs SFA1

<MDAs

<MDAs SFA2

<MDAs

<MDAs SFA3

<MDAs

<MDAs SFA4

<MDAs

<MDAs Quarterly Oysters for Gamma Emitters (pCi/kg-wet)

IA3

<MDA

<MDA IA6(Control)

<MDA

<MDA Quarterly ISFSI Vegetation for Gamma Emitters (pCi/kg-wet)

SFB1

<MDA

<MDA SFB2

<MDA

<MDA SFB3

<MDA

<MDA SFB4

<MDA

<MDA SFB5

<MDA

<MDA Quarterly ISFSI Soil for Gamma Emitters (pCi/kg-dry)

SFS1

<MDA

<MDA SFS2

<MDA

<MDA SFS3

<MDA

<MDA SFS4

<MDA

<MDA SFS5

<MDA

<MDA NOTE: <MDA denotes laboratory analysis detected No non-natural radionuclides at or above the ODCM required Minimum Detectable Activity

Annual Radiological Environmental Operating Report YEAR: 2024 Page 48 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 13: Complete REMP Results, Sediment and Fish Radionuclides in Sediment (pCi/kg dry)

Sample Code Sample Date Gamma Emitters WB1 4/15/2024 Shoreline at Barge Road 10/21/2024 WBS2 6/19/24 Bottom Sediment at Discharge Area 10/22/24 WBS4 6/19/24 Bottom Sediment at Camp Conoy 10/22/24 Radionuclides in Fish (pCi/kg-wet)

Sample Code Sample Date Sample Type Gamma Emitters IA1 8/14/2024 Spanish Mackerel IA2 8/27/2024 Blue Fish IA4 (Control) 8/14/2024 Blue Fish IA5 (Control) 8/14/2024 Spanish Mackerel

All Non-Natural Gamma Emitters <MDA

Annual Radiological Environmental Operating Report YEAR: 2024 Page 49 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

, Cross Check Intercomparison 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. Intercomparison 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.

Constellation Generation Solutions Laboratory participated in the following proficiency testing studies provided by Environmental Resource Associates (ERA) and Eckert Ziegler Analytics (EZA) in 2024. The Laboratorys intercomparison program results for 2024 are summarized below. is a summary of Constellation Generation Solutions (CGS) laboratorys quality assurance program. It consists of Table 14 which is a compilation of the results of the CGS laboratorys participation in an interlaboratory comparison program with Environmental Resource Associates (ERA) located in Arvada, Colorado and Eckert and Ziegler Analytics, Inc. (EZA) located in Atlanta, Georgia.

It also includes a compilation of the results of the Constellation Generation Solutions (CGS) Laboratorys participation in a split sample program with Teledyne Brown Engineering located in Knoxville, Tennessee.

The CGS laboratory's intercomparison results, are in full agreement when they were evaluated using designated acceptance ranges and the Resolution Test Criteria in accordance with the Constellation Radiochemistry Quality Control procedure, except as noted in the Pass/Fail column and described below. The CGS laboratory's results are provided with their analytical uncertainties of 2 sigma. When evaluating with the Resolution Test a one sigma uncertainty is used to determine Pass or Fail and noted accordingly. Co-located air samplers provide the opportunity to perform interlaboratory comparisons of beta particulate and radioiodine filters that due to the nature of the sample precludes them from splitting for analysis. Results of E1-2 analyzed by CGS and E1-2Q analyzed by TBE for beta particulates are provided at the end of this table for review and are generally in good agreement. The radioiodine samples collected alongside the beta particulate filters were analyzed and all were below MDA so there are no results to compare for that parameter.

All results reported passed their respective acceptance ranges and Resolution Test Criteria with the following two exceptions for the interlaboratory crosschecks:

Annual Radiological Environmental Operating Report YEAR: 2024 Page 50 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant RAD-137 I-131 water study on 04/08/2024 on Detector 6 (D6) failed high at 29.7 pCi/L for a true value of 25.1 pCi/L with an acceptance range of 21.7 - 28.5 pCi/L. This was a new detector and the study had very low area counts. Of the three runs, the other two values would have passed. Results on all other detectors were successful. Further review of the data indicated all the Ba-133 results in the other RAD-137 water study were in acceptable range. In that study, Ba-133 is meant to approximate I-131 results as it has an energy very close to I-131 in the spectrum. The detector is new in the lab and there is an ongoing review of its performance to identify the optimal operating range and any inherent bias.

E14044 Filter study on 12/05/24 failed low for Cs-134 on D6 reporting 91.3 +/- 3.25 pCi for a true value of 116 pCi. This study also had unusually low area counts in this range of the spectrum. The result did pass the acceptance range of 81.2 - 150.8 pCi, however due to the extremely low activity level, count times were extended significantly to capture other isotopes with lower yields resulting in very low uncertainties for higher yield isotopes. In the case of Cs-134 the uncertainty was less than 5% and at the level of recovery observed, the result failed the resolution test. Routine analysis is normally performed to achieve 15% +/- 5 %. Review of all other studies performed on this detector showed successful performance for Cs-134 and all other isotopes. The evaluation of detector performance is ongoing to identify inherent bias or variability at low count rates as is observed in environmental samples.

The vendor laboratory used by CGS for subcontracting and interlaboratory comparison samples, Teledyne Brown Engineering (TBE), also participates in the ERA and EZA interlaboratory comparison program. A presentation of their full data report is provided in their Annual Environmental Quality Assurance Program Reports, [50]. In summary TBE reported results met vendor and laboratory acceptance ranges with the following exceptions described here.

For TBE, the following three studies reported data that did not meet the specified acceptance criteria and were addressed through the TBE Corrective Action Program. Investigations of the failures are described as follows:

TBE Crosschecks failed high for MRAD-40 Gross Beta at 42.1 pCi/Filter. The true value was 22.2 and the acceptable range was 13.5-33.5 pCi/Filter. All QC associated with the original sample was acceptable and no anomalies were found. This sample was used as the WG duplicate with a result of 42.5 pCi. Both were counted on the same detector. Upon comparison to historical sample data, the alpha activity of this ERA submitted sample was the highest assigned result, and the beta activity was the lowest. Therefore, the alpha-to-beta crosstalk was more significant than normal, causing the beta activity to report falsely high data. The counting room laboratory staff will adjust the alpha-to-beta crosstalk via correction calculation measures when high alpha are observed. Subsequent study MRAD-41 for Gross Beta filter returned acceptable results.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 51 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant RAD-137 Gross Alpha in water failed low at 35.2 pCi/L. The true value was 52.6 pCi/L and the acceptable range was 39.6 - 65.6 pCi/L. A QuiKResponse repeat study was analyzed and failed high at 40.3 pCi/L and the acceptable range was 21.5 - 38.5 pCi/L. Investigation showed higher than usual solids in the ERA study, out of the usual range of client samples received by the lab. Also, a different attenuation curve, Th-230, was used for the crosscheck than had been used historically. This curve was less representative of client samples.

