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Tritium Management and Groundwater Contamination Review at Braidwood Generating Station

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25 diapositives · 401 Views · Dec 13, 2012

The Braidwood Generating Station's operational history, highlighting its dual Westinghouse pressurized water reactors, and discusses the station's management of tritium discharges. Following historical leaks from the circulating water blowdown line and the subsequent contamination of groundwater, an Issues Management Team established thorough characterization and remediation strategies. Key regulatory challenges and community relations efforts are addressed, along with insights into groundwater monitoring, sampling techniques, and proactive measures to manage tritium migration and protect local water sources.

#braidwood station #tritium management #groundwater contamination #environmental monitoring #radioactive releases #regulatory compliance #remediation efforts #community outreach
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  1. Braidwood Generating Station Tritium Review Presentation to RETS/REMP WorkshopJune 26, 2007

  2. Braidwood Station Background • Dual-unit Westinghouse pressurized water reactors • Construction permit December 1975 • Unit One operation July 1988 • Unit Two operation October 1988 • (Initial operating licenses good for 40 years) • Generation capability Unit 1 – 1248 MWe Unit 2 – 1224 MWe • Number of employees 615 (Exelon)

  3. Circulating Water Blowdown Line • Station exchanges clean water with Kankakee River for cooling lake through circulating water make up and blowdown lines • In addition, blowdown line caries periodic discharges of liquid radioactive waste • Tritium is principal component; other activity is significantly reduced via radwaste system (filters, demineralizers, RO) • Prior to 11/05, discharges 2-3 times per week • Discharge concentration limits contained in offsite dose calculation manual (ODCM) • 10 times limits in 10 CFR Appendix B • For tritium, concentration limit is 1 E+7 pico-curies/liter • Non-radiological aspects of discharge regulated by NPDES permit

  4. Circulating Water Blowdown Line

  5. Chronology • Three significant VB leaks 1996-2000 • VB-1: 11/96, ~380K gallons • VB-3: 12/98, ~3M gallons • VB-2: 11/00, ~3M gallons • Inadequate response at the time • IEPA questions raised regarding Godley; sampling initiated - 3/05 • Environmental contractor engaged to install sampling wells - 6/05-11/05 • Identified elevated groundwater tritium concentrations near site border - 11/05 • Ceased liquid radioactive releases – 11/05 • Formed issues management team and root cause team – 11/05

  6. Issues Management Team Role • Characterize source and extent of contamination • Develop and implement remedial action • Coordinate/support external response efforts • Public outreach/media response • Regulatory • Government • Legal • Real estate • Support root cause team

  7. Regulatory Issues • NRC • Violations for failure to document and assess impact of releases • Low to moderate safety significance (white) • Oversight of characterization and remediation efforts • Illinois EPA • Lead agency is Bureau of Water • Violation Notices for exceeding IEPA groundwater quality standard and non-degradation standard • Exelon community relations plan • Jurisdictional issues for regulation of radioactive releases

  8. Key Learnings • Historic insensitivity to blowdown spills • Lack of knowledge of State groundwater regulations • Exelon functional area gaps for radiological spills • IEPA sensitivity to “Right to Know” • Issues management process

  9. Description of Sites • Areas for focused site characterization reports • Areas near VB 1 and VBs 2,3 • VB 4 • VB 6 • VB 7 • West side of turbine building • Other areas investigated - no tritium identified • Blowdown line between VB 1 and 3 • River screen house (past VB 11)

  10. Regional Geology

  11. Sampling and Analysis Locations

  12. Additional Studies • Comprehensive water level measurements • Area wide well inventory • Review release logs to estimate curies released from VB leaks • Tritium dating study in VB 2,3 plume area • Chemical analysis of groundwater/blowdown water • Pipe integrity test • Modeling of transport

  13. Regional Groundwater Use • Wells are screened as follows • Shallow aquifer (25-30 feet) • Private wells • Shallow bedrock (80-100 feet) • Private wells • Deeper bedrock (600-700 feet) • Some private wells • Municipal wells • Deepest bedrock (1400-1600 feet) • Municipal wells

  14. Key Conclusions • Tritium in groundwater is consistent with historical releases from VBs • Migration will not result in impact on private wells above the groundwater standard • Additional conclusions and observations VB-1 VB 2-3 VB-4,6,7

  15. VB 2,3 • Objectives • Prevent migration into uncontaminated areas • Recover contaminated groundwater • Use a method that can be implemented quickly, with already licensed and permitted disposal methods • Currently pumping from pond on Exelon property (Exelon Pond) • Most immediate effect on northward migration • Will supplement this action with additional remediation actions based on modeling

  16. Exelon Pond Pumping System

  17. Blowdown Line Integrity • Operate line water solid • Sealed bottom of VB vaults • Installed continuous leak detection system • Hydraulic transient analysis of line • Weekly inspections of blowdown line corridor

  18. Action to Suppress VB-1 Plume • VB-1 plume is leaching into site perimeter ditch • Installed temporary weir in ditch to raise level of surface water • Installed in 3/06 • Stop partially penetrating influence of ditch • Result - slow downward trend in sample results at weir • Removed in fall of 2006 after successful implementation of remediation system • Installed remediation system consisting of 3 wells.

  19. Dose Assessment • Performed by independent three member team with significant industry experience • Independent review – Dr. John W Poston • Methodology highlights • Multiple exposure pathways considered • Results include past, current, and hypothetical future dose • Methodology consistent with Regulatory Guide 1.109 (1977) • Volumes and concentrations released based on plant release logs and soil samples

  20. VB-2, VB-3 Related Scenarios • Private Well 8 Potable Water • Well Drinking Water • Garden Irrigated with Well • Exelon Pond • Swimming • Eating Fish Living In Pond • Eating Deer Drinking From Pond • Eating Goose Drinking from Pond • Smiley Ditch VB-2, VB-3 • Eating Deer Drinking from Smiley Road Ditch • Direct Dose from Smiley Road Ditch • Spill Water at VB-3 • Deer drinking water eating contaminated vegetation

  21. VB-3 Multiple Nuclide Scenarios • Deer drinking ponded spill water, eating contaminated vegetation around vacuum breaker pit. • Direct shine to members of public on Smiley Road from potential soil contamination in ditch. • No direct sample data from 1998 spill • Soil sample data from 2001 50.75 (g) available • Tank release data from 1998

  22. Summary of Calculated Doses

  23. Root Cause Analysis • Responses to spills varied; none were adequate • 1996 and 1998 spills treated as water spills; no sampling or cleanup • 2000 spill was sampled and cleaned up; no consideration of impact on ground water • Root cause is lack of integrated procedural guidance • Environmental spill response procedures not intended for radioactive spills • Radiological documentation procedure does not consider impacts on groundwater, hydrology, groundwater regulations • Additional root cause is lack of management oversight • Review of condition reports • Inadequate follow-through for 2000 spill

  24. Root Cause Corrective Actions • Develop integrated spill response procedure • Develop methodology for future releases • Increase rigor in issues management process • Case study for management aspects • Other actions address training, procedure enhancements • Previous actions to prevent catastrophic VB failures • Appear effective based on performance since 2000 • Did not address small VB leaks • Action to consider alternate methods for releases

  25. Release Reduction • Recycle modifications • Clean up radwaste to primary grade water • Reverse osmosis/demineralizers • Use existing primary water storage tanks • Volume reduction modifications • Condensate re-route (chillers and aux steam) • Floor drain re-route (reduces organic input) • Reduction of over 1M gal/year input to radwaste • Long-term optimization • Production • Recycle • Release (electrolysis, liquid release)