ML20120A430

Transmittal of 2019 Annual Radiological Environmental Operating Report

ML20120A430
Person / Time
Site:	Millstone
Issue date:	04/28/2020
From:	Armstrong L Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
20-148
Download: ML20120A430 (91)

Text

Dominion Energy Nuclear Connecticut, Inc.

,,., Dominion Rt 156, Rope Ferry Road, Waterford, CT 06385 Dominion Energy.com #

£ Energy*

U.S. Nuclear Regulatory Commission Serial No.20-148 Attention: Document Control Desk MPS Lie/LO RO Washington, DC 20555-0001 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNITS 1, 2, AND 3 2019 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT This letter transmits the Annual Radiological Environmental Operating Report for the Millstone Power Station, for the period January 2019 through December 2019. 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,

~ Chv-n_~

Director, Nuclear Station Safety and Licensing

Serial No.20-148 2019 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.20-148 2019 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.20-148 2019 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.20-148 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 ATTACHMENT 1 2019 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MILLSTONE POWER STATION UNITS 1, 2, AND 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DENC)

Millstone Power Station 2019 Radiological Environmental Operating Report January 1, 2019 - December 31, 2019 Dominion Nuclear Connecticut, Inc.

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

ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MILLSTONE POWER STATION RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM 2019 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 Nuclear Connecticut, Inc.

Waterford, Connecticut

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

~ 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. PROGRAM DESCRIPTION .................................................................................. 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 2019 ...................................................... A-1 APPENDIX B -

SUMMARY

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

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station EXECUTIVE

SUMMARY

INTRODUCTION This report summarizes the results of the Radiological Environmental Monitoring Program (REMP) conducted in the vicinity of the Millstone Nuclear Power Station (MPS) during the period from January 1 to December 31, 2019. 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 2019, there were 546 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 2019 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 result.

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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 2019, 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 2019 was approximately 0.234 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 2019 REMP for MPS resulted in the collection and analysis of 718 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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

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 2019 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, 2019.

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

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

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

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

Radioactive material exists naturally and has always been a part of our environment. The earth's crust, for example, contains radioactive uranium, radium, thorium, and potassium.

Some radioactivity is a result of fallout from nuclear weapons testing. Examples of radioactive fallout that could be present in environmental samples are cesium-137 and strontium-90.

Some examples of radioactive materials released from a nuclear power station are hydrogen-3 (tritium), cesium-137, iodine-131, strontium-90, and cobalt-60.

1-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 Radiation Dose Radiation Dose Source (mrem/year) Source (mrem/year)

Internal, inhalation(2) 228 Medical(3) 300 External, space 33 Consumer(4) 13 Internal, ingestion 29 Industrial, security, 0.3 educational, research External, terrestrial 21 Occupational 0.5 Weapons Fallout <1 Nuclear Power Stations <1 Approximate Total 311 Approximate Total 314 (1) information from References 3 and 4 (2) from radon and thoron (3) includes computerized tomography (147 mrem), nuclear medicine (77 mrem), interventional fluoroscopy (43 mrem) and conventional radiography and fluoroscopy (33 mrem)

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

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 5 kilometers (three miles) west of New London, Connecticut. Commercial operation of MPS2 began in December 1975 and MPS3 in May 1986.

MPS was operational during most of 2019, with the exception of the downpowered event in April through May for MPS2 due to emergent repair activities and refueling outage in April for MPS3. The annual capacity factor for MPS2 was 95.04% and for MPS3 was 89.58%.

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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 1-4

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 1-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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).

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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:

x reactor water cleanup system; x liquid radioactive waste treatment system; x sampling and analysis of the liquid radioactive waste tanks; and, x 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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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.

1-10

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station EXAMPLES OF Millstones RADIATION EXPOSURE PATHWAYS Figure 1.6-1: Radiation Exposure Pathways 1-11

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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.

1-12

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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.

1-13

DominionNuclearConnecticut,Inc. AnnualRadiologicalEnvironmentalOperatingReport2019

MillstonePowerStation

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.

 21

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Table 2.1-1 Environmental Monitoring Program Sampling Types and Locations Distance, No.- Direction From Type* Location Name 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 1

35-I Niantic Bay 0.5 Mi, SSW to W Lobster, Fish , 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 2.1 Mi, W TLD

& Terrace Ave 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 1.4 Mi, NNE TLD 55-I Waterford - Magonk Point 1.8 Mi, ESE TLD 56-I New London - Ocean&Mott 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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Table 2.1-1 Environmental Monitoring Program Sampling Types and Locations (Continues)

No.- Distance, Direction From Type1 Location Name 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 Waterford - Gardiners Wood &

63-I 0.8 Mi, NE TLD Jordon Cove 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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Table 2.1-2 Required Sampling Frequency & Type of Analysis Exposure Pathway No. of Sampling & Collection Frequency Type of Analysis and/or Sample Locations

1. Gamma Dose - 391 Quarterly Gamma Dose - Quarterly Environmental TLD

2. Airborne Particulate 8 Continuous sampler - filter change Gross Beta - Every two weeks 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 I-131 - Every two weeks change every two weeks

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

5. Reserved

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

Quarterly at control location -

Composite of 6 weekly grab samples.

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

8. Bottom Sediment 5 Semiannual Gamma Isotopic on each sample

9. Soil 3 Annually Gamma Isotopic on each sample

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

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

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

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

Footnotes

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

- Oysters were previously Sample#12, REMODCM revision 27.

2-4

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Figure 2.1-1, Inner TLD, Air, Grass, Soil, and Aquatic Locations 2-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Figure 2.1-2, Outer TLD and Aquatic Locations 2-6

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 2.2 Samples Collected During Report Period The following table summarizes the number of samples of each type collected and analyzed during 2019:

Table 2.2-1 REMP Samples Collected in 2019 Number of Number of Technical Technical Number of Extra Sample Type Specification Specification Samples Analyzed Required Samples Required Samples Analyzed Gamma Exposure 156 156 16 (Environmental TLD)

Air Particulates 216 216 0 Air Iodine 216 216 0 Soil 3 3 0 Milk (cow) 0 0 0 Milk (goat) 0 0 0 Well Water 12 12 24 Vegetation 10 10 7 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 667 667 51 2.3 Required Samples Not Collected During the Report Period During 2019 all required samples were obtained as listed in Table 2.2-1.

Prior to 2018, milk sampling was performed as an extra sample. The 2019 Land Use Census did not locate any milk farms producers within ten miles of Millstone Power Station. As a substitute for milk samples, strontium analysis of air samples and gamma analysis of broad leaf vegetation were performed.

2-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

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 119 out of 129 quality assurance analyses performed met the specified acceptance criteria. Ten 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 ten analysis failures were found to adversely affect any of Millstone samples results and data accuracy.

3-1

DominionNuclearConnecticut,Inc. AnnualRadiologicalEnvironmentalOperatingReport2019

MillstonePowerStation

RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2019 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 Gam m a 172 NA 156 9 0.04 Mi. 4 16 Radiation Dose 7.7 W 11.2 7.9 TLD (uR/hr) (4.5-11.3) (11.1-11.3) (5.7-9.5)

Air Iodine I-131 216 0.07 189 NA NA <LLD 27

( pCi/m 3 ) <LLD <LLD Air Particulate GR-B 216 0.01 189 10 1.2 Mi. 27 27

( pCi/m 3 ) 0.012 E 0.012 0.012 (0.007-0.017) (0.008-0.017) (0.007-0.017)

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 3 0.3 Mi. 4 4 0.1124 NE 0.1254 0.1035 (0.0731-0.1657) (0.0744-0.1657) (0.0819-0.1269)

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 13.295 NE 14.900 14.900 (13.200-13.390) (<LLD-14.900) (<LLD-14.900)

CS-137 0.18 2 4 1.0 Mi. 1 1 0.250 N 0.312 0.154 (0.189-0.312) (<LLD-0.312) (<LLD-0.154)

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 f or collection in 2019, as a substitute, K-40 NA Strontium Analysis of Air Particulate f ilters w as perf ormed Other Note 4 Gammas



 32

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2019 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 2019, as a substitute, K-40 NA Strontium Analysis of Air Particulate filters w as 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 9 (pCi/g wet) Be-7 NA 1 25 Within 10 Miles 1 4 0.928 0.928 <LLD

(<LLD-0.928) (<LLD-0.928)

K-40 NA 5 25 Within 10 Miles 5 4 2.498 2.498 1.655 (1.032-5.523) (1.032-5.523) (0.584-02.341)

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 1.340 NNW 1.888 1.173 (0.571-2.726) (1.050-2.726) (0.609-1.738)

K-40 NA 6 26 >10 miles 2 2 3.981 4.449 4.449 (3.109-4.587) (3.147-5.751) (3.147-5.751)

Other Note 7 <LLD NA NA <LLD <LLD Gammas 3-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2019 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 11 32 < 0.1 Mi 11 4 (pCi/l) 1102 1102 <LLD (402-4780) (402-4780)

GAMMA 16 11 32 < 0.1 Mi 11 3 K-40 NA 322 322 256 (229-408) (229-408) (183-300)

Other Note 5 <LLD NA NA <LLD <LLD Gammas Bottom Sedim ent GAMMA 10 (pCi/g dry) K-40 NA 8 31 1.8 Mi. 2 2 14.65 NW 15.95 14.21 (12.03-19.49) (14.35-17.54) (13.74-14.68)

Ac-228 8 37C 3.5 Mi. 1 1

<LLD WSW 1.112 1.112

(<LLD-1.112) (<LLD-1.112)

Other Note 3 <LLD NA NA <LLD <LLD Gammas Flora GAMMA 16 (pCi/g wet) BE-7 NA 3 36 2.7 Mi. 2 2 0.3208 WSW 0.3635 0.3635 (0.3133-0.3347) (0.2867-0.4402) (0.2867-0.4402)

K-40 NA 12 32 < 0.1 Mi 4 4 6.5823 7.65 6.1343 (4.8820-9.3060) (6.2440-9.3060) (5.1410-6.7950)

I-131 0.06 12 NA NA <LLD 4

<LLD <LLD Other Note 6 <LLD NA NA <LLD <LLD Gammas 3-4

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2019 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 32 < 0.1 Mi 2 NA 3.342 3.831 (2.647-4.737) (2.924-4.737)

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 2.432 NW 2.432 2.21 (2.288-2.575) (2.288-2.575) (1.834-2.585)

Other Note 9 <LLD NA NA <LLD <LLD Gammas Clam s GAMMA 4 (pCi/g wet) K-40 NA 3/4 29 < 0.5 Mi. 2 NA 1.61 ENE to ESE 1.629 (1.539-1.718) (1.539-1.718)

Other Note 9 <LLD NA NA <LLD NA Gammas Lobster GAMMA 4 (pCi/g wet) K-40 NA 2 89 >4.0 miles 2 2 2.657 of discharge 2.782 2.782 (2.435-2.879) (2.446-3.117) (2.446-3.117)

Other Note 9 <LLD NA NA <LLD <LLD Gammas 3-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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):

4.66 S b LLD =

E

• V

• 2.22

• Y

• exp (-O't)

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)

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

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

3-6

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 2V error (i.e., the measured value exceeds 3V). The reported error is two times the standard deviation (2V) 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 3-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 1 QUARTERLY GAMMA EXPOSURE RATE (uR/hr)*

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

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

1Q 7.6 0.7 11.1 0.7 7.3 0.5 7.6 0.5 8.8 0.8 8.9 0.8 5.3 0.5 11.1 0.7 11.1 0.9 8.6 0.6 7.2 0.4 2Q 8.0 0.3 11.3 0.4 7.5 0.4 8.3 0.4 9.5 0.8 8.4 0.4 4.9 0.3 10.9 0.5 11.2 0.5 9.5 1.3 7.3 0.7 3Q 7.9 0.5 11.2 0.9 7.5 0.7 7.9 0.4 9.5 1.3 8.9 1.2 4.5 0.6 11.2 0.7 11.3 0.7 9.5 0.9 6.9 0.4 4Q 7.7 0.5 10.5 0.7 7.2 0.5 7.7 0.5 9.2 0.7 8.6 1.2 4.6 0.3 10.7 0.9 11.2 0.8 9.2 0.8 6.8 0.6 PERIOD 13C 14C 15C 16C 27 41 42 43 44 45 46

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

1Q 8.4 0.7 9.1 0.6 7.3 0.6 5.7 0.5 7.6 0.6 6.5 0.5 7.1 0.7 7.8 0.5 7.8 0.5 6.8 0.4 7.9 0.7 2Q 9.1 0.5 9.5 0.4 7.9 0.4 5.9 0.5 7.4 0.5 6.9 0.3 7.3 0.7 7.2 0.3 8.1 0.6 7.3 0.4 8.3 0.4 3Q 8.8 0.8 9.5 0.8 8.0 0.6 6.2 0.5 7.2 0.5 7.2 0.8 7.5 0.5 7.1 0.6 8.0 0.8 7.2 0.7 8.2 0.6 4Q 8.7 0.7 9.4 0.6 7.7 0.5 6.0 0.4 7.5 0.6 7.0 0.8 7.2 0.6 7.4 0.6 7.9 0.7 6.8 0.5 8.4 0.7 PERIOD 47 48 49 50 51 52 53 55 56 57 59

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

1Q 7.5 0.5 9.0 0.6 7.5 0.9 7.8 0.5 6.5 0.6 6.9 0.5 7.1 0.4 7.2 0.5 7.1 0.5 6.8 0.6 7.4 0.8 2Q 7.8 0.5 9.3 0.7 7.9 0.4 7.9 0.5 6.5 0.8 6.9 0.4 7.4 0.4 7.2 0.3 7.3 0.9 6.9 0.4 8.0 0.5 3Q 7.6 0.5 8.9 0.5 7.6 0.8 7.7 0.6 6.5 0.5 7.1 0.5 6.9 0.7 7.2 0.7 6.8 0.5 6.6 0.5 7.8 0.6 4Q 7.4 0.5 8.9 0.7 7.6 0.6 7.6 0.8 6.1 0.4 7.1 0.5 6.9 0.7 7.2 0.5 7.0 0.5 6.7 0.4 7.8 0.5 PERIOD 60 61 62 63 64 65 66 73 74 75

