ML25111A131

From kanterella
Jump to navigation Jump to search
2024 Radioactive Effluent Release Report
ML25111A131
Person / Time
Site: South Texas, 07201041  STP Nuclear Operating Company icon.png
Issue date: 04/21/2025
From: Grones S
South Texas
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
NOC-AE-25004102
Download: ML25111A131 (1)
v • d • e


Text

Nucleor UJ April 21,2025 NOC-AE-25004102 10 CFR 50.36a STI:35729722 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 South Texas Project Units 1 and 2 Docket Nos. STN 50-498; STN 50-499; and72-1041 2024 Radioactive Effluent Release Report Pursuant to the South Texas Project Technical Specification 6.9.1.4 and 10 CFR 50.36a, STP Nuclear Operating Company provides the attached 2024 Radioactive Effluent Release Report. The report covers the period from January 1,2024, to December 31,2024.

There are no commitments in this letter.

lf there are any questions on this report, please contact me at (361) 972-7596, or Stephanie Rodgers at (361) 972-4527 es Manager, Chemistry & Safety

Enclosure:

2024 Radioactive Effluent Release Report Regional Administrator, Region lV U.S. Nuclear Regulatory Commission 1600 E. Lamar Boulevard Arlington, TX 7601 1-4511 cc

SOUTH TEXAS PROJECT ELECTRIC GENERATING STATION 2024 RADIOACTIVE EFFLUENT 2024 RADIOACTIVE EFFLUENT RELEASE REPORT RELEASE REPORT STI #35658027 O P G P 0 3 -Z X- 0 0 07 Photo courtesy of L.Boone

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Blank Page Intentionally Left Blank

2024 Radioactive Effluent Release Report SOUTH TEXAS PROJECT ELECTRIC GENERATING STATION Completed by Generation in accordance with Technical Specifications for United States Nuclear Regulatory Commission Renewed Facility Operating License Nos.

NPF-76 & NPF-80 April 2025 Authored by:

Shaterika N. Brown Consulting Chemist Chemistry Division Technical Review:

James R. Flournoy Consulting Chemist Chemistry Division Approved by:

Scott Grones Manager Chemistry Division 0PGP03ZX0007, Preparation of the Radioactive Effluent Release Report South Texas Identification (STI): 35658027 Docusign Envelope ID: C722E23A-0611-43EE-AE8C-6304DEA70086

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Blank Page Intentionally Left Blank

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Table of Contents i

Table of Contents PAGE Summary Tab Report Summary and Introduction........................................................................................................ 1-1 Effluent Program Tab Supplemental Information for Effluent and Waste Disposal............................................................... 2-1 Regulatory Limits Effluent Concentrations Limits Average Energy (Million Electron Volts/Disintegration)

Measurement and Approximations of Total Activity Batch Releases Abnormal (Unplanned) Releases Estimate of Total Error Solid Waste Shipments Radiological Impact on Man Meteorological Data Lower Limit of Detection Dose to Members of the Public Technical Specifications and Offsite Dose Calculation Manual Controls Reporting Requirements............................................................................................................................................ 3-1 Offsite Dose Calculation Manual Changes Annual Land Use Census Radioactive Waste Treatment System Design Modification Description Inoperable Effluent Monitoring Instrumentation Explanation Gas Storage Tank Curie Limit Violation Description Unprotected Outdoor Tank Curie Limit Violation Description Abnormal (Unplanned) Release Description Radioactive Waste Process Control Program Changes Independent Spent Fuel Storage Installation (ISFSI)

Radiological Data Tab Gaseous Effluents..................................................................................................................................... 4-1 Liquid Effluents....................................................................................................................................... 5-1 Solid Waste and Irradiated Fuel Shipments.......................................................................................... 6-1

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Table of Contents ii Table of Contents PAGE Dose Data Tab Dose Accumulations................................................................................................................................. 7-1 Results of the Direct Radiation Measurements Program..................................................................... 8-1 Meteorological Data Tab Joint Frequency Tables........................................................................................................................... 9-1 Joint Frequency Tables for First Quarter Joint Frequency Tables for Second Quarter Joint Frequency Tables for Third Quarter Joint Frequency Tables for Fourth Quarter Joint Frequency Tables for First Quarter Batch Release Joint Frequency Tables for Second Quarter Batch Release Joint Frequency Tables for Third Quarter Batch Release Joint Frequency Tables for Fourth Quarter Batch Release

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Summary Tab Summary Tab

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Summary Tab Intentionally Left Blank

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Summary and Introduction 1-1 Report Summary During 2024, as in previous years, operation of the South Texas Project (STP) created no adverse effects or health risks. The maximum radiation exposure calculated for a hypothetical person living at the boundary of STP during 2024 due to operation of STP was less than one millirem. For reference, this dose may be compared to the average annual radiation exposure of 620 millirem to people in the United States from all sources, as shown in Figure 1-1. Of that 620 millirem, natural radiation sources in the environment accounted for 50% of the radiation exposure, whilst 48% of the exposure occurred from medical procedures. Nuclear power operations contributed less than one millirem.

Figure 1-1

  • NCRP (2006). National Council on Radiation Protection and Measurements, Ionizing Radiation Exposure of the Population of the United States, (Bethesda, Maryland), NCRP Report No. 160.

During 2024, the estimated total body dose to a hypothetical Member of the Public with the highest probability for exposure from radioactive effluents and direct radiation was 0.025 millirem. This total represents approximately 0.1% of the limits of 40 CFR 190. Based on our 2024 Land Use Census, real individuals reside in the West by Southwest Sector, approximately 4,000 meters (2.5 miles) from the site. For dose calculation purposes, the residents at this location are characterized as the theoretically highest exposed individual regarding food consumption, occupancy, and other uses of the areas in the plant vicinity. Our

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Summary and Introduction 1-2 dose model assumes that this theoretically highest exposed individual may consume the maximum amount of food with all the food being grown or grazed at the residence. This hypothetical individual receives shoreline exposure from Little Robbins Slough for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> per year and consumes 21 kilograms (46 pounds) of fish taken from Little Robbins Slough.

This hypothetical individual receives a submersion dose from noble gases and dose from inhaled radioactive particulates, radioiodines, carbon-14, and tritium. This hypothetical is considered an adult and consumes 64 kilograms (140 pounds) of leafy vegetables grown at the residence and consumes 110 kilograms (240 pounds) of meat from livestock grazed at the residence. This estimated total body dose is calculated using models and exposure pathways described in our Offsite Dose Calculation Manual for a hypothetical individual offsite. Other dose estimates for Members of the Public onsite are listed in the report using exposure pathways not addressed by standard dose calculation methods.

Doses from releases to the environment at STP have historically been and continue to be well below regulatory limits, as shown in Figure 1-2. Carbon-14 accounted for a majority of the Total Body Dose reported in gaseous effluents. Members of the Public continue to receive negligible additional radiation due to the operation of STP. This Radioactive Effluent Release Report summarizes the data describing the radioactive liquid and gaseous releases from STP during 2024. The radioactive effluents from STP are effectively monitored and controlled in accordance with regulatory requirements.

Liquid and gaseous discharges from STP are continuously monitored for radioactive content.

Samples are also collected from ventilation systems and liquid discharges and analyzed for radioactivity. The sample and analysis methods are verified and augmented using an environmental laboratory. Radioactivity monitors continuously sample the ventilation

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Summary and Introduction 1-3 exhaust systems. On the liquid discharge lines, radioactivity monitors automatically divert or isolate liquid effluents if the radioactivity is higher than expected. These monitors are also equipped with remote alarm indications in the unit control rooms and health physics offices.

Prior to and during power operation, STP is required to evaluate radioactive material in the environment. We are committed to sampling and analyzing environmental samples for radioactivity to support our Radiological Environmental Monitoring Program (REMP). The results of these environmental samples are listed in our 2024 Annual Environmental Operating Report. These environmental measurements affirm the accuracy of our sampling and analysis program, a subset of our Radioactive Effluent Control Program. These measurements are categorized into four pathways. The sampled pathways include airborne, waterborne, ingestion, and direct radiation. Based on these environmental measurements and the radioactivity released to the environment (included in this report), STP continues to operate with no negative effect on the population or the environment.

The radiation monitors and the sampling and analysis program, provide an accurate determination of the type and quantity of radioactive materials released in plant effluents.

Liquid effluents are directed to the Main Cooling Reservoir (MCR) that is located entirely within the site boundary. STP continues to aggressively pursue the reduction of radioactive material in liquid effluents consistent with prudent industry practices.

Each year, the effluent monitoring results are summarized in this report and a hypothetical radiation dose to the population in the surrounding area is calculated based on gaseous radioactive effluents, meteorological conditions, and liquid radioactive effluents. The hypothetical dose assumes credible paths for radioactive material to reach a Member of the Public, such as consumption of leafy vegetables from a garden, fish from the river, inhalation, and direct exposure. The highest potential hypothetical dose to an individual at the site boundary was calculated to be less than one millirem or approximately an additional day of radiation exposure from natural radiation sources. The information presented in this report demonstrates that plant operation is consistently controlled to make certain that radioactive effluents remain below regulatory limits and to ensure protection of the public and the environment.

INTRODUCTION This Radioactive Effluent Release Report is submitted for the period of January 1, 2024 through December 31, 2024, in accordance with Appendix A of Renewed Facility Operating License Nos. NPF-76 and NPF-80, Technical Specifications, and the Offsite Dose Calculation Manual.

A single submittal is made for both units combining those sections that are common. Separate tables of releases and release totals are included where separate processing systems exist.

This report includes an annual summary of hourly meteorological measurements taken during each quarter. This data appears as tables of wind direction and wind speed by atmospheric stability class. All assessments of radiation doses are performed in accordance with the Offsite Dose Calculation Manual.

Minimal quantities of radioactivity were released during 2024. Liquid effluents are discharged to the onsite Main Cooling Reservoir and may be subsequently released offsite.

The radioactivity released in liquids beyond the site boundary was estimated using the Offsite

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Summary and Introduction 1-4 Dose Calculation Manual. Solid radioactive waste is shipped offsite for disposal. Table 1-1 lists a summary of the radioactive effluents and solid waste attributable to the station.

Table 1-1 TYPE OF RADIOACTIVE MATERIAL EFFLUENT TYPE DESTINATION VOLUME CUBIC METER CURIES NOBLE GAS GAS OFFSITE 5.4E+09 (2) 1.1E+03 PARTICULATE AND IODINES GAS OFFSITE 5.4E+09 (2) 5.5E-03 TRITIUM &

CARBON-14 GAS OFFSITE 5.4E+09 (2) 1.2E+02 TRITIUM LIQUID OFFSITE 4.8E+06 (3) 3.0E+02 (5)

FISSION AND ACTIVATION PRODUCTS LIQUID OFFSITE 4.8E+06 (3) 5.5E-04 (5)

TRITIUM LIQUID ON-SITE 4.7E+04 (4) 2.3E+03 FISSION AND ACTIVATION PRODUCTS(1)

LIQUID ON-SITE 4.7E+04 (4) 2.4E-02 SPENT RESINS AND FILTERS SOLID FOR DISPOSAL 2.8E+01 2.3E+02 DRY COMPRESSIBLE WASTE SOLID FOR DISPOSAL 5.7E+02 2.7E-01 OTHER (Large Components and Associated Commodities)

SOLID FOR DISPOSAL 7.7E+00 1.2E-03 Low Level Exempt Quantities of sewage sludge and resin SOLID FOR DISPOSAL 6.1E+01 4.9E-05 (1)Excludes dissolved and entrained gases.

(2)Unit Vent Release Volume for Units 1 and 2.

