Air Dispersion Modeling:Planning for Airborne Terrorism

Release

Tiffany LeBlanc Gerald GruberREU Program

University of Texas at Arlington

Outline

Objective Hotspot Software Gaussian Dispersion Equation Meteorology Effects: Wind and Air

Stability Scenarios Modeling Results Conclusion

REU Objective

The objective of this project was to create a scenario portraying a nuclear terrorist attack using the software HotSpot. This software evaluates and models how a pollutant disperses into the atmosphere depending on certain variables.

Hotspot

The HotSpot program provides approximation of the radiation effects associated with the atmospheric release of radioactive materials.

Short term accidents or releases

Gaussian Dispersion Equation

C  =  Downwind concentration, µg/m3

Q  =  Pollution source emission rate, µg/su  =  Average wind speed, m/sσy  =  y direction plume standard deviation, mσz  =  z direction plume standard deviation, m

x  =  Position in the x direction or downwind direction, m

y  =  Position in the y direction, mz  =  Position in the z direction, mH  =  Effective stack height, m

Gaussian Dispersion Equation

Air Stability

Turbulent dispersion causes the pollutant concentrations to disperse away from the mean flow.

What are the categories of air stability?› A = Very Unstable› B = Moderately Unstable› C = Slightly Unstable› D = Neutral› E = Slightly Stable› F = Stable

Air Stability How do you determine air stability?

Wind

What causes changes in wind flow? Wind is summarized with direction and

velocity. Urban vs. Rural Environments

› Urban environments produce more wind friction than rural environments.

› Concentration is inversely proportional to wind speed.

Scenario

There is a terrorist attack outside the stadium of the 2012 Super Bowl releasing Plutonium-238.

Variables:› Wind speed (2 m/s,

12m/s)› Air Stability (Category

A and F)› Amount of explosive

(Backpack 20 lbs., Car 200 lbs.)

http://www.stadiumsofprofootball.com/afc/LucasOilStadium.htm, 2006

Plutonium-238 Why Plutonium- 238? Health effects of Plutonium-238 What is MAR? (Materials at Risk)

http://www.clarku.edu/departments/marsh/projects/community/plutonium.pdf, 2002http://news.discovery.com/space/as-nasas-plutonium-supply-dwindles-esa-eyes-nuclear-energy-program.htm, 2010

Scenario

Backpack Scenario› MAR 2,000 Ci of Plutonium-238› Urban environment› 2 m/s and 12 m/s wind speed from the South› Air Stability Category A and F› 20 lbs. of explosive

Car Scenario› MAR 2,000 Ci of Plutonium-238› Urban environment› 2 m/s and 12 m/s wind speed from the South› Air Stability Category A and F› 200 lbs. of explosive

Methods using HotSpotStep 1: Models

Methods using HotSpotStep 2: Source Term

Methods using HotSpotStep 3: Meteorology

Methods using HotSpotStep 4: Output

Using Google Earth: Plotting our source

Modeling- Backpack Category F 2 m/s

Modeling- Backpack Category F 2 m/s

Table Output

Results

Modeling-Car Category F 12 m/s

Table 1: Total Results

 Scenario Stabilit

y ClassWind Speed(m/s)

Lbs of explosive

MAR(Curies)

Area of 1000 rem isopleths(km2)

Backpack A 2 20 2,000 0.076

Backpack A 12 20 2,000 0.019

Backpack F 2 20 2,000 0.14

Backpack F 12 20 2,000 0.017

Car A 2 200 2,000 0.037

Car A 12 200 2,000 0.015

Car F 2 200 2,000 0.046

Car F 12 200 2,000 0.008

Conclusion

By changing the variables, we were able to model the most devastating scenario. The variables that caused the most destruction were wind speed at 2 m/s in a stable environment and a lower amount of explosive. This evidence supports all of the background information we learned about Air Dispersion before we modeled our scenarios.

Sources

Cooper, C. David., and F. C. Alley. "Chapter 20 Atmospheric Dispersion Modeling." Air Pollution Control: a Design Approach. Third ed. Prospect Heights, IL: Waveland, 2002. 607-48. Print.

Burns, Casey. Overview of Plutonium and Its Health Effects (2002): 6-9. Web. 07 July 2011. <http://www.clarku.edu/departments/marsh/projects/community/plutonium.pdf>.

Homann, Steven G. HotSpot. Computer software. National Atmospheric Release Advisory Center (NARAC). Vers. 2.07.1. 2 Mar. 2010. Web. <https://narac.llnl.gov/HotSpot/HotSpot.html>.

Lucas Oil Stadium. Photograph. Indianapolis. Stadiums of Pro Football. Web. 13 July 2011. <http://www.stadiumsofprofootball.com/afc/LucasOilStadium.htm>.

O'Neil, Ian. "As NASA's Plutonium Supply Dwindles, ESA Eyes Nuclear Energy Program : Discovery News." Discovery News: Earth, Space, Tech, Animals, History, Adventure, Human, Autos. Spaceflight Now, 09 July 2010. Web. 07 July 2011. <http://news.discovery.com/space/as-nasas-plutonium-supply-dwindles-esa-eyes-nuclear-energy-program.html>.

 "Radiation Risk and Realities." United States Environmental Protection Agency. May 2007. Web. 4 July 2011. <http://www.epa.gov/rpdweb00/docs/402-k-07-006.pdf>.