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

1Q 6.0 0.6 6.2 0.4 8.2 0.6 8.3 0.5 7.1 0.5 7.9 0.6 7.2 0.5 7.3 0.6 7.5 0.5 6.7 0.4 2Q 6.7 0.3 6.5 0.3 8.0 0.5 8.4 0.9 7.0 0.6 7.9 0.4 7.5 0.7 7.1 0.4 7.6 0.4 6.8 1.0 3Q 6.3 0.5 6.3 0.7 7.8 0.9 8.3 0.5 7.2 0.5 7.6 0.5 7.1 0.5 6.6 0.4 7.3 0.9 6.6 0.5 4Q 6.2 0.4 6.5 0.4 8.2 0.5 8.4 0.5 7.3 0.8 7.9 0.9 6.9 0.4 6.8 0.5 7.2 0.7 6.7 0.5

• 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 3-8

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 2 AIR PARTICULATES GROSS BETA RADIOACTIVITY (pCi/m3 )

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

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

01/08/19 0.012 0.002 0.010 0.002 0.011 0.002 0.012 0.002 0.012 0.002 0.009 0.002 0.011 0.002 0.013 0.002 01/22/19 0.012 0.002 0.011 0.002 0.012 0.002 0.013 0.002 0.010 0.002 0.010 0.002 0.012 0.002 0.013 0.002 02/05/19 0.015 0.002 0.014 0.002 0.015 0.002 0.016 0.002 0.017 0.002 0.016 0.002 0.016 0.002 0.016 0.002 02/19/19 0.012 0.002 0.010 0.002 0.011 0.002 0.009 0.002 0.011 0.002 0.010 0.002 0.011 0.002 0.011 0.002 03/05/19 0.015 0.002 0.014 0.002 0.014 0.002 0.014 0.002 0.016 0.002 0.014 0.002 0.016 0.002 0.015 0.002 03/19/19 0.013 0.002 0.012 0.002 0.012 0.002 0.015 0.002 0.016 0.002 0.017 0.002 0.016 0.002 0.015 0.002 04/02/19 0.013 0.002 0.014 0.002 0.012 0.002 0.015 0.002 0.016 0.002 0.014 0.002 0.014 0.002 0.014 0.002 04/16/19 0.008 0.002 0.007 0.002 0.007 0.002 0.008 0.002 0.009 0.002 0.007 0.002 0.007 0.002 0.007 0.002 04/30/19 0.010 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 0.009 0.002 05/14/19 0.008 0.002 0.010 0.002 0.008 0.002 0.008 0.002 0.010 0.002 0.009 0.002 0.008 0.002 0.008 0.002 05/28/19 0.008 0.002 0.010 0.002 0.009 0.002 0.009 0.002 0.008 0.002 0.008 0.002 0.009 0.002 0.008 0.002 06/11/19 0.009 0.002 0.008 0.002 0.007 0.002 0.009 0.002 0.009 0.002 0.008 0.002 0.008 0.002 0.008 0.002 06/25/19 0.007 0.002 0.007 0.002 0.008 0.002 0.009 0.002 0.009 0.002 0.008 0.001 0.008 0.002 0.009 0.002 07/09/19 0.012 0.002 0.012 0.002 0.011 0.002 0.012 0.002 0.011 0.002 0.014 0.002 0.011 0.002 0.012 0.002 07/23/19 0.009 0.002 0.010 0.002 0.011 0.002 0.011 0.002 0.012 0.002 0.011 0.002 0.010 0.001 0.011 0.002 08/06/19 0.016 0.002 0.013 0.002 0.014 0.002 0.014 0.002 0.014 0.002 0.016 0.002 0.017 0.002 0.017 0.002 08/19/19 0.014 0.002 0.012 0.002 0.015 0.002 0.014 0.002 0.015 0.002 0.014 0.002 0.014 0.002 0.016 0.002 09/03/19 0.012 0.002 0.011 0.002 0.011 0.002 0.011 0.002 0.013 0.002 0.011 0.002 0.012 0.002 0.014 0.002 09/17/19 0.012 0.002 0.013 0.002 0.014 0.002 0.012 0.002 0.013 0.002 0.013 0.002 0.014 0.002 0.012 0.002 10/01/19 0.014 0.002 0.012 0.002 0.012 0.002 0.012 0.002 0.011 0.002 0.013 0.002 0.013 0.002 0.012 0.002 10/15/19 0.012 0.002 0.012 0.002 0.010 0.002 0.011 0.002 0.011 0.002 0.011 0.002 0.012 0.002 0.011 0.002 10/29/19 0.010 0.002 0.010 0.002 0.009 0.002 0.008 0.002 0.009 0.002 0.011 0.002 0.010 0.002 0.009 0.002 11/14/19 0.012 0.002 0.012 0.002 0.011 0.002 0.013 0.002 0.012 0.002 0.012 0.002 0.012 0.002 0.012 0.002 11/26/19 0.012 0.002 0.014 0.002 0.012 0.002 0.014 0.002 0.013 0.002 0.013 0.002 0.012 0.002 0.013 0.002 12/10/19 0.010 0.002 0.011 0.002 0.011 0.002 0.010 0.002 0.009 0.002 0.011 0.002 0.011 0.002 0.009 0.002 12/23/19 0.014 0.002 0.016 0.002 0.014 0.002 0.015 0.002 0.014 0.002 0.014 0.002 0.016 0.002 0.014 0.002 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 3-9 C= Control location, Background location

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 3 AIRBORNE IODINE (pCi/m3 )

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

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

01/08/19 -0.002 0.015 -0.002 0.014 -0.002 0.014 -0.002 0.014 -0.003 0.022 -0.003 0.023 -0.003 0.021 -0.003 0.025 01/22/19 0.005 0.017 0.004 0.015 0.004 0.015 0.004 0.016 0.031 0.025 0.032 0.025 0.013 0.010 0.034 0.027 02/05/19 -0.004 0.014 -0.006 0.023 -0.006 0.023 -0.007 0.025 -0.006 0.024 -0.005 0.020 -0.005 0.019 -0.006 0.022 02/19/19 -0.008 0.016 -0.008 0.016 -0.007 0.015 -0.008 0.016 0.003 0.016 0.003 0.016 0.003 0.015 0.004 0.018 03/05/19 -0.002 0.013 -0.002 0.013 -0.002 0.013 -0.002 0.013 -0.010 0.022 -0.010 0.024 -0.009 0.022 -0.011 0.025 03/19/19 -0.003 0.015 -0.003 0.014 -0.003 0.014 -0.004 0.015 -0.017 0.014 -0.018 0.015 -0.013 0.012 -0.019 0.016 04/02/19 0.009 0.025 0.009 0.024 0.008 0.023 0.009 0.025 -0.006 0.018 -0.006 0.020 -0.003 0.010 -0.006 0.021 04/16/19 -0.004 0.017 -0.003 0.016 -0.003 0.015 -0.004 0.017 0.005 0.019 0.005 0.020 0.002 0.010 0.005 0.019 04/30/19 -0.003 0.008 -0.003 0.007 -0.003 0.007 -0.003 0.007 -0.001 0.012 -0.001 0.013 -0.001 0.012 -0.001 0.011 05/14/19 -0.006 0.010 -0.008 0.011 -0.007 0.011 -0.007 0.010 0.004 0.016 0.005 0.017 0.004 0.015 0.004 0.014 05/28/19 -0.002 0.008 -0.003 0.010 -0.002 0.009 -0.002 0.008 -0.013 0.017 -0.015 0.019 -0.013 0.017 -0.012 0.016 06/11/19 -0.001 0.006 -0.001 0.007 -0.001 0.007 -0.001 0.006 0.001 0.022 0.001 0.018 0.001 0.022 0.001 0.021 06/25/19 -0.001 0.016 -0.002 0.017 -0.002 0.018 -0.001 0.015 0.012 0.018 0.010 0.014 0.012 0.018 0.011 0.017 07/09/19 0.002 0.012 0.002 0.015 0.002 0.013 0.002 0.013 -0.002 0.010 -0.002 0.007 -0.002 0.010 -0.002 0.009 07/23/19 0.001 0.009 0.001 0.008 0.001 0.010 0.001 0.010 0.008 0.016 0.007 0.013 0.006 0.012 0.008 0.015 08/06/19 -0.012 0.023 -0.011 0.021 -0.013 0.024 -0.013 0.024 0.004 0.016 0.003 0.013 0.003 0.014 0.004 0.015 08/19/19 -0.006 0.019 -0.005 0.018 -0.006 0.020 -0.006 0.020 -0.012 0.018 -0.006 0.008 -0.011 0.016 -0.011 0.016 09/03/19 -0.003 0.010 -0.003 0.009 -0.003 0.010 -0.003 0.010 0.008 0.008 0.006 0.006 0.007 0.007 0.007 0.007 09/17/19 0.006 0.017 0.006 0.015 0.006 0.017 0.006 0.017 -0.005 0.013 -0.004 0.010 -0.004 0.010 -0.005 0.011 10/01/19 -0.008 0.020 -0.006 0.015 -0.007 0.016 -0.006 0.016 -0.007 0.016 0.012 0.016 0.010 0.013 0.012 0.015 10/15/19 -0.015 0.014 -0.014 0.013 -0.014 0.014 -0.013 0.013 0.004 0.018 0.004 0.019 0.004 0.018 0.004 0.017 10/29/19 0.004 0.008 0.004 0.008 0.004 0.008 0.004 0.008 -0.003 0.011 -0.004 0.012 -0.003 0.011 -0.001 0.004 11/14/19 0.009 0.015 0.010 0.016 0.006 0.009 0.010 0.015 -0.017 0.016 -0.015 0.013 -0.016 0.015 -0.015 0.014 11/26/19 0.013 0.009 0.017 0.012 0.016 0.011 0.016 0.011 0.017 0.012 -0.001 0.010 -0.001 0.011 -0.001 0.010 12/10/19 0.000 0.012 0.000 0.013 0.000 0.011 0.000 0.012 0.000 0.008 0.000 0.008 0.000 0.008 0.000 0.008 12/23/19 -0.004 0.019 -0.004 0.020 -0.003 0.017 -0.004 0.019 0.004 0.013 0.004 0.012 0.005 0.013 0.004 0.012 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 C= Control location, Background location 3-10

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 4 AIR PARTICULATES (pCi/m3 )

GAMMA SPECTRA - QTR 1 (12/26/18 - 04/02/19)

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

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

1 0.0086 0.0157 -0.0012 0.0016 0.1363 0.0386 -0.0004 0.0012 0.0001 0.0025 -0.0006 0.0013 0.0012 0.0029 2 -0.0117 0.0092 -0.0007 0.0020 0.1413 0.0299 -0.0001 0.0010 0.0006 0.0017 0.0002 0.0011 0.0022 0.0023 3 -0.0050 0.0101 0.0002 0.0018 0.1657 0.0320 0.0000 0.0009 -0.0005 0.0018 -0.0004 0.0010 -0.0011 0.0026 4 0.0012 0.0120 0.0002 0.0015 0.1355 0.0521 -0.0005 0.0017 0.0002 0.0031 -0.0002 0.0016 -0.0014 0.0042 10 -0.0031 0.0105 -0.0007 0.0012 0.1207 0.0305 0.0002 0.0012 -0.0004 0.0014 0.0002 0.0009 0.0003 0.0025 11 0.0089 0.0144 -0.0001 0.0016 0.1125 0.0279 -0.0006 0.0010 0.0006 0.0020 -0.0004 0.0011 0.0015 0.0026 27 -0.0067 0.0122 -0.0016 0.0021 0.1472 0.0293 -0.0018 0.0013 0.0023 0.0021 -0.0002 0.0012 0.0017 0.0030 15C -0.0016 0.0125 -0.0016 0.0019 0.1048 0.0294 -0.0010 0.0015 -0.0018 0.0021 -0.0004 0.0012 0.0014 0.0034 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

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

1 0.0017 0.0028 -0.0022 0.0049 0.0007 0.0040 -0.0046 0.0125 -0.0003 0.0016 0.0001 0.0012 -0.0144 0.1775 2 0.0010 0.0017 -0.0030 0.0033 0.0025 0.0032 -0.0043 0.0097 0.0000 0.0010 -0.0007 0.0010 -0.0566 0.1119 3 0.0003 0.0015 0.0009 0.0026 -0.0004 0.0025 -0.0018 0.0095 -0.0003 0.0010 0.0006 0.0008 0.0120 0.1420 4 0.0013 0.0027 0.0008 0.0048 -0.0009 0.0039 -0.0034 0.0123 -0.0002 0.0016 0.0000 0.0013 -0.1336 0.2135 10 0.0008 0.0017 0.0006 0.0030 -0.0024 0.0025 -0.0029 0.0094 -0.0008 0.0013 0.0008 0.0010 0.0612 0.1152 11 0.0012 0.0022 0.0000 0.0041 -0.0017 0.0031 -0.0001 0.0101 -0.0008 0.0012 -0.0001 0.0009 0.0464 0.1256 27 -0.0004 0.0021 -0.0010 0.0037 0.0004 0.0057 0.0159 0.0138 -0.0005 0.0013 0.0004 0.0011 -0.0177 0.1889 15C -0.0002 0.0023 0.0039 0.0043 -0.0003 0.0035 0.0038 0.0123 0.0004 0.0013 0.0000 0.0011 -0.0191 0.1407 LOCATION Ce-141 Ce-144

(+/-) (+/-)

1 -0.0007 0.0051 0.0009 0.0056 2 0.0006 0.0038 0.0035 0.0050 3 -0.0025 0.0036 -0.0002 0.0043 4 0.0018 0.0057 -0.0036 0.0061 10 0.0043 0.0040 0.0008 0.0042 11 -0.0033 0.0039 -0.0023 0.0044 27 -0.0064 0.0063 0.0050 0.0070 15C -0.0062 0.0049 0.0000 0.0060 C= Control location, Background location Results in bold type are positive.