(3)Estimated MCR seepage to identified receptors.

(4)Total volume of liquid radioactive effluents discharged to the MCR.

(5)Reference ODCM, Table B4-1 for Matagorda Bay.

Tritium was the largest contributor to the offsite doses from radioactive liquid effluents.

The offsite doses are well below any regulatory limit and significantly less than the average annual radiation exposure to people in the United States from all sources (620 millirem),

from NCRP (2006). National Council on Radiation Protection and Measurements, Ionizing Radiation Exposure of the Population of the United States, (Bethesda, Maryland), NCRP Report No. 160.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Effluent Program Tab Effluent Program Tab

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Effluent Program Tab Intentionally Left Blank

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-1 Supplemental Information for Effluent and Waste Disposal

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-2 Supplemental Information for Effluent and Waste Disposal The South Texas Project is located on 12,220 acres in Matagorda County, Texas, approximately 15 miles southwest of Bay City along the west bank of the Colorado River. The South Texas Project is currently owned by Constellation Energy, City of Austin, and City Public Service Board of San Antonio as tenants in common. Houston Lighting & Power Company was the original project manager of the South Texas Project and was responsible for the engineering, design, licensing, construction, startup, and initial commercial operation of the two-unit facility. In 1997, the STP Nuclear Operating Company assumed operational control of the South Texas Project and responsibility for implementation of associated environmental programs.

The South Texas Project has two Westinghouse pressurized water reactors. The rated core thermal power of each unit is 3,853 megawatts-thermal (MWt). Each unit was originally designed for a net electrical power output of 1,250 megawatts-electric (MWe). Unit 1 received a low-power testing license on August 21, 1987, achieved initial criticality on March 8, 1988, and was declared commercially operational on August 25, 1988. Unit 2 received a low-power testing license on December 16, 1988, achieved initial criticality on March 12, 1989, and was declared commercially operational on June 19, 1989. On September 28, 2017, the United States Nuclear Regulatory Commission approved the South Texas Projects request to extend the operating licenses an additional twenty years through 2047 and 2048.

The combined units currently produce enough electricity to serve more than two million homes and businesses throughout Texas. With approximately 1,000 baseline employees, the STP Nuclear Operating Company is the largest employer and source of revenue for Matagorda County. Nuclear energy continues to provide long-term cost stability and promote energy independence. It is our nation's largest source of carbon-free energy. As we work collectively to secure our state's long-term energy future, nuclear energy will continue to play an important role as a safe and reliable supply of clean baseload electricity.

Regulatory Limits Fission and Activation Gases The air dose due to noble gases released in gaseous effluents, from each unit to areas at and beyond the Site Boundary shall be limited to the following:

During any calendar quarter: Less than or equal to 5 millirads for gamma radiation and less than or equal to 10 millirads for beta radiation, and During any calendar year: Less than or equal to 10 millirads for gamma radiation and less than or equal to 20 millirads for beta radiation.

Iodines and Particulates, Half-Lives > 8 days The dose to a Member of the Public from iodine-131, iodine-133, tritium, and all radionuclides in particulate form with half-lives greater than eight days in gaseous effluents released, from each unit to areas at and beyond the Site Boundary shall be limited to the following:

During any calendar quarter: Less than or equal to 7.5 millirems to any organ; and During any calendar year: Less than or equal to 15 millirems to any organ.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-3 Liquid Effluents The dose or dose commitment to a Member of the Public from radioactive materials in liquid effluents released, from each unit to Unrestricted Areas shall be limited to:

During any calendar quarter: Less than or equal to 1.5 millirems to the whole body and to less than or equal to 5 millirems to any organ; and During any calendar year: Less than or equal to 3 millirems to the whole body and to less than or equal to 10 millirems to any organ.

Effluent Concentrations Limits Gaseous Effluents The dose rate due to radioactive materials released in gaseous effluents from the site to areas at and beyond the Site Boundary shall be limited to the following:

For noble gases: Less than or equal to 500 millirems/year to the whole body and less than or equal to 3000 millirems/year to the skin, and For Iodine-131, Iodine-133, tritium, and all radionuclides in particulate form with half-lives greater than eight days: Less than or equal to 1500 millirems/year to any organ.

Liquid Effluents The concentration of radioactive material released in liquid effluents to Unrestricted Areas shall be limited to 10 times the concentrations specified in 10CFR, Part 20, Appendix B, Table II, Column 2, for radionuclides other than dissolved or entrained noble gases. For dissolved or entrained noble gases, the concentration shall be limited to 2.0E-04 microcurie/milliliter total activity.

Average Energy (Million Electron Volts/Disintegration)

The average energy of the radionuclide mixture in releases of fission and activation gases is not applicable to STP.

Measurement and Approximations of Total Activity The following discussions detail the methods used to measure and approximate total activity for the following:

Gaseous Effluents: Fission and Activation Gases, Tritium, Iodines, and Particulates Liquid Effluents: Fission and Activation Products, Tritium, Dissolved and Entrained Gases Tables A3-1 and A4-1 of the Offsite Dose Calculation Manual give sampling frequencies and lower limit of detection requirements for the analysis of liquid and gaseous effluent streams.

Gaseous Effluents

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-4 Analytical Methods for Gaseous Releases from the Reactor Containment Building Monthly pre-release grab samples are collected from the plant Reactor Containment Building atmosphere. These samples are analyzed on a Gamma Spectroscopy System utilizing high purity germanium detectors for noble gas, iodine, and particulate activity. Tritium specific radioactivity is measured using Liquid Scintillation Counting techniques.

The radionuclide concentrations obtained are used in conjunction with the gross noble gas release rate monitoring data collected by the radiation monitoring system to estimate the release rate of each radionuclide in the effluent streams. The noble gas release rate data collected by the unit vent radiation monitor is quantified and reported as continuous mode of release. The data from the unit vent radiation monitor in conjunction with the grab sample results of the Reactor Containment Building atmosphere are used to quantify the radioactive material released.

Analytical Methods for Continuous Gaseous Releases Periodic noble gas and tritium grab samples are taken from the continuous release points, such as the Unit Vent. Continuous sampling for particulates and iodine is also performed on effluent streams. These samples are analyzed for tritium and gamma radionuclides, as described above for gaseous releases. Strontium-89, strontium-90, and gross alpha analyses is performed by the on-site Radiological Services Laboratory.

Noble gas quantification is performed by the plant radiation monitoring system using noble gas grab sample results and the gross noble gas release rate monitor.

The methodology used for estimating the quantity of carbon-14 released to the environment is described in the following section Dose to Member of the Public from Radioactive Effluents Including Carbon-14.

Secondary system liquid grab samples in conjunction with the mass of the secondary coolant lost are used for quantifying secondary steam releases. The radioactive material in the steam is based on grab sample results of the secondary liquid. The secondary liquid is analyzed for gamma emitters and tritium.

Liquid Effluents Analytical Methods for Liquid Releases Liquid batch releases include waste liquid treated by the liquid waste processing system and secondary system chemical regeneration waste. Liquid effluents resulting from primary to secondary leakage or other plant operations are continuously monitored and are tracked as continuous releases. For batch releases, representative pre-release grab samples are taken and analyzed in accordance with Table A3-1 of the Offsite Dose Calculation Manual. For continuous releases, representative samples are collected weekly and analyzed. Radionuclide analyses are performed using a Gamma Spectroscopy System. Aliquots of each pre-release batch sample are composited in accordance with the requirements in Table A3-1 of the Offsite Dose Calculation Manual. Tritium concentrations are determined using Liquid Scintillation Counting techniques. Dissolved and entrained gas concentrations are determined by counting

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-5 grab samples on the Gamma Spectroscopy System. Strontium-89, strontium-90, gross alpha, iron-55, and nickel-63 determinations are performed by the on-site Radiological Environmental Monitoring Laboratory. The radionuclide concentrations obtained are used with the total volume for each batch release.

Batch Releases Liquid and gaseous summaries are compiled from permits generated using a computer-based effluent management system and plant procedures. Liquid batch releases are accounted for by individual permits. Gaseous batch releases are accounted for by monthly permits and consist of reactor containment purges for the purpose of reducing radioactive material concentrations. Batch times represent the actual period of releases and the periods that the purge valves were open.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-6 Liquid (Unit 1)

Liquid (Unit 1)

Quarter 1 Quarter 2 Quarter 3 Quarter 4

a. Number of batch releases 24 11 47 29
b. Total time period for batch releases (minutes) 1439 668 2848 1726
c. Maximum time period for a batch release (minutes) 64 65 66 69
d. Average time period for batch releases (minutes) 60 61 61 60
e. Minimum time period for a batch release (minutes) 58 58 51 38 Gaseous (Unit 1)

Gaseous (Unit 1)

Quarter 1 Quarter 2 Quarter 3 Quarter 4

a. Number of batch releases 0

0 0

11

b. Total time period for batch releases (minutes) 0 0

0 24420

c. Maximum time period for a batch release (minutes) 0 0

0 6840

d. Average time period for batch releases (minutes) 0 0

0 2220

e. Minimum time period for a batch release (minutes) 0 0

0 360 Liquid (Unit 2)

Liquid (Unit 2)

Quarter 1 Quarter 2 Quarter 3 Quarter 4

a. Number of batch releases 41 37 17 8
b. Total time period for batch releases (minutes) 2413 2207 1042 481
c. Maximum time period for a batch release (minutes) 62 63 65 63
d. Average time period for batch releases (minutes) 59 60 61 60
e. Minimum time period for a batch release (minutes) 32 45 48 58

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-7 Gaseous (Unit 2)

Gaseous (Unit 2)

Quarter 1 Quarter 2 Quarter 3 Quarter 4

a. Number of batch releases 4

8 0

0

b. Total time period for batch releases (minutes) 6840 32760 0

0

c. Maximum time period for a batch release (minutes) 3840 10140 0

0

d. Average time period for batch releases (minutes) 1710 4095 0

0

e. Minimum time period for a batch release (minutes) 360 240 0

0 Abnormal (Unplanned) Releases No abnormal releases occurred during this reporting period.

Estimate of Total Error Estimate of Error for Liquid Effluents The maximum error associated with volume and flow measurements, based upon plant calibration practice, is estimated to be + 1.27%. The error associated with the flow measurement is small in relation to the counting uncertainty of the radionuclide concentration analysis.

The average uncertainty associated with counting measurements is 10% or less at the 95%

confidence interval.

The error associated with dilution volume is estimated to be + 10%.

Estimate of Error for Gaseous Effluents The maximum error associated with monitor readings, sample flow, vent flow, sample collection, monitor calibration, and laboratory procedures are collectively estimated to be:

Fission and Activation Gases Low Activity (less than 10 microcurie per second)

+ 100%

Fission and Activation Gases High Activity (greater than or equal to 10 microcurie per second)

+ 20%

Iodines

+ 25%

Particulates

+ 25%

Tritium

+ 50%

The average uncertainty associated with counting measurements is 10% or less at the 95%

confidence interval for fission and activation gases, iodines, particulates, and tritium.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-8 Estimate of Error for Solid Radioactive Waste The potential error associated with solid radioactive waste shipments is estimated to be +/-

20%. This is based on waste stream sampling uncertainty and an industry standard of +/- 20%

for calibration of instrumentation.

Solid Waste Shipments A total of 19 shipments of radioactive filter media, spent resins, dry active waste, irradiated components, and other wastes were made during the reporting period. Additionally, there were 3 shipments of exempt quantities made in 2024. A summary of the data is provided in Section 6, Solid Waste and Irradiated Fuel Shipments. This data is based upon waste generated from Units 1 and 2.

