This Chapter briefly describes the main measurement techniques, their advantages and their limitations for individual monitoring. In most cases, assessment of intakes of radionuclides may be achieved by body activity measurements, excreta monitoring, air sampling with personal air samplers, or a combination of these techniques. The choice of measurement technique will be determined by a number of factors including the radiation emitted by the radionuclide; the likely radiation dose; the biokinetic behaviour of the contaminant and the availability of equipment.
Routine monitoring programmes usually involve only one type of measurement if adequate sensitivity can be achieved. For some radionuclides, only one measurement technique is feasible, e.g. urine monitoring for intakes of tritium. For radionuclides, such as plutonium isotopes, that present difficulties for both measurement and interpretation, a combination of techniques may have to be employed. If different methods of adequate sensitivity are available, the general order of preference in terms of accuracy of interpretation is:
These techniques are, however, complementary and not mutually exclusive. Monitoring in relation to a particular task or event may often involve a combination of techniques so as to make the best possible evaluation of a novel or unusual situation. For example, a programme of both body activity and excreta measurements and, in some circumstances, personal air sampling may be used in combination with solubility studies on samples of airborne activity or source material from the workplace. Solubility studies will not necessarily give a good indication of the solubility characteristics of material in the lung but can provide valuable guidance for use in determining the most appropriate monitoring procedure .
In the workplace individuals may be exposed to a variety of radionuclides, as could occur in fuel reprocessing or manufacturing plants. In such circumstances it may be feasible to use a radionuclide that is readily detectable to assess the potential for exposure to other radionuclides in the plant. Thus screening for 144Ce could be used to assess the potential for exposure to actinides. Similarly intakes of particulates may be complex mixtures and indicator radionuclides could be used in any assessment. Thus 241Am may be present in inhaled fuel particles together with plutonium isotopes and external monitoring can be used to assess their intake.