ULTRATRACE ANALYSIS This term could be used generally to describe the whole area of trace analysis using micro-sized samples, but could be more precisely specified as trace analysis with sample size £ 10-4 g and constituent content £ 100 ppm (0.01%). C. See subtrace analysis .
UNSEALED SOURCE A radioactive source which is not encapsulated, in contrast to a sealed source .
URANIUM SERIES The natural decay chain commencing with 238U and ending with stable 206Pb. The mass number of each member of the series is representable as 4n+2 where n is an integer.
VAN DE GRAAFF ACCELERATOR An electrostatic generator in which a high potential is produced by the accumulation of electric charge conveyed to an insulated conductor by a continuously moving belt. The potential generated is used for accelerating charged particles. NM.
WASTE, HIGH-LEVEL (i) The highly radioactive liquid, containing mainly fission products, as well as some actinides , which is separated during chemical reprocessing of irradiated fuel (aqueous) waste from the first solvent extraction cycle and those waste streams combined with it. (ii) Spent reactor fuel, if it is declared a waste. (iii) Any other waste with a radioactivity level comparable to (i) or (ii). WASTE.
WASTE, LOW-LEVEL Waste which, because of its low radionuclide content, does not require shielding during normal handling and transportation. WASTE.
WELL DETECTOR Special type of counter in which the detector is shaped in the form of a well to contain the sample whose radioactivity is to be counted in nearly 4p geometry.
WESTCOTT CROSS-SECTION See cross section, effective thermal .
WIGNER EFFECT Displacements of atoms from their positions in a crystal structure by radiation. NM.
WILZBACH LABELING See labeling, Wilzbach .
X-RADIATION, CHARACTERISTIC See characteristic X-radiation .
X-RAY Electromagnetic radiation of wavelengths in the approximate range 10-11 to 10-9 m whose origin is in the rearrangement of electronic states of atoms from an excited state to a lower energy excited state or to the ground state.
X-RAY EMISSION ANALYSIS, PARTICLE INDUCED A method of analysis based on the measurement of the energies and intensities of characteristic X-radiation emitted by a sample during irradiation with heavy charged particles.
X-RAY EMISSION ANALYSIS, RADIOISOTOPE INDUCED A method of analysis based on the measurement of the energies and intensities of characteristic X-radiation emitted by a sample during irradiation with a radioactive source .
X-RAY FLUORESCENCE The emission of X-ray radiation by an atom as a result of the interaction of radiation with its orbital electrons . IUPAC82..
X-RAY FLUORESCENCE ANALYSIS A method of analysis based on the measurement of the energies and intensities of characteristic X-radiation emitted by a sample during irradiation with X-rays of wavelength shorter than their characteristic wavelengths.
X-RAY FLUORESCENCE ANALYSIS, ENERGY-DISPERSIVE A method of X-ray fluorescence analysis involving the measurement of the wavelength (energy) spectrum of the emitted radiation , e.g., by a semiconductor detector .
X-RAY FLUORESCENCE ANALYSIS, WAVELENGTH-DISPERSIVE A method of X-ray fluorescence analysis involving the measurement of the wavelength (energy) spectrum of the emitted radiation , e.g., by using a diffraction grating or crystal.
XRF X-ray fluorescence .
YIELD, FLUORESCENCE For a given excited state of a specified atom, the ratio of the number of excited atoms which emit a photon to the total number of excited atoms.
YIELD, RADIOCHEMICAL See radiochemical yield .