Radiological Impact on Man The data for the period January 1, 2024, through December 31, 2024, is provided in the Dose Accumulation (Section 7) and the Summary of Direct Radiation Table 8-1 (Section 8). The following dilution factors and dilution water flows were used for assessing the radiation doses due to radioactive liquid effluents released to unrestricted areas.

Receptor Location ODCM(1)

Dilution Factor Dilution Water Flow Cubic Feet/Second Dilution Water Flow Liters/Year Dilution Water Flow Liters/Quarter Colorado River 1.00E+00 6.00E+02 5.36E+11 1.34E+11 Matagorda Bay 1.63E+02 9.78E+04 8.73E+13 2.18E+13 Little Robbins Slough Area 3.05E-02 1.83E+01 1.63E+10 4.08E+09 (1) Offsite Dose Calculation Manual factor (Table B4-3).

The dilution water flow used to estimate the individual dose due to ingestion of saltwater fish and saltwater invertebrates (shrimp) harvested from the Colorado River was 5.36E+11 liters per year for the years of 1989 through 2024. The dilution water flow used to estimate the individual dose due to ingestion of saltwater fish and saltwater invertebrates harvested from the Matagorda Bay was 8.73E+13 liters per year for the years of 1993 through 2024 as the result of a diversion channel that routes the Colorado River into Matagorda Bay. The dilution water flow used to estimate the individual dose due to ingestion of freshwater fish from the Little Robbins Slough Area was 1.63E+10 liters per year for the years 1989 through 2024. These dilution water flows were also used for estimating individual dose due to shoreline deposits. The radioactive material reported in the Liquid Effluent tables is the amount released to the Main Cooling Reservoir and does not contribute to dose until the radioactive material is released to unrestricted areas. In order to estimate the doses due to liquid effluents, the radioactive material reported must be adjusted by the values listed in the Offsite Dose Calculation Manual, Table B4-1, Radionuclide Fractions N(i), Reaching Off-site Bodies of Water.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-9 Meteorological Data The 2024 meteorological data is presented in the form of joint frequency tables. Each quarter contains eight tables, one for each stability class and one for all classes combined.

A second set of joint frequency tables is provided for time periods when the reactor containment building fans were operating to remove radioactive material from the containment for personnel protection reasons. These containment purges are classified as batch releases.

Lower Limit of Detection The Lower Limit of Detection (an a priori limit) is defined as the smallest concentration of radioactive material in a sample that will yield a net count above system background that will be detected with 95% probability, and only a 5% probability of falsely concluding that a blank observation represents a "real" signal. A zero (0) value in the attached tables indicates no activity detected.

Dose to Member of the Public Dose to Member of the Public from Direct Radiation Outside the Site Boundary The Offsite Dose Calculation Manual includes the direct radiation from plant structures as a component to the dose to a hypothetical, highest exposed Member of the Public located off site due to plant operations. The Offsite Dose Calculation Manual allows measurements made near the plant structures to be used in these calculations following suitable adjustments for distance and exposure time. In 2024, Thermoluminescent Dosimeters (TLD) and Beryllium Oxide Optically Stimulated Luminescent (BeOSL) dosimeters were placed along the protected area fence or the concrete intrusion barriers surrounding Units 1 and 2 of the South Texas Project, around the Old Steam Generator Storage Facility, Low Level Rad Waste Storage Area, and around the Independent Spent Fuel Storage Installation (ISFSI) pad as pictured in Figure 8-1 of Section 8. The results of these measurements are summarized in Table 8-1 of Section 8.

The table shows that in 2024, dosimeter measurements were typical of previous years readings around the Protected Area and slightly higher near the Independent Spent Fuel Storage Installation (ISFSI) Area compared to the other dosimeters but still below the regulatory limits.

In accordance with the Offsite Dose Calculation Manual, the dose due to direct radiation can be estimated taking the highest dosimeter measurement, minus the background, and correcting for the distance to the site boundary using Dosedirect = TLD * (PA)2 / (RD)2 Where TLD = background corrected TLD or BeOSL annual dose, mR/yr PA = distance from source of radiation to the dosimeter location, meters RD = distance from the source of radiation to the closest site boundary, meters

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-10 The TLD average dose rate is the average of the four quarterly values for the highest location less the quarterly average background at the site boundary. The highest annual average TLD dose rate was 46 mR/quarter for station #39 which is located in the vicinity of Independent Spent Fuel Storage Installation (ISFSI) Area, as shown in Figure 8-1. The value for TLD or BeOSL may be calculated as shown below where the historical site boundary background of 15.4 mR/quarter gamma only is used to find the net rate attributable to waste stored onsite.

Each dosimeter location has background values calculated using ANSI N13.37 methodology, which was used in these calculations.

TLD = 46 mR/quarter for gamma and neutron at ISFSI station # 39 or TLD = (46 mR/quarter) * (4 quarters/yr) = 184 mrem/yr assuming a mR is about equal to a mrem The approximate distances PA and RD are estimated using field measurements and global positioning satellite technology. The total dose to a hypothetical member of the public at the site boundary could be calculated as below:

Dosedirect = (184 mrem/yr) * (40 meters)2 / (1800 meters)2 = 0.091 mrem/yr This assumes someone is positioned permanently at the site boundary fence east of the Units.

A real person might traverse this area twice daily (to and from work) for a total exposure time of Exposure time (hypothetical person) = (250 work days per year) * (4 minutes per trip) *

(2 trips per day)

Exposure time (hypothetical person) = 2000 minutes = 0.00381 yr Dosedirect = 0.091 mrem/yr

  • 0.00381 yr = 0.000347 mrem in 2024 In summary, a realistic measurable dose of 0.0003 mrem was possible to a member of the public offsite in 2024 although a hypothetical maximum annual dose rate of 0.1 mrem/yr was calculated at the nearest offsite location.

Dose to Member of the Public from Direct Radiation Inside the Site Boundary A hypothetical Member of the Public inside the site boundary but outside the protected area fence could receive less than one millirem from direct radiation. The most exposed employee on site who is also a member of the public would be a grounds keeper whose job required him to work in the vicinity east of the Independent Spent Fuel Storage Installation Area (ISFSI)

Area. If such an individual worked 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> once a quarter at the fence where the dose rate was highest, their direct radiation dose could be calculated as follows:

Dose (mrem) = 40 * [61+26+31+65] / 366 / 24 = 0.83 mrem in a year where 40 =

10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> per quarter times four quarters 61 =

dose rate in first quarter, mrem/quarter 26 =

dose rate in second quarter, mrem/quarter 31 =

dose rate in third quarter, mrem/quarter

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-11 65 =

dose rate in fourth quarter, mrem/quarter 366 =

days in a year 24 =

hours per day Hence, in 2024 a hypothetical member of the public with the highest exposure to direct radiation received about 0.83 mrem from direct radiation. This value is considerably less than the EPA 40 CFR 190 limit of 25 mrem/year.

Dose to Member of the Public from Direct Radiation and Radioactive Effluents Inside the Site Boundary A hypothetical Member of the Public outside the protected area fence but inside the site boundary could receive approximately 0.02 millirem from radioactive effluents due to inhalation and immersion. This dose plus the direct radiation dose would yield 0.85 millirem, a small fraction of the 10 CFR 20.1301 annual limit.

Dose to Member of the Public from Radioactive Effluents Outside the Site Boundary using ODCM Exposure Pathways During 2024, the estimated total body dose to a hypothetical Member of the Public with the highest probability for exposure from radioactive effluents and direct radiation was 0.025 millirem. This total represents approximately 0.1% of the limits of 40 CFR 190. Based on our 2024 Land Use Census, real individuals reside in the West by Southwest Sector, approximately 4,000 meters (2.5 miles) from the site. For dose calculation purposes, the residents at this location are characterized as the theoretically highest exposed individual with regard to food consumption, occupancy, and other uses of the areas in the plant vicinity. Our dose model assumes that this theoretically highest exposed individual may consume the maximum amount of food with all the food being grown or grazed at the residence. This individual receives shoreline exposure from Little Robbins Slough for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> per year and consumes 21 kilograms (46 pounds) of fish taken from Little Robbins Slough. This individual receives a submersion dose from noble gases and dose from inhaled radioactive particulates, radioiodines, carbon-14, and tritium. This hypothetical adult is assumed to consume 64 kilograms (140 pounds) of leafy vegetables grown at the residence and consumes 110 kilograms (240 pounds) of meat from livestock grazed at the residence. This estimated total body dose is calculated using models and exposure pathways described in our ODCM for a hypothetical individual offsite. Other dose estimates for Members of the Public onsite are listed in the report using exposure pathways not addressed by standard dose calculation methods.

Dose to Member of the Public from Radioactive Effluents Outside the Site Boundary using Liquid to Gaseous Receptor Exposure Pathways Consistent with normal operation of the units, approximately 2300 Curies of tritium were released to the Main Cooling Reservoir during 2024. Since some portion of the tritium released in liquid effluents evaporates from the Main Cooling Reservoir, this section is included to provide an estimate of offsite dose from that gaseous source per section 4.10 of the ODCM.

The Main Cooling Reservoir, with a surface area of about 28,300,000 square meters (7000 acres), is an area source and contributes tritium to the atmosphere. The atmospheric dispersion

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Supplemental Information for Effluent and Waste Disposal 2-12 factor for the WSW sector at 4000 meters was estimated to be 4.01E-07 seconds per cubic meter using the EPA code Iclt3 and 2004 meteorological data.

The product of X/Q, tritium released to the MCR, and the dose factor for a population age group (87.9, 91.7, 114.2, or 20.5 millirem-cubic meter per second-curie for age groups adult, teen, child and infant, respectively) generated an estimated whole body dose of 0.08 millirem for the highest exposed population group, a small fraction of the limits of 40 CFR 190.

Dose to Member of the Public from Radioactive Effluents including Carbon-14 Carbon-14 was reported as a radioactive effluent in 2010 for the first time. Carbon-14 is a naturally occurring isotope of carbon. Carbon-14 is formed naturally in the upper atmosphere and is also formed in an operating nuclear reactor, primarily through activation of oxygen molecules. The quantity of carbon-14 produced by operating nuclear reactors is significantly less than that produced naturally or from weapons testing.

The NRC published Regulatory Guide 1.21 Revision 1, Measuring, Evaluating, and Reporting Radioactivity in Solid Wastes and Releases of Radioactive Materials in Liquid and Gaseous Effluents from Light-Water-Cooled Nuclear Power Plants in 1974. This regulatory guidance recommends the content and format of this report. This report follows the recommendations of Regulatory Guide 1.21, Revision 1. In 2009, the NRC published revision 2 of Regulatory Guide 1.21 based on a risk-informed perspective for reporting principal radionuclides. This document recommended methods for estimating and reporting the quantity of carbon-14 released in gaseous effluents. The quantity of carbon-14 released from each unit was estimated using NUREG-0017, Calculation of Releases of Radioactive Materials in Gaseous and Liquid Effluents from Pressurized Water Reactors PWR-GALE Code, April 1985. A value of 7.3 curies of carbon-14 was used for each unit. The Semiannual Summation of All Releases by Quarter for All Airborne Effluents found in section 4-2 of this report lists carbon-14 in a similar manner as tritium.

ODCM dose factors were used for estimating doses to Members of the Public and the doses due to carbon-14 are included in the Dose Accumulations, Section 7-1 of this report. EPRI Report TR-105715, Characterization of Carbon-14 Generated by the Nuclear Power Industry, November 1995 concluded that the molecular form of carbon-14 produced in gaseous effluent is 75 to 90 percent hydrocarbons (primarily methane) with the remainder in inorganic form (carbon dioxide or carbon monoxide in gas or carbonates in liquid). This report listed the measured molecular forms of carbon-14 in gaseous effluents from two U.S. and six German commercial pressurized water reactors. The average fraction of inorganic carbon-14 was determined to be 20 percent, and the average organic fraction was determined to be 80 percent.