3-11

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 4 AIR PARTICULATES (pCi/m3 )

GAMMA SPECTRA - QTR 2 (04/02/19 - 06/25/19)

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

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

1 0.0065 0.0119 -0.0004 0.0024 0.0932 0.0309 -0.0001 0.0011 -0.0005 0.0016 0.0007 0.0013 0.0001 0.0029 2 -0.0005 0.0114 -0.0008 0.0031 0.1002 0.0305 -0.0011 0.0016 -0.0016 0.0024 0.0004 0.0018 0.0006 0.0032 3 -0.0044 0.0121 0.0008 0.0031 0.1270 0.0291 -0.0020 0.0015 -0.0013 0.0027 0.0003 0.0011 0.0043 0.0042 4 -0.0078 0.0087 -0.0002 0.0022 0.1057 0.0262 -0.0010 0.0010 -0.0002 0.0017 -0.0008 0.0011 -0.0007 0.0030 10 -0.0038 0.0090 0.0006 0.0028 0.1434 0.0355 0.0000 0.0016 0.0003 0.0027 -0.0006 0.0016 -0.0008 0.0042 11 -0.0045 0.0151 0.0005 0.0037 0.1406 0.0333 0.0000 0.0013 -0.0014 0.0018 -0.0013 0.0014 0.0031 0.0027 27 0.0061 0.0174 0.0016 0.0040 0.0994 0.0275 0.0009 0.0014 -0.0005 0.0023 0.0007 0.0016 0.0008 0.0035 15C -0.0021 0.0126 -0.0016 0.0017 0.1004 0.0256 -0.0003 0.0011 0.0000 0.0014 0.0000 0.0010 0.0023 0.0032 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

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

1 0.0033 0.0023 -0.0014 0.0034 -0.0002 0.0029 -0.0013 0.0094 -0.0004 0.0012 0.0010 0.0010 -0.0213 0.0998 2 0.0013 0.0025 0.0003 0.0047 -0.0020 0.0035 0.0002 0.0137 -0.0003 0.0017 0.0008 0.0013 0.0407 0.1132 3 -0.0011 0.0028 0.0002 0.0047 0.0014 0.0036 0.0003 0.0129 -0.0004 0.0020 0.0008 0.0014 0.0463 0.1209 4 0.0000 0.0017 0.0004 0.0032 -0.0006 0.0028 0.0004 0.0109 -0.0008 0.0013 0.0001 0.0009 -0.0715 0.1062 10 -0.0008 0.0029 -0.0007 0.0057 0.0016 0.0039 -0.0025 0.0129 -0.0001 0.0018 -0.0008 0.0017 0.0449 0.1596 11 0.0003 0.0022 -0.0012 0.0033 0.0003 0.0029 -0.0044 0.0088 0.0001 0.0014 0.0002 0.0010 -0.0479 0.1125 27 -0.0017 0.0022 0.0009 0.0044 -0.0013 0.0033 0.0011 0.0118 -0.0002 0.0015 0.0018 0.0014 0.0751 0.1339 15C 0.0010 0.0019 0.0000 0.0032 0.0007 0.0023 -0.0027 0.0098 0.0008 0.0009 0.0001 0.0009 -0.0155 0.0890 LOCATION Ce-141 Ce-144

(+/-) (+/-)

1 -0.0007 0.0047 -0.0021 0.0058 2 -0.0067 0.0054 -0.0022 0.0065 3 -0.0033 0.0053 0.0040 0.0070 4 0.0028 0.0035 0.0009 0.0051 10 0.0011 0.0056 -0.0005 0.0072 11 0.0022 0.0031 0.0022 0.0043 27 0.0011 0.0048 0.0022 0.0067 15C -0.0019 0.0040 -0.0006 0.0055 C= Control location, Background location Results in bold type are positive.

3-12

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 4 AIR PARTICULATES (pCi/m3 )

GAMMA SPECTRA - QTR 3 (06/25/19 - 10/01/19)

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

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

1 -0.0037 0.0087 0.0002 0.0022 0.0786 0.0249 0.0005 0.0007 -0.0002 0.0014 0.0000 0.0009 0.0006 0.0024 2 -0.0024 0.0080 0.0010 0.0018 0.1133 0.0270 0.0017 0.0011 -0.0009 0.0014 0.0010 0.0010 0.0001 0.0029 3 0.0104 0.0146 -0.0007 0.0023 0.1345 0.0267 0.0000 0.0009 -0.0003 0.0016 -0.0010 0.0009 0.0010 0.0030 4 0.0036 0.0093 0.0005 0.0020 0.1091 0.0272 0.0007 0.0011 -0.0008 0.0017 0.0005 0.0010 -0.0015 0.0031 10 -0.0069 0.0103 -0.0023 0.0022 0.1136 0.0306 0.0002 0.0008 0.0006 0.0019 0.0007 0.0013 0.0009 0.0026 11 0.0097 0.0118 0.0004 0.0020 0.1214 0.0243 0.0003 0.0009 0.0010 0.0013 -0.0002 0.0008 0.0010 0.0018 27 0.0023 0.0113 0.0005 0.0018 0.1094 0.0264 0.0000 0.0013 0.0001 0.0017 0.0000 0.0010 0.0019 0.0025 15C 0.0033 0.0106 0.0008 0.0024 0.1269 0.0260 0.0000 0.0008 -0.0003 0.0015 0.0006 0.0010 0.0016 0.0025 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

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

1 0.0019 0.0017 -0.0013 0.0029 -0.0020 0.0023 -0.0035 0.0085 0.0010 0.0010 0.0000 0.0008 0.0024 0.0838 2 0.0020 0.0018 -0.0005 0.0031 0.0000 0.0019 -0.0084 0.0078 0.0001 0.0009 -0.0001 0.0009 -0.0416 0.0735 3 0.0003 0.0017 -0.0019 0.0025 -0.0022 0.0023 -0.0097 0.0085 0.0012 0.0010 0.0013 0.0010 0.0348 0.0758 4 -0.0008 0.0020 0.0012 0.0028 -0.0010 0.0027 -0.0043 0.0113 0.0005 0.0011 0.0001 0.0011 0.0145 0.0907 10 0.0000 0.0017 0.0010 0.0034 0.0002 0.0021 0.0051 0.0078 -0.0012 0.0011 0.0001 0.0008 -0.0407 0.0736 11 0.0012 0.0013 0.0010 0.0023 -0.0010 0.0019 0.0048 0.0072 0.0008 0.0009 0.0004 0.0007 -0.0137 0.0654 27 0.0005 0.0014 0.0009 0.0030 0.0006 0.0025 -0.0012 0.0105 -0.0001 0.0012 0.0002 0.0010 0.0592 0.0904 15C 0.0005 0.0013 -0.0006 0.0022 -0.0018 0.0021 -0.0012 0.0079 0.0003 0.0010 0.0000 0.0008 0.0740 0.0821 LOCATION Ce-141 Ce-144

(+/-) (+/-)

1 0.0037 0.0033 0.0007 0.0042 2 0.0003 0.0026 0.0005 0.0039 3 -0.0004 0.0035 0.0023 0.0043 4 0.0015 0.0037 0.0023 0.0055 10 -0.0002 0.0031 0.0013 0.0038 11 -0.0009 0.0025 -0.0005 0.0034 27 -0.0022 0.0035 -0.0022 0.0042 15C 0.0016 0.0029 0.0011 0.0035 C= Control location, Background location Results in bold type are positive.

3-13

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 4 AIR PARTICULATES (pCi/m3 )

GAMMA SPECTRA - QTR 4 (10/01/19 - 01/07/20)

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

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

1 -0.0113 0.0104 -0.0005 0.0025 0.0914 0.0276 -0.0002 0.0012 0.0016 0.0018 -0.0005 0.0013 0.0024 0.0028 2 0.0013 0.0100 -0.0005 0.0019 0.0966 0.0248 0.0000 0.0012 -0.0010 0.0016 0.0005 0.0013 0.0005 0.0026 3 0.0076 0.0085 -0.0001 0.0017 0.0744 0.0171 -0.0001 0.0008 -0.0006 0.0009 -0.0004 0.0007 0.0005 0.0022 4 0.0078 0.0102 -0.0001 0.0021 0.0731 0.0190 -0.0002 0.0008 0.0005 0.0013 -0.0002 0.0009 0.0020 0.0021 10 -0.0006 0.0086 0.0012 0.0028 0.0885 0.0219 -0.0007 0.0007 -0.0006 0.0014 0.0003 0.0004 0.0001 0.0019 11 0.0079 0.0108 -0.0004 0.0026 0.0946 0.0199 0.0003 0.0009 -0.0007 0.0011 -0.0006 0.0008 -0.0006 0.0021 27 0.0106 0.0121 0.0029 0.0039 0.0800 0.0359 -0.0005 0.0014 -0.0004 0.0022 -0.0004 0.0013 0.0007 0.0031 15C -0.0031 0.0078 0.0007 0.0019 0.0819 0.0240 -0.0002 0.0010 -0.0004 0.0016 0.0001 0.0010 0.0002 0.0021 LOCATION Nb-95 Zr-95 Ru-103 Ru-106 Cs-134 Cs-137 Ba-140

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

1 0.0000 0.0020 -0.0014 0.0032 -0.0014 0.0022 0.0088 0.0099 0.0010 0.0011 0.0002 0.0011 -0.0462 0.0982 2 0.0005 0.0019 -0.0017 0.0033 -0.0016 0.0028 0.0010 0.0080 -0.0007 0.0011 0.0002 0.0009 0.0675 0.0905 3 -0.0002 0.0012 0.0006 0.0022 0.0009 0.0017 -0.0016 0.0063 -0.0005 0.0008 -0.0001 0.0006 -0.0044 0.0679 4 0.0018 0.0015 -0.0011 0.0022 -0.0001 0.0019 -0.0031 0.0088 -0.0004 0.0008 -0.0002 0.0007 -0.0252 0.0665 10 -0.0002 0.0014 0.0020 0.0022 -0.0002 0.0017 0.0079 0.0074 -0.0001 0.0011 -0.0001 0.0008 0.0531 0.0720 11 0.0003 0.0012 -0.0005 0.0020 0.0006 0.0018 -0.0041 0.0055 0.0005 0.0008 0.0004 0.0008 0.0235 0.0716 27 -0.0019 0.0024 0.0009 0.0038 0.0018 0.0032 0.0115 0.0139 0.0011 0.0015 0.0003 0.0013 0.0846 0.1227 15C -0.0004 0.0017 -0.0001 0.0030 0.0014 0.0024 0.0020 0.0104 -0.0004 0.0011 0.0003 0.0009 0.0060 0.0933 LOCATION Ce-141 Ce-144

(+/-) (+/-)

1 -0.0011 0.0034 -0.0024 0.0042 2 0.0000 0.0041 0.0027 0.0052 3 0.0005 0.0027 0.0010 0.0035 4 0.0025 0.0025 -0.0017 0.0035 10 -0.0008 0.0025 0.0043 0.0036 11 0.0005 0.0026 -0.0001 0.0032 27 0.0017 0.0047 -0.0037 0.0064 15C 0.0008 0.0037 -0.0023 0.0047 C= Control location, Background location Results in bold type are positive.

3-14

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 5 SOIL (pCi/g dry wt.)

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

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

3 05/07/19 0.031 0.356 13.200 1.731 0.022 0.363 0.003 0.043 -0.027 0.040 -0.050 0.089 4 05/07/19 0.604 0.548 13.390 1.701 0.099 0.446 0.002 0.050 0.010 0.045 0.019 0.107 14C 05/07/19 0.608 0.580 14.900 1.328 -0.129 0.316 0.020 0.039 0.004 0.036 -0.058 0.077 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

3 05/07/19 0.004 0.045 0.056 0.110 0.010 0.040 -0.001 0.067 -0.007 0.040 0.102 0.394 4 05/07/19 0.023 0.047 0.072 0.113 0.040 0.056 -0.044 0.081 0.020 0.046 0.350 0.458 14C 05/07/19 0.010 0.042 0.017 0.100 0.020 0.040 -0.008 0.064 -0.004 0.036 0.175 0.303 COLLECTION LOCATION DATE Sb-125 Cs-134 Cs-137 Ce-141 Ce-144 Ac-228

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

3 05/07/19 0.009 0.117 0.018 0.050 0.189 0.075 -0.014 0.061 -0.033 0.257 0.213 0.357 4 05/07/19 -0.053 0.139 0.076 0.056 0.312 0.101 -0.026 0.074 0.066 0.311 0.091 0.412 14C 05/07/19 -0.015 0.106 0.030 0.044 0.154 0.069 0.037 0.058 0.088 0.240 1.073 0.281 C= Control location, Background location Results in bold type are postive.

3-15

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 6 MILK (pCi/l)

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 2019.

Strontium analysis of air samples and gamma analysis of Broadleaf vegetation were performed as a substitite (Table 4 & Table 9) 23 Goat 3-16

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 7 WELL WATER (pCi/l)

