2. The Effects of Nuclear Weapons: Terrorist Threat

3. Purpose The purpose of this presentation is to provide the reader with an overview of nuclear weapons and their effects. Topics will include: –Types of weapons –Energy release –Types of Detonation –Historical Information –Effects

4. Nuclear Weapons vs Radioactive Dispersal Device (RDD or Dirty Bomb) Nuclear weapons –Use conventional explosives to create super-critical mass of fissionable nuclear material –Super-critical mass is capable of self-sustaining, prompt, uncontrolled chain reaction –Resultant explosive yield can be orders of magnitude higher than possible with conventional materials RDD –Use conventional explosives to spread or disperse radioactive material –No chain reaction or nuclear yield –In most cases the explosion will cause more damage than the radioactive material dispersion

5. Remaining discussion The remainder of this presentation describes nuclear weapons For further information on RDD weapons see: –http://www.bt.cdc.gov/radiation/pdf/dirty bombs.pdfhttp://www.bt.cdc.gov/radiation/pdf/dirty bombs.pdf –http://www.nrc.gov/reading-rm/doc- collections/fact-sheets/dirty-bombs.pdf

6. Nuclear Weapons Types Fission devices –Uranium ( 235 U) or Plutonium ( 239 Pu) –Gun Type Explosively combine two sub-critical assemblies –Implosion Type Symmetrically implode a sphere of sub-critical density Required for 239 Pu –Terrorist Threat Stolen military device Improvised Nuclear Device (IND), i.e. “home made” 235 U Gun-type Weapon easiest to construct Likely 20 kT or less

7. Nuclear Weapons Types, con’t. Thermonuclear (Fusion) devices –Unlikely to be a terrorist device –Military application –High-technology

8. Energy Equivalents of one Kiloton of TNT Complete burn-up (fission) of 56 g (~2 ounces) of 235 U or 239 Pu 1.15 x 10 6 kilowatt-hours 1.8 x 10 9 British thermal units 14,500 Gallons of Gasoline 4/5 the energy produced by the Hoover Dam in 1 hour

9. Types of Detonations from a Terrorist Threat Most likely –Surface: Truck –Underwater: Boat Less likely –Air: Private plane –Sub-surface: Subway Least likely –High Altitude: Military Delivery Only

10. Distribution of Energy of an Air Burst below 100,000 ft Blast and Thermal account for 85% of the Energy released

11. Nuclear Weapon Experience Two non-testing detonations Hiroshima –Little Boy – 235 U Gun-Type Device Nagasaki –Fat Man – 239 Pu Implosion Device

12. Results of a Nuclear Explosion 80,000 deaths in Hiroshima and 20,000 deaths in Nagasaki Nearly all deaths due to Blast and Thermal Few deaths attributed to Radiation –Prompt or Delayed

13. Results of a Nuclear Explosion Expect few, if any, survivors near ground- zero However, little experience in “urban” environment Buildings will provide shielding –Blast –Thermal –Radiation Residual radioactive environment, significant impact on rescue operations

14. Hiroshima Before Hiroshima After

15. Weapon Effects Prompt effects higher with airburst –Blast –Thermal –Prompt Radiation –Prompt effects 30-50% reduced with surface burst –Electromagnetic Pulse (EMP) Primarily results from a high-altitude explosion Not a likely effect from a terrorist detonation Residual effects higher with surface burst –Residual Radioactivity (Fallout)

16. Weapon Effects (Based on a 20 kt low-altitude Airblast) Peak shock wave overpressure –~14 psi @ ¼ mile Thermal energy –~18 cal/cm 2 @ 1 mile Prompt radiation dose –Neutron ~ 0.8 Gy @ 1 mile –  -ray ~ 1.2 Gy @ 1 mile

17. Residual Radiation (Fallout) Difficult to predict impact to a specific area Depends on: –Type of weapon –Type of burst Air Surface –Wind patterns –Terrain Little data for an “Urban” Environment

18. Fallout, con’t. Decay rate: t can be any time unit Average photon energy ~0.7 MeV

19. Summary A terrorist use of a nuclear weapon would most likely involve: – 235 U Gun-type device –Surface detonation –Yield of 20 kt or less The major injuries and effects would be caused by: –Blast and shock –Thermal Rescue efforts pertain mostly to injuries distant from ground zero Radiation protection necessary for rescue of shielded survivors nearer ground zero Little experience with explosion in an “Urban” environment

20. References Glasstone and Dolan, “The Effects of Nuclear Weapons,” Published by US DoD and Energy Research and Development Administration, Washington DC, 1977. Ferguson and Potter, “The Four Faces of Nuclear Terrorism,” Monterey Institute – Center for Nonproliferation Studies, Monterey, CA, 2004. Auxier J, “The Effects of Nuclear Weapons,” Health Physics Summer School, Gaithersburg, MD, July 2004. Public Protection from Nuclear, Chemical and Biological Terrorism, Ed. by Brodsky, Johnson and Goans, Medical Physics Publishing, Madison, WI, 2004.