ML24116A228

Annual Environmental Operating Report

ML24116A228
Person / Time
Site:	South Texas
Issue date:	04/25/2024
From:	Morgan J South Texas
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NOC-AE-24004032, 35584603
Download: ML24116A228 (1)

Text

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Nuclear Operattng Company

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ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 South Texas Project Units 1 and 2 Docket Nos. 50-498; 50-499 April 25, 2024 NOC-AE-24004032 10 CFR 50.36 STI: 35584603 South Texas Project Electric Generating Station 2023 Annual Environmental Operating Report Pursuant to the South Texas Project Environmental Protection Plan (Non-radiological) and Technical Specification 6.9.1.3, the STP Nuclear Operating Company provides the attached South Texas Project Electric Generating Station 2023 Annual Environmental Operating Report.

There are no commitments in this letter.

If there are any questions about this report, please contact Zachary Dibbern at (361) 972-4336 or me at (361) 972-4045.

e /14.-)c/---

ah B. Morgan ager, Health Physics

Attachment:

South Texas Project Electric Generating Station 2023 Annual Environmental Operating Report cc:

Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 E. Lamar Boulevard Arlington, TX 76011-4511

CHAPTER 0NE l EXECUTIVE

SUMMARY

1-2 2023 ANNUAL 2023 ANNUAL ENVIRONMENTAL ENVIRONMENTAL OPERATING REPORT OPERATING REPORT

TABLE OF CONTENTS Figure 2-1: Plant Water Systems..... 2-4 Figure 4-1: 2023 Non-radioactive Waste Management........... 4-9 Figure 4-2: 2023 Non-radioactive Waste Generation............ 4-9 Figure 4-3: Hazardous Waste Shipped Historical Comparison..... 4-9 Figure 6-1: Radiological Environmental Monitoring Program Designated Sample Location Map............... 6-3 Figure 6-2: Radiological Environmental Monitoring Program Onsite Sample Location Map............... 6-4 Figure 6-3: Radiological Environmental Monitoring Program Zone Location Map............... 6-5 Figure 6-4: Historical Comparison of Average Quarterly Beta Activity from Indicator and Control Air Samples.... 6-6 Figure 6-5: Environmental Dosimeter Comparisons......... 6-7 Figure 6-6: Historical Comparison of Cobalt-60 in Main Cooling Reservoir Sediment............ 6-7 FIGURES Table 1: Radiological Environmental Monitoring Program....... 6-19 to 6-21 Table 2: Sample Media and Location Descriptions...... 6-22 to 6-30 Table 3: 2023 Radiological Environmental Monitoring Program Analysis Summary........ 6-34 to 6-40 TABLES ANSI/HPS N13.37 STP Environmental Dosimetry Results............ 6-33 CHART CHAPTER ONE EXECUTIVE

SUMMARY

.............. 1-1 CHAPTER TWO SITE AND AREA DESCRIPTION............ 2-1 CHAPTER THREE NON-RADIOLOGICAL ENVIRONMENTAL INTRODUCTION AND

SUMMARY

............... 3-1 CHAPTER FIVE RADIOLOGICAL ENVIRONMENTAL INTRODUCTION AND

SUMMARY

............... 5-1 CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT................ 6-1 Program Description........... 6-2 Airborne Pathway............. 6-6 Direct Exposure Pathway......... 6-6 Sediment Samples............ 6-8 Waterborne Pathway.......... 6-10 NEI Groundwater Protection Initiative.6-15 Land Use Census............. 6-16 Quality Assurance............ 6-16 Program Deviations........... 6-18 Radiological Environmental Monitoring Program Analysis Summary....... 6-32 CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL INTRODUCTION AND

SUMMARY

.............. 4-1 Environmental Conditions........ 4-2 Aquatic and Ecological Monitoring... 4-2 Water Quality Management....... 4-3 Air Quality Management......... 4-7 Non-radioactive Waste Management.. 4-7 Chemical Control and Management.. 4-8 Environmental Protection Plan Status. 4-10 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Figure 6-7: Calculated Cumulative Curies of Cobalt-60 in the Main Cooling Reservoir................. 6-7 Figure 6-8: Historical Comparison of Tritium Added to and Remaining in the Main Cooling Reservoir....... 6-9 Figure 6-9: Historical Comparison of Tritium Activity in Reservoir Relief Wells................ 6-9 Figure 6-10: Historical Comparison of Tritium Activity in Surface Water.... 6-11 Figure 6-11: Historical Comparison of Tritium Activity in Shallow Aquifer Ground Water.............. 6-11 Figure 6-12: Tritium Activity in Shallow Ground Water West of the Main Cooling Reservoir................. 6-14 Figure 6-13: STP Protected Area Ground Water Monitoring Results........ 6-15 Figure 6-14: STP Protected Area Ground Water Monitoring Wells.... 6-15 Figure 6-15: 2023 Radiological Laboratory Quality Assurance Program Performance............... 6-17 Figure 6-16: Duplicate & Split Agreement of Environmental Samples in 2023... 6-17

INTRO OVERVIEW Photo courtesy of Gary Parkey Authored by:

Laura Stoicescu, CHP Consulting Health Physicist, Health Physics Division Technical Review:

Edmond Hardcastle Jr.

Staff Environmental Radiological Services Specialist Health Physics Division Authored by:

Kenneth M. Cunningham Environmental Supervisor, Regulatory Affairs Approved by:

Jonah Morgan Manager, Health Physics Division Completed in accordance with Technical Specifications for United States Nuclear Regulatory Commission Renewed License No. NPF-76 and No. NPF-80 l April 2024 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT The 2023 Annual Environmental Operating Report for the South Texas Project Electric Generating Station combines in one report the requirements for the Annual Environmental Operating Report (Non-radiological) found in Appendix B to the renewed Facility Operating License No. NPF-76 and No. NPF-80 and the requirements for the Annual Radiological Environmental Operating Report found in Part A of the stations Offsite Dose Calculation Manual.

Photo courtesy of Greg McMullin STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

For over thirty years, STP has produced safe, carbon-free, clean-air energy at our site in beautiful Matagorda County with great respect and admiration for the land, water and air we all share.

Matagorda County prides itself on the beauty and variety of the ecosystems and wildlife that thrive here. It harbors a unique convergence of those ecosystems, including secluded, extensive forests, waterways, riparian wetlands, an expansive prairie and 40 miles of beautiful, wild coastline. Its uniqueness as prime habitat for wildlife is evidenced by it being consistently named as the county with the greatest variety of migratory birds than in any other county in the United States. STP is committed to caring for the natural resources with which we have been entrusted. We want Matagorda County residents to know that STPs dedication to protecting the environment will not diminish, and it is our great privilege to operate on this land that we all call home. Transparency in our environmental operations is a key element to maintaining our trust and good relationship with our community. This report exemplifies our dedication to maintaining this open communication.

Thank you for allowing us to continue to be your trusted neighbor.

We look forward to serving this community and being a steward of our environment for many years to come.

Tim Powell President and CEO STP Nuclear Operating Company MESSAGE FROM THE PRESIDENT AND CEO MESSAGE FROM THE PRESIDENT AND CEO

EXECUTIVE

SUMMARY

1-1 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER 0NE EXECUTIVE

SUMMARY

1-2 This report describes the environmental monitoring programs, non-radiologicaland radiological, conducted atthe South Texas Project during2023. Included in this report arethe Environmental Protection Plan Status, the results of the Radiological Environmental Monitoring Program, and the Land Use Census.

Non-radiological environmentalmonitoring is performed eachyear as part of the stations overallEnvironmental Protection Plan whichis intended to provide for protection of non-radiological environmentalparam eters during station operations.

Non-radiological monitoringencompasses, as a minimum, waterquality, air quality, waste generationand minimization, and local aquaticand terrestrial ecological conditions. In2023, non-radiological monitoring bythe station confirmed that the SouthTexas Projects efforts to respect andprotect local environmental conditions were successful. The operation of South Texas Project continued to provide high-quality habitat areas for a varietyof flora and fauna and continued tohave no indications of negative nonradiologicalim pacts to local environmental conditions.

The environment within a 15-mileradius of the South Texas Project isroutinely monitored for radiation andradioactivity.

Sampling locations areselected using weather, land use, andwater use infor mation. Two types ofsampling locations are used. The firsttype, Control Stations, are located inareas that are beyond the measurableinfluence of the South Texas Projector any other nuclear facility. The sampleresults from these stations are used toexplain radiation from sources otherthan the South Texas Project.

IndicatorStations are the second type of station.The samples from these stations measure any radiation contributed tothe environment that could be caused by the South Texas Project. Indicator Stations are located in areas close tothe South Texas Project where anyplant releases would be detected.

Prior to initial operation of the South Texas Project, samples were collectedand analyzed to determine the amountof radioactivity present in the area.These results are used as a preoperationalbase line. Results fromthe Indicator Stations are comparedto both current control sample resultsand the pre-operational baselinevalues to determine if changes inradioactivity levels are attributable tostation operations or other causes suchas previous nuclear weapons testing programs and natural variations.

