ML24135A191

2023 Annual Radioactive Effluent Release Report

ML24135A191
Person / Time
Site:	Monticello
Issue date:	05/14/2024
From:	Northern States Power Company, Minnesota, Xcel Energy
To:	Office of Nuclear Reactor Regulation
Shared Package
ML24135A189	List: L-MT-24-014, Offsite Dose Calculation Manual, Revision 9 ML24135A190 ML24135A191 ML24135A192
References
L-MT-24-014
Download: ML24135A191 (1)

Text

(l Xcel Energy

• RESPONSIBLE BY NATURE "'

2023 Annual Radioactive Effluent Release Report For Monticello Nuclear Generating Plant

For the period covering January 1, 2023 through December 31, 2023 Monticello Nuclear Generating Plant Page ii 2023 Annual Radioactive Effluent Release Report

CONTENTS

List of Figures............................................................................................................................ iii List of Tables............................................................................................................................. iv Executive Summary................................................................................................................... 1 Introduction................................................................................................................................ 3 About Nuclear Power.............................................................................................................. 3 About Radiation Dose............................................................................................................. 4 About Dose Calculation.......................................................................................................... 5 Dose Assessment for Operation of MNGP during the 2023 Calendar Year................................ 7 Critical Receptor..................................................................................................................... 7 Offsite Dose due to Gaseous Releases.................................................................................. 8 Offsite Dose Due to Liquid Releases...................................................................................... 9 Dose to Individuals Due to Their Activities Inside the Site Boundary.....................................10 Dose to the Likely Most-Exposed Member of the Public (40 CFR 190)..................................11 Supplemental Information.........................................................................................................12 Abnormal Releases/Discharges.............................................................................................12 Water Storage Pond and Evaporation...................................................................................14 Environmental Monitoring......................................................................................................14 Radioactive Solid Waste Disposal.........................................................................................20 Effluent Radiation Monitors Out of Service for Greater than 30 Days....................................20 Changes to the ODCM..........................................................................................................20 Changes to the Process Control Program (PCP)................................................................... 21 Corrections to Previous ARERRs.......................................................................................... 21 References...............................................................................................................................22 Attachment A: 2023 ARERR Release Summary Tables............................................................23 Attachment B: 2023 REMP TLD Dose Information....................................................................32 Attachment C: Groundwater Monitoring Well Locations............................................................33 Attachment D: 2023 Groundwater Protection Program Well Data.............................................37

fl Xcel Energy Monticello Nuclear Generating Plant Page iii 2023 Annual Radioactive Effluent Release Report

LIST OF FIGURES

Figure 1: Typical Boiling Water Reactor (BWR) design. (US NRC, Ref. [11])............................ 3 Figure 2: Example of a fission reaction. (Wikimedia Commons, Ref. [12])................................. 3 Figure 3: Gaseous Radwaste Treatment System at MNGP....................................................... 4 Figure 4: US Population dose distribution for major sources of exposure. (NCRP Report 160, Ref. [1])...................................................................................................................................... 4 Figure 5: Potential exposure pathways to Members of the Public due to operation of MNGP.... 5 Figure 6: River Water Tritium Sample Results From Specialized Laboratory............................12 Figure 7: Annual Tritium Activity Trends MW-9A from 2009-2023............................................19 Figure 8: MNGP Groundwater Monitoring Well Locations - Overall View (Ref. [9])..................33 Figure 9: MNGP Groundwater Monitoring Well Locations - Site View (Ref. [9]).......................34

fl Xcel Energy Monticello Nuclear Generating Plant Page iv 2023 Annual Radioactive Effluent Release Report

LIST OF TABLES

Table 1: Critical Receptor 2023................................................................................................. 7 Table 2: Critical Receptor Organ Dose...................................................................................... 8 Table 3: Air Dose due to Noble Gases at the Maximum Site Boundary Location....................... 8 Table 4: Liquid Effluent Dose..................................................................................................... 9 Table 5: Maximum Effluent Dose to Individuals due to Their Activities Inside Site Boundary....10 Table 6: Total Dose Due To All Uranium Fuel Cycle Sources (40 CFR 190).............................11 Table 7: Abnormal Release To The Site Environs....................................................................12 Table 8: Modeled Abnormal Discharge From MNGP To Mississippi River................................13 Table 9: Groundwater Monitoring Well Sampling Frequencies..................................................18 Table 10: Annual Tritium Activity Trends MW-9A from 2009-2023............................................19 Table 11: Gaseous Effluents - Summation of All Releases (RG-1.21 Table 1A).......................25 Table 12: Gaseous Effluents - Elevated Releases (RG-1.21 Table 1B)....................................26 Table 13: Gaseous Effluents - Reactor Building Vent & Water Storage Pond Releases (RG-1.21 Table 1C)..........................................................................................................................27 Table 14: Liquid Effluents - Summation of All Releases (RG-1.21 Table 2A)............................28 Table 15: Liquid Effluents (RG-1.21 Table 2B)..........................................................................29 Table 16: Solid Waste and Irradiated Fuel Shipments (RG-1.21 Table 3)................................. 30 Table 17: 2023 REMP TLD Dose Results.................................................................................32 Table 18: MNGP Monitoring Well Locations from FP-CY-GWPP-01. (Ref. [8]).........................35

fl Xcel Energy Monticello Nuclear Generating Plant Page 1 2023 Annual Radioactive Effluent Release Report

EXECUTIVE

SUMMARY

Monticello Nuclear Generating Plant (MNGP) is a Boiling Water Reactor (BWR) located in central Minnesota. The plant releases small quantities of radioactive materials in gaseous form and does not make routine releases of radioactive liquids. Radioactive material in the environment due to plant operations remains below detectible levels, as discussed in the Annual Radiological Environmental Operating Report (AREOR) for MNGP. Technical Specifications limit the quantities of radioactive material that may be released, based on calculated radiation doses or dose rates.

Dose to Members of the Public due to radioactive materials released from the plant is limited by Appendix I of 10 CFR 50 and by 40 CFR 190. Operational doses to the public during 2023 were calculated to be very small compared to the limits required by regulation and compared to other sources of radiation dose and pose no health hazard. Below is a brief summary of the significant sections of the report.

DOSE ASSESS MENT F OR OPERATION OF MNGP IN 2023

The Critical Receptor for MNGP has changed since the last report; the new critical recept or is located at 1.10 miles SE. The Critical Receptor was a Child with dose due to Ground Plane, Inhalation and Vegetable Ingestion pathways. The maximum Annual Organ Dose calculated for this receptor was 0.0328 mrem to the Thyroid. This annual dose is a small fraction of the 10 CFR 50, Appendix I guideline of 15 mrem to the Maximum Organ.

Maximum Gaseous Site Boundary Air Doses were calculated to be 0.00 186 mrad g amma and 0.000646 mrad beta. These doses are also small compared to the 10 CFR 50, Appendix I guidelines for air dose of 10 mrad gamma and 20 mrad beta.

Effluent-related dose to individuals due to their activities inside the site boundary was found to be highest for a hypothetical worker in the subyard or Site Admin Building working 40 hour4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br />s/week.

The maximum organ dose due to gaseous effluents was found to be 0.0202 mrem Thyroid, after taking into account occupancy time.

The leak from the penetration between the Turbine and Reactor Buildings reported in the 2022 ARERR was fixed in March 2023. The total release was quantified at 829,000 +/- 68,100 gallons containing a total activity of 14.0 +/- 1.2 Ci. As a result of migration of the Tritium plume from the penetration leak, MNGP detected Tritium in Monitoring Wells that had the potential to interface with the river. Tritium was first detected in Monitoring Wells 33-A & 37-A on 7/27/23. There are two methods of determining river Tritium loading. The first method is river sampling, performed both upstream, and downstream. Analysis, performed by both in -house labs and third-party vendors with very low detection capability, has shown no detectable Tritium in the Mississippi River above naturally occurring background levels. The second is an analytical method. Using the most widely used and accepted groundwater modeling software and a set of conservative groundwater flow volume assumptions, an abnormal discharge of 0.167 Curies 3H to the Mississippi River between the period of 7/27/23-12/31/23 period was estimated. This is far less than would be present in the river from naturally occurring sources over that period. This highest dose from this release was determined to be 0.0504 mRem to any Child organ at the nearest drinking water source. Out of an abundance of caution, MNGP has also installed a sheet pile wall on the river perimeter as part of the mitigation strategy to minimize any further migration of the source offsite.

fl Xcel Energy Monticello Nuclear Generating Plant Page 2 2023 Annual Radioactive Effluent Release Report

The Likely Most-Exposed Individual due to all Uranium Fuel Cycle O perations for demonstration of compliance with 40 CFR 190 was determined to be the same as the Critical Receptor identified above. The doses received were calculated to be 0.01 12 mrem Whole Body, 0.0337 mrem Thyroid, and 0.0290 mrem Bone (Max Organ other than Thyroid) using Ground Plane, Plume (noble gas), Inhalation and Vegetable Ingestion pathways. The assessment looked at Radiological Environmental Monitoring Program (REMP) Thermoluminescent Dosimeters (TLDs) and found that n o Facility Related Dose was detected at any REMP TLD locations for MNGP in 2023.

ENVIRONMENTAL MONITORING

REMP results for 2023 did not detect radioactive material due to plant operation in offsite samples.

This confirms that impact on the environment and the public due to plant effluents remains very low, consistent with the small dose values reported in the Dose Assessment section.

Two areas of particular interest with regard to environmental monitoring for the present report are TLD and groundwater monitoring. TLD results were analyzed using methodology based on ANSI/HPS N13.37-2014 and found to indicate no Facility Related Dose at, or beyond, the site boundary. This result indicates that direct radiation due to operating the plant or the Independent Spent Fuel Storage Installation (ISFSI) is not contributing measurable dose to people living near the site.

A 2023 4th quarter REMP TLD was positive, but it is not believed to be due to facility dose. It is believed to be the result of the heavy construction in the area. A Monticello RP Technician did a follow-up survey and found a background dose rate of 5 µrem/hr ; there was nothing above background observed at the TLD location and surrounding areas. This condition was captured in MNGP CAP 501000082357; the background of this TLD and the others nearby will need to be reevaluated if this condition persists.

Groundwater monitoring of onsite wells found that seventeen monitoring well locations indicated tritium concentrations above those observed in rainwater captured onsite. The leak to groundwater that started in 2022 and the ensuing migration of the plume has resulted in significant changes in the groundwater. Tritium has been detected in the following wells: MW-4, MW-9, MW-9B, MW-10, MW-12A, MW-12B, MW-13A, MW-15A, MW-16A, MW-16B, MW-23A, MW-29A, MW-30A, MW-31B, MW-33A, and MW-37A. The highest concentration seen on site during the 2023 reporting period was at Monitoring Well 9B, 2,970,000 +/- 7,980 pCi/l. This activity is above the REMP reporting threshold of 30,000 pCi/l per the MNGP ODCM. In total, 10 wells were above the REMP reporting threshold. Tritium was detected in newly developed MW-33A and MW-37A which resulted in MNGP reporting an abnormal discharge to the Mississippi River. There were three Ba-140 Groundwater samples that returned positive results, (MW-12A, MW-30A, MW-37A), and one MW-4 sample Cs-134 result that was positive.

fl Xcel Energy Monticello Nuclear Generating Plant Page 3 2023 Annual Radioactive Effluent Release Report

INTRODUCTION

While many readers of this report will be very familiar with the scientific, design, and operational principles of nuclear power generation, the sections below provide a brief introduction for the reader that may not have a background in the nuclear industry.

A BOUT NUCLEAR POWER

Commercial nuclear power plants are Wais made of generally classified as either Boiling Water concrete and steel Reactors (BWRs) or Pressurized Water 3-6feettliick Reactors (PWRs), based on their design.

(1-1.5 meters)

Monticello Nuclear Generating Plant is classified as a BWR and the discussion below will focus on that technology.

Electricity is generated by a BWR similarly to the way that electricity is generated at other conventional types of power plants, such as those driven by coal or natural gas. Water is boiled to generate steam, the steam turns a turbine that is attached to a generator and the steam is condensed back into water to be returned to the boiler.

Figure 1 shows a schematic representation for a typical BWR. What

Containment Emergency Waler makes nuclear power different from these Structure St4,ply Systems other types of power plants is that the heat FIGURE 1: TYPICAL BOILING WATER REACTOR (BWR) is generated by fission and decay DESIGN. (US NRC, REF. [11] ) reactions occurring within and around the core containing fissionable uranium (U-235).

Nuclear fission occurs when certain nuclides (primarily U-233, U-235, or Pu-239) absorb a neutron and break into several smaller nuclides (called fission products) as well as some additional neutrons. Among the fission products are noble gases, K rypton (Kr) and Xenon (Xe),

which must be removed along with other non-condensable gases (due to air leaks) from the condenser in order to maintain a working vacuum to pull steam across the turbine. Figure 2 shows an example 95Kr of a fission reaction of U-235; of note in the diagram are 3 6 two fission products (Ba-139 and Kr-95), two additional FIGURE 2: EXAMPLE OF A FISSION neutrons produced, and 200 MeV of energy released. REACTION. (WIKIMEDIA COMMONS, REF.

[12] )

fl Xcel Energy Monticello Nuclear Generating Plant Page 4 2023 Annual Radioactive Effluent Release Report

At MNGP, the non-condensable gases are

PLAMT STA.CK treated with the Gaseous Radwaste Treatment System; this system reduces the amount of radioactive material released to the environment by

KJlOUP PIPE SHORT holding gases from the main condenser in compressed gas

ACK DI LUTION tanks for a minimum of 50 AIR

MONITOR 42-NCH PARTICULATE hours to allow for decay of I FUEL I Q-2_ HOLDUP PIP£ FILTER shorter-lived isotopes. The

AIR EJECTORS OM81NER REACTOR VESSEL treated gases are released through the 100- meter Plant Stack. The Plant Stack 5 provides additional dilution time for activity in the plume to

FiPR~~ Ol,;'l,V dissipate prior to reaching the FIGURE 3: GASEOUS RADWASTE TREATMENT SYSTEM AT ground level where people MNGP. could be exposed to the radioactive material that it contains. The Gaseous Radwaste Treatment System includes filtration to reduce particulate and iodine activity that is released; however, because filters are not perfectly efficient, small quantities of particulate, iodine and tritium activity are also released through the Plant S tack. Figure 3 provides a schematic representation of the Gaseous Radwaste Treatment System at MNGP.

