Text

2020 Annual Radiological Environmental Operating Report
	ML21133A495
Person / Time
Site:	Monticello
Issue date:	05/13/2021
From:	Conboy T; Xcel Energy
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	L -MT-21-032
	Download: ML21133A495 (86)
	v • d • e

~ Xcel Energy 2807 West County Road 75 Monticello, MN 55362 5/13/2021 L.. MT-21-032 10 CFR 50, Appendix I ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 2020 Annual Radiological Environmental Operating Report Pursuant to 10 CFR 50, Appendix I, Section IV.B.2, IV.B.3, IV.C and, in accordance with Monticello Nuclear Generating Plant (MNGP) Technical Specifications 5.6.1, the Northern States Power Company, a Minnesota corporation (NSPM), d/b/a Xcel Energy, is submitting the Annual Radiological Environmental Operating Report, under MNGP's "Radiological Environmental Monitoring Program," for year 2020.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

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Thomas A. Conboy Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region 111, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC Minnesota Department of Commerce

ENCLOSURE RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM JANUARY 1 - DECEMBER 31, 2020

ARCADIS I Design&Consultancy fornatural and built assets (l Xcel Energy RESPONSIBLE BY NATURE 2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT (AREOR)

Monticello Nuclear Generating Plant Last Updated: 5/10/2021

2020 ANNUAL RADIOLOGICAL

______________________________ ENVIRONMENTAL Dale Brokaw, EIT Environmental Engineer OPERATING REPORT Monticello Nuclear Generating Plant Prepared for:

Xcel Energy, Inc.

Michael Hay, PhD Prepared by:

Principal Scientist Arcadis US, Inc.

Quality Assurance Reviewer 630 Plaza Drive Suite 200 Highlands Ranch Colorado 80129 Our Ref.:

30041924 Eric Cowan Quality Assurance Reviewer Date: 5/10/2021 Jesse Toepfer, Toepfer PhD, PhD PE, PE PMP, PM RSO Program Manager arcadis.com

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT CONTENTS Acryonyms and abbreviations ....................................................................................................................... v References .................................................................................................................................................. vii Executive Summary ................................................................................................................................. ES-1 Summary of Activities and Results ................................................................................................... ES-1 1 Introduction ............................................................................................................................................. 2 1.1 Site Description and Sample Locations ........................................................................................ 4 1.1.1 Site Description .................................................................................................................. 4 1.1.2 Rationale for Sample Locations ......................................................................................... 4 1.2 Scope and Requirements of the REMP ........................................................................................ 4 2 Radiological Environmental Sampling Program Requirements .............................................................. 6 2.1 Exposure Pathway and Sample Locations ................................................................................... 6 2.2 Maps of Sample Locations .......................................................................................................... 14 3 Statistical and Calculational Methodology ............................................................................................ 19 3.1 Trend Identification ...................................................................................................................... 19 3.2 Estimation of the Mean Value ..................................................................................................... 19 3.3 Lower Limit of Detection and Minimum Detectable Concentration ............................................. 20 3.4 Reporting Levels and Lower Limits of Detection for Radioactivity .............................................. 20 4 Interpretation of Results ........................................................................................................................ 25 4.1 Airborne Radioiodine and Particulates ........................................................................................ 25 4.2 Drinking Water ............................................................................................................................. 27 4.3 River Water ................................................................................................................................. 27 4.4 Groundwater ................................................................................................................................ 27 4.5 Broadleaf Vegetation ................................................................................................................... 27 4.6 Food Products ............................................................................................................................. 28 4.7 Fish .............................................................................................................................................. 28 4.8 Shoreline Sediment ..................................................................................................................... 29 4.9 Direct Gamma Radiation ............................................................................................................. 30 4.9.1 Environmental TLD .......................................................................................................... 30 4.9.2 ISFSI TLD ........................................................................................................................ 31 arcadis.com i

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 5 Land Use Census.................................................................................................................................. 32 5.1 Purpose ....................................................................................................................................... 32 5.2 Methodology ................................................................................................................................ 33 5.3 2020 Land Use Census ............................................................................................................... 33 6 Quality Assurance ................................................................................................................................. 36 6.1 Sample Collection ....................................................................................................................... 36 6.2 Sample Analysis .......................................................................................................................... 36 6.3 Dosimetry Analysis ...................................................................................................................... 36 6.4 Laboratory Equipment Quality Assurance .................................................................................. 36 6.4.1 Daily Quality Control ........................................................................................................ 36 6.4.2 Calibration Verification ..................................................................................................... 36 6.5 General Engineering Laboratory, LLC ........................................................................................ 37 6.6 Environmental Dosimetry Company............................................................................................ 37 7 Environmental Sampling Modifications ................................................................................................. 38 7.1 Program Modifications ................................................................................................................ 38 7.2 Change of Sampling Procedures ................................................................................................ 38 7.3 Change of Analysis Procedures .................................................................................................. 38 7.4 Sample Deviations and Unavailable Analyses ............................................................................ 39 7.5 Analytical Deviations ................................................................................................................... 40 8 Radiological Environmental Monitoring Program - Summary of Results ............................................. 41 8.1 Radiological Environmental Monitoring Program Data Summary ............................................... 41 9 Errata to Previous Reports .................................................................................................................... 46 9.1 Errata to the MNGP AREOR ....................................................................................................... 46 10 Radiological Environmental Monitoring Program Results .................................................................... 47 10.1 Detection of activity ..................................................................................................................... 48 arcadis.com ii

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT TABLES Table 2.1-1: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Airborne (ODCM 07.01 Table 1) ........................................................ 6 Table 2.1-2: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Direct Radiation (ODCM 07.01 Table 1) ............................................ 7 Table 2.1-3: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Waterborne (ODCM 07.01 Table 1) ................................................... 8 Table 2.1-4: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Ingestion (ODCM 07.01 Table 1) ....................................................... 9 Table 2.1-5: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis (ODCM 07.01 Table 4) ...................................................................... 10 Table 3.4-1: Reporting Levels for Radioactivity Concentration in Environmental Samples ........................ 21 Table 3.4-2: Maximum Values for the Lower Limits of Detection (LLD) ...................................................... 22 Table 3.4-3: Analysis and Frequency of Samples ....................................................................................... 23 Table 5.3-1: Changes in Land Use Census from 2019 to 2020 .................................................................. 35 Table 5.3-2: Summary of Highest Location for each pathway in 2020 ....................................................... 35 Table 7.4-1: Sample Deviations and Unavailable Analysis ......................................................................... 39 Table 7.5-1: Analytical Deviations for Lanthanum-140 ............................................................................... 40 Table 8.1-1: Radiological Environmental Monitoring Program Summary ................................................... 42 DATA TABLES Airborne Cartridge: Radioiodine .................................................................................................................. 49 Airborne Particulates: Gross Beta ............................................................................................................... 51 Airborne Particulates: Gamma Isotopic ....................................................................................................... 52 Sediment: Gamma Isotopic ......................................................................................................................... 57 Tissue - Fish: Gamma Isotopic ................................................................................................................... 59 Tissue - Plant: Gamma Isotopic ................................................................................................................. 60 Water: Tritium .............................................................................................................................................. 61 Water - Drinking: Gross Beta ...................................................................................................................... 62 Water - Drinking: Iodine-131 ....................................................................................................................... 63 Water - Groundwater: Gamma Isotopic ...................................................................................................... 64 Water - Drinking: Gamma Isotopic ............................................................................................................. 68 arcadis.com iii

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Water - Surface: Gamma Isotopic .............................................................................................................. 69 Direct Radiation - TLD: Gamma ................................................................................................................. 72 Direct Radiation - ISFSI: Gamma ............................................................................................................... 74 FIGURES Figure 1.0-1: Monitored Potential Exposure Pathways ................................................................................. 3 Figure 2.2-1: Radiation Environmental Monitoring Program (ODCM 07.01 Figure 1) ................................ 14 Figure 2.2-2: 4 - 5 Mile Ring and Special Interest TLD Locations (ODCM 07.01 Figure 2) ....................... 15 Figure 2.2-3: Site Boundary TLD Locations (ODCM 07.01 Figure 3) ......................................................... 16 Figure 2.2-4: Control Locations (ODCM 07.01 Figure 4) ............................................................................ 17 Figure 2.2-5: ISFSI TLD Locations (ODCM 07.01 Figure 5) ....................................................................... 18 Figure 4.1-1: Graph of Historical Airborne Particulate Gross Beta ............................................................. 25 Figure 4.1-2: Graph of 2020 Average Airborne Particulate Gross Beta for Indicator and Control Locations ............................................................................................................................................... 26 Figure 4.2-1: Graph of Historical Gross Beta for Drinking Water Sample ................................................... 27 Figure 4.8-1: Graph of Historical Cesium-137 in River Sediment ............................................................... 29 Figure 4.9.1-1: Graph of Direct Gamma Radiation Measurements............................................................. 30 Figure 4.9.1-2: Graph of Historical Direct Gamma Measurements ............................................................. 31 EQUATIONS Equation 1 ................................................................................................................................................... 19 APPENDICES Appendix A GEL Laboratories, LLC 2020 Annual Quality Assurance Report Appendix B Environmental Dosimetry Company, Annual Quality Assurance Status Report, January -

December 2020 arcadis.com iv

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT ACRYONYMS AND ABBREVIATIONS AREOR Annual Radiological Environmental Operating Report BTP Radiological Assessment Branch Technical Position, Rev. 1, on Radiological Monitoring CFR Code of Federal Regulations d/b/a doing business as D/Q deposition coefficient E East EDC Environmental Dosimetry Company ENE East-Northeast ESE East-Southeast ft feet ft2 square feet GEL General Engineering Laboratories LLC GPS Global Positioning System ISFSI Independent Spent Fuel Storage Installation LLD lower limit of detection MDA minimum detectable activity mi mile MNGP Monticello Nuclear Generating Plant MOC Management of Change mrem millirem MWe megawatt electric N North NE Northeast NIST National Institute of Standards and Technology NNE North-Northeast NNW North-Northwest NRC Nuclear Regulatory Commission NW Northwest OCA owner-controlled area arcadis.com v

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT ODCM Offsite Dose Calculation Manual pCi/g picocurie per gram pCi/L picocurie per liter pCi/kg picocurie per kilogram pCi/m3 picocurie per cubic meter REMP Radiological Environmental Monitoring Program S South SE Southeast SSE South-Southeast std quarter Standard quarter, 91 days SSW South-Southwest SW Southwest TLD thermoluminescent dosimeter UFSAR Updated Final Safety Analysis Report USB Universal Serial Bus W West WNW West-Northwest WSW West-Southwest arcadis.com vi

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT REFERENCES Arnold, J.R., and H.A. Al-Salih. 1955. Beryllium-7 Produced by Cosmic Rays. Science. April 121(3144):

451-453.

MNGP Chemistry Manual, Procedure I.05.41, Annual Land Use Census and Critical Receptor Identification.

NRC Generic Letter 79-65 Radiological Environmental Monitoring Program Requirements Enclosing Branch Technical Position (BTP), Revision 1, November 1979.

NUREG 1302 Offsite Dose Calculation Manual Guidance: Standard Radiological Effluent Controls for Boiling Water Reactors, April 1991 Offsite Dose Calculation Manual (ODCM) 07.01 Monticello Nuclear Generating Plant, Revision 26.

Regulatory Guide 4.15 Quality Assurance for Radiological Monitoring Programs, Revision 1, 1979.

arcadis.com vii

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT EXECUTIVE

SUMMARY

This 2020 Annual Radiological Environmental Operating Report (AREOR) describes the Monticello Nuclear Generating Plant (MNGP) Radiological Environmental Monitoring Program (REMP) and program results for the 2020 calendar year1. MNGP is operated by Northern States Power Company, a Minnesota corporation, d/b/a Xcel Energy (Xcel) under a license granted by the U.S. Nuclear Regulatory Commission (NRC).

Provisions of NRCs NUREG-1302, NRC Generic Letter 79-65 Branch Technical Position, MNGP Technical Specifications, and MNGPs Offsite Dose Calculation Manual (ODCM) establish the requirements of the REMP. This AREOR describes the purpose and scope of MNGPs REMP, along with the monitoring and sampling results for the reporting period.

AREOR Contents This AREOR includes the following:

x Identification of sampling locations x Descriptions of environmental sampling and analysis procedures x Comparisons of present environmental radioactivity levels and historical environmental data x Analyses of trends in environmental radiological data as potentially affected by MNGP operations x A summary of environmental radiological sampling results Photo Credit: Daniel Thurston, Chemistry Supervisor, MNGP x Quality assurance practices, sampling deviations, unavailable samples, and program changes Plant Stack, used for dispersing treated gaseous effluents, Monticello Nuclear Generating Plant in Winter Summary of Activities and Results Sampling activities were conducted as prescribed by MNGPs ODCM. Required analyses were performed and detection capabilities were met for the collected samples required by the ODCM. To compile data for this AREOR, 844 samples were analyzed, yielding 1,961 test results. Based on the annual MNGP Land Use Census, the current number of sampling sites for MNGP is sufficient. Concentrations observed in the environment in 2020 for MNGP-related radionuclides were within the ranges of concentrations observed in the past. The continued operation of MNGP has not contributed measurable radiation to the environment.

1 Some of the composite samples corresponding to Quarter 4 and December 2020 extended to January 4th 2021.

ES-1

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 1 INTRODUCTION Photo Credit: Daniel Thurston, Chemistry Supervisor, MNGP Welcome to Monticello Nuclear Generating Plant The Radiological Environmental Monitoring Program (REMP) for the Monticello Nuclear Generating Plant (MNGP),2 located in Monticello, Minnesota, provides data on measurable levels of radiation and radioactive materials in the area surrounding the Site3 and evaluates the relationship between quantities of radioactive materials released from MNGP and the resultant doses to individuals from principal pathways of exposure.

At any given nuclear utility in the United States, REMPs are designed to provide a check on a nuclear utilitys Effluent Release Program4 and dispersion modeling to ensure that radioactive effluent concentrations in the air, terrestrial, and aquatic environments conform to the As Low As Reasonably Achievable (ALARA) design objectives of Appendix I of Chapter 10 of the Code of Federal Regulations (CFR) Part 50.

This 2020 Annual Radiological Environmental Operating Report (AREOR) has been prepared by Arcadis U.S., Inc. and presents a summary of the environmental data from exposure pathways, interpretations of that data, along with analyses and trends of the results covering the 2020 calendar year5.

2 In this document, a distinction is made between MNGP, Site, and Plant. MNGP is the name of the facility. Site refers to the entire areal extent of MNGPs property, including the uncontrolled and controlled areas. Plant refers to the controlled area. The REMP involves monitoring and sampling at various locations across the Site and offsite locations.

3 Referred to as the Site environs.

4 The Effluent Release Program is separate but related to the REMP. Both are required by federal regulations.

5 Some of the composite samples corresponding to Quarter 4 and December 2020 extended to January 4 th 2021.

2

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Figure 1.0-16 below illustrates various exposure pathways7 for receptors.8 Routinely monitored pathways include ingestion, inhalation, and direct radiation. Exposure pathways are based on Site-specific information, such as the locations and habitats of receptors, the ages of those receptors, and the distance and relationship of those receptors with respect to release points and water usage around MNGP. A Site-specific REMP has been developed and maintained in accordance with MNGPs Offsite Dose Calculation Manual (ODCM), NUREG-1302, and the Branch Technical Position on Radiological Environmental Monitoring.

Livestock Products

~ Direct Rad_iation Radionuchdes .

Behavior o f Radionuchdes Figure 1.0-1 Monitored Potential Exposure Pathways.

7 An exposure pathway describes the route of the radiological exposure from a source. The primary radiological emissions from the Site are airborne discharges. The following pathways are monitored as part of MNGPs REMP: external dose, ingestion of radioactive material, and inhalation of radioactive material.

8 Living things that can be affected by radioactive effluent releases are referred to as environmental receptors.

3

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 1.1 Site Description and Sample Locations 1.1.1 Site Description Located in Wright County, Minnesota, MNGP is located along the Mississippi River and is about 40 miles northwest of the Twin Cities of Minneapolis and St. Paul. MNGP generates commercial electrical power via a boiling water reactor with a nominal generating capacity of 681 megawatts electric (MWe). Commercial production was initiated on June 30, 1971.

1.1.2 Rationale for Sample Locations The REMP was established to assess the exposure pathways to humans. Specific methods and different environmental media are required to assess each pathway. Sampling locations for the Site are chosen based upon meteorological factors, preoperational monitoring, and results of the land use surveys. A number of sample points are selected as control locations because they are distant enough to preclude any MNGP effect, and thus, unaffected by Site operations. MNGPs REMP sampling locations and the TLD monitoring locations are discussed in Section 2 of this AREOR.

1.2 Scope and Requirements of the REMP MNGPs REMP is based on U.S. Nuclear Regulatory Commission (NRC) guidance, is conducted in accordance with MNGPs ODCM, and is furthermore guided by applicable procedures for sample media, sampling locations, sampling frequency, and analytical sensitivity requirements. Indicator and control locations were established for comparison purposes to distinguish radioactivity originating from the Plant versus that from natural or other anthropogenic9 sources. This program provides for surveillance of appropriate critical exposure pathways to man, protects vital interests of members of the public, and is intended to satisfy compliance with state and federal environmental agencies. Section 3 lists the reporting levels and sample collection frequency for detection of radioactivity in the environment.

9 An anthropogenic source refers to radioactivity from a manmade substance, as well as radioactivity from natural sources that would not otherwise normally be present in the environment either in an amount, concentration, and/or at a specified rate, without human intervention.

4

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Photo Credit: Daniel Thurston, Chemistry Supervisor, MNGP Blooming Trees at Monticello Nuclear Generating Plant The Annual Land Use Census, required by MNGPs ODCM, is performed to ensure changes in the use of areas at or beyond the Site boundary are identified and that appropriate modifications to the REMP are made if necessary. This census satisfies the requirements of Section IV.B.3 of Appendix I to 10 CFR 50.

Results are described in Section 5 of this document.

In addition, participation in an interlaboratory comparison program is performed in fulfillment of MNGPs ODCM operational requirements. The comparison program provides for independent checks on the precision and accuracy of measurements of radioactive material in REMP sample matrices. These checks are performed as part of the quality assurance (QA) program for environmental monitoring to demonstrate that the results are valid for the purposes of Section IV.B.2 of Appendix I to 10 CFR Part 50 and Regulatory Guide 4.15 Quality Assurance for Radiological Environmental Monitoring Programs. Appendix A of this 2020 AREOR summarizes the results obtained as part of this comparison program.

5

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 2 RADIOLOGICAL ENVIRONMENTAL SAMPLING PROGRAM REQUIREMENTS Figures 2.2-1 through 2.2-5 depict MNGPs REMP sampling locations and the TLD monitoring locations.

The location numbers shown on these maps correspond to those listed in Tables 2.1-2 through 2.1-4.

Guidance for the format and layout of these tables and figures is derived from MNGPs ODCM.

2.1 Exposure Pathway and Sample Locations Table 2.1-1 below presents the sample frequency and collection, analysis type, and number of samples versus their locations for airborne radioiodine and particulates.

Table 2.1-1: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Airborne (ODCM 07.01 Table 1)

Exposure Pathway Number of Samples and Sample Sampling and Type and Frequency of and/or Sample Locations** Collection Frequency Analysis

1. Airborne Samples from five locations: Continuous sampler Radioiodine analysis Weekly Radioiodine & three samples from offsite locations operation with sample for I-131 Particulates (in different sectors) of the highest collection weekly.

calculated annual average ground Particulate:

level D/Q, one sample from the Gross beta activity on each vicinity of a community having the filter weekly* Analysis highest calculated annual average SHALL be performed more ground-level D/Q, and one sample than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following filter from a control location specified in change.

Table 2.1-5. Perform gamma isotopic analysis on composite (by location) sample quarterly.

Notes:

If gross beta activity in any indication sample exceeds 10 times the yearly average of the control sample, a gamma isotopic analysis is required.

- Sample locations are further described in Table 2.1-5.

6

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-2 below presents the sample frequency and collection, analysis type, and number of samples versus their locations for direct radiation.