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

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

71 03/13/19 -18 497 -39.8 33.9 -17.5 47.4 -35.2 40.6 0.80 3.52 -3.39 3.62 -6.10 7.31 2.67 3.02 05/22/19 -6 469 -6.06 41.2 -12.7 61.6 3.07 41.3 -4.16 5.21 -1.32 4.85 -4.99 10.3 3.65 5.14 08/21/19 227 551 -12.4 35.5 -24.5 52.9 -30.5 40.0 -3.01 4.08 0.02 3.84 -0.40 7.58 2.77 3.94 11/06/19 102 574 3.24 39.9 73.4 81.9 -11.9 44.9 1.83 5.60 -1.77 4.96 -7.47 9.50 0.49 3.88 72 03/13/19 -53 493 25.4 40.5 -66.5 74.8 -26.4 46.0 0.91 4.97 -1.30 4.92 0.78 8.53 -0.12 4.51 05/22/19 -108 467 -17.1 37.4 -12.9 64.5 -38.8 40.7 2.65 4.49 1.19 4.92 3.98 9.97 3.86 5.08 08/20/19 316 555 -28.0 35.8 32.9 65.6 -33.6 40.4 1.41 4.11 1.71 4.03 -8.71 8.69 -0.65 3.67 11/06/19 368 601 -1.73 40.8 0.17 84.8 8.49 41.8 -1.00 4.32 -2.04 4.49 2.15 10.1 1.40 4.34 76 02/04/19 -53 469 -24.6 31.3 -14.2 49.8 -4.03 34.8 -3.23 3.87 0.94 3.29 -9.57 7.59 0.18 4.35 05/20/19 183 495 -16.1 34.9 -12.1 52.6 22.0 34.7 2.14 3.93 -1.36 3.89 -4.03 9.39 -0.54 3.96 08/19/19 -90 551 24.3 18.3 -11.1 30.7 -0.69 19.5 -0.11 2.03 -0.43 1.88 3.98 4.51 2.23 2.18 11/04/19 422 574 10.4 34.7 73.0 61.6 -17.7 32.2 -1.46 3.68 0.71 3.52 1.38 6.46 -0.32 3.47 77 02/05/19 192 471 -10.6 35.4 -13.3 55.8 -16.5 41.3 -0.43 4.25 -4.94 4.50 6.19 8.28 2.07 3.98 05/20/19 -29 482 -1.25 45.2 41.4 93.2 46.1 51.7 -2.93 5.85 -3.01 5.78 -5.34 9.96 0.81 5.23 08/19/19 77 563 17.5 22.7 37.0 49.0 -4.43 26.3 -0.17 2.52 0.28 2.71 -1.78 5.06 3.01 2.39 11/04/19 201 556 39.0 47.2 -2.91 70.8 -13.9 49.0 -6.78 5.80 0.67 5.41 -0.80 11.6 0.26 5.89 78 02/04/19 46 462 -7.31 30.7 -7.52 47.4 -39.9 32.1 2.78 3.78 -3.27 3.39 -1.03 6.79 0.43 4.12 05/20/19 -12 488 12.9 28.0 -60.6 45.5 19.2 30.8 -1.52 3.70 -0.53 2.91 -0.40 5.94 0.33 3.26 08/19/19 227 580 -11.6 22.1 43.1 53.5 5.50 24.9 0.11 2.27 -0.77 2.32 2.31 5.02 -0.36 2.53 11/04/19 261 552 -52.0 37.2 9.92 54.3 -39.4 36.4 -1.63 4.43 -3.08 4.70 -4.88 9.23 0.48 4.61 79 02/06/19 324 460 22.0 30.0 -38.9 55.7 5.05 36.5 -0.25 3.91 -1.61 4.02 5.62 8.22 1.07 3.73 05/22/19 -17 482 -17.5 42.5 -55.1 70.1 18.2 45.0 -0.60 5.57 -3.33 4.80 -12.4 10.2 -0.24 6.70 08/21/19 275 548 -1.57 29.0 12.1 65.5 2.71 31.7 1.01 3.24 -1.24 3.72 0.27 6.25 1.35 3.40 11/06/19 360 599 19.3 44.1 41.9 85.9 -23.1 41.8 -2.72 5.44 2.13 4.35 -6.07 8.61 1.37 4.17 81 03/13/19 327 524 -37.7 38.9 25.7 58.6 -4.06 43.6 1.50 3.87 -3.19 3.89 4.74 7.06 4.28 3.86 05/22/19 502 522 -7.33 38.6 -32.9 58.1 -12.0 41.8 4.20 4.73 -1.75 5.03 7.44 8.28 2.19 4.34 07/09/19 47 511 -3.41 30.2 -9.54 51.7 -5.62 30.5 -0.66 3.34 0.62 3.30 -1.94 6.45 1.38 2.97 11/06/19 713 618 -23.6 38.9 27.4 64.8 29.7 43.4 -2.41 4.20 -3.15 3.99 -4.39 9.37 -1.76 5.05 82 02/06/19 55 430 -19.0 29.3 -27.5 50.1 -7.95 32.1 1.78 3.17 -1.18 3.29 2.02 6.04 -0.19 2.88 04/29/19 -29 468 -3.93 58.4 -26.7 79.3 -24.6 60.4 -6.64 6.99 -0.15 6.71 -8.78 12.3 0.21 6.46 07/09/19 138 523 -21.8 41.6 7.55 47.4 -3.96 50.7 -5.35 4.77 -4.39 4.30 -5.11 8.02 -1.02 4.15 11/15/19 180 213 -31.8 32.6 20.4 42.7 -8.50 33.5 -5.33 3.68 -5.86 3.75 -8.83 7.50 0.04 3.58 83 02/06/19 -69 457 18.0 35.1 -8.37 62.3 -12.7 41.4 2.16 3.94 -2.80 4.29 0.98 7.85 2.10 4.27 05/22/19 76 493 15.0 37.5 -27.4 57.9 13.6 42.8 -0.53 3.62 -0.34 4.88 -2.90 9.85 -2.97 4.85 08/20/19 123 541 -17.8 39.6 -5.52 53.5 -6.10 46.5 2.86 3.19 -3.15 4.22 3.53 8.81 0.48 3.39 11/05/19 -116 563 -8.64 37.0 -12.7 53.1 6.57 42.0 1.55 3.74 0.86 3.81 -0.99 9.27 1.53 4.05 3-17

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 7 WELL WATER (pCi/l)

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

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

71 03/13/19 8.26 6.99 5.00 3.87 0.22 6.06 -2.01 4.04 -9.19 33.6 2.77 10.8 -0.11 6.75 0.46 4.10 05/22/19 5.57 9.37 1.65 6.32 -4.79 8.39 -0.56 4.60 3.83 41.8 -8.59 14.0 2.14 5.66 1.10 4.93 08/21/19 -1.57 7.81 -0.02 4.65 2.10 6.93 -0.82 4.46 -1.23 30.8 -8.03 11.4 -1.82 6.85 -1.49 3.99 11/06/19 -3.35 13.4 1.55 6.07 -2.76 8.33 0.04 4.24 -5.71 38.8 3.82 9.53 1.60 7.11 0.03 5.16 72 03/13/19 -2.20 9.15 1.01 4.06 -4.21 8.24 -3.45 5.19 -14.1 40.9 -8.11 13.6 -2.03 7.85 -1.31 4.69 05/22/19 -5.25 9.94 -2.01 4.34 -1.83 6.82 -6.37 5.07 -37.9 45.2 3.08 12.7 0.71 5.80 -1.22 4.85 08/20/19 -3.16 8.73 2.93 4.67 0.90 6.96 2.00 4.88 17.8 35.4 1.62 11.8 -5.91 6.56 2.94 4.67 11/06/19 -0.24 9.71 4.47 5.28 -0.35 8.39 -2.75 4.92 40.2 37.8 -4.04 12.8 4.66 7.21 1.12 5.10 76 02/04/19 2.70 10.5 0.35 4.68 -4.18 6.98 -2.49 3.98 8.62 40.8 4.15 12.1 -0.12 5.45 -1.04 4.32 05/20/19 -4.53 9.38 1.42 5.12 3.90 5.78 -1.38 4.26 -13.3 36.8 3.61 11.0 -0.12 5.65 1.54 3.84 08/19/19 -12.1 5.65 -1.04 2.09 -0.13 3.70 -0.31 2.33 18.8 18.4 -0.24 5.64 0.29 4.10 -0.58 2.45 11/04/19 0.93 9.43 9.40 4.27 2.11 6.71 -2.07 3.83 -15.4 30.7 -5.37 10.5 -2.65 4.63 1.69 3.67 77 02/05/19 19.9 11.7 9.31 5.83 3.96 7.72 -0.54 5.05 -22.5 34.9 -2.21 13.1 1.21 7.75 -1.01 4.21 05/20/19 10.9 12.3 5.41 6.21 -11.0 8.27 -0.60 6.00 15.5 43.3 -4.08 16.2 7.06 8.59 -0.28 4.95 08/19/19 12.6 6.26 1.62 2.71 1.20 4.40 1.38 2.70 17.8 22.3 4.22 7.33 4.26 5.58 1.51 2.68 11/04/19 7.28 14.8 30.3 7.31 -1.39 8.18 -3.51 5.35 26.3 44.6 4.76 17.3 -7.99 6.97 1.47 5.89 78 02/04/19 -7.07 10.2 -0.66 4.15 1.04 5.24 -0.40 4.33 13.0 33.5 -0.26 11.1 0.75 5.54 3.45 4.38 05/20/19 -12.6 9.16 1.15 3.30 -1.99 5.57 2.35 3.32 -24.2 27.4 1.16 8.87 -0.10 4.97 1.89 3.42 08/19/19 -12.4 5.57 2.07 2.47 2.25 4.41 -3.52 2.68 14.3 21.0 5.84 6.61 2.81 5.61 -1.97 2.63 11/04/19 0.35 11.5 16.2 5.80 -1.49 7.04 -3.49 4.09 -13.0 36.5 2.40 12.1 3.87 5.21 -0.52 4.78 79 02/06/19 -16.5 11.6 -2.45 4.54 0.63 6.88 -4.28 4.41 -1.80 36.5 2.31 12.5 -0.75 6.29 0.47 4.49 05/22/19 -3.96 9.72 -2.57 4.64 0.88 7.91 3.64 4.84 -30.9 46.5 5.05 13.8 2.61 6.11 -2.70 5.03 08/21/19 -9.85 8.53 2.88 3.47 -1.84 6.05 -3.10 3.62 20.3 28.3 5.07 9.30 0.13 5.31 -2.35 3.86 11/06/19 -15.6 12.5 -2.16 5.57 -6.49 9.31 -3.13 5.08 12.4 42.1 0.81 13.7 -0.58 7.47 1.20 5.78 81 03/13/19 28.0 10.9 6.14 4.50 -2.51 7.31 -2.05 4.58 -4.94 41.1 4.11 12.4 -5.16 8.22 -5.34 4.56 05/22/19 7.65 9.28 1.88 5.87 -3.30 7.33 -1.75 4.66 -11.8 37.6 11.4 15.0 -1.46 5.48 -2.42 4.95 07/09/19 -1.59 7.76 1.82 3.55 -0.30 5.26 1.78 3.69 -1.75 28.3 -2.13 8.87 -2.58 5.58 0.14 3.68 11/06/19 -6.07 12.1 8.56 5.18 -0.98 6.93 -4.71 5.08 7.68 36.4 0.40 13.5 1.73 6.55 2.18 4.52 82 02/06/19 -1.94 7.07 1.47 4.03 0.74 5.31 2.41 3.52 0.97 28.2 2.02 10.2 -0.73 5.02 1.52 3.52 04/29/19 9.70 14.0 9.22 7.73 4.75 10.5 1.05 6.45 14.6 56.5 -6.98 19.5 -7.57 9.36 -0.26 5.82 07/09/19 1.24 10.2 14.0 5.46 -3.71 7.32 -3.37 4.78 -1.36 34.7 1.80 13.3 -3.78 8.31 0.07 4.31 11/15/19 0.72 9.05 20.2 4.46 4.27 6.14 0.78 3.62 -9.60 29.8 3.17 10.7 0.09 5.48 -0.91 3.63 83 02/06/19 1.18 10.6 -1.35 4.70 -5.40 7.57 2.74 4.41 3.75 38.3 -3.96 13.0 3.06 6.57 0.04 4.94 05/22/19 5.84 9.31 0.99 5.83 -4.89 8.86 1.24 4.63 2.30 42.6 -5.26 13.8 1.52 6.53 -0.14 5.84 08/20/19 7.29 8.98 3.20 5.35 3.62 8.22 -2.99 4.97 17.3 43.1 5.43 11.3 -1.96 7.65 0.14 3.68 11/05/19 -1.17 9.61 5.27 4.69 -2.51 6.91 -1.59 4.47 -20.5 36.0 -0.26 11.6 0.00 6.75 -1.93 4.25 3-18

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 7 WELL WATER (pCi/l)

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

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

71 03/13/19 -1.95 4.15 -2.10 18.8 -3.13 5.01 9.54 12.7 05/22/19 -8.73 5.65 -2.81 17.6 -2.45 5.29 -15.9 19.2 08/21/19 -1.80 3.75 13.1 18.7 1.10 5.25 -0.54 15.3 11/06/19 -0.26 4.64 5.18 20.5 1.64 8.30 -5.95 18.7 72 03/13/19 -0.32 3.97 -0.59 21.4 -1.72 6.58 0.35 16.7 05/22/19 -5.33 4.25 2.05 18.7 1.10 6.41 -3.24 17.0 08/20/19 -0.99 4.41 13.8 19.4 -0.35 6.48 -1.58 13.6 11/06/19 -4.37 5.45 4.03 22.4 -0.58 7.12 -1.93 19.0 76 02/04/19 -2.72 4.99 12.2 15.3 2.05 7.17 -4.09 15.6 05/20/19 -2.02 4.63 6.74 17.7 3.15 4.11 -6.04 13.5 08/19/19 2.68 2.08 -2.33 10.4 -1.98 4.61 -6.41 8.27 11/04/19 -0.21 4.30 -5.12 16.0 -1.83 4.05 5.24 16.8 77 02/05/19 -4.57 4.32 -3.61 20.4 0.13 6.40 6.22 16.0 05/20/19 -3.66 5.81 2.18 22.7 -2.49 8.39 -0.74 20.7 08/19/19 -0.60 2.66 4.09 14.2 7.68 4.34 6.26 9.68 11/04/19 -10.7 6.21 -6.00 22.3 -3.01 8.20 -13.3 19.2 78 02/04/19 -3.19 3.88 -5.97 15.1 3.61 5.71 -9.86 15.6 05/20/19 -2.24 3.66 -4.62 13.8 -2.32 4.89 -7.03 11.5 08/19/19 -1.71 2.34 2.55 12.5 -0.02 3.45 2.99 8.61 11/04/19 -6.48 4.87 7.97 17.4 1.55 5.76 8.57 19.3 79 02/06/19 -2.16 4.38 9.65 16.5 -1.78 7.81 16.1 16.3 05/22/19 -2.05 5.01 -4.66 18.8 -0.32 7.04 -5.00 20.6 08/21/19 0.89 3.25 2.52 14.0 3.48 4.93 -2.22 12.3 11/06/19 0.40 5.40 -3.47 20.8 1.48 7.16 1.32 20.5 81 03/13/19 -0.16 4.14 9.89 20.8 -0.87 5.38 -9.06 14.6 05/22/19 -3.44 5.26 1.57 16.3 1.36 5.18 0.53 18.7 07/09/19 0.02 2.99 -1.40 14.3 4.12 4.99 0.36 11.3 11/06/19 -1.65 5.13 -1.35 21.3 0.19 7.69 15.2 14.7 82 02/06/19 0.98 3.69 -6.88 15.1 1.22 4.48 -3.23 12.3 04/29/19 -11.4 7.19 -12.9 27.5 -0.93 8.86 10.1 22.9 07/09/19 0.05 4.71 3.39 21.7 -1.94 6.61 -6.33 15.8 11/15/19 0.51 3.99 -6.87 15.8 3.45 5.89 15.4 13.8 83 02/06/19 -2.02 4.44 10.9 19.1 -4.60 7.13 12.7 18.7 05/22/19 -2.59 5.15 -12.3 18.4 -2.23 5.17 -1.87 15.9 08/20/19 -2.63 4.93 -9.59 22.0 -2.79 6.53 8.93 16.7 11/05/19 -1.43 4.32 -25.6 19.3 -0.93 5.24 -4.06 13.7 3-19

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 8 FRUITS & VEGETABLES (pCi/g wet wt.)