ABOUT RADIATION DOSE

Ionizing radiation, including alpha, beta, and gamma radiation from radioactive decay, has sufficient energy to break chemical bonds in tissues and result in damage to tissue or genetic material. The amount of ionization that will be generated by a given exposure to ionizing radiation is quantified as dose. The units for dose Consumer/

oocupa tional / indus tnal are generally given in millirem (mrem) (2%)

in the US. Conven tional radiogra phy/ ftuoroscopy (5%)

The National Council on Radiation Protection (NCRP) has evaluated the lnterventional fluoroscopy population dose for the US and (7%)

determined that the average individual is exposed to approximately 620 mrem per year (Ref. [1]). There are many FIGURE 4: US POPULATION DOSE DISTRIBUTION FOR sources of radiation dose, ranging from MAJOR SOURCES OF EXPOSURE. (NCRP REPORT 160, natural background sources to medical REF. [1] )

fl Xcel Energy Monticello Nuclear Generating Plant Page 5 2023 Annual Radioactive Effluent Release Report

procedures, air travel, and industrial processes. Approximately half (310 mrem) of the average exposure is due to natural sources of radiation including exposure to Radon, cosmic radiation, and internal radiation and terrestrial due to naturally occurring radionuclides. The remaining 310 mrem of exposure is due to man-made sources of exposure, with the most significant contributors being medical (48%) due to radiation used in various types of medical scans and treatments. Of the remaining 2% of dose, most is due to consumer activities such as air travel, smoking cigarettes, and building materials. A small fraction of this 2% is due to industrial activities including generation of nuclear power.

Readers who are curious about common sources and effects of radiation dose that they may encounter can find excellent sources of information from the Health Physics Society, including the Radiation Fact Sheets (http://hps.org/hpspublications/radiationfactsheets.html), and from the US Nuclear Regulatory Commission website (http://www.nrc.gov/about-nrc/radiation.html). The Personal Annual Radiation Dose Calculator on the NRC website can be particularly interesting t o look at (http://www.nrc.gov/about-nrc/radiation/around-us/calculator.html). When the facts are examined, it becomes apparent that the dose to the public due to routine nuclear plant operations is very small when compared to common background and medical sources of radiation exposure.

ABOUT DOSE CALCULATION

ll.h3 Milk, Meat and Concentrations of radioactive material Crop Ingesti,.___ on in the environment resulting from the operation of MNGP are very small and it is not possible to determine doses directly using measured activities of environmental samples. To overcome this, Dose Calculations based on measured activities of effluent streams are used to model the dose impact for FIGURE 5: POTENTIAL EXPOSURE PATHWAYS TO Members of the Public due to plant MEMBERS OF THE PUBLIC DUE TO OPERATION OF operation and effluents. There are MNGP. several mechanisms that can result in dose to Members of the Public, including: Ingestion of radionuclides in food or water; Inhalation of radionuclides in air; Immersion in a plume of noble gases; and Direct Radiation from the ground, the plant or from an elevated plume (See Figure 5).

The MNGP Offsite Dose Calculation Manual (ODCM) specifies the methodology used to obtain the doses in the Dose Assessment section of this report. The methodology in the ODCM is based on NRC Regulatory Guide 1.109 (Ref. [2]) and NUREG-0133 (Ref. [3]). Doses are calculated by determining what the nuclide concentration will be in air, on the ground or in food products based on plant effluent releases. Release points are continuously monitored to quantify what concentrations of nuclides are being released, then meteorological data is used to determine how much of the released activity will be present at a given location outside of the plant either deposited onto the ground or in gaseous form. Intake patterns and nuclide bio-concentration factors are used to determine how much activity will be transferred into animal milk or meat.

Finally, human ingestion factors and dose factors are used to determine how much activity will be consumed and how much dose the consumer will receive. Inhalation dose is calculated by determining the concentration of nuclides and how much air is breathed by the individual.

fl Xcel Energy Monticello Nuclear Generating Plant Page 6 2023 Annual Radioactive Effluent Release Report

Each year MNGP performs a Land Use Census to determine what potential dose pathways currently exist within a five-mile radius around the plant, the area most affected by plant operations. The Annual Land Use Census identifies the locations of vegetable gardens, nearest residences, milk animals and meat animals. The data from the census is used to determine who is likely to receive the highest radiation dose as a result of plant operation.

There is uncertainty in dose calculation results due to modeling atmospheric dispersion of material released and bioaccumulation factors, as well as assumptions associated with consumption and land-use patterns. Even with these sources of uncertainty, the calculations do provide a reasonable estimate of the order of magnitude of the exposure. Conservative assumptions are made in the calculation inputs, including the amounts of various foods and water consumed and the amount of air inhaled, such that the actual dose received is likely lower than the calculated dose. Even with the built in conservatism, doses calculated for the highest hypothetical exposed individual due to plant operation (on the order of less than 1 mrem) are a very small fraction of the annual dose that is received due to other sources that are not related to plant operation (about 620 mrem). The calculated doses due to plant effluents, along with REMP results indicating no identified radioactive material due to plant operations, serve to provide assurance that MNGP is not having a negative impact on the environment or people living near the plant.

fl Xcel Energy Monticello Nuclear Generating Plant Page 7 2023 Annual Radioactive Effluent Release Report

DOSE ASSESSMENT FOR OPERATION OF MNGP D URING THE 2023 CALENDAR YEAR

Below is an assessment of radiation dose due to operation of MNGP during the period of January 1, 2023 through December 31, 2023. The doses calculated represent a small fraction of the dose limits contained in 40 CFR 190 and Appendix I of 10 CFR 50.

CRITICAL RECEPTOR

The Land Use Census for MNGP identifies real exposure pathways for radioactive effluents based on Ingestion (including Gardens, Milk Animals, and Meat Animals), Inhalation and Direct Radiation Exposure (Residence Locations). Inhalation and Direct Radiation Exposure are assumed to exist at all locations, while Ingestion Pathways are assumed only where vegetable gardens, milk animals, or meat animals are actively used for consumption. For any given location and pathway, all age groups are assumed to be present and consume conservative quantities of food products, water, and inhaled air (based on Table E-5 of Regulatory Guide 1.109, Ref. [2]).

The person that is identified as having the largest potential exposure is called the Critical Receptor.

For 2023, the Critical Receptor identified by the MNGP Land Use Census has changed since the last Land Use Census. The Critical Receptor was identified as a Child at a Garden in the SE Sector 1.1 miles away from the plant and the max organ being Thyroid. A factor in the Critical Receptor changing was the update of ODCM-APP-A which provided updated dispersion and deposition values calculated using 2016-2020 data. This Critical Receptor is used for determination of compliance with the dose limits of 10 CFR 50, Appendix I. The Critical Receptor from the 2023 Land Use Census is included as Table 1.

TABLE 1 : CRITICAL RECEPTOR 2023.

SECTOR SE DISTANCE 1.1 miles PATHWAYS Ground Plane, Inhalation, and Vegetable Age Group Child Organ Thyroid

fl Xcel Energy Monticello Nuclear Generating Plant Page 8 2023 Annual Radioactive Effluent Release Report

OFFSITE DOSE DUE TO GASEOUS RELEASES

Critical Receptor dose results below were calculated using the 2023 effluent source term from Table 11 and Table 12. The Critical R eceptor doses include dose from C-14 released between May 1 and September 30, in accordance with the methodology in the MNGP ODCM ; this is because only C-14 released during the growing season will be incorporated into food products that contribute to the calculated dose for the Ingestion pathways. Dose due to noble gases released from the Plant Stack and Reactor Building Vent (RBV) release points have been determined for the SSE site boundary location.

The calculated quarterly and annual doses remain a small percentage of the Guidelines provided in Appendix I to 10 CFR 50.

TABLE 2 : CRITI CAL RECEPTOR ORGAN DOSE 10 CFR 50, % of Max Organ Period Dose* Appendix I Design Guideline Objective Thyroid Q1 0.0137 mrem 0.18%

Thyroid Q2 0.00967 mrem 7.5 mrem/quarter 0.13%

Bone Q3 0.01 73 mrem 0.23%

Thyroid Q4 0.00451 mrem 0.06%

Thyroid Annual 0.0328 mrem 15 mrem/year 0.22%

• Includes dose from Iodines, Particulates, Tritium, and Carbon-14.

TABLE 3 : AIR DOSE DUE TO NOBLE GASES AT THE MAXIMUM SITE BOUNDARY LOCATION Exposure 10 CFR 50, % of Type Period Exposure* Appendix I Design Guideline Objective Q1 0.000612 mrad 0.01%

Q2 0.000 260 mrad 5 mrad/quarter 0.01%

Gamma Air Dose Q3 0.0005 85 mrad 0.01%

Q4 0.000403 mrad 0.01%

Annual 0.00186 mrad 10 mrad/year 0.02%

Q1 0.000 154 mrad0.00 15%

Q2 0.000 0624 mrad10 mrad/quarter0.00 06%

Beta Air Dose Q3 0.000215 mrad 0.002%

Q4 0.000 215 mrad0.002%

Annual 0.000646 mrad 20 mrad/year 0.006%

• Includes dose due to Noble Gases only.

fl Xcel Energy Monticello Nuclear Generating Plant Page 9 2023 Annual Radioactive Effluent Release Report

OFFSITE DOSE DUE TO LIQUID RELEASES

As a result of the continued migration of the Tritium Plume following the abnormal release to the site environs in 2022, MNGP concluded that Tritium had the potential to reach the river. This determination was made after H-3 was detected in Monitoring Wells 33A & 37A on July 27, 2023.

Tritium was subsequently detected in Monitoring Well 48-A, on 8/18/23, via a sample analyzed by MNGPs in-house laboratory. A follow up sample taken 8/23/23 was sent to MNGPs certified vendor laboratory and was below the minimum detectable concentration (MDC). The below analysis used the MW-48A in-house sample as an active interface for the period between the positive sample and the following less than detectable sample.

Our groundwater vendor used their modeling software (MODFLOW) to estimate the amount of activity released to the river. The software modeled the interface between monitoring wells positive for Tritium near the river and the river. This was done to estimate the groundwater exchange rate with the river at those interfaces. Tritium concentration between sample dates was linearly interpolated. A more in-depth explanation is provided in the Abnormal Releases/Discharges section.

A total abnormal discharge for 2023 period was quantified to be 0.167 Ci of Tritium. The max dose was determined to be at the nearest drinking water uptake, the St. Paul Water Intake, 34.2 mi downstream of the plant. The max dose was 0.0504 mrem toany Child Organ.

TABLE 4 : LIQUID EFFLUENT DOSE 10 CFR 50, % of Organ Dose Appendix I Guideline Design Objective Whole Body 0.0504 mrem 3 mrem 1.68%

Max Organ 0.0504 mrem 10 mrem 0.50%

fl Xcel Energy Monticello Nuclear Generating Plant Page 10 2023 Annual Radioactive Effluent Release Report

DOSE TO INDIVIDUALS DUE TO THEIR ACTIVITIES INSIDE THE SITE BOUNDARY

This section evaluates dose to non-occupationally exposed workers that may be onsite for various reasons. Groups of concern include cleaning contractors at the Receiving Warehouse and Site Administrative Building, and Xcel Energy Company Transmission and D istribution (T&D) cr ews working in the subyard. These workers are considered not to be occupationally exposed because the work activities are only remotely related to plant-operational activities. Use of a very conservative assumption of 40 hour4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br />s/week spent inside the site boundary by these groups conse rvatively represents the most-exposed individual.

The annual whole body, skin and organ dose was computed using the 2023 source term using the noble gas dose calculation methodology provided in the ODCM. Elevated finite plume dose factors for the site boundary were used for Plant Stack noble gas total body doses ; these dose factors provide a good approximation of the elevated finite plume dose factors that would be determined at the location of interest. The highest calculated organ dose to non-occupationally exposed workers within the site boundary due to plant effluent releases was determined to be 0.0202 mrem Thyroid for workers in the subyard or Site Administration Building. This computed dose includes a reduction by the factor of 40/168 to account for limited occupancy factor for these individuals. The calculated doses due to gaseous effluents for Whole Body, Thyroid and Skin for non-rad workers onsite are presented in Table 5.

TABLE 5 : MAXIMUM EFFLUENT DOSE TO INDIVIDUALS DUE TO THEIR ACTIVIT IES INSIDE SITE BOUNDARY Organ Dose*

Whole Body 0.0142 mrem Thyroid 0.0202 mrem Max Other Organ (Lung) 0.0146 mrem

• Includes doses due to Gaseous Effluent Releases of Noble Gases, Iodines, Particulates, and Tritium.

Pathways calculated were Inhalation and Direct Radiation due to Elevated Plume and Ground-Plane Deposition.

fl Xcel Energy Monticello Nuclear Generating Plant Page 11 2023 Annual Radioactive Effluent Release Report

DOSE TO THE LIKELY MOST - EXPOSED MEMBER OF THE PUBLIC (40 CFR 190)

Compliance with 40 CFR 190, Environmental Radiation Protection Standards for Nuclear Power Operations, requires controlling dose to any member of the public due to all radiation sources from the uranium fuel cycle below 25 mrem to the whole body, 75 mrem to the thyroid and 25 mrem to any other organ. These limits apply to dose in the general environment outside of the site boundary due to effluents in addition to other sources of dose from the uranium fuel cycle that impact members of the public. In the case of Monticello Nuclear Generating Plant, no other nearby uranium fuel cycle sources are present and only doses due to effluents, direct radiation from the reactor and steam turbines and direct radiation due to the ISFSI are included in the assessment.

In order to determine the maximum exposed individual, it is necessary to determine whether direct radiation dose due to plant operations has been detected outside of the site boundary. MNGP has analyzed the 2023 REMP TLD data using methodology based on ANSI/HPS N13.37-2014 (Ref. [4]) and has determined that facility related radiation dose was not detected for any REMP TLD during 2023. Attachment B summarizes the REMP TLD data for 2023. See Direct Radiation Dose below on pg. 16 for more information on REMP TLDs.

Therefore, the Likely Most-Exposed Member of the Public would be the Critical Receptor identified in the 2023 Land Use Census. D oses due to Iodines, Tritium, Carbon-14, Particulates with > 8-day half-life, and Noble Gases were summed to determine total dose due to gaseous effluents, and the results are reported in Table 6.

TABLE 6 : TOTAL DOSE DUE TO ALL URANIUM FUEL CYCLE SOURCES (40 CFR 190)

Dose Type Organ Dose 40 CFR 190 % of Limits Limit Direct Radiation All Not detected - 0.00%

Dose*

Noble Gases Whole Body 0.00093 mrem - 0.01%

Skin 0.00194 mrem - 0.02%

Particulates, Whole Body 0.0103 mrem - 0.04%

Iodines, Tritium Thyroid 0.0328 mrem - 0.06%

and Carbon-14 Max Other Organ (Bone) 0.0281 mrem - 0.12%

Whole Body 0.0112 mrem 25 mrem 0.05%

Total Dose ** Thyroid 0.0337 mrem 75 mrem 0.07%

Max Other Organ (Bone) 0.0290 mrem 25 mrem 0.13%

• Based on REMP TLD Results, as discussed in the Environmental Monitoring Section below.

• • For the Critical Receptor identified in Table 1, above. Because Direct (TLD) dose is 0.0, then this represents the likely most-exposed individual. Doses in bold include contributions due to Iodines, Particulates, Tritium, Carbon-14, and Noble Gases.

fl Xcel Energy Monticello Nuclear Generating Plant Page 12 2023 Annual Radioactive Effluent Release Report

SUPPLEMENTAL INFORMATION

ABNORMAL RELEASES/DISCHARGES

Monticello Nuclear Generating Plant had an abnormal release to the site environs due to the leak from a penetration between the Turbine and Reactor Buildings. The leak was fixed in March 2023.

