Radionuclides mother

Stather JW, Harrison JD, Kendall GM. 1992. Radiation doses to the embryo and fetus following intakes of radionuclides by the mother. Radiat Prot Dosim 41(2/4) 111-118. 

Mo/"mTc Generators The essential part of the most commonly available generator system is a simple chromatography column to which the mother radionuclide is absorbed on a suitable support material. The daughter radionuclide is a decay product of the mother nuclide. Since it is the daughter nuclide that is used to label the carrier molecules, it must be possible to separate this from the parent nuclide by a chemical separation. 

The genetic correlations of the radionuclides within the families are often characterized by the terms mother and daughter . Thus, is the mother nuclide of all members of the uranium family, Ra is the mother nuclide of Rn, and so forth. 

If the half-life of the mother nuclide is much longer than those of the succeeding radionuclides (secular equilibrium), eq. (4.48) becomes much simpler, provided that radioactive equilibrium is established. As in this case At A2, A3... Aa, all terms are small compared with the first one, giving... 

These equations are the same as those derived for radioactive equilibrium between mother and daughter nuclide (eqs. (4.23) and (4.24)) i.e. in secular equilibrium the relations in section 4.4 are not only valid for the directly succeeding daughter nuclide, but also for all following radionuclides of the decay series. This has already been applied in the examples given in section 4.4. 

Application of short-lived radionuclides has the advantage that the activity vanishes after relatively short periods of time. This aspect is of special importance in nuclear medicine. Short-hved radionuclides may be produced by irradiation in nuclear reactors or by accelerators, but their supply from in-adiation facilities requires matching of production and demand, and fast transport. These problems are avoided by application of radionuclide generators containing a longer-lived mother nuclide from which the short-hved daughter nuclide can be separated. 

Table 12.10. Examples of mother and daughter nuclides suitable for use in radionuclide generators.

The main problems with application of cosmogenic radionuclides are knowledge of the production rate during the time span of interest and the possibility of interferences (e.g. by nuclear explosions). For the other methods it is important whether the systems are closed or open, i.e. whether nuclides involved in the decay processes (mother nuclides, daughter nuclides or a particles in the case of measurement of He) are lost or entering the system during the time period of interest. 

Emanation techniques are based on the production of radioactive noble gases by decay of mother nuclides or by nuclear reactions. The emanating power has been defined by Hahn as the fraction of radioactive noble gas escaping from a solid relative to the amount produced in the solid. It depends on the composition of Ihe solid, ils lallice structure and its spccihc smTace area. Reactions in the solid have a major inlluence. Further factors affecting the emanating power are the half-life of the noble gas radionuclide, its recoil energy and the temperature. 

Radionuchdes Any kind of unstable (radioactive) atoms that may differ in atomic number Z and/or neutron number N from other atoms Radionuclide generators Set-up to separate repeatedly short-lived daughter nuclides from longer-lived mother nuclides by chemical methods Radiotoxicity Toxicity of radionuclides... 

These series include mother radionuclides - radioactive isotope mih the longest half-life T j, intermediate radiogenic and radioactive isotopes and radiogenic stable isotopes. 

O Equations (40.8) and (40.9) reduce to N1/N2 - /I2//I1 and Ai = A2. In these equilibria, the daughter activity will not exceed the parent activity. This characteristic, different from the transient equilibrium shown in O Fig. 40.1, is illustrated for the Ge/ Ga radionuclide generator in Fig. 40.3. The ratio between the mother and daughter half-lives in this case is 270.8 X 24h/1.135h = 5726. 

In chronometry, the age of the sample is defined not in terms of the decay of a parent nuclide, but rather as the in-growth of a daughter activity. Radionuclides that are linked to one another by the processes of radioactive decay have relative concentrations that can be calculated with the Bateman equations, which express the simple laws of radioactive decay and ingrowth. If there exists a time at which all the descendant radionuclides have been removed from the mother material, that time can be determined through the measurement of the relative concentrations of the mother and daughter nuclides at a later time. The time interval between the purification of the sample and the subsequent analysis of the sample is defined as the age of the material at the analysis time. The technique does not apply when the half-life of the daughter nuclide involved in the determination is significantly shorter than the elapsed time. 

A device in which a daughter radionuclide with a shorter half-life is separated from a mother radionuclide with a longer half-life. 

The most important pharmaceutical radionuclide produced by a nuclear reactor is molybdenum. This element is the mother radionuclide in a Mo/ " Tc-generator (see Sect. 15.6.4). During separation in this generator sodium "technetium pertechnetate is formed. Tc-pertechnetate is the most frequently used radiochemical for coupling to a pharmaceutical ligand in the preparation of diagnostic radiopharmaceuticals. 

Radionuclide generators are loaded by the manufacturer with a mother radionuclide. This radionuclide decays continuously to a daughter radionuclide with suitable properties for the preparation of radiopharmaceuticals. These generators can be used on site for a period of a week to several months, depending on the type of generator [1,2]. 

Sometimes real time or complete quality control is not reasonably possible, especially when the radioactive dose is extremely high (e.g. loading of generators with mother radionuclide) or when the half-life of the radionuclide is very short. In those cases all feasible quality control tests are finalised after release, but always before administration to the patient. This two-step release requires a strict recall procedure in order to prevent administration when the delayed quality control results do not meet the requirements. 

The interpretation of the results of experiments performed in recent years has yielded contradictory conclusions as to the sources and the mechanisms of contamination buildup. A th one exception, the measures taken on the basis of these results have not resulted in a clear success on the contrary, in some cases a deterioration of the situation has resulted. The question as to the reasons for such consequences emerges and it seems that the failure of many attempts has mainly been due to the fact that only macrochemical aspects (e. g. effect of pH and temperature on the solubility of the corrosion product oxides) have been taken into consideration. In reality, because of the very low mass concentrations of the essential radionuclides and their mother elements in the coolant, severe deviations in behavior from that of macroamounts are to be expected, an effect which is well known in radiochemistry. In particular, in the behavior of Co and Co trace-chemical mechanisms such as surface adsorption onto oxide particles, co-precipitation together with other elements, as well as ion exchange and isotope exchange with other constituents of the corrosion product oxides can be assumed to play an important role, but in most of the investigations performed up to now these have not been considered. 

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