ML21110A155

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2020 Annual Radiological Environmental Operating Report
ML21110A155
Person / Time
Site: Millstone  Dominion icon.png
Issue date: 04/19/2021
From: Armstrong L
Dominion Energy Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
21-122
Download: ML21110A155 (90)


Text

Dominion Energy Nuclear Connecticut, Inc.

Millstone Power Station 314 Rope Ferry Road, Waterford, CT 06385 Dominion Energy.com U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 APR 1 9 2021 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNITS 1, 2, AND 3 n Dominion

=

a,, Energy Serial No.

MPS Lie/LO Docket Nos.

License Nos.21-122 RO 50-245 50-336 50-423 DPR-21 DPR-65 NPF-49 2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT This letter transmits the Annual Radiological Environmental Operating Report for the Millstone Power Station, for the period January 1, 2020 through December 31, 2020.

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. Jeffry A. Langan at (860) 444-5544.

Sincerely,

~~

L. J. Armstrong Director, Nuclear Station Safety and Licensing

Serial No.21-122 2020 Annual Radiological Environmental Operating Report Page 2 of 4 Attachments:

1 Commitments made in this letter:

1. None.

cc:

U. S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 T. Carter NRC Project Manager Millstone Unit 1 U.S. Nuclear Regulatory Commission Two White Flint North, Mail Stop 5-A10 11545 Rockville Pike Rockville, MD 20852-2738 L. A. Kauffman NRC Inspector U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 S. L. Wilson NRC Inspector U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman NRC 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 NRC Senior Resident Inspector Millstone Power Station

Serial No.21-122 2020 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. Foikwein American Nuclear Insurers 95 Glastonbury Blvd.

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

Serial No.21-122 2020 Annual Radiological Environmental Operating Report Page 4 of 4 R. Brule First Selectman Town of Waterford Waterford Town Hall Waterford, CT 06385 M. C. Nickerson 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.21-122 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 ATTACHMENT 1 2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MILLSTONE POWER STATION UNITS 1, 2, AND 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DENC)

Millstone Power Station 2020 Radiological Environmental Operating Report January 1, 2020 - December 31, 2020 Dominion Energy Nuclear Connecticut, Inc.

Unit License Docket 1

DPR-21 50-245 2

DPR-65 50-336 3

NPF-49 50-423 ii ;, Dominion pi, Energy

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 MILLSTONE POWER STATION RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM 2020 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 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020

~ 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 4.10 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 2020...................................................... A-1 APPENDIX B -

SUMMARY

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

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 i

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 to December 31, 2020. 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 2020, there were 529 samples collected from the atmospheric, aquatic, and terrestrial environments. In addition, 172 exposure measurements were obtained using environmental thermoluminescent 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 2020 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 2020 ii 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 39 - 100 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 2020, 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 2020 was approximately 0.226 mrem for the year. This conservative estimate is well below the Environmental Protection Agencys (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 2020 REMP for MPS resulted in the collection and analysis of 701 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 Millstones operation. The 2020 REMP samples results are consistent with previous years with no trends evident.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 11

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 2020 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 Millstones 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 to December 31, 2020.

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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 12

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 1980s 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 shows the sources and doses of radiation from natural and man-made sources.

Table 1.3-1 Radiation Sources and Corresponding Approximate Doses(1)

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

Source Radiation Dose (mrem/year)

Internal, inhalation(2) 228 Medical(3) 300 External, space 33 Consumer(4) 13 Internal, ingestion 29 Industrial, security, educational, research 0.3 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)

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 13 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-7 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 shutdown, 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 2020, with the exception of the MPS2 refueling outage in May, the MPS3 down-power event in April, and MPS3 refueling outage in October. For 2020, the annual capacity factor for MPS2 was 87.6% and for MPS3 was 84.9%.

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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 14

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 (I-131), xenon-133 (Xe-133), and cesium-137 (Cs-137).

Figure 1.4-1: SIMPLIFIED DIAGRAM OF A PRESSURIZED WATER REACTOR

Pressuri :.:ed water reactor-a common type of Light Water Reactor

~

EAM GENER

~

(LWR)


co,INIDENS ER COOILJNG WATER

-,TAK!IINIG WASTE MEAT TOTI-IE E'INIV1IRONHElHT

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 15 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.

Figure 1.4-2: Radioactive Fission Product Formation Uranium Neutrons Radiation Neutron._.

Fission Products uranium

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 16 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).

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).

0 Neutron collision with Co-59 Stable Cobalt Nucleus Co-60 Radioactive Cobalt Nucleus

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 17 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 Millstones 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 18

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.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 19 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.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 110 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 MPSs 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 111

EXAMPLES OF Millstones RADIATION EXPOSURE PATHWAYS Figure 1.6-1: Radiation Exposure Pathways

LIQUID EFFLUENTS DIRECT RADIATION IL DEPOSITION)

1. SHORELINE DIRECT RADIATION (FISHING, PICNIC.ING) ~
2. DIRECT RADIATION (IMMERSION IN OCEAN, (OAT;, SWIMMING)
3. DIRECT RADIATION (STATION),

2 AIR INHALATION c/ 1. DIRECT RADIATION (AIR SUBMERSION)

  • t c/
5. CONSUMPTION (VEGETATION)

~

t DEPOSITION

(/

DEPOSITION

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 112

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 salt water 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 NRC-recommended models that tend to result in over-estimates of the resulting dose. These computerized dose calculations are performed by DENC personnel. These computer codes use the guidelines and methodology set forth by the NRC in Regulatory Guide 1.109 (Reference 7).

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

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.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 113 After dose calculations are performed, the results are compared to the dose limits for the public as specified in NRCs 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 21

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.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 22 Table 2.1-1 Environmental Monitoring Program Sampling Types and Locations No.-

Type*

Location Name

Distance, Direction From Release Point**

Sample Media 1-I Onsite - NAP Parking Lot N 0.6 Mi, NNW TLD, Air Particulate, Iodine, Vegetation 2-I Onsite - Weather Shack 0.3 Mi, S TLD, Air Particulate, Iodine 3-I Onsite - Bird Sanctuary 0.3 Mi, NE TLD, Air Particulate, Iodine, Soil 4-I Onsite - Albacore Drive 1.0 Mi, N TLD, Air Particulate, Iodine, Soil 5-I Onsite - Quarry East 0.1 Mi, SSE TLD 6-I Onsite - Quarry Discharge 0.3 Mi, SSE TLD 7-I Onsite - Env. Lab Dock 0.3 Mi, SE TLD 8-I Onsite - Env. Lab 0.3 Mi, SE TLD 9-I Onsite - Bay Point Beach 0.4 Mi, W TLD 10-I Goshen Fire Dept.

1.2 Mi, E TLD, Air Particulate, Iodine, Vegetation 11-I 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.

8.8 Mi, W TLD 17-I Site Boundary 0.5 Mi, NE Vegetation 25-I Fruits & Vegetables

< 10 Miles Vegetation 26-C Fruits & Vegetables

> 10 Miles Vegetation 27-I East Lyme Police Dept.

1.7 Mi, WNW TLD, Air Particulate, Iodine 28-I Two Tree Island 1 0.8 Mi, SSE Fish1 29-I West Jordan Cove 1 0.5 Mi, ENE to ESE Clams, Fucus, Fish1 31-I Niantic Shoals 1.8 Mi, NW Bottom Sediment, Clams 32-I Vicinity of Discharge 1,2 Bottom Sediment, Fish1, Seawater, Aquatic Flora 33-I Seaside Point 1.8 Mi, ESE Bottom Sediment 34-I Thames River Yacht Club 4.0 Mi, ENE Bottom Sediment 35-I Niantic Bay 0.5 Mi, SSW to W Lobster, Fish1, Aquatic Flora 36-C Black Point 2.7 Mi, WSW Aquatic Flora 37-C Giant's Neck 3.5 Mi, WSW Bottom Sediment, Seawater 41-I Waterford - Myrock Avenue 3.2 Mi, ENE TLD 42-I East Lyme - Billow Road 2.4 Mi, WSW TLD 43-I East Lyme-Old Black Point 2.6 Mi, SW TLD 44-I Onsite - Schoolhouse 0.1 Mi, NNE TLD 45-I Onsite - Access Road #1 0.5 Mi, NNW TLD 46-I Old Lyme - Hillcrest Ave.

4.6 Mi, WSW TLD 47-I East Lyme - W. Main St.

4.5 Mi, W TLD 48-I East Lyme - Corey & Roxbury 3.4 Mi, WNW TLD 49-I East Lyme - Society Rd.

3.6 Mi, NW TLD 50-I East Lyme - Manwaring Rd &

Terrace Ave 2.1 Mi, W TLD 51-I East Lyme - Smith Ave.

1.5 Mi, NW TLD 52-I Waterford - River Rd.

1.1 Mi, NNW TLD 53-I Waterford - Gardiners Wood Rd 1.4 Mi, NNE TLD 55-I Waterford - Magonk Point 1.8 Mi, ESE TLD 56-I New London - Ocean & Mott Ave.

3.7 Mi, E TLD

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.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 23 Table 2.1-1 Environmental Monitoring Program Sampling Types and Locations (Continues)

No.-

Type1 Location Name Distance, Direction From Release Point2 Sample Media 57-I New London - Ocean Ave.

3.6 Mi, ENE TLD 59-I Waterford -Miner Ave.

3.4 Mi, NNE TLD 60-I Waterford-Parkway South&Cross 4.0 Mi, N TLD 61-I Waterford-Oil Mill&Boston Post 4.3 Mi, NNW TLD 62-I East Lyme - Columbus Ave.

1.9 Mi, WNW TLD 63-I Waterford - Gardiners Wood &

Jordon Cove 0.8 Mi, NE TLD 64-I Waterford - Shore Rd.

1.1 Mi, ENE TLD 65-I Waterford - Boston Post Rd.

3.2 Mi, NE TLD 66-X NAP Parking Lot - Fit Center 0.4 Mi, NW TLD 71-I 1-MW-XFMR-03 Onsite Well Water 72-I MW-GPI-1 Onsite Well Water 73-X Site Switchyard Fence 0.3 Mi, N TLD 74-X Ball Field Foul Pole 0.6 Mi, N TLD 75-X Waterford - Windward Way &

0.5 Mi, NE TLD Shotgun 76-X ISFSI-1 Up-gradient of ISFSI Well Water 77-X ISFSI-2 Down-gradient of ISFSI Well Water 78-X ISFSI-3 Down-gradient of ISFSI Well Water 79-I M3-MW-1 Onsite Well Water 81-I S2-MW-1 Onsite Well Water 82-I MW-6B Onsite Well Water 83-I 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.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 24 Table 2.1-2 Required Sampling Frequency & Type of Analysis Exposure Pathway and/or Sample No. of Locations Sampling & Collection Frequency Type of Analysis

1.

Gamma Dose -

Environmental TLD 391 Quarterly Gamma Dose - Quarterly

2.

Airborne Particulate 8

Continuous sampler - filter change every two weeks Gross Beta - Every two 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 stations gross beta results

3.

Airborne Iodine 8

Continuous sampler - canister change every two weeks I-131 - Every two weeks

4.

Vegetation 5

One sample near middle and one near end of growing season Gamma Isotopic on each sample

5.

Reserved

6.

Sea Water 2

Continuous sampler with a monthly collection at indicator location.

Quarterly at control location -

Composite of 6

weekly grab l

Gamma Isotopic and Tritium on each sample.

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 (edible portion) 2 Semiannual Gamma Isotopic on each sample

11.

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

13.

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

14.

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

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

Oysters were previously Sample#12, REMODCM revision 27.

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 25 Figure 2.1-1, Inner TLD, Air, Grass, Soil, and Aquatic Locations

Dominion Energy Nuclear Connecticut, Inc.

Annual Radiological Environmental Millstone Power Station Operating Report 2020 26 Figure 2.1-2, Outer TLD and Aquatic Locations

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 27

2.2 Samples Collected During Report Period The following table summarizes the number of samples of each type collected and analyzed during 2020:

Table 2.2-1 REMP Samples Collected in 2020 Sample Type Number of Technical Specification Required Samples Number of Technical Specification Required Samples Analyzed Number of Extra Samples Analyzed Gamma Exposure (Environmental TLD) 156 156 16 Air Particulates 208 208 0

Air Iodine 208 208 0

Soil 3

3 0

Milk (cow)

Milk (goat) 0 0

0 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 50 2.3 Required Samples Not Collected During the Report Period During 2020 all required samples were obtained as listed in Table 2.2-1.

Prior to 2018, milk sampling was performed as an extra sample. The 2020 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 31

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 I.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 Energys (DOE)

Mixed Analyte Performance Evaluation Program (MAPEP).

The Teledyne inter-laboratory comparison report concluded that 126 out of 133 quality assurance analyses performed met the specified acceptance criteria. Seven 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 32

RADIOLOGICAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2020 Medium or Indicator Control Pathw ay Locations Location w ith Highest Mean Locations Sampled Analysis Total LLD*

Number Number (Units)

Type Number Mean Location Distance Number Mean (Range)

Number Direction Mean (Range)

(Range)

Direct Gamma 172 NA 156 9

0.04 Mi.

4 16 Radiation Dose 7.8 W

11.3 7.9 TLD (uR/hr)

(4.4-11.5)

(10.7-11.5)

(5.7-9.4)

Air Iodine I-131 208 0.07 182 NA NA

<LLD 26

( pCi/m 3)

<LLD

<LLD Air Particulate GR-B 208 0.01 182 11 1.6 Mi.

26 26

( pCi/m 3) 0.012 ENE 0.012 0.013 (0.006-0.023)

(0.007-0.023)

(0.006-0.021)

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 04 1.0 Mi.

4 4

0.1137 N

0.1202 0.1014 (0.0881-0.1448)

(0.0986-0.1448)

(0.0831-0.1080)

Other Note 2

<LLD NA NA

<LLD

<LLD Gammas Soil GAMMA 3

(pCi/g dry)

K-40 NA 2

14 12.0 Mi.

1 1

16.070 NE 17 17 (15.470-16.670)

(<LLD-17.000)

(<LLD-17.000)

CS-137 0.18 1/2 4

1.0 Mi.

1 1

0.333 N

0.333 0.283

(<LLD-0.333)

(<LLD-0.333)

(<LLD-0.283)

Ac-228 NA 2

4 1.0 Mi.

1

<LLD 0.880 N

1.132 (0.628-1.132)

(<LLD-1.132)

Other Note 3

<LLD NA NA

<LLD

<LLD Gammas Cow Milk SR-89 10 (pCi/l)

SR-90 2

GAMMA Milk w as not available for collection in 2020, as a substitute, K-40 NA Strontium Analysis of Air Particulate filters and Gamma Analysis of Broadleaf Vegetation w ere performed.

Other Note 4 Gammas I

I I I I

I

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 33

RADIOLOGICAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2020 Medium or Indicator Control Pathw ay Locations Location w ith Highest Mean Locations Sampled Analysis Total LLD*

Number Number (Units)

Type Number Mean Location Distance Number Mean (Range)

Number Direction Mean (Range)

(Range)

Goat Milk SR-89 10 (pCi/l)

SR-90 2

GAMMA Milk w as not available for collection in 2020, as a substitute, K-40 NA Strontium Analysis of Air Particulate filters and Gamma Analysis of Broadleaf Vegetation w ere performed.