The lab review of data also showed that a replicate run of the sample would have passed but the lab chose the wrong replicate to report. The lab has gone to a lower volume of sample and resumed using the Am-241 attenuation curve which more closely mirrors client samples and subsequent crosschecks are reporting acceptable.

Quarter 1-2024 gamma results for Co-60 (air filter) and Ce-141 (soil) both failed high. The reported result for the filter Co-60 was 168+/- 12.7 and the known value was 126+/-2.1; the reported results for the soil Ce-141 was 0.106 and the known value was 0.0714+/-0.0013 pCi/g. The root cause investigation showed successful results for the filter on another detector. All QC associated with this sample was acceptable. The soil was recounted on another detector and Ce-141 result of 0.085 was acceptable and generally the same for other geometries. All QC associated with this sample was acceptable. No effective corrective action can be taken at this time. Historically, the Filter Co-60 and soil Ce-141 results have been well within TBE QC acceptance ranges. TBE has successfully passed cross-check results and it appears that these two results are anomalous. If there is a recurrence, a root cause investigation will be done promptly.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 52 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 3/14/2024 E14036 Milk pCi/L I-131 96.7 90.8 63.6 118 Pass pCi/L Cs-134 182 198 139 257 Pass pCi/L Cs-137 181 171 120 222 Pass pCi/L Ce-141 88.1 85 59.5 111 Pass pCi/L Cr-51 281 230 161 299 Pass pCi/L Mn-54 187 183 128 238 Pass pCi/L Fe-59 93.6 86.5 60.6 112 Pass pCi/L Co-60 152 158 111 205 Pass pCi/L Zn-65 161 176 123 229 Pass 3/14/2024 E14037 Water pCi/L Beta Cs-137 238 231 162 300 Pass 3/14/2024 E14038 Charcoal pCi I-131 75.9 90.2 63.1 117 Pass 3/14/2024 E14038 Charcoal pCi I-131 79.0 90.2 63.1 117 Pass 3/14/2024 E14038 Charcoal pCi I-131 77.1 90.2 63.1 117 Pass 3/14/2024 E14038 Charcoal pCi I-131 77.3 90.2 63.1 117 Pass 4/8/2024 RAD-137 Water pCi/L I-131 27.1 25.1 21.7 28.5 Pass 4/8/2024 RAD-137 Water pCi/L I-131 25.1 25.1 21.7 28.5 Pass 4/8/2024 RAD-137 Water pCi/L I-131 27.5 25.1 21.7 28.5 Pass 4/8/2024 RAD-137 Water pCi/L I-131 29.7 25.1 21.7 28.5 Fail 1 4/8/2024 RAD-137 Water pCi/L Beta Cs-137 36.6 46.5 33.9 59.1 Pass 4/8/2024 RAD-137 Water pCi/L Cs-134 55.9 57.8 42.8 72.8 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 53 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 4/8/2024 RAD-137 Water pCi/L Cs-137 190 186 149 223 Pass pCi/L Co-60 98.8 98.8 79.7 118 Pass pCi/L Zn-65 228 240 188 292 Pass 4/8/2024 RAD-137 Water pCi/L Cs-134 60.7 57.8 42.8 72.8 Pass pCi/L Cs-137 185 186 149 223 Pass pCi/L Co-60 97.7 98.8 79.7 118 Pass pCi/L Zn-65 233 240 188 292 Pass 4/8/2024 RAD-137 Water pCi/L Cs-134 59.8 57.8 42.8 72.8 Pass pCi/L Cs-137 190 186 149 223 Pass pCi/L Co-60 97.2 98.8 79.7 118 Pass pCi/L Zn-65 240 240 188 292 Pass 4/8/2024 RAD-137 Water pCi/L Cs-134 58.6 57.8 42.8 72.8 Pass pCi/L Cs-137 185 186 149 223 Pass pCi/L Co-60 102 98.8 79.7 118 Pass pCi/L Zn-65 227 240 188 292 Pass 6/13/2024 E14101 Soil pCi/g Cs-134 0.406 0.408 0.286 0.530 Pass pCi/g Cs-137 0.402 0.451 0.316 0.586 Pass 6/13/2024 E14101 Soil pCi/g Cs-134 0.372 0.408 0.286 0.530 Pass pCi/g Cs-137 0.365 0.451 0.316 0.586 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 54 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 6/13/2024 E14039 Water pCi/L Beta Cs-137 265 262 183 341 Pass 6/13/2024 E14040 Water pCi/L Ce-141 45.4 37.5 26.3 48.8 Pass pCi/L Co-60 402 391 274 508 Pass pCi/L Cr-51 250 291 204 378 Pass pCi/L Cs-134 237 242 169 315 Pass pCi/L Cs-137 233 229 160 298 Pass pCi/L Fe-59 183 174 122 226 Pass pCi/L Mn-54 209 204 143 265 Pass pCi/L Zn-65 89.6 99.1 69.4 129 Pass 6/13/2024 E14040 Water pCi/L Ce-141 40 37.5 26.3 48.8 Pass pCi/L Co-60 397 391 274 508 Pass pCi/L Cr-51 286 291 204 378 Pass pCi/L Cs-134 238 242 169 315 Pass pCi/L Cs-137 237 229 160 298 Pass pCi/L Fe-59 183 174 122 226 Pass pCi/L Mn-54 212 204 143 265 Pass pCi/L Zn-65 95.4 99.1 69.4 129 Pass 6/13/2024 E14041 Filter pCi Ce-141 25.4 25.2 17.6 32.8 Pass pCi Co-60 258 262 183 341 Pass pCi Cr-51 211 195 137 254 Pass pCi Cs-134 137 162 113 211 Pass pCi Cs-137 159 153 107 199 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 55 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 