Radionuclides detectors separation techniques

Once the radionuclide content of a sample is specified, available detectors must be selected to measure the emitted radiation. The choice of detection technique influences the need for and extent of the radiochemical separation, as discussed in Chapter 7. 

The difficulty for gamma spectrometrists is that no gamma radiation is emitted by these radionuclides and thus they cannot be measured by the techniques described in this text. To determine pure beta emitters in a mixture of radionuclides, a degree of chemical separation is required, followed by measurement of the beta radiation, perhaps by liquid scintillation or by using a gas-filled detector. 

There are several potential sources of radioactive materials that can contaminate water (see Chapter 4, Section 4.14). Radioactive contamination of water is normally detected by measurements of gross P activity and gross a activity, a procedure that is simpler than detecting individual isotopes. The measurement is made from a sample formed by evaporating water to a very thin layer on a small pan, which is then inserted inside an internal proportional counter. This setup is necessary because P particles can penetrate only very thin detector windows, and a particles have essentially no penetrating power. More detailed information can be obtained for radionuclides that anit y-rays by the use of gamma spectrum analysis. This technique employs solid-state detectors to resolve rather closely spaced y peaks characteristic of specific isotopes in the sample s spectra. In conjunction with multichannel spectrometric data analysis, it is possible to determine a number of radionuclides in the same sample without chemical separation. This method requires minimal sample preparation. 

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