Impurity atoms from nuclear reactions

Impurity atoms resulting from nuclear reactions. Their influence on the properties of a solid is generally very similar to that of the same impurities introduced in a chemical way. Only thermal neutrons are able to produce them in any appreciable amount even in this case, and as far as the irradiated material does not contain elements with a large cross section, like boron-10 or lithium-6, the concentration of the produced impurities quite generally remains negligible. 

A French radioisotope production group provided radionuclides such as Cr, Fe, Cu, Zn, and As by the Szilard-Chalmers processes (Henry 1957). At the Japan Atomic Energy Research Institute, this process was applied to obtain pure from neutron-irradiated potassium phosphate. Ordinary products using (n,p) reaction in a nuclear reactor contain an impurity isotope P in P, but P produced by (n,y) reaction in neutron-irradiated phosphate does not contain P. Hot atom chemically obtained P by (n,y) reaction was therefore appropriate for some special experiments in which contamination of P with different half-life and P-particle energy had to be excluded (Shibata et al. 1963). 

Despite this favorable record, the further development of nuclear power is greatly handicapped in many countries because of public concern over the radioactive products arising in the course of plant operation and the consequences of their possible release to the environment. Energy generation from the neutron-induced fission of heavy atoms is inevitably accompanied by the formation of radioactive nuclides. This is, first of all, the direct consequence of nuclear fission, which leads initially to fission products that are unstable due to an excess of neutrons in the newly formed nuclei. These products are transformed by a sequence of p decays (mainly with associated y emission) to stable end products. Moreover, neutron capture in the heavy atoms of the fuel results in the buildup of nuclei which are heavier than those of the starting element (uranium, plutonium) and which mostly decay — in part, with very long halflives — by a emission. Finally, from elements present in structural and cladding materials, as well as in the coolant, its additives and impurities, additional radionuclides are formed, induced by neutron capture reactions which take place in the intense neutron field inside the reactor pressure vessel. 

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