6/13/2024 E14041 Filter pCi Fe-59 132 117 81.9 152 Pass pCi Mn-54 143 137 95.9 178 Pass pCi Zn-65 71.0 66.4 46.5 86.3 Pass 6/13/2024 E14042A Filter pCi Beta Cs-137 249 220 154 286 Pass 9/12/2024 E14043 Filter pCi Beta Cs-137 242 221 84.7 157 Pass 9/12/2024 E14102 Soil pCi/g Cs-134 0.318 0.336 0.235 0.437 Pass pCi/g Cs-137 0.287 0.295 0.207 0.384 Pass 9/12/2024 E14102 Soil pCi/g Cs-134 0.299 0.336 0.235 0.437 Pass pCi/g Cs-137 0.269 0.295 0.207 0.384 Pass 9/12/2024 E14102 Soil pCi/g Cs-134 0.305 0.336 0.235 0.437 Pass pCi/g Cs-137 0.277 0.295 0.207 0.384 Pass 9/12/2024 E14102 Soil pCi/g Cs-134 0.312 0.336 0.235 0.437 Pass pCi/g Cs-137 0.282 0.295 0.207 0.384 Pass 9/16/2024 MRAD-41 Filter pCi Cs-134 499 581 377 712 Pass pCi Cs-137 880 848 696 1110 Pass pCi Co-60 865 839 713 1070 Pass pCi Zn-65 269 239 196 365 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 56 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 10/4/2024 RAD-139 Water pCi/L Cs-134 79.6 80.2 63.0 97.4 Pass pCi/L Cs-137 49.7 46.3 23.3 69.3 Pass 10/4/2024 RAD-139 Water pCi/L Co-60 47.9 45.3 31.6 59.0 Pass pCi/L Zn-65 108 114 75.0 153 Pass 10/4/2024 RAD-139 Water pCi/L Cs-134 79.8 80.2 63.0 97.4 Pass pCi/L Cs-137 46.0 46.3 23.3 69.3 Pass pCi/L Co-60 49.4 45.3 31.6 59.0 Pass pCi/L Zn-65 106 114 75.0 153 Pass 10/4/2024 RAD-139 Water pCi/L Cs-134 79.4 80.2 63.0 97.4 Pass pCi/L Cs-137 46.3 46.3 23.3 69.3 Pass pCi/L Co-60 47.5 45.3 31.6 59.0 Pass pCi/L Zn-65 106 114 75.0 153 Pass 10/4/2024 RAD-139 Water pCi/L I-131 26.4 26.3 22.7 29.9 Pass 10/4/2024 RAD-139 Water pCi/L I-131 26.3 26.3 22.7 29.9 Pass 12/5/2024 E14044 Filter pCi Ce-141 75.7 74.8 52 97 Pass pCi Co-58 105 97.9 69 127 Pass pCi Cr-60 220 219 153 285 Pass pCi Cr-51 182 185 130 241 Pass pCi Cs-134 97.9 116 81 151 Pass pCi Cs-137 144 144 101 187 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 57 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 12/5/2024 E14044 Filter pCi Fe-59 130 107 75 139 Pass pCi Mn-54 113 104 73 135 Pass pCi Zn-65 164 155 109 202 Pass 12/5/2024 E14044 Filter pCi Ce-141 69.3 74.8 52 97 Pass pCi Co-58 93.7 97.9 69 127 Pass pCi Cr-60 196 219 153 285 Pass pCi Cr-51 166 185 130 241 Pass pCi Cs-134 91.3 116 81 151 Fail 1 pCi Cs-137 135 144 101 187 Pass pCi Fe-59 113 107 75 139 Pass pCi Mn-54 106 104 73 135 Pass pCi Zn-65 146 155 109 202 Pass 12/5/2024 E14044 Filter pCi Ce-141 66.6 74.8 52 97 Pass pCi Co-58 92.4 97.9 69 127 Pass pCi Cr-60 204 219 153 285 Pass pCi Cr-51 175 185 130 241 Pass pCi Cs-134 95.7 116 81 151 Pass pCi Cs-137 139 144 101 187 Pass pCi Fe-59 119 107 75 139 Pass pCi Mn-54 102 104 73 135 Pass pCi Zn-65 139 155 109 202 Pass 12/5/2024 E14045 Water pCi/L Beta Cs-137 257 240 168 312 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 58 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 12/5/2024 E14046 Charcoal pCi I-131 58.0 65.3 45.7 84.9 Pass pCi I-131 59.3 65.3 45.7 84.9 Pass pCi I-131 59.4 65.3 45.7 84.9 Pass 12/5/2024 E14047 Milk pCi/L Ce-141 74.7 71.6 50.1 93.1 Pass pCi/L Co-58 95.2 93.7 65.6 122 Pass pCi/L Co-60 211 210 147 273 Pass pCi/L Cr-51 164 177 124 230 Pass pCi/L Cs-134 114 111 77.7 144 Pass pCi/L Cs-137 150 138 96.6 179 Pass pCi/L Fe-59 112 102 71.4 133 Pass pCi/L I-131 50.1 51.0 35.7 66.3 Pass pCi/L Mn-54 106 99.5 69.7 129 Pass pCi/L Zn-65 141 149 104 194 Pass 12/5/2024 E14047 Milk pCi/L Ce-141 77.8 71.6 50.1 93.1 Pass pCi/L Co-58 96.9 93.7 65.6 122 Pass pCi/L Co-60 208 210 147 273 Pass pCi/L Cr-51 205 177 124 230 Pass pCi/L Cs-134 110 111 77.7 144 Pass pCi/L Cs-137 140 138 96.6 179 Pass pCi/L Fe-59 100 102 71.4 133 Pass pCi/L I-131 45.5 51.0 35.7 66.3 Pass pCi/L Mn-54 109 99.5 69.7 129 Pass pCi/L Zn-65 136 149 104 194 Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 59 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14: Cross Check Intercomparison Results Study Date Study ID Units Radionuclide Reported Value Assigned Value Acceptance Performance Evaluation Lower Limit Upper Limit 12/5/2024 E14047 Milk pCi/L Ce-141 71.9 71.6 50.1 93.1 Pass pCi/L Co-58 89.7 93.7 65.6 122 Pass pCi/L Co-60 232 210 147 273 Pass pCi/L Cr-51 180 177 124 230 Pass pCi/L Cs-134 113 111 77.7 144 Pass pCi/L Cs-137 149 138 96.6 179 Pass pCi/L Fe-59 112 102 71.4 133 Pass pCi/L I-131 63.3 51.0 35.7 66.3 Pass pCi/L Mn-54 105 99.5 69.7 129 Pass pCi/L Zn-65 148 149 104 194 Pass 1 See Discussion at the beginning of Attachment 3

