TP-1 Decommissioning Overview and Decommissioning Overview and Alpha Contamination Hazards at Alpha Contamination Hazards at Connecticut Yankee Connecticut Yankee North Carolina Chapter Health Physics Society February 22, 2007 Jay Tarzia, CHP Radiation Safety & Control Services, Inc.
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Decommissioning Overview and Alpha Contamination Hazards at Connecticut Yankee · 2007-03-12 · Alpha Contamination Hazards During Decommissioning at CY • Small Amount Lead to
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TP-1
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.
During Decommissioning• Identification and Control of Alpha
Source Term• Lessons Learned
TP-3
Connecticut YankeeConnecticut Yankee
TP-4
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
TP-5
Shutdown DecisionShutdown Decision• Regulatory Issues Emerge - Fall 1996• Economic Evaluations Determine Continued
Operation Not in Consumer Interest• Shutdown Decision - December 4, 1996
TP-6
Regulatory Issues at Regulatory Issues at ShutdownShutdown
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
TP-34
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
TP-35
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
TP-36
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
TP-37
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
TP-38
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
TP-39
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
TP-40
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
• Airborne Radioactivity Levels• Inhalation hazard• Do Good Air sampling!
• General Area• Personal
TP-43
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