Text

Submittal of 2017 Annual Radiological Environmental Operating Report
	ML18128A196
Person / Time
Site:	Millstone
Issue date:	05/01/2018
From:	O'Connor M; Dominion Energy Nuclear Connecticut
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	18-175
	Download: ML18128A196 (92)
	v • d • e

Dominion Energy Nu clear Connecticut, Inc.

Rt 156, Rope Ferry Road, Waterford, CT 06385 Dominion Energy.com U.S. Nuclear Regulatory Commission Serial No.18-175 Attention: Document Control Desk MAY O 1 2018 MPS Lic/GJC RO Washington , DC 20555-0001 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-2 1 DPR-65 NPF-49 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNITS 1, 2, AND 3 2017 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT Th is letter transm its the Ann ual Radiological Environmental Operating Report for the Millstone Power Station , for the period January 2017 through December 2017. This satisfies the provisions of Section 5.7.2 of Millstone Power Station Unit 1 Permanently Defueled Techni cal 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.

If you have any questions or require add itional information , please contact Mr.

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

Sincerely,

~\Ju_~

M. J. O'Connor Director, Nuclear Station Safety and Licensing

Serial No.18-175 2017 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 S. J. Giebel NRC Project Manager Millstone Unit 1 U.S. Nuclear Regulatory Commission Two White Flint North, Mail Stop T-8 F5 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 H. W Anagnostopoulos 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.18-175 2017 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 R. Stein Chairman Connecticut Siting Council 10 Franklin Square New Britain , CT 06051 J.P. Kelley Waterford-East Lyme Shellfish Commission Waterford Town Hall Waterford , CT 06385 S. Brietmaier American Nuclear Insurers 95 Glastonbury Blvd.

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

Serial No.18-175 2017 Annual Radiological Environmental Operating Report Page 4 of 4 D. Steward 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.18-175 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 ATTACHMENT 1 2017 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MILLSTONE POWER STATION UNITS 1, 2, AND 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DENC)

Millstone Power Station 2017 Radiological Environmental Operating Report January 1, 2017-December 31, 2017 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 2017 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. Annu al Radio logica l Enviro nm ental Operating Report 2017 Millston e 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. RADIOCHEMICAL RESULTS ............ ............ .......... ...... ...... ......... .. .... ........... 3-1 3.1

SUMMARY

TABLE ............... .............. .. .. .... ... .... ...... ... .. ... .. ... ... ...... .. . 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) ...... .. .. .. ........................ .. .. .. .................. .4-7 4.12 Aquatic Flora (Table 12). ........ .... ...................... .. .. ...... ...... .... .. .... ...... 4-8 4.13 Fish (Tables 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 2017 .............. .. .... .... ........ .. ............... A-1 APPENDIX B -

SUMMARY

OF INTERLABORATORY COMPARISONS ........... 8-1 APPENDIX C - ERRATUM - Correction to MPS 2016 AREOR .... .... .. .. .. ...... .. .. .. C-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station

Dominion Nuclear Conn ecticut, In c. Annu al Rad iological Enviro nmental Operating Report 2017 Millstone Power Stat ion 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 , 2017. 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, cow and goat milk, well water, broadleaf vegetation, fruits and vegetables, seawater, bottom sediment, aquatic flora , fish , oysters, clams , and lobster.

During 2017, there were 485 samples collected from the atmospheric, aquatic, and terrestrial environments. In addition, 155 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. Typically the cow milk locations are identified by a review of the annual registration information obtained from the State of Connecticut Department of Agriculture.

The nearest garden has been conservatively assumed to be located at the nearest residence . Although broadleaf sampling was performed and may be used in lieu of a garden census, gardens were included in the 2017 census . Only vegetable gardens having an area of more than 500 square feet need to be 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. The American Dairy Goat Association list and drive by inspection are used to in the selection process of goats for the Goat Pathway. For 2017 only one goat was available and this goat provided milk for sampling.

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.

Dom inion Nucl ear Connecticut, Inc. Annual Radiological Environm ental Op era ting Report 2017 Millstone Power Stati on The seawater exiting the stations quarry is monitored for tritium , a station generated radionuclide. Monitoring of seawater in the area of the discharge indicated the presence of tritium , a station related radionuclide. Tritium was only found in seawater onsite inside the mixing zone of the quarry discharge at levels that were expected from routine station operation.

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

RADIOLOGICAL IMPACT TO THE GENERAL PUBLIC During 2017, 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 general public from radioactive effluents and ambient radiation resulting from MPS operations for 2017 was approximately 0.31 mrem* for the year. This conservative estimate is well below the Environmental Protection Agency's (EPA) annual dose limit to any member of the general public and is a fraction of a percent of the typical dose received from natural and other sources of man-made radiation .

CONCLUSIONS The 2017 REMP for MPS resulted in the collection and analysis of 640 environmental samples and measurements. The data obtained were used to determine the impact of Millstone's operation on the environment and on the general public.

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

Based on this information , there is no significant radiological impact on the environment or on the general public due to Millstone's operation. The term 'mrem ' used in this report is a unit of radiation dose. 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.

ii

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 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 REMP for 2017 performed by Dominion Energy Nuclear Connecticut (DENC) for MPS is discussed in this report. Since the operation of a nuclear power station results in the release of small amounts of radioactivity and low levels of radiation , the Nuclear Regulatory Commission (NRC) requires by regulations and technical specifications that a program be established to monitor radiation and radioactivity in the environment (References 1, 6, 9, 10, & 11 ). This report, published annually per Millstone's Technical Specifications (section 5.7.2 for MPS1, section 6.9.1.6A for MPS2 and Section 6.9.1.3 for MPS3), summarizes the results of measurements of radiation and radioactivity in the environment in the vicinity of the MPS and at distant locations during the period January 1 to December 31 , 2017.

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, cow and goat milk, well water, broadleaf vegetation, fruits, vegetables, seawater, bottom sediment, aquatic flora, fish, oysters, clams and lobster.

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.

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 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 1980's because of the increased usage of medical procedures involving exposure to radiation (see 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 Radiation Sources and Corresponding Approximate Doses (1)

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

Internal, inhalation( l 2

~28 Medica1(3l 300 External, space 33 Consumer(4l 13 Internal, ingestion ~9 Industrial, security, 0.3 educational, research External, terrestrial ~1 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

Dom inion Nucl ear Conn ecti cut, Inc. An nual Radiologi cal Environ mental Op erating Repo rt 2017 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-? 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 2017, with the exception of refueling outages in April for MPS2 and October/November for MPS3. The annual capacity factor for MPS2 was 89.0% and for MPS3 was 91 .7%.

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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Domin ion Nuclear Conn ecticut, In c. Annual Radio logical Environm ental Ope ratin g Repo rt 2017 Mi llston e 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, wh ile nuclear stations use uranium fission in a nuclear reactor.

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

The operation of a nuclear reactor results in the release of small amounts of radioactivity and low levels of radiation . The radioactivity originates from two major sources, radioactive fission products and radioactive activation products . Radioactive fission products, as illustrated in Figure 1.4-1 , originate from the fissioning of the nuclear fuel. These fission products get into the reactor coolant from their release by minute amounts of uranium on the outside surfaces of the fuel cladding , by diffusion through the fuel pellets and cladding and, on occasion, through defects or failures in the fuel cladding . These fission products circulate along with the reactor coolant water and will deposit on the internal surfaces of pipes and equipment. The radioactive fission products on the pipes and equipment emit radiation.

Examples of some fission products are krypton-85 (Kr-85), strontium-90 (Sr-90), iodine-131 (1-131), xenon-133 (Xe-133), and cesium-137 (Cs-137).

SIMPLIFIED DIAGRAM OF A PRESSURIZED WATER REACTOR Pressuri zed water reactor-

a. common type of Light Wa ter Reactor (LWR)

TURB IN£ ENERAT OR C O N D ENSER C.OOUNG WA1"£R l'AIUNO.

w .+.s-re H EAT TO T H E EM'VLR<>NM EN T Figure 1.4-1 1-4

Domi nion Nuclea r Conn ecticut, In c. Annu al Radiological Environmental Op erating Report 2017 Millston e Power St ation Nuclear Fission Fission is the spl itting 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 (see Figure 1.4-2).

1.,...

Uranium Neutrons

'1 L Neutron iI **------ ...

Uranium *""-.2', 7".<P

~

Fission Products -

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

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station Radioactive activation products (see 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. So, activation products are nothing more than ordinary naturally-occurring atoms that are made unstable or radioactive by neutron bombardment. These activation products circulate along with the reactor coolant water and will deposit on the internal surfaces of pipes and equipment. The radioactive activation products on the pipes and equipment emit radiation. Examples of some activation products are manganese-54 (Mn-54), iron-59 (Fe-59), cobalt-60 (Co-60), and zinc-65 (Zn-65).

collision with 8 Co-59 Co-60 Stable Radioactive Neutron Cobalt Nucleus Cobalt Nucleus Figure 1.4-3 Radioactive Activation Product Formation At MPS there are five independent protective barriers that confine these radioactive materials. These five barriers are:

fuel pellets;

fuel cladding;

reactor vessel and associated piping and equipment;

primary containment and,

secondary containment (enclosure building).

1-6

Dom inion Nucl ear Connecticut, Inc. Annual Rad iological Environmental Op erat ing Repo rt 2017 Millston e 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 rad ioactivity in the primary coolant and the reactor core. However, during the course of operations and maintenance, small amounts of radioactive fission and activation products can escape through valve leaks or upon breaching of the primary coolant system for maintenance.

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

The fifth barrier is the secondary containment or enclosure building . The enclosure building is a steel building that surrounds the primary containment. This barrier is an additional safety feature at Millstone's reactor units to contain radioactivity that may escape from the primary containment. This enclosure building is equipped with a filtered ventilation system that is used when needed to reduce the radioactivity that escapes from the primary containment.

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

1-7

Dom ini on Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 M illstone 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:

reactor water cleanup system ;

liquid radioactive waste treatment system;

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

liquid waste effluent discharge radioactivity monitor.

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

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

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

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

This liquid waste effluent discharge line is provided with a shielded radioactivity monitor. This detector is connected to a radiation level meter and a recorder in the Control Room. The radiation alarm is set so that the detector will alarm before radioactivity levels exceed the release limits. In addition to the alarm function the radiation monitor also signals both discharge valves to close thus terminating the discharge release to the environment.

Gamma spectroscopy analysis, tritium analysis and the effluent radiation monitors prevent any liquid radioactivity from being released in excess of release rate and total activity limits.

An audible alarm notifies the Control Room operator that this has occurred.

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

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

1-8

Dom inion Nuclear Conn ecticut, Inc. Annu al Radiological Environmental Operating Report 2017 M illston e Powe r Stati on The preceding discussion illustrates that many controls exist to reduce the radioactive liquid effluents released to the environment to as far below the release limits as is reasonably achievable.

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

containment building ventilation system ;

containment building radioactivity monitors;

sampling and analysis of containment building vent and purge effluents;

process gas treatment system;

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

MPS stack and units' vent effluent radioactivity monitors;

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

process radiation monitors; and

steam jet air ejector (SJAE) monitor The primary sources of gaseous radioactive waste are degassing of the primary coolant, gaseous liquid drains, and gaseous vents . Additional sources of gaseous waste activity include ventilation air released from the auxiliary building and purging and venting of the containment building . The radiation level meter and recorders for the effluent radioactivity monitors are located in the Control Room. The station process computer aids in tracking the monitor readings. To supplement the information continuously provided by the detector, air samples are taken periodically from the units' containments, MPS stack and units' vents.

These samples are analyzed to quantify the total amount of radioactive gases, radioactive iodines, radioactive particulate and tritium released in gaseous effluents.

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

Gaseous waste at MPS3 is purified through a process gas system , consisting of high-efficiency particulate air filters and charcoal absorber beds. Gases from periodic venting of the MPS2 containment are released through a similar process system (Enclosure Building Filtration System) while gases from the MPS3 containment vacuum pumps are released without treatment. If necessary, MPS3 containment air can be filtered by an internal particulate and charcoal treatment system . Containment purges (purge is the forced ventilation process while containment vents are pressure releases) for MPS2 are filtered by high-efficiency particulate filters while at MPS3 these are not normally filtered . If necessary, particulate and charcoal filters can be used for these purges.

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

1-9

Dom inion Nuclea r Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 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 MPS's radioactive effluents. The purpose of this calculation is to periodically assess the dose to the general public resulting from radioactive effluents to ensure that the dose is being maintained as far below the federal dose limit as is reasonably achievable. This is the second stage for assessing releases to the environment.

The types and quantities of radioactive liquid and gaseous effluents released from MPS during each year are reported to the NRG annually in the Radiological Effluent Release Report (RERR). Similar to this report, the RERR is submitted annually to the NRG. The liquid and gaseous effluents were well below the federal release limits and were a small percentage of the MPS REMODGM 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.

1-10

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Mi llstone Power Station EXAMPLES OF MPS's RADIATION EXPOSURE PATHWAYS LIQUID EFFLUENTS Jo

3. DIRECT RADIATION (STATION) 2. AIR INHALATION

1. DIRECT RADIATION I

,! c/ (AIR SUBMERSION)

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

2. DIRECT RADIATION (IMMERSION IN OCEAN, BOATING , SWIMMING)

INGESTION

3. CONSUMPTION (FISH, SHELLFISH)

~

INGESTION Figure 1.6 Radiation Exposure Pathways 1-11

Dominion Nucl ear Connecticut, Inc. Annua l Rad iological Environm enta l Op erating Report 2017 Millstone Power Station There are four pathways in wh ich liquid effluents affect humans:

external radiation from liquid effluents that deposit and accumulate 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 NRG-recommended models that tend to result in over-estimates of the resulting dose. These computerized dose calculations are performed by DNC 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

Dom inion Nucl ear Conn ecticut , Inc. An nual Radiological Environmental Operati ng Repo rt 2017 Millston e Power Sta tion After dose calculations are performed, the results are compared to the dose limits for the public as specified in NRC's technical specifications for MPS (References 9-11 ).

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

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

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

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

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

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

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

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

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

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

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

1-13

Dominion Nucl ear Conn ecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station

2. PROGRAM DESCRIPTION 2.1 Sampling Schedule and Locations The sample locations and the sample types and frequency of analysis are given in Tables 2-1 and 2-2 and shown in Figures 2.1 and 2.2 . The program as described on Table 2-2 only lists the required samples as specified in the REMODCM. However, in order to identify the locations of the extra samples, all locations (both required and extra) are listed in Table 2-1.

2-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station Table 2-1 Envjronmental Monjtorjna Program sampling Types and Locatjons No.- Distance, Direction Location Name Sample Media Type* From Release Point**

1-1 Onsite - NAP Parking Lot N 0.6 Mi, NNW TLD , Air Particulate , Iodine, Vegetation 2-1 Onsite -Weather Shack 0.3 Mi , S TLD , Air Particulate, Iodine 3-1 Onsite - Bird Sanctuary 0.3 Mi , NE TLD, Air Particulate , Iodine, Soil 4-1 Onsite - Albacore Drive 1.0 Mi , N TLD , Air Particulate , Iodine, Soil 5-1 Onsite - Quarry East 0.1 Mi , SSE TLD 6-1 Onsite - Quarry Discharge 0.3 Mi , SSE TLD 7-1 Onsite - Env. Lab Dock 0.3 Mi, SE TLD 8-1 Onsite - Env. Lab 0.3 Mi, SE TLD 9-1 Onsite - Bay Point Beach 0.4 Mi , W TLD 10-1 Goshen Fire Dept. 1.2 Mi, E TLD, Air Particulate, Iodine, Vegetation 11-1 Great Neck Country Club 1.6 Mi, ENE TLD, Air Particulate , Iodine 13-C Mystic, CT 11 .5 Mi , ENE TLD 14-C Ledyard, CT 12.0 Mi, NE TLD, Soil 15-C Norwich, CT 14.0 Mi , N TLD , Air Particulate, Iodine 16-C Old Lyme, CT - Halls Rd. 8.8Mi,W TLD 17-1 Site Boundary 0.5 Mi, NE Vegetation 25-1,X Fruits & Vegetables < 10 Miles Vegetation 26-C, X Fruits & Vegetables > 10 Miles Vegetation 27-1 East Lyme Police Dept. 1.7 Mi , WNW TLD, Air Particulate, Iodine 28-1 Two Tree Island 0.8 Mi, SSE Fish 1 29-1 ,X West Jordan Cove ::;0.5 Mi , ENE to ESE 1 Clams, Fucus, Fish 0.4 Mi , ENE-ESE 31-1 Niantic Shoals 1.8 Mi , NW Bottom Sediment, Clams 32-1 Vicinity of Discharge Bottom Sediment, Fish 1 , Seawater, Fucus 33-1 Seaside Point 1.8 Mi , ESE Bottom Sediment 35-1 , X Niantic Bay :s;0.5 Mi , SSW to W 1 Lobster, Fucus, Fish 36-C, X Black Point 2.7 Mi, WSW Fucus 37-C Giant's Neck 3.5Mi , WSW Bottom Sediment, Seawater 41-1 Waterford - Myrock Avenue 3.2 Mi , ENE TLD 42-1 East Lyme - Billow Road 2.4 Mi , WSW TLD 43-1 East Lyme-Old Black Point 2.6 Mi , SW TLD 44-1 Onsite - Schoolhouse 0.1 Mi , NNE TLD 45-1 Onsite - Access Road #1 0.5 Mi , NNW TLD 46-1 Old Lyme - Hillcrest Ave. 4.6Mi,WSW TLD 47-1 East Lyme - W . Main St. 4.5Mi , W TLD 48-1 East Lyme- Corey&Roxbury Rd . 3.4 Mi, WNW TLD 49-1 East Lyme - Society Rd. 3.6 Mi, NW TLD 50-1 East Lyme- Manwaring/Terrace 2.1 Mi,W TLD 51-1 East Lyme - Smith Ave. 1.5 Mi, NW TLD 52-1 Waterford - River Rd. 1.1 Mi, NNW TLD 53-1 Waterford - Gardiners Wood Rd 1.4 Mi, NNE TLD 55-1 Waterford - Magonk Point 1.8 Mi, ESE TLD 56-1 New London - Ocean&Mott Ave. 3.7 Mi, E TLD 57-1 New London - Ocean Ave. 3.6 Mi, ENE TLD 59-1 Waterford -Miner Ave. 3.4 Mi, NNE TLD 60-1 Waterford-Parkway South&Cross 4.0 Mi, N TLD 61-1 Waterford-Oil Mill&Boston Post 4.3 Mi, NNW TLD 2-2

Dominion Nuclear Conn ecticut, Inc. Ann ual Radiological Environm ental Operating Report 2017 Millstone Power Station Table 2-1 Environmental Monjtorjng Program sampling Types and Locations <Continues)

No.- Distance, Direction Location Name Sample Media Typ From Release Point2 62-1 East Lyme - Columbus Ave. 1.9 Mi , WNW TLD 63-1 Waterford - Gardiners Wood & 0.8 Mi , NE TLD Jordon Cove 64-1 Waterford - Shore Rd. 1.1 Mi , ENE TLD 65-1 Waterford - Boston Post Rd . 3.2 Mi , NE TLD 66-X NAP Parking Lot - Fit Center 0.4 Mi , NW TLD 71-1 1-MW-XFMR-03 Onsite Well Water 72-1 MW-GPl-1 Onsite Well Water 73-X Site Switchyard Fence 0.3 Mi, N TLD 74-X Ball Field Foul Pole 0.6 Mi , N TLD 75-X Waterford - W indward Way & Shotgun 0.5 Mi , NE TLD 76-X ISFSl-1 Up-gradient of ISFSI Well Water 77-X ISFSl-2 Down-gradient of ISFSI Well Water 78-X ISFSl-3 Down-grad ient of ISFSI Well Water 79-1 M3-MW-1 Onsite Well Water 81-1 S2-MW-1 Onsite Well Water 82-1 MW-6B Onsite Well Water 89-C Aquatic background >4 Mi of discharge Lobster 90-X Thames River 4M i, E Fucus

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 :

Key: I - Indicator C - Control X - Extra - sample not required by the REMODCM

I = Indicator; C = Control.