Other Note 4 Gammas Well Water H-3 36 2000 36 NA NA

<LLD NA (pCi/l)

<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

(pCi/g wet)

Be-7 NA 4

NA NA

<LLD 4

<LLD

<LLD K-40 NA 4

25 Within 10 Miles 4

4 2.841 2.841 1.375 (1.009-7.242)

(1.009-7.242)

(0.469-2.256)

Other Note 6

<LLD NA NA

<LLD

<LLD Gammas Broad Leaf Vegetation GAMMA 8

(pCi/g wet)

BE-7 NA 6

1 0.6 Mi.

2 2

1.528 NNW 2.149 1.478 (0.487-3.128)

(1.169-3.128)

(0.718-2.239)

K-40 NA 6

1 0.6 Mi.

2 2

3.268 NNW 3.745 3.610 (2.232-4.129)

(3.560-3.929)

(3.271-3.948)

Ac-228 NA 1/6 17 0.5 Mi.

1/2 2

0.366 NE 0.366

<LLD

(<LLD-0.366)

(<LLD-0.366)

Other Note 7

<LLD NA NA

<LLD

<LLD Gammas I I I I I I

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 34

RADIOLOGICAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2020 Medium or Indicator Control Pathw ay Locations Location w ith Highest Mean Locations Sampled Analysis Total LLD*

Number Number (Units)

Type Number Mean Location Distance Number Mean (Range)

Number Direction Mean (Range)

(Range)

Sea Water H-3 16 3000 8/12 32

< 0.1 Mi 8/12 4

(pCi/l) 1561 1561

<LLD (605-3300)

(605-3300)

GAMMA 16 K-40 NA 12 32

< 0.1 Mi 12 4

253 253 243 (170-323)

(170-323)

(199-288)

Other Note 5

<LLD NA NA

<LLD

<LLD Gammas Bottom Sediment GAMMA 10 (pCi/g dry)

K-40 NA 8

32

< 0.1 Mi 2

2 15.53 17.47 14.37 (12.35-20.15)

(14.78-20.15)

(13.86-14.91)

Ac-228 3/8 31 1.8 Mi.

2 2

1.267 NW 1.410

<LLD (0.982-1.821)

(0.999-1.821)

Other Note 3

<LLD NA NA

<LLD

<LLD Gammas Aquatic Flora GAMMA 16 (pCi/g wet)

BE-7 NA 12 36 2.7 Mi.

1/4 1/4

<LLD WSW 0.2417 0.2417

(<LLD-0.2417)

(<LLD-0.2417)

K-40 NA 12 32

< 0.1 Mi 4

4 6.8593 7.5333 6.5610 (4.3730-8.9230)

(5.3750-8.9230)

(4.8780-7.3190)

I-131 0.06 12 NA NA

<LLD 4

<LLD

<LLD Other Note 6

<LLD NA NA

<LLD

<LLD Gammas I

I I I I

I

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 35

RADIOLOGICAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2020 Medium or Indicator Control Pathw ay Locations Location w ith Highest Mean Locations Sampled Analysis Total LLD*

Number Number (Units)

Type Number Mean Location Distance Number Mean (Range)

Number Direction Mean (Range)

(Range)

Fish - Other GAMMA 4

(pCi/g wet)

K-40 NA 4

29 0.5 Mi.

2 3.227 ENE to ESE 3.601 NA (2.838-3.694)

(3.507-3.694)

Other Note 9

<LLD NA NA

<LLD NA Gammas Oysters GAMMA 4

(pCi/g wet)

K-40 NA 2

31 1.8 Mi.

2 2

1.905 NW 1.905 1.771 (1.512-2.297)

(1.512-2.297)

(1.633-1.908)

Other Note 9

<LLD NA NA

<LLD

<LLD Gammas Clams GAMMA 4

(pCi/g wet)

K-40 NA 4

31 1.8 Mi.

2 2.118 NW 2.146 NA (1.805-2.431)

(2.087-2.204)

Other Note 9

<LLD NA NA

<LLD NA Gammas Lobster GAMMA 4

(pCi/g wet)

K-40 NA 2

35 0.5 Mi.

2 2

2.996 SSW to W 2.996 2.471 (2.861-3.131)

(2.861-3.131)

(1.984-2.958)

Other Note 9

<LLD NA NA

<LLD

<LLD Gammas I

I I I I

I

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 36

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/l for I-131, 15 pCi/l for Cs-134, 18 pCi/l for Cs-137, 70 pCi/l for Ba-140 and 25 pCi/l for La-140.

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

6 - LLDs for fruits & vegetables, broadleaf vegetation and aquatic flora for gamma are 0.06 pCi/M3 for I-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 I-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; and 0.15 pCi/g for Cs-137.

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):

t)

(-

Y 2.22 V

E S

4.66

=

LLD b

exp 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 transformation per minute per picoCurie Y

is the fractional radiochemical yield (when applicable) 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 37

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 2 error (i.e., the measured value exceeds 3).

The reported error is two times the standard deviation (2) 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 I-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

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38

LOCATIONS PERIOD

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1Q 8.2 0.3 11.3 0.5 7.7 0.4 8.3 0.3 9.3 0.4 9.1 0.5 5.3 0.2 11.2 0.6 11.5 0.5 9.9 0.5 7.0 0.3 2Q 7.4 0.3 10.5 0.4 7.1 0.2 7.8 0.2 9.1 0.3 8.2 0.2 4.4 0.3 10.6 0.4 10.7 0.5 9.4 0.4 6.8 0.3 3Q 8.1 0.4 11.1 0.3 7.5 0.2 8.5 0.3 10.0 0.3 8.7 0.4 4.9 0.2 11.4 0.3 11.5 0.7 10.0 0.3 7.0 0.3 4Q 7.9 0.5 10.9 0.5 7.3 0.3 8.4 0.4 9.9 0.4 8.7 0.5 5.1 0.2 11.4 0.4 11.4 0.5 9.8 0.4 7.1 0.4 PERIOD

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1Q 9.3 0.4 9.3 0.4 7.5 0.3 6.2 0.4 7.6 0.3 7.2 0.3 7.2 0.3 7.2 0.3 7.9 0.4 7.1 0.3 8.5 0.4 2Q 8.4 0.3 8.8 0.4 7.3 0.2 5.7 0.2 7.1 0.2 6.9 0.3 7.0 0.3 6.9 0.2 7.6 0.2 6.7 0.2 8.4 0.3 3Q 8.9 0.3 9.4 0.4 7.9 0.2 6.3 0.2 7.4 0.2 7.4 0.2 7.7 0.4 7.2 0.2 8.2 0.3 7.3 0.3 8.9 0.3 4Q 9.0 0.4 8.6 0.4 7.6 0.3 6.0 0.6 7.5 0.4 6.9 0.3 7.2 0.4 7.5 0.4 8.0 0.4 7.3 0.3 8.2 0.3 PERIOD

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1Q 7.5 0.3 9.0 0.3 7.7 0.4 7.6 0.3 6.6 0.3 7.4 0.3 7.2 0.3 7.2 0.4 6.9 0.3 7.0 0.4 7.7 0.4 2Q 7.4 0.2 8.7 0.3 7.4 0.3 7.3 0.3 6.2 0.3 6.8 0.4 7.0 0.3 7.0 0.2 6.8 0.2 6.6 0.2 7.2 0.2 3Q 8.0 0.2 9.3 0.4 7.9 0.2 7.8 0.3 7.1 0.4 7.1 0.3 7.4 0.3 7.4 0.3 6.9 0.2 7.1 0.2 8.1 0.2 4Q 8.0 0.4 8.8 0.4 7.7 0.3 7.6 0.4 6.7 0.5 7.3 0.4 7.1 0.3 7.5 0.3 7.2 0.3 6.8 0.4 7.6 0.3 PERIOD

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1Q 6.0 0.2 6.4 0.3 7.9 0.3 8.0 0.4 7.1 0.3 7.8 0.5 7.8 0.4 7.2 0.5 7.6 0.3 6.5 0.3 2Q 6.1 0.4 6.1 0.3 8.3 0.3 7.6 0.5 7.2 0.2 7.5 0.3 7.3 0.2 6.9 0.3 7.4 0.3 6.6 0.3 3Q 6.7 0.2 6.7 0.2 9.5 0.4 8.9 0.4 7.8 0.3 8.5 0.3 7.6 0.2 7.0 0.3 7.8 0.3 7.0 0.2 4Q 6.5 0.4 6.3 0.5 9.2 0.5 8.4 0.4 7.5 0.4 8.1 0.4 7.1 0.3 6.8 0.3 7.5 0.5 6.6 0.4

  • READINGS ARE THE AVERAGE OF MULTI CaSo4(Tm) PHOSPHOR ELEMENTS WITHIN ONE PANASONIC TLD BADGE ERRORS ARE TWO SIGMA AND INCLUDE COUNTING, TRANSIT, READER AND FADE UNCERTAINTIES C= Control location, Background location 65 66 73 74 75 60 61 62 63 64 46 47 48 49 50 51 52 53 55 56 57 59 41 42 43 44 45 13C 14C 15C 16C 27 TABLE 1 QUARTERLY GAMMA EXPOSURE RATE

(µR/hr)*

1 2

3 4

5 6

7 8

9 10 11

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39

PERIOD ENDING 1

2 3

4 10 11 27 15C

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

01/07/20 0.014 0.002 0.015 0.002 0.014 0.002 0.014 0.002 0.013 0.002 0.014 0.002 0.013 0.002 0.013 0.002 01/21/20 0.010 0.002 0.010 0.002 0.009 0.002 0.012 0.002 0.010 0.002 0.010 0.002 0.009 0.002 0.010 0.002 02/04/20 0.013 0.002 0.012 0.002 0.011 0.002 0.013 0.002 0.010 0.002 0.011 0.002 0.012 0.002 0.012 0.002 02/18/20 0.012 0.002 0.010 0.002 0.011 0.002 0.012 0.002 0.012 0.002 0.011 0.002 0.011 0.002 0.011 0.002 03/03/20 0.014 0.002 0.013 0.002 0.015 0.002 0.015 0.002 0.016 0.002 0.015 0.002 0.016 0.002 0.015 0.002 03/17/20 0.012 0.002 0.011 0.002 0.012 0.002 0.010 0.002 0.010 0.002 0.011 0.002 0.012 0.002 0.011 0.002 03/31/20 0.007 0.001 0.008 0.002 0.008 0.001 0.006 0.001 0.006 0.001 0.008 0.002 0.006 0.002 0.006 0.001 04/14/20 0.012 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.010 0.002 0.011 0.002 0.009 0.002 04/28/20 0.014 0.002 0.015 0.002 0.014 0.002 0.014 0.002 0.015 0.002 0.016 0.002 0.014 0.002 0.013 0.002 05/12/20 0.007 0.002 0.007 0.002 0.008 0.002 0.008 0.002 0.007 0.002 0.009 0.002 0.007 0.002 0.007 0.002 05/26/20 0.008 0.002 0.007 0.001 0.008 0.002 0.007 0.002 0.008 0.002 0.007 0.002 0.008 0.002 0.009 0.002 06/09/20 0.010 0.002 0.009 0.002 0.010 0.002 0.010 0.002 0.010 0.002 0.012 0.002 0.009 0.002 0.010 0.002 06/23/20 0.009 0.002 0.009 0.002 0.008 0.002 0.010 0.002 0.010 0.002 0.010 0.002 0.009 0.002 0.012 0.002 07/07/20 0.014 0.002 0.014 0.002 0.014 0.002 0.013 0.002 0.012 0.002 0.012 0.002 0.015 0.002 0.014 0.002 07/21/20 0.011 0.002 0.012 0.002 0.011 0.002 0.011 0.002 0.011 0.002 0.012 0.002 0.010 0.002 0.011 0.002 08/04/20 0.017 0.002 0.017 0.002 0.015 0.002 0.016 0.002 0.016 0.002 0.016 0.002 0.019 0.002 0.018 0.003 08/19/20 0.015 0.002 0.013 0.002 0.018 0.002 0.016 0.002 0.018 0.002 0.015 0.002 0.016 0.002 0.018 0.002 09/01/20 0.015 0.002 0.015 0.002 0.015 0.002 0.017 0.002 0.016 0.002 0.015 0.002 0.015 0.002 0.015 0.002 09/15/20 0.013 0.002 0.015 0.002 0.011 0.002 0.013 0.002 0.012 0.002 0.012 0.002 0.011 0.002 0.012 0.002 09/29/20 0.022 0.002 0.021 0.002 0.020 0.003 0.019 0.003 0.019 0.002 0.023 0.002 0.021 0.002 0.021 0.002 10/13/20 0.012 0.002 0.011 0.002 0.012 0.002 0.012 0.002 0.011 0.002 0.014 0.002 0.011 0.002 0.014 0.002 10/27/20 0.010 0.002 0.012 0.002 0.013 0.002 0.011 0.002 0.012 0.002 0.013 0.002 0.012 0.002 0.013 0.002 11/10/20 0.021 0.002 0.021 0.002 0.021 0.002 0.019 0.002 0.020 0.002 0.022 0.003 0.021 0.003 0.021 0.002 11/24/20 0.015 0.002 0.015 0.002 0.015 0.002 0.014 0.002 0.015 0.002 0.015 0.002 0.016 0.002 0.013 0.002 12/08/20 0.010 0.002 0.012 0.002 0.012 0.002 0.011 0.002 0.011 0.002 0.012 0.002 0.011 0.002 0.010 0.002 12/22/20 0.012 0.002 0.013 0.002 0.014 0.002 0.014 0.002 0.013 0.002 0.015 0.002 0.013 0.002 0.013 0.002 01/05/21 0.011 0.002 0.010 0.002 0.008 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.010 0.002 C= Control location, Background location TABLE 2 AIR PARTICULATES GROSS BETA RADIOACTIVITY (pCi/m3)

LOCATIONS

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PERIOD ENDING 1

2 3

4 10 11 27 15C

(+/)

(+/)

(+/)

(+/)

(+/)

(+/)

(+/)

(+/)

01/07/20

-0.007 0.008

-0.006 0.007

-0.006 0.007

-0.007 0.008

-0.007 0.008 0.000 0.013 0.000 0.006 0.001 0.013 01/21/20

-0.001 0.016

-0.001 0.017

-0.001 0.006

-0.001 0.016 0.001 0.009 0.001 0.008 0.001 0.010 0.001 0.009 02/04/20 0.006 0.010 0.006 0.011 0.003 0.005 0.006 0.010 0.006 0.011 0.008 0.016 0.009 0.018 0.008 0.016 02/18/20 0.002 0.012 0.002 0.013 0.002 0.011 0.002 0.012 0.003 0.010 0.003 0.009 0.003 0.010 0.003 0.009 03/03/20 0.002 0.005 0.001 0.004 0.001 0.004 0.002 0.005 0.002 0.005

-0.003 0.013

-0.001 0.006

-0.003 0.014 03/17/20 0.003 0.015 0.003 0.016 0.003 0.013 0.003 0.016 0.003 0.012 0.002 0.009 0.003 0.013 0.003 0.011 03/31/20