The pathway doses were calculated using the average ratio of 1:5 for ingestion pathways, as carbon in the form of hydrocarbons is not absorbed by plants. The radiation doses from STP to the public (including carbon-14) are much lower than regulatory limits and are a very small contributor to the total radiation dose the American public receives each year from natural and manmade sources.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Technical Specifications and Offsite Dose Calculation Manual Controls Reporting Requirements 3-1 Technical Specifications and Offsite Dose Calculation Manual Controls Reporting Requirements

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Technical Specifications and Offsite Dose Calculation Manual Controls Reporting Requirements 3-2 Offsite Dose Calculation Manual Changes (reference, Technical Specifications, 6.13)

The ODCM was not revised since issuance of the 2022 Radioactive Effluent Release Report.

Annual Land Use Census (reference, Offsite Dose Calculation Manual Controls, 3.12.2.a)

The Land Use Census verified current nearest residents within five miles. No new residents or receptors were identified within five miles of the site.

Radioactive Waste Treatment System Design Modification Description (reference, Offsite Dose Calculation Manual Controls, 6.15)

A review of the work history for 2024 for the solid, liquid, and gaseous waste processing systems revealed that no major modifications were installed on these systems in 2024.

Inoperable Effluent Monitoring Instrumentation Explanation (reference, Offsite Dose Calculation Manual Controls, 6.9.1.4)

For 2024, inoperable liquid and gaseous effluent monitoring instruments were corrected within the time specified in sections 3.3.3.10 and 3.3.3.11 of offsite dose calculation manual controls.

Gas Storage Tank Curie Limit Violation Description (reference, Offsite Dose Calculation Manual Controls, 6.9.1.4)

The Reactor Coolant System (RCS) Vacuum Degassing System was not used during this reporting period. Therefore, the quantity of radioactive material in the RCS Vacuum Degassing System Storage Tanks did not exceed the limits set forth in Section 3.11.2.6 of Technical Specifications.

Unprotected Outdoor Tank Curie Limit Violation Description (reference, Offsite Dose Calculation Manual Controls, 6.9.1.4)

There are no Unprotected Outdoor Tanks at South Texas Project. Therefore, the quantity of radioactive material in any unprotected outdoor tank did not exceed the limit set forth in Section 3.11.1.4 of Technical Specifications.

Abnormal (Unplanned) Release Description (reference, Offsite Dose Calculation Manual, 6.9.1.4)

No abnormal (unplanned) releases occurred during this reporting period.

Radioactive Waste Process Control Program Changes (reference, Technical Specifications, 6.13)

There were no changes made to the Radioactive Waste Process Control Program during this reporting period.

Independent Spent Fuel Storage Installation (ISFSI)

There are no radiological effluents released from the ISFSI. Direct dose from the ISFSI is documented in table 8-1 of this report.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Radiological Data Tab Radiological Data Tab

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Radiological Data Tab Intentionally Left Blank

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-1 Gaseous Effluents

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-2 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL AIRBORNE EFFLUENTS Unit: 1 Starting: 1-Jan-2024 Ending: 30-Jun-2024 TYPE OF EFFLUENT UNITS QUARTER 1 QUARTER 2 EST. TOT ERROR A. FISSION & ACTIVATION GASES

1. TOTAL RELEASE CURIES 5.87E-01 5.03E-01 100
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 7.47E-02 6.40E-02
3. PERCENT OF LIMIT (9.60E+04 uCi/sec) 7.78E-05 6.66E-05 B. RADIOIODINES
1. IODINE-131 CURIES 0.00E+00 0.00E+00 25
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 0.00E+00 0.00E+00
3. PERCENT OF LIMIT (4.00E-02 uCi/sec) 0.00E+00 0.00E+00 C. PARTICULATES
1. PARTICULATES(HALF-LIVES>8 DAYS)

CURIES 7.77E-06 5.56E-06 25

2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 9.88E-07 7.07E-07
3. PERCENT OF LIMIT (3.00E-01 uCi/sec) 3.29E-04 2.36E-04
4. GROSS ALPHA RADIOACTIVITY CURIES 0.00E+00 0.00E+00 D. TRITIUM
1. TOTAL RELEASE CURIES 2.32E+01 6.96E+00 50
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.95E+00 8.85E-01
3. PERCENT OF LIMIT (1.80E+05 uCi/sec) 1.64E-03 4.92E-04 E. CARBON-14
1. TOTAL RELEASE CURIES 1.81E+00 1.82E+00 None
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.30E-01 2.31E-01
3. PERCENT OF LIMIT (7.8E+03 uCi/sec) 2.95E-03 2.97E-03

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-3 STP NUCLEAR OPERATING COMPANY Unit 1 REPORT CATEGORY: SEMIANNUAL AIRBORNE GROUND LEVEL CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: FISSION GASES, IODINES, AND PARTICULATES REPORTING PERIOD: QUARTER # 1 AND QUARTER # 2 YEAR 2024 CONTINUOUS MODE BATCH MODE NUCLIDES RELEASED UNITS QUARTER 1 QUARTER 2 QUARTER 1 QUARTER 2 FISSION GASES Argon-41 CURIES 3.87E-01 2.97E-01 0.00E+00 0.00E+00 Xenon-133 CURIES 2.00E-01 2.06E-01 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 5.87E-01 5.03E-01 0.00E+00 0.00E+00 IODINES Iodine-131 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-132 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-133 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 PARTICULATES Beryllium-7 CURIES 7.77E-06 5.56E-06 0.00E+00 0.00E+00 Cobalt-58 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Cobalt-60 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Chromium-51 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iron-59 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Manganese-54 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Niobium-95 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Antimony-124 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Selenium-75 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Tin-113 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zinc-65 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zirconium-95 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 7.77E-06 5.56E-06 0.00E+00 0.00E+00 OTHER Carbon-14 CURIES 1.81E+00 1.82E+00 0.00E+00 0.00E+00 Hydrogen-3 (Tritium)

CURIES 2.32E+01 6.96E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 2.50E+01 8.77E+00 0.00E+00 0.00E+00

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-4 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL AIRBORNE EFFLUENTS Unit: 1 Starting: 1-Jul-2024 Ending: 31-Dec-2024 TYPE OF EFFLUENT UNITS QUARTER 3 QUARTER 4 EST. TOT ERROR A. FISSION & ACTIVATION GASES

1. TOTAL RELEASE CURIES 6.01E-01 1.78E+00 100
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 7.56E-02 2.24E-01
3. PERCENT OF LIMIT (9.60E+04 uCi/sec) 7.87E-05 2.33E-04 B. RADIOIODINES
1. IODINE-131 CURIES 0.00E+00 1.56E-05 25
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 0.00E+00 1.96E-06
3. PERCENT OF LIMIT (4.00E-02 uCi/sec) 0.00E+00 4.91E-03 C. PARTICULATES
1. PARTICULATES(HALF-LIVES>8 DAYS)

CURIES 0.00E+00 2.09E-04 25

2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 0.00E+00 2.63E-05
3. PERCENT OF LIMIT (3.00E-01 uCi/sec) 0.00E+00 8.77E-03
4. GROSS ALPHA RADIOACTIVITY CURIES 0.00E+00 0.00E+00 D. TRITIUM
1. TOTAL RELEASE CURIES 1.25E+01 6.06E+00 50
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 1.57E+00 7.62E-01
3. PERCENT OF LIMIT (1.80E+05 uCi/sec) 8.74E-04 4.23E-04 E. CARBON-14
1. TOTAL RELEASE CURIES 1.84E+00 1.84E+00 None
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.31E-01 2.31E-01
3. PERCENT OF LIMIT (7.8E+03 uCi/sec) 2.97E-03 2.96E-03

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-5 STP NUCLEAR OPERATING COMPANY Unit 1 REPORT CATEGORY: SEMIANNUAL AIRBORNE GROUND LEVEL CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: FISSION GASES, IODINES, AND PARTICULATES REPORTING PERIOD: QUARTER # 3 AND QUARTER # 4 YEAR 2024 CONTINUOUS MODE BATCH MODE NUCLIDES RELEASED UNITS QUARTER 3 QUARTER 4 QUARTER 3 QUARTER 4 FISSION GASES Argon-41 CURIES 3.89E-01 1.40E-01 0.00E+00 1.46E+00 Xenon-133 CURIES 2.12E-01 1.79E-01 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 6.01E-01 3.19E-01 0.00E+00 1.46E+00 IODINES Iodine-131 CURIES 0.00E+00 5.93E-06 0.00E+00 9.69E-06 Iodine-132 CURIES 0.00E+00 1.73E-04 0.00E+00 8.62E-05 Iodine-133 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 0.00E+00 1.79E-04 0.00E+00 9.58E-05 PARTICULATES Beryllium-7 CURIES 0.00E+00 2.08E-06 0.00E+00 0.00E+00 Cobalt-58 CURIES 0.00E+00 9.22E-06 0.00E+00 2.94E-05 Cobalt-60 CURIES 0.00E+00 5.00E-06 0.00E+00 1.56E-05 Chromium-51 CURIES 0.00E+00 2.57E-05 0.00E+00 8.56E-05 Iron-59 CURIES 0.00E+00 1.92E-08 0.00E+00 1.06E-06 Manganese-54 CURIES 0.00E+00 1.15E-06 0.00E+00 3.25E-06 Niobium-95 CURIES 0.00E+00 4.73E-06 0.00E+00 1.57E-05 Antimony-124 CURIES 0.00E+00 4.00E-09 0.00E+00 2.21E-07 Selenium-75 CURIES 0.00E+00 7.94E-10 0.00E+00 3.33E-08 Tin-113 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zinc-65 CURIES 0.00E+00 9.67E-09 0.00E+00 5.34E-07 Zirconium-95 CURIES 0.00E+00 2.37E-06 0.00E+00 7.94E-06 TOTAL FOR PERIOD CURIES 0.00E+00 5.02E-05 0.00E+00 1.59E-04 OTHER Carbon-14 CURIES 1.84E+00 1.52E+00 0.00E+00 3.17E-01 Hydrogen-3 (Tritium)

CURIES 1.25E+01 4.85E+00 0.00E+00 1.21E+00 TOTAL FOR PERIOD CURIES 1.43E+01 6.37E+00 0.00E+00 1.53E+00

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-6 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL AIRBORNE EFFLUENTS Unit: 2 Starting: 1-Jan-2024 Ending: 30-Jun-2024 TYPE OF EFFLUENT UNITS QUARTER 1 QUARTER 2 EST. TOT ERROR A. FISSION & ACTIVATION GASES

1. TOTAL RELEASE CURIES 3.41E+02 2.74E+02 20
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 4.34E+01 3.49E+01
3. PERCENT OF LIMIT (9.60E+04 uCi/sec) 4.52E-02 3.63E-02 B. RADIOIODINES
1. IODINE-131 CURIES 2.03E-03 2.59E-03 25
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.58E-04 3.30E-04
3. PERCENT OF LIMIT (4.00E-02 uCi/sec) 6.46E-01 8.24E-01 C. PARTICULATES
1. PARTICULATES(HALF-LIVES>8 DAYS)

