DECONTAMINATION OF RADIOACTIVE TUNGSTEN-THORIUM SCRAP

摘要

In Krefeld, Germany, Siempelkamp operates a melting plant to treat steel scrap contaminated with natural radioactivity, mercury or other chemical and toxical substances. The so called GERTA plant is licensed according to the German BImSchG (federal law on protection against environmental pollution). The facility is equipped with a net frequency induction furnace and has an annual capacity of 2,000 t. The purpose is to produce a final metal product, which is completely free of all contamination ready for use in the steel cycle without any limitations. So far, more than 90% of the input consisted of carbon steels with contamination of Ra-226 as main nuclide from natural uranium decay, elementary mercury from oil and gas industry or mercury from chlorine electrolysis. In a recent project, over 130 t of tungsten and molybdenum alloyed with thorium oxide from the welding electrodes production have been successfully decontaminated and converted into a Fe-W-Mo alloy, which could be sold as a high value product. This paper gives a closer view to the "tungsten project" in terms of metallurgy, radiation protection and legislation.