Over the period of leakage between November 2022 - March 2023 the total release was quantified to be a volume of 829,000 +/- 68,100 gallons containing a total activity of 14.0 +/- 1.2 Ci. The activity from the nuclides in the release were calculated and provided in Table 7. Due to the uncertainty in the Tritium calculation and the small magnitude of the respective gamma species, the resulting sum appears the same as the Tritium result.

TABLE 7 : ABNORMAL RELEASE TO THE SITE ENVIR O NS Nuclide Activity Released (Ci)

H-3 14.0 +/- 1.2 I-131 0.00090 +/- 0.00026 I-133 0.010 +/- 0.0015 I-135 0.023 +/- 0.0076 Xe -133 0.0027 +/- 0.00058 Xe -135 0.042 +/- 0.0049 Total Activity 14.0 +/- 1.2

As a result of the abnormal release above and the resulting migration of that plume, there was a potential for MNGP to have had an abnormal discharge to the Mississippi River. Monticello collected additional weekly upstream and downstream river samples to send to a specialized laboratory able to detect Tritium with a LLD of 19.3 pCi/l. These results are plotted in Figure 6 below, for results that were less than 19.3 pCi/l, 0 is the plotted value. The black line on 7/27/23 represents the first day of detection in monitoring wells that were near the Mississippi River. Per these results, no plant impact can be seen on the concentration of Tritium (i.e., above natural background level) in the Mississippi River.

70

~ 50 0

S:

_f 40 C

~

c ~ 30 u

C 8 20

10

0 ~- ----1------- --------- - - -+----+-~------- -------..............................

1/ 1/ 2023 2/20/2023 4/11 / 2023 5/3 1/ 2023 7/ 20/ 2023 9/812023 10/28/ 2023 12/ 17/2023 Date of Sam pie

- M-8 Upstream V endor Tritium { pQ/L} - M-9 Down stream V endor Tritium {pCi/ L}

FIGURE 6 : RIVER WATER TRITIUM SAMPLE RESULTS FROM SPECIALIZED LABORATORY fl Xcel Energy Monticello Nuclear Generating Plant Page 13 2023 Annual Radioactive Effluent Release Report

While Monticello did not detect any Tritium resulting from plant activities in the river, on July 27, 2023 Tritium was detected in newly developed Monitoring Wells 33-A & 37-A. It was subsequently detected in Monitoring Well 48-A on 8/18/23, all following samples of MW-48A were less than detectable. This positive result was from MNGPs in-house laboratory; the sample sent to our certified vendor laboratory on 8/23/23 was less than detectable. MW-48A was considered positive and an active interface between the date of the positive sample (8/18/23) and the subsequent vendor laboratory sample (8/23/23) being less than detectable. It is assumed groundwater continuously flows to the river, so our groundwater vendor modeled the flow between the tritium positive monitoring wells near the river and the river such the site could determine if a discharge had occurred.

The groundwater vendor used MODFLOW to determine flux to the river from each respective monitoring well interface. The model assumed each interface extended half the distance to the adjacent monitoring wells in either direction. The flux was calculated daily using the developed model. Tritium concentrations at each well interface were determined daily by linearly interpolating between samples. The wells containing Tritium were considered part of the interface until a sample was taken that was below the minimum detectable concentration. The site installed a Vertically Engineered Barrier (VEB) between the plume and the river from August 2023 -

November 2023, this changed the flux calculations accordingly. The results of the analysis for the modeled abnormal discharge to the Mississippi River are given below in Table 8. The gamma species were only ever detected in MW-9 before decaying away; thus, no abnormal discharge of gamma species is reported. The total activity released was determined to be 0.167 Ci Tritium which resulted in a dose to 0.0504 mrem to any Child organ at the nearest receptor.

TABLE 8 : MODELED ABNORMAL DISCHARGE FROM MNGP TO MISSISSIPPI RIVER Month 3H Activity Discharged (Ci)

July 2023* 0.00401 August 2023 0.0525 September 2023 0.0997 October 2023 0.00865 November 2023 0.00105 December 2023 0.00109 Total 2023 0.167

• July 2023 is the first date of detection, 7/27/23, through the end of the month.

Remediation activities remain in progress to mitigate further abnormal discharges via this pathway. Also, the site continues to work with the vendor to determine any further abnormal discharges and will ensure they are included in the 2024 ARERR.

fl Xcel Energy Monticello Nuclear Generating Plant Page 14 2023 Annual Radioactive Effluent Release Report

WATER STORAGE POND AND EVAPORATION

MNGP has established a new gaseous release point within this reporting period. The site in -

serviced the Water Storage Pond system in August 2023. The Water Storage Pond is designed to hold the pumped groundwater as part of the ongoing Tritium remediation efforts. Over time some of the Tritiated Water within the Storage Pond has naturally evaporated. The site identified this as a new gaseous release point.

Before the Water Storage Pond was placed in service, the site used temporary above ground storage tanks to contain the remediated Tritiated water. The evaporation from these tanks was accounted for as well.

A total of 0.388 Ci of Tritium released via natural evaporation from the temporary tanks and the Water Storage Pond is accounted for during this reporting period.

ENVIRONMENTAL MONITORING

The REMP at MNGP provides additional assurance that there are no significant dose or environmental impacts due to operation of the plant. The MNGP ODCM sp ecifies REMP requirements, including TLD samples for direct radiation exposure, Water Samples (Surface, Ground, and Drinking Water sources), Air sampling for Particulate and Iodine radionuclides, Vegetation and Milk sampling, and sampling of Shoreline Sediments, and Fish. REMP sampling continues to indicate that radionuclides in the environment due to operation of MNGP remain below detectable levels.

A 2023 4th quarter REMP TLD was positive, M01A, but it is not believed to be due to facility dose.

The vendor was contacted and verified the result was accurate. It is believed to be the result of the heavy construction in the area. A Monticello RP Technician did a follow-up survey and found a background dose rate of 5 µrem/hr. There was no indication of anything above background at the TLD location. This condition was captured in MNGP QIM 501000082357; the background of this TLD and the others nearby will need revaluated if this condition persists.

Complete results and analyses for MNGP REMP Sampling in 2023 a re available in the 2023 AREOR for MNGP (Ref. [5]).

fl Xcel Energy Monticello Nuclear Generating Plant Page 15 2023 Annual Radioactive Effluent Release Report

CHANGES IN LAND USE AND NON-OBTAINABLE MILK OR VEGETABLE SAMPLES A single milk cow was located at 3.25 miles in the NNE sector during the 2023 Land Use Census.

This location included milk, meat, and garden ingestion pathways. Discussion with the animals owner indicated that the cow provides enough milk for their use, but not enough extra to reliably obtain the 1-2 gallons per sample period required for analysis. Due to the relatively low deposition parameter, the calculated dose at this location remains lower than the dose at the critical receptor.

ODCM-07.01 (based on NUREG-1302 (Ref. [6])) states that milk samples are required for three locations within 1 mile or three locations where calculated doses are greater than 1 mrem/year.

As stated above the location is greater than 1 mile away and the low dispersion parameter has total calculated dose to infant thyroid by all pathways at 0.01 46 mrem, thu s a milk sample is not required.

Milk samples were not available during 2023 due to the limited milk supply of the animal, as discussed above. The site missed the compensatory June Vegetation sampling; the sample was collected but it was not shipped to the vendor laboratory within the required 3 days (see MNGP QIM 501000075372.) Compensatory samples were collected and analyzed (per ODCM-07.01, Table 1) for July, August, and September.

Corn and Potato sampling was not required because no routine liquid discharges were made during the growing season. Additionally, the Land Use Census found that there are no water use permits for irrigation using water from the Mississippi River within 5 miles downstream of the plant.

fl Xcel Energy Monticello Nuclear Generating Plant Page 16 2023 Annual Radioactive Effluent Release Report

DIRECT RADIATION DOSE MONITORING TLDs are stationed around MNGP to measure the ambient gamma radiation field. Monitoring stations are placed near the site boundary and approximately five (5) miles from the reactor, in locations representing sixteen (16) compass sectors. Other locations are chos en to measure the radiation field at places of special interest such as nearby residences, meeting places and population centers. Control sites are located farther than ten (10) miles from the site, in areas that will not be affected by plant operations.

In order to reliably determine whether direct radiation dose due to plant operation has been detected at or beyond the site boundary, Monticello has analyzed REMP TLDs using methodology based on ANSI/HPS N13.37-2014 (Reference [4]), starting with the 2015 ARERR.

This methodology uses the historical average background TLD dose for each location and the Minimum Differential Dose (MDD) based on the performance of the TLD system to determine if a statistically significant dose due to plant operation has been detected. A table summarizing the 2023 TLD analysis is presented in Attachment B (pg. 32). Complete results for the REMP TLDs are also reported in the AREOR.

Historically, the site used guidance from NUREG-0543, METHODS FOR DEMONSTRATING LWR COMPLIANCE WITH THE EPA URANIUM FUEL CYCLE STANDARD (40 CFR PART 190),

which states in S ection IV, As long as a nuclear plant site operates at a level below the Appendix I reporting requirements, no extra analysis is required to demonstrate compliance with 40 CFR Part 190. This statement remains true, assuming that there are no potentially significant sources of direct radiation dose. With the inclusion of spent fuel storage onsite (ISFSI), it is necessary to verify that direct radiation does not reach a level that would cause the total dose to exceed the 40 CFR 190 limits. Hence, the more reliable ANSI/HPS methodology was implemented in order t o determine direct radiation dose moving forward.

The ISFSI at Monticello Nuclear Generating Plant was constructed west of the plant in 2007. The initial loading campaign was completed in 2008 with 10 Horizontal Storage Modules (HSMs) loaded with spent fuel. I n 2013 an additional five HSMs were loaded with spent fuel. In 2016 one additional HSM was loaded. In 2018 an ISFSI campaign loaded an additional 14 HSMs, bringing the total number of stored modules to 30.

fl Xcel Energy Monticello Nuclear Generating Plant Page 17 2023 Annual Radioactive Effluent Release Report

GROUNDWATER PROTECTION PROGRAM (GWPP)

Onsite groundwater is monitored at MNGP in accordance with the guidance presented in NEI 07-07 (Reference [7]). This initiative was developed by NEI and nuclear industry stakeholders to address a gap in industry guidance and practices for monitoring groundwater and responding to inadvertent releases of radioactive material with the potential to contaminate groundwater. The initiative sets forth voluntary requirements for evaluating and monitoring Systems, Structures and Components (SSCs) with a high risk of contaminating groundwater. Additionally, the guidance specifies reporting requirements for onsite groundwater sample results that exceed REMP reporting thresholds and that all onsite groundwater results ar e reported in either the ARERR (Effluent) or AREOR (REMP) reports.

The current groundwater monitoring program includes 60 monitoring wells and 8 pumping wells at 40 different locations. 20 of the locations include a nested configuration, where one sample is taken at the level of the water table (GWPP locations ending with an A) while a second sample can be taken from deeper water ( GWPP locations ending with a B). A map of groundwater sample locations is provided in Attachment C (pg. 33).

Since the previous report, 41 additional monitoring wells have been developed. As a part of the investigation into the Tritium plume migration, several wells were developed, sampled, and analyzed in Monticellos in-house laboratory. If Tritium was not detected in the newly developed well, it was noted for the site vendors groundwater modeling purposes. These wells were periodically sampled and analyzed in-house for Tritium to verify the plume had not undergone an unforeseen migration. Only the wells sent to our certified vendor laboratory are included in the full 2023 groundwater data in Attachment D (pg. 37). The plume has migrated throughout the site environs resulting in several additional monitoring wells being positive for Tritium that were not previously above detectable concentration.

As a part of the Water Storage Pond installation, Monitoring Wells 101, 102, and 103 have been developed around the pond. This, along with the Water Storage Pond Leak Detection System, ensures that the pond is not leaking into the surrounding groundwater. They ar e only tested for Tritium currently, for there is no pathway for gamma isotopes to these wells. The contents of water transferred to the pond are verified free of gamma nuclides before addition.

The site has also developed pumping wells. Some of these have replaced existing monitoring wells and some are new developments. Monitoring Well 10 and Monitoring Well 13A were over-drilled and converted to Pumping Well 10A (PW-10A) and Pumping Well 13A (PW-13A) respectively. These wells are still sampled as befo re; they are labeled as both in Attachment D.

The purpose of the pumping wells is remediation. Additionally, Pumping Wells 4A, 9A, 16A, and 30A are located near the monitoring well of the same number. There are also Pumping Wells 1 and 22A. The pumping wells are included on the map in Attachment C. The site is pumping the Tritium containing groundwater to the Water Storage Pond where it is then stored (evaporation is accounted for).

The wells are sampled at different frequencies depending on how likely they are to include non-natural activity; Table 9 summarizes the current sampling frequencies for groundwater monitoring wells at MNGP. Wells that have historically read only at background levels and are unlikely to become contaminated are monitored once annually for tritium and gamma-emitting nuclides.

Wells that have historically indicated tritium near background levels but are more likely to include activity from leaks or spills are monitored quarterly for tritium and gamma-emitting nuclides. The

fl Xcel Energy Monticello Nuclear Generating Plant Page 18 2023 Annual Radioactive Effluent Release Report

remaining wells are monitored more frequently to ensure that high-risk SSCs are adequately monitored and that existing activity is characterized with sufficient resolution; these wells are monitored monthly for tritium and quarterly for gamma-emitting nuclides. Several wells are considered sentinel wells that would indicate if radioactive material were migrating offsite into the Mississippi River; these wells are indicated in bold in Table 9, below. As a result of the ongoing response to the abnormal release to the groundwater and resulting migration of the plume, several new monitoring wells were installed downstream (i.e., between the site and the river) of former sentinel wells.

TABLE 9 : GROUNDWATER MONITORING WELL SAMPLING FREQUENCIES.

Tritium Number of Sampling Monitoring Groundwater Monitoring Well Identities*

Frequency Wells

Quarterly 9 MW-1, MW-2, MW-3, MW-4B, MW-11, MW-13B, MW-14, MW-15B, MW-23A, MW-37A

Monthly 12 MW-4, MW-9, MW-9B, MW-10, MW-12A, MW-12B, MW-13A, MW-15A, MW-16A, MW-29A, MW-30A, MW-33A

Annual 16 MW-1B, MW-4B, MW-5, MW-6, MW-7, MW-8, MW-10B, MW-16B, MW-26A, MW-26B, MW-31B, MW-48A, MW-1011, MW-1021, MW-1031

Developed, 24 MW-17A, MW-17B, MW-19A, MW-19B, MW-20A, MW-21A, Not MW-23B, MW-24, MW-27A, MW-27B, MW-28A, MW-28B, Currently MW-29B, MW-30B, MW-31B, MW-33B, MW-37B, MW-48B, Sampled MW-50A, MW-58A, MW-66A, MW-67A, MW-67B, MW-68A

• Locations in BOLD typeface are considered sentinel wells.