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

2-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station Table 2-2 Required sampljng frequency & Type of Analysis Exposure Pathway No. of Sampling & Collection Frequency Type of Analysis and/or Sample Locations 1

1. Gamma Dose - 39 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 station 's gross beta results

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

4. Vegetation 5 One sample near middle and one Gamma Isotopic on each 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 Gammalsotopic and Tritium on each sample

8. Bottom Sediment 5 Semiannual Gamma Isotopic on each sample

9. Soil 3 Annually Gamma Isotopic on each sample

10. Fin Fish (edible 2 Quarterly Semiannual beginning 4th Gamma Isotopic on each sample quarter portion) 11 . Aquatic flora (fucus) 4 Quarterly beginning 4th quarter Gamma isotopic on each sample

13. Clams 2 Quarterly Semiannual beginning 4th Gamma Isotopic on each sample (edible portion) quarter

14. Lobster 2 Quarterly Semiannual beginning 4th Gamma Isotopic on each sample (edible portion) quarter Footnotes

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

Oysters were previously 12. REMODCM revision 27.

2-4

Dominion Nucl ear Connecticut, Inc. Annua l Radiolog ical Environmental Operating Report 2017 Millstone Power Station Figure 2.1, "Inner TLD, Air, Grass, Soil, and Aquatic Locations" 2-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station Figure 2.2, "Outer TLD and Aquatic Locations" 2-6

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 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 2017:

Number of Number of Technical Technical Number of Extra Sample Type Specification Specification Samples Analyzed Required Samples Required Samples Analyzed Gamma Exposure 156 155 16 (Environmental TLD)

Air Particulates 208 208 0 Air Iodine 208 208 0 Soi l 3 3 0 Milk (cow) 0 0 8 Milk (goat) 0 0 8 Well Water 12 12 24 Fruits & Vegetables 4 4 0 Broad leaf vegetation 8 8 0 Sea Water 16 16 0 Bottom Sediment 10 10 11 Aquatic Flora 4 4 12 Fish 4 4 0 Oysters 0 0 4 Clams 4 4 0 Lobster 4 4 0 Total All Types 641 640 83 2.3 Required Samples Not Collected During the Report Period During 2017 there was one required sample deviation from the sampling schedule. The fourth quarter Quarry Discharge TLD was lost during construction activities on the discharge quarry. This issue has been corrected in the first quarter of 2018.

The air sample volume collected on November 14, 2017 for particulates (Table 2) and iodine (Table 3) was half the normal volume because of a loss of power at the sampler and sample pump failures for that two week sample period. The volume collected was still sufficient to attain the required minimum analyses sensitivities for the samples.

2-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 20 17 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.

3-1

Dominion Nuclear Con necticut, Inc. Annual Radiological Environmenta l Operati ng Report 2017 Mi llston e Pow er Station RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2017 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled Analysis Total LLD* Number Number (Units) Type Number Mean Location Distance Number Mean (Range) Number Direction Mean(Range) (Range)

Direct Gam ma 171 NA 155 02 0.3Mi. 4 16 Rad iation Dose 7.7 s 11 7.9 TLD(uR/hr) (4.6-11 .6) (10.4-11.4) (5.9-9.4)

Air Iodine 1-131 208 0 .07 182 NA NA <LLD 26 3 <LLD

( pCi/m ) <LLD Air Particulate GR-B 208 0.01 182 15 14.0 Mi. 26 26 (pCi!m 3 ) 0.0124 N 0.0130 0.0130 (0.0045/0.0199) (0.0054/0.0199) (0.0054/0.0199)

GAMMA 32 BE-7 NA 28 02 0.3Mi. 4 4 0.119 s 0.135 0.108 (0 .084-0.176) (0.115-0.165) (0.069-0 .137)

Other Note2 <LLD NA NA <LLD <LLD Gammas Soll GAMMA 3 (pCil gdry) K-40 NA 2 14C 12 Mi.

14.74 NE 16.89 16.89 (13.59-15.88) (<LLD-16.89) (<LLD-16.89)

CS-137 0.18 2 4 1.0Mi. 2 0.26 N 0.32 <LLD

(.20-.32) (<LLD-0.32)

Other Note3 <LLD NA NA <LLD <LLD Gammas Cow MIik SR-89 3 10 3 NA NA <LLD NA (pCi/1) <LLD SR-90 3 2 3 NA NA <LLD NA

<LLD GAMMA 8 K-40 NA 8 22 10.5Mi. 8 NA 1326 WNW 1326

( 1155/1457) (1155/1457)

Other Note4 <LLD NA NA <LLD <LLD Gammas 3-2

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2017 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled Analysis Total LLD*

Number Number (Units) Type Number Location Distance Number Mean Mean (Range) Number Direction Mean(Range) (Range)

Goat Milk SR-89 3 10 3 NA NA <LLD NA (pCi/1) <LLD SR-90 3 2 3 NA NA <LLD NA

<LLD GAMMA 8 K-40 NA 8 23 11 .9Mi. 8 NA 1608 NNW 1608 (1337/1934) (1337/1934)

Other Note4 <LLD NA NA <LLD <LLD Gammas WellWater H-3 36 2000 36 NA NA <LLD NA (pCi/1) <LLD GAMMA 36 K-40 NA 36 NA NA <LLD NA

<LLD Other Notes <LLD NA NA <LLD NA Gammas Fruits & Vegetables GAMMA 8 (pCi/gwet) K-40 NA 4 26 > 10 Milles 4 4 1.080 1.167 1.167 (0.483-1.401) (0.543-2 .036) (0.543-2.036)

Other Note6 <LLD NA NA <LLD <LLD Gammas Broad Leaf Vegetation GAMMA 8 (pCi/gwet) BE-7 NA 5/6 0.6Mi. 1/2 2 1.337 NNW 1.906 1.205 (0.859-1.906) (<LLD-1 .906) (0.955-1.454)

K-40 NA 6 0.6Mi. 2 2 3.908 NNW 4.536 4.894 (3.418-4 .850) (4.221-4.850) (4.217-5.570)

Ac-228 NA 1/6 10 1.2Mi. 1/6 2 0.130 E 0.130 <LLD

(<LLD-0.130) (<LLD-0 .130)

Other Note7 <LLD NA NA <LLD <LLD Gammas 3-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2017 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampled Analysis Total LLD*

Number Number (Units) Type Number Location Distance Number Mean Mean (Range) Number Direction Mean(Range) (Range)

Sea Water H-3 16 3000 7/12 32 <0.1 Mi 7/1 2 4 (pCi/lj 808 808 <LLD (346/ 1990) (346/ 1990)

GAMMA 16 K-40 NA 11 /12 32 <0.1 Mi 11 / 12 4 295 295 264 (227/403) (227/403) (217/346)

Other Note5 <LLD NA NA <LLD <LLD Gammas Bottom Sediment GAMMA K-40 10 (pCilgdry) NA 8 32 <0 .1 Mi 2 2 18.39 19.52 14.92 (16.06-22 .76) (16.27-22 .76) (14.77-15.07)

Other Note3 <LLD NA NA <LLD <LLD Gammas Flora GAMMA BE-7 20 (pCi/gwet) NA 3/20 90 4 .0Mi. 1/2 NA 0.351 E 0 .513 (0 .206-0 .513) (<LLD-0 .513)

K-40 NA 20 32 < 0.1 Mi 4 NA 6 .678 7.674 (4.567-1 .925) (6.732-9.125) 1-131 0.06 1/20 90 4 .0Mi. 1/20 NA 0.044 E 0.044

(<LLD-0.044) (<LLD-0 .044)

Ac-228 NA 3/20 29 0.4Mi. 1/4 NA 0 .138 NNE 0.194 (0.091 -0.192) (<LLD-0 .192)

Other Note6 <LLD NA NA <LLD NA Gammas 3-4

Domini on Nuclear Connecticut, Inc. Annual Radi ol ogical Environmental Operating Rep ort 2017 M illston e Power Sta t ion RADIOLOCIAL ENVIRONMENT MONITORING PROGRAM

SUMMARY

MILLSTONE POWER STATION Dockets 50-245, 50-336 & 50-423 2017 Medium or Indicator Control Pathway Locations Location with Highest Mean Locations Sampl ed Analysis Total LLD* Number Number (Units) Type Number Location Distance Number Mean Mean (Range) Number Direction Mean(Range) (Range)

Fish

Other GAMMA 4 (pCi/gwet) K-40 NA 4 32 <0.1 Mi 2 NA 3.150 3.193 (3.037-3.196) (3.189-3.196)

Other Note9 <LLD NA NA <LLD NA Gammas Oysters GAMMA 4 (pCi/gwet) K-40 NA 4 89 >4.0Mi. 2 NA 2.256 of Discharge 2.702 (1 .617-3.098) (2.305-3.098)

Other Note9 <LLD NA NA <LLD NA Gammas Clams GAMMA 4 (pCilgwet) K-40 NA 4 29 0.4Mi. 2 NA 2.058 ENE-ESE 2.356 (1 .558-2.643) (2. 068-2.643)

Other Note9 <LLD NA NA <LLD NA Gammas Lobster GAMMA 4 (pCilgwet) K-40 NA 2 35 <0 .5Mi. 2 2 3.007 SSW-W 3.007 2.401 (2.027-3.987) (2.027-3.987) (2.306-2.496)

Other Note9 <LLD NA NA <LLD NA Gammas 3-5

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Op erating Report 2017 Millstone Power Station NOTES FOR

SUMMARY

TABLE 1 - The required LLD . LLD is the smallest concentration of radioactivity that will be detected with 95%

confidence that the activity is real. See detailed discussion below.

3 3 2 - LLDs for air particulate gamma are 0.05 pCi/M for Cs-134 and 0.06 pCi/M 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/1 for 1-131 , 15 pCi/1 for Cs-134 , 18 pCi/1 for Cs-137, 70 pCi/1 for Ba-140 and 25 pCi/1 for La-140.

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

3 6 - LLDs for fruits & vegetables , broadleaf vegetation and aquatic flora for gamma are 0.06 pCi/M for 3 3 1-131, 0.06 pCi/M for Cs-134 and 0.08 pCi/M for Cs-137.

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

8 - Aquatic flora locations were extra, non-required samples for the first three quarters of 2017. For the fourth quarter aquatic flora added as a requirement to the REMODCM with Locations 29 , 32 and 35 treated as indicators and Location 36 as a control. Location 90 is an extra , non-required location which is downstream from the New London water treatment plant. Although it is not influenced by any MPS releases , at times it will detect radioactivity released from the water treatment plant.

9 - 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 radioc hemical separation):

4.66 S b LLD = - - - - - - - -

E

V

2.22

Y

exp (-A,0.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 volum e) 2 .22 is the number of transformation per minute per picoCurie Y is the fractional radiochemical yield (when applicable)

A is the radioactive decay constant for the particular radionuclide t.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.

(continue on next page)

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 2017 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 balded type. Results are considered positive when the measured value exceeds 1.5 times the listed 2cr error (i .e., the measured value exceeds 3cr) . The reported error is two times the standard deviation (2cr) of the net activity. Unless otherwise noted , the overall error (counting ,

sample size, chem istry, errors , etc.) is estimated to be 2 to 5 times that listed . Because of counting statistics , negative values, zeros and numbers below the Minimum Detectable Level (MDL) are statistically valid pieces of data . For the purposes of this report , in order to indicate any background biases , all the valid data are presented . This practice was recommended by Health and Safety Laboratory (HASL) ("Reporting of Analytical Results from HASL," letter by Leo B. Higginbotham) ,

NUREG 0475 and NUREG/CR-4007 (Sept. 1984).

Data are given according to sample type as indicated below.

1. Gamma Exposure Rate

2. Air Particulates, Gross Beta Radioactivity

3. Air Particulates , Airborne 1-131

4. Air Particulates , Gamma Spectra

5. Soi l

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 2017 M illstone Power Station TABLE 1 QUARTERLY GAMMA EXPOSURE RATE

(µR/hr)*

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

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

1Q 7.6 0.5 10.4 0.5 7.0 0.3 7.2 0.7 9.1 0.9 8.4 0.5 5.4 0.3 10.4 0.5 9.9 0.4 8.4 0.4 6.3 0.5 2Q 8.0 0.5 11.1 0.8 7.2 0.4 7.3 0.4 9.2 0.6 8.7 0.5 4.6 0.6 10.7 0.6 11 .0 0.7 8.8 0.9 6.9 0.4 3Q 8.2 0.6 11.4 0.7 7.6 0.6 7.5 0.6 9.7 0.6 8.4 0.6 4.6 0.5 11.0 1.0 11.4 0.8 8.8 1.3 7.2 0.8 4Q 8.5 0.7 11.3 1.2 7.7 0.7 8.1 0.6 9.7 1.2 (a) 5.0 0.4 11.6 1.2 11 .2 1.0 9.2 0.7 7.3 0.6 PERIOD 13C 14C 15C 16C 27 41 42 43 44 45 46

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

1Q 8.7 0.4 8.8 0.4 7.3 0.4 5.9 0.4 7.1 0.4 6.4 0.4 7.3 0.6 7.1 0.6 6.9 0.7 6.8 0.3 7.8 0.7 2Q 8.2 0.5 9.1 0.8 7.6 0.5 5.9 0.6 7.6 0.6 6.5 0.7 7.3 0.4 7.2 0.5 7.7 0.6 7.0 0.4 8.3 0.5 3Q 9.0 0.9 9.4 0.6 8.0 0.6 6.3 0.5 7.5 0.5 6.8 0.7 7.5 0.6 7.2 0.4 8.2 0.6 7.2 1.0 8.5 0.7 4Q 9.1 0.9 9.2 1.0 7.8 1.0 6.1 0.5 7.6 0.7 6.7 0.6 7.7 0.7 7.7 0.7 8.2 0.6 7.2 0.8 8.6 0.8 PERIOD 47 48 49 50 51 52 53 55 56 57 59

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

1Q 7.6 0.5 8.8 0.5 6.3 0.4 7.0 0.3 6.2 0.4 6.8 0.4 6.8 0.7 7.1 0.3 6.8 0.5 6.9 0.6 7.3 0.5 2Q 7.6 0.8 9.0 0.6 6.4 0.3 7.8 0.6 6.3 0.5 6.7 0.5 7.2 0.6 7.4 0.4 6.8 0.6 7.2 0.4 7.7 0.5 3Q 7.9 1.0 9.7 0.9 7.1 0.6 7.6 0.9 6.5 0.5 6.8 0.6 7.3 0.7 7.5 0.6 7.4 0.6 7.3 0.5 8.1 0.6 4Q 7.8 0.6 9.4 0.7 6.6 0.5 7.9 1.0 6.4 0.8 7.3 0.7 7.4 0.6 7.6 0.7 7.1 0.8 7.4 0.7 8.1 0.9 PERIOD 60 61 62 63 64 65 66 73 74 75

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

1Q 6.2 0.3 6.3 0.4 7.3 0.3 7.8 0.7 7.1 0.3 7.3 0.6 6.8 0.4 7.6 0.4 7.3 0.4 6.2 0.5 2Q 6.4 0.4 6.4 0.5 7.9 0.6 8.3 0.9 7.1 0.5 7.7 0.6 7.3 0.7 8.2 0.5 7.2 0.5 6.6 0.4 3Q 6.8 0.6 6.5 0.4 8.1 0.9 8.4 0.6 7.7 0.5 7.8 0.5 7.7 0.5 8.1 0.8 7.6 0.6 6.9 0.4 4Q 6.5 0.6 6.4 0.6 8.5 0.7 9.0 0.7 7.4 0.6 7.5 0.6 7.7 0.7 7.5 0.6 7.9 0.8 6.7 0.5

READINGS ARE THE AVERAGE OF MULTl Caso. TM PHOSPHOR ELEMENTS WITHIN ON E PANASONIC TLD BADGE ERRORS ARE TWO SIGMA AND INCLUDE COUNTING , TRANSIT, READER AND FADE UNCERTAINTIES C = Control location, Background location (a) Lost TLD 3-8

Dominion Nuclear Connecticut, Inc. Annual Radiol ogical Environmental Operating Report 2017 Millstone Power Statio n TABLE 2 AIR PARTICULATES GROSS BET A RADIOACTIVITY 3

(pCi/m )

LOCATIONS PERIOD ENDING 01 02 03 04 10 11 27 15C

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

01 /10/17 0.010 0.002 0.011 0.002 0.010 0.002 0.010 0.002 0.011 0.002 0.010 0.002 0.010 0.002 0.012 0.002 01 /24/17 0.012 0.002 0.013 0.002 0.013 0.002 0.014 0.002 0.014 0.002 0.013 0.002 0.013 0.002 0.012 0.002 02/07/17 0.011 0.002 0.011 0.002 0.013 0.002 0.012 0.002 0.011 0.002 0.011 0.002 0.011 0.002 0.011 0.002 02/21 /17 0.013 0.002 0.013 0.002 0.014 0.002 0.013 0.002 0.013 0.002 0.012 0.002 0.013 0.002 0.013 0.002 03/07/17 0.014 0.002 0.014 0.002 0.015 0.002 0.016 0.002 0.014 0.002 0.015 0.002 0.015 0.002 0.016 0.002 03/21 /17 0.014 0.002 0.013 0.002 0.013 0.002 0.013 0.002 0.014 0.002 0.012 0.002 0.012 0.002 0.013 0.002 04/04/17 0.010 0.002 0.009 0.002 0.010 0.002 0.010 0.002 0.016 0.002 0.010 0.002 0.010 0.002 0.013 0.002 04/18/17 0.010 0.002 0.011 0.002 0.011 0.002 0.009 0.002 0.011 0.002 0.010 0.002 0.010 0.002 0.011 0.002 05/02/17 0.005 0.001 0.007 0.002 0.008 0.002 0.005 0.001 0.008 0.002 0.007 0.002 0.008 0.002 0.007 0.002 05/16/17 0.006 0.002 0.005 0.001 0.007 0.002 0.006 0.001 0.006 0.001 0.006 0.002 0.005 0.001 0.005 0.002 05/30/17 0.008 0.002 0.010 0.002 0.008 0.002 0.008 0.002 0.008 0.002 0.008 0.002 0.009 0.002 0.008 0.002 06/13/17 0.008 0.002 0.008 0.002 0.009 0.002 0.009 0.002 0.010 0.002 0.010 0.002 0.007 0.001 0.008 0.002 06/27/17 0.015 0.002 0.011 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 07/11 /17 0.013 0.002 0.012 0.002 0.011 0.002 0.012 0.002 0.012 0.002 0.012 0.002 0.012 0.002 0.012 0.002 07/25/17 0.013 0.002 0.012 0.002 0.015 0.002 0.014 0.002 0.014 0.002 0.0 16 0.002 0.014 0.002 0.016 0.002 08/08/17 0.010 0.002 0.007 0.002 0.011 0.002 0.011 0.002 0.010 0.002 0.011 0.002 0.010 0.002 0.011 0.002 08/22/17 0.018 0.002 0.017 0.002 0.017 0.002 0.017 0.002 0.015 0.002 0.017 0.002 0.018 0.002 0.017 0.002 09/05/17 0.013 0.002 0.014 0.002 0.012 0.002 0.015 0.002 0.014 0.002 0.015 0.002 0.013 0.002 0.014 0.002 09/18/17 0.016 0.002 0.014 0.002 0.015 0.002 0.016 0.002 0.014 0.002 0.015 0.002 0.016 0.002 0.015 0.002 10/03/17 0.013 0.002 0.010 0.002 0.014 0.002 0.013 0.002 0.012 0.002 0.013 0.002 0.013 0.002 0.013 0.002 10/17/17 0.012 0.002 0.013 0.002 0.011 0.002 0.014 0.002 0.012 0.002 0.013 0.002 0.012 0.002 0.014 0.002 10/31 /17 0.016 0.002 0.018 0.002 0.018 0.002 0.016 0.002 0.019 0.002 0.020 0.003 0.018 0.002 0.018 0.002 11 /14/17 0.015 0.002 0.015 0.002 0.015 0.002 0.016 0.002 0.016 0.002 0.015 0.002 0.013 0.002 0.020 0.003 11 /28/17 0.013 0.002 0.014 0.002 0.014 0.002 0.013 0.002 0.014 0.002 0.016 0.002 0.014 0.002 0.016 0.002 12/12/17 0.016 0.002 0.015 0.002 0.017 0.002 0.018 0.002 0.018 0.002 0.015 0.002 0.014 0.002 0.019 0.002 12/26/17 0.013 0.002 0.013 0.002 0.013 0.002 0.013 0.002 0.011 0.002 0.011 0.002 0.014 0.002 0.011 0.002 C= Control Location , Background Location 3-9