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

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

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

01/14/19 Squash -0.023 0.077 5.523 0.434 -0.038 0.080 0.004 0.009 0.000 0.010 0.001 0.022 0.004 0.009 07/25/19 Lettuce 0.928 0.238 2.099 0.415 0.060 0.150 -0.001 0.015 -0.002 0.014 0.007 0.029 0.009 0.011 07/25/19 Apples -0.054 0.106 1.735 0.393 0.021 0.094 0.006 0.011 0.001 0.011 0.008 0.023 0.007 0.011 10/08/19 Tomatoes -0.083 0.132 2.100 0.362 0.158 0.149 0.009 0.014 -0.001 0.016 -0.015 0.037 -0.005 0.014 10/08/19 Apples -0.054 0.147 1.032 0.330 -0.053 0.148 0.007 0.014 0.014 0.012 -0.008 0.029 -0.004 0.014 COLLECTION DATE Type Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

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

01/14/19 Squash -0.002 0.023 -0.002 0.010 -0.003 0.017 -0.010 0.009 -0.037 0.075 -0.007 0.025 -0.002 0.013 07/25/19 Lettuce -0.020 0.032 -0.001 0.014 -0.010 0.023 0.001 0.015 -0.008 0.131 0.007 0.039 0.014 0.020 07/25/19 Apples 0.006 0.024 -0.001 0.010 -0.018 0.021 -0.003 0.012 -0.071 0.113 0.001 0.031 0.002 0.017 10/08/19 Tomatoes -0.004 0.043 0.017 0.017 0.009 0.028 -0.007 0.016 0.114 0.141 0.047 0.047 -0.005 0.025 10/08/19 Apples -0.078 0.035 -0.007 0.015 -0.008 0.028 0.005 0.017 -0.128 0.136 0.002 0.043 -0.003 0.027 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

01/14/19 Squash 0.009 0.010 -0.003 0.009 -0.035 0.051 0.006 0.010 0.013 0.015 -0.022 0.058 -0.007 0.035 07/25/19 Lettuce 0.002 0.016 0.017 0.016 -0.010 0.067 0.002 0.016 -0.001 0.025 -0.030 0.101 0.028 0.075 07/25/19 Apples -0.019 0.014 -0.006 0.012 -0.020 0.051 -0.004 0.015 -0.006 0.020 -0.045 0.080 0.062 0.052 10/08/19 Tomatoes -0.005 0.018 0.001 0.017 0.036 0.067 0.009 0.019 0.008 0.028 -0.013 0.106 0.043 0.058 10/08/19 Apples 0.001 0.016 -0.013 0.015 -0.071 0.070 0.010 0.015 -0.004 0.023 0.071 0.092 -0.002 0.063 Results in bold type are positive.

3-20

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 8 FRUITS & VEGETABLES (pCi/g wet wt.)

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

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

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

07/25/19 Lettuce 0.029 0.115 2.341 0.515 0.010 0.117 -0.001 0.012 -0.004 0.012 -0.006 0.028 -0.012 0.014 07/25/19 Plums 0.003 0.111 1.906 0.410 0.107 0.104 0.009 0.013 -0.005 0.015 -0.009 0.029 -0.009 0.014 10/08/19 Tomatoes 0.013 0.165 1.787 0.394 -0.178 0.181 0.003 0.017 -0.002 0.021 0.011 0.039 0.004 0.022 10/08/19 Apples -0.052 0.116 0.584 0.311 0.123 0.124 0.001 0.013 -0.004 0.014 -0.006 0.022 0.006 0.016 COLLECTION DATE Type Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

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

07/25/19 Lettuce 0.000 0.038 0.006 0.014 -0.023 0.026 -0.005 0.014 0.090 0.123 0.027 0.041 -0.012 0.019 07/25/19 Plums -0.002 0.028 0.002 0.013 0.001 0.022 0.005 0.012 0.043 0.115 0.010 0.036 0.000 0.016 10/08/19 Tomatoes 0.071 0.056 0.013 0.021 0.005 0.032 0.006 0.020 -0.030 0.170 -0.009 0.055 0.020 0.034 10/08/19 Apples -0.015 0.031 -0.006 0.015 0.005 0.025 -0.004 0.013 -0.023 0.115 -0.005 0.033 0.001 0.019 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

07/25/19 Lettuce -0.003 0.014 0.002 0.014 0.040 0.055 -0.002 0.017 0.006 0.019 0.103 0.070 -0.020 0.048 07/25/19 Plums 0.011 0.013 0.006 0.012 0.032 0.053 0.012 0.015 -0.003 0.018 -0.059 0.079 -0.003 0.050 10/08/19 Tomatoes -0.018 0.022 0.019 0.022 -0.004 0.084 -0.001 0.031 0.010 0.030 0.054 0.115 0.066 0.077 10/08/19 Apples -0.004 0.013 -0.004 0.015 0.005 0.061 -0.009 0.024 0.014 0.019 -0.048 0.075 0.023 0.042 C= Control location, Background location Results in bold type are positive.

3-21

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 9 BROADLEAF VEGETATION (pCi/g wet wt.)

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

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

06/24/19 1.050 0.302 4.392 0.664 -0.116 0.133 -0.013 0.015 -0.006 0.015 -0.001 0.033 0.012 0.019 10/08/19 2.726 0.196 4.023 0.317 -0.072 0.073 0.009 0.009 -0.002 0.008 0.004 0.017 0.001 0.009 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

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

06/24/19 -0.062 0.049 -0.010 0.017 0.000 0.029 0.006 0.015 -0.058 0.136 0.019 0.040 -0.011 0.021 10/08/19 -0.028 0.020 0.006 0.008 0.002 0.014 0.001 0.008 -0.016 0.081 0.007 0.022 -0.001 0.010 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/24/19 -0.016 0.021 -0.009 0.016 0.023 0.052 0.011 0.022 0.006 0.024 0.090 0.105 0.078 0.069 10/08/19 0.001 0.009 0.004 0.009 -0.002 0.032 -0.006 0.009 0.003 0.014 0.013 0.057 0.111 0.037 LOCATION 10 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

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

06/25/19 0.571 0.243 4.587 0.759 0.131 0.131 0.020 0.017 -0.002 0.015 -0.046 0.038 0.009 0.018 10/08/19 1.039 0.303 3.696 0.564 0.037 0.176 -0.012 0.022 0.004 0.022 0.020 0.045 -0.002 0.028 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

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

06/25/19 0.010 0.048 -0.003 0.018 0.011 0.027 -0.003 0.017 0.048 0.161 -0.014 0.043 0.007 0.019 10/08/19 0.047 0.057 0.013 0.024 -0.003 0.038 0.004 0.020 0.159 0.207 0.002 0.061 -0.018 0.027 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/25/19 0.002 0.017 -0.007 0.018 0.058 0.063 -0.002 0.015 0.011 0.024 0.014 0.087 -0.009 0.070 10/08/19 0.003 0.024 0.021 0.022 0.033 0.089 -0.005 0.024 -0.017 0.032 0.008 0.137 -0.010 0.095 Results in bold type are positive.

3-22

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 9 BROADLEAF VEGETATION (pCi/g wet wt.)

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

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

06/24/19 0.828 0.269 4.081 0.590 -0.027 0.130 0.009 0.016 -0.004 0.013 -0.015 0.032 0.000 0.015 10/08/19 1.829 0.331 3.109 0.606 -0.110 0.133 -0.006 0.020 0.005 0.015 -0.021 0.034 0.006 0.022 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

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

06/24/19 -0.009 0.032 -0.007 0.014 -0.003 0.027 -0.004 0.015 -0.016 0.136 -0.022 0.040 0.008 0.018 10/08/19 -0.014 0.042 0.003 0.016 0.003 0.035 0.012 0.019 0.004 0.130 0.015 0.047 0.012 0.018 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/24/19 0.002 0.014 0.009 0.019 0.019 0.060 0.000 0.012 -0.005 0.022 -0.041 0.098 0.075 0.131 10/08/19 0.009 0.018 0.012 0.021 0.061 0.080 -0.033 0.027 -0.001 0.022 0.019 0.097 0.124 0.084 LOCATION 26C COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

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

06/25/19 0.609 0.194 5.751 0.736 -0.042 0.136 -0.009 0.019 0.005 0.015 -0.019 0.038 -0.005 0.017 10/08/19 1.738 0.296 3.147 0.566 -0.137 0.130 -0.001 0.016 -0.009 0.014 0.006 0.027 0.009 0.015 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 I-131

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

06/25/19 -0.040 0.040 -0.002 0.018 0.006 0.031 0.006 0.016 -0.019 0.149 0.015 0.045 -0.011 0.018 10/08/19 -0.007 0.037 0.011 0.017 0.010 0.031 -0.003 0.016 -0.024 0.134 -0.027 0.045 -0.001 0.020 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/25/19 0.000 0.019 -0.005 0.017 -0.064 0.056 -0.005 0.016 -0.021 0.026 0.027 0.112 0.075 0.076 10/08/19 0.004 0.018 0.010 0.019 0.012 0.060 0.006 0.015 0.000 0.022 0.008 0.091 0.123 0.071 C= Control location, Background location Results in bold type are positive.

3-23

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 10 SEA WATER (pCi/l)

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

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

01/29/19 441 139 24.5 31.7 141 94 -13.4 34.0 -3.43 4.80 -0.24 3.48 -2.91 9.70 02/26/19 1120 250 -8.34 33.6 328 94 -11.7 30.8 -0.76 4.13 -2.28 3.66 3.43 8.89 03/26/19 1240 261 23.8 39.2 302 119 40.7 32.8 -0.61 3.13 -2.57 4.43 3.43 6.68 04/30/19 4780 558 -6.18 35.0 297 109 -10.7 31.2 -0.94 3.57 2.71 4.16 4.34 8.70 05/28/19 1430 276 5.70 26.6 381 80 -7.03 28.0 -2.18 3.03 -1.44 3.03 -5.07 6.08 06/25/19 493 203 -12.9 43.2 343 104 18.5 42.9 1.31 4.53 5.86 4.50 2.66 9.28 07/30/19 140 153 20.7 49.1 253 107 -4.42 51.9 -1.03 5.19 -2.44 4.95 -3.02 10.2 08/27/19 402 217 9.79 42.3 375 121 -25.4 46.1 -2.14 5.30 -0.19 4.69 1.53 9.29 09/24/19 449 205 -30.7 42.9 408 118 -36.6 43.7 0.63 5.16 2.34 4.95 10.3 8.58 10/29/19 412 131 3.59 39.0 303 108 -6.04 38.0 -1.08 4.10 -3.28 3.35 0.36 8.96 11/26/19 519 229 19.8 36.0 318 114 34.8 40.2 1.54 4.64 1.96 4.19 3.77 10.5 12/31/19 832 155 -16.9 24.8 229 78 8.17 27.2 -1.03 3.20 2.46 3.19 0.53 6.23 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

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

01/29/19 0.67 4.29 3.10 9.78 3.66 4.87 -1.89 8.03 -0.86 4.02 23.0 33.3 -1.93 12.5 02/26/19 1.27 3.92 -5.02 9.72 1.92 3.69 1.55 6.47 -2.97 4.17 -6.75 29.9 3.74 10.1 03/26/19 0.20 5.51 -6.26 8.41 3.74 4.21 3.81 6.38 -3.34 3.90 -31.4 40.3 -4.33 12.7 04/30/19 -1.57 4.10 -3.79 9.94 -1.96 3.66 -0.18 6.20 -0.79 4.15 4.22 37.3 0.04 11.6 05/28/19 -1.30 2.86 2.56 8.44 0.18 3.31 -0.73 5.35 -0.35 2.98 5.50 28.0 3.36 8.64 06/25/19 0.04 4.66 -8.09 12.2 0.90 4.46 -3.75 7.73 -1.38 4.92 29.5 44.8 -0.33 14.1 07/30/19 0.20 6.44 -13.8 10.9 4.86 5.29 -1.56 8.11 -1.89 5.08 1.95 47.5 0.45 15.8 08/27/19 -0.77 4.96 -7.97 11.0 1.72 4.85 -9.22 8.25 -5.96 4.71 21.5 44.8 1.71 12.9 09/24/19 0.00 0.00 -16.1 11.7 1.81 4.48 1.45 8.19 -2.30 5.34 -13.6 45.3 5.06 12.3 10/29/19 3.57 5.11 -10.1 12.4 -0.47 4.17 -1.08 7.14 3.61 5.02 5.10 41.9 6.56 10.7 11/26/19 2.76 4.10 -6.55 8.81 2.04 4.01 5.82 8.35 -0.89 4.81 14.2 34.9 -3.38 10.1 12/31/19 0.04 3.41 4.06 7.62 1.75 3.20 2.27 5.43 -0.28 3.65 -9.87 27.8 -1.48 8.11 Results in bold type are positive.