1 MW-101, MW-102, MW-103 are tested for Tritium only

Water depths are determined at 33 currently sampled monitoring wells on a monthly basis and the data is used to determine static water levels. The Pumping Wells PW-10A and PW-13A do not have their levels currently determined. Monitoring Wells 101, 102, and 103 currently have their water depth measured on a semi-annual basis. It has been not ed that groundwater generally flows toward the river, but there are fluctuations in the gradient and periods of flow reversal have been observed when river level is particularly high.

Additional sampling performed under the guidance of the GWPP includes sampling water from storm drains. These samples periodically indicate elevated tritium activities due to recapture of tritium from gaseous effluents. Zero samples of the storm drain were above the minimum detectable concentration in 2023. Rain and snow samples taken onsite indicate that tritium is commonly detected in rain water at concentrations historically ranging from approximately 200 pCi/l to nearly 1,000 pCi/l. The highest detected concentrations of tritium in rain and snow samples around MNGP have approached 2,000 pCi/l. The site has also established new rain collection sites around the Water Storage Pond to assess the amount of recapture from the pond as it evaporates. In 2023, the concentration of tritium in rain and snow samples ranged between <193 to 968 pCi/l, with an average of 413 pCi/l.

fl Xcel Energy Monticello Nuclear Generating Plant Page 19 2023 Annual Radioactive Effluent Release Report

Results for 2023 indicate that monitoring well MW-9A contained tritium activities ranging from 174,000 +/- 1,890 pCi/l to 2, 700,000 +/- 7,610 pCi/l, with an average of 800,250 pCi/l. A comparison of peak, average, and the range of tritium concentrations by year in MW-9A is presented in Table 10 and Figure 6, below. The annual averages below include MDA values for cases where activity was <MDA.

TABLE 10: ANNUAL TRITIUM ACTIVITY TRENDS MW-9A FROM 2009-2023.

Peak H-3 Average H-3 Activity Activity

Year MW-9A MW-9A (pCi/l) (pCi/l)......

2009 21,727 9,117 0 C.

- 100,000 +-------------- --H- ------1 2010 21,127 4,549 J:

2011 2,317 549 r, 2012 770 306 5 10,000 _ _, _____ _, _..,. _______ __, _,_ -----,

2013 15,124 4,147 *-+I 2014 5,911 2,522 +I ~

2015 6,493 1,679 c: 1,000 - - ---- --.... ~

Q) 2016 6,559 2,423 (.)

2017 5,306 1,553 C:

2018 4,400 1,252 0 0 100 +---,----,-----r----r----,----,----,----,--~~---r----r----r---r--,

2019 5,850 1,805 2020 1,660 713 An nu a l Range + Pe a k Tritium MW-9A + Ave rage Tritium MW-9A 2021 8,220 2,185 2022 4,220,000 851,329 FIGURE 7: ANNUAL TRITIUM ACTIVITY TRENDS MW-9A 2023 2,700,000 800,250 FROM 2009-2023.

Tritium has been detected in the following wells: MW-4, MW-9, MW-9B, MW-10, MW-12A, MW-12B, MW-13A, MW-15A, MW-16A, MW-16B, MW-23A, MW-29A, MW-30A, MW-31B, MW-33A, and MW-37A. All other monitoring wells indicated activities that were less than 300 pCi/l.

The site had 4 samples in 2023 return positive gamma results. In the 3/21/23 MW-12A sample, Ba-140 was detected at a concentration of 16.6 +/- 14.7 pCi/l. The 8/23/23 MW-30A sample detected Ba-140 at a concentration of 16.6 +/- 18.7 pCi/l. The 08/28/23 sample of MW-37A detected Ba-140 at a concentration of 15.8 +/- 12.1 pCi/l. The MW -4 sample taken 3/21/23 detected Cs-134 at a concentration of 3.03 +/- 2.82 pCi/l. Due to the high uncertainty in each of these results and following samples returning to below MDC, it is the conclusion of the site that no gamma-emitting nuclides were detected related to site operation in 2023. All tritium results were obtained as required. The full 2023 onsite groundwater well monitoring results are presented in Attachment D (pg. 37).

The LLD for groundwater monitoring of tritium at MNGP during 2023 was less than 300 pCi/l, in accordance with station processes and procedures; this LLD is far below the required REMP LLD (2,000 pCi/l) and very far below the REMP reporting threshold for water samples (20,000 pCi/l).

The site has chosen to use this low LLD in order to quickly identify and characterize any potential

fl Xcel Energy Monticello Nuclear Generating Plant Page 20 2023 Annual Radioactive Effluent Release Report

contamination sources. The LLD as reported represents the activity at which there is a 95%

chance that a sample containing that level of activity would be characterized as detected with only a 5% chance that the sample would be characterized as a blank.

The Xcel Energy Groundwater Monitoring Program (Ref. [8]) has established a Baseline Threshold Level for tritium, defined as the 95% Confidence Level determined using Students t test and a statistical mean of ten or more sample results; at this level a sample would be considered to be statistically different from background, based on analytical results. For wells that consistently indicate near or below LLD, the Baseline Threshold Level is 400 pCi/l. The program also provides an Action Level of 3-times the Baseline Threshold Level, or 1200 pCi/l for these wells; at this level, additional action is taken to evaluate the cause of the change in activity and work through the Corrective Action process to address the concern. Tritium was detected in Sentinel Wells which resulted in the abnormal discharge of Tritium being reported as discussed in the Abnormal Releases/ Discharges section of this report.

RADIOACTIVE SOLID WASTE DISPOSAL

During 2023, a total of 76.4 Ci of Solid, Low-Level Radioactive waste was shipped offsite for disposal, which contained purely Class A waste. A total of 17 shipments were made to t wo locations. Tables summarizing types and quantities of waste shipped are included in Attachment A, Table 16.

EFFLUENT RADIATION MONITORS OUT OF SERVICE FOR GREATER THAN 30 DAYS

The Water Storage Pond Transfer System Radiation Monitor was out of service beyond 30 days.

The site has not installed the Water Storage Pond Transfer System Radiation Monitor yet.

However, the monitor and its associated compensatory actions were added to the ODCM so there was governance on how to operate the system until the radiation monitor is installed. The required compensatory samples were collected for operation of the system in batch mode. The current expectation of the site is to have the radiation monitor installed and in-serviced by the end of June 2024.

CHANGES TO THE ODCM

ODCM-01.01, Introduction, was revised to align the definition of an abnormal discharge and abnormal release to that of Reg Guide 1.21 Rev 3 which is the most current industry standard.

The site previously used the terms interchangeably, which is how they are presented in Reg Guide 1.21 Rev 1.

ODCM-02.01, Liquid Effluents & ODCM-03.01, Gaseous Effluents, were both updated to include the Water Storage Pond as a new gaseous release point as well as associated equipment and systems. The initial change included equipment that was not installed on site

ODCM-05.01, Gaseous Effluents Calculations, was updated to include how evaporation from the pond will be determined. Tables 26 and 27 for the RBV WRGMs and the Stack WRGMs respectively, were also updated to correspond with the new X/Q and D/Q values for the site. A

fl Xcel Energy Monticello Nuclear Generating Plant Page 21 2023 Annual Radioactive Effluent Release Report

follow-up change corrected errors within the text of Table 27; the numbers within the table did not change.

ODCM-07.01, Radiological Environmental Monitoring Program, was updated to include a new Figure 1 which showed the location of the new Critical Receptor. REMP TLD M-15B, previously named Red Oak Wild Bird Farm, had its name changed to Barton Ave NW. The TLD location did not change; the bird farm is no longer present at this location.

ODCM-APP-A was updated with new dispersion and deposition (X/Q and D/Q respectively) values using MET data from 2016-2020. The update to ODCM-APP-A also included the parameters for the new gaseous release point, the Water Storage Pond. A follow-up update was performed after an error was found in the X/Q & D/Q report from the vendor. I t was discovered ODCM-APP-A contained zeros for the dispersion parameters for the N, NNE, NE, ENE, E, ESE, SE, and SSE sectors for 2.7 miles short-term Offgas Stack releases. This issue was captured in MNGP QIM 501000077554. The vendor was contacted who confirmed the error and provided an updated report with the missing values. The O DCM was updated to include these values.

CHANGES TO THE PROCESS CONTROL PROGRAM (PCP)

In 2023, Monticello upgraded the resin drying system from the existing equipment (RDS-1000) to a Self-Engaging Resin Dewatering System (SERDS). As part of this project, the Process Control Program (PCP) was revised to update the affected portions to reflect the new equipment. This change did not affect any processes or commitments within the PCP.

CORRECTIONS TO PREVIOUS ARERRS

There is a correction to the 2022 ARERR included with this report. The 2022 ARERR Groundwater Data was corrected to include the detection of gamma isotopes by our vendor laboratory. The samples were previously identified as being below required LLD but above the sites certified vendor laboratorys MDC. This correction fixes the data in Attachment D and the related text in the report.

fl Xcel Energy Monticello Nuclear Generating Plant Page 22 2023 Annual Radioactive Effluent Release Report

REFERENCES

[1] "NCRP Report No. 160: Ionizing Radiation Exposure of the Population of the United States," National Council on Radiation Protection and Measurements, Bethesda, MD, 2009.

[2] "Regulatory Guide 1.109, Rev. 1: Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR 50, Appendix I," U.S. Nuclear Regulatory Commission, Washington, D.C., 1977.

[3] W. C. Burke and F. J. Congel, "NUREG-0133: Preparation of Radiological Effluent Technical Specifications for Nuclear Power Plants," US Nuclear Regulatory Comission, Washington D.C., 1978.

[4] "ANSI/HPS N13.37-2014: Environmental Dosimetry - Criteria for System Design and Implementation," Health Physics Society, McLean, VA, 2014.

[5] Arcadis, "2023 Annual Radiological Environmental Operating Report for Monticello Nuclear Generating Plant," Xcel Energy, Monticello, MN, 2023.

[6] W. W. Meinke and T. H. Essig, "NUREG-1302: Offsite Dose Calculation Manual Guidance:

Standard Radiological Effluent Controls for Boiling Water Reactors," U.S. Nuclear Regulatory Commission, Washington, D.C., 1991.

[7] "NEI 07-07: Industry Ground Water Protection Initiative - Final Guidance Document, Rev.

1," Nuclear Energy Institute, Washington, DC, 2019.

[8] "FP-CY-GWPP-01, "Fleet Groundwater Protection Program"," Xcel Energy (internal procedure), Minneapolis, MN, 2024.

[9] J. de Lambert and W. A. Carlson, Carlson McCain, Inc., Lino Lakes, MN, 2024.

[10] "Offsite Dose Calculation Manual for Monticello Nuclear Generating Plant," Xcel Energy, Monticello, MN.

[11] "Boiling Water Reactors (BWRs)," 15 January 2015. [Online]. Available:

http://www.nrc.gov/reactors/bwrs.html. [Accessed 11 April 2016].

[12] Stefan-XP, "Wikimedia Commons," 23 November 2009. [Online]. Available:

https://commons.wikimedia.org/w/index.php?curid=8540436. [Accessed 16 April 2016].

fl Xcel Energy Monticello Nuclear Generating Plant Page 23 Attachment A: 2023 ARERR Release Summary Tables

ATTACHMENT A: 2023 ARERR RELEASE

SUMMARY

TABLES

Covering the Operating Period of Jan - Dec 2023

Facility: Monticello Nuclear Generating Plant

Licensee: Xcel Energy

License Number: DPR-22

1. Regulatory Limits

a. Fission and activation gases:

1. Quarterly dose at or beyond the site boundary 5 mrad gamma radiation 10 mrad beta radiation

2. Annual dose at or beyond the site boundary 10 mrad gamma radiation 20 mrad beta radiation

b. Iodine-131, Iodine-133, Tritium and Particulates, half -lives >8 days:

1. Quarterly 7.5 mrem to any organ

2. Annual 15 mrem to any organ

c. Liquid Effluents:

1. Quarterly:

1.5 mrem total body 5 mrem to any organ

2. Annual:

3 mrem total body 10 mrem to any organ

2. Maximum Permissible Concentrations

a. Fission and Activation Gases:

10 CFR 20, Appendix B, Table 2, Column 1

b. Iodine-131, Iodine-133, Tritium and Particulates, half -lives >8 days:

10 CFR 20, Appendix B, Table 2, Column 1

c. Liquid effluents:

10 times 10 CFR 20, Appendix B, Table 2, Column 2 2.0E-4 µC i/ml for dissolved and entrained gases

3. Average Energy (Not Applicable)

~ Xcel Energy Monticello Nuclear Generating Plant Page 24 Attachment A: 2023 ARERR Release Summary Tables

4. Measurements and Approximations of Total Radioactivity

a. Noble Gases:

Gross noble gas activity released from Reactor Building Vent and Plant Stack exhaust streams is continuously monitored for variation in release rate. Weekly gamma isotopic analysis is performed on grab samples from exhaust streams. Releases from the Plant Stack are modeled to account for varying noble gas concentrations due to decay tank releases; this methodology was implemented at the site in January 2018 in order to improve the accuracy of noble gas release and dose estimates. The uncertainty estimate for noble gas releases was increased to +/-50% in 2019; this accounts for the estimated uncertainty in the noble gas release model along with other uncertainties associated with sampling and counting. 75% of the noble gases released in 2019 consist of Xe-137, Xe-133, and Xe -135; these gases are affected by increased uncertainty due to low concentration (Xe-137), wide variation in concentration (Xe-133) and periodic increases in activity (Xe-135).

b. Iodines in Gaseous Effluent:

Continuous sampling using charcoal cartridges with isokinetic sample flow drawn from Reactor Building Vent and Plant Stack exhaust streams. Weekly gamma isotopic analysis.

c. Particulates in Gaseous Effluent:

Continuous sampling using particulate filters with isokinetic sample flow drawn from Reactor Building Vent and Plant Stack exhaust streams. Weekly analysis for gamma isotopic and gross alpha. Gross alpha samples are decayed for approximately 9 days prior to analysis to allow for decay of natural activity. Quarterly composites are analyzed for Sr-89 and Sr -90.

d. Tritium in Gaseous Effluent:

Monthly grab samples from Reactor Building Vent and Plant Stack exhaust streams followed by liquid scintillation counting.

e. Liquid Effluents Tank sample analyzed prior to each planned release and continuous monitoring of gross activity during planned release.