Domini on Nucl ear Connecticut, Inc. Annual Radi ological Environmental Operating Report 2017 Millstone Power Station TABLE 3 AIRBORNE IODINE (pCi/m 3)

LOCATIONS PERIOD ENDING 01 02 03 04 10 11 27 15C

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

01 /10/17 0.026 0.026 0.026 0.028 0.022 0.022 0.023 0.019 0.023 01 /24/17 0.000 0.013 0.012 0.013 0.011 0.020 0.021 0.019 0.020 02/07/17 0.014 0.013 0.013 0.014 0.012 0.012 0.013 0.011 0.012 02/21 /17 0.001 0.020 0.021 0.021 0.019 0.027 0.024 0.025 0.025 03/07/17 0.021 0.022 0.022 0.023 0.008 0.024 0.022 0.023 0.023 03/21 /17 0.010 0.020 0.021 0.022 0.020 0.019 0.017 0.018 0.018 04/04/17 -0.005 0.015 0.015 0.015 0.014 0.015 0.013 0.014 0.014 04/18/17 -0.006 0.016 0.016 0.016 0.015 0.016 0.015 0.016 0.016 05/02/17 -0.004 0.020 0.021 0.020 0.018 0.015 0.015 0.016 0.016 05/16/17 0.006 0.016 0.016 0.016 0.015 0.012 0.013 0.013 0.014 05/30/17 0.006 0.019 0.019 0.021 0.019 0.016 0.017 0.015 0.017 06/13/17 0.000 0.016 0.016 0.018 0.016 0.012 0.013 0.012 0.013 06/27/17 0.002 0.017 0.017 0.019 0.017 0.018 0.020 0.018 0.020 07/11 /17 0.004 0.020 0.021 0.022 0.020 0.016 0.017 0.015 0.017 07/25/17 0.0 15 0.016 0.016 0.017 0.015 0.015 0.016 0.015 0.017 08/08/17 0.001 0.029 0.029 0.031 0.027 0.020 0.022 0.020 0.022 08/22/17 0.032 0.030 0.030 0.032 0.029 0.018 0.019 0.018 0.020 09/05/17 0.001 0.019 0.019 0.020 0.018 0.014 0.015 0.011 0.015 09/18/17 0.012 0.021 0.021 0.018 0.020 0.018 0.019 0.018 0.020 10/03/17 0.007 0.025 0.025 0.022 0.023 0.019 0.020 0.018 0.020 10/17/17 0.002 0.015 0.015 0.013 0.014 0.018 0.018 0.017 0.018 10/31 /17 0.001 0.017 0.017 0.014 0.016 0.019 0.020 0.016 0.018 11 /14/17 -0 .011 0.024 0.024 0.020 0.022 0.022 0.024 0.021 0.041 11 /28/17 -0.015 0.018 0.018 0.015 0.017 0.009 0.010 0.009 0.009 12/12/17 0.002 0.015 0.015 0.012 0.014 0.015 0.016 0.015 0.015 12/26/17 0.008 0.022 0.021 0.010 0.020 0.019 0.020 0.019 0.019 C= Control Location, Background Location 3-10

Dom inion Nuclear Conne ctic ut, Inc. Annual Radiologica l Environm enta l Op erating Repo rt 2017 M ill stone Power Station TABLE 4 AIR PARTICULATES 3

(pCi/m )

GAMMA SPECTRA* QTR 1 (12/27/16 - 04/04/17)

LOCATION Be-7 Mn-54 Co-58 Co-60 Zn-65 Nb-95 Zr-95

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

01 0.1519 0.0351 0.0008 0.0014 -0.0005 0.0023 -0.0004 0.0012 -0.0003 0.0028 0.0006 0.0020 -0.0017 0.0034 02 0.1147 0.0263 0.0008 0.0013 -0 .0007 0.0020 0.0000 0.0011 0.0004 0.0033 0.0009 0.0023 0.0002 0.0042 03 0.1023 0.0296 -0.0004 0.0010 -0.0022 0.0016 0.0004 0.0013 0.0017 0.0024 -0 .0003 0.0018 0.0004 0.0036 04 0.1340 0.0298 -0.0001 0.0012 0.0005 0.0019 0.0001 0.0011 -0.0010 0.0029 0.0008 0.0020 0.0004 0.0038 10 0.1762 0.0381 0.0007 0.0015 0.0009 0.0020 -0.0003 0.0016 0.0012 0.0027 -0.0028 0.0025 0.0037 0.0037 11 0.1179 0.0259 0.0005 0.0011 0.0006 0.0016 0.0003 0.0010 -0.0006 0.0025 0.0016 0.0020 -0.0017 0.0035 27 0.1048 0.0302 -0.0002 0.0011 0.0013 0.0020 0.0007 0.0013 -0.0009 0.0028 -0 .0005 0.0022 0.0009 0.0032 15C 0.1214 0.0444 0.0000 0.0017 0.0029 0.0026 0.0006 0.0016 -0.0008 0.0043 0.0002 0.0030 -0.0011 0.0052 LOCATION Ru -103 Ru -106 Cs-134 Cs-137 Ba-140 Ce-141 Ce-144

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

01 0.0003 0.0031 0.0073 0.0112 -0 .0007 0.0015 -0.0005 0.0012 0.0749 0.1 275 0.0000 0.0045 -0.0020 0.0058 02 -0.0289 0.0053 -0.0094 0.0126 0.0005 0.0014 0.0003 0.0012 0.0038 0.1178 0.001 2 0.0063 0.0048 0.0083 03 -0.0004 0.0027 -0.0110 0.0104 0.0010 0.0014 -0.0007 0.0010 0.0401 0.0870 -0.0008 0.0036 -0.0038 0.0048 04 -0.0264 0.0049 -0.0037 0.0117 0.0008 0.0012 0.0005 0.0012 -0.0156 0.1053 0.0030 0.0058 -0.0009 0.0076 10 0.0007 0.0032 -0.0065 0.0116 0.0002 0.0013 -0.0010 0.0011 -0.0683 0.1 198 -0 .0029 0.0049 0.0063 0.0059 11 0.0002 0.0025 0.0009 0.0103 0.0006 0.0011 0.0012 0.0010 0.0187 0.0946 0.0007 0.0036 0.0002 0.0050 27 0.0021 0.0026 0.0048 0.0107 -0.0002 0.0012 0.0004 0.0011 0.0708 0.0866 -0.0025 0.0040 -0.0020 0.0053 15C -0.0010 0.0039 0.0160 0.0147 -0.0003 0.0016 0.0004 0.0016 0.0195 0.1504 -0.0033 0.0061 0.0025 0.0083 C= Control location, Background location Res ults in bold type are positive.

3- 11

Dom inion Nuclea r Co nnect icut, Inc. Annual Radiol ogical Environmenta l Ope rating Repo rt 20 17 M illstone Powe r Station TABLE 4 AIR PARTICULATES 3

(pCi/m )

GAMMA SPECTRA - QTR 2 (04/04/17 - 06/27/17)

LOCATION Be-7 Mn-54 Co-58 Co-60 Zn-65 Nb-95 Zr-95

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

01 0.1277 0.0316 0.0000 0.0020 -0.0002 0.0028 0.0025 0.0018 0.0009 0.0052 0.0004 0.0028 -0.0013 0.0052 02 0.1646 0.0369 0.0001 0.0018 0.0003 0.0026 -0 .0006 0.0015 0.0003 0.0043 0.0005 0.0026 0.0031 0.0051 03 0.1215 0.0349 -0.0007 0.0016 -0.0001 0.0024 0.0006 0.0015 0.0014 0.0038 0.0012 0.0022 -0.0038 0.0041 04 0.1010 0.0235 0.0000 0.0010 0.0004 0.0016 0.0001 0.0008 0.0019 0.0026 -0 .0004 0.0017 0.0002 0.0027 10 0.1123 0.0361 0.0001 0.0013 -0.0011 0.0023 0.0004 0.0011 0.0000 0.0030 0.0005 0.0020 0.0022 0.0037 11 0.0946 0.0354 -0.0008 0.0014 0.0000 0.0021 0.0004 0.0011 0.0007 0.0035 -0 .0008 0.0022 -0 .0009 0.0038 27 0.1165 0.0316 0.0008 0.0015 0.0000 0.0020 -0.0009 0.0011 0.0024 0.0031 0.0010 0.0018 0.0012 0.0029 15C 0.1374 0.0515 0.0006 0.0023 0.0012 0.0028 0.0016 0.0020 0.0014 0.0050 -0 .0014 0.0039 0.0014 0.0060 LOCATION Ru-103 Ru-106 Cs-134 Cs-137 Ba-140 Ce-141 Ce-144

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

01 0.0016 0.0045 0.0035 0.0170 -0.0015 0.0021 0.0002 0.0017 -0.1520 0.1 522 -0.0006 0.0062 -0.0044 0.0090 02 0.0018 0.0033 -0.0013 0.0158 -0.0009 0.0016 -0 .0005 0.0015 0.0738 0.1395 0.0018 0.0049 -0.0022 0.0065 03 -0.0274 0.0057 -0.0045 0.0149 -0.0006 0.0017 0.0010 0.0014 -0.0551 0.1346 0.0019 0.0066 0.0021 0.0088 04 0.0027 0.0025 0.0003 0.0096 -0.0009 0.0010 -0.0001 0.0009 0.0237 0.0775 -0 .0002 0.0036 -0.0028 0.0053 10 -0 .0010 0.0025 -0.0005 0.0106 -0 .0011 0.0013 0.0010 0.0011 0.0402 0.0943 -0.0010 0.0040 -0.0021 0.0049 11 0.0005 0.0028 -0.0091 0.0119 -0.0008 0.0012 0.0005 0.0011 -0.0868 0.0973 0.0043 0.0044 -0.0001 0.0061 27 0.0003 0.0028 -0.0063 0.0104 -0.0009 0.0013 0.0007 0.0010 0.0334 0.0700 -0.0007 0.0038 -0.0040 0.0051 15C 0.0029 0.0044 -0.0135 0.0168 -0 .0012 0.0022 0.0002 0.0018 0.0555 0.1414 -0.0078 0.0058 -0 .0056 0.0077 C= Control location, Background location Results in bold type are positive.

3- 12

Dom inion Nuclear Conn ecti cut, Inc. An nual Radiol ogi ca l Envi ro nme nt al Operating Re po rt 2017 Mi llstone Power Station TABLE 4 AIR PARTICULATES (pCi/m 3)

GAMMA SPECTRA - QTR 3 (06/27/17 -10/03/17)

LOCATION Be-7 Mn-54 Co-58 Co-60 Zn-65 Nb-95 Zr-95

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

01 0.1192 0.0352 -0.0011 0.0019 0.0037 0.0032 -0 .0005 0.0019 0.0004 0.0047 -0 .0006 0.0036 -0.0055 0.0070 02 0.1337 0.0304 0.0000 0.0010 -0.0009 0.0018 0.0006 0.0011 -0.0002 0.0032 -0 .0013 0.0019 -0.0013 0.0034 03 0.1055 0.0472 0.0001 0.0014 0.0004 0.0021 -0 .0009 0.0010 -0.0016 0.0029 0.0010 0.0026 0.0043 0.0051 04 0.1399 0.0347 0.0013 0.0018 0.0026 0.0031 0.0013 0.0014 -0.0005 0.0043 0.0000 0.0030 0.0006 0.0054 10 0.0899 0.0335 0.0004 0.0011 0.0005 0.0019 0.0004 0.0009 0.0006 0.0025 -0.0005 0.0020 0.0005 0.0031 11 0.1138 0.0350 0.0004 0.0015 -0.0003 0.0023 0.0007 0.0012 -0.0016 0.0031 -0.0010 0.0022 0.0016 0.0048 27 0.1497 0.0313 -0.0004 0.0009 0.0005 0.0016 -0.0007 0.0011 0.0030 0.0027 0.0004 0.0018 -0.0017 0.0032 15C 0.1047 0.0281 -0.0011 0.0012 -0.0012 0.0017 0.0000 0.0010 0.0008 0.0024 0.0002 0.0016 -0.0007 0.0029 LOCATION Ru-103 Ru-106 Cs-134 Cs-137 Ba-140 Ce-141 Ce-1 44

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

01 -0.0019 0.0056 -0.0002 0.0189 -0.0005 0.0021 0.0009 0.0018 0.1572 0.3029 -0.0011 0.0066 0.001 1 0.0071 02 0.0001 0.0028 0.0021 0.0086 0.0002 0.0012 0.0001 0.0010 -0.0763 0.1647 -0.0037 0.0046 -0.0016 0.0056 03 0.0027 0.0038 0.0043 0.0101 -0.0005 0.0012 0.0014 0.0011 0.1422 0.1835 -0.0007 0.0059 -0 .0012 0.0055 04 -0.0010 0.0056 -0.0032 0.0167 -0.0013 0.0017 -0.0007 0.0015 -0.0360 0.3291 0.0004 0.0084 -0.0065 0.0085 10 -0.0007 0.0034 0.0040 0.0095 0.0006 0.0012 0.0006 0.0008 0.0978 0.1809 -0.0025 0.0048 0.0013 0.0050 11 0.0005 0.0040 0.0165 0.0123 -0 .0006 0.0014 0.0017 0.0013 0.0141 0.2212 0.0023 0.0060 0.0027 0.0058 27 -0.0016 0.0028 -0.0031 0.0080 -0.0005 0.0011 0.0004 0.0009 0.1149 0.1835 -0 .0013 0.0044 -0.0001 0.0044 15C -0.0005 0.0027 -0.0019 0.0079 -0.0001 0.0009 0.0001 0.0008 -0.0635 0.1538 -0.0001 0.0043 -0 .0026 0.0046 C= Control location, Background location Results in bold type are positive.

3-13

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Powe r Stati on TABLE 4 AIR PARTICULATES (pCitm 3)

GAMMA SPECTRA- QTR 4 (10/03/17 -12/26/17)

LOCATION Be-7 Mn-54 Co-58 Co-60 Zn-65 Nb-95 Zr-95

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

01 0.0974 0.0485 0.0008 0.0019 0.0011 0.0037 -0.0009 0.0024 0.0005 0.0048 -0.0024 0.0042 0.0081 0.0082 02 0. 1251 0.0383 0.0012 0.0012 -0.0023 0.0020 0.0012 0.0013 0.0017 0.0034 0.0007 0.0025 0.0011 0.0039 03 0.0849 0.0332 -0.0003 0.0014 -0.0012 0.0020 0.0001 0.0011 -0.0008 0.0028 0.0010 0.0022 -0.0008 0.0034 04 0.1 254 0.0332 0.0003 0.0021 -0.0006 0.0033 0.0018 0.0021 0.0029 0.0048 0.0012 0.0036 -0.0054 0.0065 10 0.1 011 0.0294 0.0002 0.0012 -0.0002 0.0022 -0.0006 0.0014 0.0020 0.0030 0.0024 0.0025 -0.0037 0.0041 11 0.0843 0.0296 0.0013 0.0016 -0.0013 0.0022 0.0002 0.0013 -0.0006 0.0030 -0.0007 0.0029 0.0009 0.0049 27 0.1129 0.0297 -0.0005 0.0014 -0.0001 0.0018 -0 .0010 0.0014 -0 .0010 0.0037 0.0005 0.0022 0.0001 0.0038 15C 0.0692 0.0267 -0.0002 0.0012 -0 .0019 0.0019 0.0002 0.0013 0.0020 0.0023 -0 .0001 0.0017 -0.0017 0.0025 LOCATION Ru-103 Ru-106 Cs-134 Cs-1 37 Ba-1 40 Ce-141 Ce-144

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

01 0.0048 0.0057 -0.0273 0.0211 -0.0025 0.0029 0.0001 0.0018 -0.0734 0.2663 0.0044 0.0076 0.0038 0.0080 02 -0.0011 0.0031 -0.0008 0.0111 -0.0006 0.0011 -0.0001 0.0012 0.0991 0.1259 0.0004 0.0053 -0.0020 0.0058 03 -0.0020 0.0031 -0.0035 0.0118 -0.0003 0.0013 -0.0010 0.0011 -0.0688 0.1871 -0.0014 0.0048 -0.0031 0.0055 04 -0.0045 0.0069 0.0055 0.0190 -0 .0016 0.0021 0.0010 0.0018 -0.0965 0.2385 0.0012 0.0089 -0.0030 0.0112 10 0.0009 0.0032 0.0034 0.0120 -0 .0012 0.0015 -0 .0006 0.0012 0.0284 0.1533 0.0006 0.0050 -0.0039 0.0059 11 -0.0183 0.0052 -0.0173 0.0150 -0.0012 0.0015 -0.0012 0.0014 -0.0285 0.1770 0.0018 0.0081 -0.0018 0.0097 27 0.0017 0.0037 0.0030 0.0116 0.0003 0.0013 0.0007 0.0012 -0.0859 0.1533 0.0035 0.0053 -0 .0021 0.0062 15C -0.0001 0.0029 -0.0003 0.0100 -0.0016 0.0013 0.0006 0.0010 0.0020 0.1299 -0 .0002 0.0047 -0.0024 0.0055 C= Control location, Background location Results in bold type are positive.

