Counting gross alpha/beta

Gross alpha and gross beta activity can be determined by various radioactive counters, such as internal proportional, alpha scintillation, and Geiger counters. Radium in water can be measured by co-precipitating with barium sulfate followed by counting alpha particles. Radium-226 can be measured from alpha counting of radon-222. Various methods are well documented (APHA, AWWA, and WEF 1998. Standard Methods for the Examination of Water and Wastewater, 20 ed. Washington DC American Public Health Association). 

Air filters and gummed deposition collection films first are measured by gross alpha- and beta-particle counting and gamma-ray spectral analysis. Usually, 1/2 of the sample then is dissolved to perform radiochemical analysis of the deposited radionuclides. The filter can be dry ashed, and then totally dissolved with an HNO3-HF treatment. 

The sample may arrive unliltered or separated as filtered water and the filter that contains the solids. The water sample is preserved with dilute acid or a preservative suitable for a radionuclide such as 1 that may be lost from an acid solution. Water without suspended solids is ready for evaporation to measure the gross alpha- and beta-particle activity, measure gamma rays by spectral analysis, and perform radiochemical analysis. The solids usually are counted similarly and then processed for dissolution as described in Section 6.2.1 for subsequent radionuclide analysis. 

Paper or cloth smears are used, often in response to regulations, to wipe surfaces of specified area (e.g., 100 cm ) to check for removable radionuclides. The smears are counted directly by gamma-ray spectral analysis. For gross alpha- or beta-particle measurements, thin smears are counted in a proportional counter or immersed in a cocktail for LS counting. Further analysis for a radionuclide of interest that emits... 

Determination of gross alpha- or beta-particle activity is a measurement for which the source is prepared for counting without chemical separation. The measurements are performed to ... 

Initial gross alpha- and beta-particle counting... 

A COMPARISON OF ANALYTICAL METHODS FOR SCREENING GROSS ALPHA AND BETA RADIOACTIVITY IN WATER BY LIQUID SCINTILLATION COUNTING AND GAS FLOW PROPORTIONAL COUNTING... 

The classical approach consists of evaporating a known volume of water and measure the activity of the residue in a glass flow proportional counter (GFPC) an attractive alternative to classical methods is the ultra-low level liquid scintillation counting (LSC) coupled to alphaHxita discrimination. These methods allow rapid and simple determination of gross alpha and beta activities, which are simultaneously measured through alpha beta discrimination technique. 

Through the sampling head, the pump unit feeds air to the detection head which contains a sequentially advanced filter cartridge that captures alpha and beta emitters for detection. The detection type is gross counting for beta, gamma and spectrometry for alpha particulates using dual passivated silicon detectors. 

An aqueous sample may be added to the cocktail directly, after minor prior processing, or at the end of a radiochemical separation procedure. Direct addition is the equivalent of gross activity counting discussed in Section 7.2.4 except that some spectral analysis may be possible. Alpha particles can be differentiated from beta particles by deposited energy, pulse shape, and decay time. Self-absorption is of no concern. Quenching and luminescence, discussed in Section 8.3.2, often occur. Identification by maximum beta-particle energy is approximate, and requires comparison to radionuclide standards. 

Channel A records true "gross" or "total" activity because it includes those counts associated with compton and auger electrons as well as alpha and beta activity. 

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