EFFECTS OF A NUCLEAR EXPLOSION
A nuclear explosion releases energy in three forms: blast and shock - 50 percent: heat - 35
percent: radiation - 15 percent.
The area surrounding the site of the explosion would receive severe damage from tremendous
heat, blast, and shock waves. This area would also be severely irradiated. The size of the
area receiving severe damage would depend on the size of the exploded weapon.
Fallout formation
Any effects in outlying areas would be from radioactive fallout. Fallout is created when a
nuclear weapon explodes on or near the ground. Large amounts of pulverized dirt and rock
are sucked up into the rising fireball. The intense heat in the fireball fuses residual
radioactive atoms to this debris, which becomes radioactive. These particles of radioactive
debris - fallout - may range in size from fine to coarse sand.
Fallout distribution
The radioactive particles are heavier than air, and settle to earth soon after they are
formed. Fallout, transported by the wind, can settle over and area extending hundreds of
miles from the point of explosion.
Weather conditions, the speed and direction of winds, and the topography of the land would
affect the distribution of fallout. Extensive areas would receive little or no fallout.
Others would have heavy accumulations.
Kinds of radiation from fallout
Fallout particles give off two types of harmful radiation, gamma rays and beta particles.
1.Gamma rays are similar in X-rays. They are deeply penetrating and can damage
body cells. Although all cells are subject to damage, bone marrow cells and cells
in the intestinal lining appear to be particularly sensitive. Fortunately, most
animals can repair some radiation damage by replacing cells or increasing the
activity of undamaged cells.
2. Beta particles cannot penetrate as deeply as gamma rays, but they can also damage
living cells. Beta particles can cause severe skin burns if fallout is retained on
the skin, and they can damage cells in the digestive tract if fallout is ingested
with food or water.
Measuring radiation
A unit of radiation exposure is called a Roentgen (R). Instruments can measure the number of
radiation exposure units in a given period. Total radiation exposure over a certain period
of time is often referred to as a total dose, such as 700 R over a 7-day period.
After fallout is deposited, radiation levels decrease with time. Radiation levels decrease
rapidly at first, and they more slowly. The decrease of radiation level with time is call
"decay."
Distance decreases radiation dose. The further you are from the radiation source, the smaller
the dose you would receive. Also, the more total weight of material (shielding) between the
radiation source and yourself, the smaller the dose you would receive.
Source: Disaster Handbook for Extension Agents - Nuclear 1
