Decommissioning Overview and Alpha Contamination Hazards at Connecticut Yankee · 2007-03-12 ·...
Transcript of Decommissioning Overview and Alpha Contamination Hazards at Connecticut Yankee · 2007-03-12 ·...
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Decommissioning Overview and Decommissioning Overview and Alpha Contamination Hazards at Alpha Contamination Hazards at
Connecticut YankeeConnecticut YankeeNorth Carolina ChapterHealth Physics Society
February 22, 2007
Jay Tarzia, CHPRadiation Safety & Control Services, Inc.
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OutlineOutline• Connecticut Yankee History• Connecticut Yankee Decommissioning• Radiological Challenges Encountered
During Decommissioning• Identification and Control of Alpha
Source Term• Lessons Learned
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Connecticut YankeeConnecticut Yankee
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Connecticut Yankee HistoryConnecticut Yankee History• 582-Mwe Pressurized Water Reactor• Construction Period 1963 - 1967• Commercial Operation Jan 1, 1968• Permanently Shut Down December 4, 1996
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Shutdown DecisionShutdown Decision• Regulatory Issues Emerge - Fall 1996• Economic Evaluations Determine Continued
Operation Not in Consumer Interest• Shutdown Decision - December 4, 1996
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Regulatory Issues at Regulatory Issues at ShutdownShutdown
• Design Basis and Licensing Basis Deficiencies• Inadequate Corrective Action Program• Radiation Protection Events Emerging• Low Management Standards and Expectations• Procedure Deficiencies
Clear Indication From Regulator (NRC) That Issues Must Be Resolved Prior To Proceeding With Decommissioning
Resulting Fine May 1997 - $650,000
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Radiation Protection IssuesRadiation Protection Issues• November 1996 Fuel Transfer Canal Exposures
• Breakdown in Radiological Controls• Poor Work Planning, Control, Practices• Failure to Adhere to Fundamental
Radiological Safety• Inadequate Control of Radioactive Material
• Released Video Cables With Low Level Contamination\
• Radiation Monitoring System Inadequacies• Inadequate Calibration Procedures
Confirmatory Action Letter (CAL) Issued in May 1997 by NRC Limiting Work to ONLY Essential Radiological Work Until Program Improved
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RP Improvement ProgramRP Improvement Program• Administrative Controls Put in Place - Only
Essential Work
• Independent Assessment Performed
• Three Phase Improvement Plan Submitted to NRC
• Significant Regulator, Media and Public Interest
• Complete Overhaul of Program - 14 Month Effort
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Historical Site AssessmentHistorical Site Assessment• Identified several historical events leading
to onsite contamination• Spills and Leaks
• RWST• Airborne releases
• Stack Releases 1979• Radioactive system failures• Hazardous material used in
construction
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Offsite ContaminationOffsite Contamination• Historical Site Assessment Identified
the Potential Release of Concrete Shield Blocks to Employees (1975)
• Several Blocks Returned to Site -November 1997
• Over 5100 Blocks
• Contaminated Soil Also Identified
• Condition Not a Public Health or Safety Concern
• NRC Requires Any Detectable Licensed Material Be Recovered
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Offsite MaterialOffsite Material
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Offsite Material Recovery Offsite Material Recovery EffortEffort
• Over 140 Offsite Properties Evaluated
• Over 50 Properties Require Remediation
• Over 5,000 Blocks Located
• Significant Media and Public Interest
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Decommissioning 1997 Decommissioning 1997 • Resolution of Regulatory
Issues – NRC Confirmatory Action Letter (CAL) Issued
• Radiation Monitoring System Improvements and Recalibration
• Began Site Characterization and Historical Assessment
• Began Offsite Contamination and Recovery Efforts
INDICATES AREAS OF THE SITE THAT HAVE BEEN SURVEYED / SAMPLED FOR RADIOACTIVE MATERIALS - NO DETECTABLE ACTIVITY FOUND
INDICATES AREAS OF THE SITE THAT HAVE BEEN SURVEYED / SAMPLED FOR RADIOACTIVE MATERIALS - MEASURABLE ACTIVITY FOUND
INDICATES AREAS OF THE SITE THAT HAVE BEEN SURVEYED USING A SURFACE CONTAMINATION MONITOR
Revision #9 04/16/98
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PONDNo Detectable
Activity
COMMENTS: Areas Evaluated by Scanning, Soil Sampling and Exposure Rate Readings
CONNECTICUT RIVER
SCOPING SURVEY STATUS(1 OF 2)
TRAINING STORES OFF.