CHAPTER ONE Photo courtesy of Robert Bowers The South Texas Project Electric Generating Station (South TexasProject) continues to operate with noadverse effect on the population orthe environment. The dose equivalentfor people living in the area remainsat less than one millirem per year.

Environmental programs at thesite monitor known and predictablerela tionships between the operationof the South Texas Project and thesurrounding area. These monitoringprograms verify that the operation ofthe South Texas Project has no impactoffsite and is well below state andfederal regula tions and guidelines.These programs are verified by theState of Texas through collection andanalysis of samples and placement ofthe States monitoring dosimeters andother onsite and offsite inspections.

Photo courtesy of Greg McMullin Photo courtesy of Christie Dement Continued on p.1-3

1-3 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Radioactivity levels in the South Texas Projects environment frequentlyfall below the minimum detectioncapabilities of state-of-the-art scientificinstruments.

Samples with radiationlevels that cannot be detected arebelow the Lower Limits of Detection.The United States Nuclear RegulatoryCommission requires that equipmentused for radiological moni toring mustbe able to detect specified minimumlimits for certain types of samples. Thisensures that radiation measurementsare sufficiently sensitive to detectsmall changes in the environment.

The United States Nuclear Regulatory Commission also has a requiredreporting level. Licensed nuclearfacilities must prepare a special reportand increase their sampling if anymeasured radiation level is equal toor greater than this reporting level.

No sample from the South TexasProject has ever reached or exceededthis report ing level. Measurementsperformed are divided into fourcategories, or pathways, based uponhow the results may affect the public.Airborne, waterborne, ingestion, anddirect radiation are the four pathways that are sampled. Each pathway isdescribed on page 1-4.

The South Texas Project continuesto operate with no adverse effect onthe population or the environment.The dose equivalent for people livingin the area is maintained at less thanone millirem per year. Environmentalprograms at the site monitor knownand predictable relation ships betweenthe operation of the South TexasProject and the surrounding area.

These monitoring programs verifythat the operation of the South TexasProject has no impact offsite and is wellwithin state and federal regulations andguidelines.

These programs are verifiedby United States Nuclear RegulatoryCommission inspections and theState of Texas through collection andanalysis of samples and state radiationmonitoring dosimeters.

Photo courtesy of Greg McMullin Measurementsperformed are divided into four pathways, airborne, waterborne, ingestion, anddirect radiation Photo courtesy of Christie Dement

CHAPTER 0NE EXECUTIVE

SUMMARY

1-4

• The airborne pathway is sampledin areas around the South TexasProject by measuring the levelsof radioactive iodine and particulate radioactivityon air filters. The 2023 airborne results were similarto pre-operational levels detecting only naturallyoccurring radioactive material unrelated to theoperation of the South Texas Project.

• The waterborne pathway includes samples takenfrom surface water, groundwater, and drinkingwater. Also included in this pathway are sedimentsamples taken from the Main Cooling Reservoir andthe Colorado River.

Tritium was the only man-madenuclide consistently detected in water samplesand was measured in the shallow aquifer, the MainCooling Reservoir, ditches, and sloughs consistentwith the South Texas Project Main Cooling Reservoiroperating design. The levels of Triti um found werenear or lower than the concentration of Tritium in theMain Cooling Reservoir. Additional onsite wells havebeen sampled to map Tritium migration.

The averageTritium level in the Main Cooling Reservoir remainedstable throughout 2023. Tritium levels remain wellbelow United States Nuclear Regulatory Commis sionreporting limits and within United States Environ mentalProtection Agency drinking water standards.

Previously detected plant-related nuclides, such as cobalt-60 and cesium-137, were detected in the reser voirsediment at designated sample locations at very lowconcentrations. Additional samples had detect ablecesium-137 which is normally present in the environ mentand is consistent with pre-operational concentra tions.Onsite sediment samples continue to occasionally indicatetraces of plant-related nuclides such as cobalt-60.

Offsitesediment samples continue to show no radioactiv ity fromthe South Texas Project. In summary, the station producedno detectable waterborne effects offsite.

• The ingestion pathway includes broadleaf vegetation, agricultural products, and food products. Naturally occurring nuclides were detected at averageenvironmental levels in the samples. The data indicatedthere were no man-made nuclides detected in these typesof samples.

• The direct exposure pathway measures environmental radiation doses using thermoluminescent dosimeters.

These results are consistent with the readings fromprevious years and pre-operational measurementsindicating no effect from South Texas Project operations.

Each of the four pathways Photo courtesy of Kelly Callais

SITE AND AREA DESCRIPTION 2-1 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER TWO SITE AND AREA DESCRIPTION 2-2 The South Texas Project has twoWestinghouse pressurized waterreactors. The rated core thermal powerof each unit is 3,853 megawatts thermal(MWt). Each unit was originallydesigned for a net electrical poweroutput 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 licenseon December 16, 1988, achieved initialcriti cality on March 12, 1989, and wasdeclared commercially operational onJune 19, 1989. On September 28, 2017,the United States Nuclear RegulatoryCommission approved the SouthTexas Projects request to extend theoperating licenses an additional twentyyears through 2047 and 2048.

The combined units currently produce enough electricity to serve more thantwo million homes and businessesthroughout Texas. With approximately1,000 baseline employees, the STPNuclear Operating Company is thelargest employer and source of revenuefor Matagorda County.

Nuclear energycontinues to provide long-termcost stability and promote energyindependence. It is our nations largestsource of carbon-free energy.

As wework collectively to secure our stateslong-term energy future, nuclear energywill continue to play an important roleas a safe and reliable supply of clean baseload electricity.

Large photo courtesy of Kelly Callais. Inset photos 1 through 3 courtesy of Gary Parkey. Inset photo 4 courtesy of Greg McMullin.

The South Texas Project is located on 12,220 acres in Matagorda County,Texas, approximately 15 milessouthwest of Bay City along the westbank of the Colorado River. The SouthTexas Project is owned by Constellation Energy, City of Austin, and CityPublic Service Board of San Antonioas tenants in common. Constellation Energy purchased the NRG South Texas LP share of the STP Nuclear Operating Company on November 1, 2023. HoustonLighting &

Power Company was theoriginal project manager of the SouthTexas Project and was responsiblefor the engineering, design, licensing,construction, startup, and initialcommercial operation of the two-unitfacility. In 1997, the STP Nuclear Operating Company assumedoperational control of the SouthTexas Project and responsibilityfor implementation of associatedenvironmental programs.

Fossil-fueled and nuclear-poweredsteam generating plants operate on thesame principle. Fuel is used to produceheat to convert water into high-pressuresteam.

The steam is directed througha turbine to turn a generator. In afossil fuel plant, either coal, lignite, oil, or natural gas is burned in a boiler toproduce the heat.

In a nuclear plant,the reactor replaces the boiler and thefissioning or splitting of uranium atomsinside the reactor produces the heat.

The fuel for a nuclear reactor isuranium. It is formed into cylindricalceramic pellets, each about the size ofthe end of your little finger. One pellethas the energy potential of about aton of coal. Millions of these pellets arestacked in fuel rods that are arrangedinto assemblies that make up the coreof the reactor. The use of uraniumallows us to conserve natural gas, oil,and coal and to avoid the associatedproduction of greenhouse gases.The fission process and generationof usable heat begins in a nuclearreactor when control rods in the coreare withdrawn. In pressurized waterreactors, like those at the South TexasProject, the fuel rods heat watercirculating in sealed, stainless-steelpiping that passes through large heatexchangers called steam generators.The water in the reactor is under pressureto prevent boiling. This is why the SouthTexas Projects Units 1 and 2 reactorsare called pressurized water reactors.

This hot, pressurized water heats aseparate supply of water in the steamgenerators to produce steam that isdirected through the blades of a turbinegenerator to produce electricity. Thesteam is then fed to a condenser wherea separate supply of cooling water fromthe Main Cooling Reservoir condensesit back into water that is then pumpedback to the steam generator for reuse.A diagram of the plant water systems isshown in Figure 2-1.

In addition to its safety systems, theSouth Texas Project has many built-inphysical barriers designed to preventthe release of radioactive materials inthe unlikely event of an accident. Themost visible ones are the 200-foot tall,domed containment buildings withsteel reinforced concrete walls fourfeet thick. Inside each of these massivestructures, two more concrete wallsprovide another 11 feet of radiationshielding. The reactor vessel itself hassteel walls six inches thick, and thefuel pellets inside it are sheathed inhardened metal tubes.

Nuclear energy has one of the lowestimpacts on the environment. It is themost eco-efficient energy sourcebecause it produces the most electricityin relation to its minimal environmentalimpact. 1Nuclear power plants generateapproximately 50 percent of thecarbon-free electricity generated in theUnited States. Additional informationon nuclear energy and the environmentcan be found on the websitemaintained by the Nuclear EnergyInstitute at www.nei.org.

1Nuclear Energy Institute. NuclearEnergy Fast Facts; October 2022. Asviewed at https://nei.org/resources/resources-archive?

type=fact_sheet.