3-14

Do mi nion Nuclea r Co nnecticut , Inc. Annu al Radiological Envi ro nmental Op erating Repo rt 2017 M illst one Power Station TABLE 5 SOIL (pCi/g dry wt.)

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

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

03 05/23/17 0.022 0.325 15.880 1.652 0.057 0.298 -0.012 0.035 -0.025 0.038 0.057 0.086 04 05/24/17 0.370 0.365 13.590 1.527 0.078 0.387 0.019 0.042 -0 .019 0.036 -0.059 0.083 14C 05/23/17 0.254 0.470 16.890 1.840 0.151 0.488 0.031 0.058 -0 .023 0.050 0.022 0.113 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

03 05/23/17 0.018 0.035 0.010 0.093 0.008 0.042 0.046 0.070 0.010 0.039 -0.116 0.328 04 05/24/17 -0.028 0.041 -0.010 0.083 0.012 0.044 0.044 0.075 0.027 0.039 0.044 0.340 14C 05/23/17 0.037 0.053 0.086 0.138 0.010 0.057 0.053 0.100 -0 .020 0.056 0.112 0.448 COLLECTION LOCATION DATE Sb-125 Cs-134 Cs-137 Ce-141 Ce-144 Ac-228

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

03 05/23/17 0.087 0.087 0.018 0.045 0.203 0.090 0.012 0.057 -0 .031 0.194 0.844 0.275 04 05/24/17 -0.019 0.11 1 0.052 0.039 0.317 0.090 -0.024 0.065 -0.099 0.243 0.015 0.370 14C 05/23/17 0.028 0.148 0.090 0.060 0.039 0.061 0.027 0.098 0.192 0.360 0.972 0.328 C= Control location , Background location Results in bold type are positive.

3-15

Do minio n Nuclea r Conn ecticut, Inc. Annua l Radiological Environm ental Operati ng Re po rt 20 17 M il lst one Powe r Station TABLE 6 MILK (pCi/1)

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

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

22 01 /18/17 0.123 0.392 1307 159 -1.276 5.061 -0.054 5.381 -6.568 15.66 0.099 4.119 Cow 02/08/17 -0.242 0.430 1372 157 4.731 4.674 -1.575 4.576 -9.858 17.26 0.084 3.501 03/23/17 0.109 0.234 7.1 5.6 1.7 1.2 1155 172 0.970 5.643 -1.413 5.122 6.861 20.34 -2.169 5.886 04/19/17 0.186 0.488 1296 168 -1.658 6.748 4.863 6.375 3.144 28.86 -0 .642 7.351 05/16/17 -0.063 0.073 1404 114 0.060 3.201 1.345 2.903 -3.128 14.37 0.920 3.578 06/21/1 7 -0 .380 0.433 0.9 4.6 0.6 0.8 1457 181 -1.408 6.732 0.658 5.719 7.898 21 .12 -3 .934 6.371 07/18/17 -0 .066 0.288 1246 174 3.51 3 4.158 5.301 4.904 -7.927 14.43 -5 .005 4.994 08/15/17 0.015 0.364 -1 .3 6.0 0.7 1.2 1368 192 -0 .724 5.900 2.086 5.435 2.317 17.90 -4.665 4.881 23 03/09/17 -0.262 0.469 3. 1 5.0 0.8 0.5 1384 218 -2.968 6.851 -5.959 6.595 1.464 23.77 1.465 7.544 Goat 04/05/17 0.001 0.101 1337 140 0.741 3.722 1.598 3.368 -4.393 13.04 -2.302 4.066 05/03/17 0.227 0.408 1624 195 3.781 6.012 3.775 5.284 -7 .376 23.82 0.646 6.434 06/07/17 -0 .227 0.304 -6.3 5.4 1.2 1.3 1843 179 -6.906 6.876 4.217 6.262 2.485 25.94 1.571 5.978 07/05/17 -0.054 0.373 1698 204 0.275 4.571 5.855 5.192 21 .07 19.01 -1 .237 5.818 08/01/1 7 0.094 0.286 1453 197 -0.535 5.884 4.325 5.822 -12.27 27.20 -2.415 5.657 09/05/17 0.045 0.395 6.9 6.9 0.5 1.0 1588 84.9 0.081 2.013 0.010 2.099 5.701 12.35 -0.025 3.493 10/03/17 -0.080 0.452 1934 189 0.777 6.377 2.229 5.976 -12.41 27.61 -0.824 7.178 Results in bold type are positive 3-16

Dom inion Nuclea r Connecticut, Inc. Annua l Radio logi ca l Environm enta l Ope rating Report 2017 Millstone Power Station TABLE 7 WELL WATER (pCi/1)

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

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

71 03/20/17 186 538 -13.4 34.7 -43.6 67.4 25.0 38.1 4.07 3.75 -1.70 5.01 3.98 7.91 0.43 4.13 05/17/17 545 698 19.2 28.6 41 .7 59.3 7.80 32.9 -1.89 3.13 -1.37 2.91 -3.50 6.46 0.02 2.84 08/23/17 201 497 24.8 33.4 -1.21 58.6 -12.9 43.6 0.39 3.82 1.17 4.37 -3.13 8.96 -4.14 3.86 11/08/17 -182 649 -13.5 32.6 27.6 58.1 -0.20 33.7 -0.97 3.63 -0.39 3.97 1.19 7.70 -1.86 3.64 72 03/13/17 -323 513 20.4 26.6 31.6 40.2 -8.19 29.4 -0.60 2.92 -0.38 3.15 4.89 5.25 0.63 2.66 05/17/17 149 555 -35.5 30.6 54.2 59.2 -22.7 35.5 -0.23 3.73 -2.50 3.14 2.81 7.78 0.49 3.52 08/23/17 -86 474 13.0 36.8 4.49 71.5 -17.4 43.4 0.84 3.71 2.52 3.64 -1.45 7.35 -0.20 3.45 11 /08/17 257 657 -14.2 33.1 -65.2 59.3 -31 .7 38.7 -0.03 4.46 1.74 4.06 -1.10 9.82 2.17 4.35 76 03/08/17 183 550 8.79 37.0 31.1 63.5 45.0 40.5 1.50 3.93 -2.48 4.06 -6.55 8.07 -0.42 4.18 05/15/17 23 560 -9.54 24.8 9.64 46.5 7.80 26.6 0.89 2.95 1.93 2.67 -3.08 5.68 0.32 2.93 08/23/17 -6 485 26.6 40.5 -33.7 64.9 40.3 44.4 0.00 4.22 -2.70 4.24 7.89 8.69 1.70 3.92 11/07/17 -1 39 651 -7.77 36.3 20.3 49.0 3.58 30.8 -1 .09 3.85 -0.10 3.75 1.79 6.54 -2.29 3.45 77 03/08/17 344 569 -20.2 44.3 44.7 78.5 16.5 46.0 -0.34 5.61 2.78 5.72 -8.41 9.88 3.66 4.57 05/15/17 -122 556 -23.0 31.4 -2.68 46.6 -0.95 37.7 -2.10 3.71 1.00 3.76 0.40 7.16 -0.91 3.37 08/23/17 6 481 -5.23 33.6 -17.9 46.1 27.8 39.2 0.36 3.77 -0.76 4.02 6.21 6.77 0.41 3.64 11/07/17 225 655 36.1 35.4 2.54 63.0 12.8 38.8 -1.71 3.94 -6.16 3.82 -0.41 7.51 3.64 3.65 78 03/08/17 -7 543 -37.6 44.5 69.3 77.6 17.3 46.8 -2.72 4.68 -3.20 4.50 -5.19 8.18 -0.49 3.47 05/15/17 -119 546 5.66 27.3 -58.2 42.8 -10.4 31.3 0.65 3.08 1.34 3.02 0.22 7.41 -0.83 3.50 08/23/17 -29 482 -8.84 33.2 -13.6 45.1 -22.1 39.5 0.62 3.21 -2.90 3.58 -0.31 6.80 -1.19 3.26 11/07/17 32 651 11.1 36.8 23.1 63.8 10.8 37.8 -0.71 4.00 -1.46 4.02 -4.49 7.61 3.17 3.79 79 03/20/17 442 557 -8.22 26.4 52.5 52.6 -14.3 33.2 0.61 2.85 -1 .04 2.92 -2.65 6.73 0.95 3.79 05/18/17 141 553 -33.8 40.5 33.1 101 7.57 41.7 2.26 4.67 -1.61 5.36 12.1 10.6 -0.86 6.07 08/24/17 329 510 -32.5 40.6 5.90 68.0 -35.5 44.7 2.72 4.09 -0.86 4.30 -0.78 8.23 3.43 4.25 11/08/17 481 682 13.4 33.2 11.4 70.3 1.21 36.7 2.15 3.30 -4.02 3.93 0.47 8.23 6.52 4.77 81 03/13/17 243 558 4.46 29.1 16.2 72.9 17.5 29.9 -2.27 3.61 -1.11 3.62 1.24 7.03 -1 .85 3.67 05/17/17 323 582 -5.30 37.4 55.8 71.5 7.21 39.5 -1.44 3.95 5.46 4.17 0.07 8.70 -2.33 3.44 08/24/17 563 525 2.55 34.6 41 .3 65.7 -2.28 37.0 1.35 3.88 -0.0 1 3.97 -0.46 7.95 0.11 3.88 11/08/17 298 668 0.89 43.4 108 77.9 -27.6 48.7 0.63 4.59 -1.65 4.74 -6.91 9.73 1.35 4.45 82 03/13/17 85 541 -1.22 35.3 33.2 71.1 -16.2 39.1 -3.33 3.66 -3.54 3.79 -6.29 7.39 1.97 3.41 05/17/17 -118 529 -8.86 35.6 41.9 71.8 -36.3 44.5 -2.06 3.76 -6.71 4.24 -0.99 9.00 -1.26 4.67 08/24/17 255 496 -26.4 42.4 -31.1 47.6 -11.0 46.1 -4.72 4.70 -2.67 4.83 3.55 9.65 4.37 4.65 11/08/17 369 667 -36.1 44.5 93.9 85.2 25.7 48.9 -1 .20 4.32 1.20 5.40 -4.45 9.47 -4.35 4.69 83 03/20/17 197 534 -9.45 39.7 45.8 73.9 6.61 44.2 1.51 3.45 -0.87 3.61 -1.45 7.76 1.57 3.37 05/17/17 -82 541 -32.7 37.6 -14.6 67.5 -8.59 42.9 0.86 4.57 -1.70 4.57 1.86 9.57 2.01 4.43 08/24/17 238 506 25.2 40.9 -18.7 64.0 25.5 41.9 -1.06 5.43 -0.97 4.55 9.59 10.3 -0.54 4.16 11/08/17 75 665 7.50 45.5 51.5 94.3 -32.8 45.1 0.56 4.95 -2.39 4.27 10.6 8.33 2.61 5.91 3-17

Dom inion Nuclear Connecticut, Inc. Annual Rad iological Environmental Operating Report 2017 Millstone Power Station TABLE 7 WELL WATER (pCi/1)

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

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

71 03/20/17 -5.17 10.9 5.14 4.92 0.89 9.26 1.19 4.65 0.85 38.5 0.81 10.5 3.69 8.12 2.05 4.91 05/ 17/17 0.97 7.81 0.04 2.97 1.06 5.56 -0 .19 3.50 -11.2 26.6 1.06 8.16 1.44 6.43 3.07 3.15 08/23/17 -12 .2 10.1 -0.92 4.11 0.87 7.19 -4.39 4.33 -31 .2 39.2 -3 .66 11 .5 -7.26 9.22 1.96 4. 13 11 /08/17 -4.18 8.91 0.90 4.23 -1.72 6.13 -1.30 3.66 -3.78 31.5 1.54 10.8 2.61 5.84 2.50 3.98 72 03/13/17 -13 .7 7.66 3.44 3.32 -0.79 5.56 -0.90 3. 45 -6.66 26.5 8.50 8.43 4.71 5.66 -1 .32 3.68 05/17/17 -7.29 8.32 3.30 3.77 -4.93 6.44 -0.30 3.80 1.61 33.0 -4.49 10.1 4.11 6.53 -1 .17 3.96 08/23/17 9.01 7.98 1.91 4.37 -3.40 7.41 1. 17 4.80 16.5 40.5 1.19 11.6 -10 .6 9.28 0.89 4.34 11 /08/17 -0.41 10.5 0.04 4.18 3.34 6.95 -0.71 5.03 25.8 33.1 -4.44 13.2 1.84 7.14 3.08 4.45 76 03/08/ 17 5.80 8.52 3.12 4.29 -2.75 6. 72 -0.95 4.85 -1 2.4 35.1 16.9 10.9 -2.64 6.38 2.38 4.58 05/15/ 17 3.56 6.81 7.31 3.36 0.93 4.59 -1.11 3.02 -1 .44 24.8 5.83 8.78 0. 10 4.30 0.80 3.21 08/23/ 17 -1.16 9.03 5.01 4.36 2.24 5.99 -0. 76 4.56 27.1 37.5 7.57 12.0 1.30 8.83 5.61 4.73 11/07/ 17 3.53 7.23 1.90 4.50 -1.59 5.76 -2.27 3.61 20.5 27.0 6.47 11.2 -2.95 6.10 1.65 3.98 77 03/08/ 17 5.50 12.3 15. 1 7.42 -5.43 8.66 4.79 5.86 24.5 48.9 -2.78 15.2 -6.74 7.47 -0.23 5.55 05/15/ 17 3.80 6.90 3.84 4.54 3.91 6.12 -1.87 3.74 -13.7 33.2 3.78 10.9 -1.03 5.77 2.82 4.13 08/23/17 28.2 9.88 8.18 4.11 0.50 6.80 -1.09 4.40 25.2 35.8 7.90 10.4 -2.16 10.4 1.53 4.29 11/07/ 17 -7.43 10.8 5.81 4.58 -2.80 6.76 -5.44 4.71 6.86 35.6 -1 .12 11.4 8.83 8.15 -0.51 4.77 78 03/08/ 17 -1 1.7 12.3 4.64 4.75 -0.09 7.79 0. 22 4.84 20.1 43.6 5.38 14.2 2.19 7.56 -2.73 5.30 05/15/ 17 -11.2 8.33 0.31 3.49 -4.62 5.24 -0.70 3.67 -23.0 28.0 1.83 9.30 -3.99 4.74 0.40 3.67 08/23/ 17 7.33 7.07 4.97 3.49 0.13 6.17 2.70 4.20 -65.2 36.4 0.61 10.6 4.63 8.48 0.04 4.01 11/07/17 -16 .5 9.85 6.46 4.32 4.36 7.27 -2 .60 4.54 20.9 34.0 4.43 11.6 -0 .64 7.31 -0.10 4.82 79 03/20/ 17 -0.08 6.72 2.46 3.11 -0.31 5.46 0.85 3.66 -14.0 25.4 -6.54 8.65 -2.54 6.19 0.30 3.43 05/18/17 -2.68 12.0 -0 .52 5.11 -6.33 8.05 0.63 5.31 -14.8 46.9 -4.25 11.9 -4.02 8.31 2.43 5.71 08/24/ 17 -2.22 8.91 1.92 4.21 1.46 7. 77 1.95 4.76 41.6 42.9 -3.70 12.1 -3.31 8.67 -5.03 5.01 11 /08/ 17 -2 .17 9.03 1.39 4.16 0.70 6.52 2.03 4.43 -2.91 37.2 2.46 10.2 -2.73 6.46 0.95 4.11 81 03/13/17 13.5 8.11 -0.44 4.10 -0.44 6.35 1.62 3.62 -2 .84 28.9 3.33 9.44 -0 .13 6.04 -0.67 3.82 05/17/17 10.8 10.0 -0.69 4.30 -1.51 7.53 -2.83 4.78 8.49 40.5 -4.97 11.9 4.63 8.18 -2.69 4.51 08/24/17 1.21 9.53 3. 18 4.40 -2.18 6.01 -0.82 4.59 16.1 30.1 1.48 10.7 -0.08 7.86 -0.39 4.05 11 /08/17 5.65 10.2 2.62 5.60 0.64 8.06 -3.6 1 5.41 13.8 43.0 4. 29 14.1 6.72 8.40 1.1 7 4.67 82 03/13/17 9.92 9.15 13.9 5.04 -4.98 6.10 -2.20 4.41 -20.2 31.3 -0.95 10.9 -3.20 7.26 1.93 3.89 05/17/17 -2 .07 9.33 11.1 4.91 5.06 6. 71 -7.35 4.23 -28.2 34.7 5.39 12.6 14.8 8.33 -0.99 4.03 08/24/17 0.09 9.94 7.77 5.30 -0.72 7.93 -4.49 5.05 -3.15 35.3 0. 74 14.3 -1.47 8.80 -0 .95 5.03 11/08/17 -1 .92 8.50 1.95 5.56 5.57 8.77 1.69 4.75 -8.38 39.6 13.7 14.8 2.38 8.69 1.55 4.93 83 03/20/17 6.08 7.42 0.93 4.35 -2.40 7.59 1.36 4.66 -1 4.5 34.8 -2.32 11.6 -2.43 8.18 0.20 4.40 05/ 17/17 -0.64 8.82 2.43 4.71 2.21 7.95 -1.35 5.09 -21.4 39.2 3.86 12.3 0.60 8.86 1.47 4.99 08/24/17 -0.38 10.1 0.46 5.61 -0.70 7.82 2.80 5.46 10.2 38.2 4.16 13.2 0. 18 8.78 -1.64 5.29 11 /08/17 4.43 12.7 1.67 5.22 -2.22 10.0 -4.68 5.58 -47.2 44.3 11.4 14.6 -3.61 8.29 -2.38 6.29 3-18

Do mi nion Nuclear Con necticut , Inc. Annua l Rad iologica l Environmenta l Ope rating Repo rt 20 17 M illstone Power Station TABLE 7 WELL WATER (pCi/1)

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

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

71 03/20/17 -0.41 4.28 7.38 20.5 -2.87 9.03 -7.23 17.0 05/17/17 -3.90 3.24 1.16 14.2 0.22 5.83 -2.09 11.8 08/23/17 -0.83 4.51 -5.01 24.0 2.28 7.35 10.7 14.7 11/08/17 -1.83 3.82 8.65 15.6 2.54 4.70 15.0 14.2 72 03/13/17 -2.16 3.23 8.51 17.0 3.93 4.67 7.74 11.8 05/17/17 3.91 3.77 18.0 17.1 -3.93 5.60 6.70 12.9 08/23/17 2.75 3.81 -6.14 21.4 0.64 5.80 3.74 13.1 11 /08/17 -0.91 4.36 -30.5 25.7 0.97 5.38 4.49 18.7 76 03/08/17 -4.43 4.09 8.54 17.5 -0.09 6.24 13.4 15.4 05/15/17 0.31 2.98 5.60 12.0 0.64 3.64 8.72 11.7 08/23/17 -2.02 4.44 -16.0 24.7 2.99 6.55 -5.01 16.3 11 /07/17 -1 .96 3.50 0.09 16.4 3.61 6.32 23.1 19.6 77 03/08/17 0.52 7.00 -0.02 23.7 -0.16 7.87 -18.4 20.1 05/15/17 -1.24 3.72 3.49 15.8 0.16 5.10 -5.80 14.7 08/23/17 5.46 3.80 -13.1 19.6 2.86 6.16 13.2 12.4 11 /07/17 -3.45 4.05 -6.49 19.0 6.38 6.61 0.32 16.2 78 03/08/17 -3.53 4.91 -0.59 21 .2 -1 .60 5.48 5.85 19.7 05/15/17 -1 .23 3.48 7.23 15.0 1.15 4.85 12.1 13.1 08/23/17 1.16 3.56 2.15 19.5 -1.22 5.46 -1.40 13.3 11 /07/17 0.30 4.13 3.66 21 .5 1.48 6.59 -4.86 14.7 79 03/20/17 -0.33 3.15 -8.24 17.6 1.99 6.35 -3.82 13.7 05/18/17 -3.24 4.90 -2.07 22.2 -5.11 7.68 -3. 13 19.7 08/24/17 1.55 4.40 -8.20 22.6 1.33 6.78 12.3 16.1 11 /08/17 0.63 4.67 0.09 15.5 3.91 6.82 -0.66 14.8 81 03/13/17 -1 .06 3.71 11 .0 18.2 5.48 6.25 -0.07 12.8 05/17/17 -4.41 4.73 -3.37 20.4 -0.59 8.10 -13.6 15.8 08/24/17 -1 .70 4.12 13.9 18.8 -5.86 5.48 4.39 15.3 11 /08/17 -4.24 4.80 13.4 24.0 1.70 7.58 -1 .89 16.6 82 03/13/17 -2.10 3.93 2.69 18.7 3.95 6.05 7.51 13.5 05/17/17 -5.13 4.32 3.63 20.8 -3.75 7.43 -4.75 15.0 08/24/17 0.74 5.10 -8.96 23.0 1.36 6.47 6.49 16.1 11 /08/17 -6.95 5.09 18.8 21 .6 -2.84 6.03 0.48 17.5 83 03/20/17 -1 .59 4.44 1.94 22.3 -1.55 6.83 -1.99 14.2 05/17/17 -1. 10 4.65 9.90 22.0 5.49 8.01 -0.42 16.7 08/24/17 -0.37 4.79 -2.35 20.6 4.36 8.07 -8.99 17.3 11 /08/17 -1 .72 5.70 0.25 26.0 2.27 7.72 -10.7 18.0 3-19

Dom inion Nuclear Co nnect icut, Inc. Annual Radiological Environ m ental Op erating Repo rt 2017 M illstone Power Stati on TABLE 8 FRUITS & VEG ET ABLES (pCi/g wet wt.)

