Short-lived Radionuclides and the Role of Carriers

The most important aspects of the chemistry of short-lived radionuclides are that 

Radionuclide Half-life Number of atoms Mass [g] Concentration if dissolved in 10 ml [mol/1] 

As already mentioned in section 12.3, carriers are elements or compounds, respectively, with identical or very similar chemical properties to the radionuclide. With respect to the suitability as carrier, the chemical state is decisive. Carriers are often added to ensure normal chemical behaviour of radionuclides. For that purpose, they must be in the same chemical state as the radionuclide considered. 

In the case of radioisotopes of stable elements, such as Co, and Na, small amounts (traces) of these elements are always present, due to their ubiquity. The masses are, in general, higher than the masses of short-lived radioisotopes, and the omnipresent traces act as isotopic carriers of the short-lived radionuclides, provided that they are in the same chemical state. In the case of isotopes of radioelements, such as Ra, Ac, Po, Md or Lr, however, stable nuclides are absent and the masses of the radionuclides are identical with the masses of the elements, provided that the presence of longer-lived radioisotopes can be excluded. 

Traces of elements or compounds, respectively, of other elements with similar properties may serve as non-isotopic carriers for radioisotopes of stable elements as well as for isotopes of radioelements. The influence of non-isotopic carriers depends on the nature of the compounds and the chemical operation. For example, in precipitation reactions, non-isotopic carriers or hold-back carriers, respectively, may play a major role. 

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