-0.012 0.014

-0.013 0.015

-0.011 0.012

-0.013 0.015 0.003 0.015 0.003 0.014 0.003 0.017 0.003 0.015 04/14/20

-0.014 0.016

-0.016 0.018

-0.013 0.015

-0.015 0.017

-0.001 0.010

-0.001 0.009

-0.001 0.011

-0.001 0.010 04/28/20 0.000 0.010 0.000 0.010 0.000 0.009 0.000 0.011 0.005 0.011 0.004 0.010 0.005 0.011 0.005 0.011 05/12/20 0.000 0.017 0.000 0.017 0.000 0.016 0.000 0.018

-0.007 0.011

-0.006 0.010

-0.006 0.010

-0.007 0.011 05/26/20 0.002 0.017 0.002 0.015 0.002 0.015 0.003 0.018 0.000 0.011 0.000 0.010 0.000 0.009 0.000 0.010 06/09/20 0.012 0.021 0.011 0.020 0.011 0.019 0.013 0.023 0.005 0.015 0.004 0.014 0.002 0.007 0.005 0.015 06/23/20 0.000 0.012 0.000 0.011 0.000 0.010 0.000 0.012

-0.005 0.011

-0.005 0.011

-0.005 0.010

-0.005 0.011 07/07/20

-0.008 0.020

-0.008 0.020

-0.008 0.019

-0.009 0.023 0.004 0.012 0.004 0.011 0.002 0.006 0.004 0.011 07/21/20 0.000 0.011 0.000 0.011 0.000 0.010 0.000 0.012

-0.007 0.022

-0.006 0.020

-0.006 0.019

-0.007 0.021 08/04/20 0.012 0.018 0.012 0.017 0.011 0.016 0.012 0.017

-0.003 0.009

-0.004 0.009

-0.004 0.009

-0.004 0.010 08/19/20 0.006 0.009 0.006 0.010 0.008 0.012 0.006 0.009

-0.002 0.012

-0.002 0.011

-0.002 0.010

-0.002 0.010 09/01/20

-0.003 0.010

-0.003 0.010

-0.004 0.012

-0.004 0.011

-0.003 0.010

-0.003 0.010

-0.003 0.010

-0.003 0.010 09/15/20

-0.005 0.020

-0.005 0.020

-0.006 0.025

-0.006 0.024 0.010 0.022 0.009 0.022 0.009 0.021 0.009 0.021 09/29/20

-0.005 0.010

-0.005 0.010

-0.007 0.014

-0.007 0.013

-0.002 0.012

-0.002 0.012

-0.002 0.012

-0.002 0.011 10/13/20

-0.005 0.010

-0.005 0.010

-0.005 0.010

-0.005 0.010

-0.007 0.010

-0.007 0.010

-0.007 0.011

-0.006 0.009 10/27/20 0.000 0.017 0.000 0.018 0.000 0.018 0.000 0.017

-0.004 0.012

-0.005 0.012

-0.005 0.013

-0.004 0.011 11/10/20

-0.004 0.015

-0.004 0.016

-0.004 0.016

-0.004 0.014 0.006 0.019 0.006 0.020 0.006 0.022 0.006 0.019 11/24/20

-0.003 0.016

-0.003 0.017

-0.004 0.018

-0.002 0.011

-0.003 0.018

-0.004 0.020

-0.004 0.020

-0.004 0.018 12/08/20

-0.016 0.012

-0.017 0.013

-0.019 0.015

-0.017 0.013

-0.014 0.020

-0.016 0.023

-0.015 0.021

-0.015 0.021 12/22/20

-0.002 0.008

-0.006 0.021

-0.006 0.024

-0.005 0.021

-0.002 0.025

-0.002 0.024

-0.002 0.025

-0.002 0.029 01/05/21 0.009 0.015 0.010 0.017 0.012 0.019 0.010 0.016

-0.012 0.019

-0.012 0.018

-0.011 0.018

-0.006 0.009 C= Control location, Background location TABLE 3 AIRBORNE IODINE (pCi/m3)

LOCATIONS

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311

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1 0.0053 0.0092

-0.0001 0.0023 0.1005 0.0261 0.0003 0.0008

-0.0009 0.0015

-0.0004 0.0011

-0.0008 0.0021 2

0.0019 0.0113

-0.0021 0.0026 0.0990 0.0287 0.0010 0.0013 0.0001 0.0018

-0.0005 0.0011 0.0000 0.0021 3

0.0078 0.0120 0.0017 0.0030 0.1148 0.0261 0.0009 0.0011

-0.0002 0.0016

-0.0004 0.0011

-0.0003 0.0020 4

0.0011 0.0105

-0.0015 0.0029 0.0986 0.0242 0.0006 0.0010

-0.0007 0.0013 0.0003 0.0014 0.0030 0.0026 10

-0.0030 0.0096 0.0020 0.0030 0.1167 0.0268 0.0000 0.0013 0.0007 0.0022 0.0014 0.0013 0.0013 0.0030 11 0.0138 0.0114

-0.0005 0.0018 0.1106 0.0279 0.0001 0.0019

-0.0019 0.0020 0.0003 0.0017

-0.0007 0.0042 27 0.0074 0.0119

-0.0002 0.0023 0.0996 0.0244 0.0011 0.0011

-0.0006 0.0017

-0.0005 0.0011 0.0006 0.0026 15C 0.0073 0.0111 0.0008 0.0023 0.1079 0.0237 0.0013 0.0010

-0.0011 0.0015

-0.0004 0.0011 0.0006 0.0024 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1

-0.0006 0.0012 0.0001 0.0024 0.0009 0.0018

-0.0004 0.0075 0.0001 0.0011

-0.0007 0.0008 0.0101 0.0424 2

0.0006 0.0017 0.0008 0.0029 0.0008 0.0021 0.0037 0.0093

-0.0001 0.0011 0.0012 0.0011 0.0263 0.0475 3

-0.0001 0.0019 0.0014 0.0033

-0.0009 0.0022

-0.0049 0.0102

-0.0009 0.0010

-0.0004 0.0010

-0.0176 0.0480 4

0.0004 0.0012

-0.0008 0.0028

-0.0011 0.0020

-0.0044 0.0084 0.0002 0.0011 0.0000 0.0009 0.0041 0.0452 10

-0.0001 0.0018

-0.0004 0.0038

-0.0004 0.0029

-0.0030 0.0136 0.0012 0.0016 0.0003 0.0013 0.0790 0.0606 11

-0.0015 0.0025 0.0041 0.0041

-0.0020 0.0032

-0.0089 0.0139

-0.0005 0.0016 0.0004 0.0013 0.0505 0.0692 27 0.0008 0.0013 0.0027 0.0030

-0.0007 0.0021 0.0060 0.0097

-0.0009 0.0010

-0.0005 0.0011 0.0264 0.0493 15C

-0.0007 0.0014 0.0022 0.0025 0.0002 0.0016 0.0014 0.0086

-0.0004 0.0010 0.0006 0.0009

-0.0182 0.0386 LOCATION Ce-141 Ce-144

(+/-)

(+/-)

1 0.0009 0.0025

-0.0016 0.0047 2

-0.0018 0.0027

-0.0020 0.0048 3

0.0000 0.0030 0.0010 0.0047 4

-0.0018 0.0022

-0.0003 0.0038 10 0.0030 0.0036

-0.0012 0.0060 11 0.0002 0.0039

-0.0024 0.0061 27

-0.0028 0.0026

-0.0007 0.0040 15C 0.0001 0.0023 0.0008 0.0039 C= Control location, Background location Results in bold type are positive.

TABLE 4 AIR PARTICULATES (pCi/m3)

GAMMA SPECTRA - QTR 1 (1/7/20 - 03/31/20)

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312

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1 0.0034 0.0090 0.0019 0.0027 0.1067 0.0278 0.0009 0.0012 0.0000 0.0014

-0.0008 0.0011 0.0031 0.0023 2

-0.0006 0.0082

-0.0008 0.0020 0.1201 0.0250

-0.0003 0.0009

-0.0010 0.0012 0.0006 0.0006

-0.0007 0.0023 3

0.0073 0.0099 0.0005 0.0021 0.1064 0.0224

-0.0010 0.0009

-0.0004 0.0013

-0.0003 0.0008 0.0018 0.0021 4

-0.0070 0.0080

-0.0021 0.0023 0.1343 0.0267 0.0000 0.0009 0.0003 0.0016 0.0006 0.0013

-0.0017 0.0031 10 0.0053 0.0103 0.0005 0.0020 0.1111 0.0380

-0.0015 0.0018 0.0006 0.0020 0.0009 0.0014 0.0026 0.0031 11 0.0023 0.0095 0.0006 0.0021 0.1141 0.0241 0.0002 0.0010

-0.0013 0.0015 0.0004 0.0012 0.0031 0.0027 27 0.0066 0.0093 0.0010 0.0020 0.1307 0.0294 0.0004 0.0011 0.0001 0.0019

-0.0005 0.0011 0.0013 0.0025 15C

-0.0001 0.0093 0.0007 0.0020 0.1066 0.0272 0.0011 0.0009

-0.0002 0.0015 0.0012 0.0011

-0.0007 0.0023 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1

-0.0003 0.0018

-0.0005 0.0029 0.0017 0.0024 0.0039 0.0109 0.0007 0.0010 0.0005 0.0011

-0.0052 0.0743 2

0.0002 0.0014

-0.0002 0.0025

-0.0012 0.0020

-0.0082 0.0078 0.0000 0.0009 0.0009 0.0007 0.0426 0.0495 3

0.0016 0.0014

-0.0005 0.0023

-0.0006 0.0017

-0.0021 0.0060 0.0006 0.0009 0.0000 0.0007

-0.0142 0.0447 4

0.0012 0.0016

-0.0002 0.0029

-0.0010 0.0022

-0.0022 0.0085

-0.0001 0.0010 0.0011 0.0009 0.0002 0.0589 10

-0.0028 0.0027 0.0001 0.0049 0.0023 0.0037 0.0047 0.0165 0.0006 0.0012

-0.0009 0.0016

-0.0017 0.0925 11 0.0004 0.0015

-0.0019 0.0028

-0.0001 0.0019 0.0049 0.0074

-0.0005 0.0010 0.0004 0.0008 0.0004 0.0592 27

-0.0013 0.0016 0.0002 0.0030

-0.0016 0.0027 0.0014 0.0107

-0.0007 0.0012 0.0000 0.0011 0.0083 0.0738 15C

-0.0011 0.0015 0.0005 0.0024 0.0001 0.0021

-0.0080 0.0089

-0.0006 0.0009 0.0004 0.0009

-0.0186 0.0611 LOCATION Ce-141 Ce-144

(+/-)

(+/-)

1 0.0003 0.0037 0.0035 0.0054 2

-0.0008 0.0028 0.0022 0.0036 3

-0.0009 0.0022

-0.0005 0.0036 4

0.0015 0.0034

-0.0009 0.0047 10

-0.0026 0.0049

-0.0009 0.0074 11

-0.0009 0.0030 0.0027 0.0044 27

-0.0010 0.0033

-0.0013 0.0050 15C 0.0003 0.0026

-0.0012 0.0036 C= Control location, Background location Results in bold type are positive.

TABLE 4 AIR PARTICULATES (pCi/m3)

GAMMA SPECTRA - QTR 2 (03/31/20 - 07/07/20)

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313

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1 0.0017 0.0104 0.0044 0.0035 0.1227 0.0304 0.0008 0.0014

-0.0006 0.0022

-0.0002 0.0017 0.0019 0.0034 2

0.0092 0.0138 0.0004 0.0026 0.1268 0.0283 0.0007 0.0012

-0.0014 0.0017

-0.0003 0.0010 0.0001 0.0025 3

0.0118 0.0160 0.0048 0.0040 0.1349 0.0342 0.0000 0.0012

-0.0008 0.0019 0.0012 0.0011

-0.0005 0.0028 4

-0.0016 0.0117 0.0029 0.0030 0.1448 0.0305 0.0004 0.0012 0.0006 0.0014 0.0002 0.0013 0.0015 0.0030 10 0.0162 0.0157 0.0010 0.0024 0.1298 0.0356 0.0004 0.0015

-0.0017 0.0022 0.0001 0.0014 0.0010 0.0041 11

-0.0044 0.0103 0.0018 0.0031 0.1410 0.0281 0.0000 0.0011

-0.0005 0.0014 0.0008 0.0015 0.0014 0.0022 27 0.0009 0.0117

-0.0004 0.0021 0.1349 0.0310 0.0000 0.0019

-0.0002 0.0026

-0.0002 0.0014

-0.0001 0.0043 15C

-0.0001 0.0111 0.0007 0.0028 0.1080 0.0296 0.0008 0.0014 0.0014 0.0021

-0.0006 0.0013 0.0013 0.0025 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1

-0.0014 0.0019 0.0003 0.0035 0.0006 0.0031 0.0043 0.0105

-0.0001 0.0015

-0.0002 0.0012

-0.0065 0.0789 2

0.0010 0.0015

-0.0020 0.0030

-0.0005 0.0020

-0.0002 0.0097

-0.0003 0.0010

-0.0003 0.0008

-0.0241 0.0550 3

0.0000 0.0017

-0.0025 0.0033 0.0002 0.0022 0.0051 0.0093

-0.0008 0.0015

-0.0001 0.0008

-0.0197 0.0803 4

0.0000 0.0016 0.0000 0.0026 0.0004 0.0024 0.0004 0.0116 0.0001 0.0012 0.0001 0.0011

-0.0379 0.0629 10 0.0016 0.0025

-0.0005 0.0042 0.0011 0.0029

-0.0147 0.0130

-0.0005 0.0016

-0.0001 0.0014

-0.0025 0.1030 11

-0.0003 0.0016 0.0001 0.0032 0.0001 0.0024 0.0016 0.0092

-0.0008 0.0012 0.0004 0.0008

-0.0003 0.0582 27

-0.0041 0.0027 0.0023 0.0046

-0.0016 0.0031 0.0044 0.0131 0.0004 0.0018

-0.0018 0.0015 0.0906 0.1058 15C 0.0010 0.0019

-0.0033 0.0036 0.0002 0.0031

-0.0056 0.0135

-0.0004 0.0013 0.0004 0.0011

-0.0489 0.0790 LOCATION Ce-141 Ce-144

(+/-)

(+/-)

1

-0.0015 0.0039

-0.0039 0.0056 2

0.0007 0.0031 0.0022 0.0045 3

-0.0005 0.0037 0.0011 0.0052 4

0.0046 0.0034 0.0013 0.0049 10

-0.0034 0.0043 0.0005 0.0062 11 0.0013 0.0028

-0.0012 0.0038 27 0.0025 0.0047 0.0016 0.0067 15C 0.0021 0.0037 0.0019 0.0057 C= Control location, Background location Results in bold type are positive.

