Modeling the Effects of a Radiological Dispersion Device
DetonationTragan Knight and Nathaniel Tidwell
Dr. Melanie Sattler, P.E.Dr. Yvette Weatherton, P.E.
Roja Haritha Gangupomu
Nathaniel TidwellCompleted first year at North Central Texas
CollegeAttending University of Texas Arlington as a
sophomoreMajoring in Mechanical Engineering
Tragan KnightEastfield CollegeUniversity of Texas at ArlingtonMajor: Civil Engineering (Environmental
Engineer)Goals: Master (Material in Science) Ph.D.:
(Theology)Aspirations: Reevaluate and innovate the
recycling process.
ObjectivesModel the effects of a dirty bomb detonation
at Cotton Bowl Stadium in Dallas, TexasUse the HotSpot air dispersion model to run
simulationsCompare different radionuclides, as well as
various atmospheric conditions
Radiological Dispersion DevicesAlso known as RDDs, or “dirty bombs”Use conventional explosives to spread
radioactive material over an areaAlthough there is concern that terrorist
groups may use dirty bombs, so far none have actually been detonated.
RadionuclidesIsotopes that undergo radioactive decaySeveral types of radionuclides are used in
medicine and industryWe used three different radionuclides in our
simulations: 241Am, 137Cs, and 60Co
This backscatter gauge, used in
industry, contains 137Cs.1
1 Nitus Gamma Backscatter Gauge. Digital image. ThermoScientific.com. Thermo Fisher Scientific Inc., n.d. Web. 23 July 2012.
RadiationThree types of radioactive decay
Alpha Helium nucleus (alpha particle) is emitted from an
atom Most harmful, but least penetrating
Beta Electron or positron (beta particle) is emitted Moderate harm, and moderate penetration
Gamma Gamma rays are emitted Least harmful, but highly penetrating
Total Effective Dose EquivalentSum of external and internal effective dose
equivalentsUnit of measure is the Sievert (Sv) or
roentgen equivalent in man (rem) for biological tissue1 Sv = 100 rems
Biological Effects of RadiationEffect Dose
Blood count changes 50 rem
Vomiting (threshold) 100 rem
Mortality (threshold) 150 rem
LD50/60* (with minimal
supportive care)320 – 360 rem
LD50/60 (with supportive medical treatment)
480 – 540 rem
100% mortality (with best available
treatment)
800 rem
* The LD50/60 is that dose at which 50%of the exposed population will die within 60 days.
1"Biological Effects of Ionizing Radiation." Princeton.edu. Trustees of Princeton University, 30 Apr. 2010. Web. 26 July 2012.
1
Air Dispersion ModelingOften used to predict downwind
concentrations of pollutants, especially from smokestacks
We used HotSpot to model an RDD detonation, which uses the Gaussian Plume Model.
Plume Model
HotSpot 2.07.2Created by National Atmospheric Release
Advisory Center (NARAC)A computer program designed to calculate
radiation dosesUses the Gaussian EquationProvides numerous amounts of potential
radiological dispersal devices scenariosUsed for short-term, short-range (up to 10
km) simulations
HotSpot 2.07.2Relatively simple surroundings data
Built-in standard terrain informationOne meteorological condition per run
Less sophisticated than other air dispersion models
Parameters
Radionuclide Stability Class Rainfall241Am B Rain137Cs D No Rain60Co F
Mixture
Variables
4 radionuclides * 3 stability classes * 2 rainfall conditions = 24 runs
Other ParametersMaterial-at-Risk 100 grams
High Explosives 100 pounds TNT equivalent
Wind Speed 4.8 m/s
Wind Direction 180° (from the south)
Rainfall Rate 5 mm/hr
Terrain city
Running SimulationsHotSpot is very user-friendlyIt takes only a couple minutes to input terms
and view results
Examples of Outputs
Results
Inputs and Outputs from Hotspot.
ResultsComparing differences in stability classes with 241Am
B D F
ResultsThe figures below compare rainout and dry
conditions using 60Co and stability class B. No Rain Rain
ResultsComparing
each isotope in dry conditions with stability class B
(a) 241Am(b) 137Cs(c) 60Co(d) Mixture
A
DC
B
Conclusions
60 Co generally had the highest TEDE137 Cs generally had the lowest TEDERadiation doses are higher in scenarios with
rainStability Class F had the largest isopleth area
of sickness in all scenariosWorst-case scenario is 60Co, stability class F,
in rainy conditions
Thank You!