CURIES 1.38E-04 1.15E-04 25

2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 1.75E-05 1.47E-05
3. PERCENT OF LIMIT (3.00E-01 uCi/sec) 5.83E-03 4.89E-03
4. GROSS ALPHA RADIOACTIVITY CURIES 0.00E+00 0.00E+00 D. TRITIUM
1. TOTAL RELEASE CURIES 2.32E+01 1.06E+01 50
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.95E+00 1.34E+00
3. PERCENT OF LIMIT (1.80E+05 uCi/sec) 1.64E-03 7.45E-04 E. CARBON-14
1. TOTAL RELEASE CURIES 1.82E+00 1.81E+00 None
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.31E-01 2.31E-01
3. PERCENT OF LIMIT (7.8E+03 uCi/sec) 2.96E-03 2.96E-03

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-7 STP NUCLEAR OPERATING COMPANY Unit 2 REPORT CATEGORY: SEMIANNUAL AIRBORNE GROUND LEVEL CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: FISSION GASES, IODINES, AND PARTICULATES REPORTING PERIOD: QUARTER # 1 AND QUARTER # 2 YEAR 2024 CONTINUOUS MODE BATCH MODE NUCLIDES RELEASED UNITS QUARTER 1 QUARTER 2 QUARTER 1 QUARTER 2 FISSION GASES Argon-41 CURIES 6.11E+00 6.84E-02 3.59E+01 2.60E+00 Xenon-133 CURIES 2.97E+02 2.07E+02 2.37E+00 6.49E+01 TOTAL FOR PERIOD CURIES 3.03E+02 2.07E+02 3.83E+01 6.75E+01 IODINES Iodine-131 CURIES 7.91E-04 6.90E-04 1.24E-03 1.90E-03 Iodine-132 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-133 CURIES 6.68E-05 0.00E+00 3.87E-05 0.00E+00 TOTAL FOR PERIOD CURIES 8.58E-04 6.90E-04 1.28E-03 1.90E-03 PARTICULATES Beryllium-7 CURIES 1.54E-05 0.00E+00 0.00E+00 0.00E+00 Cobalt-58 CURIES 8.64E-06 8.69E-06 1.16E-05 1.15E-05 Cobalt-60 CURIES 8.65E-06 6.03E-06 9.15E-06 7.78E-06 Chromium-51 CURIES 3.18E-05 3.19E-05 4.27E-05 4.01E-05 Iron-59 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Manganese-54 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Niobium-95 CURIES 2.98E-06 3.00E-06 4.00E-06 3.96E-06 Antimony-124 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Selenium-75 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Tin-113 CURIES 7.10E-08 0.00E+00 1.07E-08 0.00E+00 Zinc-65 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zirconium-95 CURIES 1.04E-06 1.04E-06 1.40E-06 1.16E-06 TOTAL FOR PERIOD CURIES 6.86E-05 5.07E-05 6.89E-05 6.46E-05 OTHER Carbon-14 CURIES 1.71E+00 1.35E+00 1.05E-01 4.63E-01 Hydrogen-3 (Tritium)

CURIES 1.92E+01 5.81E+00 4.03E+00 4.74E+00 TOTAL FOR PERIOD CURIES 2.09E+01 7.16E+00 4.14E+00 5.20E+00

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-8 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL AIRBORNE EFFLUENTS Unit: 2 Starting: 1-Jul-2024 Ending: 31-Dec-2024 TYPE OF EFFLUENT UNITS QUARTER 3 QUARTER 4 EST. TOT ERROR A. FISSION & ACTIVATION GASES

1. TOTAL RELEASE CURIES 2.66E+02 2.05E+02 20
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 3.35E+01 2.57E+01
3. PERCENT OF LIMIT (9.60E+04 uCi/sec) 3.49E-02 2.68E-02 B. RADIOIODINES
1. IODINE-131 CURIES 1.66E-08 8.98E-09 25
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.09E-09 1.13E-09
3. PERCENT OF LIMIT (4.00E-02 uCi/sec) 5.22E-06 2.83E-06 C. PARTICULATES
1. PARTICULATES(HALF-LIVES>8 DAYS)

CURIES 0.00E+00 7.03E-06 25

2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 0.00E+00 8.84E-07
3. PERCENT OF LIMIT (3.00E-01 uCi/sec) 0.00E+00 2.95E-04
4. GROSS ALPHA RADIOACTIVITY CURIES 0.00E+00 0.00E+00 D. TRITIUM
1. TOTAL RELEASE CURIES 5.87E+00 1.85E+01 50
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 7.39E-01 2.33E+00
3. PERCENT OF LIMIT (1.80E+05 uCi/sec) 4.10E-04 1.29E-03 E. CARBON-14
1. TOTAL RELEASE CURIES 1.84E+00 1.84E+00 None
2. AVERAGE RELEASE RATE FOR PERIOD uCi/sec 2.31E-01 2.31E-01
3. PERCENT OF LIMIT (7.8E+03 uCi/sec) 2.97E-03 2.97E-03

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-9 STP NUCLEAR OPERATING COMPANY Unit 2 REPORT CATEGORY: SEMIANNUAL AIRBORNE GROUND LEVEL CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: FISSION GASES, IODINES, AND PARTICULATES REPORTING PERIOD: QUARTER # 3 AND QUARTER # 4 YEAR 2024 CONTINUOUS MODE BATCH MODE NUCLIDES RELEASED UNITS QUARTER 3 QUARTER 4 QUARTER 3 QUARTER 4 FISSION GASES Argon-41 CURIES 3.06E-01 3.46E-01 0.00E+00 0.00E+00 Xenon-133 CURIES 2.66E+02 2.04E+02 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 2.66E+02 2.05E+02 0.00E+00 0.00E+00 IODINES Iodine-131 CURIES 1.66E-08 8.98E-09 0.00E+00 0.00E+00 Iodine-132 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-133 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 1.66E-08 8.98E-09 0.00E+00 0.00E+00 PARTICULATES Beryllium-7 CURIES 0.00E+00 7.03E-06 0.00E+00 0.00E+00 Cobalt-58 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Cobalt-60 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Chromium-51 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iron-59 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Manganese-54 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Niobium-95 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Antimony-124 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Selenium-75 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Tin-113 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zinc-65 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Zirconium-95 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 0.00E+00 7.03E-06 0.00E+00 0.00E+00 OTHER Carbon-14 CURIES 1.84E+00 1.84E+00 0.00E+00 0.00E+00 Hydrogen-3 (Tritium)

CURIES 5.87E+00 1.85E+01 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 7.71E+00 2.03E+01 0.00E+00 0.00E+00

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Gaseous Effluents 4-10 STP NUCLEAR OPERATING COMPANY Unit 1 plus 2 Total REPORT CATEGORY: ANNUAL AIRBORNE GROUND LEVEL RELEASES.

TOTALS FOR EACH NUCLIDE RELEASED. FOR ALL OF 2024 NUCLIDES RELEASED UNITS UNIT 1 2024 UNIT 2 2024 TOTAL 2024 FISSION GASES Argon-41 CURIES 2.67E+00 4.54E+01 4.80E+01 Xenon-133 CURIES 7.95E-01 1.04E+03 1.04E+03 TOTAL FOR PERIOD CURIES 3.47E+00 1.08E+03 1.09E+03 IODINES Iodine-131 CURIES 1.56E-05 4.62E-03 4.64E-03 Iodine-132 CURIES 2.59E-04 0.00E+00 2.59E-04 Iodine-133 CURIES 0.00E+00 1.06E-04 1.06E-04 TOTAL FOR PERIOD CURIES 2.74E-04 4.73E-03 5.00E-03 PARTICULATES Beryllium-7 CURIES 1.54E-05 2.25E-05 3.79E-05 Cobalt-58 CURIES 3.86E-05 4.05E-05 7.91E-05 Cobalt-60 CURIES 2.06E-05 3.16E-05 5.22E-05 Chromium-51 CURIES 1.11E-04 1.47E-04 2.58E-04 Iron-59 CURIES 1.08E-06 0.00E+00 1.08E-06 Manganese-54 CURIES 4.40E-06 0.00E+00 4.40E-06 Niobium-95 CURIES 2.04E-05 1.39E-05 3.43E-05 Antimony-124 CURIES 2.25E-07 0.00E+00 2.25E-07 Selenium-75 CURIES 3.41E-08 0.00E+00 3.41E-08 Tin-113 CURIES 0.00E+00 8.17E-08 8.17E-08 Zinc-65 CURIES 5.44E-07 0.00E+00 5.44E-07 Zirconium-95 CURIES 1.03E-05 4.64E-06 1.50E-05 TOTAL FOR PERIOD CURIES 2.23E-04 2.60E-04 4.83E-04 OTHER Carbon-14 CURIES 7.31E+00 7.31E+00 1.46E+01 Hydrogen-3 (Tritium)

CURIES 4.86E+01 5.78E+01 1.06E+02 TOTAL FOR PERIOD CURIES 5.59E+01 6.51E+01 1.21E+02

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-1 Liquid Effluents

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-2 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL LIQUID EFFLUENTS Unit: 1 Starting: 1-Jan-2024 Ending: 30-Jun-2024 TYPE OF EFFLUENT UNITS QUARTER 1 QUARTER 2 EST. TOT ERROR %

A. FISSION & ACTIVATION PRODUCTS

1. TOTAL RELEASE (NOT INCLUDING TRITIUM, GASES, ALPHA)

CURIES 8.40E-04 3.55E-04 10

2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 4.13E-10 3.17E-10
3. PERCENT OF EC* LIMIT (FRACTIONAL) 8.62E-04 3.92E-04 B. TRITIUM
1. TOTAL RELEASE CURIES 7.81E+02 1.17E+02 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 3.84E-04 1.05E-04
3. % OF LIMIT (1.00E-02 uCi/mL) 3.84E+00 1.05E+00 C. DISSOLVED AND ENTRAINED GASES
1. TOTAL RELEASE CURIES 1.48E-03 7.64E-05 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 7.27E-10 6.81E-11
3. PERCENT OF LIMIT (2.00E-04 uCi/mL) 3.64E-04 3.41E-05 D. GROSS ALPHA RADIOACTIVITY
1. TOTAL RELEASE CURIES 0.00E+00 0.00E+00 10 E. WASTE VOL RELEASED
1. TOTAL PRE-DILUTION VOLUME LITERS 3.72E+06 4.34E+06 1
2. BATCH PRE-DILUTION VOLUME LITERS 1.33E+06 6.14E+05 F. VOLUME OF DILUTION WATER USED**

LITERS 2.03E+09 1.12E+09

  • EC= Effluent Concentration
    • Volume of dilution water used means the volume of water circulated through the main condenser during the actual time of release. Liquid effluent releases ultimately dilute into the volume of the onsite main cooling reservoir and then into offsite water bodies as described in Section 2, subsection Radiological Impact on Man of this report.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-3 STP NUCLEAR OPERATING COMPANY Unit 1 REPORT CATEGORY: SEMIANNUAL LIQUID CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: ALL RADIONUCLIDES REPORTING PERIOD: QUARTER # 1 AND QUARTER # 2 YEAR 2024 CONTINUOUS RELEASES BATCH RELEASES NUCLIDES RELEASED UNITS QUARTER 1 QUARTER 2 QUARTER 1 QUARTER 2 ALL NUCLIDES Cobalt-58 CURIES 0.00E+00 0.00E+00 1.68E-05 0.00E+00 Cobalt-60 CURIES 0.00E+00 0.00E+00 5.02E-04 1.07E-04 Iron-55 CURIES 0.00E+00 0.00E+00 1.35E-04 2.19E-05 Tritium CURIES 1.35E-02 5.40E-03 7.81E+02 1.17E+02 Mercury-203 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-131 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Krypton-85 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Krypton-85m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Manganese-54 CURIES 0.00E+00 0.00E+00 1.23E-05 7.70E-07 Molybdenum-99 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Nickel-63 CURIES 0.00E+00 0.00E+00 6.61E-05 0.00E+00 Ruthenium-106 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Antimony-124 CURIES 0.00E+00 0.00E+00 1.96E-07 4.79E-06 Antimony-125 CURIES 0.00E+00 0.00E+00 5.45E-05 2.21E-04 Tin-117m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Technetium-99m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Tellurium-125m CURIES 0.00E+00 0.00E+00 5.34E-05 0.00E+00 Xenon-131m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-133 CURIES 0.00E+00 0.00E+00 1.37E-03 7.64E-05 Xenon-133m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-135 CURIES 0.00E+00 0.00E+00 1.05E-04 0.00E+00 TOTAL FOR PERIOD CURIES 1.35E-02 5.40E-03 7.81E+02 1.17E+02