How the South Texas Project Works Photo courtesy of Greg McMullin CHAPTER TWO

2-3 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Sixty-five of the total 12,220 acres atthe South Texas Project are occupiedby the two current power plants.Plant facilities include a 7,000-acremain cooling reservoir and a 47-acreessential cooling pond. Many smallerbodies of water onsite include wetlands,Kelly Lake, drainage ditches, sloughs,and depressions. Much of the landeast of the cooling reservoir is leasedfor cattle grazing. Approximately 1,700acres remain in a more natural state asa lowland habitat. A 110-acre wetlandhabitat area was established in 1996on previously unused land locatednortheast of the power plants. The areasurrounding the South Texas Projectis characterized by coastal plain withfarmland and pasture predominating.Local relief of the area is characterizedby flat land, approximately 23 feetabove sea level.

The plant site The area Matagorda Countys economy is basedprimarily on ranching, farming, oil andnatural gas production and refinement,petrochemical production, electricitygeneration, and commercial fishingand fisheries. The area within 10miles of the site is generally rural andcharacterized as farmland, which isprimarily pastureland used for livestockranching. Although the surroundingarea is heavily cultivated, significantamounts of woodlands, thicket, brush,fields, marsh, and open water existto support wildlife. The area lies inthe southern region of the centralflyway and is host to an abundanceof migratory birds. The local estuaryenvironments provide the necessaryhabitat for a variety of fish types tocomplete their life cycles.

The area alsoaffords opportunity for recreationalhunting and fishing.

The South Texas Project is home tomany species of animals. Inhabitantsinclude American alligators, a varietyof birds, and several hundred deer. Inwinter, literally hundreds of thousandsof waterfowl, principally migratorygeese as well as white pelicans, havefound that the plants 7,000-acrecooling reservoir provides a goodresting place during their migrations.The climate of the region is subtropicalmaritime, with continental influence. Itis characterized by short, mild wintersand long, hot, and humid summers.Rainfall normally ranges from abouttwo inches per month in Februarypeaking to about four to five inches permonth in May, June, September, andOctober. The prevailing wind directionis from the south-southeast, shiftingto north-northeast for short intervalsduring the winter months.

CHAPTER TWO SITE AND AREA DESCRIPTION 2-4 PLANT WATER SYSTEMS Figure. 2-1 Photo courtesy of Diep Tran

NON-RADIOLOGICAL ENVIRONMENTAL INTRODUCTION AND

SUMMARY

3-1 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER THREE NON-RADIOLOGICAL ENVIRONMENTAL INTRODUCTION AND

SUMMARY

3-2 The South Texas Project is committedto the production of electricity in a safe,reliable, and economical manner usingnuclear energy. The stations programs,policies, and business plan objectivesalso incor porate a commitmentto environmental protection andmanagement. The stations commitmentto sound environmental management in2023 is illustrated below.

Everyone at the South Texas Projecthas a responsibility to protectthe environment.

Commitment toenvironmental safety is an integralcomponent of the South Texas Projectoperating policy and core values. Thisresponsibility reaches further than merecompliance with laws and regulationsto encompass the integration ofsound environmental practices intoour daily operational and businessdecisions.

The people at the SouthTexas Project understand the need tobalance economic, operational, andenvironmental issues for the benefit ofthe station and the public.We recognize our responsibility to holdourselves to the highest principles ofenvironmental stewardship.

Photo courtesy of Gary Parkey Non-radiological environmentalconditions and performance atthe South Texas Project during2023 remained satisfactory and demonstrated that the South TexasProject continued to operate in anenvironmentally responsible mannerduring the year.

The South TexasProject achieved and maintainedhigh standards of envronmen talperformance and compliancethrough out 2023.

• The return to the HIGH performanceclassification2 for the first time since 2017 by the TexasCommission on Environmental Quality based on the stationsenvironmental compliancerecord in all areas considered,including water quality, wastemanagement, and air qualitycompliance.

• Continued support of communityactivities such as the annualMatagorda County HouseholdHazardous Waste Collection Day.

• The completion of a potable water inspection by the Texas Commission on Environmental Quality with no violations or findings identified.

2Per Compliance History Report for CN601658669, RN102395654, Rating Year 2023; as prepared by the Texas Commission on EnvironmentalQuality.

The stations commitment to sound environmental management in 2023 was highlighted by:

Photos courtesy of Christie Dement and Greg McMullin Photo courtesy of Pedro Garcia CHAPTER THREE

NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 4-1 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 4-2 ENVIRONMENTAL CONDITIONS The Texas Commission onEnvironmental Quality rated theSouth Texas Project as a highperformer in 2023 based on thesta tions environmental compliancerecord.

Facilities, such as the SouthTexas Project, can be classified by thestate as a high performer, satisfactoryperformer, or unsatisfactory performerbased on that facilitys compliancehistory. The states classification of theSouth Texas Project as a highperformer was based on the stationsenvironmental performance over thelast five-year period.

During the period of this report, thestation continued to promote greeninitiatives including the recycling ofpaper, plastics, and aluminum by siteemployees. The sta tion also continuedto support various bird counts andsurveys in 2023 sponsored by federaland state agencies and volunteer organizations such as the annual National Audubon Society Christmas Bird Count and the United States Fish and Wildlife Services Colonial Waterbird Survey.

AQUATIC AND ECOLOGICAL MONITORING The location of the South Texas Project falls within the Texas Land ResourceArea designation as coastal prairieand can be divided into two broadecological areas bottomland andupland areasbased on topography,soils, and vegetation. The bottomlandlowland habitat is a swampy, marshyarea that provides an important habitatfor birds and other wildlife and occupiesapproximately 1,700 acres of the sitenear the Colorado River. An upland spoilcontainment area, originally con structedin 1972 by the United States Army Corpsof Engineers, is included in this area. Inaddition, a 110-acre wetland habitat areathat attracts a variety of bird groupsand other wildlife was established in1996 on previously unused land located northeast of the power plants. Theremaining area of the site offers diversehabitats for mammals and severaltypes of birds. The South Texas Projectregularly monitors the sites environsfor changing conditions.

Ecologicalconditions onsite in 2023 remainedgenerally unchanged and stable.

The South Texas Project is locatedon the state-sponsored Great TexasCoastal Birding Trail that spansthe entire Texas Gulf Coast fromBrownsville to the Louisiana border.Matagorda County, in Photo courtesy of Kelly Callais This section of the report describes the South Texas Projects non-radiological environmental program performance and environmental conditions for2023.

The STP Nuclear OperatingCompany employees closely monitorenvironmental conditions at theSouth Texas Project.

Photos courtesy of David Adams and Kelly Callais Continued on p.4-3 Photo courtesy of Greg McMullin CHAPTER FOUR

4-3 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT which the SouthTexas Project is located, consistentlyranks at or near the top of the NationalAudubon Societys Annual ChristmasBird Count for the number of speciesidentified. Many bird species have beenobserved visiting the wetland habitatand elsewhere onsite. These includethe bald eagle, white-faced ibis, andbrown pelican. Additional migratory and resident bird species such as avariety of ducks, geese, turkey, andpelicans (both brown and white)have been observed during informalsurveys of the sites diverse naturaland man-made habitats.

Intensivebird nesting continues through out thelowland habitat, particularly in a heronrookery around the perimeter of KellyLake and on the internal dikes of theMain Cooling Reservoir at the SouthTexas Project. The South Texas Projectcontinues to provide vital habitat formore than an estimated 125 species ofwintering and resident birds.

The South Texas Project continues tomonitor important wildlife species todetect pop-ulation changes. Informalobservations continue to indicate thatthe site provides high-quality habitatin which a wide range of animals thrive.The site continues to attract extensivewildlife populations, offering a refugefor resident species as well as seasonalmigrants. The lowland habitat locatedbetween the Colorado River and theeast bank of the Main Cooling Reservoiroffers a significant source of water year-round.These natural resource areas,in concert with numerous additionalwetland and grassland areas, offer thekey ingredients necessary to sustainthe extensive wildlife population at theSouth Texas Project.

WATER QUALITY MANAGEMENT Water is an essential component inelec tricity production, and electricutilities must comply with extensivefederal, state, and local waterregulations. These regulations governvirtually every aspect of businessoperations at the South Texas Project.Water usage, wastewater treatmentonsite and certain maintenance andrepair activities are regulated under the Safe Drinking Water Act, theFederal Clean Water Act, and the TexasWater Quality Act. Collectively, theseActs provide for the safeguarding ofpublic drinking water supplies andmaintaining the integrity of state andfederal waters.

Regulating agenciesthat administer these requirementsinclude the United States ArmyCorps of Engineers, the United The South Texas Project continues tomonitor important wildlife species todetect population changes Photo courtesy of Kelly Callais Photo courtesy of Greg McMullin

CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 4-4 StatesEnvironmental Protection Agency, theTexas Commission on Environmental Quality, the Texas General Land Office the Lower Colorado River Authority,and the Coastal Plains GroundwaterConserva tion District.

The South Texas Project uses bothsur face water and groundwater forstation purposes. Consistent with thestations environmental principlesencouraging efficient water usage andconservation, surface and groundwaterusage are care fully managed toconserve this important resource.Groundwater is pumped from deepaquifer wells to provide onsite drinkingwater for station personnel, to replenishthe Essential Cooling Pond, and forother industrial purposes onsite.