Table 2.1-2: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Direct Radiation (ODCM 07.01 Table 1)

Exposure Pathway Number of Samples and Sample Sampling and Type and Frequency of and/or Sample Locations** Collection Frequency Analysis

2. Direct Radiation 40 TLD stations established with Quarterly Gamma/Neutron Dose duplicate dosimeters placed at the quarterly following locations:****

1. Using the 16 meteorological sectors as guidelines, an inner ring of stations in the general area of the site boundary is established and an outer ring of stations at a distance of 4 to 5 miles distance from the plant site is established.

Because of inaccessibility, two sectors in the inner ring are not covered.

2. Ten dosimeters are established at special interest areas and four control stations.

3. Three neutron and gamma dosimeter sets are located along the OCA fence. Additionally, three neutron dosimeters are stationed with special interest and inner ring TLDs and four neutron control dosimeters are stationed with the REMP control TLDs.

Notes:

- Sample locations are further described in Table 2.1-5.

- - - Three control TLD locations have only one dosimeter.

7

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-3 below presents the sample frequency and collection, analysis type, and number of samples versus their locations for waterborne pathways.

Table 2.1-3: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Waterborne (ODCM 07.01 Table 1)

Exposure Pathway Number of Samples and Sampling and Type and Frequency of and/or Sample Sample Locations** Collection Frequency Analysis

3. Waterborne

a. Surface Water Upstream and downstream Monthly composite of Gamma Isotopic analysis of each locations weekly samples (water monthly composite and ice conditions permitting) Tritium analysis of quarterly composites of monthly composites

b. Groundwater Three samples from wells Quarterly Gamma Isotopic and tritium within 5 miles of the MNGP analyses of each sample and one sample from a well greater than 10 miles from the MNGP

c. Drinking One sample from the City of Composite of 2 weekly I-131 analysis on each bi-weekly Water Minneapolis water supply samples when I-131 composite when the dose analysis is performed; calculated for the consumption of monthly composite of the water is greater than weekly samples 1 millirem (mrem) per year#

otherwise Composite for gross beta and gamma isotopic analyses monthly Composite for tritium analysis quarterly

d. Sediment from One sample upstream of the Semiannually Gamma isotopic analysis of each Shoreline MNGP, one sample sample downstream of the MNGP, and one sample from the shoreline of the recreational area Notes:

The dose shall be calculated for the maximum organ and age group, using the methodology and parameters in the ODCM.

- Sample locations are further described in Table 2.1-5.

8

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-4 below presents the sample frequency and collection, analysis type, and number of samples versus their locations for ingestion pathways.

Table 2.1-4: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis: Ingestion (ODCM 07.01 Table 1)

Sampling and Exposure Pathway Number of Samples and Sample Collection Type and Frequency of and/or Sample Locations** Frequency Analysis

4. Ingestion

a. Milk Samples from milking animals in three Biweekly when Gamma Isotopic and Iodine-locations within 3 miles from the animals are on 131 analysis of each sample MNGP having the highest dose pasture; monthly potential; if there are none, then one at other times sample from milking animals in each of three areas between 3 to 5 miles from the MNGP where doses are calculated to be greater than 1 mrem per year#

One sample from milking animals at a control location, 10 to 20 miles from the MNGP and in the least prevalent wind direction

b. Vegetation Samples of vegetation grown closest to Monthly during Gamma Isotopic and Iodine-each of the two offsite locations of growing season 131 analysis of each sample highest predicted annual average D/Q if milk sampling is not performed, and one sample from 10 to 20 miles in the least prevalent wind direction

c. Fish One sample of one game species of Samples collected Gamma isotopic analysis on fish located upstream and downstream semi-annually each sample (edible portion of the MNGP only on fish)

d. Food Products One sample of corn and potatoes from At time of harvest Gamma isotopic analysis of any area that is irrigated by water in edible portion of each which liquid radioactive effluent has sample been discharged***

Notes:

- Sample locations are further described in Table 2.1-5.

- - As determined by methods outlined in Section 2.3 of the ODCM 07.01.

The dose shall be calculated for the maximum organ and age group, using the methodology and parameters in the ODCM.

9

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-5 below presents the location, code designation, and referenced collection site for a given sample type.

Table 2.1-5: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis (ODCM 07.01 Table 4)

Location Distance Compass Type of Sample Code Collection Site Miles Heading Sector River water M-8c Upstream of Plant within 1,000 ft upstream of Plant intake River water M-9 Downstream of Plant within 1,000 ft downstream of Plant discharge Drinking water M-14 City of Minneapolis 37.0 132 SE Groundwater M-43c Imholte Farm 12.3 313 NW Groundwater M-11 City of Monticello 3.3 127 SE Groundwater M-12 Plant Well No. 11 0.26 252 WSW Groundwater M-55 Hasbrouck Residence 1.60 255 WSW Sediment-River M-8c Upstream of Plant within 1,000 ft upstream of Plant intake Sediment-River M-9 Downstream of Plant within 1,000 ft downstream of Plant discharge Sediment-Shoreline M-15 Montissippi Park 1.27 114 ESE Fish M-8c Upstream of Plant within 1,000 ft upstream of Plant intake Fish M-9 Downstream of Plant within 1,000 ft downstream of Plant discharge Vegetation* M-41 Training Center Near 0.8 151 SSE Vegetation* M-42** Biology Station Road Near 0.7 136 SE M-42A** Near 0.7 108 ESE Vegetation* M-43c Imholte Farm Near 12.3 313 NW Cultivated Crops (corn)*** - -

(potatoes)*** - -

Notes:

Actual location for vegetation sampling may vary depending on availability of broad leaf plant species. The nearest available broad leaf specimens to the location should be used.

- M-42 is the preferred sampling location; however, M-42A may be used in place of M-42, if samples are not available at the preferred location.

- - Collected only if Plant discharges radioactive effluent into the river, then only from river irrigated fields. (See Section 2.1 of the ODCM 07.01)

Code letters are defined below:

A = Locations in the general area of the site boundary c = Locations of control samples (used for control air sampler and water control sample) 10

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-5: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis (ODCM 07.01 Table 4) (Continued)

Location Distance Compass Type of Sample Code Collection Site Miles Heading Sector Particulates and Radioiodine (air) M-1c Air Station M-1 11.0 307 NW (air) M-2 Air Station M-2 0.8 140 SE (air) M-3 Air Station M-3 0.6 104 ESE (air) M-4 Air Station M-4 0.8 147 SSE (air) M-5 Air Station M-5 2.6 134 SE Direct Radiation Inner Ring - (general area of the site boundary)

(TLD) M01A Sherburne Ave. So. 0.75 353 N (TLD) M02A Sherburne Ave. So. 0.79 23 NNE (TLD) M03A Sherburne Ave. So. 1.29 56 NE (TLD) M04A Biology Station Rd. 0.5 92 E (TLD) M05A Biology Station Rd. 0.48 122 ESE (TLD) M06A Biology Station Rd. 0.54 138 SE (TLD) M07A Parking Lot H 0.43 157 SSE (TLD) M08A Parking Lot F 0.45 175 S (TLD) M09A County Road 75 0.38 206 SSW (TLD) M10A & ISFSI- County Road 75 0.38 224 SW 15 (neutron)

(TLD) M11A County Road 75 0.4 237 WSW (TLD) M12A & ISFSI- County Road 75 0.5 262 W 14 (neutron)

(TLD) M13A North Boundary Rd. 0.89 322 NW (TLD) M14A North Boundary Rd. 0.78 335 NNW Notes:

Code letters are defined below:

A = Locations in the general area of the site boundary C = Locations of control samples (used for control air sampler and water control sample) 11

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-5: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis (ODCM 07.01 Table 4) (Continued)

Location Distance Compass Type of Sample Code Collection Site Miles Heading Sector Direct Radiation Outer Ring - (about 4 to 5 miles distant from the Plant)

(TLD) M01B 117th Street 4.65 1 N (TLD) M02B County Road 11 4.4 18 NNE (TLD) M03B County Rd. 73 & 81 4.3 51 NE (TLD) M04B County Rd. 73 (196th Street) 4.2 67 ENE (TLD) M05B City of Big Lake 4.3 89 E (TLD) M06B County Rd 14 &

4.3 117 ESE 196th Street (TLD) M07B Monticello Industrial Dr. 4.3 136 SE (TLD) M08B Residence Hwy 25 &

4.6 162 SSE Davidson Ave (TLD) M09B Weinand Farm 4.7 178 S (TLD) M10B Reisewitz Farm - Acacia Ave 4.2 204 SSW (TLD) M11B Vanlith Farm - 97th Ave 4.0 228 SW (TLD) M12B Lake Maria St. Park 4.2 254 WSW (TLD) M13B Bridgewater Sta. 4.1 270 W (TLD) M14B Anderson Res. - Cty Rd 111 4.3 289 WNW (TLD) M15B Red Oak Wild Bird Farm 4.3 309 NW (TLD) M16B University Ave and Hancock 4.4 341 NNW St, Becker Notes:

Code letters are defined below:

B = Locations about 4 to 5 miles distant from MNGP 12

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 2.1-5: Monticello Nuclear Generating Plant Radiological Environmental Monitoring Program Sample Collection and Analysis (ODCM 07.01 Table 4) (Continued)

Location Distance Compass Type of Sample Code Collection Site Miles Heading Sector Direct Radiation - (special interest locations)

(TLD) M01S 127th Street NE 0.66 241 WSW (TLD) M02S & ISFSI- Krone Residence 0.5 220 SW 16 (neutron)

(TLD) M03S Big Oaks Park 1.53 103 ESE (TLD) M04S Pinewood School 2.3 131 SE (TLD) M05S 20500 Co. Rd 11, 3.0 118 ESE Big Lake (TLD) M06S Monticello Public Works 2.6 134 SE (TLD) I-11 & ISFSI-11 OCA Fence South, on 0.31 222 SW (neutron) exit road (TLD) I-12 & ISFSI-12 OCA Fence Middle, on 0.32 230 SW (neutron) exit road (TLD) I-13 & ISFSI-13 OCA Fence North, on 0.34 240 WSW (neutron) exit road Direct Radiation Controls - (10 to 12 miles distant from Plant)

(TLD) M01C & Kirchenbauer Farm 11.5 323 NW Neutron Control D

(TLD) M02C & Cty Rd 4 & 15 11.2 47 NE Neutron Control C

(TLD) M03C & Cty Rd 19 & Jason Ave 11.6 130 SE Neutron Control A

(TLD) M04C & Maple Lake Water Tower 10.3 226 SW Neutron Control B

Notes:

Code letters are defined below:

A = Locations in the general area of the site boundary B = Locations about 4 to 5 miles distant from MNGP C = Locations of control samples (used for control air sampler and water control sample)

S = Special interest locations 13

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 2.2 Maps of Sample Locations Figure 2.2-1 below illustrates the sampling locations associated with surface water, well water, air, and vegetation.

Highest D/Q Garden Surface Water Sample

- Well Water Sample

- Air Sample

/ il\ ..._____..........._

- Sediment Sample 0' 1000' 2000' - Vegetation Sample N

I"'~::: '~ ~~,~~l~~----St

~----- -1 11 Figure 2.2-1: Radiation Environmental Monitoring Program (ODCM 07.01 Figure 1) 14

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Figure 2.2-2 below illustrates the locations of the 4- to 5-mile ring and special interest TLD monitoring stations.

Figure 2.2-2: 4 - 5 Mile Ring and Special Interest TLD Locations (ODCM 07.01 Figure 2) 15

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Figure 2.2-3 below illustrates the locations of site boundary TLD monitoring stations.

Figure 2.2-3: Site Boundary TLD Locations (ODCM 07.01 Figure 3) 16

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Figure 2.2-4 below illustrates the control sample locations.

Figure 2.2-4: Control Locations (ODCM 07.01 Figure 4) 17

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Figure 2.2-5 illustrates the ISFSI TLD locations.

1 N

GRADE ELEV.

liSFSl-16I

/(M02S)

Figure 2.2-5: ISFSI TLD Locations (ODCM 07.01 Figure 5) 18

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 3 STATISTICAL AND CALCULATIONAL METHODOLOGY 3.1 Trend Identification The REMP is not only intended to determine levels of radionuclides in the environment associated with MNGPs operations, but to evaluate trends in those levels over a period of time. If the data indicate a trend in the concentration of a radionuclide in an environmental medium, it could indicate that reactor operations are causing that particular radionuclide to fluctuate in the environment. Understanding effluent releases from MNGP is necessary to identify and interpret trends (or lack of trends) based on environmental data.

Factors that may affect environmental levels of radionuclides include prevailing weather conditions (e.g.,

periods of drought, solar cycles, and extreme precipitation events) and construction activities in close proximity to MNGP of a given sampling location.10 Some of these factors may be obvious, such as, the increase of airborne particulate beryllium-7 concentration due to atmospheric mixing or increase of surface water tritium due to atmospheric deposition from heavy precipitation events, while others are sometimes unknown.

3.2 Estimation of the Mean Value A widely used statistical calculation was performed on the raw data collected under the sample analysis program. The calculation involved determining the mean value for the indicator and control samples for each sample medium. The mean value was used in the reduction of the data generated by the sampling and analysis of the various media in the REMP. Net activity (or concentration)" is the activity (or concentration) determined to be present in the sample. No minimum detectable activity (or concentration),

lower limit of detection, less than level, or negative activities or concentrations are included in the calculation of the mean. Equation 1 below was used to calculate the estimated mean. The estimated mean is equal to the sum of all the individual sample values, beginning with the first sample, divided by the total number of samples.

N x = xi i=1 N

(Equation 1)

Where:

x = estimate of the mean i = individual sample N = total number of samples with a net activity (or concentration) xi = net activity (or concentration) for sample i When mean values are proceeded by a "+/-" value in the text, the +/- value represents the standard deviation of the individual values used to estimate the mean.

10 Additionally, from time to time, the trends may be affected by statistical additions or exclusions of known sources of radioactive material. For instance, there is a measurable amount of radioactivity attributable to the 1986 Chernobyl accident and the 2011 Japan earthquake and tsunami, which triggered the Fukushima Dai-ichi Nuclear Power Plant incident. It is important to note whether these factors are being accounted for, as they affect radiological environmental measurements, even though they are not attributable to MNGP.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 3.3 Lower Limit of Detection and Minimum Detectable Concentration The lower limit of detection (LLD) and minimum detectable concentration (MDC) are used throughout the REMP and are defined as follows.

x LLD is defined in the ODCM as the smallest concentration of radioactive material in a sample that will yield a net count above the system background that will be detected with 95 percent probability; i.e.,

only a 5 percent probability of falsely concluding that a blank observation represents a real signal.

The LLD is an a priori (i.e., before the fact) measurement. The actual LLD is dependent upon the standard deviation of the background-counting rate, the counting efficiency, the sample size (mass or volume), the radiochemical yield, and the radioactive decay of the sample between sample collection and counting. The required LLDs for each sample medium and selected radionuclides are provided in the ODCM and listed in Table 3.4-2.

x MDC is the net counting rate (sample after subtraction of background) that must be surpassed before a sample is considered to contain a scientifically measurable amount of a radioactive material exceeding background amounts. The MDC is calculated using a sample background and may be thought of as an "actual" LLD for a particular sample measurement.

Certain gross counting measurements display a calculated negative value, indicating background is greater than sample activity. In these instances, it does not mean that radioactivity is removed from the environment. Instead, the measurement errors associated with the radiochemical analysis have fluctuated causing the background count rate to be greater than the sample count rate.

3.4 Reporting Levels and Lower Limits of Detection for Radioactivity Reporting levels and LLDs for activity found in environmental samples are listed in Table 3.4-1 and Table 3.4-2. Required REMP sample analyses and their frequencies are listed in Table 3.4-3.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 3.4-1: Reporting Levels for Radioactivity Concentration in Environmental Samples Airborne Vegetables Water Fish Milk Analysis Particulate or (pCi/kg, (pCi/L) (pCi/kg, wet) (pCi/L)

Gas (pCi/m3) wet)

Tritium (H-3) 20,000a Manganese-54 (Mn-54) 1,000 30,000 Iron-59 (Fe-59) 400 10,000 Cobalt-58 (Co-58) 1,000 30,000 Cobalt-60 (Co-60) 300 10,000 Zinc-65 (Zn-65) 300 20,000 Zirconium-95 and Niobium-95 400b (Zr-Nb-95)

Iodine-131 (I-131) 2c 0.9 3 100 Cesium-134 (Cs-134) 30 10 1,000 60 1,000 Cesium-137 (Cs-137) 50 20 2,000 70 2,000 Barium-140 and Lanthanum-140 200b 300b (Ba-La-140)

Notes:

a For drinking water samples. This is a 40 CFR Part 141 value. If no drinking water pathway exists, a value of 30,000 pCi/L may be used.

b Total for parent and daughter product.

c If no drinking water pathways exist, a value of 20 pCi/L may be used.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 3.4-2: Maximum Values for the Lower Limits of Detection (LLD)

Airborne Fish Food Water Milk Sediment Analysis Particulate or (pCi/kg, Products (pCi/l) (pCi/L) (pCi/kg, dry)

Gas (pCi/m3) wet) (pCi/kg, wet)

Gross beta 4 0.01 Tritium (H-3) 2000a Manganese-54 (Mn-54) 15 130 Iron-59 (Fe-59) 30 260 Cobalt-58 and Cobalt-60 15 130 (Co-58, 60)

Zinc-65 (Zn-65) 30 260 Zirconium-95 and 15b Niobium-95 (Zr-Nb-95)

Iodine-131 (I-131) 1c 0.07 1 60 Cesium-134 (Cs-134) 15 0.05 130 15 60 150 Cesium-137 (Cs-137) 18 0.06 150 18 80 180 Barium-140 and Lanthanum-140 15b 15b (Ba-La-140)

Notes:

a If no drinking water pathway exists, a value of 3000 pCi/L may be used.

b The specified LLD applies to the daughter nuclide of an equilibrium mixture of the parent and daughter nuclides.

Per the Radiological Assessment Branch Technical Position, the following values may be used for individual nuclide LLDs when equilibrium conditions are not met: 30 pCi/L for zirconium-95, 15 pCi/L for niobium-95, 60 pCi/L for barium-140, and 15 pCi/L for lanthanum-140.

c If no drinking water pathway exists, a value of 15 pCi/L may be used.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 3.4-3: Analysis and Frequency of Samples Pathway Airborne Particulate and Radioiodine Sample Location I I

M-1 Air Station M-1 M-2 Air Station M-2 Type Control I-131 W

W Gross Beta W

W Gamma Isotopic Q1 Q1 I Tritium Gamma Dose M-3 Air Station M-3 W W Q1 M-4 Air Station M-4 W W Q1 M-5 Air Station M-5 W W Q1 Direct Radiation M01C to M04C Control Q M01A to M14A Q M01B to M16B Q M01S to M06S Q I-11 to 1-13 Q Waterborne: River Water M-8c Upstream of MNGP Control M1 Q1 M-9 Downstream of MNGP M1 Q1 Waterborne: Groundwater M-43c Imholte Farm Control Q Q M-11 City of Monticello Q Q M-12 Plant Well No. 11 Q Q M-55 Hasbrouck Residence Q Q Waterborne: Drinking Water M-14 City of Minneapolis BW1,2 M1 M1 Q1 Waterborne: Sediment M-8c Upstream of Plant Control SA M-9 Downstream of Plant SA M-15 Montissippi Park SA Ingestion: Milk - M/BW3,4 M/BW3,4 Ingestion: Vegetation M-43c Imholte Farm Control M5 M5 M-41 Training Center M5 M5 M-42 Biology Station Road M5 M5 Ingestion: Fish M-8c Upstream of Plant Control SA M-9 Downstream of Plant SA Ingestion: Food Products - A3 23

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Notes for Table 3.4-3:

1 Composite of weekly samples.

2 Iodine-131 analysis included on each bi-weekly composite when the dose from the consumption of the water is greater than 1 mrem/year. (ODCM Revision 26) 3 This pathway is currently unavailable at MNGP.

4 Every two weeks when animals are on pasture; monthly at other times.

5 During growing season when milk samples are unavailable.

W = weekly BW = every two weeks M = monthly Q = quarterly SA = semi-annually A = annually 24

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 4 INTERPRETATION OF RESULTS 4.1 Airborne Radioiodine and Particulates The average annual gross beta11 concentrations in airborne particulates were similar at the indicator (0.040 +/-

0.013 pCi/m3 for 2020) and control locations (0.039 +/- 0.013 pCi/m3 for 2020). These 2020 results are comparable to levels observed from 2009 through 2019. The results are graphed below in Figure 4.1-1.

