Proton: A constituent of the nucleus. It has one unit of positive charge and weighs slightly less than a neutron.
Radiation: Energetic charged particles, neutrons and gamma rays which cause ionization in matter. Radiation is produced in nuclear explosions but also occurs naturally from cosmic rays and from the decay of radioactive substances in our surroundings.
Radioactivity: Spontaneous nuclear decay, releasing an alpha, beta, or gamma ray.
Radioisotope: Short for radioactive isotope.
Radiological bomb: A bomb designed to create radioactive contamination.
Radium: Element with charge 88. The principal isotope has a weight of 226 and emits an alpha particle with a half-life of 1620 years.
Range: Distance traveled by an energetic charged particle in matter before it stops. Heavy charged particles move in a straight line inside matter, but electrons frequently change their course. For this reason the range of electrons is only about one-half the total distance traveled.
Reactor: Same as nuclear reactor.
Roentgen: A measure of radiation dose—defined in terms of the amount of energy deposited per unit weight of irradiated material. A dose of 400,000 roentgens in living tissue deposits enough energy to raise the temperature by 1°C. A dose of only 400 roentgens in a human being will cause death fifty per cent of the time.
Shock wave: Expanding front of high pressure and strong winds produced by an explosion.