Annual Radiological Environmental Operating Report YEAR: 2024 Page 60 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Water Q9-1 1/31/2024 Gross Beta pCi/L 1.45 0.769 1.97E +/- 1.27 Pass Water Q9-1 1/31/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 1/31/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 1/31/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 2/28/2024 Gross Beta pCi/L 1.28 0.770 2.5+/-1.25 Pass Water Q9-1 2/28/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 2/28/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 2/28/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 3/27/2024 Gross Beta pCi/L 1.39 0.722 2.92+/-1.26 Pass Water Q9-1 3/27/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 3/27/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 3/27/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 5/1/2024 Gross Beta pCi/L 1.42 0.711 2.00+/-1.3 Pass Water Q9-1 5/1/2024 LLI pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 61 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Water Q9-1 5/1/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 5/1/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 5/29/2024 Gross Beta pCi/L

<MDA 2.79+/-1.4 Pass Water Q9-1 5/29/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 5/29/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 5/29/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 6/26/2024 Gross Beta pCi/L 1.37 0.753 3.39+/-1.52 Pass Water Q9-1 6/26/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 6/26/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 6/26/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 8/1/2024 Gross Beta pCi/L 1.52 0.789

<MDA Pass Water Q9-1 8/1/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 8/1/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 8/1/2024 Tritium pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 62 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Water Q9-1 8/29/2024 Gross Beta pCi/L 1.93 0.781 3.66+/-1.43 Pass Water Q9-1 8/29/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 8/29/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 8/29/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 10/3/2024 Gross Beta pCi/L 1.60 0.762

<MDA Pass Water Q9-1 10/3/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 10/3/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 10/3/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 10/30/2024 Gross Beta pCi/L 1.97 0.788 2.68+/-1.62 Pass Water Q9-1 10/30/2024 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 10/30/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 10/30/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 12/4/2024 Gross Beta pCi/L 1.58 0.768

<MDA Pass Water Q9-1 12/4/2024 LLI pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 63 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Water Q9-1 12/4/2024 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 12/4/2024 Tritium pCi/L

<MDA

<MDA Pass Water Q9-1 1/2/2025 Gross Beta pCi/L

<MDA

<MDA Pass Water Q9-1 1/2/2025 LLI pCi/L

<MDA

<MDA Pass Water Q9-1 1/2/2025 Gamma pCi/L

<MDA

<MDA Pass Water Q9-1 1/2/2025 Tritium pCi/L

<MDA

<MDA Pass Milk G2-1 1/18/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 1/18/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 2/14/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 2/14/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 3/7/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 3/7/2024 LLI pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 64 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Milk G2-1 3/20/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 3/20/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 4/4/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 4/4/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 4/18/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 4/18/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 5/1/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 5/1/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 5/15/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 5/15/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 5/29/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 5/29/2024 LLI pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 65 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Milk G2-1 6/13/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 6/13/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 6/26/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 6/26/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 7/10/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 7/10/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 7/24/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 7/24/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 8/8/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 8/8/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 8/22/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 8/22/2024 LLI pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 66 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Milk G2-1 9/5/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 9/5/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 9/19/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 9/19/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 10/3/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 10/3/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 10/17/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 10/17/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 10/30/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 10/30/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 11/13/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 11/13/2024 LLI pCi/L

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 67 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Milk G2-1 11/26/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 11/26/2024 LLI pCi/L

<MDA

<MDA Pass Milk G2-1 12/11/2024 Gamma pCi/L

<MDA

<MDA Pass Milk G2-1 12/11/2024 LLI pCi/L

<MDA

<MDA Pass Filter Composite E1-2 3/27/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite E1-2 6/26/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite E1-2 10/3/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite E1-2 1/2/2025 Gamma pCi/m3

<MDA

<MDA Pass Vegetation H1-2 6/19/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation H1-2 7/17/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation H1-2 8/14/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation H1-2 9/11/2024 Gamma pCi/Kg

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 68 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Vegetation B10-2 8/14/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation B10-2 8/14/2024 Strontium 90 pCi/Kg

<MDA

<MDA Pass Fish INDP 10/16/2024 Gamma pCi/Kg

<MDA

<MDA Pass Fish INDP 10/16/2024 Strontium 90 pCi/Kg

<MDA

<MDA Pass Sediment J2-1 10/29/24 Gamma pCi/Kg

<MDA

<MDA Pass Water WA1 6/28/2024 Gamma pCi/L

<MDA

<MDA Pass Water WA2 6/28/2024 Gamma pCi/L

<MDA

<MDA Pass Oysters IA3 6/19/2024 Gamma pCi/Kg

<MDA

<MDA Pass Oysters IA6 6/19/2024 Gamma pCi/Kg

<MDA

<MDA Pass Bottom Sediment WBS4 6/19/2024 Gamma pCi/Kg

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 69 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Bottom Sediment WBS2 6/19/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation IB10 7/22/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation IB11 7/22/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation IB12 7/22/2024 Gamma pCi/Kg

<MDA

<MDA Pass Vegetation East 7/23/2024 Gamma pCi/Kg

<MDA

<MDA Pass Milk Farm A 09/03/2024 Gamma Gamma pCi/L

<MDA Pass Milk Farm A 09/03/2024 Gamma LLI pCi/L

<MDA Pass Milk Farm B 09/03/2024 Gamma Gamma pCi/L

<MDA Pass Milk Farm B 09/03/2024 Gamma LLI pCi/L

<MDA Pass Milk

55 09/09/2024 Gamma Gamma pCi/L

<MDA Pass Milk

55 09/09/2024 Gamma LLI pCi/L

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 70 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results Sample Type Location Sample Date Analysis Result Units CGS Results w 2 TBE Split Results w 2 Pass/Fail (Split)