Airborne Particulate Annual Average Gross Beta Control Indicators 0.100 Annual Avg Gross Beta (pCi/m3) 0.090 0.080 0.070 0.060 0.050 0.040 0.030 0.020 0.010 0.000 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Years Figure 4.1-1: Graph of Historical Airborne Particulate Gross Beta 11 Gross beta is a measurement of all beta activity present, regardless of specific radionuclide source. Beta particles are physically identical to electrons, but are differentiated by their source (beta particles are created in the nucleus during certain types of nuclear transformations, whereas electrons come from the electron cloud surrounding the nucleus). Beta particles can have various states of energy.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Figure 4.1-2 shows the average indicator gross beta from the four indicator locations (Air Station locations M-2, M-3, M-4, M-5) versus the control location (Air Station M-1) in 2020. The error bar represents the statistical uncertainty, as 1.96 sigma (V) (95% confidence), associated with each measurement for a given sample collection date. Despite the variability of gross beta activity in airborne particulates, the average results from the indicator locations were similar to the results from the control location.

Airborne Particulate Gross Beta Control Indicator 0.1 0.09 0.08 0.07 Gross Beta (pCi/m 3) 0.06 0.05 0.04 0.03 0.02 0.01 0

Sample Collection Date Figure 4.1-2: Graph of 2020 Average Airborne Particulate Gross Beta for Indicator and Control Locations Mixing of the upper and lower atmospheres can transport suspended particles and beryllium-712 from the upper atmosphere to the lower atmosphere, which can increase the airborne particulate gross beta in the lower atmosphere. Gamma spectroscopic analysis of quarterly composites of air particulate filters yielded similar results for indicator and control locations. Beryllium-7 was detected in all samples, with an average activity of 0.075 +/- 0.011 pCi/m3 for the control locations, and 0.078 +/- 0.015 pCi/m3 for the indicator locations.

All other gamma-emitting isotopes were below their respective LLD limits.

The weekly levels of airborne radioiodine-131 were below the LLD for the airborne radioiodine cartridge samples analyzed. There was no indication of an emission of radioiodine from MNGP.

12 Beryllium-7 can be created in the upper atmosphere by cosmic radiation and solar flares (Arnold & Al-Salih, 1955).

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 4.2 Drinking Water Tritium activity was measured below the detection limit for all samples. Gamma isotopic results were all below detection limits. Gross beta results were all below detection limits. Gross beta averages are shown on Figure 4.2-1. There was no indication of an effect from MNGP.

Historical Drinking Water Gross Beta (pCi/L) 3.5 Annual Average Gross Beta (pCi/L) 3 2.5 2

1.5 1

0.5 0

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Year Figure 4.2-1: Graph of Historical Gross Beta for Drinking Water Sample 4.3 River Water River water was analyzed from samples both upstream and downstream of MNGP. Tritium activity was measured below the detection limit for all samples. The gamma isotopic results were all below detection limits.

4.4 Groundwater Tritium and gamma isotopic results were below the detection limit for all samples taken. The data for 2020 were consistent with the previous years results and no MNGP operational effects were indicated.

4.5 Broadleaf Vegetation Vegetation samples were collected during the growing season of June, July, August, and September 2020.

Gamma isotopic and iodine-131 concentrations were measured below the detection limit in all samples.

These samples are required when milk samples are not available.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 4.6 Food Products Corn and potato samples were not required for 2020. There were no crops within five miles of MNGP irrigated using water from the Mississippi River, and MNGP did not discharge radioactive liquid effluents.

4.7 Fish Eight fish were analyzed in 2020, including two fish collected from upstream locations and two collected from downstream locations in May and then again in September. Two species of fish, shorthead redhorse and smallmouth bass, were collected from each location. Gamma spectroscopy was performed on the edible portion of the fish. Only potassium-40, which is a common radioisotope found in nature and would not be associated with MNGP activities, was found with an average of 3.23 +/- 0.06 pCi/g wet weight for four upstream samples and 3.17 +/- 0.08 pCi/g wet weight for the four downstream samples. These results are consistent with historical results. Other gamma-emitting isotopes remained below detection limits. There were no gamma emitting radionuclides attributable to MNGP operations identified in any of the 2020 fish samples.

Photo Credit: Darin Jensen, Senior Design Engineer, MNGP Canada Goose and Goslings Crossing Near an MNGP Radiological Environmental Sampling Point arcadis.com 28

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 4.8 Shoreline Sediment Shoreline sediments were collected from three locations: upstream, downstream, and downstream-recreational. Cesium-137 was detected in May at the upstream sample (M-8), with a concentration of 0.035

+/- 0.023 pCi/g dry weight. Similar levels of activity have been observed since 1996 (see Figure 4.8-1) and are indicative of the influence of fallout deposition from above ground nuclear weapons testing. Levels of cesium-137 in sediments are observed to fluctuate as silt distributions shift due to natural erosion and transport processes. Naturally occurring beryllium-7 and potassium-40 were also detected. There was no indication of a MNGP effect.

River Sediment Annual Average Cs-137

...,._M-8 (Control) - M-9 - M-15

.......... 0.50 0)

-:::: 0.45

(.)

a. 0.40

~ 0.35

~ 0.30 en

(.) 0.25

~0.20 C'O CD 0.15

<i: 0.10 C'O O. 05

i

§ 0.00

<( 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 Year Figure 4.8-1: Graph of Historical Cesium-137 in River Sediment arcadis.com 29

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 4.9 Direct Gamma Radiation 4.9.1 Environmental TLD Ambient radiation was measured in the general area of the Site boundary, at the inner ring, at an outer ring 4 to 5 miles (mi) from the Plant, at special interest areas, and at four control locations. On average, the quarterly TLD measurements (where one standard [std] quarter is a 91-day period) were similar for both inner and outer rings, at 14.3 and 13.9 millirem (mrem)/std quarter, respectively. The mean for special interest locations was 14.2 mrem/std quarter and the mean for the control locations was 13.2 mrem/std quarter. Figure 4.9.1-1 shows the average measured dose from each std quarter. The error bars represent the statistical uncertainty associated with each average measurement.

TLD Results 2020 (mrem/std quarter)

___.,._Control ~ Inner Ring - Outer Ring ~ Special Interest 20 18

~

2 16 B

"'~ 14

<J) 12 i i E

... 108 (I)

-S

6

~

4

t_

2 0

Mar Jun Sep Dec Sample Collection Date (2020)

Figure 4.9.1-1: Graph of Direct Gamma Radiation Measurements arcadis.com 30

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Dose rates measured at the inner and outer ring locations in 2020 were similar to those observed from 1999 through 2019 and are shown in Figure 4.9.1-2. No MNGP effect on ambient gamma radiation is indicated.

Annual Average Historical TLD (mrem/std quarter)

Annaul Average Activity (mrem/std 20 Control Inner Ring Outer Ring 18 16 14 12 10 quarter) 8 6

4 2

0 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Year Figure 4.9.1-2: Graph of Historical Direct Gamma Measurements 4.9.2 ISFSI TLD Gamma and Neutron TLDs are located around the Independent Spent Fuel Storage Installation (ISFSI) to monitor direct radiation from stored fuel for trending purposes. The ISFSI TLDs are not considered true REMP TLDs and are not representative of the dose to members of the public. Results for monitoring are included in Section 10.

No additional spent fuel casks were moved to the ISFSI in 2020. Annual data trends at and in the vicinity of the ISFSI are consistent with expectations. There were no detectable dose rate increases observed at the Site boundary TLDs in 2020.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 5 LAND USE CENSUS 5.1 Purpose The Land Use Census identifies the pathways (or routes) by which radioactive material may reach the general populations near commercial nuclear generating stations. This is accomplished by completing studies each year that identify how the surrounding lands are used by the population. A comprehensive census of the use of the land within a five-mile distance of the Plant is completed during the growing season each year. This information is used for dose assessment and to identify changes to the stations sampled and the type of samples. Therefore, the purpose of the Land Use Census is to ensure the REMP is current based on human activity near MNGP, as well as to provide data for the calculation of estimated radiation exposure.

Photo Credit: Darin Jensen, Senior Design Engineer, MNGP Woodchuck Near an MNGP Radiological Environmental Sampling Point.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT The pathways evaluated are:

x Ingestion Pathway - Results from eating food crops that may have radioactive materials deposited on them or may have taken up radioactive materials from the soil or atmosphere. Another potential pathway is through drinking milk or eating cheese from local cows or goats. The vegetation used to feed these animals may include radioactive material due to deposition or uptake from soil and the radioactivity transferred to the milk. If milk animals are not present, vegetation is collected in lieu of milk.

x Direct Radiation Exposure Pathway - Results from deposition of radioactive materials on the ground or from passage of these radioactive materials in the air.

x Inhalation Pathway - Results from breathing radioactive materials transported in the air.

5.2 Methodology The following must be identified within a five-mile radius of the Plant for each of the sixteen meteorological sectors (i.e., compass heading) for potential wind direction; for example, North-Northeast (NNE):

x The nearest resident x The nearest garden of greater than 500 square feet (ft2) producing broadleaf vegetables ("Garden")

x The nearest animal used for meat consumption ("Meat")

x The nearest milk-producing animal ("Milk")

The 2020 survey was performed using door-to-door surveys and visual observations while driving; additionally, inputs from the 2019 field data forms were used to evaluate changes to the land use. Google Earth Pro satellite imagery and the Homeland Security Emergency Management Monticello Basemap were used in determining changes in land use. Data were collected using a combination of the Spyglass App and Google Earth Pro, using a universal serial bus (USB) global positioning system (GPS) receiver. Google Earth Pro was used to determine receptor location distances and sectors; these results were used in determining dispersion parameters for dose calculations. Distance, direction, and dose pathway information is used to determine if any sampling locations need to be changed in the REMP sampling program and for determining Critical Receptor data.

5.3 2020 Land Use Census The 2020 Land Use Census was conducted between August 13 and August 20, 2020, by the REMP Coordinator in accordance with MNGPs Chemistry Manual, Procedure I.05.41, Annual Land Use Census and Critical Receptor Identification.

There were no sectors that had an increase in the nearest garden deposition coefficient (D/Q) of greater than 20 percent compared to 2019. The highest D/Q garden for 2020 remains in sector SSE at 1.20 miles from MNGP.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT There were three sectors where the highest D/Q value for the combined Meat and Garden increased by greater than 20 percent. The increase was due to finding these combined receptor pathways in 2020 that were not observed in 2019 (S, SW, and WNW). In addition, the combined pathways were not present in the three sectors (N, NE, and SSW) in which they were observed in 2019.

The highest D/Q Meat location is in the WSW sector, 1.78 miles from the Plant. The highest D/Q combined Meat/Garden location is in the W sector, 1.82 miles from the Plant.

Photo Credit: Gene Richter, Operator, Special Projects, MNGP There were no sectors in which the highest D/Q values for the nearest Deer Near an MNGP Radiological Environmental Sampling Point.

resident increased by more than 20 percent in 2020. The highest D/Q resident remains at 0.99 miles from the Plant in the SSE sector.

In 2019 a new Milk location was located 3.25 miles in the NNE sector. The animal is infrequently milked and only provides enough for the family usage. Due to the relativity low deposition, the calculated dose at this location is lower than the vegetation sample locations. Milk samples are required for three locations within 3 miles or three locations where doses are calculated to be greater than 1 mrem/year (ODCM 07.01).

The identified Milk animal is greater than 3 miles from the site, and the dose from all pathways at that location is 0.022 mrem/year to the infant thyroid. Thus, vegetation sampling was performed in lieu of milk sampling.

There are no crops being irrigated from the Mississippi River within five miles downstream of the Plant, based upon the most recent Water Use Resources Permit Index Report from the Minnesota Department of Natural Resources. The nearest downstream drinking water supplies drawn from the Mississippi River remain St. Paul and Minneapolis water supplies as currently documented in the ODCM and UFSAR.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 5.3-1 summarizes the locations showing greater than a 20 percent increase in D/Q as identified in the Land Use Census from 2019 to 2020. The locations identified in Table 5.3-1 do not necessarily represent the locations with the highest D/Q for a given pathway; rather, these are the locations with a greater than 20 percent increase in the D/Q of a pathway within a specific sector. The highest D/Q location for each pathway is described in Table 5.3-2.

Table 5.3-1: Changes in Land Use Census from 2019 to 2020 2019 Distance 2020 Distance Sector Pathway 2019 D/Q 2020 D/Q (mi) (mi)

S Meat + Garden - 4.40 - 1.9E-10 SW Meat + Garden - 3.40 - 2.30E-10 WNW Meat + Garden - 3.40 - 2.80E-10 N Meat + Garden 3.79 - 5.30E-10 -

NE Meat + Garden 3.44 - 1.40E-10 -

SSW Meat + Garden 2.77 - 4.10E-10 -

Table 5.3-2: Summary of Highest Location for Each Pathway in 2020 Pathway Sector Distance (mi) D/Q Resident SSE 0.99 1.40E-08 Meat WSW 1.78 9.60E-10 Meat + Garden W 1.82 6.90E-10 Garden SSE 1.21 6.70E-09 Milk1 NNE 3.24 3.90E-10 Crops - - -

Notes:

1 Vegetation performed in lieu of Milk sampling Doses due to ground plane, inhalation, and ingestion of vegetables and meat, were calculated for the highest D/Q Resident, Meat, Garden, and combined Meat and Garden locations identified in the 2020 Land Use Census. In accordance with the ODCM, the long- and short-duration gaseous releases from the Reactor Building Vent and the Off-gas Stack for the previous calendar year were used as the source terms.

Doses were calculated using the RADEAS computer program with the 2019 Annual Effluent Data report source term as input. This resulted in identifying the same sector, distance, and pathway as compared to last year's critical receptor. The location, comprising a residence with a garden, is 1.20 miles away from the Plant located in the SSE sector (designated GH). The pathway identified is the combination of ground plane, inhalation, and vegetable ingestion. For the purposes of compliance with 10 CFR 50 Appendix I, the critical receptor is defined as a child at this location with dose calculated to the thyroid. The dose for this receptor is estimated at 0.0335 mrem/year.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 6 QUALITY ASSURANCE 6.1 Sample Collection MNGP personnel performed the environmental sample collections as specified by approved sample collection procedures.

6.2 Sample Analysis General Engineering Laboratories, LLC (GEL) performed the environmental sample analyses as specified by approved analysis procedures. GEL is located in Charleston, South Carolina.

6.3 Dosimetry Analysis Environmental Dosimetry Company (EDC) works in conjunction with Stanford Dosimetry to perform the environmental dosimetry measurements as specified by approved dosimetry analysis procedures. The Environmental TLD program at the EDC provides Panasonic TLD badges containing calcium sulfate (CaSO4) phosphor elements for posting in the field. The raw TLD results are corrected for individual element sensitivity and reader sensitivity as determined by the quality control results. Control dosimeters are used to determine the background radiation exposure during the shipment and serve to evaluate transit exposures. The transit exposures are subtracted from the field dosimeters. Since the measured signal fades from the time of exposure to analysis, the fade of the thermoluminescent response is corrected.

6.4 Laboratory Equipment Quality Assurance 6.4.1 Daily Quality Control GEL has an internal QA program which monitors each type of instrumentation for reliability and accuracy.

Daily quality control checks ensure that instruments are in proper working order, and these checks are used to monitor instrument performance.

6.4.2 Calibration Verification National Institute of Standards and Technology (NIST) standards that represent counting geometries are analyzed as unknowns at various frequencies, ranging from weekly to annually, to verify that efficiency calibrations are valid. The frequency is dependent upon instrument use and performance. Investigations are performed and documented should calibration verification data fall outside of the acceptable limits.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 6.5 General Engineering Laboratory, LLC GEL participated in various QA programs for inter-laboratory, intra-laboratory, third party cross check programs, and a number of proficiency testing programs during 2020. A summary of the GEL QA program results for the sample media types sent to GEL during 2020 is documented in Appendix A.

6.6 Environmental Dosimetry Company EDC participates in an internal performance acceptance criteria and a quarterly independent testing TLD intercomparison program. In 2020, 100 percent of the individual dosimeters passed the performance criteria. A summary of the 2020 EDC Annual Quality Assurance Status Report is documented in Appendix B.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 7 ENVIRONMENTAL SAMPLING MODIFICATIONS 7.1 Program Modifications There were no programmatic changes to environmental sampling; however, the configuration of each of the REMP Air Sampling Units was modified following the September 2020 collection events. The existing sample holders were augmented with goosenecks to orient the sample heads toward the potential activity source to be more consistent with industry best practice. The modified Air Sampling Units were placed into service in conjunction with quarterly calibration in October 2020.

7.2 Change of Sampling Procedures There were no changes to sampling procedures in 2020.

7.3 Change of Analysis Procedures In 2018, samples were analyzed by Environmental, Inc. Midwest Laboratory. In 2019, the samples were analyzed by GEL. While the laboratory change did not impact the required LLDs, the actual MDC for some analytes, such as tritium and gross beta, could be different due to variations in natural background and analytical equipment.

In 2019, weekly drinking water and surface water samples were composited by GEL. In 2020, the weekly water samples were composited onsite and shipped to GEL monthly. While the compositing change did not impact the required LLDs, the actual MDC for some analytes, such as barium-140/lathanium-140, could be different due to changes in the sample times.

ODCM Revision 26 revised the drinking water sample requirement to make iodine-131 sampling consistent with NUREG-1302. This revision requires iodine-131 analysis to be performed when the dose calculated for the consumption of water is greater than 1 mrem per year. Otherwise, only a monthly drinking water composite analyzed for gross beta and gamma isotopic and a quarterly composite analyzed for tritium should be collected. As a result of this change, drinking water iodine-131 sampling ceased on February 27, 2020.

The standard operating procedures used by GEL are approved methods. Copies of GELs accreditations and certifications are available on their website, www.gel.com.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 7.4 Sample Deviations and Unavailable Analyses Table 7.4-1 lists the deviations from the required REMP sample collection in 2020. Despite these sample deviations, 99.6 percent of the required samples were successfully obtained and analyzed.

Table 7.4-1: Sample Deviations and Unavailable Analyses Reason for not Sample Collection Date Corrective Condition Analysis Location conducting REMP Type or Period Action Report as required Gamma Composite -

Unsafe condition Isotopic Gamma: Jan, Sample obtained Surface for sampling due to M-8C Feb, Mar 2020 when water 501000036207 Water river surface being Tritium and Tritium: 1st thawed frozen quarter1 TLD located along TLD for 1Q2021 Quarter 4 2020 CR 75 - West placed in TLD Direct TLD M-12A (Oct through Sector was missing holder and cap 501000047634 Radiation Dec 2020) from its assigned covers were TLD holder reaffixed Notes:

1 January and February samples could not be collected, but samples were collected in March. The quarterly composite for tritium therefore only includes March. Although condition report 501000036207 references the January event, subsequent events for which this condition applied were tracked under Management of Change (MOC) 603000004249.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 7.5 Analytical Deviations The ODCM 07.01 Table 3 LLD values for the parent-daughter isotopic pair barium-140/lanthanum-140 are 60 pCi/L and 15 pCi/L, respectively (see Table 3.4-2). Of the 50 groundwater, surface water, and drinking water samples collected in 2020, the LLD was not satisfied in two of the barium-140/lanthanum-140 samples (4%). In each sample, the MDC was higher than the LLD. The cause of the deviation was largely due to the time period between sample analysis and sample collection. GEL's Laboratory Information System (LIMS) outage at the end of June, coupled with short radiochemical half-life, caused the deviations.

Since barium-140 and lanthanum-140 half-lives of 12.75 days and 1.68 days, respectively, are shorter than the delay due to the outage, the required LLDs could not be met. See Table 7.5-1 for more details.