3-24

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 10 SEA WATER (pCi/l)

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

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

01/29/19 -3.96 4.95 2.96 5.03 5.43 4.26 3.79 14.4 -1.67 5.29 17.1 17.4 02/26/19 -4.10 4.65 3.57 4.28 -1.93 3.96 2.14 14.5 -2.48 6.82 -7.89 11.2 03/26/19 -1.60 4.48 0.62 3.34 -0.83 4.13 2.33 16.0 -3.10 6.20 -13.1 14.0 04/30/19 1.83 4.22 -2.44 4.21 3.54 4.83 -12.6 16.2 3.80 5.06 -1.72 17.0 05/28/19 0.08 3.24 0.81 3.38 -0.65 3.46 1.02 11.2 -2.36 3.30 8.12 12.7 06/25/19 -4.23 5.75 -2.60 4.97 0.66 5.21 -17.8 16.6 -2.42 5.47 7.76 19.4 07/30/19 1.49 6.43 0.94 6.43 -1.45 5.10 -1.58 17.8 -4.28 5.15 6.93 16.6 08/27/19 -2.25 6.32 -2.30 4.92 0.34 4.15 5.01 17.4 -1.65 4.26 -3.11 16.7 09/24/19 -3.68 6.06 -2.63 5.85 1.94 4.56 8.86 17.6 -2.76 4.57 -6.00 17.6 10/29/19 -0.26 4.51 1.13 4.12 1.90 4.35 -6.01 14.6 2.35 6.19 13.2 16.0 11/26/19 -3.87 6.49 -1.42 4.73 -0.92 4.53 2.42 16.8 0.96 5.20 -0.66 14.2 12/31/19 -1.99 4.91 1.13 3.43 -0.26 3.09 3.61 14.9 2.14 5.00 -6.02 12.4 LOCATION 37C COLLECTION DATE H-3 Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59

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

03/26/19 38 178 32.5 34.6 112 90 26.1 38.6 2.76 3.25 2.65 3.99 -2.89 8.19 06/25/19 132 179 -22.8 27.6 183 77 -4.75 28.4 -1.23 3.66 -2.72 4.08 10.1 6.34 09/24/19 256 194 -20.5 36.1 286 107 -5.60 33.5 0.59 4.10 2.46 4.43 -0.42 6.94 12/31/19 -2 109 -0.40 26.5 300 83 6.40 29.6 1.02 2.70 0.94 2.90 5.26 6.76 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

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

03/26/19 0.23 4.97 -0.88 11.8 -0.30 3.82 5.14 5.92 -0.75 4.19 30.3 37.6 -3.25 11.6 06/25/19 4.94 3.93 -14.3 7.98 1.90 3.39 3.35 5.73 -2.72 3.80 -21.4 30.3 -1.10 9.89 09/24/19 -2.25 4.52 -10.8 9.87 -0.07 4.57 -7.37 8.29 -3.08 4.45 -16.8 39.9 2.10 10.7 12/31/19 -2.07 3.19 -2.96 7.97 1.70 3.21 2.59 5.43 0.43 3.42 3.61 25.0 -7.23 9.87 COLLECTION DATE I-131 Cs-134 Cs-137 Ba-140 La-140 Ac-228

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

03/26/19 0.00 4.63 -1.27 3.92 1.61 3.71 -2.01 16.1 -1.20 5.11 -0.08 17.6 06/25/19 1.59 3.87 -0.51 4.00 1.25 3.81 -0.38 13.5 3.32 4.76 5.52 12.9 09/24/19 1.97 4.46 3.32 4.14 4.47 4.58 -3.67 14.4 -0.38 6.44 2.63 15.8 12/31/19 -0.88 5.27 -1.03 3.38 -0.33 3.25 9.67 13.0 -1.16 5.13 -6.49 9.58 C= Control location, Background location 3-25 Results in bold type are positive.

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

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

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

31 03/12/19 0.065 0.328 14.35 1.343 0.344 0.417 0.024 0.039 -0.001 0.034 -0.001 0.079 31 07/29/19 0.217 0.429 17.54 1.450 -0.332 0.439 0.015 0.049 0.045 0.051 0.002 0.107 32 06/07/19 0.109 0.300 13.10 1.463 -0.091 0.331 -0.006 0.040 -0.009 0.037 -0.023 0.090 32 10/08/19 0.250 0.326 13.35 1.668 -0.042 0.318 -0.030 0.044 -0.012 0.042 -0.020 0.079 33 04/10/19 -0.033 0.191 19.49 1.330 0.079 0.183 -0.013 0.026 0.013 0.024 0.014 0.055 33 12/11/19 0.080 0.226 12.22 1.377 0.080 0.227 0.008 0.027 -0.004 0.030 -0.005 0.065 34 04/10/19 0.112 0.165 15.15 1.151 -0.024 0.149 0.010 0.022 -0.012 0.021 0.066 0.050 34 12/11/19 0.123 0.296 12.03 1.306 0.071 0.294 0.012 0.030 0.011 0.035 -0.048 0.078 37C 03/12/19 -0.159 0.233 14.68 1.277 0.065 0.265 -0.024 0.026 -0.002 0.028 0.054 0.068 37C 08/08/19 0.209 0.538 13.74 1.521 0.215 0.551 0.022 0.063 -0.011 0.053 -0.141 0.099 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

31 03/12/19 -0.004 0.035 -0.122 0.093 -0.011 0.039 0.067 0.073 0.009 0.042 -0.177 0.361 31 07/29/19 0.019 0.049 0.082 0.143 0.042 0.054 0.030 0.086 -0.008 0.048 -0.186 0.450 32 06/07/19 -0.037 0.038 -0.007 0.114 -0.006 0.045 0.066 0.072 -0.026 0.038 0.029 0.328 32 10/08/19 0.002 0.042 -0.067 0.115 0.038 0.040 0.048 0.070 -0.022 0.038 -0.022 0.383 33 04/10/19 0.017 0.025 -0.045 0.085 -0.008 0.025 0.036 0.040 0.003 0.023 0.216 0.217 33 12/11/19 0.008 0.026 -0.146 0.070 -0.020 0.031 0.022 0.053 -0.015 0.027 -0.022 0.267 34 04/10/19 -0.011 0.026 -0.060 0.063 -0.001 0.021 -0.007 0.034 0.000 0.017 0.123 0.168 34 12/11/19 0.028 0.042 -0.285 0.104 0.008 0.041 0.011 0.070 -0.012 0.032 0.077 0.292 37C 03/12/19 0.008 0.030 -0.015 0.070 0.018 0.027 0.036 0.050 -0.005 0.030 0.050 0.243 37C 08/08/19 0.022 0.053 -0.115 0.126 0.016 0.064 0.034 0.109 -0.073 0.060 0.109 0.520 C= Control location, Background location Results in bold type are positive.

3-26

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

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

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

31 03/12/19 0.001 0.035 0.017 0.105 -0.039 0.079 0.178 0.070 -0.019 0.039 0.124 0.363 31 07/29/19 0.005 0.049 -0.031 0.139 -0.023 0.065 0.100 0.051 0.058 0.053 0.077 0.358 32 06/07/19 0.007 0.033 0.010 0.085 0.007 0.082 0.072 0.044 -0.001 0.037 0.111 0.338 32 10/08/19 -0.002 0.038 0.006 0.104 0.014 0.046 0.072 0.050 0.006 0.041 0.042 0.342 33 04/10/19 -0.008 0.025 0.011 0.060 -0.029 0.033 0.028 0.029 -0.004 0.030 0.012 0.202 33 12/11/19 -0.014 0.029 0.016 0.065 0.054 0.050 0.030 0.027 0.006 0.032 0.345 0.191 34 04/10/19 0.000 0.017 -0.027 0.051 -0.010 0.027 0.002 0.022 -0.007 0.018 0.028 0.085 34 12/11/19 -0.014 0.037 0.050 0.090 -0.039 0.063 -0.023 0.037 0.014 0.041 0.072 0.148 37C 03/12/19 0.004 0.025 0.023 0.073 -0.004 0.059 0.033 0.028 -0.016 0.029 0.225 0.131 37C 08/08/19 -0.003 0.060 -0.062 0.161 0.004 0.092 0.290 0.098 0.013 0.068 1.112 0.650 C= Control location, Background location 3-27

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

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

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

29 03/14/19 0.3133 0.1554 4.8870 0.3777 0.0703 0.1112 0.0035 0.0108 -0.0107 0.0120 -0.0183 0.0273 29 06/13/19 0.0511 0.0883 4.8820 0.4930 0.0099 0.0826 0.0036 0.0086 -0.0022 0.0095 0.0077 0.0171 29 08/20/19 0.3347 0.1606 6.1800 0.6861 -0.0683 0.0974 0.0044 0.0154 0.0127 0.0120 0.0155 0.0314 29 12/09/19 0.3144 0.1482 6.1320 0.4455 -0.0115 0.0698 -0.0027 0.0096 -0.0005 0.0100 0.0046 0.0216 32 03/14/19 0.1312 0.1233 6.2440 0.4878 0.0589 0.1259 -0.0019 0.0130 0.0071 0.0136 0.0030 0.0314 32 06/17/19 0.1177 0.0996 6.5190 0.5508 -0.0653 0.0941 -0.0076 0.0122 0.0019 0.0117 -0.0082 0.0266 32 08/20/19 0.2175 0.1531 9.3060 0.7936 -0.0651 0.1419 0.0073 0.0162 -0.0055 0.0162 -0.0033 0.0421 32 10/23/19 0.0582 0.1227 8.5310 0.7575 -0.0881 0.1216 0.0113 0.0167 -0.0141 0.0144 0.0062 0.0377 35 03/14/19 0.0999 0.1433 5.8840 0.5311 -0.1765 0.1482 0.0066 0.0158 0.0054 0.0161 0.0182 0.0365 35 06/11/19 0.1143 0.0925 7.3610 0.6537 -0.0343 0.0865 0.0046 0.0094 0.0086 0.0097 -0.0125 0.0209 35 08/20/19 0.2227 0.1401 6.6340 0.7152 0.0748 0.1412 -0.0045 0.0146 0.0013 0.0146 -0.0102 0.0344 35 12/09/19 0.1247 0.1042 6.4270 0.5396 0.0270 0.0798 0.0048 0.0110 0.0059 0.0107 -0.0053 0.0278 36C 03/12/19 0.3336 0.2452 5.8830 0.5678 0.0141 0.0961 -0.0015 0.0102 0.0078 0.0100 0.0107 0.0253 36C 06/25/19 0.2867 0.1369 5.1410 0.6297 -0.1349 0.1156 0.0031 0.0129 -0.0020 0.0135 -0.0140 0.0325 36C 08/08/19 0.4402 0.2101 6.7180 0.6501 -0.0979 0.1387 -0.0094 0.0146 -0.0016 0.0141 0.0025 0.0340 36C 12/18/19 0.2184 0.1567 6.7950 0.6171 -0.0168 0.0925 -0.0040 0.0104 -0.0031 0.0104 0.0083 0.0276 C= Control location, Background location Results in bold type are positive.

3-28

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

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

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

29 03/14/19 -0.0033 0.0112 0.0131 0.0294 0.0072 0.0132 -0.0007 0.0222 -0.0114 0.0125 0.0683 0.1162 29 06/13/19 0.0053 0.0078 0.0081 0.0212 -0.0112 0.0111 0.0159 0.0160 0.0016 0.0089 -0.0154 0.0882 29 08/20/19 0.0049 0.0141 -0.0132 0.0370 0.0072 0.0136 -0.0036 0.0199 0.0037 0.0126 -0.0214 0.1253 29 12/09/19 0.0049 0.0110 -0.0263 0.0259 -0.0015 0.0091 -0.0010 0.0167 -0.0052 0.0082 -0.0495 0.0769 32 03/14/19 0.0137 0.0130 0.0234 0.0378 -0.0068 0.0138 0.0207 0.0240 -0.0050 0.0153 0.0098 0.1245 32 06/17/19 0.0028 0.0129 -0.0045 0.0282 -0.0022 0.0111 0.0062 0.0213 -0.0010 0.0109 -0.0370 0.1066 32 08/20/19 -0.0017 0.0181 0.0030 0.0401 0.0030 0.0154 0.0037 0.0295 0.0076 0.0151 0.0666 0.1468 32 10/23/19 -0.0020 0.0140 -0.1133 0.0529 -0.0101 0.0165 -0.0238 0.0254 -0.0095 0.0150 -0.0345 0.1411 35 03/14/19 0.0052 0.0148 0.0311 0.0374 -0.0060 0.0151 0.0136 0.0262 -0.0074 0.0169 0.0625 0.1438 35 06/11/19 0.0011 0.0116 0.0082 0.0244 0.0042 0.0106 0.0082 0.0175 0.0007 0.0099 -0.0402 0.0926 35 08/20/19 0.0067 0.0127 -0.0364 0.0338 0.0016 0.0140 -0.0094 0.0272 0.0044 0.0158 -0.0078 0.1229 35 12/09/19 0.0043 0.0110 -0.0227 0.0307 0.0068 0.0097 0.0004 0.0174 0.0008 0.0098 0.0009 0.0911 36C 03/12/19 -0.0018 0.0105 -0.0262 0.0266 0.0082 0.0121 -0.0041 0.0200 -0.0034 0.0109 -0.0214 0.0889 36C 06/25/19 0.0107 0.0163 -0.0201 0.0340 0.0110 0.0126 0.0150 0.0229 0.0054 0.0154 0.0702 0.1457 36C 08/08/19 0.0066 0.0166 -0.0374 0.0413 0.0009 0.0166 -0.0146 0.0264 0.0029 0.0136 -0.0255 0.1385 36C 12/18/19 0.0000 0.0136 0.0033 0.0328 0.0055 0.0123 -0.0058 0.0212 -0.0050 0.0103 0.0234 0.1117 C= Control location, Background location 3-29

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

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

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

29 03/14/19 0.0092 0.0123 -0.0047 0.0335 -0.0007 0.0206 -0.0017 0.0143 0.0039 0.0134 0.0241 0.0504 29 06/13/19 -0.0035 0.0082 0.0145 0.0224 -0.0086 0.0133 0.0011 0.0121 -0.0002 0.0099 0.0736 0.0762 29 08/20/19 -0.0017 0.0116 0.0280 0.0333 -0.0018 0.0198 0.0050 0.0147 -0.0037 0.0124 0.0187 0.0590 29 12/09/19 0.0017 0.0083 -0.0076 0.0217 -0.0021 0.0115 0.0063 0.0110 -0.0020 0.0093 0.0747 0.0414 32 03/14/19 -0.0020 0.0127 0.0211 0.0389 0.0132 0.0219 -0.0012 0.0155 0.0022 0.0143 0.0445 0.0568 32 06/17/19 0.0005 0.0116 -0.0056 0.0332 0.0138 0.0134 0.0008 0.0138 -0.0028 0.0125 0.0426 0.0515 32 08/20/19 -0.0036 0.0149 -0.0136 0.0390 -0.0016 0.0283 -0.0017 0.0172 0.0029 0.0157 0.0712 0.0674 32 10/23/19 -0.0146 0.0135 -0.0128 0.0343 0.0049 0.0232 0.0028 0.0157 0.0055 0.0160 0.0742 0.0682 35 03/14/19 0.0055 0.0144 0.0189 0.0396 0.0096 0.0253 -0.0051 0.0186 0.0031 0.0160 0.0630 0.0634 35 06/11/19 0.0002 0.0079 -0.0244 0.0240 0.0047 0.0161 -0.0004 0.0120 -0.0062 0.0111 0.0422 0.0432 35 08/20/19 -0.0148 0.0129 0.0002 0.0375 0.0074 0.0263 -0.0108 0.0162 0.0026 0.0158 0.0046 0.0558 35 12/09/19 -0.0023 0.0083 -0.0070 0.0286 0.0109 0.0131 0.0049 0.0119 0.0044 0.0102 0.0675 0.0523 36C 03/12/19 0.0024 0.0087 -0.0186 0.0296 0.0143 0.0182 0.0004 0.0109 -0.0009 0.0117 0.0834 0.0547 36C 06/25/19 -0.0125 0.0125 -0.0077 0.0427 -0.0032 0.0160 0.0077 0.0139 0.0088 0.0148 0.0758 0.0648 36C 08/08/19 -0.0157 0.0146 0.0156 0.0416 0.0114 0.0222 0.0073 0.0202 0.0109 0.0156 0.1095 0.0899 36C 12/18/19 -0.0003 0.0109 0.0268 0.0329 -0.0040 0.0127 0.0058 0.0131 0.0027 0.0118 0.0927 0.0540 C= Control location, Background location 3-30

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 13 FISH (pCi/g wet wt.)

