Adverse Effects of Nuclear Explosions

Health effects of nuclear explosions are due primarily to air blast, thermal radiation, initial nuclear radiation, and residual nuclear radiation or fallout.

Blast : Nuclear explosions produce air-blast effects similar to those produced by conventional explosives. The shock wave can directly injure humans by rupturing eardrums or lungs or by hurling people at high speed, but most casualties occur because of collapsing structures and flying debris.

Thermal radiation : Unlike conventional explosions, a single nuclear explosion can generate an intense pulse of thermal radiation that can start fires and burn skin over large areas. In some cases, the fires ignited by the explosion can coalesce into a firestorm, preventing the escape of survivors. Though difficult to predict accurately, it is expected that thermal effects from a nuclear explosion would be the cause of significant casualties.

Initial radiation : Nuclear detonations release large amounts of neutron and gamma radiation. Relative to other effects, initial radiation is an important cause of casualties only for low-yield explosions (less than 10 kilotons).

Fallout : When a nuclear detonation occurs close to the ground surface, soil mixes with the highly radioactive fission products from the weapon. The debris is carried by the wind and falls back to Earth over a period of minutes to hours.

The first three of these effects are “prompt” effects, because the harm is inflicted immediately after the detonation. 

Thermal Radiation from Underground Bursts :

Thermal radiation may make fire a collateral effect of the use of surface burst, airburst, or shallow-penetrating nuclear weapons. The potential for fire damage depends on the nature of the burst and the surroundings. If there is a fireball, fires will be a direct result of the absorption of thermal radiation. Fires can also result as an indirect effect of the destruction caused by a blast wave, which can, for example, upset stoves and furnaces, rupture gas lines, and so on. A shallow-penetrating nuclear weapon of, say, 100 to 300 kilotons at a 3 to 5 meter depth of burst will generate a substantial fireball that will not fade as fast as the air blast.

Detonation of a nuclear weapon in a forested area virtually guarantees fire damage at ranges greater than the range of air-blast damage. If the burst is in a city environment where buildings are closely spaced, say less than 10 to 15 meters, fires will spread from burning buildings to adjacent ones. In Germany and Japan in World War II, safe separation distance ranged from about 30 to 50 feet (for a 50 percent probability of spread), but for modern urban areas this distance could be larger. This type of damage is less likely to occur in suburban areas where buildings are more widely separated. Once started, fire spread continues until the fire runs out of fuel or until the distance to the next source of fuel is too great. Thus, fire caused directly by thermal ignitions, fire caused indirectly by disruptive blast waves, and spread of fire are all potential, but uncertain, effects. 


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