PRIMARYAUX. BUILDING
CONTROLROOM
INFORMATIONCENTER
POND
EMER GENCYOPERATIONS
CENTER
WASTEDISPOSAL
TK14- 1A
TK14- 1B
TK- 61 TK4-1 A
TK25- 1A TK
25-1B
SW ITCHGEARBLDG. "B"
TK- 33
FUEL OILTANK
TK- 20 TK- 62
TK- 171A&1B
TK- 63A&B
SPENT RESINSTORAGE
SPENT RESINFACILITY
CONTAINMENTACCESS BLDG.
REACTORCONTAINMENT
MOTO RCYCLEPARKING
PARKING LOT
OVER FLO WPARKIN G LOT
ROAD
RO AD
STEAM G ENERATORMOCKUP BUILDING
BOTTLED GAS STORAGEAREA
SHUT DO WNAUX FEED
PUMP HO USE
UNCON DITIONALRELEASEFACILIT Y
PENETRATION BUILD ING
RADWASTEREDUCTION
FACILITY
115KVSWITCH YARD
ISI &CONTRACTOR
SERVICES
TOOLISSUE
INSULATIONSHOP
FABSHOP
HYDROGENSTORAGE
ION EXCHANGESTR UCTURE
WAREH OUSE#2
WAREH OUSE WAREHOU SE
WAREHOUSE#1
SERVICE BUILDING
BOILERROOM
I&C / OPS
DIESEL
CYENG.
TURBINE BUILDING
ADMIN. BUILDING
MAINT.OFFICE
DISCHARGE CANAL
SEPTICSYSTEM
OFFICE BUILD.PAP
AUX. BAY
SECURITY OFFICE
X
STORM DRAIN DISCHARGE
Avg 15 mR/yr
Tree LineWooded Area
CENTRAL MOUNTAIN SIDE
.34mR/yr
BUS 10 Area
GPR Site STORM DRAINRUNOFF
Avg 11mR/yr
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Decommissioning 1998 Decommissioning 1998 • Completed
Resolution of Regulatory Issues – CAL Lifted
• Full System Decontamination
• BUS 10 Remediation
Group 1 Exposure Rates
0
200
400
600
800
1000
7/24 7/25 7/26 7/27 7/28 7/29 7/30 7/31 8/1 8/2
mR
/hr
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Decommissioning 1999 Decommissioning 1999 • Isolation of Spent
Fuel Island• Transition to a
Decommissioning Operations Contractor (DOC)
• Steam Generator and PressurizerRemoval
IntermediateCoolingPump
SprayCoolingPump
SprayCooler
SurgeTank
SurgeTank
Air,Vapor,Heat
Spray
SprayCooling
Loop
IntermediateCooling
Loop
Spen
t Fue
l Poo
l
Fuel
Spent FuelPool Cooling
Pump
SF Bldg. Roof
Spent FuelPool Cooling
Loop
Fan
Air
Makeup
Vent
RM
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Decommissioning 2000Decommissioning 2000• Reactor Coolant Pump and
Primary Piping Removal• Completion of “Cold and Dark”
Modifications• Asbestos Abatement• Reactor Vessel Internal (Core
Barrel) Segmentation• Transfer of GTCC • Submission of License
Termination Plan to NRC
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Decommissioning 2001Decommissioning 2001
• Reactor Head Segmentation and Disposal
• Cavity Recovery and Garnet Waste Transfer
• Primary Auxiliary Building (PAB) System Structure and Component (SSC) Removals
• Turbine Building System Removals
• Began FSS of Open Land Areas
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DecommissioningDecommissioning 20022002• Waste Disposal
Building (WDB) SSC Removal
• Independent Spent Fuel Storage Installation (ISFSI) Work Begins
• Begin Tank Farm SSC Removal
• Resolution of LTP RAIs
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DecommissioningDecommissioning 20032003• Reactor Cavity Drain
down• Reactor Cavity
Aggressive Decontamination
• Regenerative Heat Exchanger Removal
• Discharge Canal Dredging
• Reactor Vessel Removals
• Remediation of Landfill Area
• Termination of DOC
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DecommissioningDecommissioning 20042004• GTTC and Fuel
Moves• Containment
Commodity Removals
• Mirror Insulation Removal
• Neutron Shield Tank Removal
• Turbine Building Condenser Removal
• Begin Building Demolition
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DecommissioningDecommissioning 20052005• Internal Containment
Demolition• Spent Fuel Pool
Demolition• Underground