Waterfrom the Main Cooling Reservoir andthe Essential Cooling Pond is usedas cooling water for plant operations.Water from the Colorado Riverreplenishes the Main Cooling Reservoirvia intermittent diversion periods.Surface water diverted to the MainCooling Reservoir from the ColoradoRiver accounted for approximate ly97% of the water used at the SouthTexas Project in 2023. Informationregarding water use in Texas can befound on the website maintained by the Texas Water Development Boardat www.twdb.texas.gov.

Most of the water used by the South Texas Project is needed to condensesteam and provide cooling for plantgenerating systems. The majority ofthis water is drawn from and returnedto the stations Main Cooling Reservoir.The Main Cooling Reservoir is a 7,000-acre, above grade, off-channel reservoircapable of impounding 202,600acre-feet of water at its maximum level. Water is diverted intermittently from the adjacent Colorado River to replenish the Main Cooling Reservoir.In addition, the Essential CoolingPond, a 47-acre, below grade, off channelreservoir that supplies waterto cool crucial plant components, iscapable of impounding 388 acre-feetof water. Various water rightspermits, contractual agreements, andcompliance documents authorizethe South Texas Project to maintainthese reservoirs, impound waterdiverted from the Colorado River,and to circulate, divert, and use waterfrom the reservoirs for industrialpurposes to operate the plant. Theseauthorizations also limit the amountand rate of diversion from the Colorado River to protect downstream environmental flow requirements forbays and estuaries. The South TexasProject diverted 42,137 acre-feet in2023 from the Colorado River for MainCooling Reservoir fill operations whilepreserving adequate freshwater flowconditions for down stream bay andestuarine ecosystems.

Approximately1,365 acre-feet of the water used bythe station was withdrawn from onsitegroundwater sources in 2023.

Existing federal and state water quality standards are implemented and enforced through the Texas Pollutant Discharge Elimination System (TPDES) permitprogram to restore and maintain thestates waters. Under this permit program,the South Texas Project monitors,records, and reports the types andquantities of pollutants from wastewaterdischarges to ensure that the SouthTexas Project meets the stringent levelsset in the permit. The TPDES permit wasrenewed in 2020. A monthly monitoringreport is submitted to the TexasCommission on Environmental Qualityfor wastewater discharges. Reports identifying groundwater use, surface water use, and water conservation are submitted annually to the Texas Water Continued on p.4-5 Photo courtesy of Christie Dement Photo courtesy of David Amador, Jr

4-5 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Development Board. Reports of surface water diversion and consumptive useare submitted to the Texas Commissionon Environmental Quality and the Lower Colorado River Authority. An annual groundwater use report is also submitted to the Coastal Plains GroundwaterConser vation District in accordance withground water district requirements.

Wastewater generated at theSouth Texas Project is processedand discharged to the onsite MainCooling Reservoir to be re-used bythe station as cooling water for plantsystems. No water was discharged from the Main Cooling Reservoirin 2023 other than from the reliefwells that are part of the reservoirembankment stabili zation system. Noaquatic monitoring was required to beconducted at the site in 2023 by theUnited States Environmental ProtectionAgency or the Texas Commis sion onEnvironmental Quality. Wastewater discharges met state and federalwater quality standards during theyear, while conserving and maximizingefficient water usage at the South TexasProject. In addi tion to the wastewaterdischarge permit program, the FederalClean Water Act, as amended, requirespermits for storm water dischargesassociated with industrial activity. TheSouth Texas Projects Storm WaterPollution Prevention Plan ensures thatpotential pollution sources at the siteare evaluated and that appropriatemeasures are selected and implementedto prevent or control the discharge ofpollutants in storm water runoff. Thisplan is a document that is revisedwhenever there is a change in design,construction, operation, or maintenancethat has a significant effect on thepotential for the discharge of pollutantsfrom the station. The stations Multi-Sector General Permit for storm waterdischarges was renewed in 2021.

Following a severe drought in 1996, theTexas Legislature recognized the needto address a wide range of state waterresource management issues. In 1997,the Texas Senate drafted legislation known as Senate Bill 1 to address these issues and to develop a comprehensive state water policy. The legislationrequired the Texas Water DevelopmentBoard to create a statewide water planthat empha sizes regional planning.Sixteen planning regions were created,each tasked to prepare a plan for theorderly develop ment, management,and conservation of water resources.The South Texas Project was chosento represent the interests of electricgenerating utilities for water-plan ningRegion K, encompassing the low erColorado River Basin. A state waterplan is prepared by the Texas WaterDevelopment Board every five yearsbased on the regional water plans.The regional water plans are revisedeach planning cycle based on updatedpopulation and water demand projections,water supply anal yses, and watermanagement strategies for a waterplanning horizon out to the year 2070.In November of 2020, the water planadopted by the Region K water planninggroup was submitted to the Texas WaterDevelopment Board and was approved in2021. The South Texas Project continuesto actively participate in the LowerColorado Regional Water Planning Groupto identify strategies to meet futurewater supply demand projections forthe region and to update the existing plan accordingly. Additional information regarding regional water planning in Texascan be found on the website main tainedby the Texas Water Development Boardat www.twdb.texas.gov.

Senate Bill 1 also required groundwater conservation districts to developground water management planswith estimates on the availability ofgroundwater in the district, detailsof how the district would managegroundwater, and management goalsfor the district. The water planning andmanagement provisions were further clarified in 2001 with the enactment of Senate Bill 2. Accordingly, the Coastal Plains Groundwater ConservationDistrict, encompassing MatagordaCounty, was confirmed by local electionin late 2001.

The purpose of thedistrict is to manage and protect thegroundwater resources of the district.The South Texas Project groundwaterwells are registered with the CoastalPlains Groundwater Conservation District. Operating permits for theground In 1999, the South Texas Projectimplemented a station WaterConservation Plan in accordancewith state water use regulations Photos 1, 3 and 4 courtesy of Greg McMullin. Photo 2 courtesy of Ian Halpin. Photo 5 courtesy of Michael Harvey.

CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 4-6 water wells were renewed inJanuary 2023, as required every threeyears.

Station personnel continue tomonitor onsite groundwater usageaccording to the requirements ofDistrict rules. Addi tional information regarding the Coastal PlainsGroundwater Conservation District can be found on its website at www.

coastalplainsgcd.com. In 2007, infurther recognition of the importanceof water conservation to meet futuredemands in the state, Senate Bill 3,enacted by the Texas Legislature,created a stakeholder-driven processfor the development of environmentalflows. Environmental flows are theamount of water necessary for a river,estuary, or other freshwater system tomaintain its health and productivity.

The law established a process todevelop environmental flow regimerecommenda tions for each major riverbasin in Texas.

The process tasked ateam of stakeholders from each area ofthe state, working with a science team,to develop a set of rec ommendationsto the Texas Commission onEnvironmental Quality and to perform ongoing periodic reviews of therecom mendations. The South TexasProject par ticipated as a member of thestakeholder committee that includedthe Colorado River and Matagorda Bay.The environ mental flow standards setflow levels at various points in riversand streams to protect water in therivers and estuaries along the coast.The existing South Texas Projectright to divert surface water was notimpacted by this legislation. Additional information regarding environmental flows can be found at: www.tceq.texas.

gov/permitting/water_rights/wr_techni cal-resources/eflows In February 2020, the TexasCommission on Environmental Qualityapproved a revised Lower ColoradoRiver Authority Water ManagementPlan. The Lower Colorado RiverAuthority Water Management Plan determines how water is allocatedfrom the Highland Lakes (specificallyLakes Travis and Buchanan) to meetthe needs of water users, includingthe South Texas Project, during watersupply shortages.

The process startedin 2019 when the Lower ColoradoRiver Authority submitted an updatedWater Management Plan to the TexasCommission on Environmental Qualityfor approval. The South Texas Project participated in the development ofthe revision for presentation to andapproval by the Texas Commission onEnvironmental Quality. Stakeholdersincluded represen tatives from cities,industry, lake area businesses andresidents, environmental interests,and agriculture. Additional informationon the Lower Colorado River AuthorityWater Management Plan can be foundat www.lcra.org.

In 1999, the South Texas Projectimple mented a station WaterConservation Plan in accordancewith state water use regula tions. Thepurpose of the Water Conservation Planis to identify and establish principles, practices, and standards to effectivelycon serve and efficiently use availableground and surface water supplies andmeet historical and projected averageindustrial water demand. Annualimplementation reports are submittedto the Texas Water DevelopmentBoard and the plan is updated everyfive years. The station re-submitted a revised plan to the Texas WaterDevelop ment Board in 2019. Managersand staff at the South Texas Projectunderstand the water resources of thestate are a critical natural resourcerequiring careful man agement andconservation to preserve water qualityand availability. Accordingly, the stationcontinues to support efforts focusingon the efficient use and conser vationof water resources.