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

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

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

07/18/17 Tomatoes 0.028 0.061 1.262 0.226 0.033 0.065 -0.005 0.008 0.004 0.007 0.005 0.015 0.000 0.008 07/18/17 Blueberries 0.028 0.119 1.172 0.328 -0.071 0.095 0.003 0.014 0.000 0.013 -0.007 0.024 0.009 0.013 10/10/17 Peppers -0.038 0.145 1.401 0.440 -0.036 0.140 0.006 0.017 -0.012 0.020 0.014 0.034 -0.002 0.014 10/10/17 Apples 0.012 0.147 0.483 0.287 0.01 7 0.139 -0.006 0.01 7 -0.002 0.018 -0.012 0.033 -0.010 0.019 COLLECTION DATE Type Zn-65 Nb-95 Zr-95 Ru-103 Ru -106 Sb-125 1-131

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

07/18/17 Tomatoes -0.018 0.019 0.008 0.008 0.005 0.012 -0.004 0.007 -0 .037 0.067 -0.006 0.019 0.000 0.009 07/18/17 Blueberries -0 .039 0.034 -0.003 0.013 -0.016 0.022 0.010 0.013 -0 .126 0.136 -0.024 0.038 0.006 0.015 10/10/17 Peppers -0 .043 0.052 0.006 0.017 -0.022 0.033 -0.001 0.016 -0 .071 0.167 0.019 0.057 -0.010 0.019 10/10/17 Apples -0 .002 0.040 0.006 0.018 0.026 0.029 0.005 0.017 -0.032 0.152 -0.016 0.048 -0.002 0.020 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La -140 Ce-141 Ce-144 Ac-228

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

07/18/17 Tomatoes 0.005 0.010 -0.005 0.007 0.009 0.029 0.002 0.009 0.003 0.012 -0 .008 0.049 0.014 0.029 07/18/17 Blueberries -0.014 0.012 -0.008 0.013 -0.053 0.046 0.002 0.012 0.000 0.020 0.025 0.087 0.076 0.054 10/10/17 Peppers 0.018 0.020 0.017 0.019 0.043 0.072 0.005 0.019 0.002 0.024 0.040 0.085 -0.033 0.063 10/10/17 Apples -0 .001 0.019 0.009 0.018 0.015 0.067 0.005 0.023 0.001 0.022 0.009 0.090 -0.035 0.065 C= Control location, Background location Results in bold type are positive.

3-20

Do mi nion Nucl ear Conn ecticut, Inc. Annual Rad iologi cal Environm ental Op erat ing Repo rt 2017 M illstone Power Station TABLE 8 FRUITS & VEG ET ABLES (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

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

07/18/17 Tomatoes 0.039 0.077 1.466 0.287 -0.011 0.086 0.001 0.010 0.001 0.009 0.006 0.020 -0 .003 0.008 07/18/17 Blueberries 0.126 0.114 0.623 0.325 0.009 0.116 -0.004 0.013 0.000 0.015 -0.018 0.027 -0 .001 0.013 10/10/17 Peppers 0.089 0.133 2.036 0.425 -0.003 0.116 0.002 0.015 -0.001 0.014 -0.004 0.033 0.004 0.015 10/10/17 Apples 0.077 0.145 0.543 0.275 -0.018 0.135 0.000 0.017 0.007 0.015 0.001 0.024 0.007 0.015 COLLECTION DATE Type Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

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

07/18/17 Tomatoes -0.039 0.026 0.006 0.010 0.003 0.017 -0.004 0.010 0.079 0.090 0.020 0.027 0.000 0.011 07/18/17 Blueberries -0.009 0.038 0.004 0.014 -0.008 0.025 0.005 0.013 -0.036 0.125 0.016 0.035 0.005 0.014 10/10/17 Peppers -0.048 0.040 0.005 0.016 0.003 0.026 0.001 0.016 0.000 0.113 0.002 0.044 -0.008 0.019 10/10/17 Apples -0.009 0.032 0.002 0.016 0.014 0.028 -0.004 0.015 -0.029 0.144 0.002 0.038 0.012 0.021 COLLECTION DATE Type Cs-134 Cs-137 Ba-140 La-140 Ce-1 41 Ce-144 Ac-228

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

07/18/17 Tomatoes -0.005 0.010 -0.009 0.010 0.046 0.037 -0.006 0.011 0.020 0.015 0.015 0.070 0.012 0.037 07/18/17 Blueberries -0.004 0.016 0.001 0.016 0.006 0.047 -0.013 0.019 0.018 0.018 0.021 0.069 0.067 0.060 10/10/1 7 Peppers 0.005 0.01 5 0.013 0.015 -0.019 0.058 0.012 0.016 0.024 0.023 0.041 0.101 -0.031 0.055 10/10/17 Apples -0.005 0.017 0.016 0.017 0.007 0.065 0.005 0.024 0.010 0.025 -0.057 0.099 -0.034 0.068 C= Control location, Background location Results in bold type are positive.

3-2 1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 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

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

06/13/17 1.633 0.321 4.850 0.736 -0.100 0.165 0.012 0.019 -0.004 0.018 0.001 0.039 -0.010 0.018 10/03/17 1.906 0.375 4.221 0.650 0.026 0.153 -0.012 0.019 -0.014 0.017 0.011 0.035 -0.014 0.018 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

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

06/13/17 -0.020 0.044 0.010 0.019 -0.006 0.040 -0.008 0.016 -0.081 0.190 0.018 0.050 -0.011 0.021 10/03/17 0.027 0.045 0.008 0.019 0.023 0.036 0.011 0.018 -0.061 0.144 0.011 0.052 0.007 0.035 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/13/17 -0.010 0.023 -0.01 3 0.022 0.067 0.079 -0.011 0.020 0.019 0.023 0.026 0.094 0.087 0.079 10/03/17 -0.002 0.019 0.001 0.020 0.079 0.084 -0.012 0.016 0.016 0.030 -0.061 0.120 0.046 0.073 LOCATION 10 COLLECTION DATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

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

06/13/17 1.157 0.280 3.428 0.544 0.054 0.140 0.002 0.016 0.004 0.014 -0 .004 0.030 0.001 0.015 10/03/17 1.149 0.383 3.656 0.711 -0.065 0.202 -0.006 0.022 0.009 0.018 0.019 0.041 0.004 0.018 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

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

06/13/17 -0.022 0.041 0.002 0.014 0.009 0.027 -0.009 0.015 -0.044 0.144 0.017 0.044 0.018 0.021 10/03/17 -0.028 0.048 0.019 0.021 0.015 0.027 0.006 0.024 -0.047 0.179 0.002 0.057 0.004 0.035 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/13/17 -0.003 0.017 -0.007 0.016 -0.017 0.066 0.001 0.018 -0.021 0.027 0.042 0.120 0.130 0.065 10/03/17 -0.001 0.020 0.007 0.024 0.010 0.112 0.004 0.026 -0.012 0.032 -0.058 0.126 0.119 0.123 Results in bold type are positive.

3-22

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 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

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

06/13/17 0.859 0.309 3.875 0.659 -0.012 0.151 0.005 0.020 -0.014 0.017 -0.011 0.037 0.006 0.019 10/03/17 1.613 0.313 3.418 0.457 -0.057 0.132 -0.012 0.015 0.003 0.012 -0.005 0.035 0.003 0.013 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

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

06/13/17 -0.009 0.040 0.014 0.019 -0.011 0.031 0.009 0.016 0.046 0.147 0.026 0.053 0.014 0.022 10/03/17 -0.013 0.039 0.008 0.014 0.015 0.027 -0.008 0.014 0.073 0.136 -0.016 0.039 0.008 0.029 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/13/17 0.018 0.022 0.025 0.021 0.046 0.074 0.000 0.020 -0.006 0.029 0.037 0.117 0.150 0.103 10/03/17 0.001 0.018 0.017 0.016 0.012 0.077 -0.002 0.020 -0.008 0.025 0.038 0.091 0.205 0.101 LOCATION 26C COLLECTION PATE Be-7 K-40 Cr-51 Mn-54 Co-58 Fe-59 Co-60

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

06/13/17 0.955 0.358 4.217 0.716 -0 .1 03 0.157 -0.003 0.016 -0.009 0.020 0.022 0.035 0.000 0.015 10/03/17 1.454 0.263 5.570 0.608 -0.016 0.152 0.011 0.016 -0.003 0.017 -0.006 0.035 -0.004 0.014 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125 1-131

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

06/13/17 -0.030 0.046 0.003 0.019 -0.007 0.031 -0.007 0.017 0.003 0.166 -0.006 0.055 0.003 0.023 10/03/17

-0.033 0.039 0.011 0.016 0.033 0.029 0.001 0.017 0.043 0.151 0.020 0.044 0.003 0.032 Cs-134 Cs-137 Ba-140 La-140 Ce-141 Ce-144 Ac-228

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

06/13/17 0.012 0.017 0.001 0.018 0.031 0.070 -0.030 0.023 -0.004 0.027 -0.007 0.105 0.050 0.079 10/03/17

-0.001 0.018 -0.004 0.020 0.008 0.088 0.013 0.021 -0.021 0.029 0.018 0.110 0.049 0.150 Results in bold type are positive.

3-23

Dominion Nucle ar Co nnecticut, Inc. Annu al Rad iological En vironme ntal Ope rati ng Re po rt 2017 M illst on e Powe r Station TABLE10 SEA WATER (pCi/1)

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

~ (+/-) (+/-) (+/-) (+/-) (+/-) (+7-)

01/31/17 813 156 27.6 45.4 315 145 17.1 49.7 -4.25 5.21 -1 .07 5.00 9.79 11 .2 02/28/17 559 210 14.9 41 .5 130 197 -37.9 37.7 -0.65 5.38 0.67 5.02 9.26 8.53 03/28/17 851 224 -36.0 38.0 227 118 12.9 36.3 0.45 4.10 -0.58 4.16 -5.27 8.94 04/25/17 158 172 5.95 28.7 326 91 -43.9 29.6 1.03 3.76 0.09 3.55 2.74 7.22 05/30/17 268 187 9.86 33.2 228 120 53.6 36.0 0.02 4.50 0.20 4.09 -6.67 7.66 06/27/17 49 179 -4 .18 28.7 319 98 26.1 29.8 1.68 3.57 -0.45 3.53 1.01 9.03 07/25/17 265 195 2.43 29.1 403 115 17.1 31 .6 -0.02 3.86 -2.14 4.16 -5.59 8.21 08/29/17 346 179 -19.6 43.0 252 123 -20.8 42.8 -0.05 4.93 -0.78 4.54 2.74 7.49 09/26/17 446 207 -4.59 28.8 309 80 -6.44 30.4 -0.89 2.95 -0.73 3.36 1.46 6.40 10/31/17 1990 300 2.36 40.1 286 128 -2.99 40.7 -1 .39 5. 30 -0.79 5.62 13.3 10.8 11 /28/17 649 204 9.77 27.5 301 88 1.87 30.1 -0.58 3.59 0.18 3.97 0.72 7.23 12/26/17 11 169 -13.0 32.9 282 97 1.82 36.0 -1.06 3.58 -2.20 3.52 1.24 7.46 COLLECTION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

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

01/31 /17 -2.64 5.57 -5.33 14.3 -1 .58 5.35 -0.45 10.5 2.26 6.07 -29.7 49.3 -3.62 15.5 02/28/17 -2.15 3.61 -11.2 11 .9 -5.16 4.54 2.35 7.72 2.51 4.56 -39.6 51 .9 -5.04 12.8 03/28/17 4.74 4.92 -8.38 11.1 -2.28 3.89 2.17 7.39 -1.63 4.26 6.38 30.7 -1.18 11.8 04/25/17 -3.22 4.08 -3.09 8.85 -1.58 4.23 0.94 5.34 -1.18 3.95 -10.1 34.4 -5.46 8.37 05/30/17 2.42 3.28 -2.38 9.88 0.96 3.76 -2 .97 7.51 -2.38 4.62 -19.4 35.6 -5.53 11.8 06/27/17 3.16 4.26 -2.11 10.2 2.26 3.27 3.60 6.15 -0.21 3.91 10.9 33.2 -3.29 9.93 07/25/17 -2.21 4.60 -1 .59 9.07 1.61 4.03 0.42 7.09 -4 .08 3.83 4.64 33.1 1.23 12.1 08/29/17 0.53 4.58 -3.59 9.27 -4.77 4.82 -0.44 9.33 -3.69 5.22 39.8 41 .2 -1.10 12.5 09/26/17 1.10 2.87 -2.1 5 7.43 2.45 3.53 -1 .04 5.12 -1.19 3.43 -4.90 26.2 -7.42 8.76 10/31/17 -2.84 4.80 -5.04 12.3 0.30 4.25 -1 .09 8.68 -0.77 4.76 -0.94 44.3 -2.76 12.0 11/28/17 -0.73 3.74 -6.27 8.79 4.37 3.57 0.34 5.74 -1 .66 3.53 4.27 30.6 6.08 10.5 12/26/17 2.18 3.81 0.08 7.72 0.81 3.92 0.29 5.45 1.37 4.07 -0 .23 34.5 0.55 9.83 Results in bold type are positive.

3-24

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station TABLE10 SEAWATER (pCi/1)

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

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

01/31/17 5.60 8.42 3.93 5.57 3.62 5.65 -1 .57 24.9 -5 .87 8.79 -5 .36 22.0 02/28/17 2 .01 5.66 1.00 5.53 -3 .86 5.39 5.30 19.6 -0.80 6.15 -7 .13 20.6 03/28/17 2 .25 7.41 1.44 4.23 0.45 4.48 9.49 20.0 -4 .04 7.25 -8.10 14.3 04/25/17 -1.46 4.88 -2.56 3.67 0.19 3.46 -3.14 14.5 -6 .55 5.30 2.35 14.3 05/30/17 -3 .14 6.70 0.37 4.32 -1 .31 3.60 -18.1 16.8 2.49 5.66 -2 .23 15.4 06/27/17 -3 .67 4.67 -1 .38 4.29 -0 .32 3.80 -4 .24 14.9 3.91 5.06 -5 .96 14.0 07/25/17 -1 .16 3.88 2 .17 3.67 1.23 3.80 -4 .71 13.5 -0.50 5.04 -0 .67 15.2 08/29/17 0.87 6.34 0.08 5.71 -0 .95 5.27 11 .2 16.5 5.72 5.68 -6 .22 20.2 09/26/17 0.91 6.41 2.37 3.64 -3.81 2.98 15.7 16.3 -3.61 5.39 4.55 12.2 10/31/17 0.10 5.69 -0 .78 6.27 4.10 5.96 12.1 20.3 -0.98 5.85 -0.02 19.4 11/28/17 -0.73 4.01 -4.00 3.71 0.08 3.88 -21.4 12.7 1.28 3.72 3.82 13.7 12/26/17 -1.45 6.21 -1.91 4.44 1.61 3.49 2.17 18.3 4.63 5.19 0.65 14.2 LOCATION 37C COLLECTION DATE H-3 Be-7 K-40 Cr-51 Mn -54 Co-58 Fe-59

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

03/21 /17 17 173 -16.0 28.2 231 96 -1 .57 31 .5 -1 .22 3.35 1.73 3.21 8.92 6.6 06/06/17 -36 95 29 .9 35.1 217 93 15.5 41 .1 1.38 4.54 -1.29 4.48 -4.46 9.9 08/15/17 -5 125 17.7 33.3 346 97 -16.7 34.8 -3.01 4.26 -2.20 3.59 -2.81 7.8 11 /21/17 10 168 8.80 43.6 262 105 -11 .0 42.2 -1.62 3.73 -2.34 4.49 2.76 8.6 COLLECTION DATE C0-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106 Sb-125

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

03/21 /17 -1 .34 3.02 -2.97 7.58 1.13 3.20 4.73 5.66 1.78 3.68 3.41 30.3 -3.55 8.32 06/06/17 -0.48 4.83 -15.5 12.8 1.32 3.84 5.12 7.56 1.93 4.57 -16.6 41.6 1.90 12.8 08/15/17 2.79 4.33 -3.53 10.0 -1.49 4.20 -4.57 7.56 1.68 4.82 14.0 31.8 2.01 10.2 11 /21 /17 -1.98 3.73 -11 .8 12.3 0.31 3.86 5.58 8.09 0.01 5.03 -3.09 39.5 -5.72 14.2 COLLECTION DATE 1-131 Cs-134 Cs-137 Ba-140 La-140 Ac-228

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

03/21 /17 -0.88 5.86 -1 .71 3.45 2.28 3.72 -0.61 18.8 -2.82 4.94 -2.99 11.4 06/06/17 3.25 5.89 -3.93 4.73 1.48 4.81 11.4 18.2 -0.77 4.08 11 .8 15.3 08/15/17 1.80 4.67 2.94 4.35 -3.21 3.77 -9.63 13.0 1.43 4.75 1.65 15.6 11/21 /17 -5.85 6.86 -1.22 4.95 -2.99 5.14 -2 .32 24 .3 -1.56 5.88 -4.02 18.5 C= Control location, Background location Results in bold type are positive.

