Glossary

Partial Test Ban Treaty (PTBT)
Also known as the Limited Test Ban Treaty (LTBT) or the Moscow Treaty, prohibits nuclear weapons tests "or any other nuclear explosion" in the atmosphere, in outer space, and under water. While not banning tests underground, the treaty does prohibit nuclear explosions in this environment if they cause "radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control" the explosions were conducted.
Peaceful Nuclear Explosion (PNE)
Nuclear explosions carried out for non-military purposes, such as the construction of harbors or canals. PNEs are technically indistinguishable from nuclear explosions of a military nature.
Permissive Action Links (PAL)
Permissive Action Links, or PALS, are systems that make it impossible to activate the weapon without proper authorization. These are electronic devices that prevent the activation or arming of the weapon unless the correct codes are inserted into it. Typically two codes should be inserted, simultaneously or close together. The codes are usually changed regularly.
Photon
A unit or 'particle' of electromagnetic radiation, carrying a quantum of energy which is characteristic of that particular radiation.
Pile
An older term for nuclear reactor.
See; Reactor.
Pitchblende
The ore from which uranium and radium are obtained.
Pounds per Square Inch (psi)
A measure of nuclear blast overpressure or dynamic pressure, used to calculate the effects of a nuclear detonation or the ability of a structure to withstand a nuclear blast.
Plutonium-239 (Pu-239)
A metallic element used for nuclear weapons. The half-life is 24,110 years.
Pressurized-Water Reactor
A reactor in which neutrons heat pressurized water, which is then used to produce steam to run a turbine.
See; Boiling-Water Reactor, Light-Water Reactor, Reactor.
Primary
The fission part of a fusion bomb. The 'match' which ignites the fusion reaction.
See; Fusion, Fusion Bomb.
Proliferation
The process by which nations acquire nuclear weapons.
Prompt radiation
Radiation released immediately by a nuclear explosion.
Proton
A particle of mass unity (approximately) carrying a unit positive charge; it is identical physically with the nucleus of the ordinary hydrogen atom. All atomic nuclei contain protons.
See; Nucleus.
Rad
A unit of absorbed dose of radiation; it represents the absorption of 100 ergs of nuclear radiation per gram of absorbing material.
Radiation
Usually refers to the radiant energy emitted by certain elements (such as radium, uranium, plutonium, thorium, and their products). Radiation is often in the form of alpha particles, beta particles, or gamma rays.
See; Radioactivity, Alpha Particle, Beta Particle, Gamma Ray.
Radiation Sickness
The complex of symptoms characterizing the disease known as radiation injury, resulting from excessive exposure of the whole body (or large part) to ionizing radiation. The earliest of these symptoms is nausea, fatigue, vomiting, and diarrhea, which may be followed by loss of hair, hemorrhage, inflammation of the mouth and throat, and general loss of energy. In severe cases, where the radiation has been approximately 1,000 rad or more, death may occur within two to four weeks. Those who survive six weeks after the receipt of a single large dose of radiation to the whole body may generally be expected to recover.
Radioactive
Certain elements (radium, uranium, thorium, and their products), emit radiant energy by spontaneously emitting alpha, beta, or gamma particles.
See; Radioactivity, Alpha Particle, Beta Particle, Gamma Ray.
Radioactive Cloud
An all-inclusive term for the cloud of hot gases, smoke, dust, and other particulate matter from the weapon itself and from the environment. It is carried aloft in conjunction with the rising fireball produced by the detonation of a nuclear weapon.
Radioactive contamination
Deposition of radioactive material in any place where it may harm persons or equipment.
Radioactive decay
The decrease in the amount of any radioactive material with the passage of time due to the spontaneous emission from the atomic nuclei or either alpha or beta particles, often accompanied by gamma radiation. Each decay process has a definite half-life.
Radioactive waste
Materials which are radioactive and for which there is no further use.
Radioactivity
The spontaneous emission of radiation, generally alpha or beta particles, often accompanied by gamma rays, from the nuclei of an unstable isotope. As a result of this emission the radioactive isotope is converted (or decays) into the isotope of a different (daughter) element which may or may not be unstable. Ultimately, as a result of one or more stages of radioactive decay, a stable (nonradioactive) end product is formed.
See; Isotope.
Radioisotope
A radioactive isotope.
See; Isotopes, Radioactivity.
Radiological dispersal device (RDD)
A device that involves radioactive materials and some method by which those materials can be spread over a wide area. It can be a variety of sizes, and the radiation can cause contamination, economic and some physical harm. One type of RDD is the popularly named "dirty bomb." A dirty bomb uses the force of conventional explosives, such as TNT, to scatter radioactive material.
Radiological terrorism
Terrorist acts carried out either by attacking a nuclear facility or through malicious use of a radiological device.
Radiological weapons
Devices that release radiation with the intent of inflicting severe injury or financial and psychological costs. The radiological isotopes used to produce radiological dispersal devices are found in waste from medical facilities, industrial plants, and nuclear power plants.
See; Isotopes, Radioactivity.
Rainout
The removal of radioactive particles from a nuclear cloud by precipitation when this cloud is within a rain cloud.
REM
A unit of biological dose of radiation; the name is derived from the initial letters of the term "roentgen equivalent man (or mammal)." The number of rems of radiation is equal to the number of rads absorbed multiplied by the RBE of the given radiation (for a specified effect). The rem is also the unit of dose equivalent, which is equal to the product of the number of rads absorbed and the "quality factor" of the radiation
Reactor
A facility in which fissile material is used in self-sustaining chain reactions (nuclear fission) to produce heat and/or radiation for both practical application and research and development. A reactor includes fissionable material (fuel) such as uranium or plutonium, and a moderating material and usually includes a reflector to conserve escaping neutrons, provisions for heat removal, and measuring and control elements.
See; Fission, Boiling-Water Reactor, Light-Water Reactor, Pressurized-Water Reactor.
Reentry phase
That portion of the trajectory of a ballistic missile or space vehicle when the vehicle reenters the earth's atmosphere.
Reprocessing
The chemical treatment of spent reactor fuel to separate plutonium and uranium from unwanted radioactive waste by-products.
Roentgen
A unit of exposure to gamma (or X) radiation. It is defined precisely as the quantity of gamma (or X) rays that will produce electrons (in ion pairs) with a total charge of 2.58 x 10-4 coulomb in 1 kilogram of dry air. An exposure of 1 roentgen results in the deposition of about 94 ergs of energy in 1 gram of soft body tissue. Hence, an exposure of 1 roentgen is approximately equivalent to an absorbed dose of 1 rad in soft tissue.
See; Radiation.
Rosenberg Case
The most infamous espionage case at Los Alamos involved David Greenglass. Greenglass gave details on how to obtain the critical mass for a plutonium bomb. Also involved were his sister Ethel Rosenberg and her husband Julius, both of whom were executed in June 1953. The Rosenberg affair stimulated worldwide protest and much anti-American propaganda. The case remains controversial to this day.

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