Feather beds — Large metal frameworks used to hold the simulated warheads before detonation in the Vixen B safety trials held at the Taranaki firing pads at Maralinga.
Film badge — A plastic holder containing a piece of film similar to a dental x-ray film and worn by personnel at a nuclear test. Radiation exposes the film. After a nuclear test, the film is developed, and the degree of darkening apparent is a measure of the radiation dose received. The film holder usually contains metal filters to enable discrimination between different types of radiation.
Fission — The process in which the nucleus of a heavy element such as uranium or plutonium splits into two nuclei of lighter elements, accompanied by the release of substantial amounts of energy.
Forward area — The restricted zone within which the major bomb trials and minor radiological experiments took place at the British nuclear tests sites.
Fusion — The process in which the nuclei of light elements such as hydrogen (particulalry its isotopes deuterium or tritium) combine to form the nucleus of a heavier element, accompanied by the release of substantial amounts of energy.
Gamma radiation — Penetrating electromagnetic radiation emitted from the nucleus of radioactive elements. This form of radiation is most readily measured by monitoring equipment such as film badges and dosimeters.
Half-life — The time in which the activity of a radioactive species will decline to half its initial value by radioactive decay. For example, plutonium-239 has a half-life of 24 400 years, so it takes 24 400 years for half of its radioactivity to decay, then another 24 400 years for half of the remaining radiation to decay, and so on. The half-life of a radioactive species is a characteristic property of that species.
Health physics — The science of human health and radiation exposure – a branch of medical science devoted to radiation safety.
Ionising radiation — Radiation that integrates with matter to add electrons to or remove electrons from the atoms of the material absorbing it, producing electrically charged (positive or negative) atoms called ions.
Isotopes — Forms of the same element whose nuclei contain different numbers of neutrons and therefore have different mass numbers. Isotopes of an element have nearly identical chemical properties but differ in their nuclear properties. For instance, some isotopes of an element may be radioactive, and others not.
Major trials — Atomic tests conducted at Monte Bello Islands, Emu Field and Maralinga in Australia that involved detonating a complete atomic bomb, resulting in a mushroom cloud.
Minor trials — Hundreds of tests conducted at Emu Field and Maralinga in Australia that involved examining how radioactive materials and atomic weaponry would behave under various conditions such as fire or conventional explosion.
Neutron — A nuclear particle with no electric charge (neutral) and a mass approximately equal to or slightly greater than that of a proton. Neutrons are present in all atoms except those of the lightest isotope of hydrogen.
Nuclides — Species of atoms having a specified number of protons and neutrons in their nuclei. Radionuclides are the radioactive forms of nuclides. They are often expressed as, for example, 239Pu, which shows in numerical form the number of neutrons combined with the number of protons (in this case 145 neutrons and 94 protons) and hence the form of isotope.
Operation Brumby — A clean-up operation, more extensive than Operation Hercules, mounted by the AWRE at the Maralinga test range between April and July of 1967. Operation Brumby was considered by the AWRE to be the final clean-up before departing the atomic weapons test site permanently.
Operation Hercules — A clean-up operation mounted by the AWRE at the Maralinga test range between August and November 1964. This clean-up was intended as a temporary measure to allow a reduction in range staff to a care and maintenance level while long-term decisions were made about its future use.
Operation RADSUR — A RADiological SURvey of both the Maralinga and the Emu Field atomic test sites carried out by the AWRE in October and November 1966. RADSUR was used as the basis for Operation Brumby.
Plumes — Clouds of radioactive material from an explosion, as well as the visible fallout after the radioactive material is carried back to the ground. The scientists on the 1984 field trip to Maralinga could detect plumes in the form of elongated hand-shapes on the ground from each detonation of the Vixen B experiments in the 1960s, because the plutonium carried back down still sat close to the surface.
Plutonium (Pu) — A dense, silvery radioactive element that does not occur naturally but is made in a reactor by irradiating uranium with neutrons. It was first produced in 1940. Plutonium has 13 known isotopes, of which plutonium-239 has the longest half-life (24 400 years). A fissile material, plutonium-239 can be used as the core of a nuclear weapon.
Quartz fibre electrometer — Dosimeters worn in the pocket like pens and read by looking through a lens to observe the position of a quartz fibre against a scale.
Radioactivity — The property of certain radionuclides of spontaneously emitting particles and/or x-ray or gamma ray radiation, or of undergoing spontaneous fission. The rate of decay is specific to a given species of radionuclide and cannot be changed by known physical or chemical processes.
Radionuclides — Radioactive nuclides.
Sievert — The unit of biological absorption of ionising radiation, expressed as dose equivalent. A millisievert is one one-thousandth of a sievert. At the time of the British nuclear tests in Australia the standard measurement of dose equivalence was the rem.
Stochastic effects — Medical conditions associated with ionising radiation, such as cancer or hereditary illness, induced at random but with no threshold radiation dose, for which probability (but not severity) increases with increasing doses of radiation. These effects may show up many years after exposure. Because stochastic effects can occur in individuals who have not been exposed to radiation above background levels, it is impossible to determine for certain whether an occurrence of cancer or genetic damage was due to a specific exposure.
Thermonuclear weapon — A nuclear device that relies on raising the temperature of a mixture of deuterium and tritium nuclei to above 10 million degrees Celsius, at which point nuclear fusion reactions occur. This type of weapon is also known as a hydrogen bomb.
Warhead — The explosive head of a bomb.
Yield — The amount of energy generated by a nuclear explosion, usually expressed in kilotonnes (for fission devices) or megatonnes (for fusion devices). A kilotonne is equivalent to 1000 tonnes of TNT, and a megatonne is equivalent to 1 million tonnes of TNT.
References
Arnold, Lorna & Smith, Mark, Britain, Australia and the Bomb: The Nuclear Tests and Their Aftermath, 2nd edn, Palgrave Macmillan, New York, 2006.
Beale, Howard, Minister for Supply, ‘Atomic Tests in Australia’, top-secret Cabinet briefing document, submission no. 73, Canberra, 11 August 1954, Malone files.