5. Batch Releases

a. Liquid

1. Number of batch Releases 0

2. Total time period for batch releases 0 min

3. Maximum time period for a batch release 0 min

4. Average time period for a batch release 0 min

5. Minimum time period for a batch release 0 min

6. Average rive r flow during release N/A cfm

b. Gaseous

1. Number of batch Releases 5

2. Total time period for batch releases 4030.0 min

3. Maximum time period for a batch release 1617.0 min

4. Average time period for a batch release 806.5 min

5. Minimum time period for a batch release 59.0 min

6. Abnormal Releases

a. Liquid

1. Number of releases: 6

2. Total activity released: 1.67 E-01 Ci

b. Gaseous

1. Number of releases: 0

2. Total activity released: 0 Ci

~ Xcel Energy Monticello Nuclear Generating Plant Page 25 Attachment A: 2023 ARERR Release Summary Tables

Table 11: Gaseous Effluents - Summation of All Releases (RG-1.21 Table 1A)

Type of Effluent Units Qtr 1 Qtr 2 Qtr 3 Qtr 4 Est. Total Error,

A. Fission & Activation Gases

1. Total Release Curies 2.65E+01 1.29E+01 1.67E+01 1.57E+01 5.00E+01

2. Average Release Rate for Period µCi/sec 3.40E+00 1.64E+00 2.10E+00 1.97E+00

3. Percent of Applicable Limit % 1.19E-02 5.15E-03 1.12E-02 7.84E-03

B. Iodines

1. Total Iodine-131 Curies 1.10E-03 3.98E-04 5.50E-04 4.04E-04 3.20E+01

2. Average Release Rate for Period µCi/sec 1.41E-04 5.06E-05 6.92E-05 5.08E-05

3. Percent of Applicable Limit % 1.10E-01 3.98E-02 5.50E-02 4.04E-02

C. Particulates

1. Total Particulates (Half-lives > 8 days) Curies 1.45E-04 2.93E-04 2.07E-04 2.22E-04 4.00E+01

2. Average Release Rate for Period µCi/sec 1.87E-05 3.72E-05 2.60E-05 2.79E-05

3. Percent of Applicable Limit % 4.95E-03 1.06E-02 5.89E-03 8.34E-03

4. Gross Alpha Activity Curies 3.64E-07 5.53E-07 6.23E-07 3.83E-07 5.00E+01

D. Tritium

1. Total Release Curies 4.91E+00 3.78E+00 4.20E+00 4.37E+00 3.30E+01

2. Average Release Rate for Period µCi/sec 6.31E-01 4.80E-01 5.28E-01 5.50E-01

3. Percent of Applicable Limit % 9.72E-03 7.32E-03 1.15E-02 1.65E-02

E. Carbon-14

1. Total Release Curies 2.01E+00 1.21E+00 1.81E+00 1.73E+00 N/A

~ Xcel Energy Monticello Nuclear Generating Plant Page 26 Attachment A: 2023 ARERR Release Summary Tables

Table 12: Gaseous Effluents - Elevated Releases (RG-1.21 Table 1B)

Continuous Mode Batch Mode

Nuclides Released Units Qtr 1 Qtr 2 Qtr 3 Qtr 4 Qtr 1 Qtr 2 Qtr 3 Qtr 4

1. Fission and Activation Gases Ar-41 Curies 2.42E-02 1.24E-02 8.94E-02 2.50E-02 9.49E-03 1.13E-02 0.00E+00 0.00E+00

Kr-85M Curies 1.84E-01 2.00E-01 2.39E-01 1.15E-01 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Kr-87 Curies 3.08E-01 2.46E-01 2.35E-01 1.62E-01 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Kr-88 Curies 4.41E-01 5.05E-01 5.46E-01 3.23E-01 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xe-133 Curies 9.54E+00 4.22E+00 5.26E+00 5.47E+00 5.02E-03 0.00E+00 0.00E+00 0.00E+00 Xe-133m Curies 2.76E-01 4.24E-02 5.85E-02 9.37E-02 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xe-135 Curies 2.45E+00 1.70E+00 2.81E+00 1.56E+00 9.22E-04 1.49E-03 0.00E+00 0.00E+00 Xe-135m Curies 2.68E+00 1.23E+00 1.70E+00 1.82E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xe-137 Curies 4.68E+00 1.86E+00 1.57E+00 1.87E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xe-138 Curies 4.98E+00 2.67E+00 2.85E+00 3.38E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

Total for Period Curies 2.56E+01 1.27E+01 1.53E+01 1.48E+01 1.54E-02 1.28E-02 0.00E+00 0.00E+00

2. Iodines I-131 Curies 3.81E-04 2.59E-04 4.55E-04 3.36E-04 0.00E+00 2.61E-08 0.00E+00 0.00E+00 I-132 Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 7.42E-08 0.00E+00 0.00E+00 I-133 Curies 2.68E-03 1.93E-03 3.17E-03 2.52E-03 5.52E-08 8.00E-08 0.00E+00 0.00E+00 I-135 Curies 4.19E-03 3.00E-03 5.04E-03 4.06E-03 0.00E+00 1.21E-07 0.00E+00 0.00E+00

Total for Period Curies 7.25E-03 5.19E-03 8.67E-03 6.92E-03 5.52E-08 3.01E-07 0.00E+00 0.00E+00

3. Particulates Ag-110m Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 1.03E-08 0.00E+00 0.00E+00 0.00E+00 Ba-140 Curies 2.44E-05 2.04E-05 2.64E-05 2.22E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Co-58 Curies 1.99E-07 8.16E-07 6.74E-08 1.61E-08 0.00E+00 6.72E-09 0.00E+00 0.00E+00 Co-60 Curies 1.63E-06 5.30E-06 2.29E-06 1.08E-06 0.00E+00 3.34E-08 0.00E+00 0.00E+00 Cr-51 Curies 9.10E-07 4.48E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Cs-137 Curies 4.89E-08 1.01E-06 2.55E-07 2.09E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Fe-59 Curies 0.00E+00 2.57E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Mn-54 Curies 1.84E-07 8.75E-07 2.08E-07 1.64E-07 1.61E-08 0.00E+00 0.00E+00 0.00E+00 Os-191 Curies 7.94E-07 4.08E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Sr-89 Curies 8.03E-06 3.31E-05 8.53E-06 7.58E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Sr-90 Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zn-65 Curies 0.00E+00 4.54E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

Total for Period Curies 3.62E-05 6.71E-05 3.78E-05 3.12E-05 2.64E-08 4.02E-08 0.00E+00 0.00E+00

4. Tritium

H-3 Curies 4.71E-01 7.03E-01 9.45E-01 1.10E+00 0.00E+00 4.33E-03 0.00E+00 0.00E+00

5. Carbon-14

C-14 Curies 2.01E+00 1.21E+00 1.81E+00 1.73E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

~ Xcel Energy Monticello Nuclear Generating Plant Page 27 Attachment A: 2023 ARERR Release Summary Tables

Table 13: Gaseous Effluents - Reactor Building Vent & Water Storage Pond Releases (RG-1.21 Table 1C)

Continuous Mode Batch Mode

Nuclides Released Units Qtr 1 Qtr 2 Qtr 3 Qtr 4 Qtr 1 Qtr 2 Qtr 3 Qtr 4

1. Fission and Activation Gases Xe-133 Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 2.31E-04 Xe-135 Curies 3.18E-01 1.83E-01 6.69E-01 8.73E-01 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xe-135m Curies 5.73E-01 0.00E+00 6.98E-01 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

Total for Period Curies 8.91E-01 1.83E-01 1.37E+00 8.73E-01 0.00E+00 0.00E+00 0.00E+00 2.31E-04

2. Iodines I-131 Curies 7.16E-04 1.39E-04 9.56E-05 6.80E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 I-133 Curies 6.36E-03 5.65E-04 7.94E-04 4.93E-04 0.00E+00 0.00E+00 0.00E+00 0.00E+00 I-135 Curies 1.66E-02 0.00E+00 0.00E+00 5.04E-04 0.00E+00 0.00E+00 0.00E+00 0.00E+00

Total for Period Curies 2.36E-02 7.04E-04 8.90E-04 1.07E-03 0.00E+00 0.00E+00 0.00E+00 0.00E+00

3. Particulates Ag-110m Curies 0.00E+00 0.00E+00 9.42E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Ba-140 Curies 5.36E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Co-58 Curies 1.43E-06 2.34E-05 2.10E-05 3.97E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Co-60 Curies 1.63E-05 1.21E-04 4.42E-05 6.89E-05 0.00E+00 0.00E+00 0.00E+00 2.68E-07 Cr-51 Curies 0.00E+00 2.61E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Cs-137 Curies 3.15E-05 4.80E-06 3.89E-06 2.85E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Mn-54 Curies 2.83E-06 1.75E-05 1.86E-06 2.09E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Os-191 Curies 0.00E+00 3.02E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Sb-124 Curies 0.00E+00 1.09E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Sr-89 Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Sr-90 Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zn-65 Curies 3.35E-06 1.92E-05 3.95E-06 3.22E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00

Total for Period Curies 1.09E-04 2.26E-04 1.69E-04 1.90E-04 0.00E+00 0.00E+00 0.00E+00 2.68E-07

4. Tritium

H-3 Curies 4.43E+00 3.07E+00 3.25E+00 3.27E+00 0.00E+00 0.00E+00 0.00E+00 1.99E-04

5. Carbon-14

C-14 Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

~ Xcel Energy Monticello Nuclear Generating Plant Page 28 Attachment A: 2023 ARERR Release Summary Tables

Table 14: Liquid Effluents - Summation of All Releases (RG-1.21 Table 2A)

Type of Effluent Units Qtr 1 Qtr 2 Qtr 3 Qtr 4 Est. Total Error,

A. Fission & Activation Products

1. Total Release (not including Tritium, Gases, and Alpha) Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 2.50E+01

2. Average Diluted Concentration During Period µCi/ml 0.00E+00 0.00E+00 0.00E+00 0.00E+00

3. Percent of Applicable Limit % 0.00E+00 0.00E+00 0.00E+00 0.00E+00

B. Tritium

1. Total Release Curies 0.00E+00 0.00E+00 1.56E-01 1.08E-02 2.50E+01

2. Average Diluted Concentration During Period µCi/ml 0.00E+00 0.00E+00 1.29E-05 3.36E-06

3. Percent of Applicable Limit % 0.00E+00 0.00E+00 1.29E+00 3.36E-01

C. Dissolved and Entrained Gases

1. Total Release Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 2.50E+01

2. Average Diluted Concentration During Period µCi/sec 0.00E+00 0.00E+00 0.00E+00 0.00E+00

3. Percent of Applicable Limit % 0.00E+00 0.00E+00 0.00E+00 0.00E+00

D. Gross Alpha Radioactivity

1. Total Release Curies 0.00E+00 0.00E+00 0.00E+00 0.00E+00 2.50E+01

E. Waste Volume Released (Pre-Dilution) Liters 0.00E+00 0.00E+00 1.21E+07 3.21E+06 2.50E+01 F. Volume of Dilution Water Used Liters 0.00E+00 0.00E+00 0.00E+00 0.00E+00 2.50E+01

~ Xcel Energy Monticello Nuclear Generating Plant Page 29 Attachment A: 2023 ARERR Release Summary Tables

Table 15: Liquid Effluents (RG-1.21 Table 2B)

Continuous Mode Batch Mode

Nuclides Released Units Qtr 1 Qtr 2 Qtr 3 Qtr 4 Qtr 1 Qtr 2 Qtr 3 Qtr 4 H-3 Curies 0.00E+00 0.00E+00 1.56E-01 1.08E-02 0.00E+00 0.00E+00 0.00E+00 0.00E+00

Total for Period Curies 0.00E+00 0.00E+00 1.56E-01 1.08E-02 0.00E+00 0.00E+00 0.00E+00 0.00E+00

~ Xcel Energy Monticello Nuclear Generating Plant Page 30 Attachment A: 2023 ARERR Release Summary Tables Table 16: Solid Waste and Irradiated Fuel Sh ipments (RG-1.21 Table 3)

A. Solid Waste Shipped Offsite for Burial or Disposal

1. Type of waste Waste Unit 1/1/2023 - Est. Total Major Nuclides for this waste type:

Class 12/31/2023 Error, %

ft3 1.25E+03 H-3, C-14, Mn-54, Fe-55, Co-58, Co-60, Ni-63, Zn-65, Sr-90,

a. Spent Resins, Filters, and m3 3.55E+01 2.50E+01 Nb-95, Tc-99, Ag-110m, I-129, Cs-137, Pu-238, Pu-239, Pu -

Evaporator Bottoms A Ci 7.62E+01 240, Pu-241, Am -241, Cm -242, Cm -243

ft3 1.50E+04 H-3, C-14, Cr-51, Mn-54, Fe-55, Co-58, Co-60, Ni-63, Zn-65,

b. Dry Active Waste (DAW) A m3 4.23E+02 2.50E+01 Sr-90, Zr-95, Nb-95, Tc-99, Ag-110m, I-129, Cs -137, Ce-141, Ci 2.33E-01 Pu-238, Pu -239, Pu-240, Pu-241, Am-241, Cm -242, Cm-243

ft3 0.00E+00 A m3 0.00E+00 2.50E+01

c. Irradiated Components Ci 0.00E+00 ft3 0.00E+00 C m3 0.00E+00 2.50E+01 Ci 0.00E+00 ft3 0.00E+00

c. Other Wastes A m3 0.00E+00 2.50E+01 Ci 0.00E+00 Sum of All Low-Level Waste ft3 1.62E+04 H-3, C-14, Cr-51, Mn-54, Fe-55, Co-58, Co-60, Ni-63, Zn-65, Shipped from the Site All m3 4.59E+02 2.50E+01 Sr-90, Nb-95, Tc-99, Ag-110m, I-129, Cs-137, Ce-141, Pu-Ci 7.64E+0 1 238, Pu-239, Pu-240, Pu-241, Am -241, Cm-242, Cm-243

2. Estimate of major nuclide composition (by type of waste)

Nuclide Abundance, %

Type of waste Name Activity (Ci)

(1.0% cutoff)

Mn-54 5.95% 4.53E+00

Fe-55 30.1% 2.29E+01

Co-58 2.35% 1.79E+00

a. Spent Resins, Filters, and Co-60 52% 3.96E+01 Evaporator Bottoms Ni-63 1.38 1.05E+00

Zn-65 4.33% 3.30E+00

Cs-137 2.26% 1.72E+00

Mn-54 6.36% 1.48E-02

Fe-55 13.74% 3.21E-02

b. Dry Active Waste (DAW) Co-58 1.96% 4.56E-03

Co-60 71.81% 1.68E-01

Zn-65 3.21% 7.48E-03

~ Xcel Energy Monticello Nuclear Generating Plant Page 31 Attachment A: 2023 ARERR Release Summary Tables Table 16: Solid Waste and Irradiated Fuel Shipments (RG -1.21 Table 3) (Continued)

3. Solid Waste Dispositio n

Number of Shipments Mode of Transportation Destination

Waste Control Specialists LLC

3 Interstate Ventures, Inc. Compact Waste Facility

Andrews, TX

UniTech Services Group

14 Xcel Energy Trucking Oak Ridge Service Center

Oak Ridge, TN

B. Irradiated Fuel Shipments (Disposition)

There were no shipments of irradiated fuel from MNGP in 2023.