3-25

Dominion Nuclear Connecticut, Inc. Annual Radiologica l Environmental Operating Report 2017 Millstone Power Station TABLE11 BOTTOM SEDIMENT (pCi/g dry wt.)

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

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

31 06/01 /17 -0.134 0.352 16.06 1.548 -0.188 0.389 0.003 0.039 -0.037 0.041 -0.070 0.082 31 07/31 /17 0.049 0.292 16.43 1.498 0.026 0.287 0.007 0.034 0.002 0.034 0.086 0.084 32 05/24/17 -0.144 0.520 22.76 2.325 -0.1 96 0.532 0.013 0.073 -0 .012 0.058 -0.039 0.126 32 11 /08/17 0.182 0.301 16.27 1.570 -0.141 0.299 -0.012 0.037 0.002 0.031 -0 .016 0.079 33 05/04/17 0.184 0.214 18.28 1.386 -0.011 0.206 -0.008 0.028 -0.018 0.028 -0 .021 0.065 33 08/16/17 -0.023 0.247 19.20 1.616 0.197 0.237 -0.028 0.034 0.006 0.032 -0.001 0.081 34 05/04/17 -0.093 0.173 18.46 1.281 0.052 0.166 -0.014 0.022 -0 .016 0.024 -0.003 0.047 34 08/16/17 -0.013 0.195 19.66 1.483 0.072 0.204 0.023 0.026 0.002 0.027 0.025 0.070 37C 06/01 /17 -0.217 0.288 15.07 1.553 0.034 0.316 -0.001 0.039 -0.009 0.036 0.003 0.077 37C 10/11 /17 0.138 0.187 14.77 1.095 -0.003 0.184 -0.003 0.021 -0.023 0.022 0.011 0.054 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

31 06/01 /17 0.006 0.040 -0.066 0.109 0.044 0.050 0.039 0.072 -0 .030 0.040 -0.012 0.352 31 07/31 /17 0.005 0.032 -0.079 0.084 0.020 0.038 0.021 0.064 -0 .008 0.035 -0.066 0.280 32 05/24/17 0.031 0.065 -0.131 0.168 -0.004 0.073 0.110 0.107 0.014 0.064 -0.155 0.572 32 11 /08/17 -0.007 0.043 -0.070 0.102 -0.032 0.035 0.062 0.068 -0.014 0.034 -0.211 0.329 33 05/04/17 0.010 0.032 -0.016 0.080 0.015 0.029 -0.018 0.045 0.007 0.026 -0.027 0.210 33 08/16/17 0.020 0.033 -0.131 0.108 -0.004 0.035 0.021 0.057 0.035 0.029 0.177 0.280 34 05/04/17 -0.028 0.026 0.047 0.064 0.047 0.032 -0.042 0.041 0.005 0.020 -0 .037 0.185 34 08/16/17 0.006 0.027 -0.189 0.083 0.006 0.026 -0.024 0.049 0.003 0.025 0.118 0.215 37C 06/01 /17 -0.019 0.032 -0.117 0.098 0.001 0.042 0.009 0.062 0.003 0.037 0.097 0.298 37C 10/11 /17 -0.010 0.025 -0.047 0.060 0.015 0.021 -0.016 0.037 -0.001 0.022 0.057 0.198 C= Control location, Background location.

3-26

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station TABLE 11 BOTTOM SEDIMENT (pCi/g dry wt.)

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

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

31 06/01/17 0.008 0.040 -0.047 0.116 -0.039 0.076 0.048 0.048 0.005 0.044 0.077 0.337 31 07/31/17 0.003 0.030 0.033 0.093 0.065 0.063 0.106 0.056 0.008 0.034 0.709 0.229 32 05/24/17 -0.048 0.065 0.012 0.163 -0.061 0.111 0.128 0.109 0.033 0.071 0.361 0.647 32 11/08/17 -0.008 0.030 0.040 0.088 0.025 0.053 0.013 0.040 -0.030 0.032 0.253 0.333 33 05/04/17 0.010 0.025 -0.028 0.076 0.007 0.037 0.006 0.033 0.025 0.029 0.142 0.226 33 08/16/17 -0.017 0.030 0.047 0.079 0.005 0.043 -0.003 0.034 -0.006 0.035 0.310 0.148 34 05/04/17 -0.011 0.022 -0.013 0.059 -0.010 0.032 0.028 0.028 0.030 0.024 0.034 0.201 34 08/16/17 0.007 0.023 0.000 0.066 -0.048 0.040 0.029 0.033 0.025 0.026 0.084 0.208 37C 06/01/17 0.012 0.038 -0.015 0.095 -0.021 0.064 0.009 0.038 0.008 0.040 0.073 0.161 37C 10/11/17 -0.009 0.018 -0.004 0.062 -0.002 0.035 -0.017 0.026 0.024 0.021 0.050 0.163 C= Control location, Background location.

3-27

Dom inion Nuclear Connecticut, Inc. Annual Rad iological Environm ent al Operati ng Report 2017 M illstone Power Station TABLE12 AQUATIC FLORA - FUCUS (pCi/g wet wt.)

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

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

29 03/08/17 0.1123 0.2312 4.5670 0.8212 0.0251 0.1970 0.0131 0.0283 0.0060 0.0212 -0.0281 0.0560 29 05/23/17 0.3012 0.2040 6.8670 0.6176 -0.1210 0.1282 0.0114 0.0151 0.0071 0.0139 -0.0040 0.0303 29 08/15/17 0.0504 0.0960 6.8130 0.5452 0.0209 0.0890 -0 .0071 0.0105 -0.0074 0.0100 -0.0028 0.0235 29 11 /15/17 0.2945 0.2130 7.5120 0.6763 0.0431 0.1116 -0.0010 0.0146 -0.0039 0.01 52 -0.0209 0.0318 32 03/08/17 0.1142 0.1018 6.7320 0.4969 -0.0039 0.0965 -0.0056 0.0112 0.0013 0.0114 0.011 2 0.0284 32 05/23/17 0.1267 0.1898 9.1250 0.9998 -0.0347 0.1587 -0.0010 0.0243 -0.0124 0.0195 0.0266 0.0563 32 08/15/17 0.1018 0.1416 8.0110 0.6689 -0.1416 0.1485 -0.0039 0.0163 -0.0094 0.0163 -0.0040 0.0348 32 11/1 5/17 0.0847 0.1584 6.8210 0.7806 0.0375 0. 1452 0.0026 0.01 56 -0.0099 0.0169 -0 .0032 0.0367 35 03/08/17 0.1716 0.1892 4.7250 0.6575 -0.1699 0.171 9 0.0053 0.0191 -0.0123 0.0179 0.0096 0.0397 35 05/24/17 0.3347 0.1457 6.4350 0.6112 0.1058 0.1113 0.0060 0.0109 -0 .0043 0.0107 -0.0181 0.0284 35 07/31 /17 0.1012 0.1307 6.7890 0.6934 -0.0195 0.1264 0.0176 0.0143 -0 .0001 0.0134 0.0064 0.0347 35 11 /09/17 0.1448 0.1889 6.1990 0.6413 0.2243 0.1901 0.0141 0.0202 -0.0100 0.0206 -0.0066 0.0389 36 03/28/17 0.2104 0.1759 5.8670 0.7263 0.0873 0.1266 0.0044 0.0144 0.0147 0.0160 0.0031 0.0390 36 06/01/17 0.2062 0.1224 6.6810 0.4693 -0.0239 0.0812 0.0018 0.0101 -0 .0052 0.0099 -0.0040 0.0234 36 08/01/17 0.0797 0.0983 6.7760 0.5066 0.0377 0.1043 0.0028 0.0108 -0.0006 0.0112 0.0141 0.0233 36 10/11/17 0.0047 0.0980 6.7210 0.5690 0.0163 0.0879 -0 .0064 0.0105 -0.0117 0.0103 -0.0064 0.0266 90 03/31/17 0.5125 0.1707 5.7620 0.5417 -0.0429 0.1131 0.0005 0.0114 -0.0122 0.0111 0.0066 0.0293 90 05/04/17 0.1594 0.1738 6.2820 0.5505 0.0008 0.0853 -0.0014 0.0118 -0.0040 0.0114 -0.001 3 0.0265 90 08/16/17 0.0570 0.1023 6.3100 0.5940 0.0077 0.0983 0.0059 0.0123 -0.0018 0.0119 0.0087 0.0267 90 11 /27/17 0.3494 0.2467 8.5580 0.6394 -0.0140 0.1126 0.0081 0.0133 0.0016 0.0122 -0.0038 0.0288 Results in bold type are positive.

3-28

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 M illstone Power Station TABLE12 AQUATIC FLORA- FUCUS (pCi/g wet wt.)

Collection Location Date Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

29 03/08/17 0.0125 0.0223 -0.0326 0.0628 -0.0117 0.0257 -0.0306 0.0421 0.0067 0.0239 0.0398 0.2378 29 05/23/17 -0 .0062 0.0127 0.0078 0.0321 0.0062 0.0148 0.0111 0.0245 0.0007 0.0145 -0.0340 0.1212 29 08/15/17 -0.0017 0.0118 -0.0393 0.0325 -0 .0033 0.0111 -0.0038 0.0217 0.0003 0.0120 0.0186 0.0968 29 11/15/17 0.0112 0.0140 -0.0401 0.0393 -0.0004 0.0145 0.0028 0.0271 -0.0090 0.0154 -0.0432 0.1196 32 03/08/17 0.0064 0.0116 -0.0317 0.0283 -0.0006 0.0118 0.0206 0.0208 -0.0029 0.0119 0.0134 0.1030 32 05/23/17 -0 .0015 0.0290 0.0298 0.0547 -0.0165 0.0210 0.0181 0.0375 0.0049 0.0210 -0.0018 0.1648 32 08/15/17 0.0039 0.0185 -0.0145 0.0417 0.0082 0.0159 -0.0066 0.0292 0.0026 0.0169 0.1157 0.1560 32 11/15/17 0.0062 0.0155 -0.0254 0.0445 0.0102 0.0175 0.0069 0.0315 0.0090 0.0168 0.0040 0.1482 35 03/08/17 0.0124 0.0185 0.0132 0.0438 -0.0023 0.0188 0.0088 0.0320 0.0050 0.0218 -0.0042 0.1706 35 05/24/17 0.0114 0.0124 -0.0022 0.0336 -0.0004 0.0129 -0.0206 0.0207 0.0102 0.0102 0.0052 0.1020 35 07/31/17 0.0114 0.0169 -0.0052 0.0381 -0.0005 0.0136 0.0184 0.0251 -0.0141 0.0157 0.0260 0.1116 35 11 /09/17 0.0126 0.0196 0.0218 0.0482 0.0027 0.0189 -0.0298 0.0354 0.0012 0.0197 0.0649 0.1781 36 03/28/17 0.0039 0.0149 -0.0446 0.0454 -0.0010 0.0175 0.0036 0.0277 0.0052 0.0162 0.0620 0.1617 36 06/01/17 -0 .0012 0.0096 0.0065 0.0267 0.0092 0.0094 0.0010 0.0157 -0.0014 0.0104 -0 .0370 0.0874 36 08/01/17 0.0045 0.0130 0.0070 0.0296 0.0067 0.0120 0.0102 0.0213 -0.0064 0.0114 0.0139 0.0964 36 10/11/17 -0.0027 0.0135 0.0124 0.0318 0.0112 0.0113 -0.0121 0.0186 -0.0108 0.0112 -0.0148 0.1132 90 03/31 /17 -0.0052 0.0125 -0.0160 0.0293 0.0009 0.0121 0.0015 0.0201 -0 .0142 0.0132 -0.0487 0.0980 90 05/04/17 -0 .0149 0.0127 -0.0205 0.0298 0.0004 0.0116 0.0132 0.0201 0.0025 0.0119 -0.0256 0.0926 90 08/16/17 -0 .0016 0.0123 -0 .0032 0.0375 0.0107 0.0126 -0.0015 0.0217 -0.0006 0.0117 -0.0357 0.1118 90 11/27/17 -0.0038 0.0157 -0.0003 0.0282 -0.0092 0.0130 -0.0020 0.0211 0.0024 0.0125 -0.0579 0.1130 Results in bold type are positive.

3-29

Dom inion Nuclear Connecticut, Inc. Annua l Radiologica l Envi ronmental Operating Repo rt 2017 M illstone Power Station TABLE12 AQUATI C FLORA - FUCUS (pCi/g wet wt.)

Collection Location Date Ag-110m Sb-125 1-131 Cs-134 Cs-137 Ac -228

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

29 03/08/17 -0.0285 0.0207 -0.0556 0.0669 0.0139 0.0332 0.0195 0.0264 0.0282 0.0236 0.0254 0.1858 29 05/23/17 -0.0063 0.0119 -0.0233 0.0365 0.0020 0.0253 0.0126 0.0173 0.0029 0.0147 0.1920 0.0721 29 08/15/17 -0.0017 0.0108 -0.0032 0.0286 0.0039 0.0167 0.0050 0.0125 0.0044 0.0109 0.0426 0.0967 29 11/15/17 0.0017 0.0129 -0.0250 0.0407 0.0066 0.0203 0.0001 0.0162 0.0032 0.0138 0.0744 0.1077 32 03/08/17 0.0138 0.0109 -0.0057 0.0320 -0.0026 0.0171 0.0074 0.0128 0.0010 0.0120 0.0309 0.0446 32 05/23/1 7 -0.0089 0.0198 0.0433 0.0505 0.0226 0.0328 0.0077 0.0205 -0.0183 0.0213 0.1076 0.0929 32 08/15/1 7 -0.0003 0.0156 -0 .0327 0.0445 -0.0230 0.0253 -0.0134 0.0185 -0.0028 0.0174 0.1051 0.0689 32 11/15/17 -0.0033 0.0146 0.0252 0.0455 0.0177 0.0248 -0.0134 0.0194 0.0073 0.0157 0.1044 0.1 173 35 03/08/17 -0.0119 0.0177 0.0119 0.0559 -0.0176 0.0302 -0.0097 0.0236 0.0137 0.0195 0.0556 0.0888 35 05/24/1 7 0.0010 0.0087 -0.0227 0.0277 0.0039 0.0202 0.0133 0.0114 0.0025 0.0107 0.0905 0.0467 35 07/31/17 0.0070 0.0138 -0 .0034 0.0404 -0.0131 0.0252 -0.0016 0.0161 0.0086 0.0157 0.0158 0.0618 35 11 /09/1 7 -0 .0025 0.0188 0.0368 0.0515 -0 .0082 0.0298 0.0110 0.0226 0.0151 0.0201 -0.0184 0.0745 36 03/28/17 0.0187 0.0149 -0.0072 0.0396 0.0024 0.0256 -0.0138 0.0177 -0.0150 0.0174 0.0754 0.0722 36 06/01 /17 -0.0071 0.0086 0.0220 0.0261 0.0095 0.0193 -0.0010 0.0102 0.0023 0.0094 0.0685 0.0466 36 08/01/17 -0 .0011 0.0101 -0.0115 0.0315 0.0008 0.0193 0.0097 0.0116 0.0020 0.0115 0.0630 0.0462 36 10/11 /17 -0 .0095 0.0123 0.0094 0.0308 -0 .0008 0.0176 0.0036 0.0125 -0.0066 0.0134 0.0796 0.0546 90 03/31 /17 -0 .0010 0.0096 0.0014 0.0297 0.0051 0.0249 0.0015 0.01 09 -0.0054 0.0114 0.0509 0.0675 90 05/04/17 -0 .0172 0.0111 -0.0297 0.0280 0.0441 0.0257 -0.0026 0.0132 -0.0039 0.0123 0.1195 0.0870 90 08/16/17 0.0012 0.0114 -0.0005 0.0325 0.0148 0.0164 0.0097 0.0155 -0.0044 0.0125 0.0075 0.0627 90 11 /27/17 -0.0116 0.0120 -0.0037 0.0338 0.0161 0.0164 0.0151 0.0145 0.0024 0.0138 0.1318 0.0791 Results in bold type are positive.

3-30

Do mi nion Nuclea r Conn ecti cut, Inc. Annual Radiologica l Environm ent al Ope rating Repo rt 20 17 M illstone Power Station TABLE 13 FISH (pCi/g wet wt.)

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

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

32 04/19/17 -0.105 0.247 3.196 0.739 0.253 0.259 0.012 0.026 0.025 0.028 0.002 0.053 32 10/17/17 0.064 0.236 3.189 0.656 0.074 0.262 0.031 0.030 -0.018 0.029 0.014 0.056 35 05/04/17 -0.082 0.273 3.037 0.825 0.028 0.290 0.001 0.028 -0.020 0.030 0.017 0.056 35 07/12/17 0.132 0.275 3.177 0.988 0.037 0.273 -0.006 0.031 0.007 0.024 0.020 0.082 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

32 04/19/17 0.008 0.031 -0.079 0.059 -0.018 0.027 -0.033 0.047 -0.014 0.028 -0.158 0.218 32 10/17/17 0.062 0.037 -0.002 0.068 0.002 0.029 0.029 0.053 0.005 0.029 -0.088 0.294 35 05/04/17 -0.013 0.026 0.011 0.079 0.038 0.032 0.001 0.043 -0.016 0.038 0.090 0.299 35 07/12/17 0.022 0.038 0.044 0.087 0.013 0.028 0.001 0.062 0.027 0.036 0.243 0.287 COLLECTION LOCATI ON DATE Ag -110M Sb-125 1-131 Cs-134 Cs-137 Ac -228

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

32 04/19/17 0.005 0.025 0.001 0.071 -0.038 0.057 -0.014 0.034 0.016 0.027 0.058 0.103 32 10/17/17 0.019 0.026 -0 .055 0.079 -0.024 0.033 -0 .011 0.034 0.008 0.029 -0.050 0.111 35 05/04/17 -0 .004 0.030 0.041 0.088 0.016 0.055 -0 .004 0.032 0.004 0.033 0.063 0.120 35 07/12/17 -0.019 0.036 -0.074 0.085 -0.020 0.050 -0 .033 0.035 0.004 0.040 0.001 0.137 Results in bol d are positive.

3-31

Do mi nion Nuclea r Conn ecti cut, Inc. Annual Rad iological Environmental Ope ra t ing Repo rt 20 17 M il lst one Powe r Stat ion TABLE 14 OYSTERS (pCi/g wet wt.)

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

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

31 04/11/17 0.010 0.129 2.002 0.430 -0.006 0.130 0.002 0.018 -0.007 0.015 0.005 0.035 31 11/14/17 0.021 0.379 1.617 0.907 0.085 0.403 -0.014 0.049 -0 .016 0.040 -0.016 0.077 89 03/08/17 0.026 0.393 2.305 0.694 -0.127 0.378 -0.014 0.039 -0.016 0.047 -0.013 0.066 89 10/11 /17 -0.009 0.343 3.098 0.939 0.026 0.363 -0.008 0.043 -0.051 0.043 -0.008 0.079 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

31 04/11 /17 0.001 0.015 0.014 0.032 0.012 0.013 0.011 0.025 -0.010 0.014 -0.093 0.137 31 11 /14/17 0.027 0.042 -0.089 0.091 -0.004 0.036 -0.016 0.071 0.034 0.044 -0.170 0.344 89 03/08/17 0.020 0.040 0.009 0.065 0.032 0.047 0.065 0.077 -0.046 0.052 -0.086 0.435 89 10/11 /17 0.000 0.039 -0.080 0.096 0.029 0.043 -0.043 0.061 -0.014 0.041 -0.185 0.393 COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

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

31 04/11 /17 -0.003 0.014 0.003 0.040 0.002 0.018 0.006 0.017 -0.003 0.016 -0.011 0.065 31 11/14/17 -0.019 0.041 -0.036 0.117 -0.027 0.064 0.024 0.045 -0.006 0.040 -0 .099 0.160 89 03/08/17 0.003 0.040 -0.034 0.132 -0.088 0.065 0.017 0.050 -0.009 0.047 0.01 1 0.130 89 10/11/17 -0.003 0.038 -0.142 0.098 0.018 0.070 0.024 0.039 -0.014 0.037 -0.064 0.142 Results in bol d type are positive.

