Processing, radionuclides generated

In the process of calibrating a radionuclide generator, 18.4 GBq activity was shown for a radioisotope. Express this in millicuries. 

A typical radionuclide generator consists of a column filled with adsorbent material in which the parent radionuclide is fixed. The daughter radionuclide is eluted from the column once it has grown as a result of the decay of the parent radionuclide. The elution process consists of passing through the column a solvent that specifically dissolves the daughter radionuclide leaving the parent radionuclide adsorbed to the column matrix. 

The sources of ionizing radiation are nuclear power plant, nuclear material processing, and radionuclide generation for nondestructive purposes. Medical and chemical laboratories use these radionuclides—for example, iodine, thallium, and barium—as tracers. The danger of mishandling these materials could cause release of these materials into the environment. Other than medical diagnostic tests for fracture of bones and constriction of blood vessels, these are used for the treatment of cancers. 

Mo is separated from other radionuclides generated by this process (Barnes and Boyd 1982). Strict limits for radionuclidic impurities are stated in the monograph on sodium pertechnetate [ Tc] injection solution (Council of Europe 2005 a). 

A third source for radionuclide generator systems is the recovery of radioactive parents from extinct radioactive decay processes, such as Th, which is recovered from decay products. The Th represents a convenient, long-lived iT i = 7,340 years) source from which Ac is recovered, which is the parent of the Ac/ Bi generator system. 

The potentially important role of colloidal species in the geochemical behaviour of the polyvalent actinides has nevertheless been stated by various authors (e.g., Kim 1991 Kersting et al. 1999). The present paper discusses the role of colloids on the release of radionuclides from a nuclear waste repositoiy with regard to the processes leading to (1) colloid generation and stability (2) radionuclide interaction with aquatic colloids and (3) colloid-borne radionuclide migration. 

A generator should ideally be simple to build, the parent radionuclide should have a relatively long half-life, and the daughter radionuclide should be obtained by a simple elution process with high yield and chemical and radiochemical purity. The generator must be properly shielded to allow its transport and manipulation. 

This was the first man-made radionuclide. From that time on many species of radionuclides were produced by bombardment of elements with charged particles using the various types of accelerators. In addition, practical use of fission energy allowed production of a great amount of artificial radionuclides, not only by neutron irradiation generated with nuclear reactors, but also by processing spent fuel. 

The third means of radionuclide production involves target irradiation by ions accelerated in a cyclotron. One example of this approach is provided by the production of Ge, which decays with a 280 day half-life to the positron emitter Ga. Proton irradiation of Ga produces Ge in a (p,2n) reaction. After dissolution of the target material a solution of the Ge product in concentrated HCl is prepared and adsorbed on an alumina column which has been pre-equilibrated with 0.005 M EDTA (ethylenediaminetetraacetate) solution. The Ga daughter may then be eluted using an EDTA solution in a system which provides the basis of a Ga generator. Cyclotron production of radionuclides is expensive compared with reactor irradiations, but higher specific activities are possible than with the neutron capture process. Also, radionuclides with particularly useful properties, and which cannot be obtained from a reactor, may be prepared by cyclotron irradiation. In one example, cyclotron produced Fe, a positron emitter, may be used for bone marrow imaging while reactor produced Fe, a /3-emitter, is unsuitable. " ... 

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