TABLE 4 AIR PARTICULATES (pCi/m3)

GAMMA SPECTRA - QTR 3 (07/07/20 - 09/29/20)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

314

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1

-0.0007 0.0115

-0.0004 0.0018 0.0898 0.0199

-0.0001 0.0008

-0.0010 0.0014 0.0004 0.0009 0.0009 0.0024 2

0.0044 0.0114

-0.0014 0.0018 0.1028 0.0210 0.0002 0.0008

-0.0007 0.0011 0.0003 0.0009

-0.0012 0.0024 3

0.0159 0.0139

-0.0015 0.0015 0.0961 0.0210

-0.0008 0.0008

-0.0001 0.0017 0.0002 0.0009 0.0018 0.0025 4

-0.0058 0.0082

-0.0013 0.0019 0.1029 0.0232 0.0001 0.0012

-0.0002 0.0017 0.0000 0.0010

-0.0004 0.0026 10

-0.0063 0.0100

-0.0004 0.0018 0.0998 0.0254 0.0002 0.0009

-0.0011 0.0013 0.0005 0.0010 0.0001 0.0025 11 0.0056 0.0101

-0.0001 0.0013 0.1054 0.0278

-0.0015 0.0013

-0.0012 0.0019 0.0001 0.0013 0.0005 0.0035 27

-0.0048 0.0095 0.0004 0.0020 0.0881 0.0232 0.0007 0.0009 0.0002 0.0010 0.0006 0.0008

-0.0024 0.0028 15C 0.0108 0.0118 0.0017 0.0019 0.0831 0.0190

-0.0002 0.0009

-0.0009 0.0015 0.0000 0.0010 0.0014 0.0025 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

1 0.0007 0.0014 0.0006 0.0021

-0.0003 0.0016 0.0017 0.0075

-0.0003 0.0009 0.0002 0.0007 0.0221 0.0321 2

0.0005 0.0012 0.0005 0.0024 0.0007 0.0017 0.0037 0.0085

-0.0001 0.0008

-0.0001 0.0007

-0.0023 0.0517 3

-0.0003 0.0013 0.0006 0.0023 0.0017 0.0016

-0.0053 0.0075

-0.0001 0.0009

-0.0003 0.0008

-0.0066 0.0533 4

-0.0006 0.0014

-0.0005 0.0026 0.0002 0.0021 0.0084 0.0091

-0.0004 0.0011 0.0001 0.0010 0.0139 0.0642 10

-0.0004 0.0013 0.0011 0.0019 0.0006 0.0019

-0.0037 0.0074

-0.0006 0.0008

-0.0005 0.0008 0.0002 0.0504 11 0.0003 0.0019

-0.0005 0.0034 0.0014 0.0025

-0.0020 0.0105

-0.0001 0.0012

-0.0006 0.0012

-0.0438 0.0825 27 0.0013 0.0018

-0.0012 0.0025

-0.0017 0.0020 0.0060 0.0083

-0.0003 0.0008 0.0001 0.0008 0.0827 0.0558 15C 0.0007 0.0015

-0.0014 0.0023 0.0005 0.0018 0.0008 0.0073

-0.0002 0.0010

-0.0003 0.0008 0.0168 0.0538 LOCATION Ce-141 Ce-144

(+/-)

(+/-)

1

-0.0013 0.0022

-0.0009 0.0033 2

-0.0005 0.0027

-0.0005 0.0037 3

0.0011 0.0025

-0.0008 0.0038 4

0.0008 0.0030

-0.0047 0.0047 10 0.0008 0.0025

-0.0040 0.0033 11

-0.0009 0.0034 0.0031 0.0055 27 0.0018 0.0029 0.0026 0.0040 15C

-0.0003 0.0028

-0.0007 0.0041 C= Control location, Background location Results in bold type are positive.

GAMMA SPECTRA - QTR 4 (09/29/20 - 01/05/21)

TABLE 4 AIR PARTICULATES (pCi/m3)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

315

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

3 05/05/20 0.400 0.344 16.670 1.805 0.238 0.284 0.041 0.040 0.002 0.040

-0.032 0.085 4

05/05/20 0.506 0.491 15.470 1.919 0.260 0.389 0.022 0.055

-0.033 0.040 0.062 0.107 14C 05/05/20 0.430 0.448 17.000 2.027

-0.136 0.368

-0.034 0.057 0.009 0.045

-0.023 0.113 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

3 05/05/20

-0.021 0.043

-0.089 0.126

-0.029 0.040 0.073 0.067 0.002 0.032

-0.030 0.366 4

05/05/20

-0.036 0.052

-0.210 0.146

-0.008 0.054

-0.038 0.091 0.029 0.048

-0.204 0.481 14C 05/05/20

-0.018 0.045

-0.154 0.134

-0.011 0.051

-0.012 0.084 0.027 0.045 0.228 0.427 COLLECTION LOCATION DATE Sb-125 Cs-134 Cs-137 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

3 05/05/20 0.004 0.083 0.072 0.045 0.059 0.052

-0.024 0.043

-0.026 0.187 0.628 0.310 4

05/05/20

-0.128 0.130 0.034 0.057 0.333 0.128

-0.021 0.062 0.150 0.270 1.132 0.331 14C 05/05/20

-0.057 0.122 0.077 0.058 0.283 0.101

-0.034 0.070

-0.132 0.278 0.703 0.444 C= Control location, Background location Results in bold type are postive.

TABLE 5 SOIL (pCi/g dry wt.)

LOCATIONS

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

316

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

22 Cow Milk was not availible for collection in 2020. Strontium Analysis of Air Samples (Table 4) and Gamma Analysis of Broadleaf Vegetation (Table 9) were performed as valid substitutes for Milk.

23 Goat TABLE 6 MILK (pCi/l)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

317

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

71 03/24/20 224 473

-10.1 26.2 16.2 48.4

-9.76 29.6

-1.68 2.95 0.74 3.03 3.69 6.59

-1.23 3.37 05/07/20 182 461

-1.77 33.9 21.5 52.5 23.3 37.7 2.96 3.89

-4.26 4.08

-6.87 8.02 2.94 4.61 09/15/20 279 586 22.7 44.1

-47.3 52.3

-12.8 44.7

-3.23 5.11

-2.19 5.16 1.60 8.61

-1.84 5.26 12/03/20

-19 576 23.9 30.9 6.10 47.2

-1.67 35.8

-0.28 3.21

-1.58 3.60

-2.01 6.49 0.96 2.86 72 03/24/20 387 486 10.0 24.2 9.89 42.2

-9.05 27.5 0.92 2.82 2.11 2.78 2.19 5.55 1.07 2.94 05/07/20 165 457 15.4 33.6 19.6 78.4 12.1 34.5

-1.19 3.61

-2.89 4.23

-3.59 6.95 0.21 3.40 08/06/20

-222 424 25.3 37.9 57.0 66.1 24.9 40.4 3.47 3.90 2.16 4.28 5.29 8.24

-1.93 3.76 12/03/20 13 578 35.0 31.9 58.5 57.2

-45.3 39.8

-1.16 3.18

-0.32 3.68

-1.42 7.29 0.97 3.97 76 03/10/20 171 546 22.3 39.4

-5.75 67.7

-1.78 40.2 1.87 4.37

-1.02 4.46

-2.64 9.10

-1.73 4.78 04/29/20 33 472 0.48 29.9 14.1 54.3

-4.19 34.2 1.34 4.14

-4.63 3.77

-0.14 7.81 1.08 4.17 09/16/20 209 580 59.7 44.0 3.70 81.2

-10.5 48.9 2.06 4.95

-3.21 4.87

-5.66 9.24

-5.35 5.77 10/23/20 51 437 11.9 34.9 15.3 53.5

-1.37 36.4

-1.32 3.90

-2.98 4.18

-1.00 7.47 1.00 3.62 77 03/10/20

-278 510

-61.0 48.4

-5.54 65.4 15.9 43.2 0.40 5.73 1.51 5.74

-3.54 10.8 1.02 5.30 04/29/20

-130 455

-12.2 47.4 77.6 85.1

-20.0 53.8

-2.71 6.06

-3.70 5.94 1.48 11.0

-4.76 6.81 09/16/20 418 596

-28.8 53.2

-14.8 72.8

-62.4 58.5

-2.09 5.28

-5.32 6.75 4.58 11.2

-4.30 5.65 10/23/20 251 435 17.3 41.4

-46.1 70.2

-12.5 45.4 1.87 5.01

-1.88 5.29 0.86 9.77 1.93 5.66 78 03/10/20

-196 517 0.01 29.3 11.1 61.7 24.5 30.7

-1.25 3.91 0.79 4.16 1.31 7.19

-0.55 4.08 04/29/20 70 469

-38.5 36.4

-48.2 64.3 11.8 33.4 1.48 4.10 0.35 3.90

-0.70 7.81 0.53 3.47 09/16/20 108 574

-21.3 38.4

-50.5 56.4

-11.3 38.1 1.62 4.47

-0.52 4.58

-4.39 10.0

-2.60 4.82 10/23/20 82 438

-9.63 36.5

-17.0 67.5

-2.89 38.0 1.40 4.02 0.04 4.35

-0.04 8.32 2.69 5.51 79 03/24/20 444 480 27.9 25.1 46.0 51.4

-18.0 30.2 0.18 2.88

-1.13 2.81

-1.83 5.90 2.50 3.47 05/08/20

-99 443 11.7 32.7

-11.0 57.0 31.9 38.9 1.60 3.47

-2.12 3.96 6.68 7.98 2.83 4.26 08/06/20 34 438 23.2 34.0

-26.9 48.8 0.09 33.2 2.04 3.22 2.65 3.54

-1.11 5.83 0.39 3.68 12/03/20

-152 565 0.98 15.4 35.2 39.5

-1.21 17.4 0.17 1.57 0.07 1.67 3.73 3.50 0.60 1.60 81 03/24/20 182 461

-27.2 27.9 16.7 55.0 11.3 33.4 1.21 3.17

-2.95 3.34 4.71 5.85

-2.22 3.40 04/23/20 41 472 0.61 39.3 4.71 52.2

-4.05 39.0 0.01 4.44

-2.43 4.69

-9.53 8.84

-3.29 4.75 07/28/20 322 480 11.7 34.6 41.3 73.8

-4.83 37.8

-1.59 4.04

-1.63 4.42 6.86 9.14 4.35 3.88 12/02/20 32 579 17.8 15.5 6.69 40.4

-17.3 19.1

-0.12 1.76

-0.17 1.74

-3.20 3.57

-1.32 1.63 82 03/11/20 246 470

-9.38 44.7 38.3 101

-37.5 47.5

-4.01 4.40

-3.79 4.64

-0.02 9.07 4.42 4.42 04/23/20

-157 451

-20.7 50.4

-36.6 68.3 12.3 53.6

-4.92 5.65

-11.7 6.50 8.48 11.0

-1.04 5.45 07/27/20

-129 374

-21.1 39.4

-34.9 46.3 0.79 44.3

-1.12 4.57

-7.25 4.65

-1.61 7.63

-1.61 3.93 10/15/20 75 417

-16.1 44.8 0.92 63.7 12.7 48.5

-3.03 5.23

-6.60 4.92 2.96 10.2 1.23 5.60 83 03/24/20 355 477 27.2 28.4 4.97 51.4 1.06 30.5 1.62 3.47

-2.77 3.44

-4.59 6.48

-1.50 3.26 05/06/20

-257 433

-4.65 30.5 24.2 45.1 17.0 31.2 0.86 3.30

-1.77 3.11 0.04 7.66

-1.25 3.53 07/27/20 331 480 16.8 38.4

-45.3 57.6 6.72 38.7 1.16 4.61

-2.82 3.63

-0.84 7.55 3.06 4.27 12/02/20

-89 572 8.46 15.7

-9.22 25.0

-14.5 18.2

-1.07 1.63

-1.01 1.70

-1.11 3.57

-1.24 1.72 TABLE 7 WELL WATER (pCi/l)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

318

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

71 03/24/20

-24.4 9.21 2.73 3.60

-2.26 6.08 3.70 3.60

-12.9 29.2 0.24 8.70 0.97 5.09

-0.41 3.29 05/07/20

-20.2 11.0 3.42 4.90 2.38 7.59 0.12 4.53

-21.6 38.8 4.90 10.4

-1.36 6.93

-0.95 4.03 09/15/20 1.13 10.6

-1.16 6.19 8.33 8.86

-3.45 4.47

-2.63 46.3

-13.0 16.0 2.12 5.94

-2.29 5.08 12/03/20

-9.63 9.09

-0.31 3.71

-1.00 6.39

-2.36 3.39 29.0 30.2 0.86 10.5 0.19 8.63 1.11 3.77 72 03/24/20

-15.5 7.62 1.07 2.97

-0.44 5.01

-1.64 2.92

-6.25 26.6 5.39 8.23 0.52 4.74 1.02 2.92 05/07/20

-11.2 9.95

-0.70 3.99 2.58 7.25

-2.16 4.28

-35.4 39.7

-5.19 10.4

-5.32 6.75

-3.60 3.47 08/06/20

-12.0 10.2

-0.10 4.42

-2.37 6.71

-1.81 4.22 24.0 33.6 3.83 12.1

-2.30 7.16

-0.91 4.85 12/03/20

-12.0 9.50 5.81 3.87 0.28 6.33

-2.67 3.97 4.56 30.3 1.14 9.65

-1.97 8.97 0.65 3.88 76 03/10/20 12.1 6.96 4.71 5.37 0.60 7.74

-2.15 4.93 17.0 43.2 0.46 12.7 5.85 5.83

-0.30 5.22 04/29/20 7.12 9.05 3.41 3.78

-0.46 6.16 0.20 4.15 9.83 35.8

-1.35 11.5

-3.06 4.39 1.01 4.41 09/16/20

-1.16 11.3 5.46 5.36

-4.21 8.46 1.89 5.07 32.3 39.8 0.55 16.0

-3.76 6.18 0.25 5.20 10/23/20

-10.5 11.5 1.55 4.15 0.67 7.08

-3.63 4.45 9.35 34.2

-6.47 10.5 2.09 6.30

-1.48 3.78 77 03/10/20

-9.11 16.6 6.09 5.98

-3.34 8.75

-1.67 5.29

-23.2 49.6

-7.88 16.6 1.79 6.58 4.64 6.08 04/29/20

-0.72 13.5 6.81 8.11

-6.47 11.4

-5.23 6.04 7.51 52.2

-13.9 16.3

-4.13 6.57 2.54 6.97 09/16/20

-2.33 15.0 3.08 7.84

-1.80 10.2

-2.88 6.15 20.6 60.0 13.5 18.0

-0.71 7.16 1.43 6.23 10/23/20 8.01 11.5 2.64 5.86 0.35 8.59 0.11 5.08 38.4 43.8 6.10 13.3 1.38 7.77

-3.57 4.63 78 03/10/20

-6.96 10.9 3.84 4.52 4.46 5.96

-0.04 4.29 2.04 36.1 4.80 11.0 2.62 4.82

-1.67 4.65 04/29/20

-15.1 11.4

-1.43 3.78 1.17 6.38

-1.40 3.97 19.9 37.8 7.20 11.8

-0.73 4.52 1.09 4.21 09/16/20

-19.7 12.5 1.20 5.66 4.07 8.05

-2.33 5.11 29.5 40.1

-1.60 14.2 0.14 5.88 0.57 6.10 10/23/20

-13.0 12.0 0.43 5.11 2.62 7.52 1.45 5.27 19.0 38.8

-4.06 12.1 0.01 6.47

-2.10 4.96 79 03/24/20

-9.41 7.73 0.07 3.06 0.80 5.79 0.28 3.03 1.79 27.3 4.96 7.95 0.83 5.04 2.01 3.39 05/08/20