3-32

Dom inion Nuclea r Conn ecticut, Inc. Ann ual Rad iologica l Environmental Opera ti ng Report 20 17 M il lst one Power St ation TABL E 15 CLAMS (pCi/g wet wt.)

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

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

29 04/24/17 -0.013 0.182 2.068 0.585 0.104 0.181 -0.013 0.023 -0.006 0.019 -0.017 0.054 29 09/13/17 -0 .103 0.330 2.643 0.939 -0.139 0.345 -0.009 0.034 0.002 0.033 -0.014 0.067 31 06/23/17 0.135 0.220 1.964 0.849 0.034 0.282 0.022 0.031 -0.032 0.029 0.021 0.073 31 10/24/17 -0.274 0.266 1.558 0.927 -0.180 0.267 0.014 0.027 0.030 0.033 0.038 0.071 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

29 04/24/17 -0 .017 0.020 -0.049 0.051 -0.010 0.025 0.031 0.045 0.006 0.022 -0.071 0.199 29 09/13/17 0.012 0.038 0.000 0.081 0.011 0.032 -0.023 0.063 -0.011 0.037 -0.116 0.353 31 06/23/17 0.021 0.027 0.047 0.075 -0 .011 0.030 0.045 0.051 0.015 0.033 0.149 0.293 31 10/24/17 0.017 0.040 -0.029 0.077 -0.014 0.032 -0.071 0.058 -0.001 0.033 -0.248 0.322 COLLECTION LOCATION DATE Ag-110M Sb-125 1-1 31 Cs-134 Cs-137 Ac-228

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

29 04/24/17 0.007 0.019 -0 .045 0.053 0.010 0.035 0.003 0.023 0.009 0.024 0.047 0.079 29 09/13/17 0.013 0.036 -0.010 0.092 -0.019 0.071 -0.012 0.039 -0.010 0.038 0.007 0.140 31 06/23/17 0.011 0.031 0.101 0.086 0.005 0.041 0.020 0.032 -0 .036 0.037 -0.001 0.148 31 10/24/17 0.021 0.036 0.018 0.093 -0.042 0.042 0.024 0.041 -0.003 0.040 -0.077 0.120 Results in bold are positive.

3-33

Dom inion Nuclear Connecticut, Inc. Annual Rad iological Environmental Operating Report 2017 M illstone Power Station TAB LE 16 LOBSTERS (pCi/g wet wt.)

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

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

35 05/04/17 0.137 0.355 2.027 0.964 -0.125 0.347 0.035 0.043 -0.011 0.038 -0.052 0.086 35 07/13/17 -0.024 0.303 3.987 0.907 -0.166 0.300 0.026 0.036 -0.011 0.037 0.015 0.068 89C 06/13/17 -0.066 0.215 2.306 0.786 -0.048 0.207 -0.036 0.033 0.008 0.029 -0.029 0.057 89C 08/16/17 -0.138 0.298 2.496 0.660 0.014 0.285 0.013 0.033 0.020 0.034 -0.027 0.062 COLLECTION LOCATION DATE Co-60 Zn-65 Nb-95 Zr-95 Ru-103 Ru-106

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

35 05/04/17 -0.011 0.038 -0.085 0.093 0.002 0.040 0.011 0.073 0.009 0.042 0.140 0.363 35 07/13/17 0.001 0.037 -0.031 0.075 0.007 0.035 0.030 0.063 -0.031 0.037 -0.045 0.368 89C 06/13/17 -0.017 0.024 0.001 0.072 -0.005 0.032 0.005 0.053 -0.025 0.028 0.065 0.292 89C 08/16/17 0.011 0.031 0.021 0.083 0.032 0.033 -0.005 0.057 -0.014 0.035 -0.406 0.308 COLLECTION LOCATION DATE Ag-110M Sb-125 1-131 Cs-134 Cs-137 Ac-228

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

35 05/04/17 0.011 0.039 -0.094 0.112 -0.024 0.069 -0.031 0.045 0.014 0.043 0.122 0.164 35 07/13/17 -0.014 0.032 0.089 0.096 -0 .008 0.053 -0.019 0.041 0.014 0.036 0.001 0.150 89C 06/13/17 -0.002 0.029 0.037 0.092 -0.011 0.032 0.010 0.031 -0.003 0.030 -0.044 0.117 89C 08/16/17 -0.013 0.031 -0.061 0.097 -0.052 0.050 -0.007 0.035 0.000 0.035 0.029 0.127 C=Control Location, Background Location Results in bold are positive.

3-34

Domi nion Nuclear Conn ecticut, Inc. Annua l Radiol ogica l Envi ron m ental Opera ting Repo rt 2017 Mil lston e Power St ation

4. PISCUSSION 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 broad leaf 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 and two soil samples. Cs-137 and Sr-90 from atmospheric nuclear weapons testing in the 1960's 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 2017, Cs-137 was detected in two soil samples and Sr-90 was not detected. The values detected were above the LLD of 0.18 pCi/g and it is common to find these levels of Cs-137 in undisturbed soil 22 . No other REMP samples show an increase in the Cs-137 and the overall trend is decreasing with time.

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 CaS04(Tm) Panasonic model UD-804 ASx TLDs. Readings are recorded as uR/hr. The unit uR 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 and seven in 2015. None were loaded in 2008, from 2011 to 2014. The exposure rate measurements at two of the three additional TLD locations remain basically unchanged from the background measurements performed prior to any cask loading (six quarter background average mid 2003 - 2004: 9.5 uR/hour at Location 73, 7.5 uR/hour at Location 74 and 6.9 uR/hour at Location 75). At Location 73 the readings have increased 0.2 uR/hour with an average of 7.9 uR/hour for 2017. In 2016, six ISFSls were loaded into the Horizontal Storage Modules and the station offsite dose from ISFSI has increased from 0.038 mrem/year to 0.041 mrem/year and is below the 25 mrem/year 40.190 CFR limit.

4-1

Domini on Nuclear Conn ecticut, Inc. An nual Radiological Environ mental Operati ng Repo rt 2017 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 at 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 7.9 uR/hour. This is equivalent to an annual dose of about 69 mrem .

The averages of all indicator locations for the period when Millstone MPS 1 was still in operation ( 1996 to 1999) exhibit the effects of N-16 BWR turbine building skyshine to immediate areas onsite. Skyshine increased exposure rates as high as 6 uR/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 2017 data for Location 3 shows an increase likelr attributable to 2-3 µR/hr gradients observed from the granite bedrock of the MPS Site2 .

4-2

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station Figure 4.1-1 uR/hr Annual Gamma Exposure Rate - 20Year History

All I ncicators

All Controls

Indicator Loe 1 CJ Indicator Loe 3 8

6 l9 l!I 0

!<I !<I Fi 4-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Repo rt 2017 Mil lstone 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. Inner 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. An increase in the deviation between the indicators and the control (figure 4.2-1) has been noted. This is currently under evaluation .

Figure 4.2-1 Air Particulate Gross Beta Activity pCi/m Monthly Average - 2017 0.0200 ~ Indicators

- Control 0.0180 0.0160 0.0140 0.0120 0.0100 0.0080 0.0060 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 4.2-2 Air Particulate Gross Beta Activity Monthly Averages - 5 Year Trend 0.021 ..._- - - - - - - - - - - - - - - - - - - - - =.---.1=n= 1 =ca

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Do minion Nucl ear Con necti cut , Inc. Ann ual Radiologica l Environm ental Op erating Repo rt 2017 Mil lston e Power Stat ion 4.3 Airborne Iodine {Table 3)

Charcoal cartridges are included at all of the air particulate monitoring stations for the collection of atmospheric iodine. These cartridges were analyzed for 1-131 every two weeks .

No detectable levels of 1-131 were seen in the 2017 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. 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. Except for Location 3, the trend appears to be declining with time . Baseline levels should be useful in the future , when site characterization and decommissioning of the station become the focus during preparations for license termination.

Figure 4.5-1 Cs-137 in Soil 2

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0 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 Year 4-5

Dom inion Nuclear Conn ecticut, Inc. Annual Radiological Environmental Op erat ing Report 2017 Millstone Power Station 4 .6 Milk (Table 6)

Typically, the most sensitive indicator of fission product existence in the terrestrial environment is the radiological analysis of milk samples. Milk is a widely consumed food ;

therefore it is usually one of the most critical exposure pathways. Since 1996 all dairy (cow) farms close enough to MPS to be considered an indicator location (i.e. within 10 miles) have ceased operation. One cow milk location and one goat location, both between ten and twelve miles from the station , were sampled as extra, non-required samples and results are shown in Table 6. Naturally occurring K-40 is the only positive result seen in both cow milk and goat milk.

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 2017 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.

4.7 Well Water (Table 7)

All REMP well samples including ISFSI well samples were less than the Minimum Detectable Concentration (MDC). 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 2017. ISFSI well results have been documented in Table 7 as required by the Connecticut Sitting Council.

4.8 Fruits and Vegetables (Table 8)

Consistent with past years, this media did not show any station effects. Naturally occurring K-40 was detected in all 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 . It's not necessary to have a continuous sampler at the control location due to the historical relative consistency noted in seawater background activity near the Millstone.

4-6

Dominion Nuclea r Connecticut, Inc. Annual Radiological En vironme ntal Op erat ing Report 2017 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, Giant's Neck {Location 37C), six weekly grab samples are obtained for quarterly compositing .

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

Measured station related levels of H-3 inseawater 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 2017 MPS had two refueling outages requiring the processing and subsequent discharge of refueling water, which explains the slightly elevated activity values in the first and fourth quarter of 2017. The highest value in 2017 for seawater was 1900 pCi/1, which is below regulatory LLD for tritium specified in NUREG 1301 of 3000 pCi/1. The total annual exposure from the liquid discharge pathway for 2017 was 0.001 mrem/yr.

Figure 4.10-1 H-3 Curies Released versus Seawater Concentration 18 Year Trend 1200 , vvv ..- . , ... _ .

J 1100 1000 I I - - c uries discharged I

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Dominion Nuclear Connecticut, Inc. Annual Radiologica l Environmental Ope ra t ing Report 2017 Mill stone Power Station 4.11 Bottom Sediment (Table 11)

There was no station related radioactivity detected in bottom sediment samples in 2017.

Naturally occurring K-40 is seen in all samples and naturally occurring Ac-228 in some samples. Bottom sediment is not a significant dose pathway to man, especially at areas not typically used by the public.

4.12 Aquatic Flora (Table 12)

Aquatic flora is a sensitive indicator of low levels of man-made radioactivity (e.g ., Mn-54, Co-58, Co-60, Zn-65, 1-131 and Ag-110m) in the environment so it was added as a required sample at four locations in revision 28 of the REMODCM . Naturally occurring Be-7 and Ac-228 appear in some samples and K-40 in all samples. One sample on the Thames River identified 4.41 E-4 pCi/g of 1-131. No other samples taken in the identified 1-131 . MPS had a gaseous release of 1 µCi 1-131 during the second quarter, but this was not identified in any other samples taken in the second and third quarter. The positive 1-131 sample could also be attributed to any one of the many contributing sources in the Thames River. The potential contributing 1-131 sources to the Thames River include the Submarine Base, Electric Boat, Pfizer, and medical wastes from 1-131 treatment.

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 2017 there were no challenges in obtaining oyster samples and four extra samples were obtained.

Naturally occurring K-40 is seen in all samples. MPS related Ag-11 Om 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. However, in 2017 no plant related radioactivity was detected in oysters.

4.15 Clams (Table 15)

Occasionally this media indicates the presence of station related radioactivity. In 2017 no activity was observed except for the naturally occurring K-40.

4.16 Lobsters (Table 16)

In 2017 no activity was observed except for the naturally occurring K-40 .

4-8

Domin ion Nuclea r Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station

s. 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 027-00, March 13, 2017 and Revision 28 , October 1, 2017.

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 Station's Environmental Monitoring Data, Connecticut Department of Environmental Protection , Division of Radiation, March 2006.

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

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

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

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

22) MP-HP0-98137 , "Determination Of Cs-137 In Undisturbed Soil At Locations Greater Than 10 Miles From Millstone Site ," July 28 , 1998.

5-1

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station APPENDIX A LAND USE CENSUS FOR 2017 A-1

Dominion Nuclear Co nnecticut , Inc. Annu al Radi ologi cal Environm enta l Operating Report 2017 M illstone Power Station The annual land use census in the vicinity of MPS was conducted as required by the MPS REMODCM. Typically the cow milk locations are identified by a review of the annual registration information obtained from the State of Connecticut Department of Agriculture licensing website at https://www.elicense.ct.gov/Lookup/GenerateRoster.aspx. Gardens are located by a drive-by during the harvest season. Although broadleaf sampling was performed and may be used in lieu of a garden census, gardens were included in the 2017 census . Only vegetable gardens having an area of more than 500 square feet need to be identified. The Land Use Census conservatively assumes that the nearest resident within each directional sector has a garden to minimize measuring gardens at individual's residence. If a garden is closer than the nearest resident in a sector, then the garden is listed as the closest garden in that sector. The search for new goat farms included consulting goat association records, which includes the American Goat Owners Association (http://adqa.org/),

contacting previous owners. A search of food sources other than milk and local gardens was conducted using the search route on "Local Food Guide to Connecticut" at http://www.farmfresh.org/.

Results of the land use census are given in Tables A-1 through A-2. No new dairy animals with in 10 miles of the MPS were located during the census.

The 2017 Land Use Census also evaluated aquatic sampling exposure pathways from the fish and shell fish located around MPS. Attachment 1 shows shellfish beds around MPS from the Bureau of Aquaculture of the Department of Agriculture. The salt water fishing areas are identified Attachment 2.

There were no changes in restricted areas, receptor locations, new exposure pathways or modifications to existing exposure pathways as a result of this assessment.

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

A-2

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station TABLE A-1 2017 Survey Resident/Garden Downwind Direction Miles Meters N 0.95 1521 NNE 0.53 854 NE 0.47 763 ENE 0.97 1554 E 0.92 1475 ESE 1.06 1701 SE NIA NIA SSE NIA NIA s NIA NIA SSW NIA NIA SW 2.28 3670 WSW 1.95 3130 w 1.78 2858 WNW 1.51 2423 NW 1.35 2179 NNW 0.51 816 Notes:

1. No gardens located closer than resident.

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

Table A-2 Milk and other foods within five miles of MPS - 2017 Sector Miles Business Location Comments NE 2.1 Private residence Waterford Goats - not milking ENE 3.0 Secchiaroli Farms Waterford Has pigs but feed sources not local NW 4 .3 Smith's Acres Niantic Fruits and vegetables WNW 5.0 Four Mile River Farm Old Lyme Eggs, beef, pork NW 5.2 Scott's Yankee Farmer East Lyme Fruits and vegetables, cider A-3

Dominio n Nuclear Connecticut, Inc. Annual Radiologica l Environmental Operat ing Report 2017 M illstone Power Station MP-CHEM-17-13 Attachment One Shellfish Beds in Vicinity of Millstone Gommacal i'fta 'C' t Jf"PIUt'.al ~

Legend Shellfish Area Classific.ition

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Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station MP-CHEM-17-13 Attachment Two Saltwater Fishing Resource Map Millstone Site A-5

Domini on Nuclear Con necticut, Inc. Annual Radio logical Environmental Operating Report 2017 M illston e Power Station APPENDIX 8

SUMMARY

OF INTERLABORATORY COMPARISONS B-1

Dom inio n Nuclear Con necticut, Inc. Ann ual Ra diological Environmental Ope rating Report 2017 Mill ston e Power Sta t ion Summary of Results - Inter-laboratory Comparison Program (ICP)

This appendix summarizes the lntercomparison Program of the Teledyne Brown Engineering (TBE)

Laboratory as required by technical specifications for each MPS unit. 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. Analytics Evaluation Criteria Analytics ' evaluation report provides a ratio of TBE's result and Analytics' known value. Since flag values are not assigned by Analytics, TBE evaluates the reported ratios based on internal QC requirements based on the DOE MAPEP criteria .

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

C. DOE Evaluation Criteria MAPEP's evaluation report provides an acceptance range with associated flag values . MAPEP defines three levels of performance:

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

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

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

For the TBE laboratory, 168 out of 173 analyses performed met the specified acceptance criteria . Five analyses did not meet the specified acceptance criteria for the following reasons and were addressed through the TBE Corrective Action Program .

1. The ERA April 2017 two nuclides in water were evaluated as Not Acceptable. (NCR 17-09)

a. The Zn-65 result of 39.3 pCi/L, exceeded the lower acceptance limit of 47.2. The known value was unusually low for this study. The sample was run in duplicate on two different detectors. The results of each were 39.3 +/- 18.2 pCi/L (46% error and lower efficiency) and 59.3 +/- 8.23 pCi/L (13.9% error and higher efficiency). The result from the 2nd detector would have been well within the acceptable range (47.2 - 65.9) and 110.2% of the known value of 53.8 pCi/L.

B-2

Dom inion Nucl ear Connecti cut, Inc. Annu al Radiological Environm ental Op erating Re port 2017 Millston e Power Station

b. The Sr-89 result of 40.7 pCi/L exceeded the lower acceptance limit of 53.8. All associated QC and recoveries were reviewed and no apparent cause could be determined for the failure. The prior three cross-check results were from 99 - 115% of the known values and the one that followed this sample (November, 2017) was 114% of the known value.

2. The DOE MAPEP August 2017 air particulate U-238 result of 0.115 +/- 0.025 Bq/sample was higher than the known value of 0.087 +/- 0.002 with a ratio of 1.32, therefore the upper ratio of 1.30 (acceptable with warning) was exceeded . TBE's result with error easily overlaps with the acceptable range. MAPEP does not evaluate results with any associated error. Also, the spike level for this sample was very low (2.35 pCi) compared to TBE's normal LCS of 6 pCi. TBE considers this result as passing . (NCR 17-15)

3. The Analytics September 2017 soil Cr-51 result was evaluated as Not Acceptable (Ratio of TBE to known result at 0.65). The reported value was 0.230 +/- 0.144 pCi/g and the known value was 0.355 +/- 0.00592 pCi/g . The sample was counted overnight for 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />; however the Cr-51 was spiked at a very low level and had a counting error of 65%. Cr-51 has a 27-day half-life, making low-level quantification even more difficult. The error does not appear to have been taken into consideration for this result. If it had been evaluated with the error, the highest result would have been 105% of the reference value, which is acceptable. Also, the known value is significantly lower than TB E's typical MDC for this nuclide in a soil matrix and would typically not be reported to clients (unless specified). The results of all of the previous cross-checks have been in the acceptable (80 - 120%) range. TBE will evaluate further upon completion of the next ICP sample. (NCR 17-16)

4. The ERA November 2017 water Sr-90 sample was evaluated as Not Acceptable. TBE's result of 27.1 pCi/L exceeded the lower acceptance range (30.8 -48.0 pCi/L). After reviewing the associated QC data for this sample, it was determined that although the spike recovery for Sr-90 was within our laboratory guidelines (70% -130% ), both the spike result and our ERA result were biased low. The original cross-check sample was completely consumed and we were unable to reanalyze before submitting the result. We have modified our preparation process to avoid this situation for future cross-check samples. We also have enhanced LIMS programming to force a LCSD when a workgroup includes cross-check samples (as opposed to running a DUP).