Table 7.5-1: Analytical Deviations Minimum ODCM 07.01 Detectible Collect Analysis Result Table 3 Location Isotope Concentration Cause Date/Time Date/Time (pCi/L) Required I I I I I I I (MDC)

LLD (pCi/L)

(pCi/L)

M-8 Upstream 5/27/2020 7/14/2020 La-140 -0.028 U 15 42.7 A of Plant 08:10 09:27 Ba-140 -36.8 U 60 177 A M-9 La-140 -13.7 U 15 47.2 A 5/27/2020 7/14/2020 Downstream of 08:25 10:47 Ba-140 -33.3 U 60 132 A Plant Cause Codes:

A= GEL's LIMS outage arcadis.com 40

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 8 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM -

SUMMARY

OF RESULTS This section presents a summary of MNGPs REMP sampling and monitoring results for the 2020 period for airborne particulates, airborne radioiodine, direct radiation, and measurable radioactivity in milk, broadleaf vegetation, river water, aquatic invertebrates, shoreline sediments, groundwater, drinking water, and fish. In all, there were no reported non-routine measurements.

8.1 Radiological Environmental Monitoring Program Data Summary Table 8.1-1 below presents the summary of MNGPs REMP sampling and monitoring results for the 2020 period.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Table 8.1-1: Radiological Environmental Monitoring Program Summary Name of Facility: Monticello Nuclear Generating Plant Docket No: 50-263 Location of Facility: Wright, Minnesota Reporting Period January - December 2020 Type, Control Location with Highest Annual Mean1 (f)2 Total Mean Number of ODCM Indicator Mean1; Analyses Table 3 Number of Medium or Pathway Sampled performed Lower Name Mean 1 Nonroutine (Units) Limit of Reported Detection Range1 Measurements (f)2 (f)2 (e.g. I-131, (LLD) Distance and 400) Direction Range 1 Range1 Airborne Particulates Gross Beta 0.01 0.040 (212/212) M-3, Air Station 0.040 (53/53) 0.039 (53/53) 0 (pCi/m3) (265) 0.012 - 0.085 0.6 m @ 104/ESE 0.021 - 0.085 0.018 - 0.082 Gamma 0 (20)

Be-7 3 - 0.078 (16/16) M-3, Air Station 0.083 (4/4) 0.075 (4/4) 0.056 - 0.104 0.6 m @ 104/ESE 0.062 - 0.104 0.063 - 0.089 Mn-54 - <LLD - - <LLD Co-58 - <LLD - - <LLD Co-60 - <LLD - - <LLD Zn-65 - <LLD - - <LLD Zr-Nb-95 - <LLD - - <LLD Ru-103 - <LLD - - <LLD Ru-106 - <LLD - - <LLD Cs-134 0.05 <LLD - - <LLD Cs-137 0.06 <LLD - - <LLD Ba-La-140 - <LLD - - <LLD Ce-141 - <LLD - - <LLD Ce-144 - <LLD - - <LLD Airborne Radioiodine I-131 0.07 <LLD - - <LLD 0 (pCi/m3) (265)

Broadleaf Vegetation Gamma 0 (pCi/kg-wet) (9)

Mn-54 - <LLD - - <LLD Fe-59 - <LLD - - <LLD Co-58 - <LLD - - <LLD Co-60 - <LLD - - <LLD Zn-65 - <LLD - - <LLD Zr-Nb-95 - <LLD - - <LLD I-131 60 <LLD - - <LLD Cs-134 60 <LLD - - <LLD Cs-137 80 <LLD - - <LLD Milk I-131 1 N/A N/A N/A N/A 0 (pCi/L) (0)

Gamma N/A N/A N/A N/A N/A 0 (0) arcadis.com 42

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Type, Control Location with Highest Annual Mean1 (f)2 Total Mean Number of ODCM Indicator Mean1; Analyses Table 3 Number of Medium or Pathway Sampled performed Lower Name Mean1 Nonroutine (Units) Limit of Reported Detection Range1 Measurements (f)2 (f)2 (e.g. I-131, (LLD) Distance and 400) Direction Range1 Range1 Fish Gamma 0 (pCi/kg-wet) (8)

K-403 - 3173 (4/4) M-9 Downstream 3215 (4/4) 3225 (4/4) 3030 - 3230 of Plant 3210 - 3220 3140 - 3300 Mn-54 130 <LLD - - <LLD Fe-59 260 <LLD - - <LLD Co-58 130 <LLD - - <LLD Co-60 130 <LLD - - <LLD Zn-65 260 <LLD - - <LLD Zr-Nb-95 - <LLD - - <LLD Cs-134 130 <LLD - - <LLD Cs-137 150 <LLD - - <LLD Ba-La-140 - <LLD - - <LLD Ce-144 - <LLD - - <LLD Shoreline Sediments Gamma 0 (pCi/kg-dry) (6)

Be-73 - 492 (3/4) M-9, Downstream 699 (1/2) <LLD 320 - 699 of Plant 699 - 699 K-403 - 12000 (4/4) M-15 12600 (2/2) 10850 (2/2) 11000 - 12700 Montissippi Park 12500 - 12700 10600 - 11100 Mn-54 - <LLD - - <LLD Fe-59 - <LLD - - <LLD Co-58 - <LLD - - <LLD Co-60 - <LLD - - <LLD Zn-65 - <LLD - - <LLD Zr-Nb-95 - <LLD - - <LLD Cs-134 150 <LLD - - <LLD Cs-137 180 <LLD - - 34.8 (1/2) 34.8 - 34.8 Ba-La-140 - <LLD - - <LLD Ce-144 - <LLD - - <LLD Drinking Water Gross Beta 4 <LLD - - None 0 (pCi/L) (12)

Gamma 0 (12)

Mn-54 15 <LLD - - None Fe-59 30 <LLD - - None Co-58 15 <LLD - - None Co-60 15 <LLD - - None Zn-65 30 <LLD - - None Zr-Nb-95 154 <LLD - - None Cs-134 15 <LLD - - None Cs-137 18 <LLD - - None Ba-La-140 154 <LLD 6 - <LLD 6 None Ce-144 - <LLD - - None arcadis.com 43

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Type, Control Location with Highest Annual Mean1 (f)2 Total Mean Number of ODCM Indicator Mean1; Analyses Table 3 Number of Medium or Pathway Sampled performed Lower Name Mean1 Nonroutine (Units) Limit of Reported Detection Range1 Measurements (f)2 (f)2 (e.g. I-131, (LLD) Distance and 400) Direction Range1 Range1 Drinking Water I-131 1 <LLD - - None 0 (pCi/L) (7)

Tritium 2000 <LLD - - None 0 (4)

Groundwater Gamma 0 (pCi/L) (16)

Mn-54 15 <LLD - - <LLD Fe-59 30 <LLD - - <LLD Co-58 15 <LLD - - <LLD Co-60 15 <LLD - - <LLD Zn-65 30 <LLD - - <LLD Zr-Nb-95 154 <LLD - - <LLD Cs-134 15 <LLD - - <LLD Cs-137 18 <LLD - - <LLD Ba-La-140 154 <LLD - - <LLD Ce-144 - <LLD - - <LLD I-1317 15 <LLD - - <LLD 0 (4)

Tritium 2000 <LLD - - <LLD 0 (16)

River Water Gamma 0 (pCi/L) (20)

Mn-54 15 <LLD - <LLD <LLD Fe-59 30 <LLD - <LLD <LLD Co-58 15 <LLD - <LLD <LLD Co-60 15 <LLD - <LLD <LLD Zn-65 30 <LLD - <LLD <LLD Zr-Nb-95 154 <LLD - <LLD <LLD Cs-134 15 <LLD - <LLD <LLD Cs-137 18 <LLD - <LLD <LLD Ba-La-140 154 <LLD 6 - <LLD 6 <LLD 6 Ce-144 - <LLD - <LLD <LLD Tritium 2000 <LLD - - <LLD 0 (7)

Direct Radiation: Gamma - N/A M03C 14.2 (4/4) 13.2 (16/16) 0 Control (16) 11.6 mi @ (13.3 - 15.9) (11.8 - 15.9) 130/SE (10 to 12 miles distant)

(mrem/91 days)

Direct Radiation: Gamma - 14.3 (55/55) M11A, 15.2 (4/4) 0 Inner Ring (55) (11.9 - 17.2) 0.4 mi @ (14.2 -17.2) 237/WSW (General Area at Site Boundary)

(mrem/91 days)

Direct Radiation: Gamma - 13.9 (64/64) M14B, 15.4 (4/4) 0 Outer Ring (64) (10.8 - 17.1) 4.3 mi @ (14.4 - 17.1) 289/WNW (4-5 mi. distant)

(mrem/91 days) arcadis.com 44

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Type, Control Location with Highest Annual Mean1 (f)2 Total Mean Number of ODCM Indicator Mean1; Analyses Table 3 Number of Medium or Pathway Sampled performed Lower Name Mean1 Nonroutine (Units) Limit of Reported Detection Range1 Measurements (f)2 (f)2 (e.g. I-131, (LLD) Distance and 400) Direction Range1 Range1 Direct Radiation: Gamma - 14.2 (36/36) M06S, 15.4 (4/4) 0 Special Interest Areas (36) (11 - 17.4) 2.6 mi @134/SE (14.3 - 17.4)

(mrem/91 days)

Notes:

1 Mean and range are based upon detectible measurements only.

2 (f) Fraction of detectible measurements at a specific location 3 Natural and not due to Plant influence 4 The specified LLD applies to the daughter nuclide of an equilibrium mixture of the parent and daughter nuclides.

Per the Radiological Assessment Branch Technical Position, the following values may be used for individual nuclide LLDs when equilibrium conditions are not met: 30 pCi/L for zirconium-95, 15 pCi/L for niobium-95, 60 pCi/L for barium-140, and 15 pCi/L for lanthanum-140.

5 If no drinking water pathway exists, a value of 15 pCi/L may be used.

6 Positive barium-140 results were due to analytical deviations rather than actual detection of Plant related material. Lanthanum-140 was not detected in any of the water samples. In some cases, the required LLD was not met for barium-140/lanthanum-140. See Section 7.5 for further details.

7 Not required arcadis.com 45

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 9 ERRATA TO PREVIOUS REPORTS 9.1 Errata to the MNGP AREOR There are no errata for previous reports from 2020.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 10 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM RESULTS This section provides tabulated REMP monitoring results. Data below were analyzed by GEL. The results reported relate only to the items tested and to the samples as received by the laboratory. Copies of GELs accreditations and certificates can be found at www.gel.com. The table notes, matrix abbreviations, and laboratory qualifiers common to each of the GEL analytical results tables are provided below.

Notes

1. LLDs are a priori values.

2. MDCs are calculated a posteriori value.

3. Gamma spectroscopy analysis results are calculated from a measurement using only one gamma energy line.

4. Results with either no qualifier, an M, or an L are considered positive results. While a U, UI, or ND are negative.

Matrix Abbreviations AC Airborne Cartridge AP Airborne Particulate SE Sediment TA Aquatic Tissue TP Plant Tissue WG Groundwater WP Drinking Water WS Surface Water Qualifiers L Analyte present. Reported value may be biased low. Actual value is expected to be higher M M if above MDC and less than LLD M REMP Result >MDC/CL and <RDL ND Analyte concentration is not detected above the limits as defined as the U qualifier U Analyte was analyzed for, but not detected above the MDL, MDA, MDC, or LOD UI Gamma Spectroscopy - uncertain identification; these results were evaluated and found to be false positives, unless otherwise noted X Lab specific qualifier - see notes from data tables for details.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT 10.1 Detection of activity It is often not possible to say for certain when net radioactivity is present in samples at environmental background levels due to natural variations in counting instrument backgrounds and other factors. The data below is reported as determined by the lab with uncertainties and all data has been included (even results with negative numbers). Results with U, UI, or ND qualifiers are considered not detected and results with L, M, or blank qualifiers are considered to be detected.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT AIRBORNE CARTRIDGE: RADIOIODINE Sample Date Air Station M-1 Air Station M-2 Air Station M-3 Air Station M-4 Air Station M-5 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 1/2/2020 -5.59E-04 +/- 5.56E-03 -6.17E-03 +/- 6.22E-03 7.53E-04 +/- 4.71E-03 -3.84E-03 +/- 9.10E-03 1.96E-03 +/- 6.42E-03 U U U U U 1/8/2020 2.64E-03 +/- 7.44E-03 -2.34E-03 +/- 7.32E-03 9.59E-05 +/- 7.12E-03 6.31E-03 +/- 7.63E-03 -3.17E-03 +/- 7.12E-03 U U U U U 1/15/2020 2.36E-03 +/- 5.26E-03 -4.62E-03 +/- 5.33E-03 -3.52E-03 +/- 6.24E-03 2.54E-03 +/- 7.10E-03 -2.61E-03 +/- 7.58E-03 U U U U U 1/22/2020 -4.02E-03 +/- 5.69E-03 -3.69E-03 +/- 8.26E-03 3.07E-03 +/- 7.42E-03 -1.09E-03 +/- 6.08E-03 5.39E-03 +/- 6.10E-03 U U U U U 1/29/2020 -1.86E-04 +/- 5.87E-03 5.68E-03 +/- 7.81E-03 -6.07E-03 +/- 6.29E-03 2.62E-03 +/- 8.46E-03 -5.10E-03 +/- 5.38E-03 U U U U U 2/5/2020 -6.44E-03 +/- 9.09E-03 -1.40E-03 +/- 7.84E-03 1.33E-03 +/- 6.39E-03 -3.29E-03 +/- 7.66E-03 3.28E-03 +/- 6.17E-03 U U U U U 2/12/2020 -7.65E-03 +/- 9.69E-03 3.17E-03 +/- 5.23E-03 2.14E-03 +/- 5.08E-03 8.29E-04 +/- 6.87E-03 3.09E-03 +/- 6.22E-03 U U U U U 2/19/2020 -3.60E-03 +/- 8.46E-03 -1.66E-03 +/- 5.20E-03 2.77E-03 +/- 6.57E-03 5.57E-03 +/- 7.76E-03 2.55E-03 +/- 4.15E-03 U U U U U 2/26/2020 7.85E-04 +/- 6.00E-03 3.14E-03 +/- 4.94E-03 2.11E-03 +/- 6.20E-03 -4.18E-03 +/- 6.98E-03 6.68E-03 +/- 7.28E-03 U U U U U 3/4/2020 -1.18E-03 +/- 1.07E-02 -3.36E-03 +/- 9.48E-03 -2.39E-03 +/- 6.43E-03 -9.01E-04 +/- 7.51E-03 6.92E-04 +/- 9.33E-03 U U U U U 3/11/2020 1.09E-03 +/- 5.45E-03 -1.40E-03 +/- 5.69E-03 4.87E-03 +/- 8.41E-03 -2.38E-03 +/- 5.48E-03 3.80E-03 +/- 5.31E-03 U U U U U 3/18/2020 4.04E-03 +/- 7.00E-03 -7.62E-05 +/- 5.71E-03 -1.65E-03 +/- 5.86E-03 -1.78E-03 +/- 5.50E-03 4.59E-03 +/- 6.26E-03 U U U U U 3/25/2020 -1.66E-02 +/- 1.64E-02 6.18E-04 +/- 1.61E-02 -5.40E-03 +/- 1.17E-02 -4.00E-03 +/- 1.57E-02 1.73E-03 +/- 1.20E-02 U U U U U 4/1/2020 7.02E-03 +/- 6.13E-03 1.46E-03 +/- 5.34E-03 -3.78E-03 +/- 8.15E-03 -2.71E-03 +/- 6.41E-03 -1.07E-03 +/- 4.50E-03 U U U U U 4/8/2020 2.14E-03 +/- 5.90E-03 -1.07E-03 +/- 5.73E-03 -5.29E-03 +/- 6.56E-03 -2.12E-03 +/- 5.83E-03 -4.43E-03 +/- 5.47E-03 U U U U U 4/15/2020 -2.17E-03 +/- 6.88E-03 3.01E-03 +/- 7.16E-03 -2.88E-03 +/- 8.23E-03 2.66E-03 +/- 7.04E-03 2.67E-03 +/- 6.08E-03 U U U U U 4/22/2020 3.83E-04 +/- 9.15E-03 4.77E-03 +/- 5.66E-03 4.88E-04 +/- 6.08E-03 -2.29E-03 +/- 7.20E-03 -1.58E-03 +/- 6.65E-03 U U U U U 4/29/2020 -9.04E-05 +/- 7.18E-03 2.33E-04 +/- 6.82E-03 4.26E-03 +/- 8.59E-03 1.45E-03 +/- 8.47E-03 4.64E-03 +/- 7.55E-03 U U U U U 5/6/2020 9.94E-03 +/- 9.74E-03 -8.37E-04 +/- 4.54E-03 1.47E-03 +/- 6.61E-03 6.20E-04 +/- 6.85E-03 1.07E-02 +/- 9.88E-03 UI U U U UI 5/13/2020 -3.74E-03 +/- 7.04E-03 1.65E-03 +/- 6.72E-03 -1.13E-03 +/- 6.53E-03 2.44E-03 +/- 6.06E-03 -2.39E-03 +/- 6.57E-03 U U U U U 5/20/2020 -3.12E-03 +/- 5.78E-03 2.83E-03 +/- 7.50E-03 -9.02E-04 +/- 5.06E-03 -2.85E-03 +/- 5.49E-03 7.96E-03 +/- 7.10E-03 U U U U U 5/27/2020 -1.26E-03 +/- 5.62E-03 1.02E-03 +/- 5.25E-03 -4.76E-03 +/- 4.96E-03 1.27E-03 +/- 4.69E-03 -3.52E-03 +/- 6.11E-03 U U U U U 6/3/2020 9.22E-04 +/- 7.63E-03 1.06E-04 +/- 8.32E-03 3.24E-03 +/- 9.54E-03 2.43E-03 +/- 1.53E-02 -5.26E-03 +/- 7.03E-03 U U U U U 6/10/2020 5.60E-03 +/- 6.09E-03 2.30E-03 +/- 5.61E-03 -4.01E-03 +/- 8.57E-03 -2.19E-03 +/- 4.95E-03 -1.61E-03 +/- 6.92E-03 U U U U U 6/17/2020 1.44E-03 +/- 6.72E-03 -6.27E-03 +/- 7.46E-03 5.13E-03 +/- 7.86E-03 2.47E-03 +/- 7.83E-03 1.17E-03 +/- 1.26E-02 U U U U U 6/24/2020 -1.04E-03 +/- 7.37E-03 4.62E-03 +/- 6.81E-03 -5.37E-03 +/- 8.46E-03 8.59E-04 +/- 9.85E-03 -5.67E-03 +/- 7.62E-03 U U U U U 7/1/2020 -5.97E-03 +/- 7.46E-03 -2.33E-03 +/- 5.60E-03 7.70E-03 +/- 1.29E-02 -4.05E-03 +/- 8.06E-03 3.23E-03 +/- 6.08E-03 U U U U U 7/8/2020 1.65E-04 +/- 8.04E-03 4.59E-03 +/- 9.07E-03 3.93E-03 +/- 9.81E-03 -7.13E-03 +/- 1.00E-02 4.20E-03 +/- 1.36E-02 U U U U U arcadis.com 49