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

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

32 04/17/19 -0.099 0.236 2.924 0.860 -0.085 0.242 0.012 0.030 -0.007 0.025 -0.029 0.049 32 10/23/19 -0.072 0.283 4.737 0.990 -0.130 0.271 0.002 0.032 0.003 0.035 -0.014 0.078 35 05/15/19 0.022 0.161 3.060 0.561 -0.072 0.172 0.002 0.020 -0.003 0.020 -0.006 0.034 35 08/06/19 0.170 0.290 2.647 0.939 0.200 0.331 0.020 0.034 -0.049 0.032 -0.055 0.062 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

32 04/17/19 0.012 0.029 -0.096 0.076 0.018 0.029 0.027 0.049 0.001 0.030 -0.081 0.273 32 10/23/19 0.007 0.040 -0.130 0.091 -0.017 0.034 0.035 0.053 0.035 0.036 0.305 0.301 35 05/15/19 0.017 0.023 -0.037 0.047 0.006 0.019 -0.020 0.033 0.017 0.019 -0.070 0.171 35 08/06/19 0.005 0.029 -0.010 0.089 -0.013 0.037 -0.014 0.061 0.021 0.037 0.062 0.330 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

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

32 04/17/19 -0.008 0.029 0.031 0.085 -0.015 0.044 -0.006 0.038 -0.001 0.031 -0.098 0.128 32 10/23/19 0.007 0.035 0.026 0.084 0.028 0.052 -0.018 0.035 0.008 0.039 0.157 0.137 35 05/15/19 -0.015 0.019 -0.024 0.055 0.012 0.024 -0.022 0.021 0.004 0.022 0.035 0.080 35 08/06/19 0.004 0.031 -0.002 0.099 -0.025 0.056 0.007 0.039 -0.014 0.037 -0.040 0.135 Results in bold type are positive.

3-31

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 14 OYSTERS (pCi/g wet wt.)

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

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

31 05/30/19 -0.139 0.287 2.288 0.785 -0.075 0.286 -0.025 0.033 -0.023 0.035 0.012 0.067 31 11/05/19 0.054 0.278 2.575 0.862 0.115 0.264 -0.023 0.035 0.006 0.037 0.044 0.062 89C 03/28/19 0.101 0.225 1.834 0.768 0.199 0.240 -0.005 0.026 -0.023 0.030 0.004 0.051 89C 10/29/19 -0.240 0.379 2.585 1.007 0.186 0.373 -0.051 0.046 0.017 0.041 0.048 0.084 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

31 05/30/19 -0.008 0.033 -0.031 0.080 -0.004 0.032 -0.017 0.060 -0.016 0.030 -0.312 0.289 31 11/05/19 0.021 0.028 -0.130 0.112 0.001 0.037 0.011 0.056 0.024 0.030 -0.075 0.294 89C 03/28/19 -0.004 0.025 -0.054 0.067 0.007 0.031 -0.005 0.045 -0.017 0.031 -0.271 0.240 89C 10/29/19 0.008 0.052 0.035 0.093 0.020 0.041 -0.005 0.079 -0.057 0.049 -0.365 0.464 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

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

31 05/30/19 0.000 0.027 -0.042 0.076 0.018 0.073 0.006 0.038 0.000 0.029 -0.069 0.118 31 11/05/19 -0.012 0.027 0.023 0.083 -0.011 0.046 0.018 0.035 0.023 0.033 0.017 0.134 89C 03/28/19 0.001 0.027 -0.071 0.061 0.036 0.046 -0.010 0.029 0.009 0.027 0.094 0.116 89C 10/29/19 0.030 0.043 0.117 0.129 -0.023 0.048 -0.001 0.052 0.008 0.052 -0.001 0.184 Results in bold type are positive.

C= Control location, Background location 3-32

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 15 CLAMS (pCi/g wet wt.)

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

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

29 06/12/19 0.064 0.214 1.539 0.727 -0.037 0.213 -0.003 0.023 -0.004 0.028 0.005 0.046 29 10/16/19 0.040 0.317 1.718 0.790 0.106 0.325 0.004 0.040 -0.026 0.040 -0.033 0.083 31 06/07/19 -0.137 0.220 1.573 0.616 0.234 0.253 0.021 0.028 0.006 0.028 -0.029 0.063 31 10/16/19 0.134 0.282 1.435 1.053 0.007 0.235 -0.014 0.038 0.034 0.033 0.028 0.046 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

29 06/12/19 -0.016 0.027 -0.048 0.051 0.024 0.026 -0.006 0.042 -0.016 0.026 0.049 0.201 29 10/16/19 0.050 0.044 -0.037 0.082 -0.025 0.038 -0.017 0.062 0.002 0.034 0.101 0.364 31 06/07/19 0.006 0.034 0.023 0.071 0.011 0.028 0.015 0.047 0.017 0.028 -0.208 0.273 31 10/16/19 -0.001 0.041 0.011 0.080 -0.005 0.033 -0.022 0.055 0.032 0.033 -0.123 0.293 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

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

29 06/12/19 -0.016 0.027 0.031 0.066 0.019 0.035 -0.008 0.030 0.017 0.026 0.000 0.105 29 10/16/19 -0.001 0.032 0.035 0.105 0.050 0.056 0.032 0.039 0.032 0.032 -0.044 0.173 31 06/07/19 -0.008 0.026 0.073 0.071 -0.070 0.060 0.005 0.032 0.028 0.027 0.005 0.101 31 10/16/19 -0.010 0.031 0.015 0.089 0.005 0.037 0.009 0.041 0.028 0.034 0.018 0.133 Results in bold type are positive.

3-33

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE 16 LOBSTERS (pCi/g wet wt.)

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

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

35 05/20/19 0.109 0.317 2.435 0.950 0.255 0.324 -0.021 0.039 -0.031 0.049 -0.029 0.072 35 08/06/19 -0.095 0.225 2.879 0.859 -0.107 0.228 0.015 0.031 -0.010 0.025 0.039 0.068 89C 06/25/19 0.028 0.209 2.446 1.066 -0.009 0.246 0.001 0.024 0.007 0.026 0.000 0.046 89C 08/08/19 0.110 0.237 3.117 0.849 0.116 0.221 0.013 0.034 -0.001 0.036 -0.018 0.062 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

35 05/20/19 -0.008 0.036 -0.215 0.102 0.021 0.042 -0.013 0.070 -0.001 0.041 -0.169 0.324 35 08/06/19 0.010 0.029 -0.041 0.080 0.009 0.029 0.008 0.050 -0.015 0.032 -0.018 0.216 89C 06/25/19 0.009 0.037 0.042 0.059 0.000 0.024 0.024 0.044 -0.012 0.026 0.113 0.243 89C 08/08/19 0.008 0.040 -0.129 0.087 -0.003 0.027 0.019 0.057 0.003 0.032 0.074 0.263 COLLECTION LOCATION DATE Ag-110M Sb-125 I-131 Cs-134 Cs-137 Ac-228

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

35 05/20/19 -0.033 0.037 -0.015 0.101 0.006 0.058 -0.010 0.039 0.019 0.040 0.012 0.139 35 08/06/19 -0.008 0.030 -0.014 0.076 0.009 0.047 -0.008 0.026 0.007 0.032 -0.037 0.117 89C 06/25/19 0.011 0.029 0.039 0.092 -0.001 0.033 0.004 0.030 -0.029 0.033 -0.062 0.143 89C 08/08/19 -0.016 0.025 -0.029 0.072 0.002 0.034 -0.011 0.032 0.007 0.029 0.004 0.112 C= Control Location, Background location Results in bold type are positive.

3-34

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

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 2019, there were three 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 2019 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 R/hr. The unit R 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, seven in 2019.

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

In 2019, the exposure rate measurement at Location 73 remains below the recorded background measurements, while Location 74 and Location 75 remain same. In 2019, the station offsite dose from ISFSI was 0.037 mrem/year, which is below the 25 mrem/year limit per 40.190 CFR.

4-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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.

The averages of all indicator locations for the period when Millstone MPS1 was still in operation (1996 to 1999) exhibit the effects of N-16 BWR turbine building skyshine to immediate areas onsite. Skyshine exposure rates are as high as 6 R/hr at onsite monitoring stations. The elevated exposure rates from skyshine decreased rapidly with distance to levels indistinguishable from normal background measurements at the nearest offsite monitoring stations. Also apparent in Figure 4.1-1 is a change of the type of TLD dosimeter in the year 2000. The difference in response between the two types of TLD dosimeters is apparent, with the new type reading 15% to 20% lower. This lower response is consistent for all locations, including both indicator and control locations.

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 out-croppings 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 2019 data for Location 3 shows an increase likely attributable to 1-3 R/hr gradients observed from the granite bedrock of the MPS Site21.

4-2

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 4-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 (see Figure 4.2-2). This indicates that any station contribution is not measurable.

44

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 2019 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 the lack of any station radioactivity.

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.

4-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 2019 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 2019, the Land Use Census did not locate any location of milk animals 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 2019. ISFSI well results have been documented in Table 7 as required by the Connecticut Sitting Council.

4.8 Fruits and Vegetables (Table 8)

Consistent with past years, this media did not show any station effects. Naturally occurring K-40 and cosmic produced Be-7 were 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 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.

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.

4-6

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 H-3 releases in the MPS liquid effluents versus the measured environmental concentrations from the vicinity of discharge location. In 2019 MPS had one outage requiring the processing and subsequent discharge of processed refueling water, which explains the slightly elevated H-3 activity values in the second quarter of 2019. The highest quarterly average H-3 value in 2019 for seawater was 2,234 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 2019 was 0.001 mrem/yr.

4-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 4.11 Bottom Sediment (Table 11)

There was no station related radioactivity detected in bottom sediment samples in 2019.

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 2019 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 2019.

4.15 Clams (Table 15)

Occasionally this media indicates the presence of station related radioactivity. In 2019 no activity was observed except for the naturally occurring K-40.

4.16 Lobsters (Table 16)

In 2019 no activity was observed except for the naturally occurring K-40.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

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 Nuclear Power Station Unit 1 Defueled Technical Specifications.

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

11) Millstone Nuclear 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 Nuclear 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 Location s Greater Than 10 Miles From Millstone Site, July 28, 1998.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station APPENDIX A LAND USE CENSUS FOR 2019 A-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station 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 2018 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 2018 sources of food locations were identified.

The 2019 Land Use Census also evaluated aquatic sampling exposure pathways from the fish and shell fish located around MPS. Figure A-2 shows shellfish beds around MPS from the Bureau of Aquaculture of the Department of Agriculture. The salt water fishing areas are identified Figure A-3. No changes from the 2018 aquatic sampling exposure pathways were identified.

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

A-2

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station TABLE A-1 2019 Survey Downwind Resident/Garden1 Direction miles meters N 0.95 1521 NNE 0.53 854 NE 0.47 763 ENE 0.97 1554 E 0.92 1475 ESE 1.06 1701 SE2 N/A N/A SSE2 N/A N/A 2

S N/A N/A 2

SSW 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.

A-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Table A-2 Milk and other foods within Ten miles of Millstone - 2019 Sector Miles Business Location Comments NW 1.95 Smith's Acres Niantic Fruits and vegetables Has a goat but currently not producing NE 1.96 Mingo Goat Waterford milk ENE 3.0 Secchiaroli Farms Waterford Has pigs but are fed non local sources WNW 5.0 Four Mile River Farm Old Lyme Eggs, Meat Scott's Yankee NW 5.2 East Lyme Fruits, vegetables, and cider Farmer Vegetables, Herbs, Eggs, Meat, NNW 5.3 White Gate Farm East Lyme Nursery and Flowers NNW 6.24 Trinity Farm Enfield Farmers Market 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 a goat but not producing milk ENE 7.5 Groton Family Farm Groton Vegetables, Honey, Maple, Eggs, Fiber Fruits, vegetables, cows, goats, and NE 8.3 Red Fence Farm Groton pig. Cows and goats currently not producing milk A-4

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Figure A-1 Farms and Goats Products within ten miles of Millstone A-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Figure A-2 Shellfish Beds in Vicinity of Millstone Millstone Site A-6

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Figure A-3 Millstone A-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station APPENDIX B

SUMMARY

OF INTERLABORATORY COMPARISONS C-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Summary of Results - Inter-laboratory Comparison Program (ICP)

The TBE Laboratory analyzed Performance Evaluation (PE) samples of air particulate, 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.1 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.

A.2 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.

A.3 DOE Evaluation Criteria MAPEPs evaluation report provides an acceptance range with associated flag values.

MAPEP defines three levels of performance:

x Acceptable (flag = A) - result within +/- 20% of the reference value x Acceptable with Warning (flag = W) - result falls in the +/- 20% to +/- 30% of the reference value x 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, 119 out of 129 analyses performed met the specified acceptance criteria. Ten 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 ERA April 2019 water Cs-134 result was evaluated as Not Acceptable. The reported value was 15.2 pCi/L (error 2.82 pCi/L) and the known result was 12.1 pCi/L (acceptance range of 8.39 - 14.4 pCi/L). With the error, the reported result overlaps the acceptable range. This sample was run as the workgroup duplicate on a different detector with a result of 10.7 pCi/L (within acceptable range). (NCR 19-10)

2. The ERA April 2019 water Sr-89 result was evaluated as Not Acceptable. The reported value was 44.9 pCi/L and the known result was 33.3 pCi/L (acceptance range of 24.5 -

40.1 pCi/L). The sample was only counted for 15 minutes instead of 200 minutes. The sample was re-prepped in duplicate and counted for 200 minutes with results of 30.7 +/-

5.37 pCi/L and 33.0 +/- 8.71 pCi/L. This was the 1st high failure for Sr-89 in 5 years.

