Detection of radionuclides

For the monitoring of personnel radiation exposures, measurement of radioactive contamination and surveying of laboratories and equipment, and for the detection of radionuclides incorporated in the human body, various detectors and instruments are used. The principles of operation of these detectors have been discussed in the previous sections of this chapter. 

The high sensitivity of detection of radionuclides has already been emphasized in section 17.1 with respect to their application in analytical chemistry. 

As mass spectrometry has continued to gain sensitivity and reliability, inductively coupled plasma/mass spectrometry (ICP-MS) has become increasingly useful in the measurement of radionuclides. The optimization of ICP-MS is improving our ability to use the atomic detection of radionuclides in that it allows the near-complete isotopic analysis of any form of sample. Aqueous samples are generally introduced into the plasma source, and solids or individual particles, and organic solutions, may be atomized and continuously introduced into the plasma source. 

Mutschke U, Pribilla O. 1967. Detection of radionuclides of biological interest in human bones and tissues. Prog Chem Toxicol 3 244-303. 

One should also note the large volume of water that is necessary for detection of radionuclides. Recent freshwater bodies normally contain only about 0.1-1 mBq/1 of global-fallout Cs. Therefore, volumes of 200 1 or greater must be used in order to... 

Detection of radionuclides based on their radiations—alpha, beta, or gamma— commonly occurs by one of two processes. Electrons bound to the atoms or molecules of the material through which charged particles such as alpha and beta particles pass are released in a process called ionization. The separated electrons and ions can be collected at two electrodes by imposing a potential difference across the detector space their presence is then measured as pulses or a current. 

Tracht, S. E., Cruz, L., StobbaWiley, C. M., and Sweedler, J. V., Detection of radionuclides in capillary electrophoresis using a phosphor-imaging detector. Anal. Chem., 68, 3922, 1996. 

This configuration meets all die fimctional requirements for effective radionuclide sensors. The packed column format provides for efficient fluidic processing of the sample for preconcentration. The detection method is radiometric via die process of scintillation. Selective chemistry is in very close proximity to the scintillation material and retains the radionuclides for counting. These new column sensors represent a novel and advantageous approach for detection of radionuclides vdien selective preconcentration is required. 

An excellent review paper was recently written and published by Hou (2008). To express and quantify the advantage of activation analysis with respect to direct radiometric detection of radionuclides, an advantage factor AF was defined by Byrne and Benedik (1999) ... 

For detection of radionuclides with Iy2> I h, irradiation 48 h at 2x10 cm" s (cadmium ratio =11, i.e., ratio obtained by irradiation without and with cadmium cover) decay time 10 h counting time 64 h. For detection of radionuclides with t]/2 < 1 h... 

Online detection of radionuclides is also integrated in sensors developed for environmental monitoring. Sensors are constituted by a preconcentrating minicolumn packed with scintillating microspheres, which integrates radiochemical separation and radiometric detection steps within a... 

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