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Sample Date Air Station M-1 Air Station M-2 Air Station M-3 Air Station M-4 Air Station M-5 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 7/15/2020 2.45E-03 +/- 5.90E-03 4.26E-03 +/- 6.70E-03 2.23E-03 +/- 6.52E-03 1.68E-03 +/- 9.45E-03 -2.41E-03 +/- 9.33E-03 U U U U U 7/22/2020 1.35E-03 +/- 8.95E-03 4.01E-03 +/- 9.92E-03 7.75E-04 +/- 9.60E-03 -3.29E-03 +/- 1.14E-02 5.67E-05 +/- 7.60E-03 U U U U U 7/29/2020 -4.05E-03 +/- 1.25E-02 4.51E-03 +/- 9.09E-03 -2.45E-03 +/- 1.17E-02 -2.84E-03 +/- 8.71E-03 5.86E-03 +/- 1.22E-02 U U U U U 8/5/2020 3.09E-04 +/- 7.21E-03 -2.20E-03 +/- 6.71E-03 4.70E-04 +/- 7.79E-03 -9.73E-04 +/- 6.24E-03 3.21E-03 +/- 6.06E-03 U U U U U 8/12/2020 -1.59E-03 +/- 6.93E-03 -3.59E-03 +/- 9.09E-03 8.96E-05 +/- 8.52E-03 -5.80E-05 +/- 8.50E-03 -2.11E-03 +/- 7.76E-03 U U U U U 8/19/2020 1.45E-03 +/- 6.14E-03 -9.53E-04 +/- 9.53E-03 -1.02E-03 +/- 1.18E-02 -2.04E-04 +/- 9.02E-03 5.65E-04 +/- 5.61E-03 U U U U U 8/26/2020 5.49E-03 +/- 7.19E-03 1.36E-04 +/- 5.64E-03 4.50E-03 +/- 8.68E-03 1.16E-03 +/- 7.35E-03 -3.05E-03 +/- 6.19E-03 U U U U U 9/2/2020 8.76E-05 +/- 6.76E-03 1.01E-03 +/- 6.80E-03 3.16E-03 +/- 5.85E-03 5.76E-03 +/- 7.57E-03 3.66E-03 +/- 8.03E-03 U U U U U 9/9/2020 1.16E-03 +/- 6.77E-03 2.50E-03 +/- 6.67E-03 4.13E-03 +/- 7.02E-03 -1.47E-03 +/- 6.65E-03 5.31E-04 +/- 7.39E-03 U U U U U 9/16/2020 2.71E-03 +/- 7.19E-03 1.19E-03 +/- 7.51E-03 -2.44E-03 +/- 5.58E-03 -4.18E-04 +/- 5.63E-03 -5.79E-04 +/- 6.45E-03 U U U U U 9/23/2020 6.84E-04 +/- 5.67E-03 2.40E-03 +/- 6.38E-03 -4.29E-03 +/- 7.67E-03 1.40E-02 +/- 9.29E-03 2.20E-03 +/- 6.71E-03 U U U UI U 9/30/2020 -6.37E-04 +/- 7.55E-03 -2.16E-03 +/- 6.78E-03 2.60E-03 +/- 1.05E-02 3.23E-03 +/- 8.46E-03 -7.15E-04 +/- 6.36E-03 U U U U U 10/7/2020 -4.85E-03 +/- 6.98E-03 -1.57E-03 +/- 9.16E-03 -9.02E-03 +/- 6.80E-03 7.84E-03 +/- 6.90E-03 1.21E-03 +/- 5.80E-03 U U U U U 10/14/2020 -2.47E-03 +/- 9.51E-03 1.60E-03 +/- 1.13E-02 -3.36E-03 +/- 8.94E-03 -4.26E-03 +/- 1.13E-02 2.16E-03 +/- 8.47E-03 U U U U U 10/21/2020 7.23E-04 +/- 7.98E-03 1.11E-04 +/- 9.73E-03 6.25E-03 +/- 7.38E-03 -5.92E-03 +/- 9.48E-03 -4.17E-03 +/- 8.48E-03 U U U U U 10/28/2020 -4.50E-03 +/- 8.78E-03 3.48E-03 +/- 1.18E-02 -1.07E-03 +/- 7.69E-03 -1.10E-02 +/- 1.25E-02 6.83E-04 +/- 9.91E-03 U U U U U 11/4/2020 -5.03E-04 +/- 6.82E-03 4.47E-03 +/- 1.34E-02 -3.04E-03 +/- 8.93E-03 1.22E-02 +/- 1.44E-02 -5.94E-03 +/- 6.40E-03 U U U U U 11/11/2020 -1.15E-03 +/- 5.37E-03 3.68E-03 +/- 8.56E-03 -4.24E-03 +/- 6.06E-03 3.17E-03 +/- 5.50E-03 5.60E-04 +/- 5.38E-03 U U U U U 11/18/2020 -1.93E-03 +/- 5.83E-03 1.92E-03 +/- 5.50E-03 3.45E-03 +/- 4.90E-03 -5.45E-03 +/- 5.26E-03 1.83E-03 +/- 5.93E-03 U U U U U 11/25/2020 -2.49E-03 +/- 8.00E-03 6.46E-03 +/- 8.18E-03 -3.34E-03 +/- 1.19E-02 2.50E-03 +/- 8.90E-03 -1.38E-03 +/- 9.89E-03 U U U U U 12/2/2020 -1.78E-03 +/- 6.57E-03 4.81E-03 +/- 6.76E-03 -2.59E-04 +/- 6.69E-03 -1.99E-03 +/- 7.42E-03 -6.82E-03 +/- 7.07E-03 U U U U U 12/9/2020 4.15E-03 +/- 7.00E-03 -1.70E-03 +/- 6.82E-03 -4.02E-03 +/- 7.17E-03 -6.20E-04 +/- 7.44E-03 3.90E-03 +/- 5.98E-03 U U U U U 12/16/2020 -5.02E-03 +/- 7.85E-03 1.44E-02 +/- 9.02E-03 2.57E-03 +/- 8.37E-03 5.32E-03 +/- 5.59E-03 -5.76E-04 +/- 5.39E-03 U UI U U U 12/23/2020 2.67E-03 +/- 7.54E-03 2.75E-03 +/- 1.13E-02 -2.36E-03 +/- 1.76E-02 -6.82E-04 +/- 8.48E-03 -1.08E-02 +/- 1.58E-02 U U U U U 12/30/2020 8.26E-03 +/- 8.08E-03 7.60E-04 +/- 8.18E-03 1.23E-02 +/- 9.71E-03 -1.64E-03 +/- 8.39E-03 -5.61E-04 +/- 8.80E-03 U U U U U arcadis.com 50

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT AIRBORNE PARTICULATES: GROSS BETA Sample Date Air Station M-1 Air Station M-2 Air Station M-3 Air Station M-4 Air Station M-5 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 1/2/2020 0.049 +/- 0.005 0.046 +/- 0.005 0.046 +/- 0.005 0.060 +/- 0.007 0.053 +/- 0.006 1/8/2020 0.027 +/- 0.005 0.026 +/- 0.004 0.029 +/- 0.005 0.036 +/- 0.006 0.030 +/- 0.005 1/15/2020 0.046 +/- 0.005 0.041 +/- 0.005 0.048 +/- 0.006 0.057 +/- 0.006 0.045 +/- 0.005 1/22/2020 0.082 +/- 0.007 0.068 +/- 0.006 0.073 +/- 0.007 0.068 +/- 0.006 0.075 +/- 0.007 1/29/2020 0.037 +/- 0.005 0.033 +/- 0.004 0.036 +/- 0.005 0.041 +/- 0.005 0.034 +/- 0.005 2/5/2020 0.036 +/- 0.005 0.044 +/- 0.006 0.035 +/- 0.005 0.037 +/- 0.005 0.042 +/- 0.005 2/12/2020 0.035 +/- 0.005 0.037 +/- 0.005 0.049 +/- 0.006 0.037 +/- 0.005 0.036 +/- 0.005 2/19/2020 0.049 +/- 0.006 0.045 +/- 0.005 0.043 +/- 0.005 0.039 +/- 0.005 0.047 +/- 0.006 2/26/2020 0.039 +/- 0.005 0.047 +/- 0.005 0.046 +/- 0.005 0.054 +/- 0.006 0.042 +/- 0.005 3/4/2020 0.037 +/- 0.005 0.034 +/- 0.005 0.030 +/- 0.004 0.033 +/- 0.004 0.036 +/- 0.005 3/11/2020 0.027 +/- 0.004 0.025 +/- 0.004 0.040 +/- 0.006 0.037 +/- 0.005 0.029 +/- 0.004 3/18/2020 0.045 +/- 0.006 0.039 +/- 0.005 0.044 +/- 0.005 0.041 +/- 0.005 0.043 +/- 0.005 3/25/2020 0.048 +/- 0.005 0.042 +/- 0.005 0.052 +/- 0.006 0.056 +/- 0.006 0.039 +/- 0.005 4/1/2020 0.032 +/- 0.005 0.038 +/- 0.005 0.040 +/- 0.005 0.043 +/- 0.005 0.036 +/- 0.005 4/8/2020 0.037 +/- 0.005 0.043 +/- 0.005 0.040 +/- 0.005 0.037 +/- 0.005 0.039 +/- 0.005 4/15/2020 0.048 +/- 0.006 0.033 +/- 0.005 0.031 +/- 0.004 0.033 +/- 0.004 0.039 +/- 0.005 4/22/2020 0.046 +/- 0.006 0.036 +/- 0.005 0.032 +/- 0.004 0.036 +/- 0.005 0.043 +/- 0.006 4/29/2020 0.029 +/- 0.004 0.026 +/- 0.004 0.042 +/- 0.006 0.028 +/- 0.005 0.030 +/- 0.004 5/6/2020 0.018 +/- 0.004 0.012 +/- 0.002 0.021 +/- 0.004 0.027 +/- 0.005 0.016 +/- 0.004 5/13/2020 0.026 +/- 0.004 0.026 +/- 0.004 0.029 +/- 0.005 0.038 +/- 0.006 0.028 +/- 0.004 5/20/2020 0.022 +/- 0.004 0.024 +/- 0.004 0.029 +/- 0.005 0.023 +/- 0.004 0.025 +/- 0.004 5/27/2020 0.021 +/- 0.003 0.022 +/- 0.004 0.023 +/- 0.004 0.020 +/- 0.003 0.024 +/- 0.004 6/3/2020 0.023 +/- 0.004 0.026 +/- 0.004 0.022 +/- 0.004 0.029 +/- 0.005 0.027 +/- 0.005 6/10/2020 0.033 +/- 0.004 0.029 +/- 0.004 0.032 +/- 0.004 0.027 +/- 0.004 0.035 +/- 0.005 6/17/2020 0.028 +/- 0.004 0.026 +/- 0.004 0.030 +/- 0.004 0.025 +/- 0.004 0.024 +/- 0.004 6/24/2020 0.026 +/- 0.004 0.032 +/- 0.005 0.026 +/- 0.004 0.030 +/- 0.005 0.030 +/- 0.005 7/1/2020 0.030 +/- 0.004 0.026 +/- 0.004 0.028 +/- 0.004 0.029 +/- 0.005 0.027 +/- 0.004 7/8/2020 0.036 +/- 0.005 0.047 +/- 0.006 0.046 +/- 0.006 0.051 +/- 0.006 0.054 +/- 0.006 7/15/2020 0.027 +/- 0.004 0.031 +/- 0.004 0.030 +/- 0.005 0.031 +/- 0.005 0.034 +/- 0.005 7/22/2020 0.025 +/- 0.004 0.025 +/- 0.004 0.029 +/- 0.005 0.027 +/- 0.004 0.023 +/- 0.004 7/29/2020 0.027 +/- 0.004 0.025 +/- 0.004 0.028 +/- 0.004 0.022 +/- 0.004 0.027 +/- 0.004 8/5/2020 0.024 +/- 0.004 0.023 +/- 0.004 0.022 +/- 0.004 0.021 +/- 0.004 0.020 +/- 0.004 8/12/2020 0.034 +/- 0.005 0.032 +/- 0.004 0.035 +/- 0.005 0.033 +/- 0.005 0.034 +/- 0.005 8/19/2020 0.033 +/- 0.005 0.029 +/- 0.005 0.034 +/- 0.005 0.030 +/- 0.004 0.031 +/- 0.004 arcadis.com 51

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Sample Date Air Station M-1 Air Station M-2 Air Station M-3 Air Station M-4 Air Station M-5 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 8/26/2020 0.042 +/- 0.005 0.049 +/- 0.006 0.050 +/- 0.006 0.044 +/- 0.005 0.043 +/- 0.005 9/2/2020 0.039 +/- 0.005 0.039 +/- 0.005 0.037 +/- 0.005 0.040 +/- 0.005 0.031 +/- 0.004 9/9/2020 0.021 +/- 0.004 0.022 +/- 0.004 0.021 +/- 0.004 0.019 +/- 0.004 0.021 +/- 0.004 9/16/2020 0.033 +/- 0.005 0.027 +/- 0.004 0.040 +/- 0.005 0.029 +/- 0.004 0.035 +/- 0.005 9/23/2020 0.046 +/- 0.005 0.048 +/- 0.006 0.051 +/- 0.006 0.039 +/- 0.005 0.041 +/- 0.005 9/30/2020 0.042 +/- 0.005 0.042 +/- 0.005 0.046 +/- 0.006 0.044 +/- 0.005 0.044 +/- 0.005 10/7/2020 0.030 +/- 0.004 0.028 +/- 0.004 0.026 +/- 0.004 0.028 +/- 0.004 0.028 +/- 0.004 10/14/2020 0.036 +/- 0.005 0.043 +/- 0.006 0.032 +/- 0.005 0.034 +/- 0.005 0.038 +/- 0.005 10/21/2020 0.032 +/- 0.005 0.031 +/- 0.005 0.032 +/- 0.005 0.028 +/- 0.004 0.025 +/- 0.004 10/28/2020 0.047 +/- 0.005 0.046 +/- 0.006 0.054 +/- 0.006 0.047 +/- 0.005 0.050 +/- 0.006 11/4/2020 0.053 +/- 0.005 0.063 +/- 0.007 0.053 +/- 0.005 0.059 +/- 0.006 0.055 +/- 0.006 11/11/2020 0.066 +/- 0.007 0.066 +/- 0.007 0.066 +/- 0.007 0.065 +/- 0.006 0.072 +/- 0.007 11/18/2020 0.061 +/- 0.006 0.059 +/- 0.006 0.059 +/- 0.005 0.055 +/- 0.005 0.061 +/- 0.006 11/25/2020 0.056 +/- 0.006 0.065 +/- 0.007 0.064 +/- 0.007 0.068 +/- 0.007 0.067 +/- 0.007 12/2/2020 0.049 +/- 0.005 0.048 +/- 0.005 0.048 +/- 0.005 0.043 +/- 0.005 0.057 +/- 0.006 12/9/2020 0.071 +/- 0.007 0.066 +/- 0.007 0.085 +/- 0.008 0.072 +/- 0.007 0.070 +/- 0.007 12/16/2020 0.045 +/- 0.005 0.047 +/- 0.006 0.050 +/- 0.006 0.050 +/- 0.005 0.048 +/- 0.006 12/23/2020 0.060 +/- 0.006 0.068 +/- 0.006 0.067 +/- 0.006 0.068 +/- 0.006 0.075 +/- 0.007 12/30/2020 0.033 +/- 0.005 0.039 +/- 0.005 0.034 +/- 0.005 0.046 +/- 0.005 0.038 +/- 0.005 AIRBORNE PARTICULATES: GAMMA ISOTOPIC Air Station M-1 Qtr 1 Qtr 2 Qtr 3 Qtr 4 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 7.28E-04 +/- 2.50E-03 7.88E-04 +/- 2.18E-03 2.57E-04 +/- 1.98E-03 1.31E-03 +/- 1.54E-03 Barium-140 U U U U Beryllium-7 6.34E-02 +/- 8.61E-03 8.94E-02 +/- 8.95E-03 8.21E-02 +/- 8.63E-03 6.50E-02 +/- 6.34E-03 2.25E-04 +/- 3.21E-04 2.57E-04 +/- 3.37E-04 -1.54E-04 +/- 3.15E-04 -8.99E-05 +/- 2.07E-04 Cerium-141 U U U U 8.50E-04 +/- 1.06E-03 2.24E-04 +/- 9.35E-04 2.16E-04 +/- 9.45E-04 -8.45E-04 +/- 6.53E-04 Cerium-144 U U U U

-1.47E-04 +/- 2.74E-04 -1.21E-04 +/- 2.29E-04 1.84E-04 +/- 2.73E-04 1.71E-04 +/- 2.27E-04 Cesium-134 U U U U 5.91E-05 +/- 2.50E-04 -1.00E-04 +/- 2.20E-04 -1.44E-05 +/- 2.20E-04 1.94E-04 +/- 4.07E-04 Cesium-137 U U U U

-1.09E-04 +/- 2.85E-04 6.81E-05 +/- 2.23E-04 1.53E-05 +/- 2.35E-04 2.25E-04 +/- 2.56E-04 Cobalt-58 U U U U 2.65E-05 +/- 2.33E-04 -3.10E-04 +/- 2.69E-04 5.18E-05 +/- 2.89E-04 -9.13E-05 +/- 2.29E-04 Cobalt-60 U U U U

-1.67E-04 +/- 1.04E-03 -1.44E-04 +/- 9.17E-04 4.57E-04 +/- 7.85E-04 1.85E-04 +/- 2.94E-04 Lanthanum-140 U U U U arcadis.com 52

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Air Station M-1 Qtr 1 Qtr 2 Qtr 3 Qtr 4 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3)

-1.36E-04 +/- 2.55E-04 1.35E-04 +/- 3.44E-04 2.49E-04 +/- 2.45E-04 1.90E-04 +/- 2.56E-04 Manganese-54 U U U U

-7.20E-05 +/- 3.90E-04 1.01E-04 +/- 3.22E-04 -1.80E-04 +/- 2.37E-04 -2.26E-05 +/- 2.55E-04 Niobium-95 U U U U

-2.64E-05 +/- 2.82E-04 -1.41E-04 +/- 2.10E-04 -3.07E-05 +/- 2.59E-04 -6.28E-05 +/- 2.20E-04 Ruthenium-103 U U U U 4.49E-04 +/- 1.90E-03 1.51E-03 +/- 2.19E-03 -7.62E-04 +/- 1.76E-03 1.77E-03 +/- 3.59E-03 Ruthenium-106 U U U U 8.78E-04 +/- 4.97E-04 -2.43E-04 +/- 4.40E-04 -3.61E-05 +/- 5.46E-04 2.22E-04 +/- 4.82E-04 Zinc-65 U U U U 1.46E-04 +/- 4.82E-04 -1.67E-04 +/- 4.80E-04 4.73E-04 +/- 5.45E-04 -7.80E-05 +/- 4.52E-04 Zirconium-95 U U U U Air Station M-2 Qtr 1 Qtr 2 Qtr 3 Qtr 4 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 5.00E-04 +/- 3.28E-03 -9.54E-04 +/- 1.91E-03 4.88E-04 +/- 2.05E-03 -1.15E-03 +/- 2.16E-03 Barium-140 U U U U Beryllium-7 5.60E-02 +/- 1.23E-02 8.80E-02 +/- 7.94E-03 8.45E-02 +/- 7.96E-03 6.64E-02 +/- 9.20E-03

-2.27E-04 +/- 5.09E-04 -1.79E-04 +/- 3.43E-04 -6.87E-06 +/- 3.04E-04 -1.49E-04 +/- 3.24E-04 Cerium-141 U U U U 7.91E-04 +/- 1.39E-03 -7.00E-04 +/- 7.48E-04 -9.49E-05 +/- 8.66E-04 -2.79E-04 +/- 1.02E-03 Cerium-144 U U U U

-1.62E-04 +/- 3.43E-04 1.78E-04 +/- 2.43E-04 -5.08E-05 +/- 2.26E-04 1.75E-04 +/- 3.34E-04 Cesium-134 U U U U 1.48E-04 +/- 4.99E-04 -1.60E-05 +/- 2.00E-04 -9.78E-05 +/- 2.40E-04 -6.32E-05 +/- 2.99E-04 Cesium-137 U U U U

-6.92E-05 +/- 3.96E-04 -1.95E-04 +/- 1.85E-04 1.41E-04 +/- 2.52E-04 1.49E-04 +/- 3.13E-04 Cobalt-58 U U U U

-2.87E-04 +/- 4.00E-04 3.61E-04 +/- 2.55E-04 -1.06E-04 +/- 2.44E-04 -7.24E-05 +/- 3.08E-04 Cobalt-60 U U U U 3.75E-05 +/- 1.23E-03 1.18E-04 +/- 5.86E-04 -5.77E-04 +/- 8.73E-04 6.98E-04 +/- 7.24E-04 Lanthanum-140 U U U U 1.47E-04 +/- 2.97E-04 -4.57E-05 +/- 1.78E-04 -2.66E-05 +/- 1.74E-04 1.03E-04 +/- 3.13E-04 Manganese-54 U U U U 1.85E-04 +/- 3.61E-04 -1.17E-05 +/- 2.53E-04 9.87E-07 +/- 2.72E-04 3.35E-04 +/- 3.59E-04 Niobium-95 U U U U

-2.35E-04 +/- 3.93E-04 -9.65E-05 +/- 2.40E-04 6.62E-05 +/- 2.63E-04 -5.85E-05 +/- 2.35E-04 Ruthenium-103 U U U U 4.75E-04 +/- 2.19E-03 1.59E-03 +/- 1.49E-03 1.90E-03 +/- 2.11E-03 -1.30E-03 +/- 2.81E-03 Ruthenium-106 U U U U