Commodity Removal
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DecommissioningDecommissioning 20062006• Containment Dome
Demolition• Discharge Canal
Restoration• Warehouse /
Outbuilding Demolition
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July 2003July 2003
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March 2005March 2005
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August 2005August 2005
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January 2007January 2007
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Radiological Challenges During Radiological Challenges During DecommissioningDecommissioning
• High Dose Rate Components and Systems
• Waste Classification and Packaging• Contaminated Soil and Groundwater• Significant Transuranic Source Term
• Potential for High Intakes• Release of Material Issues
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History of TRU Contamination at History of TRU Contamination at CYCY
• Operational Fuel Leakage• Significant in 1979 and
1989• Loss of Cavity Incident –
1984• Operational Tank and
Valve Leakage• Operational Spills• Chemical
Decontamination Events
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Regulatory and Stakeholder Regulatory and Stakeholder Interest in TRUInterest in TRU
• Heightened Sensitivity by NRC and Community Due to Past Plant Events• Transfer Canal Exposure Incident -
1996• Confirmatory Action Letter – 1997• Offsite Contamination Discovery –
1997• NRC Historical Site Review
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Typical Fission/Activation MixTypical Fission/Activation Mix• Large Variation• ETD Isotopes
• Co-60• Cs-137• Eu-
154/155/152• HTD Isotopes
• Most TRUs• Ni-63, Fe-55,
Sr-90
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Beta / Alpha RatiosBeta / Alpha Ratios• Containment
General Areas• 500/1 to 100 to 1
• PAB, WDB General Areas• 100/1 to 10 to 1
• RHR Pit, Pipe Trenches, Internal Systems• 50/1 to 1/1
• Most Plants • >10,000/1
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Alpha Contamination LevelsAlpha Contamination Levels
• Containment• Non-Detectable to 30,000 dpm / 100
cm2
• PAB, RHR Pit, Pipe Trenches• 200 to 100,000 dpm / 100 cm2
• Internal Systems• Up to 1,000,000 dpm / 100 cm2
TP-33
Airborne Radioactivity during Airborne Radioactivity during DecommissioningDecommissioning• Generated from:
• Work in Contaminated Areas• Dismantling Systems and
Components• Ratios Can Be Inconsistent and
Unpredictable• Usually Instantaneous or Short
Duration• Chronic Occupied Particulate Airborne
Levels are Rare
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Alpha Contamination Hazards Alpha Contamination Hazards During Decommissioning at CYDuring Decommissioning at CY
• Small Amount Lead to Very High Internal Doses• 13,200,000 dpm Co-60 = 1 rem• 2,640 dpm Am-241 = 1 rem
• Difficult to Detect in People • WBC does not detect Alpha
contamination• > 500 mrem Intakes Can be Missed by
WBC Due to Low Beta / Alpha Ratios• Detection Challenged by Radon
• Relatively High• Changes with weather, time, location.
Fecal Bioassays Assumed Inahlation Intake of .559 nCi, A
1E-04
1E-03
1E-02
1E-01
1E+00
0 2 4 6 8 10Time Post Intake, Days
nCi/d
ay
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Annual Limit on Intake, ALIAnnual Limit on Intake, ALI
• Listed in 10CFR20 for each Isotope for Inhalation or Ingestion
• Represents a Quantity of Radioactive Material, uCi.
