ML22115A114

Annual Radiological Environmental Operating Report

ML22115A114
Person / Time
Site:	Millstone
Issue date:	04/25/2022
From:	Armstrong L Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
22-090
Download: ML22115A114 (92)

Text

Dominion Energy Nu clea r Co nn ecticut, In c.

Mill stone Power Station ~ Dominion

' 314 Rope Ferry Road, W aterford, CT 06385 Dominion Energy.com

~ Energy APR 2 5 2022 U.S. Nuclear Regulatory Commission Serial No.22-090 Attention: Document Control Desk MPS Lie/LO RO Washington, DC 20555-0001 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNITS 1, 2, AND 3 2021 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT This letter transmits the Annual Radiological Environmental Operating Report for the Millstone Power Station , for the period January 1, 2021, through December 31, 2021.

This satisfies the provisions of Section 5.7.2 of Millstone Power Station Unit 1 Permanently Defueled Technical Specifications (POTS), and Sections 6.9.1 .6a and 6.9.1.3 of the Millstone Power Station Units 2 and 3 Technical Specifications, respectively.

Should you have any questions, please contact Mr. Dean E. Rowe at (860) 444-5292.

Sincerely, c1/4<<rCL1/4 L. J. Armstrong

• Director, Nuclear Station Safety and Licensing Attachments: 1 Commitments made in this letter:

1. None.

Serial No.22-090 2021 Annual Radiological Environmental Operating Report Page 2 of 4 cc: U. S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 P.Longmire NRG Project Manager Millstone Unit 1 U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 5-A 10 11555 Rockville Pike Rockville, MD 20852-2738 L. A. Kauffman NRG Inspector U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 S. L. Wilson NRG Inspector U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman NRG Project Manager Millstone Units 2 and 3 U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C2 11555 Rockville Pike Rockville, MD 20852-2738 NRG Senior Resident Inspector Millstone Power Station

Serial No.22-090 2021 Annual Radiological Environmental Operating Report Page 3 of 4 (2copies)

Director Bureau of Air Management Monitoring & Radiation Division Department of Energy and Environmental Protection 79 Elm Street Hartford, CT 06106-5127 A. Honnellio Regional Radiation Representative (EPA Region 1, Boston)

U. S. Environmental Protection Agency (Region 1) 5 Post Office Square Suite 100 Boston, MA 02109 G. Allen Jr.

Department of Health and Human Services U. S. Food and Drug Administration 140 Shrewsbury Street, Suite 1 Boylston, MA 01501 M. Bachman Executive Director Connecticut Siting Council 10 Franklin Square New Britain, CT 06051 J.P. Kelley Waterford-East Lyme Shellfish Commission Waterford Town Hall Waterford, CT 06385 J. Folkwein American Nuclear Insurers 95 Glastonbury Blvd.

Glastonbury, CT 06033 D. Carey Connecticut Department of Agriculture Aquaculture Division P. 0. Box 97 Millford, CT 06460

Serial No.22-090 2021 Annual Radiological Environmental Operating Report Page 4 of 4 R. Brule First Selectman Town of Waterford Waterford Town Hall Waterford, CT 06385 K. A. Seery First Selectman Town of East Lyme PO Box 519 Niantic, CT 06357 University Of Connecticut Library Serials Department Storrs, CT 06268 Mrs. John Mingo 69 Spithead Road Waterford, CT 06385

Serial No.22-090 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 ATTACHMENT 1 2021 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MILLSTONE POWER STATION UNITS 1, 2, AND 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DENC)

Millstone Power Station 2021 Radiological Environmental Operating Report January 1, 2021- December 31, 2021 Dominion Energy Nuclear Connecticut, Inc.

Unit License Docket 1 DPR-21 50-245 2 DPR-65 50-336 3 NPF-49 50-423

~ Dominion p Energy

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MILLSTONE POWER STATION RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM 2021 Millstone Power Station Unit 1, DOCKET NO. 50-245 Millstone Power Station Unit 2, DOCKET NO. 50-336 Millstone Power Station Unit 3, DOCKET NO. 50-423 Dominion Energy Nuclear Connecticut, Inc.

Waterford, Connecticut

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

~ TABLE OF CONTENTS ,...,

EXECUTIVE

SUMMARY

....................................................................................................................i

1. INTRODUCTION ................................................................................................... 1-1 1.1. Overview ..................................................................................................... 1-1

1. 2. Radiation and Radioactivity ........................................................................ 1-1 1.3. Sources of Radiation ................................................................................... 1-2 1.4. Nuclear Reactor Operations ........................................................................ 1-3 1.5. Radioactive Effluent Control ....................................................................... 1-8 1.6. Radiological Impact on Humans ................................................................. 1-10

2. PROGRAM DESCRIPTION .................................................................................. 2-1 2.1 Sampling Schedule and Locations .................................................................. 2-1 2.2 Samples Collected During Report Period ........................................................ 2-7 2.3 Required Samples Not Collected During the Report Period ............................ 2-7

3. RADIOCHEMICAL RESULTS ............................................................................... 3-1 3.1 Summary Tables ............................................................................................. 3-1 3.2 Data Tables .................................................................................................... 3-7

4. DISCUSSION OF RESULTS ................................................................................ 4-1 4.1 Gamma Exposure Rate (Table 1) ............................................................... 4-1 4.2 Air Particulate Gross Beta Radioactivity (Table 2) ..................................... 4-4 4.3 Air Iodine (Table 3) .................................................................................... 4-5 4.4 Air Particulate Gamma (Table 4) ................................................................ 4-5 4.5 Soil (Table 5) ............................................................................................. 4-5 4.6 Cow Milk (Table 6) ..................................................................................... 4-6 4.7 Well Water (Table 7) .................................................................................. 4-6 4.8 Fruits and Vegetables (Table 8) ................................................................ 4-6 4.9 Broad Leaf Vegetation (Table 9) ................................................................ 4-6 4.1 O Seawater (Table 10) .................................................................................. 4-6 4.11 Bottom Sediment (Table 11) ...................................................................... 4-8 4.12 Aquatic Flora (Table 12) ............................................................................. 4-8 4.13 Fish (Table 13) ........................................................................................... 4-8 4.14 Oysters (Table 14) ..................................................................................... 4-8 4.15 Clams (Table 15) ....................................................................................... 4-8 4.16 Lobsters (Table 16) .................................................................................... 4-8

5. REFERENCES ...................................................................................................... 5-1 APPENDIX A - LAND USE CENSUS FOR 2021 ...................................................... A-1 APPENDIX 8 -

SUMMARY

OF INTERLABORATORY COMPARISONS ................. 8-1 APPENDIX C - ERRATUM ........................................................................................ C-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 EXECUTIVE

SUMMARY

INTRODUCTION This report summarizes the results of the Radiological Environmental Monitoring Program (REMP) conducted in the vicinity of the Millstone Power Station (MPS) during the period from January 1, 2021 to December 31, 2021. This document has been prepared in accordance with the requirements of the separate MPS Unit 1 (MPS1) Permanently Defueled Technical Specifications and the Technical Specifications for Millstone Units 2 and 3 (MPS2 and MPS3).

The REMP has been established to monitor the radiation and radioactivity released to the environment as a result of MPS's operation. This program, initiated in April 1967, includes the collection, analysis, and evaluation of radiological data in order to assess the impact of MPS on the environment and on the general public.

SAMPLING AND ANALYSIS The environmental sampling media collected in the vicinity of MPS and at distant locations included aquatic, atmospheric, and terrestrial samples. These samples were air particulate filters, charcoal cartridges, soil, well water, broadleaf vegetation, fruits and vegetables, seawater, bottom sediment, aquatic flora, fish, oysters, clams, and lobsters.

During 2021, there were 529 samples collected from the atmospheric, aquatic, and terrestrial environments. In addition, 170 exposure measurements were obtained using environmental thermo luminescent dosimeters (TLDs). A discussion of all discrepancies from the sample collection requirements in the MPS Radiological Effluent Monitoring and Offsite Dose Calculation Manual (REMODCM) is given in Section 2.3 of this report. Teledyne Brown Engineering, Inc. of Knoxville, Tennessee performed the sample analyses and Environmental Dosimetry Company of Sterling, Massachusetts, performed the TLD analyses.

LAND USE CENSUS The annual land use census in the vicinity of MPS was conducted as required by the MPS REMODCM. To determine the dairy exposure pathway, a list of cow milk and goat milk locations is established. The list of cow milk locations is identified by a review of the annual registration information obtained from the State of Connecticut Department of Agriculture. The list of goat milk locations is identified by the information obtained from the American Dairy Goat Association list and by inspections performed in the field. Although broadleaf sampling was performed and may be used in lieu of a garden census, gardens were included in the 2021 census. Only vegetable gardens having an area of more than 500 square feet were identified. Due to the difficulty of measuring individual gardens, the nearest garden within each directional sector identified by a drive-by survey is listed. However, for dose calculation, garden distances are based on nearest resident assuming that a resident may plant a new garden. This gives a more conservative dose estimate.

RADIOLOGICAL IMPACT TO THE ENVIRONMENT The radionuclides detected in some samples were from non-station, naturally occurring radionuclides.

All terrestrial samples collected as part of the MPS REMP did not show any station related isotopes.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 The seawater exiting the stations quarry is monitored for all station generated radionuclides.

Tritium was only found in seawater onsite inside the mixing zone of the quarry discharge at levels that were expected from routine station operation.

Offsite ambient radiation measurements using environmental TLDs beyond the site boundary ranged between 40 - 102 milliRoentgens (mrem) per year. The range of ambient radiation levels observed with the TLDs is consistent with natural background radiation levels for Connecticut.

RADIOLOGICAL IMPACT TO THE GENERAL PUBLIC During 2021, radiation doses to the general public as a result of Millstone's operation continued to be well below the federal limits and much less than the dose due to other sources of man-made (e.g., X-rays, medical) and naturally-occurring (e.g., cosmic, radon) radiation.

The calculated total body (whole body) dose to the maximally exposed member of the public from radioactive effluents and ambient radiation resulting from MPS operations for 2021 was approximately 0.242 mrem for the year. This conservative estimate is well below the Environmental Protection Agency's (EPA) annual dose limit to any member of the general public and is a fraction of a percent of the typical dose received from natural and other sources of man-made radiation.

CONCLUSIONS The 2021 REMP for MPS resulted in the collection and analysis of 699 environmental samples and measurements. The data obtained were used to determine the impact of Millstone's operation on the environment and on the general public.

An evaluation of direct radiation measurements, environmental sample analyses, and dose calculations indicates all applicable federal criteria were met with margin. Furthermore, radiation levels and the consequential dose from station operation were small in comparison to those attributed to naturally occurring and man-made background radiation.

Based on this information, there is no significant radiological impact on the environment or on the general public due to Millstone's operation. The 2021 REMP samples results are consistent with previous years with no trends evident.

ii

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

1. INTRODUCTION This section provides an overview of the MPS REMP. It also includes background information to allow a reader to have an informed understanding of radiation and nuclear power operation.

1 .1 Overview The 2021 REMP performed by Dominion Energy Nuclear Connecticut (DENC) for MPS is discussed in this report. Since the operation of a nuclear power station results in the release of small amounts of radioactivity and low levels of radiation, the Nuclear Regulatory Commission (NRC) requires by regulations and technical specifications that a program be established to monitor radiation and radioactivity in the environment (References 1, 6, 9, 10, & 11 ). This report published annually per Millstone's Technical Specifications (section 5.7.2 for MPS1, section 6.9.1.6a for MPS2 and Section 6.9.1.3 for MPS3), summarizes the results of measurements of radiation and radioactivity in the environment in the vicinity of the MPS and at distant locations during the period January 1, 2021 to December 31, 2021.

The REMP consists of taking radiation measurements and collecting samples from the environment, analyzing them for radioactivity content, and interpreting the results. With emphasis on the critical radiation exposure pathways to humans, samples from the aquatic, atmospheric, and terrestrial environments are collected. These samples include, but are not limited to: air, soil, well water, broadleaf vegetation, fruits, vegetables, seawater, bottom sediment, aquatic flora, fish, oysters, clams, and lobsters.

Thermoluminescent dosimeters (TLDs) are placed in the environment to measure gamma radiation levels. The TLDs are processed and the environmental samples are analyzed to measure the very low levels of radiation and radioactivity present in the environment as a result of MPS operation and other natural and man-made sources. These results are reviewed by Millstone's radiological staff and have been reported semiannually or annually to the NRC and others for over 30 years.

In order to more fully understand how a nuclear power station impacts humans and the environment, background information on radiation and radioactivity, natural and man-made sources of radiation, reactor operations, radioactive effluent controls, and radiological impact on humans is provided. It is believed that this information will assist the reader in understanding the radiological impact on the environment and humans from the operation of Millstone.

1.2 Radiation and Radioactivity All matter is made of atoms. Nuclear radiation is energy or particles that are given off from atoms in an excited state (e.g., unstable, radioactive atoms).

Radioactive material exists naturally and has always been a part of our environment. The earth's crust, for example, contains radioactive uranium, radium, thorium, and potassium. Some radioactivity is a result of fallout from nuclear weapons testing. Examples of radioactive fallout that could be present in environmental samples are cesium-137 and strontium-90. Some examples of radioactive materials released from a nuclear power station are hydrogen-3 (tritium),

cesium-137, iodine-131, strontium-90, and cobalt-60.

1-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Radiation is measured in units of mrem, much like temperature is measured in degrees. A mrem is a measure of the biological effect of the energy deposited in tissue. The letter 'm' is for 'milli',

or one-thousandth of a 'rem'. The word 'rem' is an acronym for roentgen equivalent man. One rem is equal to a 'rad' multiplied by factors to account for type of radiation and distribution within the body. The word 'rad' is an acronym for radiation absorbed dose. One rad is equal to the absorption of 100 ergs of energy per gram of tissue. The natural and man-made radiation dose received in one year by the average American is 300 to 600 mrem (References 2, 3, 4 & 5). The per capita dose has increased since the early 1980's because of the increased usage of medical procedures involving exposure to radiation (Reference 3).

Radioactivity is measured in Curies. Levels of radioactivity commonly seen in the environment are typically a small fraction of a Curie, therefore radioactivity in the environment is typically measured in picocuries. One picocurie (pCi) is one-trillionth of a Curie and is equal to 0.037 disintegrations per second (2.22 disintegrations per minute).

1.3 Sources of Radiation As mentioned previously, naturally occurring radioactivity has always been a part of our environment. Table 1.3-1 shows the sources and doses of radiation from natural and man- made sources.

Table 1.3-1 a Ia t'I0n S ources an d Correspon d'Ing A.ooroxImat e Doses (1)

Rd' NATURAL MAN-MADE Radiation Dose Radiation Dose Source (mrem/year) Source (mrem/year)

Internal, inhalation<2l 228 MedicaI<3> 300 External, space 33 Consumer<4> 12.3 Internal, ingestion 29 Industrial, security, 0.3 educational, research External, terrestrial 21 Occupational 0.5 Weapons Fallout <1 Nuclear Power Stations <1 Approximate Total 311 Approximate Total 314 (1) information from References 3 and 4 (2) from radon and thoron (3) includes computerized tomography (147 mrem), nuclear medicine (77 mrem), interventional fluoroscopy (43 mrem) and conventional radiography and fluoroscopy (33 mrem)

(4) primarily from cigarette smoking (4.6 mrem), commercial air travel (3.4 mrem), building materials (3.5 mrem) and mining and agriculture (0.8 mrem) 1-2

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Cosmic radiation (external, space) from the sun and outer space penetrates the earth's atmosphere and continuously bombards us with rays and charged particles. Some of this cosmic radiation interacts with gases and particles in the atmosphere, making them radioactive. These radioactive byproducts from cosmic ray bombardment are referred to as cosmogenic radionuclides. Isotopes such as beryllium-? and carbon-14 are formed in this way. Exposure to cosmic and cosmogenic sources of radioactivity results in about 33 mrem of radiation dose per year.

Additionally, natural radioactivity is in our body and in the food we eat (about 29 mrem/year),

the ground we walk on (about 21 mrem/year) and the air we breathe (about 228 mrem/year).

The majority of a person's annual dose results from exposure to radon and thoron in the air we breathe. These gases and their radioactive decay products arise from the decay of naturally occurring uranium, thorium and radium in the soil and building products such as brick, stone, and concrete. Radon and thoron levels vary greatly with location, primarily due to changes in the concentration of uranium and thorium in the soil. Residents at some locations in Colorado, New York, Pennsylvania, New Jersey, and even Connecticut have a higher annual dose as a result of higher levels of radon/thoron gases in these areas. In total, these various sources of naturally-occurring radiation and radioactivity contribute to a total dose of about 311 mrem per year.

In addition to natural radiation, we are normally exposed to radiation from a number of man-made sources. The single largest doses from man-made sources result from therapeutic and diagnostic applications of x-rays and radiopharmaceuticals. The annual dose to an individual in the United States from medical and dental exposure is approximately 300 mrem.

Consumer products/uses, such as cigarettes, building materials and commercial air travel contribute about 13 mrem/year. Much smaller doses result from weapons fallout (less than 1 mrem/year) and nuclear power stations (less than 1 mrem/year). Typically, the average person in the United States receives approximately 314 mrem per year from man-made sources.

1.4 Nuclear Reactor Operations MPS generates about 2100 megawatts of electricity at full power, which provides approximately one-third of the power consumed in the State of Connecticut. MPS2 and MPS3 are pressurized water reactors (MPS1, which is permanently shut down, was a boiling water reactor). The nuclear station is located on an approximate 500-acre site about three miles (five kilometers) west of New London, Connecticut. Commercial operation of MPS2 began in December 1975 and MPS3 in May 1986.

MPS was operational during most of 2021, with the exception of the MPS2 refueling outage in October, and the MPS3 down-power event in June. For 2021, the annual capacity factor for MPS2 was 90.85% and for MPS3 was 97.14%.

Nuclear-generated electricity is produced by many of the same techniques used for conventional oil and coal-generated electricity. Both systems use heat to boil water in order to produce steam.

The steam turns a turbine, which turns a generator, producing electricity. In both cases, the steam passes through a condenser where it changes back into water and re-circulates back through the system (see Figure 1.4-1 ). The cooling water source for MPS is the Niantic Bay.

1-3

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 The key difference between nuclear power and conventional power is the source of heat used to boil the water. Conventional stations burn fossil fuels in a boiler, while nuclear stations use uranium fission in a nuclear reactor.

Inside the reactor, a nuclear reaction called fission takes place. Particles, called neutrons, strike the nucleus of a uranium-235 atom, causing it to split into fragments called radioactive fission products. The splitting of the atoms releases both heat and more neutrons. The newly released neutrons then collide with and split other uranium atoms, thus making more heat and releasing even more neutrons, and on and on until the uranium fuel is depleted or spent. This process is called a chain reaction. When this chain reaction is self-sustaining, the reactor is called "critical."

The operation of a nuclear reactor results in the release of small amounts of radioactivity and low levels of radiation. The radioactivity originates from two major sources, radioactive fission products and radioactive activation products. Radioactive fission products, as illustrated in Figure 1.4-1, originate from the fissioning of the nuclear fuel. These fission products get into the reactor coolant from their release by minute amounts of uranium on the outside surfaces of the fuel cladding, by diffusion through the fuel pellets and cladding and, on occasion, through defects or failures in the fuel cladding. These fission products circulate along with the reactor coolant water and will deposit on the internal.surfaces of pipes and equipment. The radioactive fission products on the pipes and equipment emit radiation . Examples of some fission products are krypton-85 (Kr-85), strontium-90 (Sr-90), iodine-131 (1-131), xenon-133 (Xe-133), and cesium-137 (Cs-137).

Pressurized water reactor~

a common type of Light Water Reactor (LWR)

~

EAM GENERATOR' 1- - - - - - -* c o N DE N SER COOLING WATE R

..,__ _...;::= ~- -TAKING WAST E HEAT TO THE ENVIRONMENT Figure 1.4-1: SIMPLIFIED DIAGRAM OF A PRESSURIZED WATER REACTOR 1-4

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Nuclear Fission: fission is the splitting of atoms (e.g., uranium-235) by a neutron to release heat and more neutrons, creating a chain reaction. Radiation and fission products are by-products of the process as illustrated in Figure 1.4-2.

Uranium

~

Neutrons

'iL Neutron il **----...

Uranium ~i.~)T~

Fission Products Uranium 1-::

Neutrons

~

. * * ;<)

Fission Products Figure 1.4-2: Radioactive Fission Product Formation 1-5

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Radioactive activation products (Figure 1.4-3), on the other hand, originate from two sources.

The first is by neutron bombardment of the hydrogen, oxygen and other gas (helium, argon, nitrogen) molecules in the reactor cooling water. The second is a result of the fact that the internals of any piping system or component are subject to minute yet constant corrosion from the reactor cooling water. These minute metallic particles (for example: nickel, iron, cobalt, or magnesium) are transported through the reactor core into the fuel region, where neutrons may react with the nuclei of these particles, producing radioactive products. Therefore, activation products are nothing more than ordinary naturally- occurring atoms that are made unstable or radioactive by neutron bombardment. These activation products circulate along with the reactor coolant water and will deposit on the internal surfaces of pipes and equipment. The radioactive activation products on the pipes and equipment emit radiation. Examples of some activation products are manganese-54 (Mn-54), iron-59 (Fe-59), cobalt-60 (Co-60), and zinc-65 (Zn-65).

collision with 0

Co-59 Co-60 Stable Radioactive Neutron Cobalt Nucleus Cobalt Nucleus Figure 1.4-3: Radioactive Activation Product Formation At MPS there are five independent protective barriers that confine these radioactive materials.

These five barriers are:

• fuel pellets;

• fuel cladding;

• reactor vessel and associated piping and equipment;

• primary containment; and

• secondary containment (enclosure building).

1-6

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 The ceramic uranium fuel pellets provide the first barrier. Most of the radioactive fission products are either physically trapped or chemically bound between the uranium atoms, where they will remain. However, a few fission products that are volatile or gaseous may diffuse through the fuel pellets into small gaps between the pellets and the fuel cladding.

The second barrier, the fuel cladding, consists of zirconium alloy tubes that confine the fuel pellets. The small gaps between the fuel and the cladding contain the noble gases and volatile iodines that are types of radioactive fission products. This radioactivity can diffuse to a small extent through the fuel cladding into the reactor coolant water. Radioactivity can also escape into coolant water through cladding defects and failures.