-5.10E-04 +/- 1.04E-03 -1.55E-04 +/- 4.45E-04 1.74E-05 +/- 5.50E-04 1.10E-05 +/- 6.78E-04 Zinc-65 U U U U

-3.22E-06 +/- 8.15E-04 2.07E-04 +/- 3.29E-04 -1.67E-04 +/- 4.47E-04 -4.12E-04 +/- 5.08E-04 Zirconium-95 U U U U arcadis.com 53

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Air Station M-3 Qtr 1 Qtr 2 Qtr 3 Qtr 4 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3) 4.31E-04 +/- 1.89E-03 2.93E-04 +/- 2.35E-03 2.00E-04 +/- 2.08E-03 6.09E-04 +/- 1.31E-03 Barium-140 U U U U Beryllium-7 7.30E-02 +/- 8.79E-03 1.04E-01 +/- 1.06E-02 9.44E-02 +/- 8.57E-03 6.23E-02 +/- 7.35E-03

-2.96E-04 +/- 3.19E-04 -5.46E-04 +/- 4.75E-04 2.85E-05 +/- 3.30E-04 2.94E-05 +/- 3.33E-04 Cerium-141 U U U U 1.02E-04 +/- 8.94E-04 -1.11E-04 +/- 1.06E-03 4.44E-04 +/- 1.05E-03 5.62E-04 +/- 1.07E-03 Cerium-144 U U U U 6.19E-05 +/- 2.04E-04 -5.20E-05 +/- 3.49E-04 -1.97E-04 +/- 2.50E-04 -4.57E-05 +/- 2.28E-04 Cesium-134 U U U U

-5.49E-05 +/- 2.07E-04 1.46E-04 +/- 2.71E-04 1.47E-04 +/- 2.20E-04 -4.50E-05 +/- 2.35E-04 Cesium-137 U U U U

-1.78E-04 +/- 2.71E-04 1.99E-05 +/- 2.79E-04 -5.11E-05 +/- 2.56E-04 5.11E-05 +/- 2.99E-04 Cobalt-58 U U U U 5.45E-05 +/- 2.59E-04 -6.17E-05 +/- 3.51E-04 -7.23E-05 +/- 2.78E-04 -1.53E-04 +/- 2.26E-04 Cobalt-60 U U U U 1.40E-05 +/- 6.38E-04 1.24E-04 +/- 1.55E-03 2.70E-04 +/- 9.83E-04 9.70E-05 +/- 6.51E-04 Lanthanum-140 U U U U

-6.44E-05 +/- 2.37E-04 1.89E-04 +/- 2.56E-04 1.51E-04 +/- 2.22E-04 9.74E-05 +/- 2.40E-04 Manganese-54 U U U U 1.04E-04 +/- 2.48E-04 -1.62E-04 +/- 3.19E-04 -2.14E-04 +/- 3.32E-04 -6.32E-05 +/- 3.26E-04 Niobium-95 U U U U

-6.78E-05 +/- 2.80E-04 -1.09E-04 +/- 2.77E-04 3.81E-04 +/- 4.03E-04 -2.10E-05 +/- 2.49E-04 Ruthenium-103 U U U U

-2.78E-04 +/- 1.75E-03 1.34E-03 +/- 2.45E-03 3.28E-03 +/- 4.17E-03 -4.38E-04 +/- 2.12E-03 Ruthenium-106 U U UI U

-5.79E-05 +/- 5.65E-04 3.53E-04 +/- 6.59E-04 -3.98E-05 +/- 5.13E-04 -2.04E-04 +/- 4.96E-04 Zinc-65 U U U U

-4.73E-05 +/- 3.79E-04 -9.80E-06 +/- 6.03E-04 2.17E-04 +/- 3.91E-04 6.97E-05 +/- 4.04E-04 Zirconium-95 U U U U arcadis.com 54

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Air Station M-4 Qtr 1 Qtr 2 Qtr 3 Qtr 4 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3)

-5.06E-04 +/- 2.33E-03 6.71E-04 +/- 2.17E-03 6.91E-04 +/- 1.92E-03 2.34E-03 +/- 3.00E-03 Barium-140 U U U U Beryllium-7 6.96E-02 +/- 8.48E-03 1.02E-01 +/- 9.91E-03 7.39E-02 +/- 7.69E-03 6.79E-02 +/- 1.14E-02

-2.17E-04 +/- 4.39E-04 -2.38E-04 +/- 4.09E-04 3.20E-04 +/- 3.81E-04 -6.01E-04 +/- 5.01E-04 Cerium-141 U U U U

-7.48E-05 +/- 1.11E-03 -2.87E-04 +/- 1.06E-03 4.69E-04 +/- 1.01E-03 -9.35E-04 +/- 1.66E-03 Cerium-144 U U U U

-1.09E-04 +/- 2.53E-04 9.30E-05 +/- 2.48E-04 2.94E-05 +/- 2.03E-04 4.67E-04 +/- 4.86E-04 Cesium-134 U U U U 4.12E-05 +/- 2.70E-04 -6.45E-05 +/- 2.58E-04 2.25E-04 +/- 1.60E-04 5.61E-05 +/- 4.77E-04 Cesium-137 U U U U

-1.30E-05 +/- 2.61E-04 1.07E-05 +/- 2.63E-04 7.58E-05 +/- 2.02E-04 6.13E-04 +/- 5.24E-04 Cobalt-58 U U U U 3.21E-05 +/- 3.18E-04 1.12E-04 +/- 2.84E-04 -1.77E-05 +/- 2.49E-04 1.14E-04 +/- 4.97E-04 Cobalt-60 U U U U

-3.73E-04 +/- 9.97E-04 -3.12E-04 +/- 8.07E-04 -8.57E-05 +/- 7.10E-04 5.71E-05 +/- 1.11E-03 Lanthanum-140 U U U U

-4.82E-05 +/- 2.81E-04 3.30E-04 +/- 2.53E-04 -1.89E-05 +/- 2.69E-04 -8.82E-05 +/- 4.40E-04 Manganese-54 U U U U 3.41E-05 +/- 3.97E-04 1.13E-04 +/- 2.30E-04 -1.21E-05 +/- 2.21E-04 -2.78E-04 +/- 5.08E-04 Niobium-95 U U U U

-2.65E-05 +/- 3.27E-04 1.19E-04 +/- 2.86E-04 -9.09E-07 +/- 2.14E-04 -2.67E-04 +/- 4.05E-04 Ruthenium-103 U U U U 2.93E-04 +/- 2.48E-03 1.27E-03 +/- 2.13E-03 1.29E-03 +/- 1.89E-03 5.86E-04 +/- 2.76E-03 Ruthenium-106 U U U U

-2.54E-04 +/- 6.22E-04 -1.89E-04 +/- 4.42E-04 -2.24E-04 +/- 5.67E-04 -2.55E-04 +/- 1.14E-03 Zinc-65 U U U U

-2.94E-04 +/- 4.89E-04 1.58E-04 +/- 4.81E-04 1.11E-04 +/- 4.53E-04 -1.98E-04 +/- 8.47E-04 Zirconium-95 U U U U arcadis.com 55

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Air Station M-5 Qtr 1 Qtr 2 Qtr 3 Qtr 4 (pCi/m3) (pCi/m3) (pCi/m3) (pCi/m3)

-1.53E-03 +/- 2.25E-03 -5.80E-04 +/- 2.57E-03 5.54E-04 +/- 2.37E-03 3.87E-04 +/- 1.87E-03 Barium-140 U U U U Beryllium-7 6.34E-02 +/- 7.51E-03 9.93E-02 +/- 9.92E-03 8.15E-02 +/- 8.75E-03 6.72E-02 +/- 8.23E-03

-4.54E-04 +/- 4.60E-04 -3.07E-04 +/- 4.97E-04 -7.40E-04 +/- 4.46E-04 4.06E-05 +/- 4.38E-04 Cerium-141 U U U U 5.54E-06 +/- 1.08E-03 1.01E-03 +/- 1.85E-03 4.65E-04 +/- 1.09E-03 4.41E-04 +/- 1.15E-03 Cerium-144 U U U U

-4.00E-05 +/- 2.73E-04 2.03E-04 +/- 2.77E-04 1.16E-04 +/- 2.64E-04 -2.39E-04 +/- 3.01E-04 Cesium-134 U U U U 6.29E-05 +/- 2.38E-04 1.85E-04 +/- 2.44E-04 2.98E-05 +/- 2.35E-04 -1.88E-06 +/- 2.63E-04 Cesium-137 U U U U

-1.36E-04 +/- 2.82E-04 5.44E-05 +/- 3.00E-04 4.17E-05 +/- 2.88E-04 5.70E-05 +/- 2.60E-04 Cobalt-58 U U U U

-1.46E-05 +/- 2.41E-04 7.59E-05 +/- 2.50E-04 4.65E-06 +/- 2.75E-04 -1.75E-04 +/- 2.63E-04 Cobalt-60 U U U U

-6.90E-04 +/- 8.45E-04 3.78E-04 +/- 1.13E-03 3.00E-04 +/- 6.78E-04 9.26E-06 +/- 8.75E-04 Lanthanum-140 U U U U 1.18E-04 +/- 2.20E-04 -9.32E-05 +/- 2.71E-04 6.09E-05 +/- 2.12E-04 2.26E-04 +/- 2.46E-04 Manganese-54 U U U U 2.61E-05 +/- 3.16E-04 -6.21E-05 +/- 3.22E-04 4.78E-05 +/- 3.19E-04 -1.57E-04 +/- 3.04E-04 Niobium-95 U U U U

-1.23E-04 +/- 2.75E-04 1.51E-04 +/- 3.05E-04 -1.30E-04 +/- 2.32E-04 2.06E-06 +/- 3.38E-04 Ruthenium-103 U U U U 1.56E-04 +/- 2.11E-03 2.20E-03 +/- 2.46E-03 -1.73E-03 +/- 1.87E-03 -5.83E-04 +/- 2.45E-03 Ruthenium-106 U U U U 5.43E-05 +/- 4.47E-04 1.55E-04 +/- 6.03E-04 -2.91E-04 +/- 6.00E-04 1.52E-04 +/- 5.33E-04 Zinc-65 U U U U 8.74E-05 +/- 5.38E-04 -2.97E-04 +/- 6.24E-04 1.98E-04 +/- 5.17E-04 7.14E-05 +/- 3.98E-04 Zirconium-95 U U U U arcadis.com 56

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT SEDIMENT: GAMMA ISOTOPIC M-8c Upstream of Plant Qtr 2 Qtr 4 M-9 Downstream Qtr 2 Qtr 4 of Plant (pCi/Kg, dry) (pCi/Kg, dry) (pCi/Kg, dry) (pCi/Kg, dry)

Barium-140 -53.9 +/- 55.0 33.7 +/- 87.7 Barium-140 4.3 +/- 93.2 -15.0 +/- 98.3 U U U U Beryllium-7 117.0 +/- 97.5 178.0 +/- 276.0 Beryllium-7 234.0 +/- 270.0 699.0 +/- 342.0 U U UI Cerium-144 20.4 +/- 64.9 -55.9 +/- 91.2 Cerium-144 61.5 +/- 62.6 44.2 +/- 116.0 U U U U Cesium-134 8.2 +/- 16.3 25.6 +/- 24.8 Cesium-134 14.0 +/- 17.6 -14.1 +/- 24.0 U U U U Cesium-137 34.8 +/- 23.4 6.9 +/- 16.3 Cesium-137 20.9 +/- 25.2 36.2 +/- 27.5 M U U U Cobalt-58 -4.2 +/- 12.9 10.3 +/- 14.4 Cobalt-58 -7.0 +/- 17.7 20.3 +/- 16.8 U U U U Cobalt-60 4.1 +/- 15.3 -10.1 +/- 20.1 Cobalt-60 0.3 +/- 16.4 -0.5 +/- 26.2 U U U U Iron-59 -24.9 +/- 39.8 9.2 +/- 35.7 Iron-59 -22.8 +/- 33.2 -11.8 +/- 44.3 U U U U Lanthanum-140 -16.6 +/- 17.0 4.1 +/- 25.4 Lanthanum-140 -21.6 +/- 28.4 -10.3 +/- 35.3 U U U U Manganese-54 3.8 +/- 13.8 6.1 +/- 16.2 Manganese-54 15.4 +/- 19.1 -6.5 +/- 21.0 U U U U Niobium-95 3.1 +/- 13.1 -4.3 +/- 16.2 Niobium-95 11.6 +/- 17.0 -0.8 +/- 25.9 U U U U Potassium-40 10600.0 +/- 750.0 11100.0 +/- 837.0 Potassium-40 11000.0 +/- 805.0 11800.0 +/- 1070.0 Ruthenium-103 -0.4 +/- 11.2 2.3 +/- 13.7 Ruthenium-103 -8.0 +/- 11.9 -1.5 +/- 20.5 U U U U Ruthenium-106 80.1 +/- 99.1 4.0 +/- 136.0 Ruthenium-106 11.6 +/- 140.0 20.5 +/- 184.0 U U U U Zinc-65 6.5 +/- 36.5 9.4 +/- 38.9 Zinc-65 1.6 +/- 37.8 25.5 +/- 45.7 U U U U Zirconium-95 13.6 +/- 25.0 6.2 +/- 30.7 Zirconium-95 -21.6 +/- 30.2 -9.0 +/- 42.4 U U U U arcadis.com 57

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT M-15 Montissippi Park Qtr 2 Qtr 4 (pCi/Kg, dry) (pCi/Kg, dry)

Barium-140 40.0 +/- 46.8 -68.8 +/- 94.8 U U Beryllium-7 320.0 +/- 200.0 456.0 +/- 262.0 Cerium-144 15.0 +/- 68.1 -19.7 +/- 90.9 U U Cesium-134 22.0 +/- 23.9 24.6 +/- 28.7 U U Cesium-137 22.6 +/- 26.1 27.2 +/- 21.9 UI U Cobalt-58 5.7 +/- 12.5 9.8 +/- 16.5 U U Cobalt-60 -1.2 +/- 13.8 8.4 +/- 18.6 U U Iron-59 21.1 +/- 28.7 3.7 +/- 42.4 U U Lanthanum-140 1.9 +/- 12.1 4.0 +/- 28.1 U U Manganese-54 25.9 +/- 20.3 6.0 +/- 17.4 UI U Niobium-95 -4.2 +/- 15.4 -0.4 +/- 18.9 U U Potassium-40 12500.0 +/- 700.0 12700.0 +/- 963.0 Ruthenium-103 -6.8 +/- 10.8 3.4 +/- 18.1 U U Ruthenium-106 -23.1 +/- 108.0 2.3 +/- 153.0 U U Zinc-65 15.1 +/- 35.7 2.9 +/- 48.5 U U Zirconium-95 3.0 +/- 26.8 21.0 +/- 31.0 U U arcadis.com 58

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT TISSUE - FISH: GAMMA ISOTOPIC M-8c Upstream of Plant M-9 Downstream of Plant (pCi/Kg, wet)

May Sep May Sep Fish 1 Fish 2 Fish 1 Fish 2 Fish 1 Fish 2 Fish 1 Fish 2 Barium-140 9.6 +/- 18.5 8.4 +/- 15.8 -1.2 +/- 30.0 22.0 +/- 36.6 14.2 +/- 19.3 12.5 +/- 34.5 9.0 +/- 26.2 19.0 +/- 36.0 U U U U U U U U Cerium-144 -21.5 +/- 21.4 -7.7 +/- 18.4 -28.9 +/- 44.7 3.1 +/- 43.3 -13.5 +/- 16.0 0.7 +/- 16.7 -21.8 +/- 28.3 3.4 +/- 45.1 U U U U U U U U Cesium-134 3.1 +/- 3.9 -6.6 +/- 4.2 0.7 +/- 8.4 3.9 +/- 11.4 3.7 +/- 3.9 2.1 +/- 5.4 0.1 +/- 7.1 0.7 +/- 9.0 U U U U U U U U Cesium-137 1.5 +/- 3.6 5.3 +/- 3.5 -0.6 +/- 7.5 2.2 +/- 10.1 1.8 +/- 3.6 5.1 +/- 4.9 2.1 +/- 5.3 7.1 +/- 9.4 U U U U U U U U Cobalt-58 2.0 +/- 3.4 -0.2 +/- 3.2 4.4 +/- 8.8 0.2 +/- 10.9 2.9 +/- 3.1 0.0 +/- 3.0 1.1 +/- 6.1 -2.0 +/- 8.1 U U U U U U U U Cobalt-60 1.0 +/- 4.3 -2.6 +/- 3.7 -1.1 +/- 10.7 4.1 +/- 9.3 -0.6 +/- 4.0 -0.3 +/- 3.5 -3.0 +/- 5.9 2.1 +/- 10.4 U U U U U U U U Iron-59 -2.1 +/- 8.1 8.5 +/- 7.8 -12.0 +/- 19.5 22.6 +/- 21.8 3.7 +/- 7.7 3.2 +/- 8.0 -0.3 +/- 14.7 -2.8 +/- 16.9 U U U U U U U U Lanthanum-140 5.4 +/- 4.9 -3.6 +/- 4.9 -8.6 +/- 12.8 -6.2 +/- 8.6 3.4 +/- 4.7 -5.2 +/- 4.3 0.1 +/- 9.0 4.0 +/- 12.1 U U U U U U U U Manganese-54 0.3 +/- 3.5 0.3 +/- 3.0 5.2 +/- 8.2 0.5 +/- 9.3 1.4 +/- 3.3 -3.9 +/- 3.2 0.9 +/- 5.9 4.8 +/- 8.1 U U U U U U U U Niobium-95 1.4 +/- 3.2 1.6 +/- 3.1 1.9 +/- 9.5 3.9 +/- 8.2 -0.4 +/- 3.9 0.2 +/- 3.4 1.7 +/- 5.9 0.4 +/- 8.5 U U U U U U U U Potassium-40 3260.0 +/- 201.0 3200.0 +/- 194.0 3140.0 +/- 448.0 3300.0 +/- 459.0 3210.0 +/- 201.0 3030.0 +/- 193.0 3220.0 +/- 379.0 3230.0 +/- 470.0 Zinc-65 -3.1 +/- 8.5 1.6 +/- 9.6 3.8 +/- 15.5 19.4 +/- 29.1 7.7 +/- 10.0 0.2 +/- 9.3 2.1 +/- 14.7 10.8 +/- 22.7 U U U U U U U U Zirconium-95 -1.6 +/- 5.9 1.1 +/- 6.0 -5.3 +/- 11.7 -3.4 +/- 14.2 2.5 +/- 5.7 2.0 +/- 5.8 2.4 +/- 9.2 32.5 +/- 22.5 U U U U U U U UI arcadis.com 59

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT TISSUE - PLANT: GAMMA ISOTOPIC M-41 Training Center M-42 Biology Station Road pCi/Kg Jun Jul Aug Sep Jun Jul Aug Sep

-4.1 +/- 9.4 4.3 +/- 11.3 -1.2 +/- 9.4 4.6 +/- 9.5 2.3 +/- 11.9 -0.5 +/- 13.0 -1.8 +/- 9.0 4.1 +/- 17.0 Cesium-134 U U U U U U U U

-3.9 +/- 7.6 3.7 +/- 10.6 3.4 +/- 7.6 25.5 +/- 20.3 -3.9 +/- 11.3 7.7 +/- 12.1 -2.9 +/- 7.0 -9.5 +/- 20.7 Cesium-137 U U U UI U U U U

-8.6 +/- 10.8 -4.2 +/- 10.2 4.4 +/- 8.7 -5.1 +/- 8.7 0.3 +/- 11.5 4.5 +/- 10.5 2.8 +/- 8.0 9.0 +/- 13.7 Cobalt-58 U U U U U U U U 1.5 +/- 9.5 -3.6 +/- 14.9 -2.5 +/- 10.2 -4.3 +/- 9.4 5.8 +/- 20.1 -2.5 +/- 17.7 -1.6 +/- 10.6 -2.0 +/- 12.2 Cobalt-60 U U U U U U U U 9.1 +/- 16.5 -11.0 +/- 15.3 -2.9 +/- 12.8 -2.3 +/- 16.2 26.0 +/- 19.3 11.2 +/- 21.0 -7.6 +/- 10.8 20.9 +/- 23.2 Iodine-131 U U U U U U U U