(NCR 19-11)

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

3. The MAPEP February 2019 soil Sr-90 result was not submitted and therefore evaluated as Not Acceptable. The sample was run in duplicate, with results of -1.32 +/- 4.09 Bq/kg

(<6.87) and -1.030 +/- 3.55 Bq/kg (<5.97). The known result was a false positive test (no significant activity). TBE did not submit a result because it appeared that the results may not be accurate. TBE analyzed a substitute soil Sr-90 sample from another vendor, with a result within the acceptable range. (NCR 19-12)

4. The MAPEP February 2019 water Am-241 result was evaluated as Not Acceptable.

The reported value was 0.764 +/- 0.00725 Bq/L with a known result of 0.582 Bq/L (acceptable range 0.407 - 0.757 Bq/L). TBEs result falls within the upper acceptable range with the error. It appeared that a non-radiological interference was added and lead to an increased mass and higher result. (NCR 19-13)

5. The MAPEP February 2019 vegetation Sr-90 result was evaluated as Not Acceptable.

The reported result was -0.1060 +/- 0.0328 Bq/kg and the known result was a false positive test (no significant activity). TBEs result was correct in that there was no activity. MAPEPs evaluation was a statistical failure at 3 standard deviations. (NCR 19-14)

6. The ERA October 2019 water Gross Alpha result was evaluated as Not Acceptable.

TBEs reported result was 40.5 +/- 10.3 pCi/L and the known result was 27.6 pCi/L (ratio of TBE to known result at 135%). With the associated error, the result falls within the acceptable range (14.0 - 36.3 pCi/L). The sample was run as the workgroup duplicate on a different detector with a result of 30.8 +/- 9.17 pCi/L (within the acceptable range).

This was the first failure for drinking water Gr-A since 2012. (NCR 19-23)

7. The ERA October 2019 water Sr-90 result was evaluated as Not Acceptable. TBEs reported result was 32.5 +/- 2.12 pCi/L and the known result was 26.5 pCi/L (ratio of TBE to known result at 123%). With the associated error, the result falls within the acceptable range (19.2 - 30.9 pCi/L). The sample was run as the workgroup duplicate on a different detector with a result of 20.0 +/- 1.91 pCi/L (within the acceptable range).

Both TBE results are within internal QC limits. A substitute quick response sample was analyzed with an acceptable result of 18.6 pCi/L (known range of 13.2 - 22.1 pCi/L). (NCR 19-24)

8. The MAPEP August 2019 soil Ni-63 result of 436 +/- 22.8 Bq/kg was evaluated as Not Acceptable. The known result was 629 Bq/kg (acceptable range 440 - 818 Bq/sample).

With the associated error, the TBE result falls within the lower acceptance range. All associated QC was acceptable. No reason for failure could be found. This is the first failure for soil Ni-63 since 2012. (NCR 19-25).

9. The MAPEP August 2019 water Am-241 result was not reported and therefore evaluated as Not Acceptable. Initial review of the results showed a large peak where Am-241 should be (same as the February, 2019 sample results). It is believed that Th-228 was intentionally added as interference. The sample was re-prepped and analyzed using a smaller sample aliquot. The unusual large peak (Th-228) was seen again and also this time a smaller peak (Am-241). The result was 436 +/- 22.8 Bq/L (acceptable range 0.365 +/- 0.679 Bq/L). Th-228 is not a typical nuclide requested by clients, so there is no analytical purpose to take samples through an additional separation step.

TBE will pursue using another vendor for Am-241 water cross-checks that more closely reflects actual customer samples. (NCR 19-26)

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station

10. The Analytics September 2019 soil Cr-51 sample was evaluated as Not Acceptable.

TBEs reported result of 0.765 +/- 0.135 pCi/g exceeded the upper acceptance range (140% of the known result of 0.547 pCi/g). The TBE result was within the acceptable range (0.63 - 0.90 pCi/g) with the associated error. The Cr-51 result is very close to TBEs normal detection limit. In order to get a reportable result, the sample must be counted for 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> (10x longer than client samples). There is no client or regulatory requirement for this nuclide and TBE will remove Cr-51 from the reported gamma nuclides going forward. (NCR 19-27)

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

C-4

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station A.1 Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Identification Known Ratio of TBE to (b)

Month/Year Matrix Nuclide Units Reported (a) Evaluation Number Value Analytics Result Value March 2019 E12468A Milk Sr-89 pCi/L 87.1 96 0.91 A Sr-90 pCi/L 12.6 12.6 1.00 A E12469A Milk Ce-141 pCi/L 113 117 0.97 A Co-58 pCi/L 153 143 1.07 A Co-60 pCi/L 289 299 0.97 A Cr-51 pCi/L 233 293 0.80 A Cs-134 pCi/L 147 160 0.92 A Cs-137 pCi/L 193 196 0.98 A Fe-59 pCi/L 153 159 0.96 A I-131 pCi/L 91.5 89.5 1.02 A Mn-54 pCi/L 149 143 1.04 A Zn-65 pCi/L 209 220 0.95 A E12470 Charcoal I-131 pCi 77.5 75.2 1.03 A E12471 AP Ce-141 pCi 60.7 70.2 0.87 A Co-58 pCi 87.9 85.8 1.02 A Co-60 pCi 175 179 0.98 A Cr-51 pCi 165 176 0.94 A Cs-134 pCi 91.2 95.9 0.95 A Cs-137 pCi 120 118 1.02 A Fe-59 pCi 108 95.3 1.13 A Mn-54 pCi 94.2 85.7 1.10 A Zn-65 pCi 102 132 0.77 W E12472 Water Fe-55 pCi/L 2230 1920 1.16 A E12473 Soil Ce-141 pCi/g 0.189 0.183 1.03 A Co-58 pCi/g 0.209 0.224 0.93 A Co-60 pCi/g 0.481 0.466 1.03 A Cr-51 pCi/g 0.522 0.457 1.14 A Cs-134 pCi/g 0.218 0.250 0.87 A Cs-137 pCi/g 0.370 0.381 0.97 A Fe-59 pCi/g 0.263 0.248 1.06 A Mn-54 pCi/g 0.248 0.223 1.11 A Zn-65 pCi/g 0.371 0.344 1.08 A E12474 AP Sr-89 pCi 88.3 95.2 0.93 A Sr-90 pCi 11.7 12.5 0.94 A August 2019 E12562 Soil Sr-90 pCi/g 4.710 6.710 0.70 W (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 C-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station A.1 Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Identification Known Ratio of TBE to (b)

Month/Year Matrix Nuclide Units Reported (a) Evaluation Number Value Analytics Result Value September 2019 E12475 Milk Sr-89 pCi/L 70.0 93.9 0.75 W Sr-90 pCi/L 12.0 12.9 0.93 A E12476 Milk Ce-141 pCi/L 150 167 0.90 A Co-58 pCi/L 170 175 0.97 A Co-60 pCi/L 211 211 1.00 A Cr-51 pCi/L 323 331 0.98 A Cs-134 pCi/L 180 207 0.87 A Cs-137 pCi/L 147 151 0.97 A Fe-59 pCi/L 156 148 1.05 A I-131 pCi/L 81.1 92.1 0.88 A Mn-54 pCi/L 160 154 1.04 A Zn-65 pCi/L 303 293 1.03 A E12477 Charcoal I-131 pCi 95.9 95.1 1.01 A E12478 AP Ce-141 pCi 129 138 0.93 A Co-58 pCi 128 145 0.88 A Co-60 pCi 181 174 1.04 A Cr-51 pCi 292 274 1.07 A Cs-134 pCi 166 171 0.97 A Cs-137 pCi 115 125 0.92 A Fe-59 pCi 119 123 0.97 A Mn-54 pCi 129 128 1.01 A Zn-65 pCi 230 242 0.95 A E12479 Water Fe-55 pCi/L 1810 1850 0.98 A E12480 Soil Ce-141 pCi/g 0.305 0.276 1.10 A Co-58 pCi/g 0.270 0.289 0.93 A Co-60 pCi/g 0.358 0.348 1.03 A Cr-51 pCi/g 0.765 0.547 1.40 N (1)

Cs-134 pCi/g 0.327 0.343 0.95 A Cs-137 pCi/g 0.308 0.321 0.96 A Fe-59 pCi/g 0.257 0.245 1.05 A Mn-54 pCi/g 0.274 0.255 1.07 A Zn-65 pCi/g 0.536 0.485 1.11 A E12481 AP Sr-89 pCi 95.9 91.9 1.04 A Sr-90 pCi 12.3 12.6 0.97 A E12563 Soil Sr-90 pCi/g 0.392 0.360 1.09 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 19-27 C-6

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station A.2 DOE's Mixed Analyte Performance Evaluation Program (MAPEP)

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

Number Value (a) Range Value February 2019 19-GrF40 AP Gross Alpha Bq/sample 0.184 0.528 0.158 - 0.898 A Gross Beta Bq/sample 0.785 0.948 0.474 - 1.422 A 19-MaS40 Soil Ni-63 Bq/kg 420 519.0 363 - 675 A Sr-90 Bq/kg (1) NR (3) 19-MaW40 Water Am-241 Bq/L 0.764 0.582 0.407 - 0.757 N (4)

Ni-63 Bq/L 4.72 5.8 4.1 - 7.5 A Pu-238 Bq/L 0.443 0.451 0.316 - 0.586 A Pu-239/240 Bq/L -0.00161 0.0045 (2) A 19-RdF40 AP U-234/233 Bq/sample 0.1138 0.106 0.074 - 0.138 A U-238 Bq/sample 0.107 0.110 0.077 - 0.143 A 19-RdV40 Vegetation Cs-134 Bq/sample 2.14 2.44 1.71 - 3.17 A Cs-137 Bq/sample 2.22 2.30 1.61 - 2.99 A Co-57 Bq/sample 2.16 2.07 1.45 - 2.69 A Co-60 Bq/sample 0.02382 (1) A Mn-54 Bq/sample -0.03607 (1) A (5)

Sr-90 Bq/sample -0.1060 (1) N Zn-65 Bq/sample 1.35 1.71 1.20 - 2.22 W August 2019 19-GrF41 AP Gross Alpha Bq/sample 0.192 0.528 0.158 - 0.898 W Gross Beta Bq/sample 0.722 0.937 0.469 - 1.406 A (6) 19-MaS41 Soil Ni-63 Bq/kg 436 629 440 - 818 N Sr-90 Bq/kg 444 572 400 - 744 W 19-MaW41 Water Am-241 Bq/L NR (7)

Ni-63 Bq/L 7.28 9.7 6.8 - 12.6 W Pu-238 Bq/L 0.0207 0.0063 (2) A Pu-239/240 Bq/L 0.741 0.727 0.509 - 0.945 A 19-RdF41 AP U-234/233 Bq/sample 0.0966 0.093 0.065 - 0.121 A U-238 Bq/sample 0.0852 0.096 0.067-0.125 A 19-RdV41 Vegetation Cs-134 Bq/sample 0.0197 (1) A Cs-137 Bq/sample 3.21 3.28 2.30 - 4.26 A Co-57 Bq/sample 4.62 4.57 3.20 - 5.94 A Co-60 Bq/sample 4.88 5.30 3.71 - 6.89 A Mn-54 Bq/sample 4.54 4.49 3.14 - 5.84 A Sr-90 Bq/sample 0.889 1.00 0.70 - 1.30 A Zn-65 Bq/sample 2.78 2.85 2.00 - 3.71 A (a) The MAPEP known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation (b) 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 19-12 (4) See NCR 19-13 (5) See NCR 19-14 (6) See NCR 19-25 (7) See NCR 19-26 C-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station A.3 ERA Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Identification Known Acceptance (b)

Month/Year Matrix Nuclide Units Reported (a) Evaluation Number Value Limits Value April 2019 Rad-117 Water Ba-133 pCi/L 26.3 24.1 18.6 - 27.8 A (1)

Cs-134 pCi/L 15.2 12.1 8.39 - 14.4 N Cs-137 pCi/L 33.6 33.1 28.8 - 39.4 A Co-60 pCi/L 11.9 11.5 8.67 - 15.5 A Zn-65 pCi/L 87.1 89.2 80.3 - 107 A GR-A pCi/L 19 19.3 9.56 - 26.5 A GR-B pCi/L 20.2 29.9 19.1 - 37.7 A U-Nat pCi/L 55.5 55.9 45.6 - 61.5 A H-3 pCi/L 21500 21400 18700 - 23500 A Sr-89 pCi/L 44.9 33.3 24.5 - 40.1 N (2)

Sr-90 pCi/L 24.5 26.3 19.0 - 30.7 A I-131 pCi/L 28.9 28.4 23.6 - 33.3 A October 2019 Rad-119 Water Ba-133 pCi/L 42.7 43.8 35.7 - 48.8 A Cs-134 pCi/L 53.5 55.9 45.2 - 61.5 A Cs-137 pCi/L 77.7 78.7 70.8 - 89.2 A Co-60 pCi/L 51.5 53.4 48.1 - 61.3 A Zn-65 pCi/L 36.6 34.0 28.5 - 43.1 A GR-A pCi/L 40.5 27.6 14.0 - 36.3 N (3)

GR-B pCi/L 36.3 39.8 26.4 - 47.3 A U-Nat pCi/L 27.66 28.0 22.6 - 31.1 A H-3 pCi/L 22800 23400 20500 - 25700 A Sr-89 pCi/L 47.1 45.5 35.4 - 52.7 A (4)

Sr-90 pCi/L 32.5 26.5 19.2 - 30.9 N I-131 pCi/L 26.0 23.9 19.8 - 28.4 A December 2019 QR 120419D Water Sr-90 pCi/L 20.1 18.6 13.2 - 22.1 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 19-10 (2) See NCR 19-11 (3) See NCR 19-23 (4) See NCR 19-24 C-8

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station APPENDIX C ERRATUM C-9

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2019 Millstone Power Station Erratum- Correction to Previously Published Annual Radiological Environmental Operating Report In the 2019 Annual Radiological Environmental Operating Report there were no correction identified to previously published Annual Radiological Environmental Operating Reports.

C-10