Modeling the Effects of a Radiological Dispersion Device Detonation

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

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

3. 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.

4. 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

5. 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.

6. 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 1Nitus Gamma Backscatter Gauge. Digital image. ThermoScientific.com. Thermo Fisher Scientific Inc., n.d. Web. 23 July 2012.

7. Radiation • Three 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

8. 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

9. Biological Effects of Radiation 1 * 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.

10. 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.

11. Plume Model

12. 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

13. 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

14. Parameters Variables 4 radionuclides * 3 stability classes * 2 rainfall conditions = 24 runs

15. Other Parameters

16. Running Simulations • HotSpot is very user-friendly • It takes only a couple minutes to input terms and view results

17. Examples of Outputs

18. Results Inputs and Outputs from Hotspot.

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

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

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

22. 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

23. Thank You!