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-4 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL LIQUID EFFLUENTS Unit: 1 Starting: 1-Jul-2024 Ending: 31-Dec-2024 TYPE OF EFFLUENT UNITS QUARTER 3 QUARTER 4 EST. TOT ERROR %

A. FISSION & ACTIVATION PRODUCTS

1. TOTAL RELEASE (NOT INCLUDING TRITIUM, GASES, ALPHA)

CURIES 1.04E-02 1.25E-03 10

2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 2.17E-09 4.25E-10
3. PERCENT OF EC* LIMIT (FRACTIONAL) 4.24E-04 1.37E-04 B. TRITIUM
1. TOTAL RELEASE CURIES 4.29E+02 6.61E+01 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 8.98E-05 2.25E-05
3. % OF LIMIT (1.00E-02 uCi/mL) 8.98E-01 2.25E-01 C. DISSOLVED AND ENTRAINED GASES
1. TOTAL RELEASE CURIES 2.15E-03 1.99E-04 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 4.51E-10 6.77E-11
3. PERCENT OF LIMIT (2.00E-04 uCi/mL) 2.25E-04 3.39E-05 D. GROSS ALPHA RADIOACTIVITY
1. TOTAL RELEASE CURIES 0.00E+00 0.00E+00 10 E. WASTE VOL RELEASED
1. TOTAL PRE-DILUTION VOLUME LITERS 6.34E+06 7.11E+06 1
2. BATCH PRE-DILUTION VOLUME LITERS 2.60E+06 1.59E+06 F. VOLUME OF DILUTION WATER USED**

LITERS 4.77E+09 2.93E+09

  • EC= Effluent Concentration
    • Volume of dilution water used means the volume of water circulated through the main condenser during the actual time of release. Liquid effluent releases ultimately dilute into the volume of the onsite main cooling reservoir and then into offsite water bodies as described in Section 2, subsection Radiological Impact on Man of this report.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-5 STP NUCLEAR OPERATING COMPANY Unit 1 REPORT CATEGORY: SEMIANNUAL LIQUID CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: ALL RADIONUCLIDES REPORTING PERIOD: QUARTER # 3 AND QUARTER # 4 YEAR 2024 CONTINUOUS RELEASES BATCH RELEASES NUCLIDES RELEASED UNITS QUARTER 3 QUARTER 4 QUARTER 3 QUARTER 4 ALL NUCLIDES Cobalt-58 CURIES 0.00E+00 0.00E+00 5.13E-05 1.27E-04 Cobalt-60 CURIES 0.00E+00 0.00E+00 2.75E-04 3.14E-05 Iron-55 CURIES 0.00E+00 0.00E+00 3.53E-04 8.16E-04 Tritium CURIES 3.54E-03 3.88E-03 4.29E+02 6.61E+01 Mercury-203 CURIES 0.00E+00 0.00E+00 1.50E-07 0.00E+00 Iodine-131 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Krypton-85 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Krypton-85m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Manganese-54 CURIES 0.00E+00 0.00E+00 1.11E-06 0.00E+00 Molybdenum-99 CURIES 0.00E+00 0.00E+00 0.00E+00 1.16E-07 Nickel-63 CURIES 0.00E+00 0.00E+00 9.44E-03 2.51E-05 Ruthenium-106 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Antimony-124 CURIES 0.00E+00 0.00E+00 1.82E-05 6.08E-05 Antimony-125 CURIES 0.00E+00 0.00E+00 2.17E-04 1.85E-04 Tin-117m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Technetium-99m CURIES 0.00E+00 0.00E+00 0.00E+00 1.13E-07 Tellurium-125m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-131m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-133 CURIES 0.00E+00 0.00E+00 2.15E-03 1.94E-04 Xenon-133m CURIES 0.00E+00 0.00E+00 3.01E-07 0.00E+00 Xenon-135 CURIES 0.00E+00 0.00E+00 3.22E-06 4.31E-06 TOTAL FOR PERIOD CURIES 3.54E-03 3.88E-03 4.29E+02 6.61E+01

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-6 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL LIQUID EFFLUENTS Unit: 2 Starting: 1-Jan-2024 Ending: 30-Jun-2024 TYPE OF EFFLUENT UNITS QUARTER 1 QUARTER 2 EST. TOT ERROR %

A. FISSION & ACTIVATION PRODUCTS

1. TOTAL RELEASE (NOT INCLUDING TRITIUM, GASES, ALPHA)

CURIES 1.85E-03 2.83E-03 10

2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 5.97E-10 8.90E-10
3. PERCENT OF EC* LIMIT (FRACTIONAL) 4.51E-04 5.37E-03 B. TRITIUM
1. TOTAL RELEASE CURIES 6.37E+02 1.42E+02 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 2.05E-04 4.46E-05
3. % OF LIMIT (1.00E-02 uCi/mL) 2.05E+00 4.46E-01 C. DISSOLVED AND ENTRAINED GASES
1. TOTAL RELEASE CURIES 4.64E-01 3.12E-01 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 1.49E-07 9.80E-08
3. PERCENT OF LIMIT (2.00E-04 uCi/mL) 7.47E-02 4.90E-02 D. GROSS ALPHA RADIOACTIVITY
1. TOTAL RELEASE CURIES 0.00E+00 0.00E+00 10 E. WASTE VOL RELEASED
1. TOTAL PRE-DILUTION VOLUME LITERS 9.57E+06 6.78E+06 1
2. BATCH PRE-DILUTION VOLUME LITERS 2.28E+06 2.04E+06 F. VOLUME OF DILUTION WATER USED**

LITERS 3.10E+09 3.18E+09

  • EC= Effluent Concentration
    • Volume of dilution water used means the volume of water circulated through the main condenser during the actual time of release. Liquid effluent releases ultimately dilute into the volume of the onsite main cooling reservoir and then into offsite water bodies as described in Section 2, subsection Radiological Impact on Man of this report.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-7 STP NUCLEAR OPERATING COMPANY Unit 2 REPORT CATEGORY: SEMIANNUAL LIQUID CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: ALL RADIONUCLIDES REPORTING PERIOD: QUARTER # 1 AND QUARTER # 2 YEAR 2024 CONTINUOUS RELEASES BATCH RELEASES NUCLIDES RELEASED UNITS QUARTER 1 QUARTER 2 QUARTER 1 QUARTER 2 ALL NUCLIDES Cobalt-58 CURIES 0.00E+00 0.00E+00 5.89E-06 1.76E-05 Cobalt-60 CURIES 0.00E+00 0.00E+00 3.00E-04 1.71E-05 Iron-55 CURIES 0.00E+00 0.00E+00 5.83E-04 5.10E-05 Tritium CURIES 2.93E-02 7.75E-03 6.36E+02 1.42E+02 Mercury-203 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-131 CURIES 0.00E+00 0.00E+00 1.12E-06 1.63E-03 Krypton-85 CURIES 0.00E+00 0.00E+00 0.00E+00 1.14E-03 Krypton-85m CURIES 0.00E+00 0.00E+00 0.00E+00 2.27E-06 Manganese-54 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Molybdenum-99 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Nickel-63 CURIES 0.00E+00 0.00E+00 6.18E-05 0.00E+00 Ruthenium-106 CURIES 0.00E+00 0.00E+00 0.00E+00 2.26E-06 Antimony-124 CURIES 0.00E+00 0.00E+00 0.00E+00 3.12E-04 Antimony-125 CURIES 0.00E+00 0.00E+00 7.72E-04 8.04E-04 Tin-117m CURIES 0.00E+00 0.00E+00 0.00E+00 1.63E-07 Technetium-99m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Tellurium-125m CURIES 0.00E+00 0.00E+00 1.30E-04 0.00E+00 Xenon-131m CURIES 0.00E+00 0.00E+00 2.50E-03 1.28E-02 Xenon-133 CURIES 0.00E+00 0.00E+00 4.58E-01 2.98E-01 Xenon-133m CURIES 0.00E+00 0.00E+00 2.78E-03 0.00E+00 Xenon-135 CURIES 0.00E+00 0.00E+00 1.66E-04 5.94E-05 TOTAL FOR PERIOD CURIES 2.93E-02 7.75E-03 6.37E+02 1.42E+02

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-8 STP NUCLEAR OPERATING COMPANY SEMIANNUAL SUMMATION OF ALL RELEASES BY QUARTER ALL LIQUID EFFLUENTS Unit: 2 Starting: 1-Jul-2024 Ending: 31-Dec-2024 TYPE OF EFFLUENT UNITS QUARTER 3 QUARTER 4 EST. TOT ERROR %

A. FISSION & ACTIVATION PRODUCTS

1. TOTAL RELEASE (NOT INCLUDING TRITIUM, GASES, ALPHA)

CURIES 2.23E-03 4.06E-03 10

2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 1.25E-09 5.24E-09
3. PERCENT OF EC* LIMIT (FRACTIONAL) 5.10E-04 1.10E-03 B. TRITIUM
1. TOTAL RELEASE CURIES 5.40E+01 4.47E+01 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 3.02E-05 5.77E-05
3. % OF LIMIT (1.00E-02 uCi/mL) 3.02E-01 5.77E-01 C. DISSOLVED AND ENTRAINED GASES
1. TOTAL RELEASE CURIES 4.78E-05 0.00E+00 10
2. AVERAGE DILUTED CONCENTRATION DURING PERIOD uCi/mL 2.67E-11 0.00E+00
3. PERCENT OF LIMIT (2.00E-04 uCi/mL) 1.34E-05 0.00E+00 D. GROSS ALPHA RADIOACTIVITY
1. TOTAL RELEASE CURIES 0.00E+00 0.00E+00 10 E. WASTE VOL RELEASED
1. TOTAL PRE-DILUTION VOLUME LITERS 5.45E+06 3.53E+06 1
2. BATCH PRE-DILUTION VOLUME LITERS 9.43E+05 4.45E+05 F. VOLUME OF DILUTION WATER USED**

LITERS 1.78E+09 7.71E+08

  • EC= Effluent Concentration
    • Volume of dilution water used means the volume of water circulated through the main condenser during the actual time of release. Liquid effluent releases ultimately dilute into the volume of the onsite main cooling reservoir and then into offsite water bodies as described in Section 2, subsection Radiological Impact on Man of this report.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-9 STP NUCLEAR OPERATING COMPANY Unit 2 REPORT CATEGORY: SEMIANNUAL LIQUID CONTINUOUS AND BATCH RELEASES. TOTALS FOR EACH NUCLIDE RELEASED.