The third barrier consists of the reactor pressure vessel, steel piping and equipment that confine the reactor cooling water. The reactor pressure vessel, which holds the reactor fuel, is typically a steel tank 40 feet high by 14 feet in diameter with walls about five to nine inches thick. These vessels and associated piping provide containment for radioactivity in the primary coolant and the reactor core. However, during the course of operations and maintenance, small amounts of radioactive fission and activation products can escape through valve leaks or upon breaching of the primary coolant system for maintenance.

The fourth barrier is the primary containment. It is a cylindrical enclosure with approximately five-foot thick steel reinforced concrete walls lined by steel on the inside. During operation the containment is closed but small amounts of radioactivity may be released from primary containment by venting during operation to maintain proper containment pressure. During maintenance and refueling outages containment is open and small amounts of radioactivity is released during this time when the fuel has been moved out of the reactor cavity in containment.

The fifth barrier is the secondary containment or enclosure building. The enclosure building is a steel building that surrounds the primary containment. This barrier is an additional safety feature at Millstone's reactor units to contain radioactivity that may escape from the primary containment.

This enclosure building is equipped with a filtered ventilation system that is used when needed to reduce the radioactivity that escapes from the primary containment.

The five barriers confine most of the radioactive fission and activation products. However, small amounts of radioactivity do escape via mechanical failures and maintenance on valves, piping, and equipment associated with the reactor cooling water system. The small amounts of radioactive liquids and gases that do escape the various containment systems are further controlled by the liquid purification and ventilation filtration systems. The control of radioactive effluents at MPS will be discussed in more detail in the next section.

1-7

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 1.5 Radioactive Effluent Control The small amounts of radioactive liquids and gases that might escape the first two barriers are processed in the liquid and gaseous waste treatment systems, then monitored for radioactivity, and released only if the radioactivity levels are below the federal release limits.

Radioactivity released from the liquid effluent system to the environment is limited, controlled and monitored by a variety of systems and procedures which include:

• reactor water cleanup system;

• liquid radioactive waste treatment system;

• sampling and analysis of the liquid radioactive waste tanks; and

• liquid waste effluent discharge radioactivity monitor.

The purpose of the reactor water cleanup system is to continuously purify the reactor cooling water by removing radioactive atoms and non-radioactive impurities that may become activated by neutron bombardment. A slip stream of the reactor coolant water is diverted from the primary coolant system and is directed through ion exchange resins where radioactive elements, dissolved and suspended in the water, are removed through chemical processes.

The net effect is a substantial reduction of the radioactive material that is present in the primary coolant water and consequently the amount of radioactive material that might escape from the system.

Reactor cooling water that might escape the primary cooling system and other radioactive water sources are collected in floor and equipment drains. These drains direct this radioactive liquid waste to large holdup tanks. The liquid waste collected in the tanks is purified again using the liquid radioactive waste treatment system, which consists of a filter and ion exchange resins.

Processing of liquid radioactive waste results in large reductions of radioactivity in liquids discharged into Niantic Bay. Wastes processed through liquid radioactive waste treatment can be purified and, in some cases, re-used in station systems.

Prior to release, the radioactivity in any liquid radioactive waste tank is sampled and analyzed to determine if the level of radioactivity is below the release limits and to quantify the total amount of radioactive liquid effluent that will be released. If the levels are below the federal release limits, the tank is drained to the liquid effluent discharge header.

This liquid waste effluent discharge line is provided with a shielded radioactivity monitor. This detector is connected to a radiation level meter and a recorder in the Control Room. The radiation alarm is set so that the detector will alarm before radioactivity levels exceed the release limits. In addition to the alarm function, the radiation monitor also signals both discharge valves to close thus terminating the discharge release to the environment. Gamma spectroscopy analysis, tritium analysis and the effluent radiation monitors prevent any liquid radioactivity from being released in excess of release rate and total activity limits. An audible alarm notifies the Control Room operator that this has occurred.

Some liquid waste sources, which have a low potential for containing radioactivity, and/or may contain very low levels of contamination, may be discharged directly to the environment.

One such source of liquid is the turbine building sump. However, periodic representative samples are collected for analysis of radioactivity content to track the amounts of radioactivity being discharged.

1-8

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 The preceding discussion illustrates that many controls exist to reduce the radioactive liquid effluents released to the environment to as far below the release limits as is reasonably achievable.

Radioactive releases from the radioactive gaseous effluent system to the environment are limited, controlled, and monitored by a variety of systems and procedures which include:

• containment building ventilation system;

• containment building radioactivity monitors;

• sampling and analysis of containment building vent and purge effluents;

• process gas treatment system;

• auxiliary building (and engineered safeguards and fuel building for MPS3) ventilation system;

• MPS stack and units' vent effluent radioactivity monitors;

• sampling and analysis of MPS stack and units' vent effluents;

• process radiation monitors; and

• steam jet air ejector (SJAE) monitor.

The primary sources of gaseous radioactive waste are degassing of the primary coolant, gaseous liquid drains, and gaseous vents. Additional sources of gaseous waste activity include ventilation air released from the auxiliary building and purging and venting of the containment building. The radiation level meter and recorders for the effluent radioactivity monitors are located in the Control Room. The station process computer aids in tracking the monitor readings. To supplement the information continuously provided by the detector, air samples are taken periodically from the units' containments, MPS stack and units' vents. These samples are analyzed to quantify the total amount of radioactive gases, radioactive iodines, radioactive particulate, and tritium released in gaseous effluents.

Gases from the primary coolant are held up in waste gas decay tanks for decay at MPS2.

Gaseous waste at MPS3 is purified through a process gas system, consisting of high-efficiency particulate air filters and charcoal absorber beds. Gases from periodic venting of the MPS2 containment are released through a similar process system (Enclosure Building Filtration System) while gases from the MPS3 containment vacuum pumps are released without treatment.

If necessary, MPS3 containment air can be filtered by an internal particulate and charcoal treatment system. Containment purges (purge is the forced ventilation process while containment vents are pressure releases) for MPS2 are filtered by high-efficiency particulate filters while at MPS3 these are not normally filtered. If necessary, particulate and charcoal filters can be used for these purges.

Normally, for MPS2, the air released from the unit vent is from the ventilation of the auxiliary (which includes the fuel pool), service and enclosure buildings. For MPS2, fuel pool and enclosure building ventilation can be redirected to the MPS Site Stack. Normally, for MPS3, the air released from the unit vent is from the ventilation of the auxiliary, fuel, service, waste disposal and enclosure buildings. For MPS3, enclosure building ventilation can be redirected to the MPS Site Stack.

1-9

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Therefore, for both liquid and gaseous releases, radioactive effluent control systems exist to collect and purify the radioactive effluents in order to reduce releases to the environment to as low as is reasonably achievable. The effluents are always monitored, sampled and analyzed to make sure that radioactivity levels are below the release limits. If the release limits are being approached, isolation valves are closed to stop the release and ensure that federal regulatory limits are always met.

1.6 Radiological Impact on Humans The final step in the effluent control process is the determination of the radiological dose impact to humans and comparison with the federal dose limits to the public. As mentioned previously, the purpose of continuous radiation monitoring and periodic sampling and analysis is to measure the quantities of radioactivity being released to determine compliance with the radioactivity release limits. This is the first stage for assessing releases to the environment.

The second stage is calculation of the dose impact to the general public from MPS's radioactive effluents. The purpose of this calculation is to periodically assess the dose to the general public resulting from radioactive effluents to ensure that the dose is being maintained as far below the federal dose limit as is reasonably achievable. This is the second stage for assessing releases to the environment.

The types and quantities of radioactive liquid and gaseous effluents released from MPS during each year are reported to the NRC annually in the Radiological Effluent Release Report (RERR).

Similar to this report, the RERR is submitted annually to the NRC. The liquid and gaseous effluents were well below the federal release limits and were a small percentage of the MPS REMODCM effluent control limits.

The measurements of the physical and chemical nature of the effluents are used to determine how the radionuclides will interact with the environment and how they can result in radiation exposure to humans. The environmental interaction mechanisms depend upon factors such as the hydrological (water) and meteorological (atmospheric) characteristics in the area.

Information on the water flow, wind speed, wind direction, and atmospheric mixing characteristics are used to estimate how radioactivity will distribute and disperse in the ocean and the atmosphere.

The most important type of information that is used to evaluate the radiological impact on humans is data on the use of the environment. Information on fish and shellfish consumption, boating usage, beach usage, locations of cows and goats, locations of residences, locations of gardens, and other usage information are utilized to estimate the amount of radiation and radioactivity received by the general public.

The radiation exposure pathway to humans is the path radioactivity takes from its release point at MPS to its effect on man. The movement of radioactivity through the environment and its transport to humans is portrayed in Figure 1.6-1.

1-10

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 EXAMPLES OF Millstone's RADIATION EXPOSURE PATHWAYS LIQUID EFFLUENTS DIRECT RADIATION IL DEPOSITION)

• ~

~-

?c

3. DIRECT RADIATION (STATION) , 2. AIR INHALATION

1. DIRECT RADIATION V

(AIR SUBMERSION)

~

1. SHORELINE DIRECT RADIATION (FISHING, PICNIC.ING) ~ 5. CONSUMPTION (VEGETATION)

~

DEPOSITION

2. DIRECT RADIATION (OAT; (IMMERSION IN OCEAN, SWIMMING)

(I

&affl~~

DEPOSITION INGESTION

3. CONSU (FISH, S Figure 1.6-1: Radiation Exposure Pathways 1-11

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 There are four pathways in which liquid effluents affect humans:

• external radiation from liquid effluents that deposits and accumulates on the shoreline;

• external radiation during boating from radioactivity in ocean water;

• external radiation from immersion in ocean water containing radioactivity; and

• internal radiation from consumption of fish and shellfish containing radioactivity absorbed from the liquid effluents.

There are six major pathways in which gaseous effluents affect humans:

• external radiation from immersion in an airborne plume of radioactivity;

• external radiation from shine from an overhead, airborne plume of radioactivity;

• internal radiation from inhalation of airborne radioactivity;

• external radiation from deposition of radioactive effluents on the ground;

• internal radiation from consumption of vegetation containing radioactivity deposited on the vegetation from airborne deposition and absorbed from the soil due to ground deposition of radioactive effluents; and

• internal radiation from consumption of milk and meat containing radioactivity deposited on forage that is eaten by cattle and other livestock.

Drinking water is not a pathway of exposure for radioactivity released in liquid or gaseous effluents from Millstone. All liquid effluents are released to either Long Island Sound or Niantic Bay. Both are saltwater bodies which are not used as sources of drinking water. The closest reservoir is Lake Konomoc, 6.5 miles from Millstone. Radioactivity deposited in the reservoir from MPS gaseous effluents would not yield a significant dose to the public compared to doses from the six major pathways listed.

Ambient (direct) radiation emitted from sources of radioactivity at MPS comes from low- level radioactive waste being processed and stored at the site prior to shipping and disposal. Also, the operation of the Independent Spent Fuel Storage Installation (ISFSI) which began in 2005 results in a small amount of direct radiation at the site boundary.

The radiological dose impact on humans is based both on effluent analyses and modeling and on direct measurements of radiation and radioactivity in the environment. However, the operation of MPS results in releases of only small amounts of radioactivity, and, as a result of dilution in the atmosphere and ocean, even the most sensitive radioactivity measurement and analysis techniques cannot usually detect these tiny amounts of radioactivity above that which is naturally present in the environment. Therefore, radiation doses are calculated using radioactive effluent release data and computerized dose calculations that are based on conservative NRG-recommended models that tend to result in over-estimates of the resulting dose. These computerized dose calculations are performed by DENG personnel. These computer codes use the guidelines and methodology set forth by the NRG in Regulatory Guide 1.109 (Reference 7).

The dose calculations are specified in the Millstone's REMODGM (Reference 8), which has been reviewed by the NRG.

It should be emphasized that the conservative assumptions made in the computer code calculations; the maximum hypothetical dose to an individual is considerably higher than the dose that would actually be received by a real individual.

1-12

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 After dose calculations are performed, the results are compared to the dose limits for the public as specified in NRC's technical specifications for MPS (References 9-11).

The technical specifications limits for the dose to a member of the general public from radioactive material in liquid effluents released to unrestricted areas are:

• less than or equal to 3 mrem per year to the total body; and,

• less than or equal to 10 mrem per year to any organ.

The technical specifications limits for dose due to release of radioactivity in gaseous effluents is restricted to:

• less than or equal to 10 mrad per year for gamma radiation from noble gases;

• less than or equal to 20 mrad per year for beta radiation from noble gases; and

• less than or equal to 15 mrem per year to any organ from iodine-131, iodine-133, tritium, and all particulate radionuclides with half-lives greater than 8 days.

The Technical Specifications limits for total dose from all three MPS units due to release of radioactivity in gaseous and liquid effluents and direct radiation is restricted to:

• less than or equal to 25 mrem per year to the total body;

• less than or equal to 75 mrem per year to the thyroid; and

• less than or equal to 25 mrem per year to any other organ.

1-13

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

2. PROGRAM DESCRIPTION 2.1 Sampling Schedule and Locations The sample locations, types, and frequency of analysis are given in Tables 2.1-1 and 2.1-2 and are shown in Figures 2.1-1 and 2.1-2. The program as described in Table 2.1-1 lists the required samples collected as specified in the REMODCM, as well as any other extra samples collected under the program.

2-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Table 2,1-1 Environmental Monitoring Program sampling Types and Locations Distance, No.- Direction From Type* Location Name Release Point** Sample Media 1-1 Onsite - NAP Parking Lot N 0.6Mi, NNW TLD, Air Particulate, Iodine, Vegetation 2-1 Onsite - Weather Shack 0.3Mi, S TLD, Air Particulate, Iodine 3-1 Onsite - Bird Sanctuary 0.3Mi, NE TLD, Air Particulate, Iodine, Soil 4-1 Onsite - Albacore Drive 1.0Mi, N TLD, Air Particulate, Iodine, Soil 5-1 Onsite - Quarry East 0.1 Mi, SSE TLD 6-1 Onsite - Quarry Discharge 0.3Mi, SSE TLD 7-1 Onsite - Env. Lab Dock 0.3 Mi, SE TLD 8-1 Onsite - Env. Lab 0.3 Mi, SE TLD 9-1 Onsite - Bay Point Beach 0.4Mi, W TLD 10-1 Goshen Fire Dept. 1.2 Mi, E TLD, Air Particulate, Iodine, Vegetation 11-1 Great Neck Country Club 1.6 Mi, ENE TLD, Air Particulate, Iodine 13-C Mystic, CT 11.5 Mi, ENE TLD 14-C Ledyard, CT 12.0 Mi, NE TLD, Soil 15-C Norwich, CT 14.0 Mi, N TLD, Air Particulate, Iodine 16-C Old Lyme, CT - Halls Rd. 8.8Mi,W TLD 17-1 Site Boundary 0.5 Mi, NE Vegetation 25-1 Fruits & Vegetables < 10 Miles Vegetation 26-C Fruits & Vegetables > 10 Miles Vegetation 27-1 East Lyme Police Dept. 1.7Mi,WNW TLD, Air Particulate, Iodine 1

28-1 Two Tree Island 1 0.8 Mi, SSE Fish 1

29-1 West Jordan Cove 1  ::; 0.5 Mi, ENE to ESE Clams, Fucus, Fish 31-1 Niantic Shoals 1.8 Mi, NW Bottom Sediment, Clams 1

32-1 Vicinity of Discharge 1,2 Bottom Sediment, Fish , Seawater, Aquatic Flora 33-1 Seaside Point 1.8 Mi, ESE Bottom Sediment 34-1 Thames River Yacht Club 4.0 Mi, ENE Bottom Sediment 35-1 Niantic Bay :s;0.5 Mi, SSW to W Lobster, Fish1, Aquatic Flora 36-C Black Point 2.7Mi,WSW Aquatic Flora 37-C Giant's Neck 3.5Mi,WSW Bottom Sediment, Seawater 41-1 Waterford - Myrock Avenue 3.2 Mi, ENE TLD 42-1 East Lyme - Billow Road 2.4Mi, WSW TLD 43-1 East Lyme-Old Black Point 2.6Mi,SW TLD 44-1 Onsite - Schoolhouse 0.1 Mi, NNE TLD 45-1 Onsite - Access Road #1 0.5Mi, NNW TLD 46-1 Old Lyme - Hillcrest Ave. 4.6Mi,WSW TLD 47-1 East Lyme -W. Main St. 4.5Mi,W TLD 48-1 East Lyme - Corey & Roxbury 3.4Mi, WNW TLD 49-1 East Lyme - Society Rd. 3.6Mi, NW TLD 50-1 East Lyme - Manwaring Rd & 2.1 Mi, W TLD Terrace Ave 51-1 East Lyme - Smith Ave. 1.5 Mi, NW TLD 52-1 Waterford - River Rd. 1.1 Mi, NNW TLD 53-1 Waterford - Gardiners Wood Rd 1.4 Mi, NNE TLD 55-1 Waterford - Magonk Point 1.8 Mi, ESE TLD 56-1 New London - Ocean & Mott 3.7Mi, E TLD Ave.

1, Fish required to be sampled from one of three other locations (#28, #29 or #32).

2. Vicinity of discharge includes the Quarry and shoreline area from Fox Island to western point of Red Barn recreation Area and Offshore out to 500 feet.

Footnotes:

• I = Indicator; C = Control, X - Extra - sample not required by the REMODCM

• • = The release points are the Millstone Stack for terrestrial location and the end of the quarry for aquatic location.

2-2

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Table 2,1-1 Environmental Monitoring Program Sampling Types and Locations

,continues)

No.- Distance, Direction From 1

Type Location Name Release Point2 Sample Media 57-1 New London - Ocean Ave. 3.6Mi, ENE TLD 59-1 Waterford -Miner Ave. 3.4 Mi, NNE TLD 60-1 Waterford-Parkway South&Cross 4.0Mi, N TLD 61-1 Waterford-Oil Mill&Boston Post 4.3Mi, NNW TLD 62-1 East Lyme - Columbus Ave. 1.9Mi,WNW TLD Waterford - Gardiners Wood &

63-1 0.8 Mi, NE TLD Jordon Cove 64-1 Waterford - Shore Rd. 1.1Mi,ENE TLD 65-1 Waterford - Boston Post Rd. 3.2 Mi, NE TLD 66-X NAP Parking Lot - Fit Center 0.4Mi, NW TLD 71-1 1-MW-XFMR-03 Onsite Well Water 72-1 MW-GPl-1 Onsite Well Water 73-X Site Switchyard Fence 0.3Mi,N TLD 74-X Ball Field Foul Pole 0.6Mi, N TLD 75-X Waterford - Windward Way & 0.5Mi, NE TLD Shotgun 76-X ISFSl-1 Up-gradient of ISFSI Well Water 77-X ISFSl-2 Down-gradient of ISFSI Well Water 78-X ISFSl-3 Down-gradient of ISFSI Well Water 79-1 M3-MW-1 Onsite Well Water 81-1 S2-MW-1 Onsite Well Water 82-1 MW-6B Onsite Well Water 83-1 S3-MW-2 Onsite Well Water 89-C Aquatic background >4 miles of discharge Lobster

1. Fish required to be sampled from one of three other locations (#28, #29 or #32).

2. Vicinity of discharge includes the Quarry and shoreline area from Fox Island to western point of Red Barn recreation Area and Offshore out to 500 feet.

Footnotes:

• I Indicator; C Control, X - Extra - sample not required by the REMODCM

• • = The release points are the Millstone Stack for terrestrial location and the end of the quarry for aquatic location.

2-3

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Table 2.1-2 Required sampHnq frequency & Type of Analysis Exposure Pathway No.of Sampling & Collection Frequency Type of and/or Sample Locations Analysis

1. Gamma Dose- 1 Quarterly Gamma Dose - Quarterly 39 Environmental TLD

2. Airborne Particulate 8 Continuous sampler - filter change Gross Beta - Every two every two weeks weeks Gamma Spectrum

- Quarterly on composite (by location), and on individual sample if gross beta is greater than 10 times the mean of the weekly control station's gross beta results

3. Airborne Iodine 8 Continuous sampler - canister 1-131 - Every two weeks change every two weeks

4. Vegetation 5 One sample near middle and one Gamma Isotopic on each near end of growing season sample

5. Reserved

6. Sea Water 2 Continuous sampler with a monthly Gamma Isotopic and collection at indicator location. Tritium on each sample.

Quarterly at control location -

Composite of 6 weekly grab

7. Well Water 6 Semiannual Gamma Isotopic and Tritium on each sample

8. Bottom Sediment 5 Semiannual Gamma Isotopic on each sample

9. Soil 3 Annually Gamma Isotopic on each sample

10. Fin Fish 2 Semiannual Gamma Isotopic on each sample (edible portion)

11. Aquatic flora (fucus) 4 Quarterly Gamma isotopic on each sample

13. Clams 2 Semiannual Gamma Isotopic on each (edible portion) sample

14. Lobster 2 Semiannual Gamma Isotopic on each (edible portion) sample Footnotes

1. Two or more TLDs or TLD with two or more elements per location.

Oysters were previously Sample#12, REMODCM revision 27.

2-4

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 figure 2,1-1, "Inner TLP, Air, Grass, Soil, and Aquatic Locations" 2-5

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 figure 2.1-2. "Outer IbP and Aquatic Locations" 2-6

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 2.2 Samples Collected During Report Period The following table summarizes the number of samples of each type collected and analyzed during 2021:

Iablg 2.2-j BEDllP ~s1m12lg1 Cgllg,tgg ill 2Q2j Number of Number of Technical Technical Number of Extra Sample Type Specification Specification Samples Analyzed Required Samples Required Samples Analyzed Gamma Exposure 156 156 14 (Environmental TLD)

Air Particulates 208 208 0 Air Iodine 208 208 0 Soil 3 3 0 Milk (cow) 0 0 0 Milk (goat) 0 0 0 Well Water 12 12 24 Vegetation 10 10 6 Sea Water 16 16 0 Bottom Sediment 10 10 0 Aquatic Flora 16 16 0 Fish 4 4 0 Oysters 0 0 4 Clams 4 4 0 Lobster 4 4 0 Total All Types 651 651 48 2.3 Required Samples Not Collected During the Report Period During 2021 all required samples were obtained as listed in Table 2.2-1.