-17.0 9.81 0.55 4.26

-0.25 5.76

-3.96 4.26 17.6 32.4 8.62 11.6

-2.67 7.15

-0.91 4.01 08/06/20

-8.11 10.7 0.35 3.67 0.00 6.44 3.78 3.78

-22.8 35.7 1.65 11.2 3.08 5.56

-0.43 4.88 12/03/20

-5.44 3.73 0.91 1.72 0.21 2.84 0.96 1.95

-2.76 14.5

-1.89 4.72

-4.57 4.11

-0.68 1.78 81 03/24/20 5.21 6.83 4.43 3.67 1.85 5.43

-2.25 3.39 18.1 29.1 4.83 9.59

-1.68 5.36 1.65 3.54 04/23/20 0.24 8.15 1.15 4.75 3.14 6.49 1.87 4.74

-13.1 42.1 5.64 13.1 2.20 6.06 0.81 4.74 07/28/20

-0.11 9.15

-2.05 4.83

-5.19 6.97

-2.60 4.60 9.68 34.1 4.32 10.7 1.10 6.67

-4.98 4.74 12/02/20 2.96 3.34

-0.66 2.01

-1.29 3.03

-0.67 2.02 4.80 14.6 2.82 4.56 0.83 4.94 0.13 1.83 82 03/11/20 3.35 8.88 10.0 5.05

-0.21 7.13 3.00 4.59

-23.3 37.8

-4.71 13.3

-3.63 8.88 2.23 4.45 04/23/20

-4.10 14.6 9.42 6.96

-4.21 10.1

-4.06 5.86

-9.08 50.0 0.82 17.8 4.22 7.91

-1.63 5.78 07/27/20 5.33 10.1 8.20 5.17 2.77 7.24 1.83 4.64 9.03 35.3 3.54 14.6 1.10 8.57 1.60 4.41 10/15/20

-2.70 11.9 14.7 6.11

-1.06 8.06

-1.07 4.94 30.7 42.3

-5.45 15.5

-4.14 7.62 0.19 5.15 83 03/24/20

-0.73 7.72 3.80 4.01

-0.27 5.99

-1.42 3.43

-0.60 29.7

-0.60 9.54

-1.88 5.35

-1.65 3.44 05/06/20 0.45 7.57 1.35 3.92 1.36 6.20

-2.13 3.52 5.20 30.8

-1.80 9.49 1.74 6.73 0.12 3.68 07/27/20

-15.0 11.8

-1.67 5.15 4.14 8.33

-3.62 4.70 10.9 43.0 0.59 11.7 2.58 7.21

-1.06 4.58 12/02/20 2.14 3.80 0.51 1.92 1.13 3.25

-0.21 2.03 5.20 14.8

-2.56 4.36 2.58 4.58 2.00 1.77 TABLE 7 WELL WATER (pCi/l)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

319

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

(+/-)

(+/-)

(+/-)

(+/-)

71 03/24/20

-2.99 3.49 4.96 13.4

-0.56 5.28

-0.81 11.6 05/07/20

-1.31 4.50 0.89 17.9 0.30 6.08 0.15 14.9 09/15/20

-0.86 4.86 3.81 19.5 0.26 7.05 5.42 19.3 12/03/20 0.14 4.05

-7.54 21.1 4.85 6.54

-4.69 12.9 72 03/24/20

-2.27 3.08

-2.81 13.0 0.10 4.21

-0.44 11.1 05/07/20

-0.94 4.28 3.94 18.3

-0.33 7.34

-13.3 14.6 08/06/20 1.94 4.43 0.15 16.3

-0.10 6.91 12.3 15.8 12/03/20

-2.15 3.49

-2.98 20.7 3.60 7.56

-10.5 12.1 76 03/10/20

-6.39 5.29

-6.76 19.5 5.32 6.64 10.9 18.1 04/29/20

-1.30 3.91 4.12 14.3 5.43 5.50

-0.32 15.5 09/16/20

-2.31 5.70 14.9 21.5 2.49 6.23 15.2 20.0 10/23/20

-1.35 4.20

-1.92 18.8

-2.29 5.61

-3.43 15.3 77 03/10/20

-4.48 6.86

-3.75 22.3 0.88 6.36

-11.6 18.4 04/29/20

-9.43 7.34 10.0 23.0 4.42 6.55 15.8 22.2 09/16/20

-3.21 6.98 1.65 24.2 4.90 7.89 13.0 25.7 10/23/20

-6.51 5.27

-18.9 23.8

-0.66 6.41 5.8 18.1 78 03/10/20 0.89 3.76 12.3 18.7 1.03 4.56

-3.62 14.2 04/29/20

-1.06 4.30 3.66 15.6 3.30 5.39 17.1 17.8 09/16/20

-1.28 5.36 2.58 17.2 5.13 6.12 7.56 17.5 10/23/20 0.15 4.95 3.89 22.1

-1.84 4.12

-8.71 16.8 79 03/24/20 2.04 3.43 13.5 12.7

-1.30 4.36 14.5 10.5 05/08/20 0.77 4.29

-10.6 19.9 5.42 6.10

-0.35 15.5 08/06/20

-0.37 4.24 8.11 16.1

-1.11 4.89 5.82 13.5 12/03/20

-0.96 1.73

-2.76 9.85 0.67 2.88

-3.09 6.74 81 03/24/20

-4.00 3.41

-11.1 15.7 3.61 4.03

-3.68 12.7 04/23/20

-4.98 4.68 7.09 16.9 2.17 4.60 0.97 16.3 07/28/20 0.41 3.97

-0.05 22.0 5.68 6.44 5.32 14.9 12/02/20

-0.46 1.77 0.28 11.2 0.42 3.74

-2.71 7.07 82 03/11/20

-7.28 4.57

-4.92 22.8

-0.73 6.97 8.00 16.7 04/23/20

-10.8 6.11 3.78 23.8 3.16 8.29

-0.88 20.3 07/27/20

-0.32 4.98 11.2 21.9

-1.30 7.41

-8.69 14.4 10/15/20 1.87 5.88

-5.10 23.5 7.63 7.34

-6.04 20.5 83 03/24/20

-4.66 3.48

-12.2 15.3 1.04 5.24

-4.00 12.2 05/06/20

-0.45 2.99 7.22 20.0 3.45 6.53 8.43 11.5 07/27/20 3.49 4.34

-23.9 22.5 6.91 6.85

-5.39 14.3 12/02/20 1.11 1.67

-3.02 11.1 1.15 3.47

-1.27 6.52 TABLE 7 WELL WATER (pCi/l)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

07/28/20 Lettuce 0.261 0.194 7.242 0.872 0.199 0.160

-0.008 0.018

-0.005 0.019 0.029 0.045

-0.007 0.022 07/28/20 Apples

-0.036 0.129 1.309 0.386 0.174 0.150

-0.005 0.015 0.006 0.014 0.013 0.037 0.003 0.017 10/06/20 Tomatoes 0.001 0.102 1.803 0.367

-0.054 0.092 0.003 0.013

-0.002 0.010 0.011 0.027

-0.004 0.011 10/06/20 Apples 0.050 0.099 1.009 0.314

-0.036 0.103

-0.002 0.014 0.006 0.012 0.009 0.022

-0.010 0.013 COLLECTION DATE Type Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

07/28/20 Lettuce

-0.099 0.052

-0.005 0.024 0.020 0.036

-0.012 0.018 0.115 0.169

-0.029 0.047

-0.018 0.029 07/28/20 Apples 0.006 0.038 0.009 0.017 0.008 0.032 0.003 0.015 0.012 0.139 0.004 0.041

-0.003 0.026 10/06/20 Tomatoes 0.008 0.032 0.006 0.012

-0.013 0.022

-0.003 0.013 0.082 0.118 0.008 0.033

-0.004 0.015 10/06/20 Apples

-0.003 0.028 0.016 0.016 0.015 0.021

-0.003 0.011

-0.045 0.111

-0.011 0.040 0.001 0.015 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

07/28/20 Lettuce

-0.009 0.020 0.012 0.021 0.017 0.085

-0.003 0.025

-0.003 0.024 0.073 0.104 0.067 0.088 07/28/20 Apples 0.005 0.017 0.005 0.017 0.012 0.080 0.000 0.021 0.001 0.023

-0.018 0.099

-0.030 0.051 10/06/20 Tomatoes

-0.014 0.013

-0.009 0.014

-0.020 0.045 0.002 0.013 0.001 0.017 0.033 0.071

-0.034 0.046 10/06/20 Apples 0.002 0.015 0.003 0.015

-0.026 0.049 0.011 0.017

-0.004 0.019

-0.020 0.082

-0.051 0.045 Results in bold type are positive.

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

TABLE 8 FRUITS & VEGETABLES (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

07/28/20 Lettuce 0.096 0.138 2.256 0.432

-0.009 0.123 0.003 0.012

-0.008 0.014

-0.015 0.030

-0.007 0.017 07/28/20 Plums

-0.060 0.176 1.163 0.477 0.101 0.165 0.010 0.019 0.006 0.018

-0.011 0.036

-0.015 0.025 10/06/20 Tomatoes

-0.027 0.118 1.613 0.441 0.060 0.133 0.004 0.017 0.005 0.018

-0.009 0.028 0.000 0.015 10/06/20 Apples

-0.017 0.088 0.469 0.246 0.035 0.084 0.009 0.011 0.001 0.010 0.015 0.019 0.005 0.009 COLLECTION DATE Type Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

07/28/20 Lettuce

-0.034 0.038 0.002 0.016 0.031 0.026

-0.018 0.013

-0.061 0.129

-0.032 0.038

-0.002 0.024 07/28/20 Plums

-0.023 0.051 0.011 0.023 0.020 0.040 0.000 0.019

-0.083 0.172 0.039 0.058

-0.033 0.033 10/06/20 Tomatoes 0.039 0.032 0.020 0.019 0.017 0.030

-0.001 0.016

-0.063 0.133 0.005 0.042

-0.004 0.017 10/06/20 Apples

-0.007 0.023 0.002 0.010

-0.005 0.018

-0.007 0.011

-0.065 0.092 0.004 0.029

-0.009 0.012 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

07/28/20 Lettuce

-0.002 0.015 0.007 0.016 0.051 0.059 0.001 0.017 0.009 0.022

-0.023 0.084

-0.015 0.054 07/28/20 Plums

-0.010 0.023 0.002 0.022

-0.089 0.089 0.002 0.036

-0.018 0.029 0.042 0.128

-0.008 0.075 10/06/20 Tomatoes 0.002 0.017

-0.004 0.015 0.029 0.061 0.019 0.018 0.010 0.023 0.050 0.102

-0.013 0.063 10/06/20 Apples

-0.003 0.011 0.003 0.011

-0.019 0.036 0.000 0.011

-0.007 0.013

-0.036 0.057

-0.020 0.038 C= Control location, Background location Results in bold type are positive.

TABLE 8 FRUITS & VEGETABLES (pCi/g wet wt.)

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

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 1.169 0.322 3.929 0.768

-0.094 0.129

-0.010 0.019

-0.011 0.018 0.023 0.038

-0.008 0.021 10/08/20 3.128 0.445 3.560 0.617 0.045 0.156 0.004 0.017

-0.006 0.016

-0.007 0.038 0.013 0.015 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 0.004 0.054 0.002 0.021 0.003 0.029

-0.006 0.017

-0.190 0.181 0.009 0.052 0.020 0.023 10/08/20

-0.037 0.040 0.013 0.017 0.017 0.029 0.005 0.017

-0.095 0.160 0.039 0.052

-0.002 0.026 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20

-0.003 0.024 0.015 0.019 0.031 0.072

-0.003 0.017

-0.006 0.025

-0.036 0.113 0.070 0.083 10/08/20 0.003 0.019

-0.018 0.016 0.011 0.064

-0.003 0.013

-0.011 0.028 0.009 0.107 0.124 0.081 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 0.487 0.301 4.129 0.698

-0.068 0.144 0.005 0.017 0.001 0.018 0.018 0.034 0.002 0.022 10/08/20 1.089 0.324 3.243 0.622 0.111 0.134 0.015 0.014

-0.013 0.015

-0.011 0.033 0.016 0.019 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20

-0.063 0.050

-0.011 0.019

-0.010 0.032 0.001 0.018 0.163 0.174 0.001 0.052

-0.016 0.021 10/08/20

-0.049 0.038 0.004 0.017

-0.003 0.028

-0.001 0.016

-0.035 0.167 0.018 0.044 0.009 0.024 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 0.000 0.017

-0.006 0.019 0.013 0.066 0.003 0.025 0.021 0.027

-0.022 0.115

-0.009 0.076 10/08/20 0.000 0.021

-0.007 0.015 0.032 0.079 0.009 0.024

-0.012 0.023 0.022 0.093 0.113 0.086 Results in bold type are positive.

LOCATION 10 TABLE 9 BROADLEAF VEGETATION (pCi/g wet wt.)

LOCATION 1

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 0.955 0.331 2.515 0.494 0.018 0.147 0.003 0.018 0.000 0.018

-0.009 0.035

-0.001 0.020 10/08/20 2.343 0.434 2.232 0.483 0.084 0.141 0.009 0.017

-0.011 0.018 0.030 0.034 0.005 0.022 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20

-0.042 0.041 0.002 0.020

-0.004 0.033

-0.005 0.019

-0.042 0.167 0.008 0.052 0.020 0.019 10/08/20

-0.011 0.035 0.014 0.018 0.012 0.033

-0.005 0.017

-0.107 0.162

-0.002 0.048

-0.003 0.024 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20

-0.012 0.020

-0.014 0.019

-0.037 0.071 0.015 0.022 0.003 0.025

-0.007 0.106 0.125 0.082 10/08/20 0.000 0.025 0.007 0.022

-0.013 0.066

-0.003 0.020 0.009 0.028

-0.139 0.108 0.366 0.096 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 0.718 0.274 3.948 0.827 0.013 0.165

-0.004 0.021 0.000 0.024 0.000 0.040

-0.031 0.029 10/08/20 2.239 0.345 3.271 0.629 0.066 0.162

-0.013 0.017 0.007 0.018 0.027 0.036

-0.006 0.020 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20

-0.025 0.053

-0.019 0.024

-0.012 0.036

-0.005 0.019 0.083 0.214

-0.005 0.055

-0.003 0.022 10/08/20

-0.046 0.048

-0.004 0.021

-0.032 0.031 0.000 0.020 0.057 0.149 0.022 0.047

-0.037 0.023 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

06/17/20 0.007 0.024 0.015 0.027 0.023 0.083

-0.012 0.029 0.029 0.027 0.032 0.123 0.045 0.093 10/08/20 0.006 0.021 0.003 0.019 0.000 0.084 0.000 0.018 0.004 0.028

-0.054 0.117 0.107 0.115 C= Control location, Background location Results in bold type are positive.