Fish (Spanish Mackerel)

IA1 8/14/2024 Gamma pCi/kg

<MDA

<MDA Pass Filter Composite CC-A1 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-A2 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-A3 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-A4 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-A5 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-SFA1 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-SFA2 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-SFA3 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass Filter Composite CC-SFA4 9/30/2024 Gamma pCi/m3

<MDA

<MDA Pass

Annual Radiological Environmental Operating Report YEAR: 2024 Page 71 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results (Air Particulate Beta )

Media Location Sample Date Beta pCi/M3 (CGS)

E1-2

+/-2 (TBE)

E1-2Q

+/-2 Filter E1-2 / E1-2Q 1/04/2024 Beta pCi/M3 2.46E-02 2.37E-03 8.99E-03 4.65E-03 Filter E1-2 / E1-2Q 1/11/2024 Beta pCi/M3 1.73E-02 2.05E-03 1.40E-02 3.83E-03 Filter E1-2 / E1-2Q 1/18/2024 Beta pCi/M3 3.39E-02 2.68E-03 2.02E-02 4.34E-03 Filter E1-2 / E1-2Q 1/25/2024 Beta pCi/M3 2.64E-02 2.37E-03 1.61E-02 4.20E-03 Filter E1-2 / E1-2Q 1/31/2024 Beta pCi/M3 1.25E-02 2.06E-03 9.29E-03 4.01E-03 Filter E1-2 / E1-2Q 2/08/2024 Beta pCi/M3 1.83E-02 1.99E-03 1.23E-02 3.41E-03 Filter E1-2 / E1-2Q 2/14/2024 Beta pCi/M3 2.28E-02 2.63E-03 1.23E-02 4.54E-03 Filter E1-2 / E1-2Q 2/22/2024 Beta pCi/M3 2.14E-02 2.04E-03 1.11E-02 3.42E-03 Filter E1-2 / E1-2Q 2/28/2024 Beta pCi/M3 2.37E-02 2.56E-03 1.91E-02 4.75E-03 Filter E1-2 / E1-2Q 3/07/2024 Beta pCi/M3 1.32E-02 1.75E-03 7.60E-03 3.15E-03 Filter E1-2 / E1-2Q 3/14/2024 Beta pCi/M3 1.86E-02 2.21E-03 1.42E-02 4.18E-03 Filter E1-2 / E1-2Q 3/20/2024 Beta pCi/M3 2.06E-02 2.49E-03 1.57E-02 4.26E-03 Filter E1-2 / E1-2Q 3/27/2024 Beta pCi/M3 1.31E-02 1.99E-03 1.16E-02 3.61E-03 Filter E1-2 / E1-2Q 4/04/2024 Beta pCi/M3 1.63E-02 1.89E-03 9.42E-03 3.57E-03 Filter E1-2 / E1-2Q 4/11/2024 Beta pCi/M3 1.61E-02 2.01E-03 8.08E-03 3.54E-03 Filter E1-2 / E1-2Q 4/18/2024 Beta pCi/M3 1.99E-02 2.21E-03 1.01E-02 3.83E-03 Filter E1-2 / E1-2Q 4/25/2024 Beta pCi/M3 1.54E-02 2.04E-03 1.09E-02 3.67E-03 Filter E1-2 / E1-2Q 5/01/2024 Beta pCi/M3 2.45E-02 2.63E-03 1.75E-02 4.61E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 72 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results (Air Particulate Beta )

Media Location Sample Date Beta pCi/M3 (CGS)

E1-2

+/-2 (TBE)

E1-2Q

+/-2 Filter E1-2 / E1-2Q 5/9/2024 Beta pCi/M3 1.41E-02 1.70E-03 1.12E-02 3.37E-03 Filter E1-2 / E1-2Q 5/15/2024 Beta pCi/M3 8.08E-03 2.05E-03 8.46E-03 3.71E-03 Filter E1-2 / E1-2Q 5/23/2024 Beta pCi/M3 1.40E-02 1.84E-03 1.16E-02 3.49E-03 Filter E1-2 / E1-2Q 5/29/2024 Beta pCi/M3 1.94E-02 2.38E-03 1.13E-02 4.37E-03 Filter E1-2 / E1-2Q 6/06/2024 Beta pCi/M3 1.87E-02 1.98E-03 1.80E-02 3.94E-03 Filter E1-2 / E1-2Q 6/13/2024 Beta pCi/M3 1.08E-02 1.82E-03 1.02E-02 3.70E-03 Filter E1-2 / E1-2Q 6/20/2024 Beta pCi/M3 2.35E-02 2.41E-03 2.06E-02 4.41E-03 Filter E1-2 / E1-2Q 6/26/2024 Beta pCi/M3 2.63E-02 2.67E-03 1.65E-02 4.74E-03 Filter E1-2 / E1-2Q 7/03/2024 Beta pCi/M3 1.48E-02 1.93E-03 9.09E-03 3.78E-03 Filter E1-2 / E1-2Q 7/10/2024 Beta pCi/M3 2.61E-02 2.43E-03 1.64E-02 4.38E-03 Filter E1-2 / E1-2Q 7/18/2024 Beta pCi/M3 2.29E-02 2.15E-03 1.56E-02 3.79E-03 Filter E1-2 / E1-2Q 7/24/2024 Beta pCi/M3 2.28E-02 2.55E-03 1.21E-02 4.55E-03 Filter E1-2 / E1-2Q 8/01/2024 Beta pCi/M3 2.36E-02 2.15E-03 2.03E-02 4.15E-03 Filter E1-2 / E1-2Q 8/08/2024 Beta pCi/M3 2.62E-02 2.44E-03 1.50E-02 4.32E-03 Filter E1-2 / E1-2Q 8/15/2024 Beta pCi/M3 1.77E-02 2.14E-03 2.14E-02 4.43E-03 Filter E1-2 / E1-2Q 8/22/2024 Beta pCi/M3 1.88E-02 2.21E-03 1.43E-02 4.01E-03 Filter E1-2 / E1-2Q 8/29/2024 Beta pCi/M3 4.12E-02 2.87E-03 2.95E-02 4.85E-03 Filter E1-2 / E1-2Q 9/05/2024 Beta pCi/M3 2.04E-02 2.30E-03 1.30E-02 4.17E-03 Filter E1-2 / E1-2Q 9/12/2024 Beta pCi/M3 2.38E-02 2.37E-03 2.02E-02 4.26E-03