~ Xcel Energy Monticello Nuclear Generating Plant Page 32 Attachment B: 2023 REMP TLD Dose Information

ATTACHMENT B : 2023 REMP TLD DOSE INFORMATION

TABLE 17: 2023 REMP TLD DOSE RESULTS.

Dose Determinatio n for onlice llo Nud ea r G ene ra. *ng Plant. O perations in 2D23.

A rmua 1 Quarte rly Norma lized Quarter ly Annual Fac ility Basel ine, Mcmito nin g Data, QuarterlyFacil ily Do -se, Annual Mon ito ring Dose.,

B.li Me FrMcrBe Basel ine, Data., M,. F.o. = M..,.a..,

(mrem) (mrem per standa rd q.u:arlerl (mrem) B,. (m rem ) (m reinv (mreml Q2-Q1 Q4 Q1 Q2 QG Q4 0 1 Q2 03 04 M D1A 13.2 1 5.1 12. B 14. B 17. 9 25.3 ND ND ND 110.2 " 5B.5 7D. 8 12.3" M D2A -14. 2 1 6.1 12.4 14. 6 16.7 15.1 ND ND ND ND 62.6 5B.8 ND M OOA 13.9 1 5.7 11. 1 14. 5 15.6 14.7 ND ND ND ND 6 1.D 55. 9 ND M D4A 13. 1 1 5.6 10.B 13.2 15.3 12.7 ND ND ND ND 59.B 52.0 ND M D5A 13.2 1 5.9 10. 1 13.5 15.7 13.5 ND ND ND ND 6D.B 52.8 ND

QI M OOA 14. 1 1 6. 1 10.5 14. 7 16.7 14.5 ND ND ND ND 62.4 56..4 ND il M D7A 113.9 15.9 10.4 13.4 15.2 14.2 ND ND ND ND 6 1.4 53.2 ND L M OOA 1

,i, 10. 9 15.5 14.2 ND ND ND ND 6 1.5 54. 5 ND 13.9 15.8 13.9

.5 M D9A 114. 3 1 5.8 10.6 14. 5 15.7 15.1 ND ND ND ND 6 1.5 55. 9 ND M 10A -14. 3 1 6.4 10.6 14. 3 15.7 14.6 ND ND ND ND 63.4 55. 2 ND M 11A 15.4 1 6.9 l=:J 13.9 17.5 14.8 =::::=] ND ND ND 66..D 6 1.5 ND M 12A. 15. 5 17.1 12. D 14. 2 15.3 15.2 ND ND ND ND 66..5 56..6 ND M 13A 113.6 14.6 l::::::::J 1 1.3 12.7 11.8 :::::J ND ND ND 57. 3 417. 7 ND M 14A -14. 3 1 6.3 12. 5 15. 2 17.2 16.0 ND ND ND ND 63.4 6D. 9 ND M D11S 14. 3 1 5.4 10.. 2 13.3 17. 3 13.9 ND ND ND ND 6D. 7 54. 7 ND M D2S 14. 6 1 5.4 11. 1 13. 3 17. 7 14.'I ND ND ND ND 60.B 56..5 ND M OO S 12.2 12.9 10. 1 10. 9 16. 1 12.1 ND ND ND ND 5D. 9 4 9.1 ND M D4S 12.9 14.4 102 12.5 17. 1 13.2 ND ND ND ND 56.. 1 53. 0 ND M D5S 14. 6 16.0 11. 5 13.D 19.2 14.1 ND ND ND ND 62.5 57. 9 ND M OO S 12.B 1 5.4 l=:=J 13. 7 19.0 14.6 =::::=] ND ND ND 5B.B 62.9 ND Q) M D7i8 15. 3 16.1 11. 7 13.7 17.8 14.2 ND ND ND ND 63.5 57. 3 ND I~ M OOS 13. 6 14.8 11. 7 -13.6 15. 1 12.9 ND ND ND ND 5B.D 53. 3 ND L

$ M OOS 142 16.7 10.B 15. D 17.6 14.3 ND ND ND ND 64. 3 57. 6 ND :::, M 10S 14. 5 16.0 0 9. 9 13. B 16.0 14.0 ND ND ND ND 62.5 53. 6 ND M 111S -13. 9 1 6.0 10. 1 -14. 7 16.3 14.7 ND ND ND ND 6 1.B 55. 7 ND M 12 S -13. 5 1 5.6 10. 1 -14.4 15.8 14.4 ND ND ND ND 6D. 3 54. 7 ND M 13 S -13. 5 14.4 12.D 13.7 16.3 14.3 ND ND ND ND 56..6 56. 2 ND M 14S -13.4 15.5 11. 6 14.4 16.5 14.5 ND ND ND ND 59. 9 57. 0 ND M 15S 113. 5 1 5.0 10..2 13.7 15.0 13.1 ND ND ND ND 5B.4 52.0 ND M 16S 13.D 13.5 10.4 13. 1 15. 1 13.6 ND ND ND ND 53.4 52.3 ND li M D2S '11. 5 12.7 10.D,11.4 14.4 11. 8 ND ND ND ND 4 9. 7 4!7. 6 ND M D1S 112. 1 13.3 10. 1 rn. 7 16.3 12. 5 ND ND ND ND 5 1. 7 4 9. 6 ND i; M OOS 13.6 15.3 11.4 13. 9 15.8 14.9 ND ND ND ND 59.4 56.0 ND 14. 3 15.8 11. 5 -

,j M D4S 1 14. 3 16.8 13.9 ND ND ND ND 6 1. 7 56.5 ND

i/j M OOS -t M 05S 14. 1 15.3 11. 6 13. 6 15.4 13.7 ND ND ND ND 6D. 1 54. 3 ND

15. 9 16.9 12. 9 -14. 1 15.8 15.6 ND ND ND ND 66..6 5B. 4 ND M!l1C 14. D 14.8 9. 9 -12.5 14.4 13.5 ND ND ND ND 5B.4 5D. 3 ND 2 t.Hl2C 14. D 15.6 102 -j t.HIJC 15. 3 16.3 11. 9 13.9 12.2 ND ND ND ND 6D.Q 4B. 1 ND

(.), !l4C 1 11 2 13.4 15.3 13.4 ND ND ND ND 64. 3 53.3 ND 14. 1 14.8 9. Q -12.3 13.8 12.9 ND ND ND ND 5B. 7 4 B.8 ND lt.lDDo 4. 7 1

!t.lDD., 1 1.2 1

ND = Not Detected, where MQ (BQ + MDDQ) or MA (BA + MDDA) for quarterly and annual data, respectively.

• = TLD missing in the field.

^ = TLD was positive, not believed to be due to facility dose, see MNGP QIM 501000082357 MDDQ and MDDA were determined using ten years of REMP TLD Data from 2001 through 2010. (See ANSI/HPS N13.37-2014(Ref. [4]) for details on the methodology for determining facility related dose using REMP TLDs.)

(/,, Xcel Energy Monticello Nuclear Generating Plant Page 33 Attachment C: Groundwater Monitoring Well Locations

ATTACHMENT C: GROU NDWATER MONITORING WELL LOCATIONS

XC EL ENER G Y, IN C. MONTICELLO NUCLEAR GENERATING FIGURE 1 400 2807 West County Road 7 5 PLANT WELL LOCATIONS WELL LOCATIONS

~ Xcel En ergy

• Feet Mont ice llo, MN 55362 Mont ice llo Nuclear Generating Plant (04/10/2024)

Monticello, Min nesota

FIGURE 8 : MNGP GROUNDWATER MONITORING WELL LOCATIONS - OVERALL VIEW (REF. [9]).

(/,, Xcel Energy Monticello Nuclear Generating Plant Page 34 Attachment C: Groundwater Monitoring Well Locations

FIGURE 9 : MNGP GROUNDWATER MONITORING WELL LOCATIONS - SITE VIEW (REF. [9] ).

Monticello Nuclear Generating Plant Page 35 Attachment C: Groundwater Monitoring Well Locations

T ABL E 18: MNGP MONITORING WELL LOCATIONS FROM FP - CY - GWPP - 01. (REF. [8])

Plant Data (ft) UTM Zone 15, (m) Depth Depth Surface Top of Bottom of Screen to to Well ID Date Unique Elevation Riser Well Interval Top Bottom Installed Number Easting Northing Easting Northing (ft) Elevation Elevation Elev - of of (ft) (ft) Elev Screen Screen (ft) (ft)

MW1 8/10/1994 547747 4847.19 10248.69 433407.38 5020424.14 930.4 930.19 902.4 902.4 912.4 18 28 MW1B 1/26/2023 870184 4857.61 10247.41 433410.44 5020425.10 930.2 929.96 873.2 973.2 878.2 52 57 PW1 2/21/2023 870167 5081.98 10055.39 433496.59 5020399.96 927.9 930.41 898.7 898.7 903.7 24 29 MW2 8/10/1994 547748 4843.43 10326.78 433396.55 5020445.36 921.8 923.82 897.5 897.5 907.5 14 24 MW3 8/10/1994 547749 4889.37 10319.18 433410.26 5020449.01 919.9 921.91 901.2 901.2 911.2 9 19 MW4 10/8/2007 747055 5281.42 10320.84 433518.94 5020498.60 925.4 927.86 898.7 898.7 908.7 17 27 MW4B 1/24/2023 870185 5289.29 10321.02 433521.10 5020499.64 925.8 928.26 877.8 877.8 882.8 43 48 MW5 9/6/2007 747056 4549.88 9757.05 433386.42 5020250.34 943.0 942.75 901.7 901.7 911.7 31 41 MW6 9/7/2007 747057 5035.29 9563.03 433545.55 5020257.29 930.7 933.24 899.9 899.9 909.9 21 31 MW7 9/5/2007 747058 6205.26 9609.17 433864.70 5020416.73 920.0 922.49 898.1 898.1 908.1 12 22 MW8 9/5/2007 747059 5393.93 8251.55 433809.51 5019938.00 931.5 934.00 900.1 900.1 910.1 21 31 MW-9 9/4/2009 725274 5074.19 10064.31 433493.53 5020401.38 927.9 927.58 901.2 901.2 911.2 17 27 MW9B 11/17/2009 772326 5075.65 10054.35 433495.19 5020398.80 927.9 927.75 883.5 883.5 888.5 39 44 PW9 2/6/2023 870166 5074.80 10059.10 433494.36 5020400.01 927.9 928.08 892.4 892.4 897.4 31 36 PW10A** 5/30/2023 725272 4885.31 10045.19 433443.47 5020372.40 934.9 936.36 895.9 895.9910.9 24 39 MW10B 12/29/2022 870161 4887.86 10037.95 433445.13 5020370.70 934.9 934.41 875.9 875.9 880.9 54 59 MW 11 9/2/2009 725273 4886.97 9931.96 433458.12 5020341.16 934.9 934.51 899.7 899.7 909.7 25 35 MW12A 10/29/2009 772328 5191.46 10105.31 433520.96 5020427.47 932.4 932.14 898.7 898.7 908.7 24 34 MW12B 11/2/2009 772329 5195.51 10106.27 433521.97 5020428.24 932.4 932.13 884.4 884.4 889.4 43 48 PW13A** 5/31/2023 772330 5059.49 10210.49 433471.13 5020440.14 931.3 932.95 891.3 891.3906.3 25 40 MW13B 11/1/2009 772331 5062.00 10212.53 433471.57 5020441.02 931.2 933.71 873.4 873.4 878.4 56 61 MW 14 9/13/2010 778176 4829.02 10402.98 433383.00 5020464.72 908.7 912.42 902.1 902.1 905.1 4 7 MW15A 6/25/2012 789990 5126.35 10352.88 433471.86 5020488.07 919.0 918.67 903.0 903.0 913.0 6 16 MW15B 6/26/2012 789991 5131.93 10352.93 433473.40 5020488.78 919.1 918.79 869.5 869.5 874.5 45 50 MW16A 12/28/2022 870162 5191.47 10214.97 433507.22 5020457.91 930.6 930.07 899.6 899.6 909.6 21 31 MW16B 12/28/2022 870163 5188.29 10223.72 433505.24 5020459.96 930.7 930.34 877.7 877.7 882.7 48 53 PW16A 2/20/2023 870218 5188.48 10213.12 433506.63 5020457.04 930.5 932.85 892.5 892.5 902.5 28 38 MW17A 12/21/2022 870164 5146.25 9802.99 433546.33 5020337.79 933.6 935.37 900.6 900.6 910.6 23 33 MW17B 12/20/2022 870165 5141.41 9803.31 433544.90 5020337.36 933.5 934.90 858.5 858.5 863.5 70 75 MW19A 1/11/2023 870186 5368.46 10141.08 433565.64 5020459.58 930.5 930.31 900.5 900.5 910.5 20 30 MW19B 1/11/2023 870187 5378.46 10141.03 433568.42 5020460.82 930.5 930.24 880.5 880.5 885.5 45 50 MW20A 1/27/2023 870188 5561.85 10201.21 433611.82 5020500.52 921.7 923.36 897.7 897.7 907.7 14 24 MW21A 1/27/2023 870189 5701.37 9721.49 433710.68 5020384.77 923.6 926.28 897.6 897.6 907.6 16 26 PW22A 1/25/2023 870190 5223.69 10132.39 433526.52 5020439.03 931.6 933.47 892.6 892.6 902.6 29 39 MW23A 3/17/2023 870250 5225.01 10332.11 433501.86 5020494.66 921.6 923.25 898.6 898.6 908.6 13 23 MW23B 3/17/2023 870251 5225.56 10338.94 433501.16 5020496.63 921.3 923.86 876.3 876.3 881.3 40 45 MW24A 6/8/2023 872351 4804.67 10025.59 433423.53 5020356.85 934.8 936.54 901.8 901.8 911.8 23 33 MW26A 6/15/2023 872374 5150.93 10419.40 433470.35 5020509.62 917.5 919.27 899.5 899.5909.5 8 18 MW26B 6/15/2023 872375 5160.96 10420.68 433472.97 5020511.23 917.4 919.56 869.4 869.4874.4 43 48 MW27A 6/15/2023 872372 5253.84 10424.64 433498.27 5020523.97 917.5 919.78 899.5 899.5909.5 8 18 MW27B 6/15/2023 872373 5262.43 10424.86 433500.63 5020525.11 917.6 919.91 871.6 871.6876.6 41 46 MW28A 7/5/2023 872321 5324.84 10423.67 433518.11 5020532.60 918.4 920.51 898.4 898.4908.4 10 20 MW28B 7/5/2023 872322 5332.78 10423.44 433520.34 5020533.53 918.8 920.64 878.8 878.8883.8 35 40 MW29A 6/30/2023 872323 5391.03 10387.72 433541.00 5020530.91 920.6 922.79 898.6 898.6908.6 13 23 MW29B 6/29/2023 872324 5398.64 10384.23 433543.55 5020530.90 920.6 922.73 877.6 877.6882.6 38 43 MW30A 7/6/2023 872325 5465.99 10360.20 433565.27 5020532.66 920.0 921.33 899.0 899.0909.0 11 21 MW30B 7/6/2023 872326 5473.21 10357.95 433567.55 5020532.94 919.9 921.78 880.9 880.9885.9 34 39 MW31A 7/6/2023 872328 5320.18 10236.12 433540.32 5020479.93 929.0 930.86 894.0 894.0909.0 20 35 MW31B 7/6/2023 872327 5328.12 10236.47 433542.48 5020481.02 928.8 930.63 878.8 878.8883.8 45 50 MW33A 7/19/2023 872414 5456.44 10424.99 433554.49 5020549.46 919.0 920.87 897.0 897.0907.0 12 22 MW33B 7/18/2023 872415 5464.23 10422.71 433556.94 5020549.80 919.1 920.39 879.1 879.1884.1 35 40 MW37A 7/21/2023 872416 5562.59 10450.69 433580.75 5020569.90 913.0 914.96 896.0 896.0906.0 7 17 MW37B 7/21/2023 872417 5571.69 10450.91 433583.26 5020571.10 913.9 916.20 875.9 875.9880.9 33 38

• • Monitoring Wells MW-10 and MW-13A have been over -drilled and converted into Pumping Wells PW-10A and PW-13A Respectively.