LOCATION 26C LOCATION 17 TABLE 9 BROADLEAF VEGETATION (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

01/28/20 605 215 11.1 34.8 302 127

-13.6 40.5 1.36 4.13

-1.35 4.32 1.77 9.09 02/25/20 1510 267 10.1 37.1 323 99

-7.58 37.5

-0.01 3.81

-2.40 3.37

-0.17 8.63 03/31/20 682 230 18.6 30.7 292 90

-4.44 30.4 5.71 3.27 0.99 3.84 4.40 7.31 04/28/20 1660 272

-17.6 30.0 270 90 14.2 30.9

-0.55 3.40 2.59 3.25

-2.85 7.67 05/26/20 2360 321

-11.7 42.4 210 100

-7.30 42.9

-0.98 4.77 0.72 4.24

-1.02 8.71 06/30/20 274 200 5.41 31.2 170 103 3.63 32.8

-2.09 4.28 0.12 3.42 0.22 7.15 07/28/20 1170 377 9.06 33.6 233 92

-3.78 39.4

-0.91 3.81

-2.70 3.82 1.73 7.84 08/25/20 87 182

-17.6 24.6 213 81 14.0 25.4 0.77 3.00

-2.69 2.65 0.46 6.28 09/29/20 1200 252 4.40 35.5 279 108

-8.36 36.0

-1.63 5.04

-3.18 4.76

-3.76 8.64 10/27/20 3300 415

-32.7 34.2 279 87

-22.8 32.4 1.02 3.56 0.12 3.70

-5.64 7.59 12/01/20 191 186 8.31 32.4 201 102

-4.97 30.6 0.01 3.80

-0.30 4.11 1.38 6.84 12/28/20

-66 175 11.9 31.6 261 93 0.54 31.3 0.46 3.51

-0.98 3.76 1.87 6.79 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

01/28/20 1.15 5.05

-2.85 9.97

-1.29 5.17

-1.66 7.68

-2.28 4.65

-14.0 35.1

-0.60 11.6 02/25/20

-3.35 4.21

-5.48 9.75

-0.80 3.71 3.97 6.16

-0.32 4.01 17.5 39.8

-5.29 10.6 03/31/20

-1.33 3.66

-0.36 8.31 0.65 3.98 5.48 6.20

-0.11 3.35

-39.0 32.7

-1.70 9.82 04/28/20

-0.62 4.57

-2.77 8.21 2.80 3.66

-0.89 5.96 1.93 3.72 16.5 31.3

-2.46 9.71 05/26/20

-0.44 6.02

-5.78 10.5

-1.89 4.16 0.87 8.65

-0.10 4.10

-14.7 43.9 1.08 12.5 06/30/20 0.28 4.24

-5.69 8.76

-0.45 3.77 1.46 6.39 0.48 3.85 14.6 33.3

-10.4 10.0 07/28/20 2.63 4.41 0.21 9.06

-0.75 3.81 0.04 6.70

-0.27 4.78 4.98 34.6

-2.30 10.6 08/25/20

-1.39 3.05

-5.36 6.89 0.77 2.57 1.41 5.20

-0.10 3.40 4.16 27.1

-0.76 8.43 09/29/20 2.05 4.91

-6.09 9.94

-1.21 4.70 3.68 8.69 2.39 4.69

-17.3 42.7 10.3 13.7 10/27/20 0.74 3.50

-12.8 8.56 2.04 4.51

-1.59 6.47

-3.31 4.05

-15.1 39.2 0.08 10.4 12/01/20 0.45 3.72 1.79 8.43

-0.84 4.06

-5.53 6.33 0.67 3.87

-17.7 33.4

-13.5 10.2 12/28/20

-1.23 4.45 5.07 8.40 1.88 3.81

-2.19 7.16

-1.04 3.99

-10.5 34.8

-4.54 11.3 Results in bold type are positive.

TABLE 10 SEA WATER (pCi/l)

LOCATION 32

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325

COLLECTION DATE I-131 Cs-134 Cs-137 Ba-140 La-140 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

01/28/20

-4.74 4.66 4.58 5.47

-4.83 4.49 4.37 17.2 1.19 5.06

-22.6 20.1 02/25/20

-1.96 5.01

-1.30 4.43 0.74 3.86

-7.13 16.5

-0.63 5.37

-11.9 16.8 03/31/20 1.60 4.55 0.90 3.57 1.90 4.38 1.97 14.8

-1.56 5.19

-1.46 12.1 04/28/20 1.27 3.84

-0.09 3.88

-5.49 4.23 0.39 12.7

-0.65 4.23 6.23 12.9 05/26/20 2.35 5.08

-1.05 5.19

-0.06 4.56 0.32 16.5 3.57 4.87 3.11 20.9 06/30/20 0.22 4.10 0.94 3.99

-4.17 3.80

-4.07 12.5

-0.28 4.27 16.7 14.9 07/28/20 0.98 6.26 6.14 4.18 0.50 4.15

-8.76 16.4 0.60 6.48

-4.32 12.0 08/25/20 2.03 3.40 0.03 3.53 0.46 3.02

-0.94 11.5

-0.44 3.48

-7.05 12.6 09/29/20

-4.42 5.49

-0.47 4.97 0.33 3.64

-2.04 16.0 1.05 3.42

-10.9 17.3 10/27/20

-0.54 4.60 1.26 4.01

-1.34 3.92

-13.0 13.4

-0.61 4.79 26.6 16.7 12/01/20

-1.37 4.85

-0.12 4.12

-2.74 4.12

-1.95 15.2

-2.48 3.84

-1.99 14.3 12/28/20

-1.29 5.08

-0.62 4.46 2.30 4.24 2.19 14.2 3.13 5.30

-4.94 16.1 COLLECTION DATE H-3 Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

03/31/20 52 184 9.27 33.9 258 100

-0.01 36.8

-0.20 3.62 3.27 3.96 0.35 6.53 06/23/20 38 181

-11.3 34.7 228 107

-8.96 31.9

-0.95 3.69 0.08 3.64

-0.13 8.02 09/22/20 72 180 15.0 32.2 288 90

-15.3 36.3 0.53 3.79 0.89 3.95

-1.88 8.03 12/21/20 2

114

-7.15 37.7 199 80

-28.2 33.3

-0.84 3.97

-0.07 3.51 2.11 8.15 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

03/31/20

-3.74 3.80

-9.42 9.36 2.24 3.80 1.11 6.82 0.15 4.14 5.33 35.9 2.98 10.4 06/23/20 1.37 4.35 5.10 10.4 2.36 4.77

-0.74 8.21

-2.23 4.76

-27.5 36.6

-3.67 10.5 09/22/20

-4.31 4.14

-5.43 8.00

-1.00 4.32

-0.93 5.32 1.75 4.21 17.3 35.0 3.25 10.6 12/21/20 2.15 3.03

-4.39 9.56 1.34 4.45

-5.73 7.22

-1.11 4.34

-10.8 33.7

-8.96 10.6 COLLECTION DATE I-131 Cs-134 Cs-137 Ba-140 La-140 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

03/31/20 3.78 5.25 5.16 3.55

-1.16 4.25

-1.34 16.5 1.23 6.01

-0.84 14.2 06/23/20 3.63 4.56 0.68 4.68

-0.97 5.32 11.5 17.8 1.77 5.07 7.21 14.8 09/22/20 2.31 6.66

-0.10 4.11

-6.54 4.40

-9.41 18.9 1.17 5.56 0.46 13.5 12/21/20 1.96 6.33

-1.28 4.35 1.27 4.58 27.1 19.1

-2.70 4.91

-13.0 15.6 C= Control location, Background location Results in bold type are positive.

TABLE 10 SEA WATER (pCi/l)

LOCATION 37C LOCATION 32 Cont'd

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

326

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

31 06/15/20 0.190 0.314 15.57 1.422

-0.112 0.307

-0.017 0.037

-0.004 0.040

-0.022 0.078 31 08/25/20 0.187 0.298 13.37 1.617 0.029 0.301 0.047 0.043

-0.025 0.037

-0.085 0.079 32 06/02/20

-0.048 0.363 14.78 1.505

-0.056 0.353 0.022 0.045 0.011 0.036 0.073 0.101 32 09/15/20 0.257 0.337 20.15 1.765 0.234 0.357 0.003 0.044 0.010 0.045

-0.010 0.093 33 06/17/20

-0.178 0.201 15.51 1.280 0.011 0.184 0.010 0.026

-0.015 0.025 0.051 0.060 33 12/08/20 0.001 0.216 18.51 1.667

-0.027 0.196 0.000 0.030 0.002 0.026

-0.005 0.077 34 06/17/20

-0.003 0.222 13.97 1.408

-0.053 0.184 0.009 0.027 0.000 0.027 0.001 0.070 34 12/08/20

-0.038 0.222 12.35 1.453 0.000 0.195

-0.009 0.027

-0.019 0.027 0.026 0.075 37C 02/21/20 0.051 0.199 13.86 1.466 0.034 0.222 0.000 0.029 0.011 0.028

-0.003 0.064 37C 12/08/20 0.156 0.264 14.91 1.362

-0.220 0.249

-0.022 0.039 0.003 0.033 0.032 0.072 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

31 06/15/20

-0.018 0.034

-0.046 0.093 0.034 0.040 0.040 0.070 0.033 0.039

-0.020 0.325 31 08/25/20 0.042 0.041

-0.218 0.115 0.022 0.042 0.040 0.075 0.012 0.035 0.137 0.339 32 06/02/20 0.013 0.043

-0.244 0.121 0.022 0.050

-0.009 0.080 0.039 0.044 0.194 0.356 32 09/15/20 0.015 0.042

-0.050 0.108

-0.023 0.050

-0.021 0.086

-0.005 0.042 0.276 0.404 33 06/17/20

-0.003 0.024

-0.045 0.061

-0.033 0.025 0.000 0.044 0.012 0.022

-0.092 0.225 33 12/08/20 0.006 0.029

-0.055 0.099 0.028 0.037 0.018 0.056

-0.002 0.023

-0.010 0.224 34 06/17/20 0.001 0.037

-0.036 0.073 0.003 0.027

-0.012 0.049

-0.019 0.023

-0.028 0.228 34 12/08/20

-0.004 0.033

-0.145 0.091 0.019 0.027 0.033 0.052 0.014 0.025

-0.006 0.283 37C 02/21/20 0.027 0.027

-0.073 0.077

-0.015 0.028 0.019 0.049 0.010 0.025

-0.025 0.211 37C 12/08/20 0.009 0.031

-0.156 0.088 0.018 0.031 0.010 0.055 0.006 0.032

-0.053 0.284 C= Control location, Background location Results in bold type are positive.

TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

327

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

31 06/15/20 0.026 0.033

-0.020 0.097 0.021 0.058 0.054 0.045

-0.012 0.035 0.999 0.395 31 08/25/20 0.025 0.039

-0.066 0.096 0.035 0.041 0.078 0.052

-0.008 0.046 1.821 0.452 32 06/02/20 0.030 0.039 0.049 0.105

-0.001 0.069 0.045 0.050

-0.024 0.044 0.982 0.222 32 09/15/20

-0.013 0.039

-0.037 0.116

-0.006 0.061 0.035 0.053

-0.030 0.045 1.075 0.350 33 06/17/20 0.008 0.019 0.013 0.062

-0.019 0.029 0.009 0.029 0.001 0.022 0.247 0.168 33 12/08/20

-0.022 0.026

-0.011 0.066

-0.017 0.028 0.018 0.040 0.005 0.027 0.129 0.138 34 06/17/20

-0.013 0.026 0.022 0.067

-0.034 0.032 0.034 0.032 0.008 0.030 0.251 0.108 34 12/08/20

-0.004 0.026

-0.032 0.076 0.007 0.030 0.020 0.034

-0.003 0.031 0.158 0.127 37C 02/21/20

-0.006 0.025

-0.018 0.060 0.008 0.038 0.016 0.029

-0.002 0.025 0.241 0.114 37C 12/08/20 0.018 0.033

-0.025 0.084

-0.014 0.038 0.039 0.039

-0.011 0.039 0.240 0.158 C= Control location, Background location TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

328

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 03/11/20 0.1288 0.0999 5.3630 0.5025

-0.0696 0.0804 0.0034 0.0098

-0.0037 0.0117 0.0012 0.0262 29 06/15/20 0.0783 0.1019 6.2080 0.5478 0.0157 0.0901

-0.0100 0.0119 0.0076 0.0111 0.0047 0.0274 29 09/17/20 0.0263 0.0984 7.3810 0.5511 0.0352 0.0929

-0.0071 0.0116 0.0022 0.0116 0.0046 0.0279 29 11/10/20 0.1689 0.1377 7.3570 0.8052

-0.0900 0.1247

-0.0121 0.0143

-0.0007 0.0184 0.0464 0.0367 32 03/12/20 0.1301 0.0832 5.3750 0.4285

-0.0097 0.0779

-0.0026 0.0096

-0.0006 0.0099 0.0305 0.0245 32 06/15/20 0.0242 0.1504 7.6660 0.6392

-0.0724 0.1457

-0.0013 0.0171

-0.0163 0.0179 0.0035 0.0367 32 09/17/20 0.0405 0.1026 8.1690 0.6324 0.0976 0.0968

-0.0077 0.0112

-0.0059 0.0115 0.0085 0.0308 32 11/10/20 0.1155 0.1250 8.9230 0.7192 0.0076 0.1308 0.0020 0.0169

-0.0082 0.0134

-0.0269 0.0331 35 03/12/20 0.0613 0.0766 6.7950 0.4801

-0.0378 0.0813 0.0089 0.0105

-0.0036 0.0100 0.0113 0.0224 35 06/15/20 0.1312 0.1182 6.7200 0.7183 0.0207 0.1065

-0.0096 0.0138 0.0031 0.0139 0.0183 0.0310 35 08/25/20 0.0286 0.0776 4.3730 0.4252 0.0502 0.0713 0.0054 0.0092 0.0039 0.0089 0.0055 0.0197 35 11/10/20 0.1244 0.1249 7.9810 0.7850 0.0020 0.1080

-0.0070 0.0108 0.0051 0.0131 0.0068 0.0333 36C 02/21/20 0.2118 0.1146 7.3190 0.5968 0.0303 0.1060

-0.0024 0.0131 0.0062 0.0123

-0.0072 0.0299 36C 06/17/20

-0.0072 0.1044 7.0350 0.6792 0.0716 0.0939 0.0024 0.0129 0.0031 0.0112

-0.0175 0.0237 36C 09/15/20 0.1121 0.0934 4.8780 0.4753

-0.0521 0.0889 0.0051 0.0104

-0.0027 0.0101 0.0076 0.0222 36C 12/08/20 0.2417 0.1581 7.0120 0.6820

-0.0358 0.0953

-0.0020 0.0160 0.0064 0.0133 0.0059 0.0244 C= Control location, Background location Results in bold type are positive.

TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

329

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 03/11/20

-0.0057 0.0107 0.0031 0.0303 0.0029 0.0113

-0.0003 0.0185

-0.0027 0.0109

-0.0730 0.0927 29 06/15/20

-0.0037 0.0115

-0.0079 0.0301 0.0053 0.0111

-0.0096 0.0193 0.0060 0.0105

-0.0303 0.0926 29 09/17/20 0.0146 0.0138 0.0074 0.0294

-0.0026 0.0121

-0.0113 0.0214

-0.0063 0.0120

-0.0802 0.1099 29 11/10/20

-0.0145 0.0202

-0.0411 0.0523 0.0001 0.0166 0.0065 0.0339

-0.0168 0.0144

-0.0539 0.1467 32 03/12/20

-0.0013 0.0101

-0.0279 0.0236 0.0113 0.0102 0.0012 0.0166

-0.0088 0.0094 0.0067 0.0900 32 06/15/20

-0.0022 0.0183 0.0390 0.0477 0.0708 0.0221

-0.0018 0.0277 0.0119 0.0163 0.0572 0.1464 32 09/17/20 0.0063 0.0127

-0.0140 0.0352 0.0037 0.0123

-0.0067 0.0238 0.0027 0.0115

-0.0239 0.1022 32 11/10/20 0.0071 0.0157

-0.0168 0.0413 0.0123 0.0145

-0.0112 0.0277

-0.0055 0.0143 0.0226 0.1350 35 03/12/20

-0.0009 0.0102

-0.0095 0.0257 0.0015 0.0107 0.0097 0.0176 0.0035 0.0097 0.0350 0.0934 35 06/15/20 0.0037 0.0136

-0.0198 0.0313

-0.0007 0.0130 0.0103 0.0243

-0.0095 0.0140

-0.0194 0.1140 35 08/25/20 0.0009 0.0099

-0.0246 0.0248

-0.0044 0.0094

-0.0075 0.0182 0.0102 0.0090

-0.0058 0.0825 35 11/10/20 0.0110 0.0148 0.0265 0.0401

-0.0011 0.0159 0.0008 0.0224

-0.0131 0.0129 0.0206 0.1171 36C 02/21/20 0.0092 0.0133 0.0044 0.0346

-0.0021 0.0124

-0.0099 0.0199

-0.0007 0.0119

-0.0132 0.1130 36C 06/17/20 0.0077 0.0127 0.0125 0.0325 0.0046 0.0100

-0.0022 0.0236

-0.0090 0.0130 0.0099 0.1275 36C 09/15/20

-0.0006 0.0089

-0.0339 0.0296 0.0018 0.0122

-0.0006 0.0187 0.0130 0.0096

-0.0211 0.1059 36C 12/08/20 0.0052 0.0145

-0.0300 0.0434 0.0066 0.0137 0.0130 0.0264

-0.0035 0.0122

-0.0143 0.1193 C= Control location, Background location TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

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330

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 03/11/20

-0.0015 0.0105 0.0032 0.0277 0.0033 0.0166 0.0133 0.0121

-0.0045 0.0116 0.1035 0.0508 29 06/15/20 0.0011 0.0108

-0.0046 0.0263 0.0154 0.0140 0.0049 0.0125 0.0001 0.0128 0.1267 0.0537 29 09/17/20 0.0005 0.0116

-0.0046 0.0292 0.0212 0.0176 0.0021 0.0122 0.0061 0.0120 0.0934 0.0729 29 11/10/20

-0.0096 0.0163 0.0525 0.0391 0.0111 0.0153

-0.0066 0.0194 0.0171 0.0183 0.0938 0.0760 32 03/12/20

-0.0013 0.0094

-0.0026 0.0265 0.0090 0.0144 0.0056 0.0113 0.0064 0.0107 0.0379 0.0435 32 06/15/20 0.0120 0.0148

-0.0216 0.0484 0.0067 0.0228 0.0114 0.0179

-0.0156 0.0176 0.0350 0.0724 32 09/17/20

-0.0023 0.0121 0.0460 0.0309 0.0375 0.0179

-0.0009 0.0128 0.0136 0.0124 0.0763 0.0551 32 11/10/20 0.0016 0.0139

-0.0481 0.0421

-0.0025 0.0161 0.0077 0.0160

-0.0038 0.0168 0.0978 0.0731 35 03/12/20

-0.0025 0.0086 0.0064 0.0244 0.0032 0.0135 0.0017 0.0120 0.0018 0.0093 0.0988 0.0449 35 06/15/20

-0.0005 0.0128

-0.0124 0.0349 0.0034 0.0138

-0.0009 0.0151

-0.0009 0.0137 0.0581 0.0609 35 08/25/20 0.0022 0.0090 0.0059 0.0259 0.0097 0.0105 0.0101 0.0108

-0.0029 0.0101 0.0626 0.0436 35 11/10/20 0.0037 0.0131 0.0086 0.0344

-0.0031 0.0126 0.0030 0.0178 0.0038 0.0166 0.1467 0.0703 36C 02/21/20

-0.0076 0.0127

-0.0059 0.0316 0.0046 0.0215 0.0088 0.0129 0.0060 0.0137 0.0567 0.0508 36C 06/17/20

-0.0043 0.0116

-0.0097 0.0293 0.0076 0.0131

-0.0007 0.0155 0.0005 0.0137 0.1715 0.0575 36C 09/15/20 0.0041 0.0102 0.0060 0.0286 0.0027 0.0121 0.0116 0.0122

-0.0006 0.0127 0.0458 0.0472 36C 12/08/20

-0.0055 0.0131 0.0037 0.0362 0.0034 0.0154 0.0016 0.0139

-0.0022 0.0148 0.0876 0.0710 C= Control location, Background location TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

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331

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 06/15/20

-0.002 0.270 3.507 0.927

-0.236 0.279

-0.018 0.031

-0.049 0.036 0.003 0.060 29 07/30/20

-0.059 0.259 3.694 0.948

-0.073 0.254 0.021 0.034 0.003 0.030 0.011 0.073 35 05/26/20

-0.039 0.216 2.868 0.727 0.135 0.251 0.005 0.027 0.007 0.029 0.025 0.059 35 07/30/20

-0.077 0.284 2.838 0.946 0.008 0.321 0.040 0.037 0.024 0.037 0.070 0.083 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 06/15/20

-0.009 0.030

-0.017 0.096 0.010 0.038

-0.008 0.043 0.022 0.030 0.055 0.318 29 07/30/20

-0.035 0.034 0.049 0.091 0.015 0.037 0.011 0.055 0.018 0.035 0.231 0.298 35 05/26/20 0.021 0.029

-0.040 0.068 0.005 0.026 0.010 0.054

-0.001 0.030 0.092 0.223 35 07/30/20 0.010 0.040

-0.032 0.081

-0.005 0.038 0.043 0.064

-0.012 0.034

-0.150 0.348 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 06/15/20

-0.028 0.034

-0.057 0.093 0.001 0.044 0.030 0.043

-0.006 0.039 0.010 0.140 29 07/30/20

-0.009 0.031 0.091 0.086 0.023 0.049

-0.001 0.039

-0.004 0.038

-0.019 0.118 35 05/26/20

-0.003 0.023 0.061 0.067 0.019 0.052 0.001 0.030

-0.018 0.026 0.054 0.110 35 07/30/20

-0.029 0.039

-0.010 0.087

-0.023 0.046

-0.017 0.033 0.006 0.039

-0.017 0.133 Results in bold type are positive.

TABLE 13 FISH (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

332

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

31 06/25/20 0.258 0.238 2.297 0.708 0.171 0.233

-0.007 0.031 0.010 0.029 0.033 0.068 31 12/08/20

-0.068 0.252 1.512 0.670

-0.094 0.229 0.001 0.028 0.008 0.029 0.024 0.052 89C 05/26/20

-0.075 0.240 1.633 0.748

-0.053 0.254

-0.002 0.028

-0.018 0.032 0.007 0.069 89C 09/24/20 0.082 0.409 1.908 0.892

-0.353 0.376

-0.001 0.047

-0.004 0.043 0.024 0.090 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

31 06/25/20

-0.002 0.030 0.014 0.080

-0.021 0.027

-0.026 0.053 0.002 0.029

-0.030 0.247 31 12/08/20 0.007 0.032

-0.019 0.067

-0.004 0.030

-0.028 0.053

-0.007 0.030 0.213 0.295 89C 05/26/20

-0.017 0.033

-0.039 0.045

-0.012 0.029 0.000 0.059 0.004 0.030 0.120 0.308 89C 09/24/20 0.006 0.036

-0.074 0.097 0.021 0.043 0.011 0.083 0.024 0.037

-0.104 0.432 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

31 06/25/20

-0.009 0.033 0.001 0.067 0.004 0.050

-0.004 0.032 0.006 0.037

-0.094 0.113 31 12/08/20 0.027 0.031 0.024 0.085

-0.001 0.028 0.007 0.037 0.021 0.035 0.015 0.105 89C 05/26/20

-0.002 0.028 0.054 0.078

-0.007 0.053 0.003 0.036

-0.006 0.030 0.064 0.126 89C 09/24/20 0.029 0.042 0.016 0.118

-0.030 0.077 0.055 0.052 0.017 0.047 0.004 0.165 Results in bold type are positive.

C= Control location, Background location TABLE 14 OYSTERS (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

333

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 06/02/20 0.012 0.386 1.805 1.106

-0.310 0.459 0.031 0.051 0.019 0.054 0.002 0.091 29 09/25/20 0.059 0.286 2.431 0.920

-0.030 0.318 0.029 0.035

-0.011 0.038

-0.042 0.071 31 06/02/20 0.063 0.188 2.204 0.725

-0.016 0.262 0.022 0.025 0.004 0.021

-0.016 0.047 31 10/15/20

-0.060 0.253 2.087 0.866 0.144 0.240 0.026 0.027

-0.014 0.030 0.034 0.048 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 06/02/20 0.007 0.034

-0.019 0.106 0.017 0.054 0.035 0.090

-0.032 0.053

-0.214 0.482 29 09/25/20

-0.004 0.040

-0.026 0.087 0.029 0.036 0.089 0.075 0.007 0.043

-0.107 0.301 31 06/02/20

-0.002 0.019

-0.024 0.063

-0.025 0.025 0.010 0.043

-0.015 0.028 0.058 0.238 31 10/15/20

-0.026 0.037 0.009 0.054 0.003 0.028

-0.015 0.055 0.004 0.026

-0.336 0.320 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

29 06/02/20 0.005 0.042

-0.015 0.128

-0.023 0.095

-0.040 0.063

-0.033 0.046

-0.015 0.196 29 09/25/20

-0.017 0.033

-0.074 0.116

-0.026 0.063

-0.047 0.047 0.013 0.034

-0.027 0.149 31 06/02/20

-0.005 0.021

-0.012 0.080 0.022 0.044

-0.014 0.025 0.008 0.027 0.074 0.098 31 10/15/20 0.013 0.029

-0.043 0.070 0.019 0.042

-0.006 0.039 0.008 0.033

-0.049 0.087 Results in bold type are positive.

TABLE 15 CLAMS (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

334

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

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

35 05/11/20

-0.037 0.206 2.861 0.767

-0.170 0.233 0.029 0.028

-0.012 0.025

-0.036 0.054 35 07/30/20

-0.197 0.349 3.131 1.073

-0.077 0.299

-0.016 0.037

-0.011 0.038

-0.019 0.063 89C 02/25/20

-0.043 0.271 1.984 0.745

-0.165 0.227 0.016 0.033 0.017 0.028 0.063 0.062 89C 08/19/20

-0.182 0.246 2.958 1.000 0.090 0.226

-0.012 0.032 0.026 0.033 0.001 0.039 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

35 05/11/20 0.014 0.029

-0.019 0.067 0.008 0.027

-0.018 0.046 0.006 0.029 0.065 0.259 35 07/30/20 0.015 0.049

-0.017 0.084 0.020 0.041

-0.009 0.074 0.010 0.043

-0.218 0.403 89C 02/25/20 0.020 0.041

-0.012 0.082

-0.002 0.033 0.029 0.053

-0.011 0.029 0.152 0.270 89C 08/19/20

-0.028 0.041

-0.092 0.073

-0.001 0.029

-0.007 0.050 0.004 0.030

-0.186 0.301 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

(+/-)

35 05/11/20 0.014 0.027

-0.014 0.064

-0.014 0.046 0.006 0.028

-0.042 0.031

-0.036 0.104 35 07/30/20 0.001 0.038

-0.012 0.109

-0.044 0.062

-0.009 0.041

-0.011 0.042 0.099 0.171 89C 02/25/20

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TABLE 16 LOBSTERS (pCi/g wet wt.)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 41

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 and broadleaf vegetation and in some fucus samples. K-40 and Ac-228 are two common terrestrial isotopes. K-40 was not seen in air or well water samples but was observed in almost every other type of sample. Ac-228 was observed in one sediment. Cs-137 and Sr-90 from atmospheric nuclear weapons testing in the 1960s have 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. During 2020, there were two soil samples that detected Cs-137 just above the LLD. Based on sample location, it is not unexpected to identify the presence of Cs-137 in undisturbed soil22.

The remaining REMP samples obtained during 2020 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-804 ASx 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 2005. Three containers were loaded in 2006, three in 2007, three in 2009, three in 2010, seven in 2015, six in 2016, three in 2018, and seven in 2019. None were loaded in 2020.

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 2020, 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 2020 was 0.03 mrem/year, which is below the 25 mrem/year limit per 40.190 CFR.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 42

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), Corey Road (Location 48), and Site Switchyard Fence (Location 73) 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 R/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 onsite (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 2009 to 2020 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).

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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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 2020

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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/m3 (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 2020

45

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 I-131 every two weeks. No detectable levels of I-131 were seen in the 2020 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 they were 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 detected in two soil samples. 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.

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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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 2020 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 2020, 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 2020. 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 was the only isotope 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 and Ac-228 at levels consistent with previous years. 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 2020 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. Its 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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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, Giants 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 2020 MPS had two outages requiring the processing and subsequent discharge of processed refueling water, which explains the slightly elevated H-3 activity values in the second and fourth quarters of 2020. The highest quarterly average H-3 value in 2020 for seawater was 1,431 pCi/l, which is well below the drinking water limit established by the Environmental Protection Agency (EPA) of 20,000 pCi/l. The total annual exposure from the liquid discharge pathway for 2020 was 0.001 mrem/yr.

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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4.11 Bottom Sediment (Table 11)

There was no station related radioactivity detected in bottom sediment samples in 2020.

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, I-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. The stocked trays are kept at sampling areas and represent conditions in those areas. Due to safety concerns, Location #32 was moved over eight years ago to a more accessible area in the middle of the quarry. Although it is labeled as vicinity of the discharge, it was previously located at the end of the quarry. The near-field dilution factor for liquid discharges from the MPS Quarry discharge is a factor of 3. Obtaining oyster sampling has presented challenges in obtaining the sample size required for analysis. In 2020 there were no challenges in obtaining oyster samples and four samples were obtained.

Naturally occurring K-40 is seen in most samples. MPS related Ag-110m and Zn-65 in oysters collected at Location #32 have been seen in the past. 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. As seen in the past, no plant related radioactivity was detected in oysters in 2020.

4.15 Clams (Table 15)

In 2020, only the naturally occurring K-40 was detected in the collected samples.

4.16 Lobsters (Table 16)

In 2020, only the naturally occurring K-40 was detected in the collected samples

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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 Stations 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 Stations 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

A1

APPENDIX A LAND USE CENSUS FOR 2020

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

A2

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 2020 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.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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Table A-1 2020 Survey Downwind Direction Resident/Garden1 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 SE2 N/A N/A SSE2 N/A N/A S2 N/A N/A SSW2 N/A N/A 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 N/A because they are over water.