Prior to 2018, milk sampling was performed as an extra sample. The 2021 Land Use Census did not locate any milk farms producers within ten miles of Millstone Power Station. As a substitute for milk samples, strontium analysis of air samples and gamma analysis of broad leaf vegetation were performed.

2-7

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

3. RADIOCHEMICAL RESULTS 3.1 Summary Table In accordance with the REMODCM,Section I.F.1, a summary table of the radiochemical results has been prepared and is presented on the following pages. The mean and range recorded are based only upon detectable measurements.

A more detailed analysis of the data is given in Section 4.0 where a discussion of the variations in the data explains many aspects that are not evident in the Summary Table because of the basic limitation of data summaries. The data summaries include the extra ("X") samples collected throughout the year. These samples are taken to enhance the monitoring program or replace samples from required locations when they are not available.

Furthermore, in accordance with the REMODCM, Section 1.E.3, an inter-laboratory comparison was performed by Teledyne Brown Engineering Environmental Services (TBE-ES) as part of their quality assurance program for environmental monitoring in order to demonstrate that the results are reasonably valid (Appendix B). Quality Control of radioanalyses involves TBE-ES internal process control program and independent third party programs administered by Analytics and Environmental Resource Associates (ERA) and Department of Energy's (DOE)

Mixed Analyte Performance Evaluation Program (MAPEP).

The Teledyne inter-laboratory comparison report concluded that 146 out of 154 quality assurance analyses performed met the specified acceptance criteria. Eight analyses did not meet the specified acceptance criteria addressed in Teledyne Non-Conformance Reports (NCRs), listed in Appendix B. A review of the Teledyne NCRs was performed and none of the seven analysis failures were found to adversely affect any of Millstone samples results and data accuracy.

3-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2021 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled Analysis Total LLD* Number Number (Units) Type Number Mean (Range)

Location Number I Distance Direction Number Mean (Range)

Mean (Range)

Direct Gamma 170 NA 155 8 0.3Mi. 4 15 Radiation Dose 7.7 SE 11.2 7.6 TLD (uR/hr) (4.6-11.7) (10.8-11.7) (5.8-9.2)

Air Iodine 1-131 208 0.07 182 NA NA <LLD 26 (pCilm 3 ) <LLD <LLD Air Particulate GR-8 208 0.01 182 2 0.3 Mi. 26 26 (pCilm 3 ) 0.0139 s 0.0141 0.014 (0. 007-0. 0208) (0.007-0.021) (0.0088-0.0197)

SR-89 32 0.1 28 NA NA <LLD 4

<LLD <LLD SR-90 32 0.01 28 NA NA <LLD 4

<LLD <LLD GAMMA 32 BE-7 NA 28 27 1.7 Mi. 4 4 0.1072 WNW 0.122 0.1052 (0.0852-0.1462) (0.1040-0.1462) (0.0931-0.1164)

Other Note 2 <LLD NA NA <LLD <LLD Gammas Soil GAMMA 3 (pCilg dry) K-40 NA 2 14 12.0 Mi.

14.025 NE 17.350 17.350 (13.710-14.340) (<LLD-17.350) (<LLD-17.350)

CS-137 0.18 2 NA NA <LLD

<LLD <LLD Ac-228 NA 1/2 4 1.0Mi.

1.481 N 1.481 1.291

(<LLD-1.481) (<LLD-1.481) (<LLD-1.291)

Other Note 3 <LLD NA NA <LLD <LLD Gammas 3-2

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2021 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled (Units)

Analysis Type Total Number LLD* Number Mean (Range)

Location Number I Distance Direction Number Mean (Range)

Number Mean (Range)

Cow Milk SR-89 10 (pCi/1)

SR-90 2 GAMMA Milk was not available for collection in 2021, as a substitute, K-40 NA Strontium Analysis of Air Particulate filters was performed Other Note4 Gammas Goat Milk SR-89 10 (pCi/1)

SR-90 2 GAMMA Milk was not available for collection in 2021, as a substitute, K-40 NA Strontium Analysis of Air Particulate filters was performed Other Note4 Gammas Well Water H-3 36 2000 36 NA NA <LLD NA (pCi/1) <LLD GAMMA 36 K-40 NA 36 NA NA <LLD NA

<LLD Other Note 5 <LLD NA NA <LLD NA Gammas Fruits & Vegetables GAMMA 8 (pCilg 11et) Be-7 NA 1/4 25 Within 10 Miles 1/4 4 0.528 0.528 <LLD

(<LLD-0.528) (<LLD-0.528)

K-40 NA 4 25 Within 1O Miles 4 4 1.789 1.789 1.646 (0.837-2.584) (0.837-2.584) (0.839-3.077)

Other Note6 <LLD NA NA <LLD <LLD Gammas 3-3

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2021 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled Analysis Total LLD* Number Number (Units) Type Number Mean Distance Number Mean Broad Leaf Vegetation GAMMA 8 (Range)

Location!

Number Direction I Mean (Range) (Range)

(pCi/g 11-/) BE-7 NA 5/6 0.6M. 1/2 2 1.725 NNW 3.848 1.963 (0.625-3.848) ( <LLD-3.848) (1.129-2.797}

K-40 NA 6 26 Beyond 10 miles 2 2 3.184 4.486 4.486 (2.635-3.505) ( 4.259-4.712) (4.259-4.712)

Ac-228 NA 6 NA NA <LLD 2

<LLD <LLD Other Notes <LLD NA NA <LLD <LLD Gammas Sea Water H-3 16 3000 7/12 32 <0.1 M 7/12 4 (pCi/1) 718 718 <LLD (319-1060) (319-1060)

GAMMA 16 K-40 NA 12 32 <0.1 M 12 4 281 281 252 (187-378) (187-378) (188-296)

Other Note 5 <LLD NA NA <LLD <LLD Gammas Bottom Sediment GAMMA 10 (pCilg dry) K-40 NA 8 32 <0.1 M 2 2 15.33 16.66 15.33 (12.28-19.99) (13.32-19.99) (15.08-15.58)

Ac-228 2/8 32 <0.1M 1/2 2 0.701 0.870 <LLD (0.532-0.87} (<LLD-0.870)

Other Note 3 <LLD NA NA <LLD <LLD Gammas 3-4

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2021 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled Analysis Total LLD* Number Number (Units) Type Number Mean Location Distance Number Mean (Range) Number Direction Mean (Range) (Range)

Aquatic Flora GAMMA 16 (pCi/g v..et) BE-7 NA 3/12 29 s0.5 M. 1/4 4 0.3679 ENE to ESE 0.4267 <LLD (0.3220-0.4267) ( <LLD-0.4267)

K-40 NA 12 32 <0.1 M 4 4 6.5741 7.4725 5.8285 (4.4730-9.8400) (5.4450-9.8400) (4.7220-8.7310) 1-131 0.06 12 NA NA <LLD 4

<LLD <LLD other Note6 <LLD NA NA <LLD <LLD Gammas Fish - Other GAMMA 4 (pCi/g v..et) K-40 NA 4 35 SO.SM 2 3.567 SSWtoW 3.830 NA (3.135-4.306) (3.353-4.306) other Note 8 <LLD NA NA <LLD NA Gammas Oysters GAMMA 4 (pCilg v..et) K-40 NA 2 31 1.8 M. 2 2 2.157 NW 2.157 1.930 (1.907-2.407) (1.907-2.407) (1.651-2.208) other Note 8 <LLD NA NA <LLD <LLD Gammas Clams GAMMA 4 (pCilg v..et) K-40 NA 4 31 1.8 M. 2 1.817 NW 2.057 NA (1.538-2.078) (2.036-2.078) other Note8 <LLD NA NA <LLD NA Gammas Lobster GAMMA 4 (pCilg v..et) K-40 NA 2 35 S0.5 M 2 2 3.336 SSWtoW 3.336 2.229 (3.179-3.492) (3.179-3.492) (2.202-2.255) other Note8 <LLD NA NA <LLD <LLD Gammas 3-5

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 NOTES FOR

SUMMARY

TABLE 1 - (*) The required LLD is the smallest concentration of radioactivity that will be detected with 95% confidence that the activity is real. See detailed discussion below.

2 - LLDs for air particulate gamma are 0.05 pCi/M3 for Cs-134 and 0.06 pCi/M3 for Cs-137.

3 - LLD for soil and sediment gamma is 0.15 pCi/g for Cs-134.

4 - LLDs for milk gamma are 1 pCi/I for 1-131, 15 pCi/I for Cs-134, 18 pCi/I for Cs-137, 70 pCi/I for Ba-140 and 25 pCi/I for La-140.

5- LLDs for water gamma are 15 pCi/I for Mn-54, Co-58, Co-60, Nb-95, 1-131, Cs-134 and La-140; 30 pCi/I for Fe-59, Zn-65 and Zr-95; 18 pCi/I for Cs-137 and 60 pCi/I for Ba-140.

6 - LLDs for fruits & vegetables, broadleaf vegetation and aquatic flora for gamma are 0.06 pCi/M3 for 1-131, 0.06 pCi/M3 for Cs-134 and 0.08 pCi/M3 for Cs-137.

7 - LLDs for other gamma are 0.06 pCi/g for Cs-134 and 1-131.

8 - LLDs for fish and shellfish for gammas are 0.13 pCi/g for Mn-54, Co-58, Co-60 and Cs-134; 0.26 pCi/g for Fe-59 and Zn-65; 0.15 pCi/g for Cs-137; and 0.93 pCi/g for 1-131.

Discussion of LLD The LLD at a confidence level of 95% is the smallest concentration of radioactive material in a sample that will be detected with a 5% probability of falsely concluding that a blank observation represents a "real" signal.

For a particular measurement system (which may include radiochemical separation):

LLD= _ _ _ _4_.6_6_S_b _ __

E

• V* 2.22

• Y* exp(-1M)

LLD is the lower limit of detection as defined above (as pCi per unit mass or volume) sb is the standard deviation of the background counting rate or of the counting rate of a blank sample as appropriate (as counts per minute)

E is the counting efficiency (as counts per transformation)

V is the sample size (in units of mass or volume) 2.22 is the number of transformations per minute per picoCurie Y is the fractional radiochemical yield (when applicable)

'A is the radioactive decay constant for the particular radionuclide

~t is the elapsed time between sample collection (or end of the sample collection period) and time of counting The LLD is defined as "a priori" (before the fact) limit representing the capability of a measurement system and not an "a posteriori" (after the fact) limit for a particular measurement.

Analyses were performed in such a manner that the stated LLDs were achieved under routine conditions. Occasionally background fluctuations, unavoidably small sample sizes, the presence of interfering nuclides, or other uncontrollable circumstances may have rendered these a priori LLDs unachievable. In such cases, the contributing factors are identified and described in this report. As shown in the equation above, for composite samples taken over a period of time, the LLD is decayed to the end of the sample period.

3-6

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 3.2 Data Tables The data reported in this section are results of analyses on all samples. All gamma exposure rates (Table 1) and air beta results (Table 2) are positive because of natural radioactivity. For all other results positive results are shown as bolded type. Results are considered positive when the measured value exceeds 1.5 times the listed 2cr error (i.e., the measured value exceeds 3cr).

The reported error is two times the standard deviation (2cr) of the net activity. Unless otherwise noted, the overall error (counting, sample size, chemistry, errors, etc.) is estimated to be 2 to 5 times that listed. Because of counting statistics, negative values, zeros and numbers below the Minimum Detectable Level (MDL) are statistically valid pieces of data. For the purposes of this report, in order to indicate any background biases, all the valid data are presented. This practice was recommended by Health and Safety Laboratory (HASL) ("Reporting of Analytical Results from HASL," letter by Leo B. Higginbotham), NUREG 0475 and NUREG/CR-4007 (Sept. 1984).

Data are given according to sample type as indicated below.

1. Gamma Exposure Rate

2. Air Particulates, Gross Beta Radioactivity

3. Air Particulates, Airborne 1-131

4. Air Particulates, Gamma Spectra

5. Soil

6. Milk

7. Well Water

8. Fruits & Vegetables

9. Broad Leaf Vegetation

10. Seawater

11. Bottom Sediment

12. Aquatic Flora (Fucus)

13. Fin Fish

14. Oysters

15. Clams

16. Lobster 3-7

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 1 QUARTERLY GAMMA EXPOSURE RATE (uR/hr)*

LOCATIONS PERIOD 1 2 3 4 5 6 7 8 9 10 11

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

1Q 7.6 0.4 11.0 0.5 7.0 0.3 7.9 0.3 8.9 0.4 8.5 0.3 4.9 0.2 11.0 0.4 10.5 0.5 9.7 0.6 7.1 0.3 2Q 7.7 0.2 10.9 0.3 6.9 0.2 7.8 0.2 8.8 0.2 8.1 0.3 4.6 0.1 10.8 0.3 10.9 0.4 9.9 0.4 6.7 0.2 3Q 8.3 0.3 10.7 0.5 7.8 0.3 8.5 0.2 9.7 0.4 8.8 0.2 4.9 0.2 11.7 0.2 11.2 0.2 10.3 0.3 7.2 0.3 4Q 8.0 0.3 9.8 0.3 7.6 0.2 8.2 0.4 9.3 0.2 8.7 0.2 4.9 0.2 11.3 0.5 11.4 0.4 9.7 0.2 7.0 0.2 PERIOD 13C 14C 15C 16C 27 41 42 43 44 45 46

--- (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

1Q 8.8 0.3 8.3 0.5 7.0 0.4 5.8 0.2 7.0 0.2 7.1 0.3 6.9 0.4 7.0 0.3 7.8 0.3 7.1 0.4 8.3 0.3 2Q 8.9 0.2 9.2 0.3 7.2 0.4 5.8 0.2 7.1 0.2 6.5 0.3 7.2 0.3 6.9 0.2 7.5 0.2 7.1 0.3 8.3 0.2 3Q 9.0 0.4 9.1 0.5 7.6 0.2 6.0 0.2 7.6 0.5 7.2 0.1 7.3 0.2 7.1 0.2 7.7 0.1 7.6 0.3 8.4 0.3 4Q 8.5 0.2 (a) 7.3 0.2 6.0 0.2 7.5 0.2 6.9 0.2 7.1 0.2 7.1 0.3 7.6 0.2 7.3 0.2 7.9 0.2 PERIOD 47 48 49 50 51 52 53 55 56 57 59

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

1Q 7.8 0.3 8.7 0.6 7.2 0.3 7.2 0.4 6.3 0.3 7.0 0.3 7.2 0.2 7.0 0.3 7.0 0.4 6.6 0.2 7.6 0.3 2Q 7.3 0.4 8.7 0.2 7.6 0.3 7.0 0.4 6.4 0.2 6.6 0.2 6.7 0.2 6.8 0.3 7.1 0.2 6.3 0.2 7.3 0.3 3Q 7.7 0.2 9.0 0.2 7.4 0.5 7.8 0.1 6.9 0.4 7.2 0.1 7.2 0.5 7.5 0.2 7.1 0.3 6.9 0.3 8.2 0.2 4Q 7.7 0.2 8.2 0.3 7.6 0.2 7.5 0.2 6.4 0.2 7.3 0.3 7.2 0.3 (a) 7.2 0.2 6.8 0.2 7.9 0.3 PERIOD 60 61 62 63 64 65 66 73 74 75

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

1Q 6.2 0.3 6.2 0.3 9.0 0.4 8.0 0.3 7.0 0.2 8.3 0.5 7.5 0.4 7.1 0.2 7.7 0.3 6.9 0.2 2Q 6.2 0.2 6.2 0.2 9.1 0.4 7.6 0.4 6.9 0.2 7.4 0.2 7.1 0.5 6.6 0.2 7.1 0.2 6.5 0.3 3Q 6.7 0.1 6.4 0.2 9.5 0.4 8.4 0.2 7.1 0.1 8.4 0.3 7.3 0.4 7.2 0.4 7.7 0.2 6.7 0.2 4Q 6.5 0.4 6.7 0.2 9.5 0.4 8.6 0.3 7.4 0.2 8.1 0.2 7.6 0.4 6.9 0.2 7.9 0.3 6.8 0.2

• READINGS ARE THE AVERAGE OF MULTI CaSoiTm) PHOSPHOR ELEMENTS WITHIN ONE PANASONIC TLD BADGE ERRORS ARE TWO SIGMA AND INCLUDE COUNTING, TRANSIT, READER AND FADE UNCERTAINTIES C= Control location, Background location (a) Lost TLD 3-8

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 2 AIR PARTICULATES GROSS BETA RADIOACTIVITY 3

(pCi/m )

LOCATIONS PERIOD ENDING 1 2 3 4 10 11 27 15C

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

01/19/21 0.016 0.002 0.016 0.002 0.017 0.002 0.016 0.002 0.017 0.002 0.015 0.002 0.015 0.002 0.015 0.002 02/03/21 0.007 0.002 0.008 0.002 0.008 0.002 0.007 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 02/15/21 0.013 0.002 0.012 0.002 0.013 0.002 0.014 0.002 0.014 0.002 0.013 0.002 0.013 0.002 0.014 0.002 03/02/21 0.016 0.002 0.015 0.002 0.014 0.002 0.015 0.002 0.014 0.002 0.015 0.002 0.014 0.002 0.014 0.002 03/16/21 0.011 0.002 0.016 0.002 0.013 0.002 0.014 0.002 0.015 0.002 0.015 0.002 0.015 0.002 0.014 0.002 03/30/21 0.014 0.002 0.015 0.002 0.014 0.002 0.016 0.002 0.016 0.002 0.016 0.002 0.015 0.002 0.016 0.002 04/13/21 0.010 0.002 0.011 0.002 0.010 0.002 0.011 0.002 0.010 0.002 0.009 0.002 0.010 0.002 0.010 0.002 04/27/21 0.014 0.002 0.013 0.002 0.011 0.002 0.012 0.002 0.012 0.002 0.015 0.002 0.013 0.002 0.013 0.002 05/11/21 0.011 0.002 0.011 0.002 0.011 0.002 0.012 0.002 0.012 0.002 0.011 0.002 0.011 0.002 0.012 0.002 05/25/21 0.014 0.002 0.014 0.002 0.014 0.002 0.016 0.002 0.015 0.002 0.015 0.002 0.015 0.002 0.015 0.002 06/08/21 0.010 0.002 0.008 0.002 0.008 0.001 0.009 0.002 0.008 0.002 0.008 0.002 0.008 0.002 0.010 0.002 06/22/21 0.013 0.002 0.012 0.002 0.011 0.002 0.013 0.002 0.013 0.002 0.010 0.002 0.012 0.002 0.011 0.002 07/06/21 0.010 0.002 0.007 0.002 0.009 0.002 0.009 0.002 0.008 0.002 0.008 0.002 0.007 0.002 0.010 0.002 07/20/21 0.015 0.002 0.013 0.002 0.016 0.002 0.014 0.002 0.013 0.002 0.012 0.002 0.014 0.002 0.014 0.002 08/03/21 0.014 0.002 0.013 0.002 0.014 0.002 0.012 0.002 0.015 0.002 0.015 0.002 0.013 0.002 0.016 0.002 08/17/21 0.016 0.002 0.017 0.002 0.015 0.002 0.014 0.002 0.015 0.002 0.016 0.002 0.018 0.002 0.016 0.002 08/31/21 0.015 0.002 0.015 0.002 0.016 0.002 0.014 0.002 0.014 0.002 0.015 0.002 0.015 0.002 0.015 0.002 09/14/21 0.012 0.002 0.014 0.002 0.015 0.002 0.013 0.002 0.016 0.002 0.015 0.002 0.014 0.002 0.014 0.002 09/28/21 0.018 0.002 0.017 0.002 0.014 0.002 0.016 0.002 0.018 0.002 0.016 0.002 0.021 0.002 0.018 0.002 10/12/21 0.011 0.002 0.011 0.002 0.010 0.002 0.011 0.002 0.011 0.002 0.013 0.002 0.012 0.002 0.010 0.002 10/25/21 0.020 0.002 0.021 0.003 0.019 0.002 0.019 0.002 0.020 0.003 0.020 0.002 0.018 0.002 0.020 0.002 11/09/21 0.014 0.002 0.013 0.002 0.013 0.002 0.012 0.002 0.012 0.002 0.012 0.002 0.014 0.002 0.015 0.002 11/23/21 0.016 0.002 0.017 0.002 0.018 0.002 0.019 0.002 0.015 0.002 0.018 0.002 0.017 0.002 0.019 0.002 12/07/21 0.014 0.002 0.017 0.002 0.016 0.002 0.015 0.002 0.013 0.002 0.015 0.002 0.014 0.002 0.014 0.002 12/21/21 0.019 0.002 0.019 0.002 0.015 0.002 0.017 0.002 0.016 0.002 0.015 0.002 0.016 0.002 0.016 0.002 01/04/22 0.020 0.002 0.019 0.002 0.019 0.002 0.019 0.002 0.018 0.002 0.020 0.002 0.021 0.002 0.017 0.002 C= Control location, Background location 3-9

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 3 AIRBORNE IODINE 3

(pCi/m }

LOCATIONS PERIOD ENDING 1 2 3 4 10 11 27 15C

(+/-) (+/-) {+/-) (+/-) {+/-) {+/-) {+/-) {+/-)

