b'P ROVING THE P RINCIPLERoentgen Spent fuel storage basin Uranium oxideAn international unit of measurement of A pool or pit made of reinforced concrete A metallic compound of uranium andgamma or X- radiation. See R above. containing water and used to store spent oxygen, a useful form of uranium for useSecondary loop nuclear fuel. The water acts as a shield as nuclear fuel because it has a higherpreventing radiation from harming work- melting point than metallic uranium andIn a reactor coolant system, heat carried ers near the pool. can survive the high temperatures insideaway from the reactor core in a prima- Transuranic waste (TRU) a reactor more readily. However, its heatry system is transferred to a second transfer properties are not as efficient asloop. Water in the second loop does not Waste materials contaminated with human- those of metallic uranium.become radioactive and its steam is used made elements heavier than uranium, such Water-moderated reactorto spin turbines for electrical generation. as plutonium. Also called TRU (transuran-Semiscale ic waste). This term also implies a regula- A reactor concept which is designed sotory definition in which the waste contains that water slows down the speed of neu-The informal name of a scale model of a substances with a half-life over twenty trons ejected from fissioning atoms.nuclear reactor operated as part of the years in concentrations of more than one Includes boiling water and pressurizedNuclear Reactor Safety Test Engineering ten-millionth of a curie per gram of waste. water reactor concepts.Program at the NRTS/INEL. Instead of Triga Warm runusing nuclear fuel, the core simulatedthe heat of a nuclear reaction by electrical The brand name of a small, low-power The operation of a chemical processmeans. The device was used to study the reactor manufactured by General Atomics using materials that are slightly radioac-behavior of water and steam in accidents for use in universities and laboratories. tive. A warm run is contrasted withinvolving the loss of coolant caused by a The reactor was in a small pool of water cold or hot runs.broken pipe. used as both coolant and moderator. Waste storage tankScram Similar reactors are often called triga-type reactors. A holding tank for liquid or gaseousA sudden shutting down of a nuclear Tritium wastes which may or may not be radioac-reactor, usually by dropping safety rods, tive.when a predetermined neutron flux or An isotope of hydrogen containing three Zirconiumother dangerous condition occurs. protons. Tritium gas is produced in nuclearShielding reactors and used to boost the explosive A metallic element highly resistant to cor-power of most modern nuclear weapons. It rosion and used to make cladding forMaterial such as lead, concrete, water, is also a constituent of irradiated water nuclear fuel elements. It is sometimesparaffin, and other materials used to pre- associated with reactor operations. alloyed in small amounts in the fuel itself.vent the escape of radiation into the Uranium-235 Zero powerambient or working environment of peo-ple and equipment. A fissionable isotope of the metallic ele- Also called low power, a mode of oper-Spent nuclear fuel ment, uranium. In nature, only 0.7 per- ating a reactor so that it maintains a chaincent of all uranium mined from the reaction at extremely low power levels. ItNuclear fuel containing fission and acti- ground consists of this isotope. produces very little heat. Zero power reac-vation products that can no longer eco- Uranium-238 tors are used as sensitive laboratory toolsnomically sustain a chain reaction and is to pre-test experimental loadings of testwithdrawn from a reactor. The most common isotope of uranium. It reactors and for other analytical purposes. does not generally fission, but can be irra-diated in a reactor and transformed to anisotope of plutonium which does fission.312'