In my last article, I discussed the various aspects of radiation sickness, but haven’t yet defined just what radiation is. The quick definition of radiation is energy given off by unstable matter in the form of rays or high-speed particles. Some basic chemistry paraphrased from the US Nuclear Regulatory Commission (US NRC): All matter, including you, is composed of atoms. Atoms are made up of various parts; the central nucleus contains minute particles called protons and neutrons, and the atom’s outer shell contains other particles called electrons. The nucleus has a positive electrical charge, while the electrons has a negative electrical charge. Neutrons are, well, neutral. These entities work within the atom toward a stable balance by getting rid of excess atomic energy (called radioactivity). Unstable nuclei want to become stable, and may emit energy; this emission is what we call radiation.
All matter is composed of atoms. Atoms are made up of various parts; the nucleus contains minute particles called protons and neutrons, and the atom’s outer shell contains other particles called electrons. The nucleus carries a positive electrical charge, while the electrons carry a negative electrical charge. These forces within the atom work toward a strong, stable balance by getting rid of excess atomic energy (radioactivity). In that process, unstable nuclei may emit a quantity of energy, and this spontaneous emission is what we call radiation
Put simply, radiation is divided into “ionizing” and “non-ionizing”. We are bombarded daily by radiation from multiple non-ionizing sources: the sun’s visible light and heat, microwaves, radio waves, radar, and others. This type of radiation deposits energy in the materials through which it passes, but doesn’t break molecular bonds or destabilize atoms. These effects, however, can be caused by ionizing radiation, where the atom becomes charged and unstable, not a healthy state for living cells.
There are several types of radiation given off by a nuclear weapon: Alpha, beta, and neutron particles, and gamma and X-rays. All are caused by unstable atoms, which, in order to reach a stable state, must release energy in the form of radiation. Atoms can do this by , for example, shedding electrons, which causes them to become ionized.
penetration power of different radiation types (image by NRC.gov)
Alpha radiation occurs when an atom undergoes radioactive decay, giving off an alpha particle. Due to their charge and mass, alpha particles only travel a few centimeters and don’t even penetrate the outer layer of skin. If ingested, inhaled, or somehow injected, however, alpha particles are capable of causing considerable damage to living cells.
Beta radiation takes the form of particles. Due to the smaller mass, it is able to travel further in air than an alpha particle, but can be stopped by a thick piece of plastic, a stack of paper, even clothing. It can penetrate a short distance into exposed skin, though, causing “beta burns“ which may require treatment. However, the main threat is from ingesting it, perhaps from crops growing in fallout areas.
Gamma and X-rays, unlike alpha or beta, are two types of radiation that do not consist of any particles at all, but instead, pure electromagnetic energy. Think of gamma rays as X-rays on steroids. Gamma radiation can travel much farther through air than alpha or beta particles (which have mass) and is responsible for the most ill effects on humans after a nuclear explosion. It can, however, be blocked by various materials. The thickness required for each material depends on the density; you’ll see various shielding options and thickness requirements described in our articles and videos on radiation sickness.
(Note: Examples of elements that are gamma ray emitters include iodine-131, cesium-137, cobalt-60, and radium-226.)
Lastly, Neutron radiation consists of high-speed particles with high penetrating power. Neutron particles travel further in air than other forms of radiation, but can be blocked by materials that contain hydrogen, such as water (H20) and concrete. When neutron particles are absorbed into a stable atom, they make it unstable and more likely to emit radiation. Therefore, it’s the only type discussed here that can turn other materials radioactive.
Although radiation is a major issue after a nuclear blast, it should be noted that most damage from such weapons are the result of massive amounts of the energy generated by shock and heat waves. The blast kills people close to ground zero, and causes major trauma much further away. Flying debris and falling buildings account for more casualties. The heat is so intense that almost everything close to ground zero is vaporized. At a distance, the extreme heat still causes severe burns and starts firestorms.
You might think that missile defense systems will protect us, and perhaps they would if someone targeted us with one huge 50 megaton bomb. Unfortunately, what will happen is that large cities will be hit with clusters of smaller bombs, but still 10 times larger than the bombs that hit Japan in 1945. We might be able to intercept one, maybe several, incoming missiles, but all of them? I’ll let you answer that question.