01/19/21 -0.007 0.009 -0.008 0.010 -0.008 0.010 -0.008 0.010 -0.007 0.013 -0.007 0.012 -0.007 0.012 -0.006 0.011 02/03/21 -0.020 0.020 -0.021 0.022 -0.022 0.023 -0.018 0.019 0.002 0.013 0.002 0.013 0.002 0.011 0.001 0.007 02/15/21 0.001 0.018 0.001 0.019 0.002 0.021 0.001 0.019 0.004 0.012 0.004 0.011 0.004 0.011 0.004 0.011 03/02/21 0.000 0.024 0.000 0.024 0.000 0.028 0.000 0.023 -0.009 0.015 -0.010 0.015 -0.009 0.014 -0.009 0.014 03/16/21 0.000 0.017 0.000 0.018 0.000 0.017 0.000 0.017 0.003 0.012 0.003 0.012 0.002 0.010 0.003 0.011 03/30/21 -0.004 0.017 -0.004 0.018 -0.004 0.016 -0.004 0.018 -0.004 0.022 -0.004 0.023 -0.003 0.020 -0.003 0.021 04/13/21 0.001 0.010 0.001 0.010 0.001 0.004 0.002 0.011 -0.006 0.010 -0.006 0.010 -0.006 0.011 -0.007 0.012 04/27/21 0.008 0.021 0.008 0.022 0.007 0.019 0.009 0.024 -0.001 0.013 -0.001 0.016 -0.001 0.017 -0.001 0.018 05/11/21 -0.016 0.018 -0.015 0.017 -0.017 0.019 -0.013 0.015 0.012 0.014 0.012 0.014 0.013 0.015 0.012 0.015 05/25/21 0.002 0.014 0.002 0.013 0.002 0.016 0.002 0.013 -0.004 0.019 -0.004 0.019 -0.003 0.018 -0.004 0.019 06/08/21 0.016 0.010 0.017 0.011 0.013 0.008 0.017 0.010 0.019 0.011 0.008 0.015 0.008 0.015 0.008 0.015 06/22/21 0.007 0.010 0.007 0.010 0.006 0.008 0.007 0.009 0.010 0.013 0.009 0.012 0.010 0.013 0.010 0.013 07/06/21 -0.001 0.011 -0.001 0.010 -0.001 0.009 -0.001 0.011 0.005 0.014 0.006 0.015 0.006 0.014 0.006 0.015 07/20/21 0.005 0.011 0.004 0.010 0.004 0.010 0.005 0.011 0.002 0.008 0.003 0.009 0.003 0.009 0.003 0.009 08/03/21 -0.010 0.013 -0.008 0.011 -0.009 0.012 -0.010 0.014 -0.004 0.012 -0.004 0.012 -0.004 0.012 -0.004 0.013 08/17/21 0.006 0.013 0.006 0.014 0.005 0.012 0.006 0.014 -0.001 0.011 -0.001 0.011 -0.001 0.011 -0.001 0.012 08/31/21 0.005 0.015 0.006 0.017 0.005 0.014 0.006 0.016 0.006 0.016 0.006 0.016 0.006 0.016 0.006 0.018 09/14/21 0.004 0.006 0.006 0.011 0.006 0.010 0.006 0.010 0.000 0.010 0.000 0.010 0.000 0.010 0.000 0.011 09/28/21 -0.009 0.015 -0.011 0.019 -0.010 0.017 -0.010 0.017 -0.001 0.011 -0.001 0.011 -0.001 0.011 -0.001 0.012 10/12/21 -0.002 0.013 -0.001 0.008 -0.002 0.014 -0.002 0.015 -0.002 0.015 -0.005 0.010 -0.005 0.011 -0.006 0.011 10/25/21 -0.009 0.010 -0.012 0.013 -0.010 0.010 -0.010 0.011 0.006 0.012 0.006 0.011 0.006 0.011 0.006 0.011 11/09/21 0.007 0.017 0.008 0.020 0.007 0.017 0.007 0.018 0.007 0.015 0.007 0.015 0.007 0.014 0.008 0.015 11/23/21 0.000 0.024 0.000 0.026 0.000 0.023 0.000 0.025 0.021 0.014 0.022 0.015 0.016 0.011 0.021 0.014 12/07/21 0.003 0.010 0.003 0.010 0.003 0.009 0.003 0.010 0.001 0.010 0.001 0.009 0.001 0.008 0.001 0.009 12/21/21 -0.001 0.009 -0.001 0.011 -0.001 0.009 -0.001 0.010 -0.003 0.012 -0.003 0.011 -0.003 0.010 -0.003 0.012 01/04/22 -0.001 0.012 -0.001 0.013 -0.001 0.012 -0.001 0.012 0.006 0.015 0.006 0.014 0.006 0.015 0.006 0.015 C= Control location, Background location 3-10

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 4 AIR PARTICULATES 3

(pCi/m )

GAMMA SPECTRA - QTR 1 (1/5/21 - 03/30/21)

LOCATION Sr-89 Sr-90 Be-7 Mn-54 Co-58 Co-60 Zn-65

-- (+/-) --(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

0.0005 0.0088 -0.0001 0.0024 0.1048 0.0331 -0.0001 0.0015 0.0020 0.0024 0.0007 0.0018 0.0014 0.0034 2 0.0036 0.0145 0.0014 0.0034 0.0910 0.0253 0.0017 0.0014 -0.0010 0.0019 0.0000 0.0010 -0.0016 0.0028 3 0.0015 0.0144 0.0025 0.0034 0.1192 0.0258 0.0007 0.0011 -0.0011 0.0013 0.0000 0.0011 -0.0022 0.0030 4 -0.0053 0.0106 0.0011 0.0031 0.1089 0.0272 -0.0006 0.0011 0.0002 0.0016 0.0000 0.0010 0.0017 0.0029 10 0.0064 0.0127 -0.0019 0.0023 0.0967 0.0285 -0.0005 0.0013 0.0006 0.0018 0.0000 0.0009 -0.0008 0.0029 11 -0.0022 0.0158 -0.0001 0.0026 0.1075 0.0281 0.0008 0.0013 0.0000 0.0015 0.0002 0.0007 -0.0010 0.0031 27 -0.0016 0.0121 0.0017 0.0029 0.1462 0.0328 -0.0001 0.0017 -0.0009 0.0022 0.0002 0.0015 0.0006 0.0040 15C -0.0054 0.0107 -0.0013 0.0019 0.1164 0.0247 0.0000 0.0014 0.0012 0.0018 -0.0015 0.0015 0.0043 0.0034 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

-- (+/-) ---r.+i-) (+/-) (+/-) (+/-) (+/-) (+/-)

-0.0013 0.0021 -0.0004 0.0036 0.0010 0.0033 0.0044 0.0128 -0.0005 0.0017 -0.0002 0.0015 -0.0339 0.0729 2 0.0024 0.0018 -0.0009 0.0033 0.0013 0.0023 0.0002 0.0100 -0.0003 0.0013 0.0004 0.0011 -0.0122 0.0486 3 0.0009 0.0017 -0.0016 0.0027 -0.0002 0.0022 0.0021 0.0093 0.0000 0.0013 0.0004 0.0009 -0.0326 0.0485 4 0.0004 0.0016 0.0009 0.0032 -0.0003 0.0020 -0.0047 0.0078 0.0005 0.0013 -0.0006 0.0009 0.0111 0.0531 10 0.0005 0.0017 -0.0003 0.0030 0.0002 0.0021 0.0044 0.0111 -0.0021 0.0013 0.0007 0.0012 0.0343 0.0556 11 -0.0014 0.0016 0.0003 0.0024 0.0004 0.0021 0.0059 0.0082 0.0006 0.0012 0.0002 0.0009 -0.0476 0.0534 27 -0.0003 0.0024 -0.0007 0.0042 0.0019 0.0027 -0.0123 0.0158 0.0010 0.0016 0.0007 0.0014 -0.1019 0.0818 15C -0.0005 0.0021 0.0015 0.0036 0.0012 0.0027 -0.0038 0.0115 -0.0003 0.0014 0.0003 0.0012 0.0102 0.0661 LOCATION Ce-141 Ce-144

(+/-) (+/-)

0.0002 0.0039 -0.0019 0.0060 2 -0.0004 0.0030 0.0022 0.0047 3 -0.0016 0.0030 0.0043 0.0053 4 0.0013 0.0031 -0.0044 0.0046 10 0.0014 0.0028 0.0002 0.0043 11 -0.0001 0.0025 -0.0043 0.0040 27 -0.0014 0.0046 -0.0046 0.0070 15C 0.0003 0.0037 -0.0019 0.0063 C= Control location, Background location Results in bold type are posith,e.

3-11

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 4 AIR PARTICULATES (pCi/m 3 )

GAMMA SPECTRA - QTR 2 (03/30/21 - 07/06/21)

LOCATION Sr-89 Sr-90 Be-7 Mn-54 Co-58 Co-60 Zn-65

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

1 0.0209 0.0151 0.0006 0.0020 0.0908 0.0408 0.0000 0.0012 -0.0006 0.0016 0.0006 0.0011 -0.0025 0.0018 2 0.0049 0.0119 0.0003 0.0024 0.1091 0.0232 -0.0001 0.0007 0.0002 0.0009 -0.0004 0.0008 -0.0014 0.0018 3 0.0019 0.0094 -0.0009 0.0018 0.1127 0.0255 -0.0005 0.0005 -0.0003 0.0011 0.0001 0.0008 -0.0020 0.0020 4 0.0076 0.0106 0.0011 0.0024 0.1103 0.0343 0.0003 0.0014 -0.0012 0.0021 0.0003 0.0016 -0.0014 0.0032 10 0.0053 0.0117 0.0009 0.0023 0.1020 0.0306 0.0003 0.0010 0.0006 0.0012 -0.0003 0.0007 -0.0012 0.0020 11 -0.0077 0.0084 -0.0005 0.0017 0.1052 0.0280 0.0004 0.0007 0.0000 0.0008 0.0002 0.0007 0.0008 0.0015 27 0.0027 0.0122 0.0009 0.0021 0.1040 0.0199 -0.0001 0.0007 -0.0007 0.0010 -0.0002 0.0006 0.0004 0.0016 15C -0.0004 0.0124 -0.0001 0.0023 0.1025 0.0277 0.0006 0.0009 0.0002 0.0009 0.0001 0.0008 -0.0006 0.0018 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

1 -0.0012 0.0018 -0.0014 0.0027 -0.0002 0.0021 -0.0030 0.0083 0.0000 0.0010 -0.0005 0.0009 0.0232 0.0639 2 -0.0005 0.0011 -0.0003 0.0016 -0.0007 0.0014 -0.0021 0.0043 0.0000 0.0007 0.0001 0.0005 0.0087 0.0384 3 -0.0004 0.0009 -0.0010 0.0017 0.0000 0.0014 -0.0003 0.0055 0.0000 0.0007 -0.0003 0.0005 -0.0044 0.0487 4 0.0018 0.0020 -0.0032 0.0040 -0.0009 0.0026 0.0150 0.0120 0.0005 0.0017 -0.0007 0.0013 -0.0704 0.0805 10 0.0007 0.0015 0.0002 0.0025 0.0007 0.0018 0.0040 0.0072 0.0002 0.0009 -0.0005 0.0007 0.0058 0.0546 11 0.0002 0.0011 0.0002 0.0016 -0.0001 0.0013 0.0009 0.0067 0.0011 0.0008 0.0002 0.0006 -0.0003 0.0370 27 0.0001 0.0010 -0.0022 0.0021 0.0005 0.0015 -0.0060 0.0071 -0.0004 0.0009 0.0005 0.0006 -0.0191 0.0482 15C 0.0008 0.0010 -0.0003 0.0022 0.0004 0.0016 0.0055 0.0054 0.0002 0.0007 0.0002 0.0006 0.0027 0.0423 LOCATION Ce-141 Ce-144

(+/-) (+/-)

0.0000 0.0027 -0.0008 0.0042 2 -0.0005 0.0022 0.0001 0.0027 3 0.0012 0.0021 0.0006 0.0029 4 -0.0031 0.0041 0.0007 0.0062 10 -0.0003 0.0029 -0.0011 0.0048 11 -0.0008 0.0024 -0.0030 0.0028 27 -0.0014 0.0021 -0.0022 0.0031 15C 0.0013 0.0016 0.0010 0.0031 C= Control location, Background location Results in bold type are positi1.e.

3-12

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 4 AIR PARTICULATES 3

(pCi/m )

GAMMA SPECTRA - QTR 3 (07/06/21 - 09/28/21)

LOCATION Sr-89 Sr-90 Be-7 Mn-54 Co-58 Co-60 Zn-65

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

0.0195 0.0156 0.0006 0.0025 0.1099 0.0245 -0.0003 0.0010 0.0000 0.0014 -0.0007 0.0010 0.0009 0.0026 2 -0.0100 0.0073 -0.0007 0.0022 0.0971 0.0251 -0.0004 0.0014 -0.0011 0.0021 0.0005 0.0017 -0.0019 0.0031 3 0.0077 0.0108 -0.0002 0.0022 0.1390 0.0405 0.0004 0.0015 -0.0009 0.0021 0.0005 0.0015 -0.0002 0.0035 4 -0.0020 0.0118 0.0019 0.0028 0.1000 0.0251 0.0003 0.0009 0.0001 0.0017 -0.0002 0.0010 -0.0004 0.0030 10 -0.0020 0.0144 -0.0001 0.0025 0.1097 0.0274 -0.0001 0.0014 -0.0005 0.0021 -0.0006 0.0015 0.0011 0.0031 11 -0.0001 0.0089 -0.0001 0.0017 0.0993 0.0282 0.0004 0.0015 -0.0005 0.0015 -0.0002 0.0014 0.0020 0.0032 27 -0.0041 0.0094 0.0000 0.0020 0.1225 0.0364 0.0005 0.0015 0.0011 0.0024 0.0001 0.0019 0.0005 0.0040 15C 0.0068 0.0112 0.0009 0.0024 0.1087 0.0380 -0.0005 0.0020 -0.0003 0.0025 -0.0006 0.0020 -0.0006 0.0030 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

-- (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

-0.0005 0.0017 -0.0007 0.0026 0.0011 0.0023 0.0007 0.0092 0.0002 0.0012 0.0002 0.0008 0.0221 0.0543 2 -0.0005 0.0017 0.0020 0.0035 -0.0008 0.0028 0.0017 0.0111 0.0004 0.0014 0.0001 0.0013 -0.0449 0.0717 3 0.0014 0.0024 0.0015 0.0043 0.0036 0.0030 0.0081 0.0103 -0.0004 0.0017 0.0002 0.0015 0.0264 0.0905 4 0.0003 0.0017 0.0014 0.0029 0.0004 0.0021 0.0035 0.0090 -0.0005 0.0012 -0.0002 0.0009 -0.0285 0.0563 10 0.0005 0.0017 -0.0036 0.0034 0.0020 0.0027 -0.0101 0.0126 -0.0003 0.0014 -0.0008 0.0011 0.0235 0.0765 11 0.0019 0.0019 -0.0012 0.0034 0.0017 0.0026 0.0041 0.0100 0.0005 0.0014 0.0003 0.0010 -0.0055 0.0669 27 0.0013 0.0022 0.0001 0.0034 -0.0015 0.0031 0.0107 0.0136 -0.0007 0.0015 0.0005 0.0015 0.0452 0.0776 15C -0.0024 0.0028 0.0004 0.0051 -0.0010 0.0033 -0.0085 0.0148 0.0012 0.0019 -0.0012 0.0017 0.0104 0.0977 LOCATION Ce-141 Ce-144

(+/-) (+/-)

-0.0028 0.0025 0.0024 0.0038 2 -0.0029 0.0040 0.0027 0.0063 3 -0.0014 0.0049 -0.0009 0.0074 4 0.0008 0.0024 -0.0028 0.0037 10 -0.0024 0.0037 -0.0014 0.0056 11 0.0002 0.0034 -0.0037 0.0057 27 -0.0011 0.0034 -0.0011 0.0055 15C 0.0024 0.0043 -0.0006 0.0068 C= Control location, Background location Results in bold type are positi.e.

3-13

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 4 AIR PARTICULATES 3

(pCi/m )

GAMMA SPECTRA - QTR 4 (09/28/21 - 01/04/22)

LOCATION Sr-89 Sr-90 Be-7 Mn-54 Co-58 Co-60 Zn-65

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

0.0094 0.0114 0.0018 0.0027 0.1087 0.0227 -0.0001 0.0007 0.0010 0.0013 0.0001 0.0008 0.0012 0.0022 2 0.0020 0.0100 0.0019 0.0031 0.0852 0.0253 -0.0006 0.0010 0.0010 0.0017 0.0018 0.0012 0.0016 0.0022 3 0.0105 0.0091 0.0007 0.0021 0.1040 0.0244 0.0005 0.0011 -0.0004 0.0015 -0.0001 0.0012 0.0030 0.0028 4 -0.0004 0.0089 0.0039 0.0031 0.0974 0.0189 -0.0001 0.0007 0.0010 0.0011 -0.0001 0.0007 0.0003 0.0018 10 0.0008 0.0113 0.0012 0.0025 0.0945 0.0215 0.0000 0.0009 0.0003 0.0012 -0.0007 0.0011 0.0008 0.0027 11 0.0071 0.0092 0.0016 0.0025 0.1098 0.0280 -0.0001 0.0011 0.0005 0.0017 0.0001 0.0012 0.0011 0.0024 27 0.0017 0.0095 0.0013 0.0023 0.1151 0.0253 -0.0001 0.0009 -0.0002 0.0014 -0.0001 0.0010 0.0001 0.0024 15C 0.0018 0.0086 0.0029 0.0028 0.0931 0.0263 -0.0009 0.0014 0.0028 0.0023 -0.0004 0.0011 0.0007 0.0034 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

-0.0001 0.0012 -0.0001 0.0018 0.0022 0.0017 0.0023 0.0068 -0.0002 0.0009 -0.0003 0.0008 0.0196 0.0444 2 0.0003 0.0015 0.0028 0.0024 0.0022 0.0021 -0.0001 0.0082 0.0001 0.0010 -0.0001 0.0010 0.0162 0.0679 3 0.0009 0.0017 0.0027 0.0028 -0.0024 0.0023 -0.0088 0.0099 -0.0003 0.0011 -0.0001 0.0010 0.0024 0.0600 4 -0.0004 0.0010 -0.0006 0.0021 0.0008 0.0014 -0.0034 0.0064 -0.0005 0.0007 0.0007 0.0008 0.0162 0.0463 10 0.0003 0.0015 0.0002 0.0025 -0.0006 0.0020 0.0061 0.0092 0.0000 0.0011 -0.0004 0.0009 -0.0301 0.0556 11 0.0000 0.0016 0.0008 0.0029 -0.0011 0.0023 -0.0026 0.0104 -0.0008 0.0011 -0.0001 0.0010 0.0388 0.0609 27 0.0003 0.0016 0.0015 0.0024 -0.0001 0.0015 0.0026 0.0084 -0.0002 0.0009 0.0007 0.0009 0.0134 0.0487 15C 0.0008 0.0022 0.0008 0.0034 -0.0027 0.0028 -0.0028 0.0114 -0.0009 0.0014 0.0004 0.0011 0.0204 0.0767 LOCATION Ce-141 Ce-144

(+/-) (+/-)

1 0.0006 0.0027 0.0013 0.0036 2 -0.0010 0.0026 0.0005 0.0040 3 -0.0009 0.0029 -0.0016 0.0046 4 0.0010 0.0020 0.0005 0.0027 10 -0.0007 0.0026 0.0002 0.0034 11 -0.0051 0.0030 0.0008 0.0047 27 -0.0021 0.0023 0.0000 0.0037 15C -0.0011 0.0037 -0.0044 0.0052 C= Control location, Background location Results in bold type are positi1.e.

3-14

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 5 SOIL (pCi/g dry wt.)

LOCATIONS COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

3 05/04/21 0.137 0.413 13.710 1.903 -0.215 0.369 0.020 0.053 -0.004 0.048 -0.117 0.088 4 05/04/21 0.518 0.545 14.340 2.044 -0.032 0.430 -0.060 0.067 -0.047 0.058 0.129 0.125 14C 05/04/21 0.270 0.447 17.350 2.033 0.100 0.456 -0.011 0.060 0.005 0.050 -0.027 0.125 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

3 05/04/21 -0.012 0.067 -0.024 0.127 0.060 0.057 0.072 0.089 -0.039 0.050 0.018 0.440 4 05/04/21 0.014 0.074 -0.315 0.160 0.040 0.064 0.048 0.101 -0.017 0.057 0.278 0.537 14C 05/04/21 -0.001 0.053 0.019 0.136 0.030 0.060 0.020 0.098 -0.011 0.052 0.287 0.484 COLLECTION LOCATION DATE Sb-125 Cs-134 Cs-137 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

3 05/04/21 0.096 0.134 0.027 0.054 0.102 0.092 0.028 0.061 0.006 0.244 0.605 0.289 4 05/04/21 -0.066 0.142 0.058 0.066 0.115 0.077 0.024 0.070 0.483 0.277 1.481 0.318 14C 05/04/21 -0.053 0.142 0.036 0.064 0.112 0.070 0.026 0.078 -0.112 0.311 1.291 0.544 C= Control location, Background location Results in bold type are posti1.e.