Continued on p.4-7 Photo courtesy of Chelsea Pawlosky Photo courtesy of Gary Parkey

4-7 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT AIR QUALITY MANAGEMENT Air emission sources at the SouthTexas Project fall under the scope ofair pollu tion regulations promulgatedunder the Texas Clean Air Act, theFederal Clean Air Act and numerousassociated amendments.

The purposeof these regulations is to protect airresources from pollution by controllingor abating air pollution and harmfulemissions. Although nuclear generationof electricity is a form of zero-emissionclean energy, the South Texas Projectuses small amounts of fossil fuel forbackup and emergency equipment.

Regulated emission sources at theSouth Texas Project includes fossil-fueled emergency generators and fire pumps, and other minormaintenance equipment and activities.

The station is registered under TexasCom mission on Environmental QualityPermit By Rule Registration No.154767. This permit by rule registrationgrants the station the authority tooperate identified emission sources inaccordance with applicable permit andregulatory requirements.

In 2023, the South Texas Project had no reportable air emissions events and no violations.

Unlike conventional electricalgenerating stations, nuclear powerplants do not burn fossil fuel toproduce electricity. Therefore, theSouth Texas Project produces virtually no greenhouse gases or other airpollutants that are the typical byproductsof industrial power productionprocesses. The use of emissions freenuclear power is a significant contributor to the preservation of our communitys clean air resources.

NON-RADIOACTIVE WASTEMANAGEMENT Solid waste management proceduresfor hazardous and non-hazardouswastes generated at the South TexasProject ensure that wastes are properlydispo sitioned in accordance withapplicable federal, state, and localenvironmental and health regulations.By regulatory definition, solid wasteincludes solid, semi-solid, liquid, andgaseous waste material. The TexasCommission on Environmental Quality,which administers the Texas Solid WasteDisposal Act and the federal ResourceConservation and Recovery Act program,is the primary agency regulatingnon-radioactive wastes generated atthe South Texas Project. The TexasCommission on Environmental Quality regulates the collection, handling,storage, and disposal of solid wastes, including hazardous wastes. Thetransportation of waste materialsis regulated by the United StatesDepartment of Transportation.

The South Texas Project is classified asa small quantity generator of industrialsolid wastes. Texas Commission onEnvironmental Quality regulationsrequire industrial solid wastesgenerated at the South Texas Project tobe identified to the Commission. These are listed in the Texas Commissionon Environmental Quality Noticeof Registration for the South TexasProject. The registration is revisedwhenever there is a change in wastemanagement practices atthe site.

Hazardous waste and ClassI non-hazard ous waste handling anddisposal activities are summarizedand documented in a Photo courtesy of Christopher Kalka Photo courtesy of Rob Nies

CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 4-8 waste summaryreport for the South Texas Projectthat is submitted annually to theTexas Commission on Environmental Quality. The South Texas Projectfive-year Source Reduction and WasteMinimization plan for hazardouswaste was last updated and theassociated executive summary wassubmitted to the Texas Commission onEnvironmental Quality in 2019.

Hazardous waste accumulation at the South Texas Project in 2023 was limited to a maximum holding period of 180 days.The Resource Conservation and RecoveryAct and Texas Solid Waste Dis posal Actalso requires the use of proper storageand shipping containers, labels, manifests,reports, personnel training, a spill controlplan, and an accident contin gencyplan. South Texas Project personnel routinely inspect areas throughout thesite to ensure wastes are not stored oraccu mulated inappropriately.

South Texas Project policies andregulations encourage the recycling, recovery, or re use of waste, whenpossible, to reduce the amount ofwaste generated or disposed of inlandfills. Approximately 59 percent ofthe industrial non-radioactive waste generated in 2023 at the South TexasProject was recycled or processed forreuse (Reference Figure 4-1). Usedoil, diesel fuels, electro-hydraulicfluid, and used oil filters were sent toa recycling vendor for reprocessing. Empty polyethylene drums arereturned, when possible, to the originalmanufacturer for reuse. In addition, thestation supports recycling programsfor cardboard, paper, aluminum, printercartridges and plastic. Approx imately35 tons of scrap metal were removedfrom the station for recycle in 2023.The South Texas Project continues toexplore new areas where recycling maybe expanded or initiated.

Non-radioactive solid waste thatcannot be shipped for recycling isshipped for disposal.

Municipal type trash is transported to anoffsite landfill. Hazardous waste accountsfor only a small portion of the wastegenerated at the South Texas Project.Minimization and reduction of hazardouswaste generation where feasible remainsan important goal.

Changes in theamount of hazardous waste shippedeach year generally reflect differencesin operation and maintenance activities.Successful waste minimization andsource reduction efforts by employees have allowed the South Texas Project to remain classified as a small-quantitywaste generator since 2004. (ReferenceFigures 4-2 and 4-3).

CHEMICAL CONTROL ANDMANAGEMENT The stations Integrated Spill Contingency Plan for the South Texas Project,last updated and re-certified in 2019,consolidates multiple federal and staterequirements into one plan. The planis implemented through standard siteoperating procedures and guidelines.The South Texas Project uses standardoperating procedures, policies, andprograms to minimize the generation ofwaste materials, control chemical use,and prevent spills. The South TexasProject also evaluates chem icals andproducts prior to their approval foruse at the station. Site procedures thatimplement the stations Integrated SpillContingency Plan and the stations Chemical Control Program address the evaluation, storage, use, labeling, spill control, and disposal requirementsof chemicals. These guidelines alsoassist in reducing waste generation,ensuring proper packaging for disposal,and mitigating the consequences ofinadvertent spillage.

The South Texas Project emphasizes awareness training for spill preventionand maintains readiness to respondshould a spill occur. Spill responseteam members receive annualrefresher training in hazardous materialincident response.

The South TexasProject did not have any reportableliquid spills in 2023.

Photo courtesy of Kelly Callais

4-9 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Figure 4-1 Figure 4-2 Figure 4-3

CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 4-10 The South Texas ProjectsEnvironmental Protection Plan wasissued in March of 1989 to protect nonradiologicalenviron mental monitoringparameters during operation of thenuclear plants. This report reviewsEnvironmental Protection Plan noncompliances,if any, identified in 2023and the associated corrective actionstaken to prevent recurrence.

Potentialnon-conformities are promptly addressed to maintain operations in compliance with plan requirements.

Plant personnel use a conditionreporting process to document theseconditions and track corrective actionsto completion.

Internal assessments,reviews and inspec tions are also usedto ensure compliance.

Events that require notifications tofederal, state, or local agencies arereported in accordance with theapplicable reporting requirements.The United States Nuclear RegulatoryCommission is provided with a copyof any such reports at the time they aresubmitted to the cognizant agency.

If anon-routine event occurs and a report is not required by another agency,then a 30-day report to the UnitedStates Nuclear Regulatory Commissionis required by the EnvironmentalProtection Plan. No such 30-day orother non-routine event report wasrequired in 2023.

ENVIRONMENTAL PROTECTION PLAN STATUS This annual report also reviews non-routine reports submitted by plant personnel and any activities thatinvolved a potentiallysignificant unreviewed environmental question. A proposed change, test or experiment is considered to present an unreviewed environmental question if it concerns:

• A matter that may result in a significant increase in anyadverse environmental impact previously evaluated in theFinal Environmental Statement related to the operationof South Texas Project, Units 1 and 2 (Docket Nos. 50-498and 50- 499), environmental impact appraisals, or in anydecisions of the Atomic Safety and Licensing Board.

• A significant change in effluents or power level.

• A matter not previously reviewed and evaluated inthe documents specified in (1) above, that may have asignificant adverse environmental impact.

No unreviewed environmental questions were identified in 2023.

Non-routine report reviews Photo courtesy of Christie Dement

RADIOLOGICAL ENVIRONMENTAL INTRODUCTION

SUMMARY

5-1 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER FIVE RADIOLOGICAL ENVIRONMENTAL INTRODUCTION &

SUMMARY

5-2 Only Tritium and naturally occurring radioactive material were identified in theoffsite environmental samples in 2023.

Samples of fish and meat collected and analyzed showed no South Texas Project related nuclides were present. Watersamples from the onsite drinking watersupply from the deep aquifer and fromoffsite sampling stations on the ColoradoRiver show only natural backgroundradioactivity.

The station also monitorsfor radioactivity in onsite sediment fromthe Main Cooling Reservoir and ditches.Measurements of direct radiation onsiteand offsite indicated no federal doselimits were exceeded.

Tritium is a radioactive isotope ofhydrogen that is produced in the reactorand cannot be removed from effluentsreleased to the Main Cooling Reservoirbecause it is part of the water molecule.

Due to the design of the Main Cooling Reservoir, the presence of Tritium in various sloughs and ditches onsite andthe shallow aquifer is expected. Tritiumhas been detected in these types ofsamples and the concentrations remainbelow the United States EnvironmentalProtection Agency drinking water limits.

A sampling program was developed to monitor the Tritium in the immediatearea around the plant for long termtrending.

Wells are sampled eithersemi-annually, annually, or once everyfive years, depending on location andthe amount of Tritium present. TheTritium concentration remained belowthe United States Envi ronmentalProtection Agency drinking water limitsin 2023 and within the design basis ofthe South Texas Project.