TYPE OF ACTIVITY: ALL RADIONUCLIDES REPORTING PERIOD: QUARTER # 3 AND QUARTER # 4 YEAR 2024 CONTINUOUS RELEASES BATCH RELEASES NUCLIDES RELEASED UNITS QUARTER 3 QUARTER 4 QUARTER 3 QUARTER 4 ALL NUCLIDES Cobalt-58 CURIES 0.00E+00 0.00E+00 1.70E-05 4.89E-06 Cobalt-60 CURIES 0.00E+00 0.00E+00 6.78E-05 6.14E-05 Iron-55 CURIES 0.00E+00 0.00E+00 1.02E-04 1.97E-04 Tritium CURIES 8.65E-03 1.90E-02 5.40E+01 4.47E+01 Mercury-203 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Iodine-131 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Krypton-85 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Krypton-85m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Manganese-54 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Molybdenum-99 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Nickel-63 CURIES 0.00E+00 0.00E+00 9.22E-04 3.04E-03 Ruthenium-106 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Antimony-124 CURIES 0.00E+00 0.00E+00 1.83E-04 6.46E-05 Antimony-125 CURIES 0.00E+00 0.00E+00 9.41E-04 6.88E-04 Tin-117m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Technetium-99m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Tellurium-125m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-131m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-133 CURIES 0.00E+00 0.00E+00 4.78E-05 0.00E+00 Xenon-133m CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 Xenon-135 CURIES 0.00E+00 0.00E+00 0.00E+00 0.00E+00 TOTAL FOR PERIOD CURIES 8.65E-03 1.90E-02 5.40E+01 4.47E+01

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Liquid Effluents 5-10 STP NUCLEAR OPERATING COMPANY Unit 1 plus 2 Total REPORT CATEGORY:

ANNUAL LIQUID RELEASES. TOTALS FOR EACH NUCLIDE RELEASED. FOR ALL OF 2024 NUCLIDES RELEASED UNITS UNIT 1 2024 UNIT 2 2024 TOTAL 2024 ALL NUCLIDES Cobalt-58 CURIES 1.95E-04 4.54E-05 2.41E-04 Cobalt-60 CURIES 9.15E-04 4.47E-04 1.36E-03 Iron-55 CURIES 1.33E-03 9.33E-04 2.26E-03 Tritium CURIES 1.39E+03 8.77E+02 2.27E+03 Mercury-203 CURIES 1.50E-07 0.00E+00 1.50E-07 Iodine-131 CURIES 0.00E+00 1.63E-03 1.63E-03 Krypton-85 CURIES 0.00E+00 1.14E-03 1.14E-03 Krypton-85m CURIES 0.00E+00 2.27E-06 2.27E-06 Manganese-54 CURIES 1.41E-05 0.00E+00 1.41E-05 Molybdenum-99 CURIES 1.16E-07 0.00E+00 1.16E-07 Nickel-63 CURIES 9.53E-03 4.03E-03 1.36E-02 Ruthenium-106 CURIES 0.00E+00 2.26E-06 2.26E-06 Antimony-124 CURIES 8.39E-05 5.59E-04 6.43E-04 Antimony-125 CURIES 6.78E-04 3.21E-03 3.88E-03 Tin-117m CURIES 0.00E+00 1.63E-07 1.63E-07 Technetium-99m CURIES 1.13E-07 0.00E+00 1.13E-07 Tellurium-125m CURIES 5.34E-05 1.30E-04 1.83E-04 Xenon-131m CURIES 0.00E+00 1.53E-02 1.53E-02 Xenon-133 CURIES 3.79E-03 7.56E-01 7.60E-01 Xenon-133m CURIES 3.01E-07 2.78E-03 2.78E-03 Xenon-135 CURIES 1.12E-04 2.25E-04 3.38E-04 TOTAL FOR PERIOD CURIES 1.39E+03 8.78E+02 2.27E+03 TOTAL Noble Gases CURIES 3.90E-03 7.75E-01 7.80E-01 TOTAL Excluding Tritium & Noble Gases CURIES 1.28E-02 1.10E-02 2.38E-02 TOTAL Gamma Emitters Excluding Noble Gases millicuries 1.94E+00 6.02E+00 7.95E+00

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Solid Waste and Irradiated Fuel Shipments 6-1 Solid Waste and Irradiated Fuel Shipments

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Solid Waste and Irradiated Fuel Shipments 6-2 A. SOLID WASTE SHIPPED OFFSITE FOR BURIAL OR DISPOSAL (not irradiated fuel)

1. Type of Waste Units 12-Month Period Shipped Estimated Error,

(+/-)%

a. Spent resins, filters, evaporator bottoms, etc.

m3 2.8E+01 2.00E+01 Ci 2.3E+02

b. Dry compressible waste, contaminated equip., etc.

m3 5.7E+02 2.00E+01 Ci 2.7E-01

c. Irradiated components, control rods, etc.

m3 None N/A Ci None

d. Other (Large Reactor Components and Associated Commodities) m3 7.7E+00 2.00E+01 Ci 1.2E-03
e. Low Level Exempt Quantities of sewage sludge and resin.

m3 6.1E+01 N/A Ci 4.9E-05

2. Estimate of major nuclide composition (by type of waste)
a. Spent resins, filter sludges, evaporator bottoms, etc.

Shipped Curie (Ci)

H-3 3.13E+00 1.34%

Mn-54 8.05E+00 3.45%

Fe-55 1.76E+01 7.52%

Co-58 5.65E+00 2.42%

Co-60 7.96E+01 34.09%

Ni-63 1.11E+02 47.37%

Cs-137 2.56E+00 1.09%

b. Dry compressible waste, contaminated equip., etc.

Shipped Curie (Ci)

Cr-51 4.20E-02 15.33%

Mn-54 4.65E-03 1.70%

Fe-55 4.99E-02 18.21%

Co-58 2.67E-02 9.74%

Co-60 9.52E-02 34.71%

Ni-63 1.13E-02 4.11%

Zr-95 1.37E-02 4.99%

Nb-95 2.48E-02 9.04%

c. Irradiated components, control rods, etc.

Shipped Curie (Ci)

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Solid Waste and Irradiated Fuel Shipments 6-3 None 0.00E+00 0.00%

d. Other (Large Reactor Components and Associated Commodities)

Shipped Curie (Ci)

Mn-54 1.27E-05 1.06%

Fe-55 3.44E-04 28.78%

Co-60 7.40E-04 61.89%

Ni-63 7.22E-05 6.03%

Ag-110m 1.74E-05 1.46%

e. Low Level Exempt Quantities of sewage sludge and resin.

Shipped Curie (Ci)

H-3 4.68E-05 96.08%

Be-7 1.70E-06 3.50%

Co-60 2.07E-07 0.43%

3. Solid Waste Disposition Number of Shipments Mode of Transportation Type of Waste Destination 9

Truck

a. Spent resins, filter sludges, evaporator bottoms, etc.
b. Dry compressible waste, contaminated equip., etc.
d. Other (Large Reactor Components and Associated Commodities)

Waste Control Specialists -

Compact Waste Disposal Facility 9998 W. State Highway 176 Andrews, Texas 79714 10 Truck

a. Spent resins, filter sludges, evaporator bottoms, etc.
b. Dry compressible waste, contaminated equip., etc.
d. Other (Large Reactor Components and Associated Commodities)

Waste Control Specialists - TSDF Storage and Processing Facility 9998 W. State Highway 176 Andrews, Texas 79714 Note: *Shipped per Texas Commission on Environmental Quality exemption to industrial landfill

4. Class of Solid Waste:

A, B, C

5. Type of Containers Used for Shipment:

General Design, Type A Containers, Type B Containers

6. Solidifying Agent: N/A B. Irradiated Fuel Shipments (Disposal): No shipments made during this period

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Dose Data Tab Dose Data Tab

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Dose Data Tab Intentionally Left Blank

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Dose Accumulations 7-1 Dose Accumulations

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Dose Accumulations 7-2 STP NUCLEAR OPERATING COMPANY

SUMMARY

OF MAXIMUM INDIVIDUAL DOSES Unit: 1 TOTAL ACCUMULATION FOR PERIODS:

for LIQUID, GASEOUS, AND AIR Starting: 1-Jan-2024 Ending: 31-Dec-2024 EFFLUENT APPLICABLE ORGAN ESTIMATED DOSE (mrem)

AGE GROUP LOCATION DIST DIR (m) (TOWARD)

% OF APPLICABLE LIMIT LIMIT (mrad or mrem)

LIQUID TOTAL BODY 8.05E-03 ADULT LITTLE ROBBINS SLOUGH 2.68E-01 3

LIQUID LIVER 8.13E-03 ADULT LITTLE ROBBINS SLOUGH 8.13E-02 10 NOBLE GAS AIR DOSE (gamma-mrad) 1.08E-03 2160m W 1.08E-02 10 NOBLE GAS AIR DOSE (beta-mrad) 3.98E-04 2160m W 1.99E-03 20 NOBLE GAS TOTAL BODY 7.19E-04 ALL 2160m W 1.44E-02 5

NOBLE GAS TOTAL BODY 2.69E-04 ALL 4000m WSW 5.38E-03 5

NOBLE GAS SKIN 1.16E-03 ALL 2160m W 7.71E-03 15 NOBLE GAS SKIN 4.33E-04 ALL 4000m WSW 2.88E-03 15

IODINE, PARTICULATES,

& TRITIUM BONE 1.78E-01 CHILD 1850m WNW 1.19E+00 15

IODINE, PARTICULATES,

& TRITIUM BONE 4.78E-02 CHILD 4000m WSW 3.19E-01 15

SUMMARY

OF POPULATION DOSES FOR 2024 EFFLUENT APPLICABLE ORGAN ESTIMATED POPULATION DOSE (person-rem)

AVERAGE DOSE TO POPULATION (rem per person)

LIQUID TOTAL BODY 5.30E-04 1.21E-07 GASEOUS TOTAL BODY 3.38E-02 3.11E-09 NOTES:

(1)

Doses were calculated for HYPOTHETICAL receptors at the site boundary.

(2)

Highest dose for nearest individual or receptor. This individual is assumed to reside at this location.

(3) Calculation based on a population of 303,500 for shore line exposure and for salt water invertebrate ingestion and 3,800 for salt water sport fish ingestion.

(4) Calculation based on a population of 299,000 within fifty (50) miles of South Texas Project.

(5)

Receptor at this location is an adult ingesting fresh water sport fish and receiving shoreline exposure from the Little Robbins Slough Area.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Dose Accumulations 7-3 STP NUCLEAR OPERATING COMPANY

SUMMARY

OF MAXIMUM INDIVIDUAL DOSES Unit: 2 TOTAL ACCUMULATION FOR PERIODS:

for LIQUID, GASEOUS, AND AIR Starting: 1-Jan-2024 Ending: 31-Dec-2024 EFFLUENT APPLICABLE ORGAN ESTIMATED DOSE (mrem)

AGE GROUP LOCATION DIST DIR (m) (TOWARD)

% OF APPLICABL E LIMIT LIMIT (mrad or mrem)

LIQUID TOTAL BODY 5.06E-03 ADULT LITTLE ROBBINS SLOUGH 1.69E-01 3

LIQUID LIVER 5.09E-03 ADULT LITTLE ROBBINS SLOUGH 5.09E-02 10 NOBLE GAS AIR DOSE (gamma-mrad) 4.10E-02 1850m WNW 4.10E-01 10 NOBLE GAS AIR DOSE (beta-mrad) 4.06E-02 1850m WNW 2.03E-01 20 NOBLE GAS TOTAL BODY 2.64E-02 ALL 1850m WNW 5.29E-01 5

NOBLE GAS TOTAL BODY 3.47E-03 ALL 7200m WNW 6.95E-02 5

NOBLE GAS SKIN 4.95E-02 ALL 1850m WNW 3.30E-01 15 NOBLE GAS SKIN 6.54E-03 ALL 7200m WNW 4.36E-02 15

IODINE, PARTICULATES,

& TRITIUM BONE 1.85E-01 CHILD 1850m WNW 1.23E+00 15

IODINE, PARTICULATES,

& TRITIUM BONE 4.95E-02 CHILD 4000m WSW 3.30E-01 15

SUMMARY

OF POPULATION DOSES FOR 2024 EFFLUENT APPLICABLE ORGAN ESTIMATED POPULATION DOSE (person-rem)

AVERAGE DOSE TO POPULATION (rem per person)

LIQUID TOTAL BODY 3.31E-04 7.61E-08 GASEOUS TOTAL BODY 4.77E-02 5.27E-09 NOTES:

(1)

Doses were calculated for HYPOTHETICAL receptors at the site boundary.