3-15

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 6 MILK (pCi/1)

COLLECTION LOCATION DATE 1-131 Sr-89 Sr-90 K-40 Cs-134 Cs-137 Ba-140 La-140

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

22 Cow Milk was not availible for collection in 2021.

Strontium analysis of air samples was performed as a substitite (Table 4) 23 Goat 3-16

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 7 WELL WATER (pCi/1)

COLLECTION LOCATION DATE H-3 Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

71 03/05/21 241 436 -25.6 35.4 9.93 50.5 11.0 36.4 -1.77 3.56 0.83 4.55 0.41 7.65 1.96 3.67 05/25/21 5 422 -15.3 40.3 -34.2 53.8 3.38 37.4 -2.51 4.57 -1.88 4.66 0.61 8.02 3.48 3.80 08/30/21 247 580 -17.9 24.8 17.0 38.7 8.18 31.7 -1.68 2.91 -3.28 3.23 -2.06 5.30 -0.91 3.56 11/23/21 213 430 -17.3 25.2 46.8 44.9 -8.79 26.9 1.16 2.56 -2.04 2.55 1.53 5.50 2.51 2.47 72 03/05/21 257 437 1.23 22.1 13.5 33.3 4.84 22.2 -0.23 2.68 -0.17 2.74 -1.71 5.62 -0.60 2.55 05/25/21 -128 415 1.00 22.0 22.3 35.5 16.3 24.3 1.37 2.71 -0.60 2.67 1.27 5.10 -0.11 3.22 08/30/21 228 578 27.9 29.7 -9.48 48.1 -1.92 35.3 2.76 3.10 1.04 3.81 -0.68 6.32 0.53 3.24 11/23/21 9 413 28.4 35.8 -30.4 62.6 31.9 38.8 -3.28 4.86 0.44 3.63 0.30 8.23 -0.30 4.65 76 03/23/21 -253 569 -19.5 41.2 12.6 69.5 5.27 37.6 -3.34 3.72 1.43 5.16 4.49 9.95 0.99 4.22 05/18/21 -25 434 -8.16 36.2 54.6 69.6 3.08 39.7 -1.71 4.45 -4.12 4.48 -0.98 9.28 -1.59 4.34 08/10/21 459 477 9.84 41.3 -26.9 85.1 0.98 45.0 0.16 5.15 -2.07 5.41 3.90 8.51 -5.35 6.60 10/19/21 56 446 0.18 28.7 4.45 56.3 -43.0 31.5 -1.25 3.20 -2.56 3.18 2.77 6.15 -0.05 3.16 77 03/23/21 114 597 -4.39 43.0 -33.7 82.0 26.5 46.2 -0.77 5.18 -3.68 5.70 4.05 12.0 -0.81 5.61 05/18/21 148 447 -31.1 51.6 30.6 84.0 17.0 54.6 -4.88 6.49 -3.62 6.26 -7.42 10.6 -1.11 6.28 08/10/21 10 446 -8.98 48.5 -30.6 71.4 -20.5 54.6 -7.69 5.39 -2.24 5.84 -1.32 10.1 -3.39 5.51 10/19/21 76 594 5.09 30.6 67.7 55.5 -11.3 35.4 -1.37 3.77 -4.74 3.93 -2.63 7.03 -0.94 3.76 78 03/23/21 25 436 -12.0 29.8 24.2 60.1 -3.83 33.3 0.05 3.52 -1.28 3.67 0.63 8.48 -0.31 3.56 05/18/21 437 473 -2.42 30.7 -57.4 54.4 -14.4 31.8 -1.08 3.74 -0.39 3.67 -1.26 9.33 2.78 4.98 08/10/21 -230 431 -32.8 41.5 13.8 77.1 8.18 44.3 0.92 4.80 0.79 4.64 0.88 8.62 -0.22 4.95 10/19/21 85 427 19.8 31.8 62.9 64.6 -3.53 31.4 -2.67 3.17 -0.92 3.54 5.45 6.38 0.85 3.38 79 02/25/21 181 436 -6.20 23.0 -9.55 42.6 2.91 27.7 -0.19 2.79 -1.84 2.74 3.29 5.74 2.53 2.80 05/25/21 583 604 -18.3 33.2 28.9 54.9 22.4 32.4 -1.32 3.99 -4.92 3.86 0.54 6.20 -1.58 3.38 08/30/21 77 409 -11.7 36.4 7.39 67.0 -13.2 35.1 -1.44 3.90 1.95 4.08 -2.32 7.66 0.65 3.83 11/23/21 645 460 -0.12 19.7 6.00 40.0 -9.66 23.6 0.23 2.70 0.44 2.56 -4.61 6.22 -0.49 2.77 81 02/25/21 432 464 -11.1 27.2 6.04 70.6 -1.76 30.8 1.14 3.26 1.23 2.84 -0.18 7.79 0.28 3.22 05/25/21 805 619 -0.68 41.5 -71.0 68.2 21.4 39.6 -0.64 5.38 -2.38 4.58 1.77 8.69 3.74 4.79 08/30/21 213 430 -15.4 37.4 -6.11 72.3 -3.20 40.7 -2.98 5.86 -1.10 5.16 -11.2 10.2 -4.24 5.23 11/23/21 289 426 -3.21 23.7 70.8 78.1 -4.76 25.3 -0.95 3.07 -1.87 3.15 3.79 5.91 0.81 2.76 82 01/20/21 289 426 7.33 51.2 -17.4 66.2 -49.1 52.7 -2.76 5.43 -0.43 5.99 0.35 9.77 -3.64 5.53 05/19/21 65 435 -22.0 32.6 -0.05 43.4 0.86 36.8 0.36 3.14 -0.95 3.99 -1.49 7.31 1.05 3.68 09/30/21 299 455 -22.5 31.3 20.4 41.7 2.80 36.0 -4.98 3.54 0.08 3.92 2.98 6.80 0.58 3.48 11/19/21 278 442 -26.9 19.6 -5.05 25.4 -12.0 23.5 -3.26 2.34 -0.70 2.16 -1.12 4.44 1.91 2.23 83 02/25/21 527 455 2.36 31.4 -8.20 48.1 -5.59 42.0 -0.93 3.21 0.06 3.72 4.13 7.34 -1.88 3.61 05/18/21 -337 405 -38.4 33.2 -43.5 64.7 -26.8 35.8 -0.53 4.61 1.31 4.48 2.14 9.25 3.50 4.71 08/30/21 89 568 -25.2 42.8 29.6 63.8 8.33 40.4 -0.15 4.37 -4.69 5.11 4.55 9.25 0.62 4.72 11/19/21 69 415 -14.5 31.5 47.6 49.0 -45.3 40.1 -2.18 4.14 -0.83 3.74 -3.24 7.19 -0.38 3.51 3-17

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 7 WELL WATER (pCi/1)

COLLECTION LOCATION DATE Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131 Cs-134

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

71 03/05/21 -1.36 8.22 6.20 4.73 -2.74 5.99 -0.08 4.07 -4.28 33.7 1.72 11.6 4.73 5.74 0.66 4.07 05/25/21 3.84 9.33 3.53 5.01 -0.50 6.68 -4.37 4.24 -48.6 39.3 3.54 12.6 -3.29 6.31 -1.09 4.16 08/30/21 -4.40 8.25 -0.35 3.57 -7.11 5.54 -1.82 3.56 -7.27 26.8 0.45 9.20 -1.16 4.29 -1.20 2.75 11/23/21 17.5 6.72 3.74 3.04 -0.99 4.67 -0.38 2.87 -12.5 23.0 -2.26 7.82 0.63 4.54 2.16 2.81 72 03/05/21 -8.66 6.45 -0.78 2.90 0.83 4.37 -1.40 2.85 1.71 23.4 -1.31 6.97 -1.44 4.41 -0.88 2.25 05/25/21 1.10 6.23 -0.57 3.52 -1.91 4.54 -0.06 2.91 2.16 17.7 -0.52 8.81 0.57 3.35 -0.90 3.06 08/30/21 -0.85 9.52 4.67 4.00 5.40 6.67 0.06 3.87 17.5 34.4 7.45 10.9 -1.78 4.93 -2.27 4.17 11/23/21 -16.5 13.4 5.93 4.83 -1.68 7.09 -3.49 4.50 37.2 43.2 -6.08 10.8 -4.15 5.82 0.70 3.98 76 03/23/21 -18.0 13.1 0.26 4.52 3.14 7.74 -1.08 4.49 -1.92 40.6 3.32 13.1 2.18 7.50 -1.23 5.06 05/18/21 0.91 10.8 4.67 4.77 3.64 6.88 3.58 4.31 -19.7 36.9 6.86 13.9 0.58 5.04 -2.70 5.48 08/10/21 -0.83 11.1 2.64 4.87 -2.42 8.55 0.55 5.03 12.9 40.0 -13.4 14.9 -4.19 5.87 -1.95 5.42 10/19/21 2.36 7.85 2.78 3.95 -5.84 5.48 -0.89 3.57 4.56 30.2 2.25 10.1 -0.86 3.91 0.84 3.91 77 03/23/21 -2.12 10.5 0.56 6.04 -0.44 8.83 -1.40 5.45 16.3 43.7 -2.57 14.2 1.32 7.43 2.57 5.58 05/18/21 -2.37 16.2 8.30 6.88 5.66 10.7 2.30 5.92 27.2 53.4 6.36 17.7 1.75 6.25 -2.06 6.57 08/10/21 25.5 12.8 24.1 7.40 -0.15 8.94 -1.05 5.75 1.65 47.8 11.6 19.1 2.70 6.76 -0.82 6.13 10/19/21 16.8 8.87 10.8 4.52 -0.09 6.19 -2.24 4.06 13.1 32.2 -3.94 11.6 1.02 4.50 -3.25 4.10 78 03/23/21 -7.46 10.1 7.66 4.63 1.82 6.80 -0.36 4.35 -5.92 34.5 -0.35 10.8 6.75 6.02 2.59 4.00 05/18/21 -0.13 12.0 -4.73 4.56 2.29 6.65 -0.08 4.22 10.7 34.2 -6.48 12.3 -0.18 4.03 -0.78 3.71 08/10/21 5.88 9.44 7.49 5.38 10.3 8.17 2.27 5.06 7.93 53.2 -6.63 15.5 -1.83 6.07 2.74 5.06 10/19/21 1.23 7.90 0.94 3.79 0.55 6.48 2.04 3.73 6.33 35.3 1.07 10.4 -1.06 4.37 2.90 4.24 79 02/25/21 -14.5 8.68 -2.55 3.33 -4.25 4.77 -0.91 3.08 -18.5 30.1 -1.98 7.43 -2.80 6.56 2.34 2.65 05/25/21 -7.89 9.05 4.37 4.06 -1.89 6.13 -2.54 4.38 39.0 35.3 7.23 11.0 -0.31 4.72 -2.02 4.64 08/30/21 -17.8 10.7 2.11 3.91 -2.49 6.16 2.17 4.50 16.7 43.8 -6.03 11.5 -1.12 5.49 -2.24 3.92 11/23/21 -12.2 7.02 2.02 2.95 -0.10 4.73 -3.24 2.94 -1.25 23.9 -0.38 7.14 -2.61 4.02 -1.82 3.04 81 02/25/21 7.08 6.55 3.51 3.45 -2.93 5.24 0.02 3.92 -24.6 31.6 -1.52 8.90 -0.81 8.15 -1.87 3.13 05/25/21 0.56 11.7 4.01 5.93 4.38 8.70 -4.05 4.99 -12.6 36.7 -6.69 12.6 -1.11 6.83 3.48 4.32 08/30/21 -3.70 11.1 -5.87 6.46 7.80 7.86 1.94 4.72 -9.92 43.5 9.99 13.7 -5.02 6.29 0.08 5.34 11/23/21 -1.93 7.62 3.15 3.63 2.31 5.30 -0.74 2.86 -12.2 25.7 4.82 8.18 -0.88 4.81 0.72 2.75 82 01/20/21 9.99 12.9 12.9 7.54 5.45 9.76 1.78 5.95 0.08 42.7 -8.51 15.9 2.35 8.00 -2.14 5.65 05/19/21 0.77 7.89 4.82 4.34 -3.56 5.61 -2.71 3.30 6.36 29.9 5.78 10.5 -5.63 7.51 -0.95 3.77 09/30/21 4.38 8.18 12.8 4.80 -0.26 5.85 -1.89 3.64 -8.97 29.5 13.8 11.2 -3.14 6.27 -1.34 3.73 11/19/21 3.23 5.22 3.24 2.73 1.20 3.88 -2.13 2.51 2.59 18.5 -3.05 6.15 -0.56 5.22 -0.11 2.39 83 02/25/21 -26.3 9.93 2.42 4.12 -1.02 5.89 -0.15 3.85 -44.5 33.9 -7.80 10.1 -0.80 8.62 -0.91 3.62 05/18/21 5.16 7.93 3.99 5.82 4.07 6.49 1.15 3.66 -1.44 39.1 3.17 13.9 4.87 5.90 1.09 4.57 08/30/21 1.87 11.3 -0.77 5.10 4.14 7.44 -0.46 4.63 -1.79 39.8 1.90 13.9 -3.89 6.30 -0.35 5.01 11/19/21 -21.1 12.1 2.73 4.28 -0.32 6.78 2.63 4.92 -16.6 36.4 -0.82 11.7 3.56 8.36 0.02 4.58 3-18

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 7 WELL WATER (pCi/1)

COLLECTION LOCATION DATE Cs-137 Ba-140 La-140 Ac-228

(+/-) (+/-) (+/-) (+/-)

71 03/05/21 -0.03 3.79 -12.5 15.2 1.75 5.30 -9.56 14.2 05/25/21 -2.16 4.46 -4.80 17.5 1.06 5.80 -11.6 16.9 08/30/21 -0.40 3.40 -5.54 12.2 0.59 3.70 4.02 10.4 11/23/21 0.66 2.62 -0.68 12.2 0.48 4.34 -3.57 10.3 72 03/05/21 -1.42 3.15 3.17 11.2 0.58 3.36 7.52 9.44 05/25/21 -0.94 2.56 0.38 10.7 -1.66 3.88 12.8 9.26 08/30/21 -2.99 4.49 8.99 17.7 5.42 4.52 -2.98 12.1 11/23/21 1.98 4.20 8.86 20.4 0.74 6.46 4.71 15.4 76 03/23/21 -1.40 5.43 -18.0 23.0 -4.36 6.15 4.69 15.7 05/18/21 -1.18 4.63 -1.78 14.9 3.53 5.62 -2.22 15.6 08/10/21 -0.42 5.33 -2.66 18.2 -6.09 5.74 12.5 18.6 10/19/21 -2.49 4.10 -1.83 13.4 -1.80 3.85 -3.37 12.5 77 03/23/21 -3.49 5.68 -13.2 23.0 1.24 6.53 4.81 18.7 05/18/21 -4.13 7.65 10.8 21.1 3.22 8.04 18.1 23.5 08/10/21 -2.46 5.96 3.16 20.1 3.01 7.40 -0.18 21.8 10/19/21 -1.66 4.00 -0.98 13.4 0.10 4.42 10.6 14.1 78 03/23/21 0.31 4.01 8.81 16.0 1.27 5.07 -12.4 14.1 05/18/21 0.04 3.95 1.82 14.7 3.59 5.22 -3.87 15.6 08/10/21 -2.34 5.42 -9.63 21.1 -3.33 6.16 -25.5 18.9 10/19/21 3.04 4.14 4.37 14.4 1.55 4.15 -3.25 12.3 79 02/25/21 2.10 2.63 9.67 16.6 2.32 5.88 -4.98 11.6 05/25/21 -3.49 4.70 14.4 15.3 -2.18 4.64 2.03 12.9 08/30/21 -2.65 4.49 0.55 20.1 -0.68 4.43 -6.64 16.8 11/23/21 -1.61 3.35 -9.60 13.0 2.25 4.08 -0.40 9.28 81 02/25/21 -0.28 3.29 -9.47 17.6 -0.94 5.32 7.06 11.7 05/25/21 0.90 5.35 -8.95 20.6 2.74 8.02 16.1 19.3 08/30/21 -8.71 5.94 6.55 18.3 1.49 6.96 -8.32 18.8 11/23/21 -4.34 3.33 -8.45 13.2 -2.18 4.80 9.24 11.3 82 01/20/21 -2.84 5.87 -11.6 24.4 0.67 8.04 -5.11 19.9 05/19/21 -6.4 4.13 -0.94 17.6 1.04 6.44 -7.60 12.0 09/30/21 -2.45 3.93 4.03 16.7 1.13 5.40 11.8 13.2 11/19/21 -3.96 2.38 -0.20 12.4 0.58 4.58 -3.33 8.02 83 02/25/21 -1.81 3.91 0.41 22.1 0.69 6.99 -4.85 14.0 05/18/21 -3.13 4.90 12.1 18.3 -1.09 6.53 21.0 18.4 08/30/21 -2.40 4.50 -2.94 16.6 1.40 6.88 -10.2 15.2 11/19/21 -0.72 3.71 -7.34 24.9 1.48 7.26 -8.32 15.4 3-19

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 8 FRUITS & VEGETABLES (pCi/g wet wt.)

LOCATION 25 (fruit are extra samples not required by the REMODCM)

COLLECTION DATE Type Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

07/20/21 Lettuce 0.528 0.203 2.464 0.403 -0.042 0.101 0.010 0.010 -0.002 0.012 -0.004 0.025 0.014 0.013 07/20/21 Apples 0.081 0.108 1.271 0.363 -0.011 0.100 -0.006 0.010 -0.012 0.011 0.004 0.018 0.040 0.020 10/05/21 Tomatoes -0.061 0.132 2.584 0.567 0.031 0.109 -0.001 0.017 0.008 0.014 -0.008 0.037 0.017 0.015 10/05/21 Apples 0.102 0.121 0.837 0.342 0.013 0.120 0.001 0.012 -0.006 0.014 -0.006 0.025 0.002 0.012 COLLECTION DATE T~ Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-J 07/20/21 Lettuce -0.025 0.030 0.002 0.011 -0.005 0.020 -0.008 0.011 0.100 0.116 -0.017 0.036 -0.001 0.013 07/20/21 Apples 0.005 0.024 -0.005 0.010 -0.004 0.020 -0.002 0.011 0.022 0.093 0.009 0.030 -0.005 0.012 10/05/21 Tomatoes 0.005 0.037 -0.002 0.013 0.006 0.025 0.011 0.013 0.046 0.136 -0.009 0.040 0.009 0.016 10/05/21 Apples -0.002 0.030 -0.005 0.016 0.016 0.030 0.011 0.015 0.040 0.147 0.026 0.043 0.001 0.017 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

07/20/21 Lettuce -0.005 0.014 0.004 0.012 -0.048 0.041 -0.006 0.014 -0.010 0.020 0.038 0.091 0.007 0.049 07/20/21 Apples 0.008 0.011 0.002 0.014 -0.011 0.042 0.002 0.011 -0.008 0.017 -0.012 0.067 0.005 0.054 10/05/21 Tomatoes -0.007 0.017 -0.016 0.021 -0.017 0.058 0.009 0.020 -0.002 0.020 0.048 0.086 -0.014 0.049 10/05/21 Apples 0.001 0.017 -0.011 0.017 -0.008 0.055 -0.002 0.017 0.007 0.024 0.052 0.099 0.003 0.051 Results in bold type are positil..

3-20

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 8 FRUITS & VEGETABLES (pCi/g wet wt.)

LOCATION 26C (fruit are extra samples not required by the REMODCM)

COLLECTION DATE T~ Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

07/20/21 Lettuce 0.104 0.163 3.077 0.483 0.118 0.154 0.002 0.018 -0.007 0.020 -0.019 0.040 -0.001 0.022 07/20/21 Plums 0.010 0.085 1.242 0.344 -0.103 0.109 0.002 0.013 0.009 0.012 0.012 0.025 0.011 0.020 10/05/21 Tomatoes -0.007 0.128 1.427 0.429 -0.051 0.105 0.000 0.015 -0.007 0.013 -0.015 0.026 0.002 0.013 10/05/21 Apples 0.025 0.078 0.839 0.250 0.041 0.086 -0.001 0.009 0.006 0.009 -0.006 0.021 0.004 0.008 COLLECTION DATE T~ Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

07/20/21 Lettuce 0.021 0.045 0.011 0.020 0.001 0.033 0.001 0.018 0.024 0.162 -0.005 0.053 -0.002 0.020 07/20/21 Plums -0.028 0.028 0.003 0.013 0.034 0.021 0.003 0.013 0.056 0.118 0.001 0.036 0.008 0.013 10/05/21 Tomatoes -0.021 0.032 -0.010 0.014 -0.001 0.020 0.002 0.014 0.128 0.132 -0.012 0.037 -0.002 0.012 10/05/21 Apples -0.058 0.025 -0.002 0.010 0.003 0.017 0.004 0.011 -0.026 0.088 0.007 0.021 -0.011 0.023 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

07/20/21 Lettuce -0.002 0.024 -0.005 0.020 -0.057 0.074 -0.002 0.020 -0.024 0.030 0.093 0.145 -0.004 0.070 07/20/21 Plums -0.002 0.014 0.017 0.014 0.033 0.041 0.004 0.008 -0.005 0.018 -0.027 0.082 -0.009 0.055 10/05/21 Tomatoes 0.005 0.016 -0.006 0.015 -0.034 0.059 0.005 0.016 -0.001 0.021 0.000 0.090 0.025 0.059 10/05/21 Apples 0.006 0.010 0.000 0.009 0.032 0.057 -0.001 0.013 -0.020 0.016 0.003 0.053 -0.012 0.038 C= Control location, Background location Results in bold type are positi.e.

3-21

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 9 BROADLEAF VEGETATION (pCi/g wet wt.)

LOCATION 1 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.706 0.499 3.494 0.580 0.062 0.139 -0.001 0.017 0.005 0.017 -0.026 0.041 -0.002 0.014 10/07/21 3.848 0.466 3.343 0.660 -0.047 0.160 0.009 0.021 -0.004 0.019 -0.028 0.036 0.000 0.019 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 -0.024 0.038 0.004 0.016 -0.006 0.030 0.006 0.018 -0.012 0.165 0.029 0.043 0.006 0.020 10/07/21 -0.033 0.045 -0.003 0.022 -0.007 0.031 -0.015 0.019 -0.056 0.194 -0.049 0.066 0.013 0.023 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.013 0.017 0.000 0.019 -0.039 0.067 0.001 0.019 0.006 0.026 0.001 0.121 0.183 0.086 10/07/21 0.010 0.023 0.002 0.024 -0.034 0.076 0.013 0.017 0.002 0.033 0.152 0.151 0.024 0.084 LOCATION 10 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.625 0.224 3.505 0.463 -0.007 0.113 0.000 0.014 -0.008 0.016 -0.002 0.034 0.001 0.015 10/07/21 1.074 0.305 2.772 0.529 -0.101 0.128 0.005 0.016 0.006 0.017 -0.025 0.035 -0.017 0.017 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131 T+H (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.003 0.035 0.003 0.014 -0.002 0.024 0.007 0.014 -0.079 0.127 0.004 0.038 0.015 0.017 10/07/21 -0.023 0.037 -0.012 0.017 -0.016 0.027 0.014 0.015 -0.033 0.156 -0.009 0.038 -0.003 0.016 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.016 0.018 0.000 0.016 -0.005 0.050 -0.008 0.015 0.014 0.023 0.082 0.093 0.077 0.060 10/07/21 0.008 0.019 0.001 0.019 -0.027 0.057 0.014 0.018 0.004 0.022 0.026 0.094 0.178 0.103 Results in bold type are positive.

3-22

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 9 BROADLEAF VEGETATION (pCi/g wet wt.)