Annual Radiological Environmental Operating Report YEAR: 2024 Page 73 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 14 Continued: Interlaboratory Split Sample Results (Air Particulate Beta )

Media Location Sample Date Beta pCi/M3 (CGS)

E1-2

+/-2 (TBE)

E1-2Q

+/-2 Filter E1-2 / E1-2Q 9/19/2024 Beta pCi/M3 3.26E-02 2.63E-03 2.60E-02 4.61E-03 Filter E1-2 / E1-2Q 9/26/2024 Beta pCi/M3 2.24E-02 2.24E-03 2.01E-02 4.39E-03 Filter E1-2 / E1-2Q 10/03/2024 Beta pCi/M3 1.13E-02 1.89E-03 8.26E-03 3.65E-03 Filter E1-2 / E1-2Q 10/10/2024 Beta pCi/M3 2.69E-02 2.40E-03 2.19E-02 4.66E-03 Filter E1-2 / E1-2Q 10/17/2024 Beta pCi/M3 2.76E-02 2.41E-03 1.72E-02 4.17E-03 Filter E1-2 / E1-2Q 10/24/2024 Beta pCi/M3 3.73E-02 2.72E-03 3.39E-02 5.17E-03 Filter E1-2 / E1-2Q 10/30/2024 Beta pCi/M3 1.96E-02 2.45E-03 1.57E-02 4.58E-03 Filter E1-2 / E1-2Q 11/07/2024 Beta pCi/M3 2.42E-02 2.15E-03 2.10E-02 3.89E-03 Filter E1-2 / E1-2Q 11/13/2024 Beta pCi/M3 2.03E-02 2.46E-03 1.69E-02 4.76E-03 Filter E1-2 / E1-2Q 11/20/2024 Beta pCi/M3 2.63E-02 2.45E-03 2.30E-02 4.50E-03 Filter E1-2 / E1-2Q 11/26/2024 Beta pCi/M3 2.04E-02 2.36E-03 1.41E-02 4.52E-03 Filter E1-2 / E1-2Q 12/04/2024 Beta pCi/M3 2.38E-02 2.15E-03 2.08E-02 4.08E-03 Filter E1-2 / E1-2Q 12/11/2024 Beta pCi/M3 2.87E-02 2.53E-03 2.21E-02 4.54E-03 Filter E1-2 / E1-2Q 12/19/2024 Beta pCi/M3 1.89E-02 1.93E-03 1.45E-02 3.56E-03 Filter E1-2 / E1-2Q 12/26/2024 Beta pCi/M3 2.01E-02 2.20E-03 1.65E-02 4.20E-03 Filter E1-2 / E1-2Q 1/2/2025 Beta pCi/M3 1.69E-02 2.05E-03 1.08E-02 3.80E-03 See discussion at the beginning of Attachment 3 describes the interlaboratory split program.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 74 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

, Environmental Direct Radiation Dosimetry Results Monitoring Location Quarterly

Baseline, BQ (mrem)

BQ +

MDDQ (mrem)

Normalized Quarterly Monitoring Data, MQ Quarterly Facility Dose, FQ=MQ-BQ Annual

Baseline, BA (mrem)

BA +

MDDA (mrem)

Annual Monitoring Data, MA (mrem)

Annual Facility Dose, FA=MA-BA (mrem, or ND if FA MDDA)

(mrem)

(mrem, or ND if FQ MDDQ) 1 2

3 4

1 2

3 4

DR01 13.9 23.99 11.6 13.8 11 12.5 ND ND ND ND 52.8 79.8 48.9 ND DR02 11.5 21.59 9.13 10.4 9.82 8.92 ND ND ND ND 43.6 70.6 38.3 ND DR03 10.9 20.99 8.31 11.4 13.7 7.68 ND ND ND ND 43.5 70.5 41.1 ND DR04 13.2 23.29 No data 10.8 12.4 9.09 No data ND ND ND 52.8 79.8 32.3 ND DR05 13 23.09 10.2 12.5 12.8 9.91 ND ND ND ND 51.8 78.8 45.4 ND DR06 11 21.09 8.85 10.6 12.3 8.28 ND ND ND ND 44.2 71.2 40 ND DR07 11.2 21.29 10 12.1 10.8 9.57 ND ND ND ND 44.7 71.7 42.5 ND DR08 15.8 25.89 13.1 14.6 14.5 12.6 ND ND ND ND 63.3 90.3 54.8 ND DR09 11.7 21.79 8.91 11.4 12.1 7.85 ND ND ND ND 46.6 73.6 40.3 ND DR10 11.3 21.39 8.85 11.2 11.9 9.7 ND ND ND ND 42.8 69.8 41.6 ND DR11 11.5 21.59 8.48 11.9 12.4 8.92 ND ND ND ND 43.6 70.6 41.7 ND DR12 11.4 21.49 9.29 9.78 10.1 8.45 ND ND ND ND 45.5 72.5 37.6 ND DR13 12.8 22.89 11.5 12 11.9 9.78 ND ND ND ND 48.6 75.6 45.2 ND DR14 14.3 24.39 11.7 14.3 14 12.8 ND ND ND ND 57 84.0 52.8 ND DR15 12.5 22.59 9.72 12.2 12.2 10.9 ND ND ND ND 50 77.0 45 ND DR16 11.3 21.39 8.58 11.4 11.4 8.58 ND ND ND ND 45 72.0 40 ND DR17 13.2 23.29 9.67 14.8 14.7 13.6 ND ND ND ND 47.5 74.5 52.8 ND DR18 10.4 20.49 8.91 10.1 9.92 9.18 ND ND ND ND 41.6 68.6 38.1 ND DR19 11.7 21.79 10.5 11.6 11.5 11 ND ND ND ND 46.7 73.7 44.6 ND DR20 14 24.09 11.3 13.3 14.1 13 ND ND ND ND 56.1 83.1 51.7 ND DR21 13 23.09 11 13.5 12.7 9.78 ND ND ND ND 52.1 79.1 47 ND DR22 11.9 21.99 9.07 13.1 11.8 11.1 ND ND ND ND 42.9 69.9 45.1 ND DR23 16.9 26.99 13.2 18.1 16.2 17.2 ND ND ND ND 67.8 94.8 64.7 ND DR30 13.4 23.49 11.9 11.4 11.6 9.74 ND ND ND ND 53.8 80.8 44.6 ND

