Modeling the Effects of a Radiological Dispersion Device Detonation Tragan Knight and Nathaniel Tidwell Dr. Melanie Sattler, P.E. Dr. Yvette Weatherton, P.E. Roja Haritha Gangupomu

Nathaniel Tidwell Completed first year at North Central Texas College Attending University of Texas Arlington as a sophomore Majoring in Mechanical Engineering

Tragan Knight Eastfield College University of Texas at Arlington Major: Civil Engineering (Environmental Engineer) Goals: Master (Material in Science) Ph.D.: (Theology) Aspirations: Reevaluate and innovate the recycling process.

Objectives Model the effects of a dirty bomb detonation at Cotton Bowl Stadium in Dallas, Texas Use the HotSpot air dispersion model to run simulations Compare different radionuclides, as well as various atmospheric conditions

Radiological Dispersion Devices Also known as RDDs, or “dirty bombs” Use conventional explosives to spread radioactive material over an area Although there is concern that terrorist groups may use dirty bombs, so far none have actually been detonated.

Radionuclides Isotopes that undergo radioactive decay Several types of radionuclides are used in medicine and industry We 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.

Radiation Three types of radioactive decay Alpha Beta Gamma 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 Equivalent Sum of external and internal effective dose equivalents Unit of measure is the Sievert (Sv) or roentgen equivalent in man (rem) for biological tissue 1 Sv = 100 rems

Biological Effects of Radiation 1 Effect 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.

Air Dispersion Modeling Often used to predict downwind concentrations of pollutants, especially from smokestacks We used HotSpot to model an RDD detonation, which uses the Gaussian Plume Model. 𝐶= 𝑄 2𝜋𝑢 𝜎 𝑦 𝜎 𝑧 exp −𝑦 2 2 𝜎 𝑦 2 exp − 𝑧−𝐻 2 2 𝜎 𝑧 2 + exp − 𝑧+𝐻 2 2 𝜎 𝑧 2

Plume Model

HotSpot 2.07.2 Created by National Atmospheric Release Advisory Center (NARAC) A computer program designed to calculate radiation doses Uses the Gaussian Equation Provides numerous amounts of potential radiological dispersal devices scenarios Used for short-term, short-range (up to 10 km) simulations

HotSpot 2.07.2 Relatively simple surroundings data Built-in standard terrain information One meteorological condition per run Less sophisticated than other air dispersion models

Parameters Variables Radionuclide Stability Class Rainfall 241Am B Rain 137Cs D No Rain 60Co F Mixture 4 radionuclides * 3 stability classes * 2 rainfall conditions = 24 runs

Other Parameters Material-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 Simulations HotSpot is very user-friendly It takes only a couple minutes to input terms and view results

Examples of Outputs

Results Inputs and Outputs from Hotspot.

Results Comparing differences in stability classes with 241Am B D F

Results The figures below compare rainout and dry conditions using 60Co and stability class B. No Rain Rain

Results Comparing each isotope in dry conditions with stability class B (a) 241Am (b) 137Cs (c) 60Co (d) Mixture A B C D

Conclusions 60 Co generally had the highest TEDE 137 Cs generally had the lowest TEDE Radiation doses are higher in scenarios with rain Stability Class F had the largest isopleth area of sickness in all scenarios Worst-case scenario is 60Co, stability class F, in rainy conditions

Thank You!