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 remVomiting (threshold) 100 remMortality (threshold) 150 remLD50/60

* (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

Conclusions60 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!