b'G LOSSA R YNuclear waste rapid withdrawal of the control rod is pre- RadioactivityA general term including high-level, sumed to have brought about a state of The spontaneous emission of particles ortransuranic, low-level, mixed low-level, prompt criticality, in which the chain reac- waves from the nucleus of an atom. Theand byproduct material. Each of these tion did not require the emission of the emissions may include alpha and betaterms is further defined for regulatory delayed neutrons to begin or continue. particles, and gamma rays.purposes.Proton RadionuclideNucleus An elementary atomic particle that is A radioactive species of an atom. ForCenter of an atom consisting of a cluster identical with the nucleus of a hydrogen example, strontium-90 is a radionuclideof neutrons and protons. It contains near- atom. Along with neutrons, it is a con- (also called a radioisotope) of strontium.ly all of the mass of the atom. stituent of all other atomic nuclei.PUREX RaLaPlutonium An abbreviation for RadioactiveA metallic element most typically created An acronym for plutonium-uranium Lanthanum, one of the fission products ofby irradiating uranium in nuclear reactors extraction, the name of a chemical a nuclear reaction. It was useful to scien-(although small amounts have been found process used to reprocess spent nuclear tists developing a plutonium bomb.in nature). The fissionable isotope pluto- fuel and irradiated targets. nium-239 can be used as reactor fuel. R&D 100 Award Reactor vesselPressurized water reactor Research and development awards pre- A cylindrical steel container enclosing thesented by R&D Magazine. Only one hun- fuel elements, control elements, coolantA reactor concept in which water is used dred R&D innovations are recognizedin piping, and other structures that supportto cool the reactor core. It is pressurized the country each year. the core of a nuclear reactor.to prevent it from boiling. Heat is trans- Reflectorferred from a primary coolant pipe to a Radiationsecondary pipe. E n er gy transferred through space or some Part of the structure of some nuclearPrimary loop other media in the form of particles or reactors designed to reflect neutrons backwaves. If the particles or waves are capable toward the core of the reactor.A closed system of piping through which of breaking up atoms or molecules, then the Rem (or REM)coolant flows past the nuclear fuel in a radiation is said to be ionizing radiation.reactor. An abbreviation meaning roentgenPrompt critical R equivalent man, a measure of theAn abbreviation meaning roentgen. amount of exposure (dose) of radiationAstate of criticality derived from the fact One roentgen (R) measures the power of that takes into account the biologicalthat a small percentage of neutrons in a gamma or X-rays to produce ionization effectiveness of the exposure on the par-chain reaction are not emitted as soon as (ie, strip an electron from an otherwise ticular organ exposed.the atom splits, but are delayed for as stable atom) in one gram of air. Retention basinlong as a few minutes. Prompt neutronsare emitted immediately upon fission. If a Radioactive waste An outdoor basin (of any of severalreactor goes prompt critical, it indicates By-products of nuclear processes which designs) in which liquid solutions arethat reactivity has increased to the point are radioactive and have no useful recy- deposited and held pending evaporationthat prompt neutrons alone are suff ic ien t or the precipitation of solids.clable purpose.to maintain the chain reaction. Rapid mul-tiplication of neutrons can occur after thispoint. In the SL-1 reactor accident, the3 1 1'