Carrier free radionuclide

Table III. Carrier-Free Radionuclide Starting Concentrations...

The volatilization and deposition of carrier-free radionuclides of the elements Re, Os, Ir, Mo, Tc, and Ru in a thermochromatography column were studied using air as a carrier gas [83]. The columns were filled with quartz powder (200 fim). Os was completely volatilized and adsorbed at -40 °C. The deduced enthalpy of adsorption on the quartz surface was -A//a°(OsO4)=50 5 kJ/mol. Ru was deposited at much higher temperatures around 400 °C and identified as Ru03. Later, in different online TC experiments consistently values for -A//a°(0s04) between 39 and 41 kJ/mol were determined [79, 85, 96]. 

An important application of isotope dilution in radiochemistry is the determination of a radionuclide by dilution with an inactive nuclide (inactive compound), also called reverse isotope dilution. This apphcation is very valuable if the radionuclide is present in carrier-free form. Again, quantitative separation is avoided a measured amount mi of an inactive isotope of the element to be determined is added and after a non-quantitative separation the amount m2 is measured. The ratio wa/wi is the yield of the separation procedure and the activity of the carrier-free radionuclide (Ax = 0) is obtained from the measured activity A2 ... 

The specific activity of a carrier-free radionuclide can be calculated by... 

A carrier-free radioactive sample is usually one in which the radionuclide is not diluted with isotopic atoms. In reactor production of Na from target Na, each Na is diluted with a large number of Na atoms. Na cannot be made carrier-free in a reactor. If a carrier-free radionuclide has been produced, e.g. through accelerator irradiation, which thm must be purified, its concentration is so low that it may not follow the normal chemical rules. A macroscopic amount of carrier, either isotopic or not, may have to be added to carry the radionuclide through the proper chemical purification steps. We discuss this further in 9.2. 

Table 4 Some examples for ifie mass of 10 Bq of carrier-free radionuclides ...

Table 4 gives some figures for the mass of carrier-free radionuclides with an activity of 10 Bq. 

After addition of a nonisotopic carrier material (the same chemical compoimd of an element with similar chemical behavior of the radionuclide), the radionuclide and the carrier show the same chemical behavior only in some chemical procedures. This can be used for separation processes. Later on the radionuclide can be separated from the nonisotopic carrier material by specific chemical separation procedures and recovered as a carrier-free radionuclide. Using this radiochemical method Marie Curie discovered radium by first using the nonisotopic carrier barium and finally isolating radium from barium by separately crystallizing barium and radium bromides. 

The term specific activity (activity per unit mass) is important for radiochemical methods like isotope dilution. Samples of carrier-free radionuclides have the highest possible specific activity for this radionuclide. By the addition of carrier material the specific activity is lower, the total amount of material (stable and radioactive materials) is increased, and some handling procedures, like precipitation, might be easier. The change of specific activity is the basis of isotopic dilution techniques. 

Eichler, B., Kratz, J.V. Electrochemical deposition of carrier-free radionuclides. Radiochim. Acta 88, 475-482 (2000)... 

Electromigration of carrier-free radionuclides. 5. Ion mobilities and hydrolysis of Np(V) in aqueous perchlorate solutions. Radiochim. Acta, 42, 43-46. Runde, W. and Kim, J.L (1994) Chemical Behaviour of Trivalent and Pentavalent Americium in Saline NaCl-Solutions. Studies of Transferability of Laboratory Data to Natural Conditions. Report RCM-01094, Technische Universitat Miinchen, 236 pp. Runde, W., Neu, M.P., and Clark, D.L. (1996) Neptunium(V) hydrolysis and carbonate complexation experimental and predicted neptunyl solubility in concentrated NaCl using Pitzer approach. Geochim. Cosmochim. Acta, 60, 2065-2073. 

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