Gmelin S Handbook Of Inorganic Chemistry And Isotopes

In connection with the recent treatment of radium and the actinides, the Gmelin Institute is carrying out the description of thorium and its compounds. The supplement volume A 2 comprising the history, isotopes and the recovery of thorium and the supplement volumes C 1, C 2 and C 3 describing the compounds with the noble gases, hydrogen, oxygen compounds and nitrogen compounds have already been published; also published is supplement volume C 5 describing the compounds with sulfur, selenium, tellurium, and boron. The supplement volume D 1 and D 2 describing the properties of thorium ions in solution and the solvent extraction of thorium, as well as supplement volume E describing the coordination compounds have also been published. The present volume deals with the technical fabrication of important thorium compounds and their uses in the nuclear and non-nuclear fields. It also describes in detail the behavior of thorium nuclear fuels during operation of a nuclear power plant as well as the reprocessing of burnt-up thorium fuels. By far the most important Th compound is ThO2 due to its high chemical and thermal stability as well as its high melting point near 3000°C, the highest for any metal oxide. The inherent radioactivity of 232Th and the formation of radioactive daughter products are important limiting factors in the technical scale use of thorium compounds because of necessary radiation protection measures and of health physics. 232Th is transformed by neutrons to the fissile uranium isotope 233U. Thorium therefore is an excellent breeding material, especially for high-temperature reactors. A lot of basic and technical investigations for reprocessing of spent thorium fuel have to be done; no such reprocessing plants exist as yet.

Astatine is - besides radon and francium - the only natural radioelement which only has short-Lived isotopes, thereby excluding experiments with . . weighable" amounts of the element. This implies that all available data on physics and chemistry of this element are 12 16 based on experiments on the tracer scale with 10- to 10- g - and this will also not change in future because no longer-Lived isotopes as yet known are to be expected. Due to the fact that the only isotope of At occurring in the natural decay series, 219At, results from the 0. 005% a-branching of 223Fr which itself is produced by the only 1. 38% a-branching of 227 Ac - a member of the 235U series - there is no chance to recover substantial amounts of 219At from natural sources for sCientific research of At. All studies, therefore, are being done with the isotopes 209At to 211At having half-lives in the few hours region and being obtained by irradiation of bismuth with a-particles via (a,xn) reactions or by proton irradiation of heavy elements via spallation reactions. The mostly used isotope is 7. 22 h 211At. The fast separation of the obtained At isotopes is no very difficult procedure and is either being done by wet adsorption-precipitation techniques or making use of its high volatility by destilling in air.