-16.6 +/- 24.8 -19.6 +/- 23.7 0.3 +/- 17.7 -2.7 +/- 22.3 4.6 +/- 26.7 -21.3 +/- 29.8 -8.7 +/- 17.6 -12.5 +/- 28.3 Iron-59 U U U U U U U U Manganese- -5.7 +/- 8.8 -0.6 +/- 7.7 6.8 +/- 8.9 -0.4 +/- 8.4 -8.9 +/- 12.2 4.5 +/- 12.7 -0.3 +/- 8.0 -12.1 +/- 14.7 54 U U U U U U U U 5.5 +/- 9.0 5.0 +/- 9.6 4.0 +/- 9.0 -0.2 +/- 8.6 -4.2 +/- 11.0 1.7 +/- 12.4 4.2 +/- 8.5 6.3 +/- 15.2 Niobium-95 U U U U U U U U 0.9 +/- 21.4 2.7 +/- 18.3 17.9 +/- 38.7 0.0 +/- 20.9 -18.4 +/- 30.4 -16.6 +/- 29.2 -5.7 +/- 18.4 4.8 +/- 28.9 Zinc-65 U U U U U U U U M-43 Imholte Farm pCi/Kg Jun Jul Aug Sep

-2.0 +/- 9.8 20.4 +/- 17.7 -2.3 +/- 17.9 1.7 +/- 13.4 Cesium-134 U U U U

-4.1 +/- 7.5 2.0 +/- 17.0 1.6 +/- 14.5 0.2 +/- 11.9 Cesium-137 U U U U 1.8 +/- 7.9 -3.1 +/- 14.6 6.1 +/- 13.8 0.1 +/- 11.4 Cobalt-58 U U U U

-4.3 +/- 9.0 -8.2 +/- 14.6 4.2 +/- 16.9 7.6 +/- 12.4 Cobalt-60 U U U U 3.3 +/- 15.8 2.6 +/- 25.4 6.2 +/- 22.3 19.9 +/- 21.2 Iodine-131 U U U U

-28.2 +/- 24.4 -0.7 +/- 35.6 0.3 +/- 33.9 -15.2 +/- 23.1 Iron-59 U U U U Manganese- 1.9 +/- 9.1 -7.7 +/- 13.7 -1.4 +/- 13.0 6.1 +/- 11.6 54 U U U U 11.9 +/- 9.1 7.0 +/- 14.7 2.4 +/- 14.7 -3.5 +/- 14.4 Niobium-95 U U U U 10.5 +/- 24.0 3.7 +/- 37.2 14.0 +/- 38.5 20.3 +/- 29.9 Zinc-65 U U U U arcadis.com 60

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT WATER: TRITIUM pCi/L Qtr 1 Qtr 2 Qtr 3 Qtr 4 M-11 City of -57.0 +/- 249.0 108.0 +/- 181.0 63.4 +/- 275.0 24.2 +/- 133.0 Monticello U U U U 35.0 +/- 254.0 159.0 +/- 189.0 15.6 +/- 272.0 -26.4 +/- 131.0 M-12 Plant Well #11 U U U U M-14 City of 142.0 +/- 278.0 176.0 +/- 136.0 56.6 +/- 112.0 65.4 +/- 171.0 Minneapolis1 U U U U

-23.4 +/- 248.0 -47.3 +/- 169.0 42.8 +/- 265.0 -0.2 +/- 136.0 M-43 Imholte Farm U U U U M-55 Hasbrouck -109.0 +/- 246.0 94.2 +/- 180.0 252.0 +/- 280.0 37.4 +/- 142.0 Residence U U U U M-8 Upstream of -8.4 +/- 154.0 -236.0 +/- 259.0 115.0 +/- 254.0 151.0 +/- 219.0 Plant U U U U M-9 Downstream of -17.6 +/- 143.0 -154.0 +/- 266.0 -155.0 +/- 232.0 19.1 +/- 220.0 Plant U U U U 1Q4 2020 composite sample collection continued into January 4, 2021.

arcadis.com 61

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT WATER - DRINKING: GROSS BETA M-14 City of Gross Beta Minneapolis (pCi/L) 1.570 +/- 2.240 Jan U

2.110 +/- 2.330 Feb U

1.620 +/- 1.820 Mar U

1.590 +/- 2.180 Apr U

1.870 +/- 2.130 May U

1.290 +/- 1.510 Jun U

0.174 +/- 1.940 Jul U

0.717 +/- 2.110 Aug1 U 1.550 +/- 2.040 Sep U

0.051 +/- 1.540 Oct1 U 1.010 +/- 2.030 Nov1 U 1.780 +/- 1.990 Dec1 U 1Monthly composite samples collected in August, October, November, and December continued into the first few days of each subsequent respective month.

arcadis.com 62

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT WATER - DRINKING: IODINE-131 M-14 City of Iodine-131 Minneapolis (pCi/L) 1/2/2020 -1.15E-01 +/- 2.71E-01 U

1/8/2020 2.57E-01 +/- 3.33E-01 U

1/15/2020 -4.81E-01 +/- 5.38E-01 U

1/22/2020 3.47E-01 +/- 5.60E-01 U

1/29/2020 -2.52E-01 +/- 5.07E-01 U

2/5/2020 -3.28E-01 +/- 4.61E-01 U

2/12/2020 3.20E-01 +/- 5.35E-01 U

Iodine-131 analysis completed on each bi-weekly sample when the dose from the consumption of the water is greater than 1 mrem/year (ODCM Revision 26) arcadis.com 63

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT WATER - GROUNDWATER: GAMMA ISOTOPIC Qtr 1 Qtr 2 Qtr 3 Qtr 4 M-11 City of Monticello (pCi/L) (pCi/L) (pCi/L) (pCi/L)

-3.92E+00 +/- 6.37E+00 1.83E+00 +/- 4.52E+00 3.83E+00 +/- 1.62E+01 -1.86E+00 +/- 1.36E+01 Barium-140 U U U U

-1.13E+00 +/- 6.17E+00 -3.76E-01 +/- 5.95E+00 -3.47E+00 +/- 2.03E+01 4.45E+00 +/- 1.73E+01 Cerium-144 U U U U

-9.66E-02 +/- 9.73E-01 3.74E-01 +/- 9.58E-01 2.31E+00 +/- 3.01E+00 -3.71E-01 +/- 2.31E+00 Cesium-134 U U U U

-2.40E-01 +/- 8.63E-01 8.22E-01 +/- 2.35E+00 2.96E+00 +/- 2.78E+00 -8.83E-01 +/- 2.16E+00 Cesium-137 U U U U

-4.18E-01 +/- 1.03E+00 -5.34E-01 +/- 8.83E-01 -6.55E-01 +/- 3.92E+00 1.08E+00 +/- 2.11E+00 Cobalt-58 U U U U

-7.76E-01 +/- 1.03E+00 -5.54E-01 +/- 9.96E-01 -1.57E+00 +/- 3.80E+00 -1.57E+00 +/- 2.59E+00 Cobalt-60 U U U U 2.14E+00 +/- 2.17E+00 8.75E-01 +/- 1.77E+00 -3.11E+00 +/- 5.33E+00 -1.58E+00 +/- 4.12E+00 Iron-59 U U U U 4.80E-01 +/- 8.83E-01 -4.34E-02 +/- 9.15E-01 -8.94E-01 +/- 3.34E+00 -4.66E-01 +/- 1.75E+00 Lanthanum-140 U U U U 6.76E-03 +/- 9.95E-01 4.55E-01 +/- 1.08E+00 -7.20E-01 +/- 3.03E+00 -6.98E-01 +/- 2.50E+00 Manganese-54 U U U U

-2.27E+00 +/- 2.81E+00 -9.69E-01 +/- 2.05E+00 -7.07E+00 +/- 6.45E+00 1.12E+00 +/- 4.36E+00 Niobium-95 U U U U 2.27E-01 +/- 1.83E+00 -1.79E-01 +/- 1.48E+00 -1.95E+00 +/- 6.01E+00 -1.45E+00 +/- 3.76E+00 Zinc-65 U U U U

-3.92E+00 +/- 6.37E+00 1.83E+00 +/- 4.52E+00 3.83E+00 +/- 1.62E+01 -1.86E+00 +/- 1.36E+01 Zirconium-95 U U U U arcadis.com 64

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Qtr 1 Qtr 2 Qtr 3 Qtr 4 M-12 Plant Well #11 (pCi/L) (pCi/L) (pCi/L) (pCi/L) 3.34E+00 +/- 5.64E+00 7.65E-01 +/- 4.52E+00 1.10E+00 +/- 1.24E+01 8.79E+00 +/- 1.97E+01 Barium-140 U U U U 3.33E-01 +/- 5.30E+00 5.29E-01 +/- 5.78E+00 -6.21E+00 +/- 1.66E+01 9.09E+00 +/- 1.87E+01 Cerium-144 U U U U 5.37E-01 +/- 8.94E-01 -3.83E-01 +/- 8.15E-01 1.75E+00 +/- 2.89E+00 -3.24E-01 +/- 2.44E+00 Cesium-134 U U U U

-3.06E-01 +/- 1.78E+00 3.88E-01 +/- 8.99E-01 1.04E+00 +/- 2.74E+00 1.60E+00 +/- 2.49E+00 Cesium-137 U U U U 1.83E+00 +/- 1.42E+00 -5.67E-02 +/- 8.66E-01 -7.42E-01 +/- 2.98E+00 -1.22E-01 +/- 2.71E+00 Cobalt-58 UI U U U 9.38E-01 +/- 7.87E-01 3.40E-01 +/- 8.96E-01 -1.56E+00 +/- 3.61E+00 -7.49E-01 +/- 2.87E+00 Cobalt-60 U U U U

-2.14E+00 +/- 2.03E+00 3.63E-01 +/- 1.79E+00 5.70E-01 +/- 4.67E+00 -6.68E-02 +/- 5.60E+00 Iron-59 U U U U

-1.72E+00 +/- 1.95E+00 6.86E-01 +/- 1.58E+00 -4.66E+00 +/- 3.78E+00 1.21E+00 +/- 7.02E+00 Lanthanum-140 U U U U 4.93E-01 +/- 8.35E-01 -6.26E-01 +/- 8.05E-01 -4.22E-01 +/- 2.36E+00 3.90E+00 +/- 2.87E+00 Manganese-54 U U U UI

-3.90E-03 +/- 9.23E-01 6.66E-01 +/- 9.36E-01 -3.09E-02 +/- 3.05E+00 -2.08E+00 +/- 2.53E+00 Niobium-95 U U U U 3.26E+00 +/- 1.82E+00 8.95E-01 +/- 1.85E+00 -1.47E+00 +/- 5.32E+00 1.31E+00 +/- 5.71E+00 Zinc-65 U U U U 9.31E-02 +/- 1.65E+00 -5.69E-01 +/- 1.63E+00 1.56E+00 +/- 4.78E+00 2.96E+00 +/- 5.45E+00 Zirconium-95 U U U U arcadis.com 65

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Qtr 1 Qtr 2 Qtr 3 Qtr 4 M-43 Imholte Farm (pCi/L) (pCi/L) (pCi/L) (pCi/L)

-7.43E+00 +/- 7.59E+00 3.56E-01 +/- 5.64E+00 -2.47E+00 +/- 8.51E+00 5.78E+00 +/- 1.23E+01 Barium-140 U U U U

-8.51E+00 +/- 8.05E+00 -3.90E+00 +/- 1.03E+01 1.13E+00 +/- 1.17E+01 7.64E+00 +/- 1.21E+01 Cerium-144 U U U U 3.32E-01 +/- 1.18E+00 1.18E+00 +/- 1.28E+00 4.43E-01 +/- 2.01E+00 -1.17E+00 +/- 2.04E+00 Cesium-134 U U U U 7.43E-01 +/- 1.08E+00 4.11E-01 +/- 1.12E+00 -9.45E-01 +/- 1.86E+00 -1.32E+00 +/- 1.77E+00 Cesium-137 U U U U

-1.91E-01 +/- 1.09E+00 -1.25E+00 +/- 1.71E+00 9.42E-01 +/- 1.79E+00 -3.71E-01 +/- 1.79E+00 Cobalt-58 U U U U

-9.78E-01 +/- 1.42E+00 -2.91E-01 +/- 1.01E+00 -3.33E-01 +/- 2.37E+00 -4.09E-01 +/- 1.57E+00 Cobalt-60 U U U U

-2.21E-01 +/- 2.37E+00 9.20E-01 +/- 2.47E+00 -1.38E-01 +/- 3.35E+00 2.07E+00 +/- 5.10E+00 Iron-59 U U U U

-1.15E+00 +/- 2.59E+00 1.12E+00 +/- 2.13E+00 -8.89E-01 +/- 2.92E+00 2.49E+00 +/- 4.86E+00 Lanthanum-140 U U U U 1.91E-01 +/- 1.02E+00 -1.12E-01 +/- 1.12E+00 6.47E-01 +/- 1.69E+00 1.98E+00 +/- 1.80E+00 Manganese-54 U U U U

-5.88E-01 +/- 1.23E+00 -6.60E-01 +/- 1.60E+00 -5.17E-02 +/- 1.91E+00 -5.20E-02 +/- 2.32E+00 Niobium-95 U U U U 1.40E+00 +/- 2.54E+00 2.28E+00 +/- 2.23E+00 -1.11E+00 +/- 4.50E+00 -7.97E-01 +/- 4.26E+00 Zinc-65 U U U U

-5.32E-01 +/- 2.03E+00 1.21E+00 +/- 1.75E+00 6.05E-01 +/- 2.70E+00 -4.46E-01 +/- 2.78E+00 Zirconium-95 U U U U arcadis.com 66

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Qtr 1 Qtr 2 Qtr 3 Qtr 4 M-55 Hasbrouck Residence (pCi/L) (pCi/L) (pCi/L) (pCi/L)

-8.29E-01 +/- 7.69E+00 1.82E+00 +/- 4.74E+00 2.46E-01 +/- 1.04E+01 -4.10E+00 +/- 1.34E+01 Barium-140 U U U U 2.17E+00 +/- 5.58E+00 1.69E+00 +/- 5.81E+00 4.24E+00 +/- 1.44E+01 8.68E+00 +/- 1.23E+01 Cerium-144 U U U U 3.00E-01 +/- 9.47E-01 6.50E-01 +/- 9.29E-01 1.98E+00 +/- 2.53E+00 1.48E+00 +/- 2.27E+00 Cesium-134 U U U U

-4.63E-01 +/- 8.97E-01 -5.99E-01 +/- 1.04E+00 -1.55E+00 +/- 2.23E+00 -5.21E-01 +/- 1.78E+00 Cesium-137 U U U U

-7.53E-01 +/- 8.71E-01 3.01E-01 +/- 8.67E-01 1.00E+00 +/- 2.42E+00 5.99E-01 +/- 1.77E+00 Cobalt-58 U U U U

-2.46E-01 +/- 8.68E-01 1.97E-01 +/- 8.31E-01 -1.11E-02 +/- 2.40E+00 3.24E-01 +/- 1.35E+00 Cobalt-60 U U U U

-8.98E-01 +/- 1.92E+00 -7.99E-01 +/- 1.88E+00 1.76E+00 +/- 4.04E+00 -3.34E+00 +/- 4.23E+00 Iron-59 U U U U

-7.62E-01 +/- 1.82E+00 -8.29E-01 +/- 1.72E+00 -5.18E-02 +/- 3.49E+00 -1.22E+00 +/- 4.67E+00 Lanthanum-140 U U U U 6.04E-01 +/- 7.83E-01 7.75E-01 +/- 1.25E+00 -1.67E+00 +/- 2.32E+00 -5.45E-01 +/- 1.87E+00 Manganese-54 U U U U

-1.29E+00 +/- 1.96E+00 -2.01E-02 +/- 1.43E+00 1.16E+00 +/- 2.23E+00 -2.57E-02 +/- 2.19E+00 Niobium-95 U U U U 3.09E-01 +/- 1.95E+00 -5.21E-01 +/- 2.11E+00 3.21E-01 +/- 4.49E+00 3.36E+00 +/- 2.49E+00 Zinc-65 U U U U

-1.33E+00 +/- 1.48E+00 6.99E-01 +/- 1.57E+00 -1.36E+00 +/- 3.38E+00 -5.60E-02 +/- 3.36E+00 Zirconium-95 U U U U arcadis.com 67

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT WATER - DRINKING: GAMMA ISOTOPIC M-14 City of Minneapolis Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

-8.100 14.900 -14.300 -2.520 -4.710

-3.730 +/- 2.410 +/- 6.920 +/- 1.470 +/- 0.958 +/- -9.110 +/- 2.050 +/-

+/- +/- +/- +/- +/-

Barium-140 10.300 9.100 14.000 8.480 6.390 7.090 7.920 13.500 13.400 16.100 21.800 17.700 U U U U U U U U U U U U 14.000 -8.570 2.600 +/- -1.530 0.287 +/- 8.910 +/- 5.410 +/- -1.520 +/- 0.352 +/- -1.480 +/- -2.180 +/- 0.710 +/-

+/- +/-

Cerium-144 6.390 +/- 5.540 6.410 8.930 15.100 13.100 9.420 7.350 7.320 11.000 10.700 17.200 U U U U U U U U U U U U 0.042 +/- -0.293 0.427 +/- -0.639 +/- 0.696 +/- -0.488 -1.290 0.297 +/- -0.696 0.126 +/- 0.532 +/- -0.546 +/-

Cesium-134 0.876 +/- 0.844 0.947 1.310 1.740 +/- 2.410 +/- 3.130 2.200 +/- 1.450 1.120 1.180 1.720 U U U U U U U U U U U U 0.825 +/- -0.026 0.349 +/- -0.114 +/- -0.534 -0.255 2.020 +/- 1.170 +/- -0.073 0.106 +/- 0.797 +/- -0.170 +/-

Cesium-137 0.971 +/- 0.787 0.931 1.240 +/- 1.580 +/- 2.290 3.210 2.060 +/- 1.460 1.170 1.250 1.620 U U U U U U U U U U U U 0.100 +/- -0.028 0.208 +/- 0.186 +/- -0.148 1.180 +/- 0.573 +/- -0.770 +/- -0.918 0.635 +/- -0.090 +/- -0.115 +/-

Cobalt-58 1.050 +/- 0.900 1.140 1.340 +/- 1.600 2.450 3.190 1.780 +/- 1.480 1.090 1.020 1.320 U U U U U U U U U U U U

-0.399 0.155 +/- 0.041 +/- 0.246 +/- -0.767 1.520 +/- 1.100 +/- -0.464 +/- -0.623 -0.112 +/- -0.263 +/- 0.916 +/-

Cobalt-60 +/- 0.956 0.764 1.070 1.300 +/- 1.780 1.920 2.930 1.920 +/- 1.740 1.290 1.040 1.780 U U U U U U U U U U U U

-2.030 -0.312 1.400 +/- -2.220 +/- 0.699 +/- -2.550 0.701 +/- 0.520 +/- -0.075 1.830 +/- -0.059 +/- -0.489 +/-

Iron-59 +/- 2.550 +/- 2.080 2.350 3.650 3.320 +/- 5.860 6.080 4.610 +/- 2.900 2.520 2.280 2.960 U U U U U U U U U U U U

-6.510 -4.580 -1.280 -1.810 +/- -3.200 -0.259 0.907 +/- -3.400 +/- -2.420 4.440 +/- 2.180 +/- -1.760 +/-

Lanthanum-

+/- 4.580 +/- 4.330 +/- 3.670 3.760 +/- 3.890 +/- 8.510 6.960 5.320 +/- 2.660 5.400 1.360 2.660 140 U U U U U U U U U UI U U

-0.992 -0.322 0.262 +/- 0.542 +/- -0.608 -0.556 0.724 +/- 0.594 +/- -0.231 0.300 +/- 0.452 +/- -0.355 +/-

Manganese-

+/- 0.893 +/- 0.778 0.956 1.470 +/- 1.520 +/- 2.630 3.540 2.070 +/- 1.230 1.110 0.939 1.580 54 U U U U U U U U U U U U 0.458 +/- 2.990 +/- -1.970 -1.490 +/- 0.763 +/- 0.970 +/- -0.370 -0.652 +/- 0.268 +/- 0.614 +/- 0.937 +/- 1.570 +/-

