ASTM D3649-06(2014)

1.1 This practice covers the measurement of gamma-ray emitting radionuclides in water by means of gamma-ray spectrometry. It is applicable to nuclides emitting gamma-rays with energies greater than 45 keV. For typical counting systems and sample types, activity levels of about 40 Bq are easily measured and sensitivities as low as 0.4 Bq are found for many nuclides. Count rates in excess of 2000 counts per second should be avoided because of electronic limitations. High count rate samples can be accommodated by dilution, by increasing the sample to detector distance, or by using digital signal processors.

1.2 This practice can be used for either quantitative or relative determinations. In relative counting work, the results may be expressed by comparison with an initial concentration of a given nuclide which is taken as 100 %. For quantitative measurements, the results may be expressed in terms of known nuclidic standards for the radionuclides known to be present. This practice can also be used just for the identification of gamma-ray emitting radionuclides in a sample without quantifying them. General information on radioactivity and the measurement of radiation has been published (1,2).2 Information on specific application of gamma spectrometry is also available in the literature (3-5). See also the referenced ASTM Standards in 2.1 and the related material section at the end of this standard.

1.3 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitation prior to use.