Analyses of the data collected from the implementation of the RadiologicalEnvi ronmental Monitoring Program indicates that the operation of the South TexasProject has no adverse radiological impact.

Photo courtesy of Gary Parkey Photos 1 and 2 courtesy of Kelly Callais. Photos 3 and 4 courtesy of Greg McMullin.

The Radiological EnvironmentalMonitoring Program is designedto evaluate the radiological impactof the South Texas Project on theenvironment by collecting andanalyzing samples for low levelsof radioactivity. Measurements ofsamples from the different pathwaysindicate that there continues to beno adverse effect offsite from theoperation of the South Texas Project.

Wells are sampled either semi-annually, annually, or once every five years CHAPTER FIVE

6-1 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-2 Analyses of the environmentalpathways require that samples be takenfrom water, air, and land environments.These samples are obtained to evaluatepotential radiation exposure to people.

Sample types are based on established pathways and experience gained atother nuclear facilities. Sample locationswere determined after consideringsite meteo rology, site hydrology, localdemography, and land use. Samplinglocations are further evaluated andmodified according to field and analysisexperience. Table 1 at the end of thissection lists the required samplinglocations and frequency of collection.

Additional discretionary samples were also collected.

Sampling locations consist of Indicator Stations and Control Stations. Indicator Stations are locations on or off thesite that may be influenced by plant discharges during plant operation.Control Stations are located beyondthe measurable influ ence of theSouth Texas Project. Although mostsamples analyzed are accompanied bya control sample, it should be noted that this practice is not always possibleor meaningful with all sample types.Fluctuations in the concentration ofradionuclides and direct radiationexposure at Indicator Stations areevaluated in relation to historicaldata and against the Control Stations.Indicator Stations are compared withcharacteristics identified during the pre-operational program to monitor for radiological effects from plant operation.

Two sample identification methods are used in the program. Figures 6-1 and6-2 are maps that identify permanentsample stations. Descriptions ofsample stations shown on Figures 6-1and 6-2 are found in Table 2. Table 2also includes supplemental samplinglocations and medium types that may beused for additional information.

Figure6-3 illustrates zones that may be usedto complement permanent, numbered sample stations.

Environmental samples from areassur rounding the South Texas Projectcontinue to indicate no radiologicaleffects from plant operation. Measuredvalues from offsite indicator samplestations continue to trend with theControl Stations.

Measurements fromonsite indicator samples continued tofluctuate within normal historical ranges.

PROGRAM DESCRIPTION Photo courtesy of Christie Dement Photo courtesy of Christie Dement CHAPTER SIX Photo courtesy of Gary Parkey The South Texas Project initiateda comprehensive pre-operational Radiological EnvironmentalMonitoring Program in July 1985.That program terminated on March 7,1988, when the operational programwas implemented.

The data from thepre-operational monitoring programform the baseline against whichoperational changes are measured.

6-3 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM DESIGNATED SAMPLE LOCATION MAP (Offsite locations are numbered)

Figure 6-1

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-4 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM ONSITE SAMPLE LOCATION MAP Figure 6-2

6-5 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Figure 6-3 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM ZONE LOCATION MAP The zone station is determined in the following manner:

• The first character of the station number Z to identify it as a zone station.

• The second character is the direction coordinate No. 1-8.

• The third character is the distance from the site No. 1-6.

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-6 Average quarterly air particulate sample beta radiation activity from threeonsite Indicator Stations and a singlecontrol station have been comparedhistorically from 2001 through 2023(see Figure 6-4).

The average of theonsite indicators trends closely with theoffsite control values. The comparisonillustrates that plant operations arenot having an impact on air articulate activity even at the Sensitive IndicatorSta tions (#1, #15, and #16). These stationsare located near the site boundarydownwind from the plant, based onthe prevailing wind direction. The betaactivity measured in the air particulatesamples is from naturally occurringradioactive material.

Gamma radiationanalyses are performed on quarterlycomposites of the weekly air particulatesamples to determine if any activity isfrom the South Texas Project.

The gamma analyses revealed no radioac tivity fromthe South Texas Project.

AIRBORNE PATHWAY Figure 6-4 DIRECT EXPOSURE PATHWAY Direct gamma exposure ismonitored in the environment withthermoluminescent dosimeters(TLDs) located at 40 locations aroundthe site. The natural direct gamma exposure varies according to location because of differences in the naturalradio active materials in the soil, soilmoisture content, and other factors.Figure 6-5 compares the amount ofdirect gamma exposure measured atthe plant since the first quarter of 2001from three different types of stations.The South Texas Project started usinga vendor for offsite processing of thethermoluminescent dosimeters forenvironmental measurement of di rectradiation during the third and fourth quarter of 2014. The Control Stations,Stations

1. 23 and #37, are greater than10 miles from the site in the minimalwind direction.

The prevailing winddirection was into the northwest sector.The Sensitive Indicator Stations areone-mile NW, NNW, and N from the plants on FM 521 at Stations

1. 15, #16 and#1 respectively. The Indicator Stationsare the remainder of the required monitoring stations.

The values plotted are the averages forall the stations according to type. Theaverage of the Control Stations is higherthan the other stations because Station#23 is in an area that has slightly highernatural background radiation. The trendsof Figure 6-5 show that South TexasProject is not contributing to the directradiation in the offsite environment.

Photo courtesy of Greg McMullin Photo courtesy of Jean Franklin

6-7 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Figure 6-5 Figure 6-6 Figure 6-7

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-8 SEDIMENT SAMPLES The cobalt-60 inventory in the reservoir has decreased since 1992 becauseof radioactive decay and installedequipment to reduce radioactiveeffluents. Although the total activityof cobalt-60 has decreased over time,an inventory of cobalt-60 is still inthe reservoir as seen occasionallyat Stations #215 and #216. In 2023,cobalt-60 was identified in three out ofseven Main Cooling Reservoir sedimentsamples taken, all results were lessthan the reporting levels. Figure 6-7demonstrates the calculated declinein the total amount of cobalt-60in the reservoir. Bottom sedimentsamples are taken from the MainCooling Reservoir each year. A studywas performed in 2010 to locate the distribution and concentrationsof cobalt-60 and cesium-137 in theMain Cooling Reservoir. Although nocobalt-60 was detected from 2007through 2010 at Stations #215 and #216,the concentration of cobalt-60 is notuniformly distributed in the reservoirsediment and some cobalt-60 remains.The highest cobalt-60 measure mentin 2023 was 67.8 pCi/kg at station

1. 215, whichis considerably less than the reportablelevels. Figure 6-6 and Figure 6-7 showthe results from the plant-pro ducedcobalt-60 from the Main Cooling Reservoir. Cobalt-60 was not identified in any other sediment sample outside the Main Cooling Reservoir in 2023.

Cesium-137 was measured in four out of six bottom sediment samplesfrom Stations #215 and #216 in the MainCooling Reservoir in 2023. The highestmeasure ment was 82.3 pCi/kg at Station#216. The highest cesium-137 detectedat station 215 was 68.9 pCi/kg. Cesium-137 is often foundin environmental media including soiland sediment as residual radio-active material resulting from above ground nuclear weapons testing conducted in the 1950s and 1960s. Soil and sediment samples taken in 1986 and 1987 priorto operation of the South Texas Project contained cesium-137 from weapons testing. The average pre-operational cesium-137 concentration was 118 pCi/

kg in soil and sediment samples, and thehighest sample concentration was 383pCi/kg. Cesium-137 activities measured at Station #215 in 2023 were slightlyhigher than previously detected dueto sampling non-homogeneous media.Results remained considerably less thanreportable levels.

The measured valuesat Station #215 and

1. 216 are consistentwith pre-operational concentrationsreduced by 30 years of radioactive decay.

Photo courtesy of Brad Conner Photo 1, 3 and 4 courtesy of Greg McMullin. Photo 2 courtesy of Gary Parkey. Photo 5 courtesy of Kelly Callais.

6-9 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Figure 6-8 Figure 6-9

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-10 Tritium has been detected in theshallow aquifer on the south sideof the Main Cooling Reservoir since1999. Models used when licensing thesite predicted Tritium in the shallowaquifer. These models were validatedwith additional studies in 2013.

A siteconceptual model, initially developed in 2008and updated in 2014, 2018 and 2023, validated theoriginal predictions of the site hydrologystudy. The revision in 2018 include Independent Spent FuelStorage Installation Project construction.

Tritium is a radioactive isotope ofhydrogen and is produced in thereactors during plant operation.Wastewater is treated to removeimpurities before release, but Tritiumcannot be removed because it ischemically part of the water molecule.

Some of the Tritium is released intothe atmosphere and the remainderis released into the Main CoolingReservoir. The Tritium escapes from theMain Cooling Reservoir by evaporation,movement into the shallow aquifer,and by percolation from the reliefwells which are a part of the reservoirembankments stabilization system.Figure 6-8 shows the amount of Tritiumreleased to the Main Cooling Reservoireach year and the amount pres entduring the last quarter of each year.

