A nuclear burst results in four types of ionizing radiation: neutrons, gamma rays, beta, and alpha radiation. The initial burst is characterized by neutrons and gamma rays while the residual radiation is primarily alpha, beta, and gamma rays. The effect of radiation on a living organism varies greatly by the type of radiation to which the organism is exposed. See [Table A-8] for characteristics of nuclear radiation.
a. Alpha particles are extremely massive, charged particles (four times the mass of a neutron); they are a fallout hazard. Because of their size, alpha particles cannot travel far and are fully stopped by the dead layers of the skin or by the uniform. Alpha particles are a negligible external hazard, but if inhaled or ingested, can cause significant internal damage.
Figure A-2. Threshold distance for minimal chorioretinal burn and flash blindness versus yield (airburst) at night.
Table A-8. Characteristics of Nuclear Radiation
| NAME AND SYMBOL | WHAT IS IT | SOURCE | ENERGY AND SPEED | RANGE IN AIR | RANGE IN TISSUE | SHIELDING REQUIRED | BIOLOGICAL HAZARD |
| α ALPHA PARTICLE | HELIUM NUCLEUS | DECAY OF URANIUM AND PLUTONIUM | ENERGY VARIES: SPEED VARIES FROM 1/20 TO 1/10 SPEED OF LIGHT | ~ 5 cm | CANNOT PENETRATE THE EPIDERMIS | NONE | NONE, UNLESS INGESTED OR INHALED IN SUFFICIENT QUANTITIES |
| β BETA PARTICLE | HIGH-SPEED SPEED ELECTRON | DECAY OF FISSION PRODUCTS AND NEUTRON INDUCED ELEMENTS | VARIES OF SKIN | 5 METERS OR MODERATE | SEVERAL LAYERS SKIN INJURY | STOPPED BY A FEW cm OF Al CLOTHING | SUPERFICIAL |
| γ GAMMA RAY | ELECTRO-MAGNETIC ENERGY | DECAY OF FISSION PRODUCTS AND NEUTRON INDUCED ELEMENTS | ENERGY VARIES: TRAVELS AT THE SPEED OF LIGHT | UP TO 500 METERS, BUT IS ENERGY DEPENDENT | VERY PENETRATING, BUT IS ENERGY DEPENDENT | DENSE MATERIAL, SUCH AS CONCRETE, STEEL PLATE, EARTH | WHOLE BODY INJURY, MANY CASUALTIES POSSIBLE |
| η NEUTRON | UNCHARGED PARTICLE | FISSION AND FUSION REACTIONS | VARIES | LESS THAN GAMMA, BUT IS ENERGY DEPENDENT | VERY PENETRATING, BUT IS ENERGY DEPENDENT | HYDROGENOUS MATERIALS, SUCH AS WATER OR DAMP EARTH | WHOLE BODY INJURY, MANY CASUALTIES POSSIBLE |
b. Beta particles are very light, charged particles that are found primarily in fallout radiation. These particles can travel a short distance in tissue; if large quantities are involved, they can produce damage to the basal stratum of the skin. The lesion produced is similar to a thermal burn (called a beta burn).
c. Gamma rays, emitted during the nuclear detonation and in fallout, are uncharged radiation similar to X rays. They are highly energetic and pass through matter easily. Because of its high penetrability, radiation can be distributed throughout the body, resulting in whole body exposure.
d. Neutrons, like gamma rays, are uncharged, are only emitted during the nuclear detonation, and are not a fallout hazard. However, neutrons have significant mass and interact with the nuclei of atoms, severely disrupting atomic structures. Compared to gamma rays, they can cause 20 times more damage to tissue.