(2)

Highest dose for nearest individual or receptor. This individual is assumed to reside at this location.

(3) Calculation based on a population of 303,500 for shore line exposure and for salt water invertebrate ingestion and 3,800 for salt water sport fish ingestion.

(4) Calculation based on a population of 299,000 within fifty (50) miles of South Texas Project.

(5)

Receptor at this location is an adult ingesting fresh water sport fish and receiving shoreline exposure from the Little Robbins Slough Area.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Dose Accumulations 7-4 STP NUCLEAR OPERATING COMPANY

SUMMARY

OF MAXIMUM INDIVIDUAL DOSES Unit: 1 plus 2 TOTAL ACCUMULATION FOR PERIODS:

for LIQUID, GASEOUS, AND AIR Starting: 1-Jan-2024 Ending: 31-Dec-2024

SUMMARY

OF POPULATION DOSES FOR 2024 EFFLUENT APPLICABLE ORGAN ESTIMATED POPULATION DOSE (person-rem)

AVERAGE DOSE TO POPULATION (rem per person)

LIQUID TOTAL BODY 8.61E-04 1.97E-07 GASEOUS TOTAL BODY 8.16E-02 7.20E-09 NOTES:

(1)

Doses were calculated for HYPOTHETICAL receptors at the site boundary.

(2)

Highest dose for nearest individual or receptor. This individual is assumed to reside at this location.

(3) Calculation based on a population of 303,500 for shore line exposure and for salt water invertebrate ingestion and 3,800 for salt water sport fish ingestion.

(4) Calculation based on a population of 299,000 within fifty (50) miles of South Texas Project.

(5)

Receptor at this location is an adult ingesting fresh water sport fish and receiving shoreline exposure from the Little Robbins Slough Area.

EFFLUENT APPLICABLE ORGAN UNIT 1 ESTIMATED DOSE (mrem)

UNIT 2 ESTIMATED DOSE (mrem)

TOTAL 1+2 ESTIMATED DOSE (mrem)

AGE GROUP LOCATION DIST DIR (m) (TOWARD)

LIQUID TOTAL BODY 8.05E-03 5.06E-03 1.31E-02 ADULT LITTLE ROBBINS SLOUGH LIQUID LIVER 8.13E-03 5.09E-03 1.32E-02 ADULT LITTLE ROBBINS SLOUGH NOBLE GAS AIR DOSE (gamma-mrad) 1.01E-03 4.10E-02 4.20E-02 1850m WNW NOBLE GAS AIR DOSE (beta-mrad) 3.78E-04 4.06E-02 4.10E-02 1850m WNW NOBLE GAS TOTAL BODY 6.74E-04 2.64E-02 2.71E-02 ALL 1850m WNW NOBLE GAS TOTAL BODY 8.84E-05 3.47E-03 3.56E-03 ALL 7200m WNW NOBLE GAS SKIN 1.09E-03 4.95E-02 5.05E-02 ALL 1850m WNW NOBLE GAS SKIN 1.42E-04 6.54E-03 6.68E-03 ALL 7200m WNW

IODINE, PARTICULATES, &

TRITIUM BONE 1.78E-01 1.85E-01 3.63E-01 CHILD 1850m WNW

IODINE, PARTICULATES, &

TRITIUM BONE 4.78E-02 4.95E-02 9.73E-02 CHILD 4000m WSW

IODINE, PARTICULATES, &

TRITIUM TOTAL BODY 3.96E-03 4.22E-03 8.18E-03 ADULT 4000m WSW

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Results of Direct Radiation Measurements 8-1 RESULTS OF DIRECT RADIATION MEASUREMENTS PROGRAM

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Results of Direct Radiation Measurements 8-2 STP NUCLEAR OPERATING COMPANY Onsite Direct Radiation Measurements REPORT CATEGORY: THERMOLUMINESCENT DOSIMETER MONITORING STATIONS QUARTERLY RESULTS FOR 2024 TABLE 8-1 MONITORING STATION NUMBER (Noted on Figure 8-1)

QUARTER 1 QUARTER 2 QUARTER 3 QUARTER 4 AVERAGE RATE AVERAGE NET RATE UNITS milliRoentgen milliRoentgen milliRoentgen milliRoentgen milliRoentgen per quarter milliRoentgen per hour PROTECTED AREA 1

10 10 10 20 13 0.0057 2

13 12 12 19 14 0.0064 3

13 11 12 11 12 0.0054 4

13 12 12 15 13 0.0060 5

13 12 11 15 13 0.0058 6

14 12 17 19 16 0.0071 7

16 15 16 17 16 0.0073 8

14 13 14 20 15 0.0070 9

13 12 12 13 13 0.0057 10 19 18 18 19 19 0.0085 11 25 23 23 36 27 0.0122 12 11 10 12 7

10 0.0046 13 12 11 10 12 11 0.0052 14 12 11 11 11 11 0.0052 15 12 11 11 12 12 0.0053 16 14 13 14 18 15 0.0068

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Results of Direct Radiation Measurements 8-3 OLD STEAM GENERATOR STORAGE FACILITY 25 13 12 12 12 12 0.0056 26 17 14 14 18 16 0.0072 27 14 12 13 13 13 0.0060 28 15 12 13 14 14 0.0062 LOW LEVEL RAD WASTE STORAGE AREA 29 17 16 16 21 18 0.0080 30 19 16 15 19 17 0.0079 31 17 16 16 20 17 0.0079 32 17 16 16 20 17 0.0079 33 17 15 16 17 16 0.0074 34 18 15 17 19 17 0.0079 35 20 20 18 19 19 0.0088 36 15 15 15 17 16 0.0071 ISFSI AREA 37*

18 10 15 16 15 0.0068 38*

36 19 17 42 29 0.0130 39*

61 26 31 65 46 0.0209 40*

33 23 24 39 30 0.0136

  • The Independent Spent Fuel Storage Installation Area started storing radioactive material in 2019.

Environmental Thermoluminescent dosimeters (TLDs) were first installed January 2015. TLD (#37 through #40) used both environmental and (Panasonic UD 814s) and personnel TLDs (Mirion type 36 badge) starting the third quarter in 2015 to measure gamma and neutron background exposure to the end of 2022. STP used Panasonic UD 802 for 2023 TLDs and the Harshaw badge with a ISFSI neutron correction factor. STP used the Panasonic UD 814 for 2024 2nd and 3rd quarter from Mirion Dosimetry with the BeOSL for the 4th quarter.

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Results of Direct Radiation Measurements 8-4 Notes for Onsite Direct Radiation Measurements Measurement Results Individual values normalized to a 91 day quarter.

Only the calcium sulfate elements were used in these averages for the environmental TLDs.

Average Net Rate:

Difference between the 2024 exposure rate and the 1986 measured rate due to natural background Average Net Rate= Average rate / 91 days / 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per day The pre-operational background rate of 15.4 mR at the site boundary in 1986 has been used to reflect the background baseline exposure rate for STP. Historically the exposure rates measured near the protected area fence have been lower than the historical background at the site boundary. However, a few dosimeter stations have at times exceeded this background rate due to radioactive waste shipping activities.

Zero:

Zero (0 or 0.00) indicate background levels Milliroentgen:

Milliroentgen or mR is a unit of exposure for X-rays and gamma rays.

Figure 8-1 8-5

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Meteorological Data Tab Meteorological Data Tab

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Meteorological Data Tab Intentionally Left Blank

RADIOACTIVE EFFLUENT RELEASE REPORT 2024 SOUTH TEXAS PROJECT Joint Frequency Tables Joint Frequency Tables 9-1

First Quarter 2024 9-2

First Quarter 2024 9-3

First Quarter 2024 9-4

First Quarter 2024 9-5

First Quarter 2024 9-6

First Quarter 2024 9-7

First Quarter 2024 9-8

First Quarter 2024 9-9

First Quarter 2024 9-10

Second Quarter 2024 9-11

Second Quarter 2024 9-12

Second Quarter 2024 9-13

Second Quarter 2024 9-14

Second Quarter 2024 9-15

Second Quarter 2024 9-16

Second Quarter 2024 9-17

Second Quarter 2024 9-18

Second Quarter 2024 9-19

Third Quarter 2024 9-20

Third Quarter 2024 9-21

Third Quarter 2024 9-22

Third Quarter 2024 9-23

Third Quarter 2024 9-24

Third Quarter 2024 9-25

Third Quarter 2024 9-26

Third Quarter 2024 9-27

Third Quarter 2024 9-28

Fourth Quarter 2024 9-29

Fourth Quarter 2024 9-30

Fourth Quarter 2024 9-31

Fourth Quarter 2024 9-32

Fourth Quarter 2024 9-33

Fourth Quarter 2024 9-34

Fourth Quarter 2024 9-35

Fourth Quarter 2024 9-36

Fourth Quarter 2024 9-37

First Quarter 2024 Batch 9-38

First Quarter 2024 Batch 9-39

First Quarter 2024 Batch 9-40

First Quarter 2024 Batch 9-41

First Quarter 2024 Batch 9-42

First Quarter 2024 Batch 9-43

First Quarter 2024 Batch 9-44

First Quarter 2024 Batch 9-45

First Quarter 2024 Batch 9-46

First Quarter 2024 Batch 9-47

Second Quarter 2024 Batch 9-48

Second Quarter 2024 Batch 9-49

Second Quarter 2024 Batch 9-50

Second Quarter 2024 Batch 9-51

Second Quarter 2024 Batch 9-52

Second Quarter 2024 Batch 9-53

Second Quarter 2024 Batch 9-54

Second Quarter 2024 Batch 9-55

Second Quarter 2024 Batch 9-56

Second Quarter 2024 Batch 9-57

Second Quarter 2024 Batch 9-58

Third Quarter 2024 Batch 9-59

Third Quarter 2024 Batch 9-60

Third Quarter 2024 Batch 9-61

Third Quarter 2024 Batch 9-62

Third Quarter 2024 Batch 9-63

Third Quarter 2024 Batch 9-64

Third Quarter 2024 Batch 9-65

Third Quarter 2024 Batch 9-66

Third Quarter 2024 Batch 9-67

Third Quarter 2024 Batch 9-68

Fourth Quarter 2024 Batch 9-69

Fourth Quarter 2024 Batch 9-70

Fourth Quarter 2024 Batch 9-71

Fourth Quarter 2024 Batch 9-72

Fourth Quarter 2024 Batch 9-73

Fourth Quarter 2024 Batch 9-74

Fourth Quarter 2024 Batch 9-75

Fourth Quarter 2024 Batch 9-76

Fourth Quarter 2024 Batch 9-77

Fourth Quarter 2024 Batch 9-78

STI #35658027 O P G P 0 3 -Z X- 0 0 07

Retrieved from "https://kanterella.com/w/index.php?title=ML25111A131&oldid=5470326"