Annual Radiological Environmental Operating Report YEAR: 2024 Page 75 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Monitoring Location Quarterly

Baseline, BQ (mrem)

BQ +

MDDQ (mrem)

Normalized Quarterly Monitoring Data, MQ Quarterly Facility Dose, FQ=MQ-BQ Annual

Baseline, BA (mrem)

BA +

MDDA (mrem)

Annual Monitoring Data, MA (mrem)

Annual Facility Dose, FA=MA-BA (mrem, or ND if FA MDDA)

(mrem)

(mrem, or ND if FQ MDDQ) 1 2

3 4

1 2

3 4

SFDR01 18.8 28.89 16.9 17.6 21.3 16.1 ND ND ND ND 75.1 102.1 71.9 ND SFDR02 20.3 30.39 16 17.5 19.9 17 ND ND ND ND 81.1 108.1 70.4 ND SFDR03 39.3 49.39 28.1 27.1 29.6 30 ND ND ND ND 157 184.0 115 ND SFDR04 34.5 44.59 49.3 52.8 61.4 61.7 14.9 18.3 26.9 27.3 138 165.0 225 87.4 SFDR05 20.6 30.69 39.8 44.6 49.6 50.1 19.3 24.1 29.1 29.6 82.2 109.2 184 102 SFDR06 17.5 27.59 29.6 33.3 50.4 60.6 12.1 15.8 32.8 43.1 70.1 97.1 174 104 SFDR07 13.2 23.29 10.7 13.4 13.3 13.9 ND ND ND ND 52.8 79.8 51.3 ND SFDR08 29.8 39.89 21.7 24.6 25.7 25 ND ND ND ND 119 146.0 97 ND SFDR09 15.8 25.89 77.5 86.8 142 195 61.7 71 127 179 63.2 90.2 501 438 SFDR10 32.7 42.79 20.6 24 25.4 23.4 ND ND ND ND 131 158.0 93.4 ND SFDR11 31 41.09 21.9 23.1 23.1 23 ND ND ND ND 124 151.0 91.1 ND SFDR12 45.5 55.59 39.3 38.3 40.7 38.4 ND ND ND ND 182 209.0 157 ND SFDR13 23.9 33.99 132 147 145 163 108 123 121 139 95.7 122.7 587 491 SFDR14 18 28.09 98.1 97.1 222 350 80 79.1 204 332 72.1 99.1 767 695 SFDR15 22.7 32.79 45.9 55.7 55.5 56.1 23.2 33 32.8 33.4 90.7 117.7 213 122 SFDR16 37.9 47.99 99 97.5 110 129 61.1 59.6 72.3 91.2 152 179.0 436 284 SFDR17 42.2 52.29 30.6 37.4 41.9 37.5 ND ND ND ND 169 196.0 147 ND SFDR18 48.5 58.59 37.6 37.8 39 40.7 ND ND ND ND 194 221.0 155 ND MDDQ = Quarterly Minimum Differential Dose = 10.09 mrem MDDA = Annual Minimum Differential Dose = 27.02 mrem ND = Not Detected, where MQ (BQ+MDDQ) or MA (BA+MDDA)

Annual Radiological Environmental Operating Report YEAR: 2024 Page 76 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

DR04 Lost Dosimeter in Quarter 1 2024 Figure 7: REMP Quarterly (91 day) Exposure of Environmental Dosimeters

Annual Radiological Environmental Operating Report YEAR: 2024 Page 77 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 8: REMP Mean Dosimeter Gamma Dose 10 Year History

Annual Radiological Environmental Operating Report YEAR: 2024 Page 78 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 9: ISFSI Mean Dosimeter Gamma Dose 10 Year History

Annual Radiological Environmental Operating Report YEAR: 2024 Page 79 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant

, Radiological Groundwater Protection Program 1.0 Summary and Conclusions The NEI Industry Groundwater Protection Initiative was established to determine the potential impact nuclear power plants may have on the surrounding environment due to unplanned releases of radioactive liquids. Under the Groundwater Protection Initiative, groundwater monitoring is accomplished through routine sampling of the water table around the plant [23]. Analysis is performed for gamma, tritium, alpha, beta, and various other radiological isotopes. Tables 15 through 19 contain the analytical results for samples taken from the various groundwater monitoring wells, subsurface drains, and rainwater. In 2019 MH24 was renamed to MH66/SSD3.

Calvert Cliffs Generating Station has a total of 16 on-site piezometer tube wells (four Background designated wells, eight Source designated wells, and four Perimeter designated wells), one sub-surface drain, and two circulating water tunnel access manholes (monitored as a Source designated sample locations) that are sampled as part of their RGPP (EN-CA-408-4160). Figure 10 shows the manhole and monitoring well sample locations.

Groundwater samples were collected from 16 on-site piezometer tubes and three subsurface manholes in 2024. These locations are listed in Table 20 and on Figure 10, Site Map Groundwater Monitoring Wells. Figure 11, Site Map Precipitation Recapture Locations shows precipitation collection sites.

Based on recapture tritium results, groundwater at the station could potentially be affected by precipitation recapture.

A piezometer tube is a shallow monitoring well which allows access to groundwater at a depth of approximately 40 feet beneath the site. Of the piezometer tubes sampled, only MH28 and MH30 showed any plant related results greater than MDAs. This activity was previously identified and evaluated in December of 2005. The activity consists of tritium originating from normal radiological waste discharges and was previously reported in the Annual Radioactive Release Reports. The tritium contamination is contained on site. No drinking water has been affected; the groundwater at this location does not impact any drinking water pathway.

The 2024 RGPP sample locations effectively monitored Systems, Structures, and Components of the Station. Therefore, RGPP sample locations identified in Attachment 1 of EN-CA-408-4160 should continue to be sampled in accordance with Attachment 2 of EN-CA-408-4160.