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

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Table A-2 Milk and other foods within Ten miles of Millstone - 2020 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 ENE 3.0 Secchiaroli Farms Waterford Has pigs, fed nonlocal sources and have concrete pens WNW 5.0 Four Mile River Farm Old Lyme Eggs, Meat NW 5.2 Scott's Yankee Farmer East Lyme Fruits, vegetables, and cider NNW 5.3 White Gate Farm East Lyme Vegetables, Herbs, Eggs, Meat, Nursery and Flowers NNW 6.24 Trinity Farm Waterford Registered AGDA member but does 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 NE 8.3 Red Fence Farm Groton Fruits, vegetables, cows, goats, and pig. Cows and goats currently not producing milk NW 9.4 Macwilliam Lyme Has goats, does not sell commercially

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

A5

Figure A-1 Farms and Goats Products within ten miles of Millstone

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

A6

Figure A-2 Shellfish Beds in Vicinity of Millstone

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020

A7

Figure A-3 Saltwater Fishing Resource Map

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Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B1

APPENDIX B

SUMMARY

OF INTERLABORATORY COMPARISONS

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B2

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 TBEs 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 ERAs evaluation report provides an acceptance range for control and warning limits with associated flag values. ERAs acceptance limits are established per the US EPA, National Environmental Laboratory Accreditation Conference (NELAC), state-specific Performance Testing (PT) program requirements or ERAs 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 MAPEPs 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, 126 out of 133 analyses performed met the specified acceptance criteria.

Seven analyses did not meet the specified acceptance criteria for the following reasons and were addressed through the TBE Corrective Action Program. A summary is found below:

1. The MAPEP February 2020 AP U-233/234 and U-238 results were evaluated as Not Acceptable. The reported value for U-233/234 was 0.0416 +/- 0.0102 Bq/sample and the known result was 0.075 Bq/sample (acceptance range 0.053 - 0.098). The reported value for U-238 was 0.0388 +/- 0.00991 Bq/sample and the known result was 0.078 Bq/sample (acceptance range 0.055 - 0.101). This sample was run as the workgroup duplicate and had RPDs of 10.4% (U-234) and 11.7% (U-238). After the known results were obtained, the sample was relogged. The filter was completely digested with tracer added originally; the R1 results were almost identical. It was concluded that the recorded tracer amount was actually double, causing the results to be skewed. Lab worksheets have been modified to verify actual tracer amount vs. LIMS data. TBE changed vendors for this cross-check to ERA MRAD during the 2nd half of 2020. Results were acceptable at 97.8% for U-234 and 106% for U-238. (NCR 20-13)

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B3

2. The Analytics September 2020 milk Sr-89 result was evaluated as Not Acceptable. The reported value was 62.8 pCi/L and the known result was 95.4 (66%). All QC data was reviewed and there were no anomalies. This was the first failure for milk Sr-89 since 2013 and there have only been 3 upper/lower boundary warnings since that time. It is believed that there may have been some loss during the sample prep (ashing). The December 2020 result was at 92% of the known. (NCR 20-19)
3. The ERA October 2020 water I-131 result was evaluated as Not Acceptable. The reported value was 22.9 pCi/L and the known result was 28.2 (acceptance range 23.5 -

33.1). The reported result was 81% of the known, which passes TBE QC criteria. This was the first failure for water I-131. (NCR 20-17)

4. The ERA October 2020 water Gross Alpha and Gross Beta results were evaluated as Not Acceptable. The reported/acceptable values and ranges are as follows:

Reported Known Range Gross Alpha 40.0 26.2 13.3 - 34.7 Gross Beta 47.5 69.1 48.0 - 76.0 All QC data was reviewed with no anomalies and a cause for failure could not be determined. This was the first failure for water Gross Beta. A Quick Response follow-up cross-check was analyzed as soon as possible with acceptable results at 96.8% for Gross Alpha and 102% for Gross Beta. (NCR 20-18)

5. The MAPEP August 2020 soil Ni-63 result was evaluated as Not Acceptable. The reported value was 438 +/- 21.1 Bq/kg and the known result was 980 Bq/kg (acceptance range 686 - 1274). It is believed that some Ni-63 loss may have occurred during the sample prep. This investigation is still on-going at this time. (NCR 20-20)

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

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B4

Month/Year Identification Number Matrix Nuclide Units TBE Value Known Value (a)

Ratio of TBE to Known Result Evaluation (b)

September 2020 E13247 Milk Sr-89 pCi/L 62.8 95.4 0.66 N(1)

Sr-90 pCi/L 12.0 12.8 0.94 A

E13248 Milk Ce-141 pCi/L 156 150 1.04 A

Co-58 pCi/L 172 180 0.96 A

Co-60 pCi/L 369 379 0.97 A

Cr-51 pCi/L 372 372 1.00 A

Cs-134 pCi/L 171 200 0.85 A

Cs-137 pCi/L 241 250 0.96 A

Fe-59 pCi/L 217 200 1.08 A

I-131 pCi/L 84.6 95.0 0.89 A

Mn-54 pCi/L 175 180 0.97 A

Zn-65 pCi/L 252 270 0.93 A

E13249 Charcoal I-131 pCi 70.2 75.8 0.93 A

E13250 AP Ce-141 pCi 101 101 1.00 A

Co-58 pCi 111 120 0.92 A

Co-60 pCi 249 254 0.98 A

Cr-51 pCi 287 249 1.15 A

Cs-134 pCi 114 134 0.85 A

Cs-137 pCi 159 168 0.95 A

Fe-59 pCi 127 134 0.95 A

Mn-54 pCi 114 121 0.94 A

Zn-65 pCi 168 181 0.93 A

E13251 Soil Ce-141 pCi/g 0.241 0.191 1.26 W

Co-58 pCi/g 0.211 0.228 0.93 A

Co-60 pCi/g 0.466 0.481 0.97 A

Cr-51 pCi/g 0.450 0.472 0.95 A

Cs-134 pCi/g 0.273 0.254 1.07 A

Cs-137 pCi/g 0.370 0.390 0.95 A

Fe-59 pCi/g 0.233 0.254 0.92 A

Mn-54 pCi/g 0.217 0.229 0.95 A

Zn-65 pCi/g 0.368 0.343 1.07 A

E13252 AP Sr-89 pCi 79.9 100.0 0.80 A

Sr-90 pCi 12.1 13.4 0.90 A

(a) The Analytics known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) Analytics evaluation based on TBE internal QC limits:

A = Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within 0.70-0.80 or 1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of < 0.70 and > 1.30 (1) See NCR 20-19 A.1 Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B5

Month/Year Identification Number Matrix Nuclide Units TBE Value Known Value (a)

Ratio of TBE to Known Result Evaluation (b)

December 2020 E13254 Milk Sr-89 pCi/L 82.2 89.7 0.92 A

Sr-90 pCi/L 12.4 13.0 0.96 A

E13255 Milk Ce-141 pCi/L 91.1 100 0.91 A

Co-58 pCi/L 77.5 84.3 0.92 A

Co-60 pCi/L 147 152 0.97 A

Cr-51 pCi/L 259 253 1.02 A

Cs-134 pCi/L 97.1 108 0.90 A

Cs-137 pCi/L 117 127 0.92 A

Fe-59 pCi/L 114 112 1.02 A

I-131 pCi/L 84.3 91.9 0.92 A

Mn-54 pCi/L 137 143 0.96 A

Zn-65 pCi/L 175 190 0.92 A

E13256 Charcoal I-131 pCi 70.2 78.2 0.90 A

E13257A AP Ce-141 pCi 67.4 74.6 0.90 A

Co-58 pCi 57.9 62.9 0.92 A

Co-60 pCi 108 113 0.95 A

Cr-51 pCi 162 189 0.86 A

Cs-134 pCi 68.1 80.4 0.85 A

Cs-137 pCi 82.4 95.0 0.87 A

Fe-59 pCi 80.5 83.7 0.96 A

Mn-54 pCi 102 107 0.95 A

Zn-65 pCi 115 142 0.81 A

E13258 Soil Ce-141 pCi/g 0.167 0.170 0.98 A

Co-58 pCi/g 0.125 0.143 0.87 A

Co-60 pCi/g 0.245 0.257 0.95 A

Cr-51 pCi/g 0.393 0.429 0.92 A

Cs-134 pCi/g 0.147 0.183 0.80 A

Cs-137 pCi/g 0.260 0.288 0.90 A

Fe-59 pCi/g 0.199 0.190 1.05 A

Mn-54 pCi/g 0.229 0.243 0.94 A

Zn-65 pCi/g 0.320 0.322 0.99 A

E13259 AP Sr-89 pCi 85.0 78.6 1.08 A

Sr-90 pCi 13.1 11.4 1.15 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 A.1 Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B6

Month/Year Identification Number Matrix Nuclide Units TBE Value Known Value (a)

Acceptance Range Evaluation (b)

February 2020 20-GrF42 AP Gross Alpha Bq/sample 0.676 1.24 0.37 - 2.11 A

Gross Beta Bq/sample 2.03 2.00 1.00 - 3.00 A

20-MaS42 Soil Ni-63 Bq/kg 0.01 (1)

A Sr-90 Bq/kg 348 340 238 - 442 A

20-MaW42 Water Ni-63 Bq/L 11.6 11.1 7.8 - 14.4 A

Pu-238 Bq/L 0.926 0.94 0.66 - 1.22 A

Pu-239/240 Bq/L 0.712 0.737 0.516 - 0.958 A

20-RdF42 AP U-234/233 Bq/sample 0.0416 0.075 0.053 - 0.098 N(3)

U-238 Bq/sample 0.0388 0.078 0.055 - 0.101 N(3) 20-RdV42 Vegetation Cs-134 Bq/sample 3.23 3.82 2.67 - 4.97 A

Cs-137 Bq/sample 2.64 2.77 1.94 - 3.60 A

Co-57 Bq/sample 0.0281 (1)

A Co-60 Bq/sample 2.62 2.79 1.95 - 3.63 A

Mn-54 Bq/sample 4.3 4.58 3.21 - 5.95 A

Sr-90 Bq/sample 0.396 0.492 0.344 - 0.640 A

Zn-65 Bq/sample 3.93 3.79 2.65 - 4.93 A

August 2020 20-GrF43 AP Gross Alpha Bq/sample 0.267 0.528 0.158 - 0.989 A

Gross Beta Bq/sample 0.939 0.915 0.458 - 1.373 A

20-MaS43 Soil Ni-63 Bq/kg 438 980 686 - 1274 N(4)

Tc-99 Bq/kg 1.11 (1)

A 20-MaW43 Water Ni-63 Bq/L 0.175 (1)

A Tc-99 Bq/L 8.8 9.4 6.6 - 12.2 A

20-RdV43 Vegetation Cs-134 Bq/sample 3.635 4.94 3.46 - 6.42 W

Cs-137 Bq/sample 0.0341 (1)

A Co-57 Bq/sample 5.855 6.67 4.67 - 8.67 W

Co-60 Bq/sample 3.122 4.13 2.89 - 5.37 W

Mn-54 Bq/sample 4.524 5.84 4.09 - 7.59 A

Sr-90 Bq/sample 1.01 1.39 0.97 - 1.81 W

Zn-65 Bq/sample 4.706 6.38 4.47 - 8.29 W

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

A = Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within 0.70-0.80 or 1.20-1.30 N = Not Acceptable - reported result falls outside the ratio limits of < 0.70 and > 1.30 (1) False positive test (2) Sensitivity evaluation (3) See NCR 20-13 (4) See NCR 20-20 A.2 DOE's Mixed Analyte Performance Evaluation Program (MAPEP)

Teledyne Brown Engineering Environmental Services

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 B7

Month/Year Identification Number Matrix Nuclide Units TBE Value Known Value (a)

Acceptance Limits Evaluation (b)

March 2020 MRAD-32 Water Am-241 pCi/L 52.5 45.3 31.1 - 57.9 A

Fe-55 pCi/L 155 152 89.3 - 221 A

Pu-238 pCi/L 34.0 36.4 21.9 - 47.2 A

Pu-239 pCi/L 30.9 33.6 20.8 - 41.4 A

April 2020 RAD-121 Water Ba-133 pCi/L 41.8 41.8 34.0- 46.7 A

Cs-134 pCi/L 42.9 46.3 37.1 - 50.9 A

Cs-137 pCi/L 226 234 211 - 259 A

Co-60 pCi/L 52.4 50.3 45.3 - 57.9 A

Zn-65 pCi/L 83.3 86.8 78.1 - 104 A

GR-A pCi/L 20.1 23.6 11.9 - 31.6 A

GR-B pCi/L 45.6 60.5 41.7 - 67.2 A

U-Nat pCi/L 18.45 18.6 14.9 - 20.9 A

H-3 pCi/L 14200 14100 12300 - 15500 A

Sr-89 pCi/L 58.0 60.1 48.3 - 67.9 A

Sr-90 pCi/L 34.1 44.7 33.0 - 51.2 A

I-131 pCi/L 27.4 28.9 24.1 - 33.8 A

September 2020 MRAD-33 Soil Sr-90 pCi/Kg 4360 4980 1550 - 7760 A

AP Fe-55 pCi/Filter 189 407 149 - 649 A

U-234 pCi/Filter 17.9 18.3 13.6 - 21.4 A

U-238 pCi/Filter 19.1 18.1 13.7 - 21.6 A

Water Am-241 pCi/L 160 176 121 - 225 A

Fe-55 pCi/L 299 298 175 - 433 A

Pu-238 pCi/L 200 191 115 - 247 A

Pu-239 pCi/L 105 100 61.9 - 123 A

October 2020 RAD-123 Water Ba-133 pCi/L 37.1 37.0 29.8 - 41.6 A

Cs-134 pCi/L 50.6 52.7 42.5 - 58.0 A

Cs-137 pCi/L 131 131 118 - 146 A

Co-60 pCi/L 62.9 60.5 54.4 - 69.1 A

Zn-65 pCi/L 167 162 146 - 191 A

GR-A pCi/L 40.0 26.2 13.3 - 34.7 N(1)

GR-B pCi/L 47.5 69.1 48.0 - 76.0 N(1)

U-Nat pCi/L 17.2 20.3 16.3 - 22.7 A

H-3 pCi/L 23800 23200 20,300 - 25,500 A

Sr-89 pCi/L 41.1 43.3 33.4 - 50.5 A

Sr-90 pCi/L 28.5 30.2 22.0 - 35.0 A

I-131 pCi/L 22.9 28.2 23.5 - 33.1 N(2)

November 2020 QR111920K Water GR-A pCi/L 50.7 52.4 27.3 - 65.6 A

GR-B pCi/L 24.9 24.3 15.0 - 32.3 A

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

(b) ERA evaluation:

A = Acceptable - Reported value falls within the Acceptance Limits N = Not Acceptable - Reported value falls outside of the Acceptance Limits (1) See NCR 20-18 (2) See NCR 20-17 A.3 ERA Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 C1

APPENDIX C ERRATUM

Dominion Energy Nuclear Connecticut, Inc. Annual Radiological Environmental Millstone Power Station Operating Report 2020 C2

Erratum-Correction to Previously Published Annual Radiological Environmental Operating Report In the 2020 Annual Radiological Environmental Operating Report there were no correction identified to previously published Annual Radiological Environmental Operating Reports.