LOCATION 17 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.746 0.272 2.635 0.514 -0.020 0.120 -0.002 0.016 0.004 0.014 0.000 0.031 0.005 0.017 10/07/21 2.329 0.557 3.354 0.718 -0.117 0.193 0.010 0.025 0.008 0.021 -0.002 0.058 0.009 0.028 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 -0.037 0.045 0.002 0.014 0.005 0.027 0.004 0.013 -0.182 0.164 -0.012 0.035 -0.014 0.017 10/07/21 -0.026 0.062 0.017 0.025 0.050 0.042 -0.006 0.024 -0.149 0.256 -0.046 0.070 -0.017 0.029 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.000 0.020 0.008 0.015 0.052 0.063 -0.004 0.025 0.000 0.020 0.113 0.086 0.040 0.075 10/07/21 0.018 0.026 0.006 0.028 0.077 0.093 -0.022 0.026 -0.022 0.035 -0.048 0.151 0.268 0.136 LOCATION 26C COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 1.129 0.261 4.712 0.633 0.005 0.123 -0.004 0.015 -0.001 0.014 0.004 0.032 0.002 0.013 10/07/21 2.797 0.681 4.259 0.869 -0.065 0.210 0.016 0.024 0.005 0.029 0.003 0.052 0.011 0.021 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 -0.040 0.036 -0.002 0.013 0.004 0.026 0.001 0.015 -0.112 0.126 0.019 0.040 0.007 0.017 10/07/21 -0.073 0.078 0.014 0.022 0.012 0.035 -0.018 0.024 0.216 0.224 0.001 0.076 0.010 0.025 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

06/22/21 0.005 0.017 0.025 0.015 -0.040 0.053 -0.003 0.019 -0.005 0.020 -0.060 0.082 0.048 0.060 10/07/21 0.001 0.027 -0.006 0.028 0.004 0.087 0.002 0.030 -0.023 0.037 -0.009 0.160 0.129 0.113 C= Control location, Background location Results in bold type are positi-e.

3-23

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 10 SEA WATER (pCi/1)

LOCATION 32 COLLECTION DATE H-3 Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

~ (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

01/26/21 108 169 -2.27 36.3 313 97 2.87 31.6 0.43 3.96 -0.97 4.22 1.66 9.12 02/23/21 242 189 -24.0 40.5 278 111 -1.42 41.7 1.53 3.92 -0.32 4.37 -1.52 9.14 03/30/21 178 194 18.4 35.4 311 93 -22.1 41.5 -1.26 3.95 -0.78 4.89 0.89 8.96 04/27/21 866 242 2.10 32.3 378 104 11.8 31.0 -4.43 3.97 -2.83 4.35 -5.50 8.48 05/25/21 524 125 5.80 25.0 261 109 12.3 33.3 -0.48 3.88 0.34 4.02 -0.80 8.09 06/30/21 319 119 1.93 27.3 285 87 -4.11 32.3 -0.37 3.19 1.38 3.68 -2.94 7.81 07/27/21 911 167 -11.3 31.7 235 105 2.25 31.8 0.49 3.57 3.32 3.69 2.19 7.30 08/31/21 872 160 -4.26 31.6 305 94 -6.59 27.9 5.23 4.49 -2.14 4.26 5.97 8.10 09/28/21 1060 228 11.2 35.1 332 95 28.3 36.4 0.90 3.88 0.71 3.66 -8.05 8.84 10/25/21 39 178 -4.49 25.0 187 81 11.0 23.6 0.00 3.25 0.76 2.71 -0.24 5.82 11/29/21 477 134 18.0 40.6 285 125 20.1 39.8 0.06 3.87 0.83 4.25 4.57 8.90 12/28/21 193 128 -19.1 33.0 200 126 17.7 36.5 1.57 3.97 1.22 4.05 2.38 7.92 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

~ (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

01/26/21 0.67 4.34 4.17 8.04 2.60 4.47 -1.33 6.49 -2.56 3.15 -0.21 32.7 -1.17 10.1 02/23/21 -0.80 4.18 3.07 9.71 3.94 5.00 4.63 7.28 1.65 5.13 1.43 35.8 5.06 13.4 03/30/21 5.04 4.41 -15.8 10.6 2.19 4.55 -1.22 7.12 1.92 4.87 -15.3 36.0 1.50 12.0 04/27/21 -0.02 4.44 -20.0 9.76 -1.98 3.60 3.41 7.69 -1.15 3.94 3.18 36.2 -2.91 10.3 05/25/21 -0.51 3.72 0.37 7.51 1.15 4.24 0.92 7.10 -1.75 3.52 -6.74 36.7 -4.88 10.3 06/30/21 1.63 4.28 5.73 8.86 -2.21 3.11 6.86 5.89 -0.05 3.23 -0.03 35.9 -2.34 11.8 07/27/21 -0.82 3.74 0.44 9.11 -0.38 3.93 -3.90 7.70 -2.79 3.73 30.8 37.4 4.15 10.2 08/31/21 -1.63 5.32 -1.90 9.01 -1.45 3.98 2.71 6.32 0.25 4.02 17.0 30.8 -4.55 11.2 09/28/21 -3.40 3.69 -1.22 9.00 0.84 3.50 -4.87 6.31 -1.84 4.11 -1.64 40.1 -3.31 12.2 10/25/21 1.22 3.43 -0.49 6.83 3.47 2.94 -2.76 5.74 0.19 3.13 10.0 28.5 -3.55 7.56 11/29/21 2.01 4.44 -7.72 10.2 0.60 4.46 6.74 7.48 -0.48 4.68 -7.64 42.3 4.42 14.7 12/28/21 3.65 5.60 -9.08 8.39 -3.42 5.06 -0.76 8.35 1.86 4.65 -21.9 36.6 -7.75 13.4 Results in bold type are positive.

3-24

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 10 SEA WATER (pCi/1)

LOCATION 32 Cont'd COLLECTION DATE 1-131 Cs-134 Cs-137 Ba-140 La-140 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

01/26/21 1.96 3.55 -1.14 4.77 -3.26 4.87 -0.48 15.7 1.59 4.09 3.20 12.1 02/23/21 -3.87 4.78 -2.38 5.31 2.34 5.38 4.44 17.2 2.31 4.82 8.52 16.3 03/30/21 2.72 8.36 3.33 4.93 -2.83 4.18 4.75 19.8 --4.46 6.51 -2.92 15.4 04/27/21 3.00 6.14 2.29 3.93 -0.47 3.69 -1.72 18.1 -3.71 6.01 --4.72 16.4 05/25/21 -1.15 4.18 1.57 4.38 -2.15 3.18 10.2 14.3 --4.88 5.14 8.65 14.0 06/30/21 1.27 4.60 -0.87 4.28 --4.03 4.05 -1.35 13.3 -5.78 4.15 5.54 14.2 07/27/21 0.03 4.31 -0.52 3.90 -0.37 4.24 --4.43 14.6 2.08 3.93 -20.5 15.0 08/31/21 1.60 4.40 3.23 4.85 -3.89 4.38 3.16 15.4 -1.31 5.13 -0.22 15.0 09/28/21 -0.23 4.66 1.41 4.50 1.80 3.99 4.05 15.3 -2.16 4.58 1.67 16.1 10/25/21 -0.03 3.21 2.10 3.25 -3.39 3.66 6.43 12.0 -1.21 4.28 -2.13 12.8 11/29/21 0.44 5.10 -0.47 3.87 -0.91 5.23 11.3 16.3 0.03 4.81 -16.1 16.4 12/28/21 --4.73 5.22 0.98 4.83 -3.06 4.64 -19.52 19.6 -3.15 5.25 -0.65 17.9 LOCATION 37C COLLECTION DATE H-3 Be-7 K--40 Cr-51 Mn-54 Co-58 Fe-59

~ (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

03/23/21 -37 110 -22.0 38.9 292 108 5.83 41.3 0.51 4.04 -1.87 4.93 -1.99 8.20 06/22/21 19 173 -1.08 27.0 188 88 -34.3 30.2 2.62 3.38 1.93 3.62 -3.22 7.68 09/21/21 15 164 --4.76 30.5 234 87 -1.12 31.5 -0.35 3.24 1.28 3.76 2.54 6.63 12/20/21 2 108 19.1 28.2 296 79 -18.0 28.2 -0.37 2.98 1.81 2.92 3.48 5.65 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

~ (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

03/23/21 -1.33 4.77 3.90 10.7 -1.00 4.96 2.63 7.40 -1.12 4.91 36.8 43.8 12.2 14.0 06/22/21 2.80 4.06 0.73 7.86 1.21 3.44 1.18 6.36 --4.31 4.10 53.5 37.1 3.55 9.02 09/21/21 -2.24 3.31 -1.42 9.26 2.29 3.82 0.77 5.55 -0.26 3.78 4.40 35.1 2.45 9.58 12/20/21 1.15 3.20 -8.42 8.78 3.31 3.03 -0.49 5.23 0.05 3.48 -9.23 29.5 5.49 9.09 COLLECTION DATE 1-131 Cs-134 Cs-137 Ba-140 La-140 Ac-228

~ (+/-) (+/-) (+/-) (+/-) (+/-)

03/23/21 -5.01 6.71 1.60 5.18 -2.24 4.98 -14.1 21.4 4.11 6.30 1.18 14.1 06/22/21 2.31 3.98 1.04 4.01 -2.16 3.52 4.09 12.9 -2.70 3.96 -2.77 13.4 09/21/21 -0.97 4.02 1.19 4.52 -1.58 3.69 12.2 13.4 1.12 4.83 -8.87 12.9 12/20/21 2.03 4.40 -1.16 3.28 2.40 3.29 -7.79 12.8 0.44 3.71 --4.13 12.0 C= Control location, Background location Results in bold type are positive.

3-25

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

31 06/10/21 -0.007 0.179 14.49 1.124 0.052 0.174 0.021 0.026 -0.026 0.024 -0.050 0.055 31 12/15/21 -0.164 0.319 15.17 1.358 0.131 0.322 0.014 0.036 -0.012 0.041 -0.063 0.078 32 06/24/21 -0.411 0.441 19.99 2.071 -0.029 0.429 -0.017 0.050 0.012 0.049 0.117 0.101 32 12/15/21 0.095 0.283 13.32 1.325 0.116 0.318 -0.012 0.037 -0.030 0.032 0.006 0.068 33 06/09/21 -0.192 0.211 18.74 1.292 0.054 0.231 0.008 0.026 -0.012 0.027 0.020 0.064 33 12/15/21 0.002 0.236 14.09 1.358 0.012 0.216 -0.023 0.026 -0.006 0.026 0.041 0.074 34 06/09/21 0.085 0.198 12.28 1.093 0.047 0.166 0.004 0.020 -0.043 0.024 -0.021 0.050 34 12/15/21 0.057 0.236 14.59 1.438 0.110 0.231 0.016 0.031 0.011 0.028 0.005 0.062 37C 06/10/21 0.182 0.167 15.08 1.261 0.024 0.177 0.007 0.024 0.011 0.021 -0.051 0.056 37C 12/15/21 0.100 0.402 15.58 1.836 0.357 0.445 -0.058 0.051 0.014 0.054 0.024 0.126 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

31 06/10/21 0.002 0.027 -0.070 0.061 -0.014 0.025 -0.002 0.034 0.007 0.022 -0.113 0.225 31 12/15/21 -0.025 0.032 -0.163 0.096 -0.006 0.040 0.040 0.069 -0.006 0.033 -0.059 0.299 32 06/24/21 0.001 0.045 -0.128 0.128 -0.016 0.051 0.039 0.097 0.020 0.052 -0.100 0.472 32 12/15/21 -0.013 0.035 0.014 0.094 0.069 0.038 0.034 0.056 0.004 0.036 0.039 0.298 33 06/09/21 -0.005 0.028 -0.164 0.080 0.030 0.027 0.067 0.047 0.011 0.024 0.131 0.237 33 12/15/21 0.012 0.030 -0.014 0.088 0.013 0.033 -0.006 0.050 -0.002 0.025 -0.044 0.236 34 06/09/21 0.028 0.024 -0.106 0.058 -0.010 0.022 -0.010 0.041 -0.003 0.023 -0.069 0.185 34 12/15/21 -0.002 0.033 -0.033 0.071 -0.012 0.029 0.003 0.052 0.011 0.028 -0.193 0.251 37C 06/10/21 -0.001 0.024 -0.033 0.065 -0.003 0.023 -0.007 0.040 0.006 0.019 0.198 0.198 37C 12/15/21 0.023 0.051 -0.095 0.153 -0.010 0.056 -0.005 0.089 0.003 0.055 -0.499 0.492 C= Control location, Background location Results in bold type are positi.e.

3-26

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

31 06/10/21 -0.002 0.019 -0.006 0.053 -0.021 0.029 0.026 0.027 0.002 0.024 0.532 0.170 31 12/15/21 -0.003 0.036 -0.003 0.094 0.034 0.065 0.082 0.045 -0.005 0.044 1.014 0.249 32 06/24/21 -0.027 0.049 -0.045 0.125 -0.049 0.086 0.037 0.064 -0.013 0.056 0.997 0.403 32 12/15/21 -0.018 0.032 0.057 0.090 -0.015 0.067 0.048 0.042 0.016 0.037 0.870 0.217 33 06/09/21 -0.011 0.025 0.054 0.071 0.015 0.035 0.015 0.030 -0.019 0.030 0.327 0.130 33 12/15/21 0.010 0.025 0.021 0.063 0.008 0.047 -0.009 0.028 -0.007 0.027 0.203 0.131 34 06/09/21 -0.002 0.019 -0.023 0.054 0.005 0.029 0.008 0.025 -0.004 0.020 0.236 0.105 34 12/15/21 0.001 0.025 0.041 0.064 0.029 0.046 -0.002 0.031 0.003 0.028 0.323 0.178 37C 06/10/21 -0.018 0.022 0.028 0.053 0.004 0.025 0.006 0.026 0.013 0.023 0.237 0.113 37C 12/15/21 -0.054 0.050 0.053 0.145 -0.036 0.089 0.057 0.050 0.014 0.054 0.575 0.343 C= Control location, Background location 3-27

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

--- (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

29 03/11/21 0.1913 0.1026 5.5290 0.5529 -0.0246 0.0920 0.0039 0.0114 -0.0054 0.0117 -0.0097 0.0249 29 06/15/21 0.4267 0.2562 5.1360 0.5808 -0.0309 0.1156 -0.0103 0.0139 0.0000 0.0140 -0.0041 0.0304 29 09/15/21 0.0326 0.1323 6.0630 0.6934 -0.0832 0.1116 -0.0043 0.0144 -0.0033 0.0156 0.0310 0.0342 29 12/15/21 0.1757 0.1468 7.7510 0.8112 -0.1584 0.1488 0.0046 0.0185 -0.0165 0.0153 -0.0149 0.0417 32 03/11/21 0.0137 0.1176 6.7640 0.6849 -0.0080 0.1127 -0.0170 0.0152 -0.0023 0.0123 -0.0100 0.0309 32 06/15/21 0.0990 0.1029 5.4450 0.5765 -0.0149 0.0883 0.0082 0.0125 -0.0074 0.0107 0.0161 0.0262 32 09/15/21 0.1379 0.1142 7.8410 0.7274 0.0295 0.1143 0.0007 0.0143 0.0105 0.0144 0.0114 0.0340 32 12/15/21 0.1411 0.1241 9.8400 0.7874 -0.0257 0.1376 -0.0022 0.0151 0.0087 0.0164 -0.0318 0.0383 35 03/11/21 0.2459 0.1433 6.2660 0.6657 0.0341 0.1358 -0.0096 0.0157 -0.0147 0.0150 0.0070 0.0369 35 06/22/21 0.3220 0.1450 4.4730 0.4820 -0.0040 0.0922 -0.0090 0.0107 -0.0084 0.0101 -0.0125 0.0230 35 09/16/21 0.1280 0.1142 7.6240 0.5890 -0.0650 0.1084 0.0059 0.0126 0.0084 0.0118 -0.0121 0.0300 35 12/15/21 0.3549 0.1255 6.1570 0.5603 -0.0706 0.0994 0.0025 0.0098 -0.0035 0.0118 -0.0093 0.0227 36C 03/18/21 0.0319 0.1656 4.7220 0.5936 -0.0620 0.1384 -0.0010 0.0171 0.0034 0.0167 0.0193 0.0318 36C 06/24/21 0.1327 0.1009 5.0730 0.5029 -0.0778 0.0914 0.0051 0.0114 -0.0025 0.0105 -0.0109 0.0268 36C 09/22/21 0.0892 0.0924 4.7880 0.4836 -0.0101 0.0780 0.0026 0.0098 -0.0030 0.0104 0.0003 0.0223 36C 12/15/21 0.3183 0.1401 8.7310 0.6789 -0.0337 0.1388 0.0053 0.0145 -0.0106 0.0137 -0.0039 0.0345 C= Control location, Background location Results in bold type are positive.

3-28

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

--- (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

29 03/11/21 -0.0020 0.0110 -0.0037 0.0317 -0.0052 0.0121 0.0095 0.0204 -0.0012 0.0121 -0.0172 0.1098 29 06/15/21 -0.0010 0.0131 0.0069 0.0376 0.0144 0.0144 0.0148 0.0241 -0.0035 0.0153 -0.1347 0.1468 29 09/15/21 0.0092 0.0139 -0.0109 0.0372 0.0096 0.0144 -0.0140 0.0249 -0.0048 0.0129 0.0478 0.1323 29 12/15/21 0.0063 0.0140 -0.0525 0.0504 0.0170 0.0164 -0.0083 0.0282 -0.0081 0.0142 0.0421 0.1332 32 03/11/21 -0.0056 0.0128 -0.0410 0.0410 -0.0002 0.0145 0.0273 0.0232 0.0014 0.0119 -0.1392 0.1149 32 06/15/21 -0.0002 0.0126 -0.0054 0.0319 0.0013 0.0122 0.0002 0.0232 -0.0005 0.0112 0.0094 0.0938 32 09/15/21 -0.0031 0.0142 -0.0182 0.0392 -0.0016 0.0150 0.0235 0.0241 -0.0007 0.0144 -0.0270 0.1229 32 12/15/21 -0.0113 0.0169 -0.0180 0.0375 0.0055 0.0173 -0.0007 0.0285 0.0064 0.0154 0.0272 0.1431 35 03/11/21 -0.0050 0.0165 -0.0142 0.0413 -0.0036 0.0152 0.0237 0.0288 0.0085 0.0144 -0.0181 0.1459 35 06/22/21 0.0081 0.0100 -0.0228 0.0280 0.0000 0.0093 0.0101 0.0204 0.0026 0.0100 -0.0525 0.0896 35 09/16/21 0.0003 0.0125 -0.0377 0.0359 -0.0038 0.0122 0.0086 0.0222 -0.0092 0.0121 -0.0765 0.0975 35 12/15/21 -0.0039 0.0107 0.0042 0.0269 -0.0035 0.0121 -0.0012 0.0198 0.0036 0.0102 -0.0697 0.1007 36C 03/18/21 -0.0011 0.0141 -0.0066 0.0338 0.0053 0.0169 0.0154 0.0298 0.0084 0.0165 0.0525 0.1482 36C 06/24/21 0.0094 0.0108 -0.0104 0.0261 0.0029 0.0108 -0.0022 0.0199 -0.0049 0.0116 -0.0218 0.0862 36C 09/22/21 -0.0042 0.0097 0.0078 0.0271 0.0035 0.0111 0.0018 0.0176 0.0057 0.0097 -0.1069 0.0927 36C 12/15/21 0.0121 0.0145 -0.0253 0.0399 0.0131 0.0136 0.0097 0.0273 0.0061 0.0163 -0.0137 0.1371 C= Control location, Background location 3-29

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

29 03/11/21 -0.0020 0.0110 0.0147 0.0298 0.0041 0.0181 0.0061 0.0133 -0.0034 0.0131 0.0286 0.0481 29 06/15/21 0.0132 0.0142 0.0274 0.0401 -0.0024 0.0173 0.0057 0.0164 -0.0106 0.0167 0.0982 0.0718 29 09/15/21 0.0077 0.0115 -0.0095 0.0343 0.0015 0.0239 0.0134 0.0149 0.0063 0.0136 0.0658 0.0582 29 12/15/21 -0.0033 0.0150 0.0018 0.0368 0.0163 0.0247 -0.0008 0.0163 -0.0042 0.0160 0.1413 0.0834 32 03/11/21 0.0016 0.0109 0.0066 0.0309 -0.0296 0.0206 0.0102 0.0155 -0.0068 0.0140 0.0184 0.0573 32 06/15/21 0.0017 0.0123 0.0144 0.0298 0.0070 0.0125 0.0087 0.0138 0.0007 0.0137 0.0568 0.0511 32 09/15/21 -0.0133 0.0137 0.0216 0.0291 0.0114 0.0264 0.0096 0.0147 -0.0008 0.0146 0.0670 0.0567 32 12/15/21 0.0022 0.0147 -0.0449 0.0412 -0.0028 0.0300 -0.0056 0.0158 -0.0088 0.0162 0.0920 0.0773 35 03/11/21 -0.0113 0.0145 -0.0243 0.0352 0.0010 0.0239 -0.0045 0.0152 0.0037 0.0154 0.0753 0.0655 35 06/22/21 -0.0074 0.0108 0.0193 0.0267 0.0072 0.0120 0.0053 0.0134 0.0001 0.0109 0.0522 0.0492 35 09/16/21 0.0105 0.0114 -0.0056 0.0364 0.0193 0.0211 0.0090 0.0120 0.0023 0.0126 0.0118 0.0503 35 12/15/21 -0.0028 0.0093 -0.0026 0.0261 0.0110 0.0187 0.0067 0.0136 -0.0007 0.0103 0.0614 0.0523 36C 03/18/21 0.0043 0.0163 0.0196 0.0462 -0.0029 0.0298 -0.0028 0.0213 0.0100 0.0173 0.0322 0.0674 36C 06/24/21 -0.0062 0.0105 0.0096 0.0245 -0.0162 0.0159 0.0054 0.0128 0.0007 0.0114 0.0129 0.0471 36C 09/22/21 -0.0115 0.0097 0.0021 0.0287 0.0005 0.0099 -0.0073 0.0124 0.0063 0.0104 0.0586 0.0467 36C 12/15/21 0.0075 0.0136 -0.0255 0.0410 0.0113 0.0233 0.0119 0.0158 -0.0156 0.0159 0.0412 0.0693 C= Control location, Background location 3-30

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 13 FISH (pCi/g wet wt.)

COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

28 06/17/21 0.075 0.240 3.135 0.946 -0.076 0.233 0.002 0.033 0.000 0.033 -0.018 0.067 28 10/14/21 0.040 0.235 3.474 0.864 0.035 0.224 0.015 0.031 -0.011 0.029 0.041 0.051 35 05/20/21 0.001 0.233 3.353 1.025 -0.093 0.258 -0.005 0.033 0.006 0.032 0.029 0.072 35 10/14/21 -0.205 0.241 4.306 0.957 0.052 0.229 -0.001 0.028 0.001 0.029 -0.019 0.060 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

28 06/17/21 0.007 0.037 -0.030 0.071 0.003 0.032 0.033 0.055 -0.016 0.027 -0.216 0.271 28 10/14/21 0.001 0.028 -0.079 0.082 -0.020 0.029 -0.011 0.055 0.012 0.029 0.024 0.265 35 05/20/21 0.011 0.022 0.006 0.074 -0.006 0.033 -0.005 0.058 -0.001 0.029 0.016 0.334 35 10/14/21 0.028 0.029 -0.053 0.077 -0.008 0.030 0.006 0.053 -0.004 0.030 0.047 0.306 COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

28 06/17/21 -0.009 0.028 -0.053 0.076 -0.011 0.051 0.009 0.039 0.012 0.033 -0.034 0.129 28 10/14/21 -0.017 0.026 0.040 0.075 -0.022 0.038 -0.011 0.032 0.018 0.028 -0.002 0.122 35 05/20/21 0.013 0.034 -0.033 0.077 0.008 0.032 -0.021 0.035 -0.025 0.041 0.033 0.139 35 10/14/21 -0.008 0.026 -0.093 0.074 0.008 0.046 0.008 0.031 -0.010 0.032 0.006 0.125 Results in bold type are positive.

3-31

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 14 OYSTERS (pCi/g wet wt.)

COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

-- (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

31 05/18/21 0.254 0.231 1.907 0.814 -0.117 0.210 -0.009 0.036 -0.003 0.030 -0.026 0.073 31 11/29/21 0.004 0.269 2.407 1.018 0.193 0.320 -0.006 0.043 -0.007 0.036 -0.031 0.065 89C 03/18/21 -0.030 0.313 1.651 0.882 -0.149 0.349 0.015 0.041 -0.012 0.042 -0.008 0.084 89C 10/14/21 0.166 0.273 2.208 0.798 -0.007 0.279 0.002 0.029 -0.009 0.030 -0.053 0.065 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

31 05/18/21 -0.004 0.034 0.040 0.075 -0.031 0.033 0.005 0.047 0.006 0.028 -0.086 0.268 31 11/29/21 0.005 0.039 0.009 0.091 0.000 0.043 -0.019 0.067 -0.020 0.044 -0.064 0.374 89C 03/18/21 -0.015 0.041 -0.060 0.095 0.000 0.040 -0.004 0.070 -0.002 0.045 0.093 0.405 89C 10/14/21 -0.018 0.032 -0.049 0.065 0.003 0.029 -0.002 0.057 0.000 0.032 -0.014 0.270 COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

31 05/18/21 -0.001 0.031 -0.021 0.074 -0.005 0.031 -0.005 0.038 -0.006 0.036 0.040 0.142 31 11/29/21 0.001 0.037 0.030 0.107 0.017 0.040 0.015 0.044 0.023 0.039 0.065 0.157 89C 03/18/21 0.026 0.039 -0.091 0.097 -0.051 0.094 -0.032 0.049 -0.042 0.043 0.104 0.163 89C 10/14/21 -0.019 0.029 -0.025 0.082 0.013 0.052 0.003 0.033 0.036 0.031 0.125 0.121 Results in bold type are positive.

C= Control location, Background location 3-32

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE15 CLAMS (pCi/g wet wt.)

COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

- (+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

29 06/29/21 -0.035 0.365 1.538 0.956 0.265 0.356 -0.021 0.042 -0.030 0.038 0.023 0.080 29 10/20/21 0.036 0.303 1.614 0.897 0.202 0.301 -0.008 0.029 -0.004 0.031 -0.007 0.073 31 06/29/21 -0.066 0.236 2.078 0.926 -0.042 0.200 0.016 0.029 0.014 0.032 0.006 0.069 31 10/20/21 -0.051 0.242 2.036 0.863 -0.046 0.262 -0.009 0.036 -0.009 0.035 -0.056 0.079 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

29 06/29/21 0.022 0.045 -0.042 0.089 0.061 0.043 0.042 0.081 0.019 0.044 0.137 0.371 29 10/20/21 -0.014 0.038 0.023 0.074 -0.011 0.035 -0.025 0.054 0.010 0.033 0.124 0.343 31 06/29/21 0.019 0.042 -0.030 0.060 -0.015 0.038 0.001 0.044 -0.008 0.030 0.109 0.310 31 10/20/21 0.014 0.038 -0.040 0.080 -0.007 0.031 -0.028 0.063 -0.027 0.030 -0.046 0.296 COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

29 06/29/21 0.007 0.042 -0.029 0.106 -0.059 0.048 -0.024 0.053 -0.002 0.048 0.025 0.192 29 10/20/21 -0.010 0.035 -0.072 0.091 -0.024 0.048 -0.009 0.041 0.013 0.041 0.084 0.128 31 06/29/21 0.004 0.031 -0.008 0.089 -0.013 0.030 0.008 0.030 0.006 0.035 0.040 0.122 31 10/20/21 -0.001 0.031 -0.045 0.078 0.006 0.038 0.016 0.037 -0.005 0.035 -0.023 0.150 Results in bold type are positive.

3-33

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 TABLE 16 LOBSTERS (pCi/g wet wt.)

COLLECTION LOCATION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

35 05/20/21 -0.063 0.306 3.492 0.949 -0.044 0.310 -0.016 0.045 -0.012 0.041 0.009 0.083 35 11/29/21 -0.080 0.184 3.179 0.704 -0.028 0.198 -0.009 0.025 -0.019 0.024 0.007 0.045 89C 06/09/21 0.071 0.167 2.202 0.655 -0.021 0.175 0.008 0.026 -0.007 0.024 -0.009 0.044 89C 08/30/21 -0.050 0.250 2.255 0.835 -0.051 0.269 0.006 0.040 0.005 0.031 0.015 0.052 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

35 05/20/21 -0.012 0.042 -0.070 0.108 0.001 0.040 0.003 0.072 -0.019 0.035 -0.242 0.390 35 11/29/21 0.024 0.031 0.009 0.050 0.004 0.024 0.003 0.035 0.004 0.021 0.002 0.227 89C 06/09/21 0.006 0.021 -0.020 0.049 0.020 0.024 -0.012 0.040 0.003 0.020 0.063 0.201 89C 08/30/21 0.019 0.041 -0.010 0.086 0.033 0.031 -0.006 0.055 -0.006 0.032 -0.140 0.287 COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

(+/-) (+/-) (+/-) (+/-) (+/-) (+/-)

35 05/20/21 -0.004 0.043 0.053 0.124 -0.021 0.043 0.014 0.042 0.026 0.051 0.045 0.168 35 11/29/21 0.024 0.025 0.024 0.065 -0.010 0.024 -0.010 0.024 -0.033 0.026 0.037 0.100 89C 06/09/21 0.005 0.022 -0.036 0.066 0.017 0.024 -0.002 0.021 -0.012 0.023 -0.007 0.068 89C 08/30/21 -0.011 0.033 0.052 0.076 -0.016 0.038 -0.021 0.033 0.002 0.034 0.014 0.127 C= Control Location, Background location Results in bold type are positi.e.

3-34

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

4. DISCUSSION OF RESULTS This section summarizes the results of the analyses on the REMP samples. The only case where station related radioactivity was detected was tritium (H-3) in seawater collected at the quarry discharge point. This was within the station boundary. The naturally occurring nuclides of Be-7, K-40, and Ac-228 were detected in some samples. Be-7 is from cosmic radiation. It was observed in air, vegetation, broadleaf vegetation and in some fucus samples. K-40 and Ac-228 are two common terrestrial isotopes. K-40 was not seen in well water samples but was observed in other samples. Ac-228 was observed in two sediment samples and in two soil samples. Cs-137 and Sr-90 from atmospheric nuclear weapons testing in the 1960's has been observed in the past. A study by the Connecticut Department of Energy and Environmental Protection in 2006 affirmed that radioactivity from nuclear weapons testing has decreased to almost non-detectable levels (Reference 19). Since 2006 detection of Cs- 137 and Sr-90 in environmental samples has been rare. Cs-137 from nuclear weapons testing was analyzed at MDC (Minimum Detectable Concentration) in all soil samples in 2021. Based on sample location, it is not unexpected to identify the presence of Cs-137 in undisturbed soil 22 . The remaining REMP samples obtained during 2021 did not indicate the presence of Cs-137 and the overall trend is decreasing (Figure 4.5-1).

4.1 Gamma Exposure Rate {Table 1)

Gamma exposure rate is determined from the integrated exposure measured over a calendar quarter using TLDs. Prior to 1990, Victoreen CaF2(Mn) glass bulb dosimeters were used for these measurements. In 1990, these were replaced by Harshaw CaF2(Mn) chips. In 2000, the CaF2(Mn) TLDs, were replaced with the CaSO4(Tm) Panasonic model UD-814 AS1 TLDs.

Readings are recorded as µR/hr. The unit µR stands for 'micro-roentgen' with a 'micro' being one-millionth of a roentgen. A roentgen is the quantity of radiation equal to 87.6 ergs of energy per gram of air. For gamma exposure a micro-roentgen is equivalent to a micro-rem, a measure of dose to man.

The dosimeters are strategically placed at a number of onsite locations, as well as at inner and outer offsite locations. Starting in 2001, the collection of TLDs was changed from monthly to quarterly and additional measurement locations were incorporated into the REMP requirements listed in the REMODCM (Reference 8). Three more locations (73-75) were added in mid-2003 to prepare for monitoring the potential effect from the ISFSI. Two dry cask containers were loaded in the first quarter of 2005, three in 2006, three in 2007, three in 2009, three in 2010, four in 2012, six in 2015, five in 2016, three in 2018, seven in 2019, and six in 2021.

Prior to any cask loading, the background readings average recorded from mid 2003 - 2004 were: 9.5 µR/hour at Location 73, 7.5 µR/hour at Location 74, and 6.9 µR/hour at Location 75.

In 2021, the annual average exposure rate measurement for the ISFSI area was 7.0 µR/hour at Location 73, 7.6 µR/hour at Location 74, and 6.7 µR/hour at Location 75. The station offsite dose from ISFSI for 2021 was 0.04 mrem/year, which is below the 25 mrem/year limit per 40.190 CFR.

In the 4th quarter of 2021 two TLDs were lost at locations #14C and #55. A condition report was initiated.

4-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Table 1 in Section 3.2 lists the exposure rate measurements for all 43 monitored locations.

These measurements demonstrate the general variations in background radiation between the various onsite and offsite locations and include gamma exposure from all sources of radioactivity.

For example, the Weather Shack (Location 2), Quarry East (Location 5), Environmental Laboratory (Location 8), Bay Point Beach (Location 9), Goshen Fire Dept (Location 10), and Corey Road (Location 48) experience higher exposure rates due to their proximity to granite beds and stonewalls. In addition, the Mystic (Location 13C) and Ledyard (Location 14C) control locations experience relatively higher background exposure rate than the other control locations in Norwich and Old Lyme (Locations 15C and 16C).

Figure 4.1-1 shows a historical trend of TLD exposure rate measurements, comparing an annual average of all indicator TLDs, an annual average of all control TLDs, and the annual average of the two most critical indicator locations which are used to represent the two closest site boundary residences in the North-northwest and Northeast directions. The average indicator and control readings were both about 8.0 µR/hour.

Figure 4.1-1 also relates the difference in indicator locations 1 and 3 and the annual average of all indicator TLDs to the annual average of the control TLDs collected and measured during coincident periods throughout the year. Locations 1 and 3 are important because they are onsite and located between the plant and nearby populated areas. As discussed earlier, the exposure measurements of many indicator locations on site (and two of the control locations) are influenced by natural background exposure differences caused by the many granite outcroppings typical of the local area. Figure 4.1-1 shows that the annual average at indicator Location 3 was lower in gamma exposure rate than the average control gamma exposure rate. These differences are the result of the differences in granite at these locations. Location 3 was moved in the second quarter 2009 to minimize the effect of tree covering for the air sampler also located at this location. The 2000 to 2009 data for Location 3 shows an increase likely attributable to 1-3 µR/hr gradients observed from the granite bedrock of the MPS Site (Reference 21). Over the last 10 years there has been no significant change in the annual gamma exposure rate (Figure 4.1-1).

4-2

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Figure 4.1-1 Annual Gamma Exposure Rate - 20 Year History 10

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 4.2 Air Particulate Gross Beta Radioactivity (Table 2)

Air is continuously sampled at seven inner ring (0 to 2 miles) locations and one control location (14 miles N) by passing it through glass fiber particulate filters. These samples are collected every two weeks and analyzed for gross beta radioactivity. Results are shown on Figure 4.2-1 and Table 2. Gross beta activity remained at levels similar to that seen over the last decade.

Indicators and control monitoring locations continue to show no significant variation in measured activities and are within the expected calculated uncertainty of +/-0.002 pCi/m 3 (see Figure 4.2-2) .

This indicates that any station contribution is not measurable.

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 4.3 Airborne Iodine (Table 3)

Charcoal cartridges are included at all of the air particulate monitoring stations for the collection of atmospheric iodine. These cartridges were analyzed for 1-131 every two weeks . No detectable levels of 1-131 were seen in the 2021 charcoal samples.

4.4 Air Particulate Gamma (Table 4)

The air particulate samples that are utilized for the gross beta analyses are composited quarterly and analyzed for gamma emitting isotopes including strontium analysis as a substitute for milk analysis. The results, as shown in Table 4, indicate the presence of naturally occurring Be-7, which is produced by cosmic radiation. No other positive results are seen. These analyses indicate that there was not any detectable station related radioactivity in the air samples.

4.5 Soil (Table 5)

This media is collected annually from one control and two indicator locations. MPS has collected and analyzed soil since 2001. Prior to 2001, soil had not been sampled for over fifteen years because station related detectable activity had not been detected. Since 2001 no station detectable activity has been seen in these samples. Naturally occurring K-40 and Ac-228 is detected in soil. Cs-137 from nuclear weapons testing was analyzed at MDC (Minimum Detectable Concentration) in all soil samples in 2021 . The results of these samples, allows for the determination of baseline activity levels in soil. This is particularly important for Cs-137, since significant levels from past weapons testing fallout remain in the soil. Figure 4.5-1 shows the trend of Cs-137 in soil samples, the trend appears to be declining with time. Baseline levels should be useful in the future, when site characterization and decommissioning of the station become the focus during preparations for license termination .

Figure 4.5-1 Cs-137 in Soil 2

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 4.6 Milk (Table 6)

Each year the Land Use Census is used to identify locations of milk animals that should be included in the monitoring program. It is performed annually and is maintained by observations, door-to-door surveys, and consulting with local agriculture authorities. The 2021 census is listed in Appendix A If a new dairy farm is identified close enough to MPS to be considered an indicator location, the collection of cow milk at that location would be added.

In 2021, the Land Use Census did not locate any location of commercial milk farms within 10 miles of Millstone Power Station. Prior to 2018, milk samples were obtained and analyzed for strontium from a farm that is no longer producing milk. A valid substitute for milk analysis is air filters strontium analysis and gamma analysis of broadleaf vegetation. This strontium analysis of air filter was determined to be more effective than milk analysis, MP-HPO-17067. The air sampling stations are located closer to the plant and in the predominant downwind direction.

4.7 Well Water (Table 7)

All REMP well samples including ISFSI well samples were less than the Lower Level of Detection Limit (LLD). Additional samples from other wells were obtained as part of the Groundwater Protection Program (GWPP). Results from the GWPP are reported in the MPS annual "Radioactive Effluent Release Report" for 2021. ISFSI well results have been documented in Table 7 as required by the Connecticut Sitting Council.

4.8 Fruits and Vegetables (Table 8)

Consistent with past years, this media did not show any station effects. Naturally occurring K-40 and cosmic produced BE-7 were the only isotopes detected in the samples.

4.9 Broad Leaf Vegetation (Table 9)

Consistent with past years, this media did not show any station effects. Most samples had detectable levels of cosmic produced Be-7 and naturally occurring K-40. Occasionally these samples have indicated positive levels of Cs-137 in the past. This can be attributed to fallout from weapons testing which has been widespread in terrestrial samples for many years. Cs-137 was not detected in any of the 2021 collected Broad Leaf Vegetation samples.

4.10 Seawater (Table 10)

The guidance in Reference 15 specifies one sample upstream (control - beyond significant influence of the discharge) and one sample downstream (indicator- beyond but near the mixing zone) for surface water samples. Historically the downstream sample for MPS has been located in the vicinity of discharge (Location 32) which is prior to the mixing zone. This location was chosen since it was readily accessible and not affected by cold weather conditions. Operation of an automatic sampler at the indicator location is necessary for providing a representative sample.

Any dose consequences can be assessed by use of the appropriate dilution factors. It's not necessary to have a continuous sampler at the control location due to the historical relative consistency noted in seawater background activity near the Millstone.

4-6

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 A technician collects an aliquot from the automatic sampler at Location 32 on a weekly frequency.

These samples are composited for monthly analyses. For the Control Location, Giant's Neck (Location 37C), six weekly grab samples are obtained for quarterly compositing .

Naturally occurring K-40 was the only detectable gamma activity seen in these samples.

Measured station related levels of H-3, beta activity, in seawater from the vicinity of discharge (Location 32) were observed in most samples. Tritium releases are typically higher near outages due to the need for increased liquid processing during these times. As mentioned above, these samples are taken directly from liquid effluent flow prior to dilution into the Long Island Sound.

Tritium builds up in the reactor coolant during each fuel cycle. It is generated during station operation from fission and neutron reactions. Figure 4.10-1 shows an eighteen-year trend of Tritium (H-3) releases in the MPS liquid effluents versus the measured environmental concentrations from the vicinity of discharge location. In 2021 MPS had one outage requiring the processing and subsequent discharge of processed refueling water. The highest quarterly average H-3 value in 2021 for seawater was 1,060 pCi/I, which is well below the drinking water limit established by the Environmental Protection Agency (EPA) of 20,000 pCi/1. The total annual exposure from the liquid discharge pathway for 2021 was 0.001 mrem/yr.

Figure 4.10-1 H-3 Curies Released versus Seawater Concentration 18 Year Trend 2,500 - , - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ 2,500

-*- Cu ries discharged - REMP pCi/liter 2,000 + - - - - - -- -- - - - - - - - - - - ----ll--- - - - - - - - ,11--- - - - + 2,000 J '

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 4.11 Bottom Sediment (Table 11)

There was no station related radioactivity detected in bottom sediment samples in 2021.

Naturally occurring K-40 is seen in all samples and naturally occurring Ac-228 in some samples.

Bottom sediment is not a significant dose pathway to man, especially at areas not typically used by the public.

4.12 Aquatic Flora (Table 12)

Aquatic flora is a sensitive indicator of low levels of man-made radioactivity (e.g., Mn-54, Co- 58, Co-60, Zn-65, 1-131 and Ag-110m) in the environment so it was added as a required sample at four locations in revision 28 of the REMODCM. Naturally occurring Be-7 appears in some samples as well as the naturally occurring K-40 in all samples. This analysis indicates the lack of any station radioactivity.

4.13 Fish (Table 13)

The activity in fish is the same as that seen in the past. No activity was observed except for the naturally occurring K-40.

4.14 Oysters (Table 14)

All locations utilize oysters stocked in trays. Oyster sampling has occasionally presented challenges in obtaining the sample size required for analysis. In 2021 four adequately sized samples were obtained. Only naturally occurring K-40 was detected in the collected samples.

Oysters have a high capacity for accumulating silver and zinc. Studies have shown that oysters can accumulate as much as 50 times or more the amount of zinc compared to most other seafood. No plant related radioactivity was detected in oysters in 2021.

4.15 Clams (Table 15)

In 2021, only the naturally occurring K-40 was detected in the collected samples.

4.16 Lobsters (Table 16)

In 2021, only the naturally occurring K-40 was detected in the collected samples 4-8

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

5. REFERENCES

1) United States of America, Code of Federal Regulations, Title 10, Part 50, Appendix A Criteria 64.

2) Donald T. Oakley, "Natural Radiation Exposure in the United States," U.S. Environmental Protection Agency, ORP/SID 72-1, June 1972.

3) National Council on Radiation Protection and Measurements, Report No. 160, "Ionizing Radiation Exposures of the Population of the United States," March 2009.

4) National Council on Radiation Protection and Measurements, Report No. 94, "Exposure of the Population of the United States and Canada from Natural Background Radiation,"

December 1987.

5) United States Nuclear Regulatory Commission, Regulatory Guide 8.29, "Instructions Concerning Risks from Occupational Radiation Exposure," Revision 0, July 1981.

6) United States of America, Code of Federal Regulations, Title 10, Part 20.1302.

7) United States Nuclear Regulatory Commission, Regulatory Guide 1.109, "Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix I," Revision 1, October 1977.

8) Millstone Power Station Radiological Effluent Monitoring and Offsite Dose Calculation Manual, Revision 30, September 19, 2018

9) Millstone Power Station Unit 1 Defueled Technical Specifications, License No. DPR-21.

10) Millstone Power Station Unit 2 Technical Specifications, License No. DPR-65.

11) Millstone Power Station Unit 3 Technical Specifications, License No. NPF-49.

12) United States Nuclear Regulatory Commission, Regulatory Guide 4.1, "Program for Monitoring Radioactivity in the Environs of Nuclear Power Plants," Rev. 1, April 1975.

13) ICN/Tracerlab, "Millstone Power Station Pre-Operational Environmental Radiation Survey Program, Quarterly Reports," April 1967 to June 1970.

14) International Commission of Radiological Protection, Publication No.43, "Principles of Monitoring for the Radiation Protection of the Population," May 1984.

15) United States Nuclear Regulatory Commission, NUREG-1301, "Offsite Dose Calculation Manual Guidance: Standard Radiological Effluent Controls for Pressurized Water Reactors," April 1991.

16) United States Nuclear Regulatory Commission, Branch Technical Position, "An Acceptable Radiological Environmental Monitoring Program", Rev. 1, November 1979.

17) Reassessment of Millstone Power Station's Environmental Monitoring Data, Connecticut Department of Environmental Protection, Division of Radiation, March 2006.

18) Nuclear Regulatory Commission Regulatory Guide 4.1, Radiological Environmental Monitoring for Nuclear Power Plants, Revision 2, June 2009.

19) Division of Radiation, CT Dept. of Energy and Environmental Protection, "Reassessment of Millstone Power Station's Environmental Monitoring Data," January 2006.

20) Connecticut Sitting Council Decision and Order for ISFSI, Docket No. 265, May 27, 2004.

21) RP-16-08, "Take-Home Thermoluminescent Dosimeter Variance", June 17, 2016.