Table 15: Alpha Isotopic and Pu-241 in Groundwater (pCi/L)

Location Date Fe-55 Ni-63 Cm-242 Cm-243 /

Cm-244 Pu-238 Pu-239 /

Pu-240 U-233 /

U-234 U-238 PZ-11 Oct

<58.08

<3.98

<0.1256

<0.1264

<0.02891

<0.1319

Annual Radiological Environmental Operating Report YEAR: 2024 Page 80 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 16: Gross Alpha and Strontium Monitoring Results (pCi/L)

Location Date Gross Alpha Dissolved Gross Alpha Suspended Sr89 Sr90 Units MH-66 10/15/2024

<1.68

<0.856

<9.31

<0.96 pCi/L MH-28 10/8/2024

<1.04

<0.856

<9.23

<0.983 pCi/L PZ11 5/7/2024 ND ND

<9.9

<0.299 pCi/L PZ11 10/29/2024

<1.43

<0.689 ND ND pCi/L PZ12 5/7/2024

<1.23

<1.05

<6.06

<0.946 pCi/L PZ13 5/7/2024

<1.22

<1.04

<6.97

<0.962 pCi/L PZ15 5/7/2024

<1.31

<1.03

<4.12

<0.873 pCi/L PZ24 5/7/2024

<1.22

<1.29

<5.06

<0.856 pCi/L PZ25 7/29/2025

<1.77

<0.88

<2.37

<0.832 pCi/L PZ29 5/7/2024 1.22 2.27

<4.69

<0.951 pCi/L PZ30 5/7/2024 4.13

<1.08

<4.15

<0.799 pCi/L ND No Data, sample obtained as required.

Table 17: Annual Well Monitoring Gamma Emitters (pCi/L)

Location 5/6/24 5/7/24 5/28/24 7/29/24 10/8/24 10/15/24 10/29/24 MH-66 ND ND ND ND ND

<MDA ND MH-28 ND ND ND ND

<MDA**

ND ND PZ11 ND ND ND ND ND ND

<MDA**

PZ12 ND

<MDA ND ND ND ND ND PZ13 ND

<MDA ND ND ND ND ND PZ15 ND

<MDA ND ND ND ND ND PZ19

<MDA ND ND ND ND ND ND PZ20

<MDA ND ND ND ND ND ND PZ21

<MDA ND ND ND ND ND ND PZ22

<MDA ND ND ND ND ND ND PZ23 ND

<MDA ND ND ND ND ND PZ24 ND

<MDA ND ND ND ND ND PZ25 ND ND

<MDA

<MDA ND ND ND PZ26

<MDA ND ND ND ND ND ND PZ27

<MDA ND ND ND ND ND ND PZ28 ND

<MDA ND ND ND ND ND PZ29 ND

<MDA ND ND ND ND ND PZ30 ND

<MDA ND ND ND ND ND ND No Data, Sample obtained as required.

<MDA Non-Natural Gamma Emitters below MDA

- Short lived isotopes Ba-140 and I-131 were not detected above MDA. MDAs are elevated due to samples held in the laboratory and analyzed on site.

Annual Radiological Environmental Operating Report YEAR: 2024 Page 81 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 18: Quarterly Monitoring Tritium (pCi/L)

Location Qtr1 Qtr2 Qtr3 Qtr4 MH-66

<200

<200 MH-28 848 330

<1000 1640 MH-30 994 656

<1000 305 PZ11

<200

<200 PZ12

<200

<200 PZ13

<200

<200 PZ15

<200

<200 PZ24

<200

<200 PZ25

<200

<200 PZ29

<200

<200 PZ30

<200

<200 Table 18 Continued: Annual Well Monitoring Tritium (pCi/L)

Location Qtr2 Location Qtr2 PZ19

<200 PZ23

<200 PZ20

<200 PZ26

<200 PZ21

<200 PZ27

<200 PZ22

<200 PZ28

<200 Table 19: Quarterly Precipitation Monitoring Tritium (pCi/L)

Location 1/23/2024 4/1/2024 7/1/2024 10/1/2024 RW 1 714

<200 213

<200 RW 2 1440 224

<200

<200 RW 3 1400

<200

<200 RW 4 267

<200 197

<200 RW 5

<200

<200 RW 6

<200

<200 RW 7

<200

<200 225

<200 RW 8

<200

Annual Radiological Environmental Operating Report YEAR: 2024 Page 82 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Table 20: Locations of Radiological Groundwater Environmental Sampling Stations RGPP Station Description PZ11 45' - North side of Unit 1 near roll-up door PZ12 NW corner of Unit 1 PZ13 Unit 1 RWT PZ15 Unit 2 RWT PZ18 45' - South side near stairwell to waterfront (idle)

PZ19 10' - Southside near traveling screen trough PZ20 10' -Northside of MMD Shop PZ21 10' - In grass West of STP PZ22 10 - In grass West of STP PZ23 45 - S of SSB doors PZ24 45' - East of SSB near Unit 2 roll-up door PZ25 45' - South side near stairwell to waterfront PZ26 45' -SW of Spare Transformer PZ27 45' -SW of Spare Transformer PZ28 45 - SW corner of NRC Bldg PZ29 45' - East of Nitrogen Tank in road PZ30 45' -NE Corner of Turbine Bldg RW1 Met Tower RW2 Lower Lay Down Area RW3 Visitors Center Overlook RW4 Waterfront RW5 Open Grass Area outside NSF PA exit RW6 U2 Turbine Building roll up door RW7 Open area north of Outfall 004 RW8 Open area on north wing wall MH28 12'- Unit1 next to Feed Water Heater MH30 12'- Unit 2 next to elevator MH66/SSD3 45'- East of SSB and South of Turbine Bldg (formerly named MH-24)

SW003 Waterfront south of Sewage Treatment Plant SW004 Waterfront Barge Dock Rd

Annual Radiological Environmental Operating Report YEAR: 2024 Page 83 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 10: Site Map Groundwater Monitoring Wells

Annual Radiological Environmental Operating Report YEAR: 2024 Page 84 of 84 Company: Constellation Plant: Calvert Cliffs Nuclear Power Plant Figure 11: Site Map Precipitation Recapture Locations

ML25135A003

Contents

Text

SUMMARY

Conclusions:

3.0 INTRODUCTION

SUMMARY

Conclusions:

3.0 INTRODUCTION

Navigation menu

ML25135A003

Text

SUMMARY

Conclusions:

3.0 INTRODUCTION

SUMMARY

Conclusions:

3.0 INTRODUCTION

Navigation menu

Search