ABSTRACT
The radioactivity measured in the aqueous or the solid samples can be expressed in different units as activity per volume or mass. Instruments of several types are commercially available to detect and measure radiation. Such instruments include gas-flow proportional counters, scintillation counters, alpha spectrometers, and gamma spectrometers. In addition, various methods may be applied to measure the radioactivity of samples. This chapter outlines the principle of operation and the merits and limitations of these instruments. Gross alpha and gross beta particles in various environmental matrices are determined by several procedures, mostly differing in the "sample preparation" techniques. One such common technique is the evaporation method. The chapter describes this method briefly. All alpha emitting isotopes of radium can be measured by the precipitation method, followed by alpha counting with a gas flow internal proportional counter or a thin-end window gas flow proportional counter or with an alpha scintillation counter. Radium-224 in water can be measured by sequential precipitation method.
