Standard Practice for High-Resolution Gamma-Ray Spectrometry of Water

Importancia y uso:

5.1 Gamma-ray spectrometry is of use in identifying radionuclides and in making quantitative measurements. Use of a semiconductor detector is necessary for high-resolution measurements.

5.2 Variation of the physical geometry of the sample and its relationship with the detector will produce both qualitative and quantitative variations in the gamma-ray spectrum. To adequately account for these geometry effects, calibrations are designed to duplicate all conditions including source-to-detector distance, sample shape and size, and sample matrix encountered when samples are measured.

5.3 Since some spectrometry systems are calibrated at many discrete distances from the detector, a wide range of activity levels can be measured on the same detector. For high-level samples, extremely low-efficiency geometries may be used. Quantitative measurements can be made accurately and precisely when high activity level samples are placed at distances of 10 cm or more from the detector.

5.4 Electronic problems, such as erroneous deadtime correction, loss of resolution, and random summing, may be avoided by keeping the gross count rate below 2000 counts per second (s^–1) and also keeping the deadtime of the analyzer below 5 %. Total counting time is governed by the radioactivity of the sample, the detector to source distance and the acceptable Poisson counting uncertainty.

Subcomité:

D19.04

Referida por:

D7784-20, D3454-21, C1295-24, D4785-20, C1402-17

Volúmen:

11.02

Número ICS:

71.040.50 (Physicochemical methods of analysis)

Palabras clave:

gamma-ray spectrometry; germanium detectors; high-resolution gamma-ray spectrometry; HPGe; photon spectrometry; water;