The concentration of Tritium in theMain Cooling Reservoir was relativelystable in 2023. The amount of Tritiummeasured in the Main Cooling Reservoirwas consistent with the amount usuallyreleased to the reservoir. The amountof rainfall and reservoir makeup fromthe Colorado River influences theconcentration of Tritium in the MainCooling Reservoir and the shallow aquifersurrounding it.

Tritium enters the sloughsand ditches of the site as runoff from therelief wells that surround the reservoir.In 2023, Tritium levels remainedconsistent with historical values inthe relief wells as shown in Figure 6-9.Sampling of Main Cooling Reservoirrelief well #701 has been discontinueddue to no water flow at that location.Another existing Main Cooling Reservoirrelief well #707, is now used as arepresentative substitute for sampling therelief well water from the Main CoolingReservoir. Station #707 is just west of thediscontinued relief well

1. 701 on the southside of the Main Cooling Reservoir. Dueto different flow rates of water throughthe relief wells, the base concentrationis slightly higher at relief well #707compared to #701. The highest 2023sample from relief well #707 indicated approximately 5,162 pCi/kg, which is lessthan required reporting levels.

WATERBORNE PATHWAY Photo courtesy of Kelly Callais Photo courtesy of Greg McMullin

6-11 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Figure 6-10 Figure 6-11

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-12 The Tritium concentrations in eightsurface water sample locations from2001 through 2023 are shown in Figure6-10. The specific sample point locationscan be found in Table 2. Tritium levelsin the onsite sloughs and ditches varywith the concentration in the reservoirand the amount of rainfall received. Theaverage Tritium concen tration in therelief well, sloughs, and ditches is lessthan the reservoir because the wateris diluted as it migrates through thereservoir relief well system. In 2023, five out of twelve required surface water samplelocations tested positive for Tritium.All test results were below the UnitedStates Environmental Protection Agencydrinking water limit of 20,000 pCi/kg.Rainwater was collected and analyzedduring 2023 to determine if the Tritiumfrom the reservoir precipitated in thelocal area. Tritium was not measured inany of the rainwater samples offsite.

Tritium was identified in the shallow(i.e.,

ten to thirty feet deep) aquifer testwells at Station #235 approximatelyseventy-five yards south of the reservoirembankment base during 1999. Startingin 2000, samples were collected fromthe shallow aquifer well at Station #251south of the Main Cooling Reservoir.The Tritium results from these twoshallow aquifer wells are shown inFigure 6-11. In 2023, the concentrationof Tritium at Station #235 was consistentwith values over the past years.The highest concentration for wells in the owner-controlled area was 5,510 pCi/kg in 2023 at Station #251. Tritium lev els continued to remainbelow the United States EnvironmentalProtection Agency drinking water limit(20,000 pCi/kg).

Shallow aquifer Tritium concentrations have remained near the concentrations found in the relief wells. Wells at Stations

1. 258 and #259 on the west side of thesite boundary have been sampled since2006.

Wells at Stations #270 and #271were installed during the last quarterof 2008.

The sample results are shownin Figure 6-12. The well at Station #271,located adjacent to site property on acounty road easement directly west ofthe Main Cooling Reservoir, indicated itshighest concentration for 2023 at 1780pCi/kg.

In 2023, a maximum value of826 pCi/ kg was identified for onsite testwells in the protected area. Tritium levels continued to remainbelow the United States Environ mentalProtection Agency drinking water limit(20,000 pCi/kg).

Photo courtesy of Kelly Callais Photos 1-4 courtesy of Gary Parkey, Greg McMullin, Diep Tran and Pedro Garcia

6-13 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

Tritium has not been detected in thedeep aquifer that is the source ofdrinking water for the local communitiesand homes. These measurements followthe hydro-logical model described in theoriginal license basis and the updatedsite conceptual model discussed earlierin this section.

A windmill-powered well, Station#267, was below detection in 2023. This onsite ground water sample station is themost distant location from the MainCooling Reservoir that Tritium hasbeen detected.

This well is not used forhuman consumption.

The drinking water onsite is pumpedfrom deep aquifer wells and is collectedmonthly and composited quarterlyto verify Tritium is not present. TheSouth Texas Project does not usewater from the reservoir, shallowaquifers, or other surface water fordrinking. If the water with the highest Tritium concentration that leavesthe site was used for drinking, themaximum dose to an individual wouldbe less than one millirem in a year.This dose is insignificant comparedto the approximately 620 mil lirem thepublic receives a year from naturalradio-activity in the environment and the radiation received frommedical procedures.3 Other samples are collected andanalyzed in addition to those requiredby our licensing documents or internalprocedures. These samples arecollected to give additional assurance that the public and the environmentare protected from any adverse effects from the plant. These sam ples includepasture grass, sediment samples,rainwater, shallow aqui fer well, waterfrom various ditches and sloughs onsite,direct radiation, and air samples nearcommunities or other areas of interest.The results of these analyses indicatethat plant operation has no health impact offsite and is well within stateand federal regulations and guidelines.

3NCRP (2006). National Council onRadiation Protection and Measurements,Ionizing Radiation Exposure of thePopulation of the United States, (Bethesda,Maryland), NCRP Report No. 160.

Photo courtesy of Gary Parkey CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-14 Photo courtesy of Gary Parkey Figure 6-12 Photo courtesy of Christie Dement

6-15 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT In 2007, the Nuclear Energy Institute(NEI) established a standard formonitoring and reporting radioactiveisotopes in ground water entitled NEIGroundwater Protection Initiative,NEI 07-07. The station implemented the recommendations of this industry standard and has broadened theground water monitoring program toinclude addi tional samples collectednear the plants.

Some of the positiveresults of this broad ened monitoringprogram reflect Tritium associated withthe Main Cooling Reservoir.

Wells near the plants are sampledsemi-annually, annually, or onceevery five years depending on theconcentration of Tritium anticipatedand the location of the wells.

Wells with high concentrationsare sampled more frequent over afive-year period which followSTP procedure requirements.

Figure6-13 contains the 2023 results for wells that weresampled along with the historical highs measured prior to2023 for each station since sampling began in 2006.

Theirlocations are shown in Figure 6-14.

Two wells sampled annually (Stations#807 and #808) are adjacent to where apipe was damaged and repaired severalyears ago. The Tritium concentration atthese two wells continued to decreaseas expected in 2023. Station #809Tritium concentra tions were relatedto the previously refer enced pipe andsubsequent repair. All the wells sampledin 2023 that had detectable Tritium areinfluenced by groundwater originatingin the Main Cooling Reservoir.

Theirconcentrations remain in the range ofgroundwater Tritium concentrationsas sociated with the Main CoolingReservoir.

All the 2023 measurementsof Tritium in groundwater are asmall fraction of the United StatesEnvironmental Protection Agencydrinking water limit (20,000 pCi/kg).

During 2012, steam traps for theauxiliary steam system that couldpotentially con tain trace amounts of Tritium were mod ified to re-direct thecondensed steam or liquid water to theMain Cooling Reservoir.

Informationregarding the steam traps and subsequentresponse was documented in thestations condition reporting process.

This evaluation identified no neweffluent release pathways and no impactto the drinking water or the health andsafety of the public.

By the end of 2014, the majority of theprotected area wells had under gone amodification to enhance the protection of the structural integrity of the waterwell casing used for sampling the upper aquifer. The modi fications werecompleted in 2016 with contin uedimprovements.

In 2023, there were four occurrences where condensed steam or water contactedthe ground onsite. This occurrence didnot result in impact to the public or the environment. No discharge occurredoffsite or to groundwater that may beused as a source of drinking water.Where ap plicable, the water was quicklyrecovered, recaptured, and clean upcompleted with no impact to groundwater.

NEI GROUNDWATER PROTECTION INITIATIVE Figure 6-14 STP Protected Area Ground Water Monitoring Wells Photo courtesy of Gary Parkey Figure 6-13 STP Protected Area Ground Water Monitoring Results

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-16 LAND USE CENSUS The Annual Land Use Census isperformed to determine if any changeshave occurred in the location ofresidents and the use of the land withinfive miles of the South Texas Project.The information is used to determinewhether any changes are needed in theRadiological Environmen tal MonitoringProgram. The census is performed bycontacting local government agenciesthat provide the information.

In addition, a survey is performed toverify the nearest residents within five miles of the South Texas Project generating units in each of 16 sectors.

The results of the survey indicated nochanges for 2023. The eleven sectorsthat have residents within five miles andthe distance to the nearest residence ineach sector are listed below.

• No commercial dairies operate within Matagorda County.

• There were no identified animals producing milk for human consumption located within five miles of STP.

• A commercial olive tree orchard is located approximately 4.9 miles WSW of the plant.

• One commercial fish farm continues to operate. It is located approximately four to five miles southwest of the plant located in the area north of Robbins Slough Road and east of South Citrus Grove Road. The water supply for the ponds is not affected by the operations of the South Texas Project.

• Colorado River water from below the Bay City Dam has not been used to irrigate crops.

• There were no identified commercial vegetable farms located within the five-mile zone.

• Broadleaf vegetation sampling is performed at the site boundary in the three most leeward sectors and at a control location in lieu of a garden census. The broadleaf vegetation samples collected also satisfy the collection requirement when milk samples are not available.

