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1 Braidwood Generating Station Tritium Review Presentation to RETS/REMP Workshop June 26, 2007.

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Presentation on theme: "1 Braidwood Generating Station Tritium Review Presentation to RETS/REMP Workshop June 26, 2007."— Presentation transcript:

1 1 Braidwood Generating Station Tritium Review Presentation to RETS/REMP Workshop June 26, 2007

2 2 Dual-unit Westinghouse pressurized water reactors Construction permitDecember 1975 Unit One operationJuly 1988 Unit Two operationOctober 1988 (Initial operating licenses good for 40 years) Generation capabilityUnit 1 – 1248 MWe Unit 2 – 1224 MWe Number of employees615 (Exelon) Braidwood Station Background

3 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 4 Circulating Water Blowdown Line

5 5 Chronology Three significant VB leaks –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 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 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 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 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 10 Regional Geology

11 11 Sampling and Analysis Locations

12 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 13 Regional Groundwater Use Wells are screened as follows –Shallow aquifer (25-30 feet) Private wells –Shallow bedrock ( feet) Private wells –Deeper bedrock ( feet) Some private wells Municipal wells –Deepest bedrock ( feet) Municipal wells

14 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-1VB 2-3 VB-4,6,7

15 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 16 Exelon Pond Pumping System

17 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 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 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 (1977) –Volumes and concentrations released based on plant release logs and soil samples

20 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 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 (g) available –Tank release data from 1998

22 22 Summary of Calculated Doses

23 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 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 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)


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