Radioactive contamination is the pollution of an area, item or individual with material which emits ionising radiation through a process of nuclear decay1. This pollution may be physical (due to the spread of radioactive material) or may result from the conversion of previously non-radioactive material due to exposure to radiation from external sources.
In addition, some areas are intrinsically "contaminated" with naturally occurring radioisotopes. In the natural world, radionuclides are made by cosmic rays and decay within the earth, and these constitute the natural radiation background, which is usually at a safe level2, although underground radon gas can accumulate in poorly-ventilated buildings, caves and mines. Deposits containing fuels such as coal, oil and gas can contain natural radium and other isotopes which will be released when the fuel burns. Also, natural radionucleotides like radium3 will irradiate their surrounding area - not an issue whilst they are underground, but a cave that taps into a radium deposit (let alone the river that taps it) may be a little hostile, and a mine deliberately sunk to extract radium even more so.
Artificially, an area can become contaminated with radioactive elements if there is a nuclear detonation nearby, as a result of prolonged bombardment from ionising radiation or fast neutrons or if radioactive waste is released in the area. Contamination from a nuclear explosion is often called fallout. A radiological weapon or "dirty bomb" generates fallout as its main - perhaps only - purpose.
Elements found in fallout or contamination include cobalt, radium, strontium, caesium, and so on. Each fallout component decays at a different rate and is dangerous in different ways. The exact isotope mix in a given mass of fallout will depend on the physics of the device that created it and can, theoretically at least, be used to identify the source of the explosion (if that isn't already known). Unstable iodine is a short-lived component that is attracted to the thyroid, so non-radioactive iodine supplements are used to stop the body from taking up the poisonous isotope. Caesium isotopes have a nasty tendency to substitute for calcium in a variety of biological processes (notably ending up in milk and in bones), leading to deep, hard to reverse irradiation of living targets. Cobalt-60 was, at one stage, identified as the optimum material for deliberate irradiation of enemy territory as it has an unpleasant combination of radiological activity, half-life and easy biological uptake. There are also safer by-products from irradiation such as deuterium.
Fallout from an atmospheric nuclear test can sometimes be detected in trace amounts thousands of miles away and it was this realisation which lead to the general abandonment of atmospheric testing (and thereafter underground testing as well) in the latter half of the twentieth century.
Apart from the safety risks, radioactivity can be a nuisance in other ways. Few people will buy contaminated scrap metal, for example, and steel made in blast furnaces after the invention of the nuclear explosive contains trace radiation that can interfere with scientific instruments.
Game and Story Use
- This is a standard way to make an area off-limits, and may be a Bland Rationalisation used to repel people from an area.
- An area which has been evacuated due to contamination is a good way to create a creepy Urban Prairie or a miniature Post-Apocalyptic Decay feel.
- Maybe the phlebotinum is disrupted by radioactive contamination and devices that use it must be built from uncontaminated materials, which may be scarce in some settings.
- Or maybe it only works in a sufficiently tainted environment and the technicians just need to be replaced every so often.
- Salvaging materials from the pre-atomic age may be profitable - the remains of the Kaiserliche Marine at Scapa Flow, for example, are at risk of being plundered by looters looking for uncontaminated scrap metal.
- In fiction, radioactive contamination has almost magical properties to enduce superpowers and the like. The reality is both more prosaic and less pleasant, but for a pulp era game, this is an excellent source of wierdness.
- Few people will buy contaminated scrap metal … if they know that it is contaminated, but PCs may find themselves racing to track down a consignment of highly irradiated material before it gets recycled and used for something else.
- For example, scrap metal thieves may steal a consigment of irradiated steel from a decommissioned power plant, the PCs must chase it down before it's recycled into consumer goods … without starting a public panic around the idea that the supply chain is already contaminated.
- Not just scrap metal. The classic post-apocalyptic novel Alas, Babylon has a scene in which a looter is exposed to high levels of radiation from the gold he's been scavenging and hoarding. The community must find a safe way to dispose of the gold where no one else will try stealing it.
- In a fantasy setting: In Poul Anderson's Three Hearts and Three Lions, the hero, an engineer transported to a fantasy realm, realizes that the giant he has turned to stone is now composed of an unstable isotope of silicon and that the entire area is now radioactive. It occurs to him that this might be why gold taken from giants might be considered "cursed".
- After the end - especially if that end came about due to atomic warfare - the question may not be whether something is contaminated or not, but how much.