Land Use Census items of interest Quality assurance encompassesplanned and systematic actionsto ensure that an item or facilitywill perform satisfactorily.

Reviews,surveillances, and audits have determined that the programs,proce dures, and personnel areperforming at a satisfactory level.

Quality audits and independenttechnical reviews help to determineareas that need attention. These areasare addressed in accordance with thestations Condition Reporting Process.

The measurement capabilities ofthe Radiological Laboratory aredemonstrat ed by participating inan interlaboratory measurementassurance program as well asperforming duplicate and split sampleanalyses. Approximately 20.5 percentof the analyses performed are qualitycontrol samples. These consistof interlaboratory measurementassurance program samples, duplicatesamples, and split samples. Allanalyses include Department of Energys Mixed Analyte Performance Evaluation Program sam ples,blanks, intercomparison testing,du plicates and splits out of a total of1339 samples analyzed for 2023.

The interlaboratory measurementas surance program provides samplesthat are similar in matrix and size tothose measured by the RadiologicalEnviron mental Monitoring Program.This program assures that equipmentcalibrations and sample preparationmethods accurately measureradioactive material in samples.

Figure6-15 summarizes the results of theinterlaboratory comparison programs.

Duplicate sampling of the environment allows the South Texas Project toestimate the repeatability of thesample collec tion, preparation, andanalysis process.

Splitting samplesallows estimation of the precision andbias trends of the method of analysiswithout the added variables introducedby sampling. Generally, two samplessplit from the same original samplematerial should agree better than twoseparate samples collected in the samearea and time. The 2023 variances for duplicates and splits are shown in Figure 6-16.

QUALITY ASSURANCE Photo courtesy of Christie Dement Photo courtesy of Vicki Rowland

Figure 6-15 Figure 6-16 6-17 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-18 In addition to measurement accuracy, radiochemical measurements mustmeet sensitivity requirements atthe Lower Level of Detection forenvironmental samples. Deviations fromthe sampling program or sensitivityrequirements must be acknowledgedand explained in this report. The lossof a small fraction of the total samplescollected in 2023 did not impact theability to demonstrate that the SouthTexas Project continues to operate withno negative effect on the population orthe environment.

During 2023 samples not collected or unacceptable for analysis:

• Three out of 260 Offsite Dose Calculation Manual (ODCM) required air samplewere not collected due to loss of powerfrom Station #15 and #16.

• Two air samples not required by the ODCM were not contin uouslycollected for the full-time interval becauseof power or equipment failures from station #35 and #6 duplicate.

• Two broadleaf vegetation samples werenot collected in January and February due to weatherconditions. Since these samples were outside the growing season they were not requiredby the ODCM.

• There were two instances where TLDresults used for measuring directradiation were not collected. Both werehit by the mower and were not recovered.

PROGRAM DEVIATIONS Photo courtesy of Ian Halpin Photo courtesy of Kelly Callais

TABLE 1 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM MCR-STP Main Cooling Reservoir STP-South Texas Project 6-19 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-20 TABLE 1 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM (CONT.)

Photo courtesy of Christie Dement MCR-STP Main Cooling Reservoir STP-South Texas Project Photo courtesy of Kelly Callais

6-21 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT TABLE 1 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM (CONT.)

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-22 TABLE 2 SAMPLE MEDIA AND LOCATION DESCRIPTIONS Photo courtesy of Kelly Callais

6-23 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-24 TABLE 2 SAMPLE MEDIA AND LOCATION DESCRIPTIONS (CONT.)

This station may be used to obtain the required aquatic samples in the vicinity of STP that may be influenced by plant operations.

MCR-STP Main Cooling Reservoir STP-South Texas Project Media codes typed in bold satisfy collection requirement described in Table 1.

Station codes typed in bold identify offsite locations.

• Control Station Photo courtesy of Gary Parkey

6-25 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

Photo courtesy of Vicki Rowland This station may be used to obtain the required aquatic samples in the vicinity of STP that may be influenced by plant operations.

MCR-STP Main Cooling Reservoir STP-South Texas Project Media codes typed in bold satisfy collection requirement described in Table 1.

Station codes typed in bold identify offsite locations.

• Control Station CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-26 TABLE 2 SAMPLE MEDIA AND LOCATION DESCRIPTIONS (CONT.)

6-27 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-28 This station may be used to obtain the required aquatic samples in the vicinity of STP that may be influenced by plant operations.

MCR-STP Main Cooling Reservoir STP-South Texas Project Media codes typed in bold satisfy collection requirement described in Table 1.

Station codes typed in bold identify offsite locations.

• Control Station TABLE 2 SAMPLE MEDIA AND LOCATION DESCRIPTIONS (CONT.)

Photo courtesy of Gary Parkey

6-29 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER FOUR NON-RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-30 TABLE 2 SAMPLE MEDIA AND LOCATION DESCRIPTIONS (CONT.)

Photo courtesy of Kelly Callais

6-31 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

A summary of all required samples isgiven in Table 3. The table has beenformatted to resemble a United StatesNuclear Regulatory Commissionindustry standard.

Modifications havebeen made for the sole purpose ofreading ease. Only positive values aregiven in this table.

Media type is printed at the topleft of each table, and the units ofmeasurement are printed at the topright. The first column lists the typeof radioactivity or specific radionuclidefor which each sam ple was analyzed.The second column gives the totalnumber of analyses performed andthe total number of non-routineanal yses for each indicated nuclide. Anon-rou tine measurement is a samplewhose mea sured activity is greater thanthe reporting levels for RadioactivityConcentrations in EnvironmentalSamples. The LOWER LIMIT OFDETECTION column lists the normalmeasurement sensitivities achieved.The sensitivities were better thanrequired by the United States Nuclear Regulatory Commission.

A set of statistical parameters is listedfor each radionuclide in the remainingcolumns.

The parameters containinformation from the indicator locations,the location having the highest annualmean, and information from the ControlStations. Some sample types do nothave Control Stations. When this is thecase, no samples is listed in the controllocation column.

For each of these groups of data,the following is calculated:

• The mean positive values

• The number of positivemeasurements/

the total numberof analyses

• The lowest and highest valuesfor the analysis The data placed in Table 3 are from thesamples required by the sites Offsite DoseCalculation Manual as described in Table 1.Additional thermoluminescent dosimeterswere utilized each quarter for qualitycontrol purposes. The minimum samplesrequired by Table 1 were supple mentedin 2023 by numerous direct radiationmeasurements, additional surface watersamples, ground water sam ples, additionalpasture grass, additional rainwatersamples, additional relief well watersamples, and additional sediment samples.Fish and crustacean samples vary innumber according to availabili ty, butexceeded the minimum number requiredby Table 1, as well as other meat samples.Also, numerous air station sam ples werecollected from weekly air sample stations,in addition to the minimum number ofsamples required by Table 1 to strengthenthe Radiological Environmen talMonitoring Program.

The minimum required Radiological Environmental Monitoring Programis presented in Table 1. The table isorganized by exposure pathway. Specificrequirements such as location, samplingmethod, collec tion frequency, andanalyses are given for each pathway.

STP followed the American National Standard Institute (ANSI)/Health Physics Society (HPS) N13.37 methodology from 2015 to 2023 using Panasonic Thermoluminescent Dosimeters (TLD) for measurement of Di rect Radiation. Quarterly Facility Dose was Not Detected (ND) for each of these Direct Radiation stations for 2023 as the values minus the baseline were less than five mrem, minimal detectable activity. These values were considered below background values (see chart on page 6-33).

RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM ANALYSIS

SUMMARY

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-32 Photo courtesy of Christie Dement Photos courtesy of Kelly Callais and Bethani Wittig

6-33 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Photo courtesy of Kelly Callais CHART 1 ANSI/HPS N13.37 STP ENVIRONMENTAL DOSIMETRY RESULTS

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-34 Photos courtesy of William Sharpe and Chelsea Pawlosky

6-35 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-36

6-37 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Photo courtesy of Gary Parkey

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-38 Photo 1 courtesy of Christie Dement. Photos 2 and 3 courtesy of Gary Parkey.

6-39 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT Photos courtesy of William Sharpe and David Adams

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-40 Photos 1 and 3 courtesy of Gary Parkey. Photo 2 courtesy of Greg McMullin.

6-41 STP 2023 ANNUAL ENVIRONMENTAL OPERATING REPORT

CHAPTER SIX RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT 6-42 Photo courtesy of Gary Parkey

1-1 STP l ANNUAL ENVIRONMENTAL OPERATING REPORT Maps provided by Janice Hopes Cover photo by Vicki Rowland Other photos courtesy of: David Adams, David Amador Jr., Michael Berry, Robert Bowers, Kelly Callais, Brad Conner, Christie Dement, Jean Franklin, Pedro Garcia, Ian Halpin, Michael Harvey, Christopher Kalka, Greg McMullin, Rob Nies, Gary Parkey, Chelsea Pawlosky, Vicki Rowland, William Sharpe, Diep Tran and Bethani Wittig.

Graphics by Diane Davis Design Coordination and support by Corporate Communications