randahl c. palmer dr. nolan hertel armin ansarihpschapters.org/src/2010/7...randahl c. palmer-...
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Randahl C. PalmerDr. Nolan HertelDr. Armin Ansari
Work funded by the Center for Disease Control and Prevention
through TKCIS
Overview• Motivation• Portal Monitors• Detector Characterization Method• Experimental Procedure• Experimental Data• Monte Carlo N‐Particles Version 5 (MCNP) Models of
Detectors • Theoretical vs. Experimental Comparisons• TPM 903B Portal Monitor Count Rate over 30 Days
Corresponding to 250 mSv• Current and Future Work
Motivation Goal
To identify individuals who have received > 250 mSv of internal contamination via ingestion or inhalation, for the purpose of further testing and treatment during 1stcut screening of the public after a Radiological Dispersal Device (RDD).
Purpose To determine the validity of using portal monitors to achieve the aforementioned goal
End Goal Procedure sheets for the usage of portal monitors
Ingestion
Triage Decision Making
RDDRDDTriage
Contaminated
Clean
Inhalation
Why Portal Monitors? In the event of an RDD a large population is likely to be affected and must be triaged making the following properties of portal monitors valuable
Portable Whole body counters Easy to assemble and operate Readily available Relatively large throughput
TPM ‐903B Portal Monitor
TPM‐903B – Thermo Scientific Transportable portal monitor 2 x BC408 plastic scintillators
Volume 10.6 liters 1.6 mm of lead shielding around 3 sides Energy Range: 60 keV to 2 MeV
Detector Characterization MethodAcquire CPS for Portal Monitors for Point
Source Measurements with Varying PMMA
Attenuations
Model the Detectors Model the Detectors in MCNP in MCNP
& Simulate the Point & Simulate the Point Source MeasurementsSource Measurements
Victim Victim Sent Sent HomeHome
Determine Determine Count Rate Count Rate (CPS) per (CPS) per 250 mSv250 mSv
Internal Internal Contamination Contamination
Procedure Procedure SheetsSheets
Compare MCNP to Compare MCNP to the Experimental the Experimental Measurements Measurements =Scaling Factor =Scaling Factor
(C/E)(C/E)
Use Dose Coefficients Listed in Rad Toolbox
(ICRP 72)
MCNP Models of MIRD and UF’s Voxel
Phantoms
Determine Source Distribution Over Time Via DCAL
Will the Will the Effective Dose Effective Dose
likely Exceed 250 likely Exceed 250 mSv?mSv?
Victim Sent Victim Sent to to Hospital Hospital for further for further screening screening
and possible and possible treatmenttreatment
Assumptions External contamination removed (i.e. changing clothing and showering)
Only to be used as 1st stage of triage of internal contamination
Count rates listed in procedure sheets correspond to an effective dose equivalent of 250 mSv
People with count rates equal to or higher than those listed in the procedure sheet need further evaluation Treatment should be based upon further evaluation
Procedure
Determining Count Rate per 250 mSv
Experimental Data Experimental Measurement 5 positions 13 PMMA thicknesses
~6 mm ‐ ~12 mm
4 sources
Isotope Photon Energy (MeV)
Photon Emission Intensity
Ba-1330.384, 0.356, 0.303, 0.276, 0.081, 0.035,
0.031, 0.030
0.089, 0.622, 0.184, 0.071, 0.338,
0.122, 0.631, 0.341
Co-60 1.332, 1.1730 0.999, 0.999Cs-137 0.662 0.853Na-22 1.275, 0.511 0.999, 1.798
Experimental Data
TPM 903B Count Rate Dependence on Position
MCNP Models of the DetectorsTPM - 903B with slab phantom
(with minimum and maximum attenuation)
TPM Portal Monitor
PMMA Box
PMMA Source Holder
& Source
AluminumFeet
Full Attenuation
Lower Limit of Detection and Energy Cutoff of TPM 903B
TPM 903B Energy Cutoff:60 keV
Table values calculated according to: Knoll, Glenn F. Radiation Table values calculated according to: Knoll, Glenn F. Radiation Detection and Measurements. 3Detection and Measurements. 3rdrd Edition. Pgs94Edition. Pgs94--96, 116.96, 116.
TPM Portal Monitor Lower Limit of DetectionBackground Level at Which Data Was Taken
Background 4985 CPSStandard Deviation 71 CPSLower Limit of Detection (above background) 331 CPSLower Limit of Detection 5316 CPS
Double Background LevelBackground 9970 CPSStandard Deviation 100 CPSLower Limit of Detection (above background) 467 CPSLower Limit of Detection 10437 CPS
Example of TPM 903 B MCNP Output with Energy Cutoff of 60 keV for Cs‐137
Energy Cutoff
TPM 903B MCNP vs. Experiment
TPM 903B Energy Cutoff: 60 keVMCNP/Experimental
TPM 903B Energy Cutoff: 60 keVMCNP/Experimental
TPM 903B Energy Cutoff: 60 keVMCNP/Experimental
TPM 903B Energy Cutoff: 60 keVMCNP/Experimental
TPM 903B Portal Monitor Count Rate Corresponding to 250 mSv Over 30 Days After Uptake
DOE/NRC RDD isotopes of concern:Co‐60, Cs‐137, I‐131 and Ir‐192
ingested & inhaledWith MIRD anthropomorphic stylized phantoms
Anthropomorphic Phantoms
Height(cm)
Mass(kg) BMI Adipose Mass
(kg)
Reference Male 179 73.1 23 11
Reference Female 168 56.5 20 15
Adipose Male 179 93.7 30 22
Adipose Female 168 73.9 26 15
Post-Menopausal Adipose Female 168 85.9 30 27
10-year Androgynous Child 140 32.7 n/a n/a
TPM‐903B (Adult with Inhaled Radioactivity)Basic Operation
Attach aluminum feet to bottom of the PVC pipes. String cables through top PVC pipe and place on
top of the two sides. Connect the portal monitor to AC power or D‐cell
batteries and turn on. Acquire the background count by pressing the
“Start” button and record value. Once background has been acquired data can be
taken. Have the person stand sideways inside the center of the portal monitor facing the display unit.
Depress “Start” button to acquire data. If the alarm goes off, ignore and continue collecting
counts. After a count rate has been obtained, subtract the
background count from the number on the display and compare the result to the proper trigger level.
Example Procedure Sheet
Trigger Levels
Current and Future Work TPM 903B Portal Monitor Count Rate Corresponding to 250 mSv Over 30 Days After Uptake with University of Florida’s Voxel Male Phantom Compare with MIRD Anthropomorphic Stylized Phantoms
MIRD Phantom UF Voxel Phantom
Current and Future WorkCanberra MiniSentry
Verify MiniSentry Data and Determine the Energy Cutoff and its Count Rate Corresponding to 250 mSv Over 30 Days After Uptake
Acknowledgements Dr. Nolan Hertel Dr. Armin Ansari Dr. Eric Burgett Team Hertel Center for Disease Control and Prevention Funding through TKCIS