(NCR 17-19)

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

B-3

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station Analytics Environmental Rad ioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Month/Year Identification Matrix Nucl ide Units Known Ratio of TBE to Evaluation Reported (b)

Number Value(a) Ana lytics Resu lt Value March 2017 E11811 Milk Sr-89 pCi/L 87 97.7 0.89 A Sr-90 pCi/L 12.4 16.2 0.77 A E11812 Milk Ce-141 pCi/L 135 145 0.93 A Co-58 pCi/L 153 150 1.02 A Co-60 pCi/L 182 183 1.00 A Cr-51 pCi/L 258 290 0.89 A Cs-134 pCi/L 104 120 0.87 A Cs-137 pCi/L 142 140 1.02 A Fe-59 pCi/L 135 129 1.05 A 1-131 pCi/L 92.6 97 .9 0.95 A Mn-54 pCi/L 173 164 1.05 A Zn-65 pCi/L 208 199 1.04 A E1181 3 Charcoal 1-1 31 pCi 92 93 .9 0.98 A E11814 AP Ce-141 pCi 99.9 101 0.99 A Co-58 pCi 95.4 104 0.92 A Co-60 pCi 140 127 1.10 A Cr-51 pCi 211 201 1.05 A Cs-134 pCi 82 .1 83.2 0.99 A Cs-137 pCi 92.8 97.0 0.96 A Fe-59 pCi 107 89.3 1.20 A Mn-54 pCi 106 114 0.93 A Zn-65 pCi 137 138 0.99 A E11816 Soil Ce-141 pCi/g 0.258 0.250 1.03 A Co-58 pCi/g 0.241 0.258 0.93 A Co-60 pCi/g 0.312 0.315 0.99 A Cr-51 pCi/g 0.439 0.500 0.88 A Cs-134 pCi/g 0.176 0.207 0.85 A Cs-137 pCi/g 0.304 0.317 0.96 A Fe-59 pCi/g 0.210 0.222 0.95 A Mn-54 pCi/g 0.292 0.283 1.03 A Zn-65 pCi/g 0.353 0.344 1.03 A E11815 Water Fe-55 pCi/L 1600 1890 0.85 A (a) The Analytics known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation.

(b) Analytics evaluation based on TBE internal QC limits:

A = Acceptable - reported result falls within ratio limits of 0.80-1.20 W = Acceptable with warning - reported result falls within 0. 70-0.80 or 1.20-1 .30 N = Not Acceptable - reported result falls outside the ratio limits of< 0. 70 and > 1.30 B-4

Dominion Nucl ear Conn ecticut, Inc. Annual Radiological En vi ronmental Opera ting Report 2017 Millstone Power Station Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Identification Known Ratio of TBE to Evaluation MonthNear Matrix Nuclide Units Reported Number Value (a) Analytics Result (b)

Value June 2017 E11844 Milk Sr-89 pCi/L 81 .3 92.6 0.88 A Sr-90 pCi/L 12.1 13.5 0.90 A E11846 Milk Ce-1 41 pCi/L 142 151 0.94 A Co-58 pCi/L 147 155 0.95 A Co-60 pCi/L 185 191 0.97 A Cr-51 pCi/L 321 315 1.02 A Cs-134 pCi/L 168 188 0.89 A Cs-137 pCi/L 148 150 0.99 A Fe-59 pCi/L 116 115 1.01 A 1-131 pCi/L 102 93 .6 1.09 A Mn-54 pCi/L 168 172 0.98 A Zn-65 pCi/L 195 204 0.96 A E11847 Charcoal 1-131 pCi 87.9 84.8 1.04 A E11845 AP Sr-89 pCi 70.8 79.1 0.90 A Sr-90 pCi 9.10 11 .5 0.79 w E11848 AP Ce-141 pCi 112 116 0.96 A Co-58 pCi 119 119 1.00 A Co-60 pCi 171 146 1.17 A Cr-51 pCi 270 241 1.12 A Cs-134 pCi 152 144 1.05 A Cs-137 pCi 114 115 0.99 A Fe-59 pCi 94 .1 88.3 1.07 A Mn-54 pCi 139 132 1.06 A Zn-65 pCi 141 156 0.90 A E11849 Water Fe-55 pCi/L 1840 1890 0.97 A July 20 17 E11901 AP GR-A pCi 50.1 44.2 1.13 A GR-B pCi 218 233 0.93 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 A cceptable - reported result falls outside the ratio limits of < 0. 70 and > 1. 30 B-5

Domi nion Nuclear Con necticut, Inc. Annual Ra diological Enviro nmental Operating Report 2017 Millston e Power St ation Analytics Environmental Radioactivity Cross Check Program Te ledyne Brown Engineering Environmental Services TBE Identificati on Known Ratio of TBE to MonthNear Matrix Nuclide Units Reported Evaluation (bl Number Value (a) Analytics Resu lt Value September 2017 E11914 Milk Sr-89 pCi/L 84.3 82.7 1.02 A Sr-90 pCi/L 12.6 12.1 1.04 A E11915 Milk Ce-141 pCi/L 93.9 87.0 1.08 A Co-58 pCi/L 115 117 0.98 A Co-60 pCi/L 265 262 1.01 A Cr-51 pCi/L 273 217 1.26 w Cs-1 34 pCi/L 186 201 0.93 A Cs-137 pCi/L 175 172 1.02 A Fe-59 pCi/L 137 125 1.09 A 1-13 1 pCi/L 78.0 71 .0 1.10 A Mn-54 pCi/L 128 123 1.04 A Zn-65 pCi/L 206 184 1.12 A E11916 Charcoal 1-131 pCi 71.9 64.4 1.12 A E11917 AP Ce-141 pCi 80 .1 86.3 0.93 A Co-58 pCi 110 116 0.95 A Co-60 pCi 277 260 1.07 A Cr-51 pCi 275 215 1.28 w Cs-134 pCi 192 199 0.96 A Cs-137 pCi 165 170 0.97 A Fe-59 pCi 122 124 0.98 A Mn-54 pCi 120 122 0.99 A Zn-65 pCi 175 183 0.96 A E11918 Water Fe-55 pCi/L 1630 1630 1.00 A E11 919 Soi l Ce-14 1 pCi/g 0.136 0.142 0.96 A Co-58 pCi/g 0.179 0.191 0.94 A Co-60 pCi/g 0.405 0.429 0.94 A Cr-51 pCi/g 0.230 0.355 0.65 N (1)

Cs-1 34 pCi/g 0.272 0.328 0.83 A Cs-137 pCi/g 0.336 0.356 0.94 A Fe-59 pCi/g 0.210 0.205 1.02 A Mn-54 pCi/g 0.210 0.201 1.05 A Zn-65 pCi/g 0.301 0.301 1.00 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 17-16 (page B-3)

B-6

Dom inion Nucl ear Conn ecticut, Inc. Annu al Radio logical Environ menta l Op erating Repo rt 2017 Millston e Power Station Analytics Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Known Identification Ratio of TBE to Month/Year Matrix Nuclide Units Reported Evaluation (b)

Number Value (a) Analytics Result Value December 2017 E1 2054 Mi lk Sr-89 pCi/L 92 .1 92 .3 1.00 A Sr-90 pCi/L 18.3 16.9 1.09 A E12055 Mi lk Ce-141 pCi/L 97 .8 98 .3 0.99 A Co-58 pCi/L 92.3 89 .9 1.03 A Co-60 pCi/L 176 173 1.02 A Cr-51 pCi/L 226 242 0.93 A Cs-134 pCi/L 118 125 0.95 A Cs-137 pCi/L 148 141 1.05 A Fe-59 pCi/L 123 113 1.08 A 1-1 31 pCi/L 66 .0 57.8 1.14 A Mn-54 pCi/L 173 161 1.08 A Zn-65 pCi/L 233 211 1.10 A E12056 Charcoal 1-131 pCi 48 .1 47.5 1.01 E12057A AP Ce-14 1 pCi 108 111 0.97 A Co-58 pCi 89 .5 102 0.88 A Co-60 pCi 223 196 1.14 A Cr-5 1 pCi 311 274 1.13 A Cs-134 pCi 141 142 1.00 A Cs-137 pCi 162 160 1.01 A Fe-59 pCi 121 129 0.94 A Mn-54 pCi 177 182 0.97 A Zn-65 pCi 203 239 0.85 A E12058 W ater Fe-55 pCi/L 1970 1740 1.13 A E1 2059 AP Sr-89 pCi 71 .2 87.4 0.81 A Sr-90 pCi 12.9 16.0 0.81 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 8-7

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station 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 Va lue February 2017 17-MaS36 Soil Ni-63 Bq/kg -5 .512 (1) A Sr-90 Bq/kg 571 624 437-811 A 17-MaW36 Water Am-241 Bq/L 0.693 0.846 0.592 - 1.100 A Ni-63 Bq/L 13.4 12.2 8.5 - 15.9 A Pu-238 Bq/L 0.7217 0.703 0.492 - 0.914 A Pu-239/240 Bq/L 0.9277 0.934 0.654 - 1.214 A 17-RdF36 AP U-234/233 Bq/sample 0.0911 0.104 0.073 - 0.135 A U-238 Bq/sample 0.0967 0.107 0.075 - 0.139 A 17-RdV36 Vegetation Cs-134 Bq/sample 6.44 6.95 4.87 - 9.04 A Cs-137 Bq/sample 4.61 4.60 3.22 - 5.98 A Co-57 Bq/sample -0 .0229 (1) A Co-60 Bq/sample 8.52 8.75 6.13 - 11 .38 A Mn-54 Bq/sample 3.30 3.28 2.30 - 4.26 A Sr-90 Bq/sample 1.30 1.75 1.23 - 2.28 w Zn-65 Bq/sample 5.45 5.39 3.77 - 7.01 A August 2017 17-MaS37 Soil Ni-63 Bq/kg 1130 1220 854 - 1586 A Sr-90 Bq/kg 296 289 202 - 376 A 17-MaW37 Water Am-241 Bq/L 0.838 0.892 0.624 - 1.160 A Ni-63 Bq/L -0.096 (1) A Pu-238 Bq/L 0.572 0.603 0.422 - 0.784 A Pu-239/240 Bq/L 0.863 0.781 0.547-1 .015 A 17-RdF37 AP U-234/233 Bq/sample 0.103 0.084 0.059 - 0.109 w U-238 Sq/sample 0.115 0.087 0.061 - 0.113 N (2) 17-RdV37 Vegetation Cs-134 Bq/sample 2.34 2.32 1.62 - 3.02 A Cs-137 Bq/sample 0.05 (1) A Co-57 Bq/sample 3.32 2.8 2.0 - 3.6 A Co-60 Bq/sample 2.09 2.07 1.45 - 2.69 A Mn-54 Bq/sample 2.90 2.62 1.83 - 3.41 A Sr-90 Bq/sample 1.17 1.23 0.86 - 1.60 A Zn-65 Bq/sample 6.07 5.37 3.76 - 6.98 A (a) The MA PEP known value is equal to 100% of the parameter present in the standard as determined by gravimetric and/or volumetric measurements made during standard preparation.

(b) DOEIMAPEP evaluation:

=

A Acceptable - reported result falls within ratio limits of 0.80-1 .20

=

W Acceptable with warning - reported result falls within 0. 70-0.80 or 1.20-1 .30

=

N Not Acceptable - reported result falls outside the ratio limits of < 0. 70 and > 1.30 (1) False positive test (2) See NCR 17-15 (page B-3)

B-8

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Ope rating Report 2017 Millstone Power Station ERA Environmental Radioactivity Cross Check Program Teledyne Brown Engineering Environmental Services TBE Identification Known Acceptance Month/Year Matrix Nuclide Units Reported Evaluation (bl Number Value (a) Limits Value March 2017 MRAD-26 AP GR-A pCi/sample 76 .3 85.5 28 .6 - 133 A April 2017 RAD-109 Water Ba-133 pCi/L 49 .2 49 .7 40.8 - 55.1 A Cs-134 pCi/L 83 .2 90 .1 74.0- 99 .1 A Cs-137 pCi/L 202 206 185 - 228 A Co-60 pCi/L 51 .2 54.7 49 .2 - 62 .7 A Zn-65 pCi/L 39.3 53 .8 47 .2 - 65.9 N (1)

GR-A pCi/L 53 .6 75 .0 39 .5 - 92.3 A GR-B pCi/L 42. 7 38 .5 25.5 - 46.0 A U-Nat pCi/L 50.1 55.6 45.2 - 61.7 A H-3 pCi/L 7080 6850 5920 - 7540 A Sr-89 pCi/L 40 .7 66.2 53 .8 - 74.3 N (1)

Sr-90 pCi/L 26 .9 26 .7 19.3 - 31.1 A 1-131 pCi/L 26.7 29 .9 24.9 - 34 .9 A September 2017 MRAD-27 AP GR-A pCi/sample 40 .9 50 .1 16.8 - 77 .8 A AP GR-B pCi/sample 58.0 61.8 39 .1 - 90.1 A October 2017 RAD-111 Water Ba- 133 pCi/L 71 .3 73.7 61 .7-8 1.1 A Cs-134 pCi/L 43 .0 53 .0 42 .8 - 58.3 A Cs-137 pCi/L 48.2 52 .9 47 .6-61.1 A Co-60 pCi/L 69 .0 69 .5 62 .6 - 78.9 A Zn-65 pCi/L 335 348 313 - 406 A GR-A pCi/L 32.5 35 .6 18.3 - 45.8 A GR-B pCi/L 24 .3 25.6 16.0 - 33.6 A U-Nat pCi/L 36 .6 37.0 30.0 - 40.9 A H-3 pCi/L 6270 6250 5390 - 6880 A 1-13 1 pCi/L 26.4 24.2 20.1-28.7 A November 2017 1113170 Water Sr-89 pCi/L 57 .1 50 .0 39.4 - 57.5 A Sr-90 pCi/L 27 .1 41.8 30 .8 - 48 .0 N (2)

(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 Accepta ble - Reported value falls outside of the Acceptance Limits (1) See NCR 17-09 (page B-2)

(2) See NCR 17-19 (page B-3)

B-9

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Operating Report 2017 Millstone Power Station APPENDIX C ERRATUM C-1

Domin ion Nuclear Co nnecticut , Inc. Annu al Ra dio logica l Environmenta l Op era t ing Report 20 17 M ill ston e Power Stat ion Erratum- Correction to the 2016 Annual Radiological Environmental Operating Report Replace entire Section 4.10 of the 2016 report with the following :

4.10 Seawater (Table 10)

The guidance in Reference 15 specifies one sample upstream (control - beyond significant influence of the discharge) and one sample downstream (indicator - beyond but near the mixing zone) for surface water samples. Historically the downstream sample for MPS has been located in the vicinity of discharge (Location 32) which is prior to the mixing zone. This location was chosen since it was readily accessible and not affected by cold weather conditions. Operation of an automatic sampler at the indicator location is necessary for providing a representative sample. Any dose consequences can be assessed by use of the appropriate dilution factors . It's not necessary to have a continuous sampler at the control location due to the historical relative consistency noted in seawater background activity near the Millstone.

A technician collects an aliquot from the automatic sampler at Location 32 on a weekly frequency.

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

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

Measured station related levels of H-3 inseawater 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 . Between 1992 and 2002, H-3 was not typically detected. However, due to the enhanced detection sensitivity, H-3 levels are now often detected at the indicator location.

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 . The high REMP sample results during the second quarter of 2016 occurred during the MPS3 outage when circulating water pumps were turned off. Tritium concentrations in the MPS Quarry were elevated because of less dilution flow during that period. Increase in dose during the time of higher tritium concentrations was not significant. The table below shows quarterly doses from release of radioactivity in liquid effluents from MPS3 during 2016.

MPS3 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Annual Total Max Individual (mrem) (mrem) (mrem) (m rem) (mrem)

Whole Body 2.65E-04 5.26E-04 3.17E-04 2.46E-04 1.35E-03 Thyroid 2.12E-04 4.77E-04 6.40E-05 2.46E-04 9.99E-04 1

Max Organ 4.73E-04 6.11E-04 1.68E-03 2.46E-04 2.37E-03 Whole body and thyroid doses were higher in the second quarter than the other three quarters by factors of about two to eight. Max organ dose in the second quarter was lower than the third quarter dose by a factor of about three and higher than the doses in the other two quarters by factors of 1.3 and 2.5. Despite an increase in dose for eight of nine doses in other quarters the second quarter increase was still a small fraction of the quarterly dose limits.

C-2

Dominion Nuclear Connecticut, Inc. Annual Radiological Environmental Op erating Report 2017 Millstone Power Station The quarterly dose limits are 1.5 mrem for whole body and 5 mrem for any organ , including the thyroid .

Whole body dose in the second quarter was less than 0.04% of the limit, thyroid dose in the second quarter was less than 0.01 % of the limit and max organ dose in the second quarter was less than 0.02%

of the limit Figure 4.10-1 H-3 Curies Released versus Seawater Concentration 18 Year Trend 1600 pCi/l iter 2450 pCi/liter 1200 1100

- - curies discharged I

1000 I

- - REMP pCi/liter 900

I 800

,I"

\

I 700 '

I A I I

\ ~

, ' ~*'

600 I

,A,

.... 1 I I v*;~

500 1\ ~ t * ~

I. V 400

\J

~ 1

\ \ t\ I\ V \ JA 300 200

. vi J\ ~ v !} ~ ,/\J ¥

~ ~ ..,

V' *

'/ V .~ *

~ ~ ~

100 0

§

' 8 g

I N

0 g

0

~

\;

\

0 g -§ -a... M g

co g

§

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 occu rring nuclides of Be-7, K-40, and Ac-228 were detected in some samples. Be-7 is from cosm ic 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 alm ost every other type of sample. Ac-228 was observed in one sediment and two soil samples. Cs-137 and Sr-90 from atmospheric nuclear weapons testing in the 1960's 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 2016, Cs-137 was detected in one soil sample and Sr-90 was not detected .

C-3

Dominion Nuclear Connecticut, Inc. Annua l Radiological Environmental Operating Report 2017 Millstone Power Station 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 CaS04(Tm) Panasonic model UD-804 ASx TLDs. Readings are recorded as uR/hr. The unit uR 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, and six in 2016. None were loaded in 2008, from 2011 , and 2014 . The exposure rate measurements at two of the three additional TLD locations remain basically unchanged from the background measurements performed prior to any cask loading (six quarter background average mid 2003 - 2004:

9.5 uR/hour at Location 73, 7.5 uR/hour at Location 74 and 6.9 uR/hour at Location 75). At Location 73 the read ings have been lower since the fourth quarter of 2012, averaging 7.7 µR/hr.

C-4

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