Nuclear Terrorism Preparedness Working Group

The effects of nuclear terrorism

Carolyn (Cari) Seifert (carolyn.seifert@pnnl.gov), Chair
James Fyffe
C. M. Wood
Sam Keith
Jason Cezeaux
C. Davis Lovell
John Lanza

Dispersion of radioactive materials can be accomplished by terrorist organizations using several methods. One of these methods is a dirty bomb and another is an improvised nuclear device or weapon. Dirty bombs are the dispersion of radioactive material associated with a conventional explosion device (or other means) the effects of which are described under Radiological Dispersive Devices. An improvised nuclear device or weapon is detonation of a thermonuclear device. Additional definitions of terms can be found in the Weapons of Mass Destruction Factsheet

One of the primary lines of defense against detonation of a nuclear device is interdiction. Interdiction is the use of methods and strategies that reduce the potential for the smuggling or illicit procession of a nuclear device as discussed on the Interdiction page. In addition, tighter controls of radioactive materials make it more difficult for the material to be stolen or diverted into terrorist uses. Interdiction relies heavily on intelligence gathering and other methods of determining the intent, tactics, and behaviors of terrorist groups attempting to utilize radiological or nuclear weapons. Members of the Society believe that detonation of a nuclear weapon is highly unlikely, nevertheless, the presentation The Effects of Nuclear Weapons provides additional information describing the mechanisms and effects of nuclear weapons. Nuclear weapons have four main destructive effects:

Blast, Thermal Energy, Initial nuclear radiation, and Fallout

Blast
The rapid release of energy in an explosion creates a shock wave of overpressure. Very close to the centre of a nuclear explosion, overpressure is equivalent to several thousand pounds per square inch (psi).

Thermal Radiation
Thermal radiation includes light and heat. Nuclear weapons release a huge amount of energy as light (ultraviolet, visible and infrared). The heat at the centre of the explosion (epicenter) is sufficiently intense to vaporize most materials. The thermal radiation creates a fireball which expands rapidly outwards consuming oxygen and, combined with the blast effect, creating near total destruction for some distance from the epicenter.

Initial nuclear radiation
Initial radiation consists mostly of gamma rays and neutrons which are generated in the nuclear reaction.

Fallout
Fallout consists of large numbers of particles, from the earth, buildings and other ground objects, which are irradiated by the explosion, mixing with the radioactive products of the explosion itself and then being distributed over a wide area by wind.

Extent of damage
The extent of damage depends on the size of the nuclear weapon, the terrain and the height at which it is detonated. Nuclear weapons detonated at ground level generate more fallout as a result of the large amount of ground material which is irradiated by the explosion and thrown in the air, but the effects of thermal radiation and radioactive waves is less than in an air blast. The nuclear weapon detonated in Hiroshima was about 12kt, i.e. the equivalent of 15,000 tons of TNT and resulted in 80,000 deaths. Nearly all deaths were due to blast and thermal effects. Current nuclear weapons range in size from 1 kt to over 1000 kt.

Within the closest 500 yards to the detonation of a one KT device, there will be radioactive bomb debris and activation products. Emergency personnel should be scheduled for short entries during the first day, the permitted exposures depending on the urgency of the need for their entry. Further information may be found on the First Response page, and the documents Guidance for Protective Action following a Radiological Terrorist Event and Background Information for the guidance.

Consideration of much bigger bombs leads to a different set of factors. A nuclear device detonated near the center of a metropolitan area could essentially destroy an area encompassed by a ten-mile radius. Blast damage would be significant to 20 miles and thermal flash burns even farther. In addition, fallout in the downwind direction would be in the tens of R/Hr for at least a hundred miles as shown in Nuclear Fallout. Evacuation and /or shielding of personnel and animals would be required.

Additional information related to the detonation of a nuclear bomb and associated issues can be found in Effects of Nuclear Weapons.

References

Planning Guidance for Response to a Nuclear Detonation Developed by the Homeland Security Council Interagency Policy Coordination Subcommittee for Preparedness & Repsonse to Radiological and Nuclear Threats.