(/,, Xcel Energy Monticello Nuclear Generating Plant Page 36 Attachment C: Groundwater Monitoring Well Locations

TABLE 18 : MNGP MONITORING WELL LOCATIONS FROM FP - CY - GWPP - 01. (REF. [8]) (CONT.)

Plant Data (ft) UTM Zone 15, (m) Top of Bottom of Screen Depth Depth to Unique Surface Riser Well Interval to Top Well ID Date Installed Number Easting Northing Easting Northing Elevation Elevation Elevation Elev - of Bottom of (ft) Screen Screen (ft)

(ft) (ft) Elev (ft)

MW 48A 7/26/2023 872437 5711.40 10444.22 433622.90 5020586.75 919.6 921.62 897.6 897.6 907.6 12 22 MW 48B 7/26/2023 872438 5703.61 10444.65 433620.68 5020585.90 920.8 922.59 868.8 868.8 873.8 47 52 MW 50A 7/24/2023 872439 5700.59 10313.03 433636.33 5020548.96 919.4 921.70 897.4 897.4 907.4 12 22 MW 58A 7/25/2023 872440 5836.28 10432.11 433659.10 5020599.04 920.1 922.87 899.1 899.1 909.1 11 21 MW-66A 10/11/2023 880250 5732.81 9949.96 433690.78 5020452.16 919.5 920.89 891.5 891.5-901.5 18 28 MW-67A 10/12/2023 880251 5435.28 9970.07 433605.63 5020420.47 930.6 932.47 895.6 895.6-905.6 25 35 MW-67B 10/12/2023 880252 5443.78 9969.50 433608.06 5020421.37 930.6 932.83 875.6 875.6-880.6 50 55 MW-68A 10/11/2023 880253 4870.85 9585.16 433497.11 5020242.83 936.8 936.80 902.8 902.8-912.8 24 34 MW 101A 7/27/2023 872427 6222.89 7498.06 434134.17 5019832.62 928.2 929.85 901.2 901.2 911.2 17 27 MW 102A 7/28/2023 872428 6713.15 7546.16 434264.30 5019907.42 926.4 928.59 989.4 989.4 999.4 18 28 MW 103A 7/28/2023 872429 6606.53 7219.23 434275.66 5019803.26 935.2 937.55 903.3 903.3 913.3 22 32

(/,, Xcel Energy Monticello Nuclear Generating Plant Page 37 Attachment D: 2023 Groundwater Protection Program Well Data

ATTACHMENT D: 2023 GROUNDWATER PROTECTIO N PROGRA M WELL DATA

TABLE 19: 2023 GROUNDWATER MONITORING DATA FOR MNGP.

Concentration (pCi/L) 140Ba-Lab ID Collect Date 3H 54Mn 58Co 59Fe 60Co 65Zn 95Zr 95Nb 134Cs 137Cs 140La

Monitoring Well 1 (MW-1)

615805001 3/22/2023 < 255 < 1.58 < 1.73 < 3.69 < 1.88 < 3.28 < 2.99 < 1.97 < 1.69 < 2.84 < 11.5 624481001 5/24/2023 < 223 < 1.54 < 1.63 < 3.84 < 1.53 < 3.38 < 3.26 < 1.89 < 1.74 < 1.54 < 15.6 635348001 8/23/2023 < 235 < 1.79 < 1.74 < 3.52 < 1.50 < 2.70 < 3.17 < 2.07 < 1.68 < 1.52 < 17.4 643202001 10/24/2023 < 125 < 2.01 < 2.14 < 4.19 < 2.27 < 3.91 < 3.42 < 2.15 < 2.10 < 2.12 < 12.8 Monitoring Well 1B (MW-1B) 643202002 10/24/2023 < 125 < 1.81 < 1.49 < 3.79 < 1.83 < 3.03 < 3.39 < 1.78 < 1.53 < 1.88 < 9.85

Monitoring Well 2 (MW-2)

615805002 3/22/2023 < 240 < 1.21 < 1.26 < 2.74 < 1.39 < 2.66 < 2.46 < 1.49 < 1.48 < 1.40 < 8.64 624481002 5/24/2023 < 223 < 1.48 < 1.54 < 1.42 < 3.25 < 3.34 < 2.96 < 1.68 < 1.69 < 1.58 < 14.5 635348002 8/23/2023 < 246 < 1.27 < 1.46 < 3.30 < 1.18 < 2.56 < 2.61 < 1.68 < 1.45 < 1.33 < 13.9 643202003 10/24/2023 < 153 < 1.50 < 1.60 < 3.29 < 1.52 < 3.35 < 2.65 < 1.77 < 1.73 < 1.72 < 9.86

Monitoring Well 3 (MW-3)

615805003 3/22/2023 < 255 < 1.52 < 1.46 < 2.89 < 1.42 < 2.64 < 2.63 < 1.62 < 1.58 < 1.50 < 9.31 624481003 5/24/2023 < 222 < 1.44 < 1.73 < 3.92 < 1.72 < 3.26 < 3.15 < 1.74 < 1.80 < 1.67 < 16.1 635348003 8/23/2023 < 248 < 1.29 < 1.52 < 3.62 < 1.37 < 2.84 < 2.75 < 1.73 < 1.56 < 1.32 < 14.5 643202004 10/24/2023 < 132 < 1.43 < 1.56 < 3.58 < 1.75 < 3.53 < 3.09 < 1.67 < 1.89 < 2.14 < 10.8

Monitoring Well 4 (MW-4) 615805004 3/21/2023 < 248 < 1.28 < 1.45 < 3.20 < 1.50 < 3.01 < 2.83 < 1.52 3.03 +/- 2.82 < 1.45 < 9.96 624481004 5/24/2023 < 224 < 1.52 < 1.62 < 3.72 < 1.54 < 2.76 < 3.00 < 1.52 < 1.69 < 1.55 < 14.8 627525001 6/16/2023 691 +/- 222 627525002 6/17/2023 815 +/- 223 628045001 6/21/2023 878 +/- 235 631021001 7/18/2023 5980 +/- 352 636604001 8/24/2023 606 +/- 229 < 1.21 <1.64 < 3.78 < 1.53 < 2.80 < 2.88 < 1.54 <1.43 <1.30 < 26.0 639233001 9/19/2023 2310 +/- 248 643949001 10/24/2023 2030 +/- 264 < 1.51 < 1.56 < 3.47 < 1.45 < 3.31 < 3.01 < 1.73 <1.60 < 1.51 < 12.5 650022001 11/28/2023 1300 +/- 292 650357001 12/18/2023 2350 +/- 269 Monitoring Well 4B (MW-4B)

643202005 10/25/2023 < 129 < 1.28 < 1.21 < 2.53 < 1.55 < 2.46 < 2.45 < 1.18 < 1.33 < 1.26 < 6.43

Monitoring Well 5 (MW-5)

634806001 8/22/2023 < 245 < 1.38 < 1.51 < 3.24 < 1.60 < 2.77 < 2.58 < 1.61 < 1.64 < 1.50 < 11.5 fl Xcel Energy Monticello Nuclear Generating Plant Page 38 Attachment D: 2023 Groundwater Protection Program Well Data

TABLE 19: 2023 GROUNDWATER MONITORING DATA FOR MNGP. (CONTINUED).

Lab ID Collect Date 3H 54Mn 58Co 59Fe 60Co 65Zn 95Zr 95Nb 134Cs 137Cs 140Ba-140La

Monitoring Well 6 (MW-6)

634806002 8/22/2023 < 244 < 1.61 < 1.50 < 3.54 < 1.50 < 2.93 < 2.72 < 2.01 < 1.57 < 1.64 < 13.0

Monitoring Well 7 (MW-7)

634806003 8/22/2023 < 252 < 1.93 < 2.05 < 4.14 < 1.92 < 4.01 < 3.54 < 2.17 < 2.12 < 1.83 < 14.9

Monitoring Well 8 (MW-8)

634806004 8/22/2023 < 244 < 1.15 < 1.36 < 3.03 < 1.19 < 2.53 < 2.41 < 1.55 < 1.41 < 1.31 < 10.2

Monitoring Well 9 (MW-9) 608231006 1/17/2023 2680000 +/- 7550 < 1.62 < 1.61 < 3.18 < 1.93 < 3.21 < 2.6 < 1.64 < 1.84 < 1.78 < 8.12 608231006 1/17/2023 2700000 +/- 7610

• 613684001 2/27/2023 1500000 +/- 29300 616606001 3/21/2023 1800000 +/- 35100 < 1.33 < 1.43 < 4.3 < 1.43 < 2.76 < 3.13 < 1.88 < 1.44 < 1.29 < 29.7 619903001 4/20/2023 1120000 +/- 6710 624656001 5/24/2023 776000 +/- 6410 < 1.1 < 1.28 < 2.83 < 1.1 < 2.3 < 2.37 < 1.34 < 1.18 < 1.11 < 14.1 628045002 6/21/2023 253000 +/- 3200

631021002 7/18/2023 214000 +/- 1990 636604002 8/22/2023 266000 +/- 3770 < 1.98 < 1.98 < 4.16 < 1.57 < 3.03 < 3.53 < 1.98 < 1.56 < 1.51 < 32.4 639233002 9/19/2023 174000 +/- 1890 643949002 10/18/2023 248000 +/- 2400 < 1.37 < 1.80 < 4.21 < 1.62 < 3.07 < 3.01 < 1.89 < 1.56 < 1.67 < 20.4 650022002 11/27/2023 364000 +/- 4550

650357002 12/18/2023 208000 +/- 2010 Monitoring Well 9B (MW-9B) 608231002 1/17/2023 2970000 +/- 7980 < 1.53 < 1.69 < 2.83 < 1.8 < 3.05 < 2.97 < 1.77 < 1.77 < 1.78 < 8.61 613684002 2/27/2023 1480000 +/- 29000 616606002 3/21/2023 146000 +/- 2880 < 1.20 < 1.69 < 3.81 < 1.28 < 2.95 < 3.03 < 1.77 < 1.4 < 1.84 < 28.3 619903002 4/20/2023 26100 +/- 999 624656002 5/24/2023 9250 +/- 717 < 1.38 < 1.57 < 3.73 < 1.45 < 3.41 < 2.68 < 1.59 < 1.55 < 1.4 < 13.3 628045003 6/21/2023 19900 +/- 942 631021003 7/18/2023 23300 +/- 658 636604003 8/22/2023 20700 +/- 1090 < 1.46 < 1.77 < 4.32 < 1.37 < 2.99 < 3.28 < 2.02 < 1.49 < 1.46 < 33.5 639233003 9/19/2023 19000 +/- 636 643949003 10/18/2023 6250 +/- 407 < 1.27 < 1.5 < 3.13 < 1.26 < 2.54 < 2.43 < 1.57 < 1.35 < 1.27 < 15.9 650022003 11/27/2023 8550 +/- 704 650357003 12/18/2023 71300 +/- 1190

• Duplicate sample; not used in calculating average.

fl Xcel Energy Monticello Nuclear Generating Plant Page 39 Attachment D: 2023 Groundwater Protection Program Well Data

TABLE 19: 2023 GROUNDWATER MONITORING DATA FOR MNGP. (CONTINUED)

Lab ID Collect Date 3H 54Mn 58Co 59Fe 60Co 65Zn 95Zr 95Nb 134Cs 137Cs 140Ba -140La Monitoring Well 10 (MW-10) / Pumping Well 10A (PW-10A) 607960003 1/17/2023 < 212 613105001 2/27/2023 < 257 < 1.54 < 1.33 < 3.36 < 1.46 < 2.83 < 2.63 < 1.64 < 1.59 < 1.56 < 9.43 615805005 3/22/2023 < 258 619903006 4/20/2023 47000 +/- 1320 624656003 5/26/2023 604000 +/- 5700 < 1.81 < 1.66 < 4.10 < 1.95 < 3.38 < 3.59 < 2.14 < 1.77 < 1.97 < 14.0 628045004 6/21/2023 475000 +/- 4490 631021004 7/18/2023 169000 +/- 1760 636604004 8/24/2023 93300 +/- 2280 < 1.42 < 1.65 < 3.58 < 1.05 < 2.36 < 3.04 < 1.82 < 1.46 < 1.43 < 26.7 639233004 9/19/2023 4410 +/- 940 643949004 10/20/2023 48200 +/- 1040 < 1.04 < 1.19 < 3.01 < 1.10 < 2.14 < 2.28 < 1.30 < 1.15 < 1.11 < 13.9 650022004 11/28/2023 5980 +/- 580 650357004 12/18/2023 4550 +/- 337 Monitoring Well 10B (MW-10B) 615805006 3/22/2023 < 250 < 2.24 < 2.06 < 4.52 < 2.42 < 5.66 < 4.97 < 2.44 < 2.58 < 2.26 < 14.0 624481005 5/26/2023 < 223 < 1.37 < 1.30 < 3.08 < 1.27 < 2.62 < 2.38 < 1.41 < 1.50 < 1.39 < 11.6 643202006 10/24/2023 < 125 < 1.78 < 1.86 < 3.06 < 2.05 < 3.74 < 3.55 < 1.76 < 1.99 < 1.83 < 11.1 Monitoring Well 11 (MW-11) 615805007 3/22/2023 < 254 < 1.86 < 2.00 < 4.16 < 2.02 < 3.78 < 3.62 < 2.26 < 2.09 < 2.16 < 11.6 624481006 5/26/2023 < 223 < 1.42 < 1.53 < 3.63 < 1.45 < 2.93 < 2.73 < 1.65 < 1.53 < 1.46 < 13.4 635348004 8/23/2023 < 247 < 1.53 < 1.69 < 3.69 < 1.68 < 3.53 < 2.97 < 1.78 < 1.61 < 1.40 < 16.2 643200006 10/24/2023 < 135 < 1.92 < 2.03 < 3.81 < 2.04 < 3.98 < 3.93 < 2.36 < 2.10 < 2.42 < 12.2 Monitoring Well 12A (MW-12A) 608231003 1/17/2023 845000 +/- 4240 < 1.72 < 1.73 < 3.41 < 1.54 < 3.31 < 2.94 < 1.78 < 1.93 < 1.69 < 9.34 613684003 2/27/2023 19600 +/- 520 616606003 3/21/2023 307000 +/- 6030 < 1.14 < 1.34 < 3.60 < 1.24 < 2.49 < 1.57 < 2.67 < 1.18 < 1.20 16.6 +/- 14.8 619903003 4/20/2023 184000 +/- 2590 624656004 5/26/2023 61400 +/- 1840 < 1.30 < 1.46 < 3.42 < 1.61 < 2.74 < 2.83 < 1.70 < 1.45 < 1.56 < 10.7 628045005 6/21/2023 9140 +/- 634 631021005 7/18/2023 2370 +/- 244 636604005 8/23/2023 397 +/- 196 < 1.12 < 1.42 < 3.26 < 1.21 < 2.39 < 2.57 < 1.51 < 1.16 < 1.25 < 24.1 639233005 9/19/2023 310 +/- 145 643949005 10/20/2023 296 +/- 170 < 1.41 < 1.56 < 4.07 < 1.71 < 3.23 < 3.15 < 1.70 < 1.70 < 1.53 < 19.6 650022005 11/27/2023 766 +/- 230 650357005 12/18/2023 892 +/- 209 Monitoring Well 12B (MW-12B) 615805008 3/21/2023 < 250 < 1.37 < 1.62 < 2.71 < 1.24 < 2.20 < 2.40 < 1.44 < 1.54 < 1.45 < 9.82 624481007 5/26/2023 < 222 < 1.40 < 1.57 < 2.86 < 1.43 < 2.53 < 2.43 < 1.55 < 1.53 < 1.47 < 11.9 636604006 8/23/2023 19300 +/- 1050 < 1.30 < 1.77 < 4.38 < 1.63 < 2.94 < 3.12 < 1.83 < 1.48 < 1.42 < 30.4 643949006 10/20/2023 87200 +/- 1410 < 1.15 < 1.29 < 2.83 < 1.24 < 2.53 < 2.34 < 1.36 < 1.15 < 1.17 < 15.5 650022006 11/27/2023 36100 +/- 1440 650357006 12/18/2023 29500 +/- 782 fl Xcel Energy Monticello Nuclear Generating Plant Page 40 Attachment D: 2023 Groundwater Protection Program Well Data