Niobium-95 1.110 1.750 +/- 2.250 2.000 1.580 2.540 +/- 3.430 2.460 1.380 1.180 1.260 2.410 U UI U U U U U U U U U U 0.232 +/- 1.220 +/- 0.104 +/- 0.293 +/- 0.900 +/- 1.620 +/- -2.440 0.000 +/- 3.830 +/- 0.934 +/- -0.002 +/- -0.963 +/-

Zinc-65 2.260 1.720 2.100 3.040 3.460 4.000 +/- 6.760 3.480 3.540 2.310 1.930 2.800 U U U U U U U U U U U U 2.010 +/- -0.253 0.684 +/- 0.226 +/- -1.380 -0.703 -0.900 -2.300 +/- -0.572 1.330 +/- 2.140 +/- -0.524 +/-

Zirconium-95 3.300 +/- 1.780 3.360 2.630 +/- 2.740 +/- 3.800 +/- 5.520 3.870 +/- 3.140 2.290 1.980 2.500 U U U U U U U U U U U U 1Monthly composite samples collected in August, October, November, and December continued into the first few days of each subsequent respective month.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT WATER - SURFACE: GAMMA ISOTOPIC M-8 Upstream of Plant pCi/L Jan1 Feb1 Mar Apr May Jun Jul Aug Sep Oct Nov Dec

-36.800 -0.284 +/- 10.300

-1.020 +/- -1.230 +/- -0.804 +/- 5.490 +/- 8.250 +/- 2.760 +/- 17.100 +/-

+/- 7.960 +/-

Barium-140 - - 7.780 12.400 8.920 10.100 21.800 10.200 27.200 111.0002 U 20.600 U U U U U U U U U

-0.159 +/- 0.275 +/- -8.640 +/- -2.570 +/- -4.250 +/- 2.180 +/- 4.440 +/- 2.830 +/- 3.170 +/- -3.440 +/-

Cerium-144 - - 4.500 7.100 15.900 5.710 6.380 15.100 11.300 9.010 5.910 9.090 U U U U U U U U U U

-0.387 +/- 0.604 +/- 0.822 +/- 0.468 +/- -0.187 +/- 0.808 +/- 1.050 +/- -0.400 +/- -0.495 +/- -0.999 +/-

Cesium-134 - - 0.939 1.100 2.360 0.764 1.000 2.000 1.900 1.520 0.822 1.470 U U U U U U U U U U

-0.344 +/- 0.005 +/- -0.735 +/- 0.127 +/- 0.615 +/- 1.800 +/- 4.950 +/- 0.522 +/- 0.089 +/- -0.240 +/-

Cesium-137 - - 0.781 1.360 2.660 0.784 0.963 1.990 2.980 1.300 0.820 1.570 U U U U U U UI U U U

-0.385 +/- 0.013 +/- -0.420 +/- -0.538 +/- -0.519 +/- -0.365 +/- -0.062 +/- -1.850 +/- -0.190 +/- -0.904 +/-

Cobalt-58 - - 0.927 1.100 2.830 0.841 1.040 2.460 1.760 1.680 0.787 1.770 U U U U U U U U U U 0.018 +/- 0.201 +/- 2.180 +/- 0.212 +/- 0.348 +/- 0.563 +/- 0.167 +/- -0.194 +/- -0.062 +/- 0.383 +/-

Cobalt-60 - - 0.766 1.030 2.870 0.846 0.978 1.950 1.670 1.560 0.802 1.270 U U U U U U U U U U

-0.182 +/- -1.150 +/- 7.250 +/- 1.660 +/- -1.040 +/- -4.650 +/- -0.121 +/- -2.030 +/- 0.536 +/- 0.195 +/-

Iron-59 - - 1.890 2.520 9.250 2.120 2.550 6.070 3.640 4.190 1.680 4.580 U U U U U U U U U U 2.360 +/- -1.880 +/- -0.028 +/- -2.760 +/- 1.380 +/- 1.820 +/- -1.700 +/- -3.230 +/- -2.470 +/- -0.411 +/-

Lanthanum-

- - 2.970 3.710 25.4002 2.830 3.890 7.130 3.460 9.110 2.580 8.370 140 U U U U U U U U U U

-0.112 +/- 0.467 +/- -0.933 +/- 0.200 +/- -0.050 +/- -0.296 +/- 1.700 +/- 0.518 +/- 0.442 +/- 2.170 +/-

Manganese-

- - 0.919 1.190 2.260 0.771 0.936 2.050 1.740 1.300 0.716 1.460 54 U U U U U U U U U UI 0.760 +/- 0.624 +/- 0.660 +/- 0.282 +/- 0.564 +/- -0.836 +/- -1.610 +/- -1.120 +/- -0.181 +/- 0.473 +/-

Niobium-95 - - 0.976 1.180 3.280 0.915 1.090 2.690 1.890 1.840 0.884 1.830 U U U U U U U U U U

-0.785 +/- 0.158 +/- 6.990 +/- 0.143 +/- -0.761 +/- -2.260 +/- -3.670 +/- 0.296 +/- 0.755 +/- -0.746 +/-

Zinc-65 - - 1.800 2.480 4.130 1.560 1.920 4.070 4.260 2.990 1.570 3.250 U U U U U U U U U U 1.400 +/- 1.170 +/- 0.531 +/- -0.822 +/- 1.000 +/- 0.211 +/- 1.250 +/- 0.985 +/- 1.070 +/- 0.887 +/-

Zirconium-95 - - 1.590 2.180 4.680 1.620 1.960 3.690 3.300 3.160 1.550 3.600 U U U U U U U U U U Notes:

1 Sample unavailable due to unsafe condition for sampling resulting from frozen river surface.

2 Positive barium-140 results were due to analytical deviations rather than actual detection of MNGP related material. Lanthanum-140 was not detected in any of the water samples. In some cases, the required LLD was not met for barium-140/lanthanum-140. See Section 7.5 for further details.

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2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT M-9 Downstream of Plant pCi/L Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

-6.520 +/- -19.200 -3.610 +/- -5.650 +/- -33.300 0.309 +/- -2.750 +/- 8.620 +/- 6.740 +/- -4.640 +/- -0.563 +/- 0.517 +/-

21.700 +/- 21.100 8.020 19.400 +/- 8.880 9.350 21.700 11.700 23.600 10.200 16.300 Barium-140 U U U U 84.9001 U U U U U U U U

-3.440 +/- 2.850 +/- -6.700 +/- 0.027 +/- -4.600 +/- 1.770 +/- -7.830 +/- 2.220 +/- 4.240 +/- 9.260 +/- -0.907 +/- -8.080 +/-

Cerium-144 6.800 4.320 5.710 11.000 16.000 5.490 7.610 13.300 12.800 11.300 7.320 11.100 U U U U U U U U U U U U 1.010 +/- 0.714 +/- 0.392 +/- 0.076 +/- 0.093 +/- 0.591 +/- -0.286 +/- 2.650 +/- -0.570 +/- -0.347 +/- 0.201 +/- -0.758 +/-

Cesium-134 0.936 0.689 0.798 2.010 2.140 0.746 1.420 2.770 1.920 1.190 0.937 1.950 U U U U U U U U U U U U 0.502 +/- 0.416 +/- 0.569 +/- -1.980 +/- 0.234 +/- -0.264 +/- -0.246 +/- -2.020 +/- 0.305 +/- 0.154 +/- -0.883 +/- -0.460 +/-

Cesium-137 0.869 0.673 0.820 1.610 2.760 0.779 0.796 2.100 1.750 1.100 1.030 1.880 U U U U U U U U U U U U

-0.525 +/- 0.172 +/- -0.494 +/- -0.776 +/- 0.820 +/- -0.174 +/- -0.151 +/- 2.090 +/- -1.810 +/- 0.742 +/- -0.303 +/- -1.280 +/-

Cobalt-58 1.100 0.764 0.813 1.880 3.300 0.825 0.856 3.950 2.390 1.270 1.090 2.040 U U U U U U U U U U U U 0.090 +/- 0.145 +/- 0.383 +/- -0.361 +/- -2.020 +/- -0.185 +/- 0.945 +/- 3.120 +/- 0.720 +/- 0.329 +/- -0.134 +/- 0.341 +/-

Cobalt-60 0.864 0.677 0.834 1.790 2.550 1.190 0.844 2.940 1.930 0.960 1.020 1.760 U U U U U U U U U U U U

-2.680 +/- -1.480 +/- -0.194 +/- -1.550 +/- -6.210 +/- -0.042 +/- 0.835 +/- -2.350 +/- 0.113 +/- 2.100 +/- -1.290 +/- 1.700 +/-

Iron-59 3.000 2.180 1.950 4.110 8.680 1.910 1.980 6.680 3.680 3.670 2.310 4.660 U U U U U U U U U U U U

-1.430 +/- -2.430 +/- -3.880 +/- 1.090 +/- -13.700 -1.100 +/- -2.900 +/- -5.620 +/- 0.408 +/- 1.970 +/- -2.780 +/- 6.850 +/-

Lanthanum- 5.440 3.870 3.220 6.920 +/- 3.300 3.280 7.700 3.690 6.780 3.530 6.080 140 U U U U 33.0001 U U U U U U U U

-1.210 +/- -0.221 +/- 1.190 +/- -0.303 +/- -1.960 +/- 0.168 +/- -0.339 +/- -0.001 +/- 0.852 +/- -0.243 +/- 0.646 +/- -0.728 +/-

Manganese-0.906 0.661 0.993 1.780 2.650 1.580 0.794 2.190 1.830 1.190 0.965 1.670 54 U U U U U U U U U U U U 0.968 +/- -0.199 +/- 0.191 +/- -1.530 +/- -0.927 +/- 0.346 +/- 0.149 +/- 0.527 +/- 0.741 +/- 0.278 +/- 0.713 +/- -0.201 +/-

Niobium-95 1.990 0.881 1.480 1.880 3.600 1.170 0.991 2.380 1.710 1.290 1.070 2.080 U U U U U U U U U U U U

-3.380 +/- 0.262 +/- 0.631 +/- -2.060 +/- 7.070 +/- 0.169 +/- -0.280 +/- -0.963 +/- -0.593 +/- -0.031 +/- -0.541 +/- -0.602 +/-

Zinc-65 3.440 1.510 1.670 2.920 7.690 1.780 1.810 4.090 3.880 2.130 2.420 3.390 U U U U UI U U U U U U U

-0.915 +/- -0.813 +/- 0.344 +/- 0.712 +/- 5.590 +/- -1.200 +/- 0.125 +/- 3.450 +/- 1.740 +/- 0.003 +/- -0.889 +/- -0.301 +/-

Zirconium-95 1.890 1.560 1.550 3.500 6.170 1.560 1.720 4.390 3.450 2.240 2.060 4.000 U U U U U U U U U U U U 1 Positive barium-140 results were due to analytical deviations rather than actual detection of MNGP related material. Lanthanum-140 was not detected in any of the water samples. In some cases, the required LLD was not met for barium-140/lanthanum-140. See Section 7.5 for further details.

arcadis.com 70

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT Data below were analyzed EDC. The results reported relate only to the items tested and to the sample as received by the laboratory. The raw TLD results are corrected for individual element sensitivity and reader sensitivity and determined by QC results. Transit exposures are subtracted and the fade of the thermoluminescent response is compensated. The abbreviations common to each of the EDC analytical results tables are provided below.

Abbreviations ISFSI Independent Spent Fuel Storage Installation TLD Thermoluminescent Dosimeter mR/Std. Qtr Millirem per standard quarter (91 days) arcadis.com 71

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT DIRECT RADIATION - TLD: GAMMA mrem/91 day Qtr 1 Qtr 2 Qtr 3 Qtr 4 Control M01C Kirchenbauer Farm 11.8 +/- 0.7 12.9 +/- 0.6 13.8 +/- 0.8 12.4 +/- 0.7 M02C Cty Rd 4 & 15 12.4 +/- 0.7 12.1 +/- 0.5 13.8 +/- 0.9 12.4 +/- 0.8 M03C Cty Rd 19 & Jason Ave 13.5 +/- 0.6 14.2 +/- 0.5 15.9 +/- 1.3 13.3 +/- 0.5 M04C Maple Lake Water Tower 13.0 +/- 0.6 12.1 +/- 0.4 14.2 +/- 1.1 12.9 +/- 0.5 Inner M01A Sherburne Ave. So. 12.9 +/- 0.8 14.7 +/- 1.1 15.7 +/- 1.0 14.1 +/- 0.9 M02A Sherburne Ave. So. 13.3 +/- 0.6 13.9 +/- 0.9 15.4 +/- 1.1 13.7 +/- 0.8 M03A Sherburne Ave. So. 11.9 +/- 0.5 13.6 +/- 0.8 15.2 +/- 1.1 13.2 +/- 0.6 M04A Biology Station Rd. 12.9 +/- 0.7 12.9 +/- 0.6 15.8 +/- 0.9 12.8 +/- 0.8 M05A Biology Station Rd. 12.9 +/- 0.6 13.4 +/- 0.7 16.1 +/- 0.8 13.2 +/- 0.6 M06A Biology Station Rd. 13.5 +/- 0.6 13.7 +/- 0.8 16.9 +/- 1.2 14.1 +/- 0.5 M07A Parking Lot H 13.5 +/- 0.7 14.0 +/- 0.6 16.9 +/- 0.9 14.0 +/- 0.8 M08A Parking Lot F 13.2 +/- 0.8 13.9 +/- 0.9 17.1 +/- 0.9 14.1 +/- 0.8 M09A County Road 75 13.7 +/- 0.6 13.5 +/- 0.5 16.9 +/- 1.1 13.3 +/- 0.6 M10A County Road 75 12.8 +/- 0.6 13.5 +/- 0.8 15.7 +/- 1.0 14.1 +/- 0.8 M11A County Road 75 14.2 +/- 0.8 14.7 +/- 0.7 17.2 +/- 0.9 14.9 +/- 0.9 M12A County Road 75 13.7 +/- 0.6 14.2 +/- 0.7 16.4 +/- 0.8 (see note 1)

M13A North Boundary Rd. 13.5 +/- 0.7 13.8 +/- 0.8 15.0 +/- 1.2 14.0 +/- 0.6 M14A North Boundary Rd. 13.6 +/- 0.8 14.6 +/- 1.1 16.1 +/- 1.0 14.3 +/- 0.5 Outer M01B 117th Street 12.7 +/- 0.8 13.2 +/- 0.6 14.8 +/- 0.8 13.0 +/- 0.4 M02B County Road 11 13.4 +/- 0.6 14.2 +/- 0.5 15.1 +/- 0.9 13.1 +/- 0.6 M03B County Rd. 73 & 81 10.8 +/- 0.7 11.3 +/- 0.4 13.6 +/- 0.8 11.8 +/- 0.8 M04B County Rd. 73 (196th Street) 12.6 +/- 0.8 13.1 +/- 0.5 14.7 +/- 1.1 12.7 +/- 0.6 M05B City of Big Lake 13.2 +/- 0.9 13.5 +/- 0.6 14.9 +/- 0.9 13.9 +/- 0.5 M06B County Rd 14 & 196th Street 11.7 +/- 0.8 13.4 +/- 0.8 15.2 +/- 0.8 14.0 +/- 0.6 M07B Monticello Industrial Dr. 14.0 +/- 0.7 13.5 +/- 0.6 15.2 +/- 0.9 14.3 +/- 1.0 M08B Residence Hwy 25 & Davidson Ave 13.3 +/- 0.9 12.8 +/- 0.4 14.5 +/- 0.8 13.5 +/- 0.7 M09B Weinand Farm 13.0 +/- 0.6 14.7 +/- 1.0 16.3 +/- 0.9 14.7 +/- 0.9 M10B Reisewitz Farm - Acacia Ave 12.9 +/- 0.8 13.7 +/- 0.8 15.7 +/- 0.9 13.7 +/- 0.8 M11B Vanlith Farm - 97th Ave 12.9 +/- 0.7 14.6 +/- 0.6 16.3 +/- 1.0 14.0 +/- 0.5 arcadis.com 72

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT mrem/91 day Qtr 1 Qtr 2 Qtr 3 Qtr 4 M12B Lake Maria St. Park 13.0 +/- 0.7 13.9 +/- 0.7 16.1 +/- 0.9 14.3 +/- 0.7 M13B Bridgewater Sta. 13.6 +/- 0.7 13.6 +/- 0.7 16.4 +/- 1.1 14.5 +/- 0.8 M14B Anderson Res. - Cty Rd 111 14.4 +/- 0.7 14.8 +/- 0.6 17.1 +/- 0.8 15.3 +/- 0.5 M15B Red Oak Wild Bird Farm 12.6 +/- 0.6 13.4 +/- 0.7 15.7 +/- 0.9 14.4 +/- 0.7 M16B University Ave and Hancock St, Becker 12.7 +/- 0.5 13.0 +/- 0.7 15.0 +/- 1.1 13.0 +/- 0.8 Special Interest I-11 OCA Fence South, on exit road 13.8 +/- 0.7 13.6 +/- 0.5 17.0 +/- 0.7 14.2 +/- 0.5 I-12 OCA Fence Middle, on exit road 13.8 +/- 0.6 13.8 +/- 0.7 16.3 +/- 0.8 13.9 +/- 1.3 I-13 OCA Fence North, on exit road 14.5 +/- 0.9 14.6 +/- 0.8 16.7 +/- 0.9 14.8 +/- 0.8 M01S 127th St. NE 11.5 +/- 0.8 11.0 +/- 0.4 14.1 +/- 0.8 12.0 +/- 0.5 M02S Krone Residence 11.9 +/- 0.8 11.9 +/- 0.7 14.7 +/- 0.9 12.4 +/- 0.7 M03S Big Oaks Park 13.2 +/- 0.8 14.0 +/- 0.7 15.7 +/- 0.8 14.1 +/- 0.5 M04S Pinewood School 14.1 +/- 0.8 14.0 +/- 0.8 16.3 +/- 0.8 14.9 +/- 0.7 M05S 20500 Co. Rd 11, Big Lake 13.3 +/- 0.6 13.1 +/- 0.6 15.8 +/- 1.0 13.4 +/- 0.7 M06S Monticello Public Works 15.1 +/- 0.5 14.3 +/- 0.8 17.4 +/- 0.8 14.8 +/- 0.5 Notes:

1 Location could not be sampled due to missing TLD (Condition Report 501000047634) arcadis.com 73

2020 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT MONTICELLO NUCLEAR GENERATING PLANT DIRECT RADIATION - ISFSI: GAMMA mrem/91 day Type Qtr1 Qtr2 Qtr3 Qtr4 I-01 NE corner of ISFSI Gamma 42.9 +/- 2.9 40.1 +/- 1.7 45.3 +/- 4.0 41.2 +/- 1.7 I-02 North side of ISFSI, center Gamma 37.0 +/- 1.9 34.7 +/- 1.8 40.1 +/- 2.0 37.4 +/- 2.1 I-03 NW corner of ISFSI Gamma 33.3 +/- 1.9 30.3 +/- 2.4 36.8 +/- 1.6 35.0 +/- 2.1 I-04 West side of ISFSI, middle Gamma 102.3 +/- 14.3 81.0 +/- 4.4 84.0 +/- 5.5 80.5 +/- 2.5 I-05 West side of ISFSI, at center of array Gamma 57.9 +/- 4.2 52.0 +/- 4.0 57.7 +/- 3.8 55.9 +/- 3.2 I-06 SW corner of ISFSI Gamma 29.0 +/- 2.0 29.7 +/- 3.1 31.8 +/- 1.5 32.6 +/- 2.3 I-07 South side of ISFSI, center Gamma 34.4 +/- 3.1 31.5 +/- 3.2 37.9 +/- 5.1 32.3 +/- 2.3 I-08 SE corner of ISFSI Gamma 37.4 +/- 4.6 32.3 +/- 4.0 37.3 +/- 4.5 33.7 +/- 4.4 I-09 East side of ISFSI, at center of array Gamma 72.0 +/- 6.7 71.1 +/- 7.2 64.8 +/- 5.7 64.4 +/- 5.4 I-10 East side of ISFSI, middle Gamma 83.4 +/- 4.4 73.9 +/- 5.4 103.8 +/- 9.8 85.6 +/- 3.6 arcadis.com 74

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ML21133A495

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