• Results in Annual Dose Limit if Inhaled or Ingested For the Assumptions Used:
• Particle Size• Breathing Rates• Metabolism of “Reference Man”
• 1 ALI = 5 rem CEDE or 50 rem CDE
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Comparison of Alpha RisksComparison of Alpha RisksIsotope Half
LifeIngestionALI, uCi
InhalationALI, uCi
Np-237 2,140,000 y 0.5 .004Pu-238 88 y 0.9 .007Pu-239 24,131 y 0.8 .006Am-241 432 y 0.8 .006Rn-222 3.8 d None 10,000Rn-222
with daughters 3.8 d None 100Co-60 5.26 y 200 30Cs-137 30 y 100 200Mn-54 313 d 2000 800
Beta/Alpha Ratio for Co-60 & Am-241 = 30 ÷ 0.006 = 5,000
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Relative Internal Dose Potential For CoRelative Internal Dose Potential For Co--60 60 and Amand Am--241 Versus Beta: Alpha Ratio 241 Versus Beta: Alpha Ratio
1
10
100
1000
10 100 1000 10000 10000Beta to Alpha Ratio
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Internal Dose Assessment and Internal Dose Assessment and Control at CYControl at CY• Identification and Control of Potential
Internal Source Term Hazards• Characterization• Area Controls
• Identification of Potential Intakes• Follow-up Intake Assessments• Data Analysis and Assignment of Dose
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Identification of Potential IntakesIdentification of Potential Intakes
• Personnel Contaminations• Focus on Facial Area
• Positive Random WBC• Unexpected Positive
General Area Air Samples• CAM Alarms• Positive Lapel Air Sample
Results
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Area Controls for Area Controls for ““Alpha AreasAlpha Areas””at CYat CY
• Minimal Risk Areas:• < 200 dpm/100 cm2
• General RWPs
• Low Risk Areas• 200 – 1000 dpm/100 cm2
• Specific – 1 RWPs
• High Risk Areas• >1000 dpm/100 cm2 or Beta/Alpha
Ratios < 50/1• Specific – 2 RWPs
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Internal Dose Protection Internal Dose Protection MeasuresMeasures
• Minimize Sources• Use engineering
controls• Ventilation• Water
• Protective Clothing• Respirators
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Internal Hazard MonitoringInternal Hazard Monitoring• Contamination Levels
• Ingestion hazard• May Be A Source for
Airborne• Do Good Surveys!
• Airborne Radioactivity Levels• Inhalation hazard• Do Good Air sampling!
• General Area• Personal
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Relative Internal Dose Potential For CoRelative Internal Dose Potential For Co--60 60 and Amand Am--241 Versus Beta: Alpha Ratio 241 Versus Beta: Alpha Ratio
1
10
100
1000
10 100 1000 10000 1000Beta to Alpha Ratio
TP-44
Alpha Contamination Alpha Contamination MonitoringMonitoring
• Low MDAs Required for release• Fixed Contamination: 100 dpm/100
sq cm• Removable Contamination: 20
dpm/100 sq cm
• “Low” plant contamination levels can lead to high airborne activity levels depending on ratios.
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Alpha Airborne MonitoringAlpha Airborne Monitoring
• Critical to assess intakes (or lack of)• Radon Interference causes
challenges• Other monitoring concerns
• Depth of burial• cross contamination
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General Area Air SamplesGeneral Area Air Samples
• Used to assess peak values• Used to determine posting
requirements• May not be representative
enough for personnel intake assessment
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Personal (Lapel) Air SamplingPersonal (Lapel) Air Sampling
• Key Part of Program• Used as an Indicator for
Potential Intakes• True Breathing Zone
Samplers• Not good for measuring
DAC for posting• Great for measuring
“INTAKE”• Can be used as
“INTAKE DOSIMETERS”
TP-48
Lapel Air Sampler Intake Lapel Air Sampler Intake AssessmentAssessment• Reference Man breaths 1200 lph
(working)• Lapel Air Sampler flow rate = 2 lpm =
120 lph• Ratio of Reference Man to Lapel =
10:1• The INTAKE of the worker = 10 *
Lapel Activity
TP-49
CY Internal Dosimetry CY Internal Dosimetry ProgramProgram• Lapel Air Sampling• G/A Air Sampling• WBC Initiation Events• WBC Action Levels• In-Vitro Sampling
• Initiation for Urine and Fecal Sampling• Process Flow for Information Flow
• Random Bioassay Selection• Internal Dosimetry Assessment Process
TP-50
Lessons LearnedLessons Learned
TP-51
Events Leading to Significant Events Leading to Significant Alpha ContaminationAlpha Contamination
• Extended Operations with Significant Fuel Leakage
• Operational Spills• Long-term Valve and Component
Leakage
TP-52
Prevention of LongPrevention of Long--Term Alpha Term Alpha EffectsEffects
• Aggressive Cleanup and Documentation of Spills• 10CFR50.75g file
• Good Component Maintenance• Limitations and Evaluations of
Operating when Fuel Leakage is Detected
• Aggressive Routine Plant Decontamination
TP-53
Benefits of Using Lapel Air Benefits of Using Lapel Air SamplersSamplers
• More Representative than General Area Samples
• Excellent Sensitivity to Alpha Intakes• Rapid Indication of Potential Intakes
• Generally Conservative for Inhalation Intakes• Easy to Use
• No need to track on/off times• No need to calculate air volume• Just know who it belongs to and don’t lose it!
• Provides “Negative” Documentation• Worker and Public Trust
TP-54
The EndThe EndQuestions?