TABLE 19: 2023 GROUNDWATER MONITORING DATA FOR MNGP. (CONTINUED).

Lab ID Collect Date 3 H 54Mn 58Co 59Fe 60Co 65Zn 95Zr 95Nb 134Cs 137Cs 140Ba -140La

Monitoring Well 13A (MW-13A) / Pumping Well 13A (PW-13A) 607960001 1/17/2023 < 217 613105002 2/27/2023 333 +/- 156 616606005 3/21/2023 2340 +/- 240 < 1.27 < 1.53 < 4.08 < 1.22 < 2.69 < 2.95 < 1.82 < 1.36 < 1.21 < 28.9 619903004 4/20/2023 489000 +/- 4370 624656005 5/26/2023 485000 +/- 5100 < 1.63 < 1.88 < 1.69 < 4.14 < 3.38 < 2.92 < 1.93 < 1.72 < 1.69 < 14.1 628045006 6/21/2023 1110000 +/- 6770 631021006 7/18/2023 588000 +/- 3280 636604007 8/24/2023 219000 +/- 3520 < 1.55 < 2.26 < 5.17 < 1.53 < 3.40 < 4.23 < 2.33 < 1.86 < 1.68 < 31.0 639233006 9/19/2023 96000 +/- 1380 643949007 10/20/2023 103000 +/- 1550 < 1.26 < 1.48 < 3.35 < 1.30 < 2.68 < 2.57 < 1.70 < 1.39 < 1.30 < 16.1 Monitoring Well 13B (MW-13B) 607960002 1/17/2023 < 216 613105003 2/27/2023 < 259 615805009 3/21/2023 < 255 < 1.58 < 1.71 < 3.87 < 1.64 < 3.51 < 2.99 < 1.81 < 1.66 < 1.90 < 10.8 619479001 4/20/2023 < 179 624481008 5/26/2023 < 223 < 1.24 < 1.24 < 2.91 < 1.31 < 2.70 < 2.50 < 1.37 < 1.42 < 1.24 < 11.6 636604008 8/24/2023 < 217 < 1.62 < 1.93 < 5.05 < 1.57 < 3.24 < 3.39 < 1.87 < 1.59 < 1.57 < 15.5 643949008 10/24/2023 < 251 < 1.36 < 1.59 < 3.35 < 1.5 < 2.91 < 3.02 < 1.66 < 1.59 < 1.53 < 14.2 Monitoring Well 14 (MW-14) 624481009 5/24/2023 < 222 < 1.56 < 1.71 < 3.77 < 1.47 < 3.07 < 2.72 < 1.96 < 1.63 < 1.53 < 14.3 634806005 8/21/2023 < 237 < 1.52 < 1.70 < 3.90 < 1.61 < 3.28 < 3.10 < 1.92 < 1.64 < 1.69 < 17.3 643200001 10/18/2023 < 121 < 2.20 < 1.92 < 5.20 < 2.33 < 4.96 < 3.86 < 2.45 < 2.00 < 2.47 < 16.8 Monitoring Well 15A (MW-15A) 615805010 3/21/2023 < 244 < 1.33 < 1.30 < 2.84 < 1.33 < 2.66 < 2.32 < 1.37 < 1.31 < 1.20 < 7.92 624481010 5/24/2023 < 223 < 1.38 < 1.61 < 3.61 < 1.62 < 2.91 < 2.90 < 1.63 < 1.47 < 1.42 < 13.0 627349001 6/16/2023 < 298 635348005 8/23/2023 844 +/- 192 < 1.85 < 2.16 < 4.69 < 2.14 < 4.12 < 3.66 < 2.02 < 1.90 < 1.87 < 18.4 639233007 9/19/2023 9670 +/- 462 643949009 10/24/2023 58500 +/- 1180 < 1.58 < 1.58 < 4.03 < 1.62 < 3.37 < 3.38 < 1.68 < 1.65 < 1.54 < 16.4 650022007 11/27/2023 27400 +/- 1250 650357007 12/18/2023 33400 +/- 813 Monitoring Well 15B (MW-15B) 615805011 3/21/2023 < 253 < 1.81 < 1.76 < 4.16 < 2.14 < 4.26 < 3.39 < 2.31 < 2.09 < 2.17 < 14 624481011 5/24/2023 < 222 < 1.43 < 1.66 < 3.76 < 1.59 < 3.22 < 2.88 < 1.92 < 1.59 < 1.64 < 15.4 635348006 8/23/2023 < 251 < 1.47 < 1.49 < 3.25 < 1.45 < 2.54 < 2.52 < 1.57 < 1.48 < 1.34 < 12.9 643200002 10/25/2023 < 127 < 1.63 < 1.60 < 2.72 < 1.67 < 3.37 < 2.72 < 1.60 < 1.72 < 1.65 < 7.55

fl Xcel Energy Monticello Nuclear Generating Plant Page 41 Attachment D: 2023 Groundwater Protection Program Well Data

TABLE 19: 2023 GROUNDWATER MONITORING DATA FOR MNGP. (CONTINUED).

Lab ID Collect Date 3H 54Mn 58Co 59Fe 60Co 65Zn 95Zr 95Nb 134Cs 137Cs 140Ba-140La

Monitoring Well 16A (MW-16A) 608231004 1/17/2023 12700 +/- 548 < 1.76 < 1.67 < 4.10 < 1.97 < 3.34 < 3.33 < 1.93 < 1.82 < 1.94 < 10.6 613684004 2/27/2023 11100 +/- 398 616606004 3/22/2023 86100 +/- 1710 < 1.07 < 1.22 < 3.15 < 1.15 < 2.48 < 2.37 < 1.48 < 1.20 < 1.14 < 23.9 619903005 4/20/2023 135000 +/- 2290 624656006 5/26/2023 1640 +/- 318 < 1.73 < 1.76 < 3.21 < 1.52 < 3.02 < 3.21 < 1.87 < 1.76 < 1.66 < 14.5 628045007 6/21/2023 143000 +/- 2450 631021007 7/18/2023 23700 +/- 666 636604009 8/23/2023 24300 +/- 1190 < 1.26 < 1.54 < 3.78 < 1.25 < 2.74 < 2.74 < 1.59 < 1.33 < 1.24 < 28.0 639233008 9/19/2023 18400 +/- 623 643949010 10/24/2023 7870 +/- 451 650022008 11/27/2023 147000 +/- 2870 < 1.39 < 1.51 < 2.99 < 1.24 < 2.49 < 2.84 < 1.62 < 1.41 < 1.45 < 13.9 650357008 12/18/2023 65700 +/- 1130 Monitoring Well 16B (MW-16B) 615805012 3/22/2023 < 256 < 1.41 < 1.41 < 3.14 < 1.51 < 2.89 < 2.84 < 1.61 < 1.57 < 1.39 < 9.91 636604010 8/23/2023 11500 +/- 812 < 1.51 < 1.67 < 4.40 < 1.42 < 3.31 < 3.25 < 1.93 < 1.59 < 1.54 < 32.2 643949011 10/24/2023 6820 +/- 424 < 1.35 < 1.57 < 3.37 < 1.56 < 2.94 < 3.22 < 1.98 < 1.61 < 1.46 < 15.8 Monitoring Well 23A (MW-23A) 636604011 8/28/2023 29600 +/- 1260 < 1.19 < 1.43 < 2.97 < 1.12 < 2.44 < 2.80 < 1.50 < 1.28 < 1.54 < 20.9 643949012 10/24/2023 17300 +/- 664 < 1.47 < 1.57 < 3.80 < 1.40 < 3.12 < 3.17 1.63 < 1.71 < 1.41 < 17.7 Monitoring Well 26A (MW-26A) 627349002 6/16/2023 < 297 Monitoring Well 26B (MW-26B) 627349003 6/16/2023 < 291 Monitoring Well 27A (MW-27A) 627349004 6/16/2023 < 284 Monitoring Well 27B (MW-27B) 627349005 6/16/2023 < 297 Monitoring Well 29A (MW-29A) 629562001 7/12/2023 1660 +/- 193 636604012 8/23/2023 60900 +/- 1830 < 1.30 < 1.72 < 3.89 < 1.39 < 2.74 < 2.88 < 1.79 < 1.41 < 1.28 < 30.0 643949013 10/20/2023 613 +/- 192 < 1.15 < 1.26 < 2.80 < 1.23 < 2.56 < 2.55 < 1.36 < 1.26 < 1.29 < 16.1 650023001 11/28/2023 1270 +/- 269 650357009 12/18/2023 269 +/- 170 Monitoring Well 30A (MW-30A) 629562002 7/12/2023 45900 +/- 987 636604013 8/23/2023 363 +/- 163 < 1.45 < 1.67 < 4.53 < 1.53 < 3.14 < 3.19 < 1.74 < 1.49 < 1.36 16.6 +/- 18.7 643949014 10/20/2023 2460 +/- 276 < 1.07 < 1.32 < 2.98 < 1.18 < 2.38 < 2.22 < 1.29 < 1.19 < 1.06 < 14.4 650023002 11/28/2023 581 +/- 203 650357010 12/18/2023 719 +/- 196 Monitoring Well 31B (MW-31B) 636604014 8/23/2023 2040 +/- 345 < 1.42 < 1.86 < 4.42 < 1.38 < 3.4 < 3.38 < 1.86 < 1.57 < 1.51 < 33.2 fl Xcel Energy Monticello Nuclear Generating Plant Page 42 Attachment D: 2023 Groundwater Protection Program Well Data

TABLE 19: 2023 GROUNDWATER MONITORING DATA FOR MNGP. (CONTINUED).

Lab ID Collect Date 3H 54Mn 58Co 59Fe 60Co 65Zn 95Zr 95Nb 134Cs 137Cs 140Ba-140La

Monitoring Well 33A (MW-33A) 636604015 8/23/2023 716 +/- 209 < 1.57 < 1.87 < 4.49 < 1.53 < 3.08 < 3.58 < 2.12 < 1.56 < 1.53 < 34.2 643949015 10/23/2023 2540 +/- 281 < 1.24 < 1.26 < 2.93 < 1.18 < 2.57 < 2.33 < 1.44 < 1.27 < 1.22 < 12.3 650023003 11/28/2023 5260 +/- 536 650357011 12/18/2023 3730 +/- 310

Monitoring Well 37A (MW-37A) 636604016 8/28/2023 8890 +/- 677 < 1.24 < 1.20 < 3.11 < 1.20 < 2.50 < 2.59 < 1.49 < 1.18 < 1.12 15.8 +/- 12.1 643949016 10/23/2023 < 250 < 1.45 < 1.59 < 3.44 < 1.46 < 3.53 < 3.19 < 1.83 < 1.47 < 1.50 17.1

Monitoring Well 48A (MW-48A) 635816001 8/23/2023 < 202 < 1.24 < 1.47 < 3.28 < 1.46 < 2.95 < 2.71 < 1.47 < 1.54 < 1.53 < 15.3

Monitoring Well 101 (MW-101) 643200003 10/25/2023 <135 < 3.07 < 3.08 < 5.59 < 2.83 < 6.22 < 5.45 < 3.31 < 2.90 < 3.01 < 15.0

Monitoring Well 102 (MW-102) 643200004 10/25/2023 < 130 < 1.53 < 1.51 < 3.92 < 1.48 < 2.97 < 2.82 < 1.80 < 1.76 < 1.81 < 10.0

Monitoring Well 103 (MW-103) 643200005 10/25/2023 < 131 < 2.14 < 1.97 < 4.61 < 2.15 < 4.32 < 3.81 < 2.39 < 2.34 < 2.08 < 13.5

Storm Drain SD006 611414001 2/8/2023 < 254 < 1.39 < 1.60 < 3.11 < 1.22 < 2.63 < 2.78 < 1.65 < 1.42 < 1.44 < 13.1 611414002 2/8/2023 < 251* < 1.23 < 1.40 < 2.93 < 1.10 < 2.60 < 2.50 < 1.50 < 1.30 < 1.21 < 11.8 619349001 4/10/2023 < 178 < 1.46 < 1.53 < 2.75 < 1.37 < 2.76 < 2.76 < 1.59 < 1.63 < 1.53 < 10.6 634097001 8/14/2023 < 235 < 1.48 < 1.70 < 3.60 < 1.81 < 3.52 < 3.04 < 1.75 < 1.90 < 1.71 < 10.7 643207001 10/25/2023 < 211 < 1.54 < 1.61 < 3.37 < 2.03 < 3.71 < 3.17 < 1.83 < 2.05 < 1.67 < 8.78

• Duplicate sample; not used in calculating average.

fl Xcel Energy