22) MP-HPO-98137, "Determination of Cs-137 In Undisturbed Soil At Locations Greater Than 10 Miles From Millstone Site", July 28, 1998.

5-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 APPENDIX A LAND USE CENSUS FOR 2021 A-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 The annual land use census in the vicinity of MPS was conducted as required by the MPS REMODCM. Table A-1 is a list of closest residents in each of twelve over-land compass sectors around Millstone. The list of residents was determined by a survey of properties around Millstone using Google Earth and verified by a field survey. It was assumed that the closest resident was also the closest garden. No changes from the 2019 closest resident list were identified Table A-2 is a list of milk and other foods within ten miles of Millstone. Cow and goat milk producers were identified using the State of Connecticut Agriculture Department list of licensees and using American Dairy Goat Association (ADGA). There were no animals producing milk located within ten miles of Millstone Power Station. As a substitute for milk samples, strontium analysis of air filter and gamma analysis of broadleaf vegetation are being performed on quarterly basis.

Other sources of food were obtained from the Internet at http://www.farmfresh.org by searching for businesses closest to Waterford, CT. A search using Google Earth and field surveys were used to identify additional sources, Figure A-1. No changes from the 2019 sources of food locations were identified.

The 2021 Land Use Census also evaluated aquatic sampling exposure pathways from the fish and shellfish located around MPS. Figure A-2 shows shellfish beds around MPS from the Bureau of Aquaculture of the Department of Agriculture. The saltwater fishing areas are identified in Figure A-3. No changes from the 2019 aquatic sampling exposure pathways were identified.

The dose modeling incorporates the distances listed in Tables A-1, A-2.

A-2

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Table A-1 2021 S urvev Downwind Resident/Garden 1 Direction miles meters N 0.95 1521 NNE 0.53 854 NE 0.47 763 ENE 0.97 1554 E 0.92 1475 ESE 1.06 1701 SE 2 NIA NIA SSE 2 NIA NIA s2 NIA NIA SSW2 NIA NIA SW 2.28 3670 WSW 1.95 3130 w 1.78 2858 WNW 1.51 2423 NW 1.35 2179 NNW 0.51 816 Notes:

1. No gardens located closer than resident.

2. Sectors SE thru SSW are NIA because they are over water.

A-3

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Table A-2 Milk and other foods within Ten miles of Millstone - 2021 Sector Miles Business Location Comments NW 1.95 Smith's Acres Niantic Fruits and vegetables NE 1.96 Mingo Goat Waterford Has goats, not producing milk Has pigs, fed nonlocal sources and ENE 3.0 Secchiaroli Farms Waterford have concrete pens WNW 5.0 Four Mile River Farm Old Lyme Eggs, Meat Scott's Yankee NW 5.2 East Lyme Fruits, vegetables, and cider Farmer Vegetables, Herbs, Eggs, Meat, NNW 5.3 White Gate Farm East Lyme Nursery and Flowers Registered AGDA member but does NNW 6.24 Trinity Farm Waterford not produce any food product N 7.1 F.R.E.S.H Farm Enfield Fruit, Vegetables, Herbs N 7.4 Hunts Brook Farm Quaker Hill Honey, Maple, Vegetables ENE 6.8 Leverett Goat Groton Has goats but not producing milk ENE 7.5 Groton Family Farm Groton Vegetables, Honey, Maple, Eggs, Fiber Fruits, vegetables, cows, goats, and NE 8.3 Red Fence Farm Groton pig. Cows and goats currently not producing milk NW 9.4 Macwilliam Lyme Has goats, does not sell commercially A-4

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Figure A-1 Farms and Goats Products within ten miles of Millstone Legend 0 Agricultural Farms

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Figure A-2 Shellfish Beds in Vicinity of Millstone J,_ 11 .

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 APPENDIX 8

SUMMARY

OF INTERLABORATORY COMPARISONS B-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Summary of Results - Inter-laboratory Comparison Program (ICP)

The TBE Laboratory analyzed Performance Evaluation (PE) samples of air particulate (AP), air iodine, milk, soil, vegetation, and water matrices for various analytes. The PE samples supplied by Analytics Inc., Environmental Resource Associates (ERA) and Department of Energy (DOE) Mixed Analyte Performance Evaluation Program (MAPEP), were evaluated against the following pre-set acceptance criteria:

A. Analytics Evaluation Criteria Analytics' evaluation report provides a ratio of TBE's result and Analytics' known value.

Since flag values are not assigned by Analytics, TBE evaluates the reported ratios based on internal QC requirements based on the DOE MAPEP criteria.

B. ERA Evaluation Criteria ERA's evaluation report provides an acceptance range for control and warning limits with associated flag values. ERA's acceptance limits are established per the US EPA, National Environmental Laboratory Accreditation Conference (NELAC), state-specific Performance Testing (PT) program requirements or ERA's SOP for the Generation of Performance Acceptance Limits, as applicable. The acceptance limits are either determined by a regression equation specific to each analyte or a fixed percentage limit promulgated under the appropriate regulatory document.

C. DOE Evaluation Criteria MAPEP's evaluation report provides an acceptance range with associated flag values.

MAPEP defines three levels of performance:

• Acceptable (flag = "A") - result within +/- 20% of the reference value

• Acceptable with Warning (flag = "W') - result falls in the +/- 20% to +/- 30% of the reference value

• Not Acceptable (flag = "N") - bias is greater than 30% of the reference value Note: The Department of Energy (DOE) Mixed Analyte Performance Evaluation Program (MAPEP) samples are created to mimic conditions found at DOE sites which do not resemble typical environmental samples obtained at commercial nuclear power facilities.

For the TBE laboratory, 146 out of 154 analyses performed met the specified acceptance criteria. Seven analyses did not meet the specified acceptance criteria and were addressed through the TBE Corrective Action Program. NOTE: One analysis (soil for Tc-99) that did not meet acceptance criteria was performed for TBE information and is not on the list of required /GP analyses. A summary is found below:

1. The ERA MRAD March 2021 Water Fe-55 result was evaluated as Not Acceptable. The reported value for Fe-55 was 579 pCi/L and the known result was 275 pCi/L (acceptance range 162 - 400). When reviewing the original sample data, it was found that the carrier yield was 52.6% (lower than typical water samples). Looking at the etched plate that was counted, it appeared that some loss of sample could have occurred. The sample was logged for reanalysis and used as the workgroup duplicate. The results were acceptable at 197 and 221 respectively. Yields were 97.4% and 105.7% and the plated samples were centered with no apparent loss of sample. The loss of sample during plating resulted in a low yield which produced an artificially high sample result. (NCR 21-01)

B-2

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021

2. The MAPEP February 2021 AP Gross Alpha result was evaluated as Not Acceptable. The reported value was 0.371 Sq/sample and the known result was 1.77 Sq/sample (acceptance range 0.53 - 3.01). A similar failure had occurred several years prior due to the filter being placed with the wrong side up on the detector. At that time, a small dot was placed on the top of the filter prior to removal from the package to indicate the correct side for counting. The current sample was still in the detector when the result was received (dot side facing the detector). The sample was recounted with a similar result and was flipped and recounted. The flipped result was 0.661 Sq/sample, within the acceptable range.

Because TBE cannot rely on receiving correct packaging from the provider, MAPEP AP cross-checks will be counted on both sides going forward. NOTE:

The August sample had the same packaging issue (upside down). (NCR 21-02)

3. The MAPEP February 2021 soil Ni-63 was evaluated as Not Acceptable. The reported value was 310 Bq/kg and the known result was 689 (acceptance range 482 - 896). All workgroup QC was reviewed with no anomalies. The analytical procedure had been revised prior to this analysis to eliminate added interferences.

The sample yield was >100%, indicative of incomplete separation from interferences, leading to a lower result. The procedure was again revised after acceptable results were obtained. (NCR 21-03)

4. The ERA October 2021 water Gross Beta result was evaluated as Not Acceptable. The reported value was 63.0 pCi/L and the known was 55.7 (acceptance range 38.1 - 62.6) or 113% of the known. The 2-sigma error was 6.8, placing the reported result well within the acceptable range. All QA was reviewed with no anomalies. A follow-up Quick Response cross-check was analyzed with a 120% ratio (see item 7). (NCR 21-10)

5. The ERA October 2021 water Tritium result was evaluated as Not Acceptable.

The reported value was 13,800 pCi/L and the known was 17,200 (acceptance range 15,000 - 18,900). The 2-sigma error was 1,430, placing the result within the acceptable range. TBE's internal QC acceptance is 70% - 130%, while ERA's for this sample was 87% - 110%. All QA was reviewed with no anomalies. A Quick Response follow-up cross-check was analyzed with a result of 17,500 pCi/L (known 17,800 pCi/L). (NCR 21-11)

6. The MAPEP August 2021 soil Ni-63 result was evaluated as Not Acceptable. The reported value was 546 Bq/kg and the known result was 1,280 Bq/kg (acceptance range 896 - 1,664). All QC was reviewed and no anomalies found. The procedure revision to remove added MAPAP interferences was ineffective for this sample. No client soil matrix samples were analyzed for Ni-63 in 2020 or 2021.

The root cause investigation is still ongoing at this time. (NCR 21-13)

7. The ERA December 2021 Quick Response water Gross Beta result was evaluated as Not Acceptable. The reported value was 47.6 pCi/L and the known was 39.8 pCi/L or 120% of the known (acceptance range of 26.4 -47.3). The 2-sigma error was 6.1, placing the reported result well within the acceptable range.

All QA was reviewed with no anomalies. The original sample was recounted on a different detector with a result of 40.3 +/- 6.27 pCi/L. The "failure" of this sample and the RAD-127 was due to the narrow upper acceptance ranges assigned (119% and 112%) (NCR 21-14)

The Inter-Laboratory Comparison Program provides evidence of "in control" counting systems and methods, and that the laboratories are producing accurate and reliable data.

B-3

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Analytics Environmental Radioactivity Cross Check Program Teled:tne Brown Enaineerina Environmental Services TSE Identification Known Ratio ofTBE to Month/Year Matrix Nuclide Units Reported Evaluation (b)

Number Value (a) Analytics Result Value March 2021 E13466 Milk Sr-89 pCi/L 84.6 87.1 0.97 A Sr-90 pCi/L 11.5 12.6 0.91 A E13467 Milk Ce-141 pCi/L 111 125 0.89 A Co-58 pCi/L 123 128 0.96 A Co-60 pCi/L 140 154 0.91 A Cr-51 pCi/L 252 242 1.04 A Cs-134 pCi/L 130 151 0.86 A Cs-137 pCi/L 110 110 1.00 A Fe-59 pCi/L 105 109 0.96 A 1-131 pCi/L 77.6 86.9 0.89 A Mn-54 pCi/L 111 112 0.99 A Zn-65 pCi/L 200 211 0.95 A E13468 Charcoal 1-131 pCi 83.5 88.5 0.94 A E13469 AP Ce-141 pCi 103.0 103 1.00 A Co-58 pCi 93.3 105 0.89 A Co-60 pCi 136 126 1.08 A Cr-51 pCi 213 198 1.07 A Cs-134 pCi 123.0 124 0.99 A Cs-137 pCi 86.3 90.1 0.96 A Fe-59 pCi 81.3 89.6 0.91 A Mn-54 pCi 93.5 92.0 1.02 A Zn-65 pCi 166 173 0.96 A E13470 Soil Ce-141 pCi/g 0.232 0.262 0.89 A Co-58 pCi/g 0.251 0.268 0.94 A Co-60 pCi/g 0.306 0.322 0.95 A Cr-51 pCi/g 0.517 0.506 1.02 A Cs-134 pCi/g 0.263 0.317 0.83 A Cs-137 pCi/g 0.278 0.301 0.92 A Fe-59 pCi/g 0.228 0.229 1.00 A Mn-54 pCi/g 0.221 0.235 0.94 A Zn-65 pCi/g 0.448 0.441 1.02 A E13471 Sr-89 pCi 92.2 95.5 0.97 A Sr-90 pCi 11.7 13.9 0.84 A (a) The Analytics known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) Analytics evaluation based on TBE internal QC limits:

A= Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning- reported result falls within 0. 70-0.80 or 1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of< 0. 70 and> 1.30 B-4

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TSE Identification Known Ratio ofTBE to Month/Year Matrix Nuclide Units Reported Evaluation (b)

Number Value (a) Analytics Result Value September 2021 E13472 Milk Sr-89 pCi/L 66.4 85.4 0.78 w Sr-90 pCi/L 11.9 14.0 0.85 A E13473 Milk Ce-141 pCi/L 118 114 1.03 A Co-58 pCi/L 116 118 0.98 A Co-60 pCi/L 142 145 0.98 A Cr-51 pCi/L 244 236 1.03 A Cs-134 pCi/L 81 93.1 0.87 A Cs-137 pCi/L 105 112 0.94 A Fe-59 pCi/L 105 102 1.03 A 1-131 pCi/L 65.1 85.6 0.76 w Mn-54 pCi/L 128 128 1.00 A Zn-65 pCi/L 158 153 1.03 A E13474 Charcoal 1-131 pCi 85.2 90.9 0.94 A E13475 AP Ce-141 pCi 126 135 0.94 A Co-58 pCi 148 139 1.07 A Co-60 pCi 183 171 1.07 A Cr-51 pCi 322 278 1.16 A Cs-134 pCi 118 110 1.08 A Cs-137 pCi 147 132 1.12 A Fe-59 pCi 131 120 1.09 A Mn-54 pCi 161 151 1.06 A Zn-65 pCi 202 180 1.12 A E13476 Soil Ce-141 pCi/g 0.215 0.219 0.98 A Co-58 pCi/g 0.208 0.226 0.92 A Co-60 pCi/g 0.277 0.277 1.00 A Cr-51 pCi/g 0.388 0.452 0.86 A Cs-134 pCi/g 0.157 0.178 0.88 A Cs-137 pCi/g 0.270 0.284 0.95 A Fe-59 pCi/g 0.218 0.195 1.12 A Mn-54 pCi/g 0.239 0.246 0.97 A Zn-65 pCi/g 0.312 0.293 1.06 A E13477 Sr-89 pCi 85.6 68.3 1.25 w Sr-90 pCi 12.6 11.2 1.13 A (a) The Analytics known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) Analytics evaluation based on TBE internal QC limits:

A = Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning- reported result falls within 0. 70-0.80 or 1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of< 0. 70 and> 1.30 B-5

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 DOE's Mixed Analyte Performance Evaluation Program (MAPEP)

Teled:t'.ne Brown Engineerin!J Environmental Services TBE Identification Known Acceptance Month/Year Matrix Nuclide Units Reported Evaluation (bl Number Value (a) Range Value February 2021 21-GrF44 AP Gross Alpha Sq/sample 0.371 1.77 0.53 - 3.01 N(3)

Gross Beta Sq/sample 0.731 0.65 0.325 - 0.974 A 21-Ma844 Soil Ni-63 Bq/kg 310 689.0 482 - 896 N\4)

Tc-99 Bq/kg 457 638 447 - 829 w 21-MaSU44 Urine Cs-134 Bq/L 2.34 2.73 1.91 - 3.55 A Cs-137 Bq/L 2.54 2.71 1.90 - 3.52 A Co-57 Bq/L 0.4100 (1) A Co-60 Bq/L 2.24 2.44 1.71 -3.17 A Mn-54 Bq/L 2.03 2.03 1.42 - 2.64 A K-40 Bq/L 52.8 54.0 38-70 A U-234 Bq/L 0.108 0.0877 0.0614-0.114 w U-238 Bq/L 0.101 0.091 0.064-0.118 A Zn-65 Bq/L 1.06 1.34 (2) A 21-MaW44 Water Ni-63 Bq/L 6.7 8.2 5.7 -10.7 A Tc-99 Bq/L 3.850 4.01 2.81 - 5.21 A 21-RdV44 Vegetation Cs-134 Sq/sample 3.13 3.60 2.5 -4.7 A Cs-137 Sq/sample 4.64 4.69 3.28 -6.10 A Co-57 Sq/sample 5.25 5.05 3.54 -6.57 A Co-60 Sq/sample 2.86 2.99 2.09 - 3.89 A Mn-54 Sq/sample 5.02 5.25 3.68 -6.83 A Sr-90 Sq/sample 0.631 0.673 0.471 - 0.875 A Zn-65 Sq/sample -0.233 (1) A August2021 21-GrF45 AP Gross Alpha Sq/sample 0.368 0.960 0.288 - 1.632 A Gross Beta Sq/sample 0.595 0.553 0.277 - 0.830 A 21-Ma845 Soil Ni-63 Bq/kg 546 1280 896 -1664 N(b)

Tc-99 Bq/kg 453 777 544 -1010 N(b) 21-MaSU45 Urine Cs-134 Bq/L 3.10 3.62 2.53 - 4.71 A Cs-137 Bq/L 0.083 (1) A Co-57 Bq/L 0.844 0.87 0.606-1.125 A Co-60 Bq/L 0.0535 (1) A Mn-54 Bq/L 0.459 0.417 (2) A K-40 Bq/L 48.8 54.0 38-70 A U-234 Bq/L 0.133 0.116 0.081 -0.151 A U-238 Bq/L 0.137 0.121 0.085-0.157 A Zn-65 Bq/L 0.339 0.420 (2) A 21-MaW45 Water Ni-63 Bq/L 33.5 39.5 27.7 - 51.4 A Tc-99 Bq/L 3.5 3.7 2.60 - 4.82 A 21-RdV45 Vegetation Cs-134 Sq/sample 3.42 4.34 3.04 - 5.64 w Cs-137 Sq/sample 2.14 2.21 1.55 -2.87 A Co-57 Sq/sample 4.08 4.66 3.26 - 6.06 A Co-60 Sq/sample 2.81 3.51 2.46 - 4.56 A Mn-54 Sq/sample 0.035 (1) A Sr-90 Sq/sample 1.15 1.320 0.92 - 1.72 A Zn-65 Sq/sample 2.05 2.43 1.70 - 3.16 A (a) The MA PEP known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measure mi made during standard preparation (b) DOEIMAPEPevaluation:

A = Acceptable - reported result falls within ratio limits of o. 80- 1. 20 W=Acceptable with warning- reported result falls within o. 70-0.80 or1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of< o. 70 and> 1.30 (1) False positive test (2) Sensitivity evaluation (3)See NCR 21-02 (4) See NCR 21- 03 (5) See NCR 21- 13 (6) Tc-99 cross-checks done for TBE information only- not required B-6

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 ERA Environmental Radioactivity Cross Check Program Teledyne Brown Engineering EnvironmentalServices TBE Identification Known Acceptance Month/Year Matrix Nuclide Units Reported Evaluation (b)

Number Value<a) Lim its Value March 2021 MRAD-34 Water Am-241 pCi/L 175 157 108-201 A Fe-55 pCi/L 579 275 162 - 400 N<1>

Pu-238 pCi/L 181 171 103 -222 A Pu-239 pCi/L 153 142 87.9 -175 A Soil Sr-90 pCi/kg 6570 9190 2860 - 14,300 A AP Fe-55 pCi/filter 107 121 44.2-193 A U-234 pCi/filter 25.99 25.5 18.9 -29.9 A U-238 pCi/filter 24.7 25.3 19.1 -30.2 A April 2021 RAD-125 Water Ba-133 pCi/L 92.3 90.5 76.2 - 99.6 A Cs-134 pCi/L 62.9 70.5 57.5 - 77.6 A Cs-137 pCi/L 161 168 151 -187 A Co-60 pCi/L 22.5 20.9 17.7-25.8 A Zn-65 pCi/L 183 177.0 159 -208 A GR-A pCi/L 30.8 30.2 15.4 - 39.4 A GR-B pCi/L 60.1 67.5 46.8 - 74.2 A LI-Nat pCi/L 36.45 36.9 30.0 -40.8 A H-3 pCi/L 13,400 14,600 12,800 - 16,100 A Sr-89 pCi/L 64.5 63.5 51.4-71.5 A Sr-90 pCi/L 22.8 23.0 16.5 - 27.0 A 1-131 pCi/L 28.2 26.7 22.2 - 31.4 A September 2021 MRAD-35 Water Am-241 pCi/L 68 63.7 43.7-81.5 A Fe-55 pCi/L 179 246 145 - 358 A Pu-238 pCi/L 102 114 68.5-148 A Pu-239 pCi/L 32 34.3 21.2 - 42.3 A Soil Sr-90 pCi/kg 6160 6090 1,900 - 9,490 A AP Fe-55 pCi/filter 493 548 200 - 874 A Pu-238 pCi/filter 28 28.5 21.5 - 35.0 A Pu-239 pCi/filter 21 21.6 16.1 - 26.1 A U-234 pCi/filter 7.95 7.76 5.75 - 9.09 A U-238 pCi/filter 8.0 7.69 5.81 -9.17 A October2021 RAD-127 Water Ba-133 pCi/L 82.8 87.5 73.6 - 96.2 A Cs-134 pCi/L 64.0 70.1 57.1 - 77.1 A Cs-137 pCi/L 145 156 140-174 A Co-60 pCi/L 83.2 85.9 77.3 - 96.8 A Zn-65 pCi/L 133 145 130-171 A GR-A pCi/L 76.0 66.7 35.0 - 82.5 A GR-B pCi/L 63.0 55.7 38.1 -62.6 N<2>

LI-Nat pCi/L 52.88 55.5 45.3-61.1 A H-3 pCi/L 13,800 17,200 15,000 - 18,900 N(3J Sr-89 pCi/L 54.9 61.0 49.1 - 68.9 A Sr-90 pCi/L 24.8 29.3 21.3-34.0 A 1-131 pCi/L 27.4 26.4 21.9-31.1 A December 2021 QR 120121Y Water GR-B pCi/L 47.6 39.8 26.4 - 47.3 N<4>

H-3 pCi/L 17,500 17,800 15,600 - 19,600 A (a) The ERA knovvn value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation.

(b) ERA evaluation:

A = Acceptable - Reported value falls within the Acceptance Limits N = Not Acceptable - Reported value falls outside of the Acceptance Limits (1) See NCR 21-01 (2) See NCR 21-10 (3) See NCR 21-11 (4) See NCR 21-14 B-7

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 APPENDIX C ERRATUM C-1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2021 Erratum- Correction to Previously Published Annual Radiological Environmental Operating Report In the 2021 Annual Radiological Environmental Operating Report there were no correction identified to previously published Annual Radiological Environmental Operating Reports.

C-2