Research for superheavy elements in hafnium ores

The natural radioactivity of chloride sublimates formed during chlorination and subsequent thermochromatographic separation (300-1050 deg C) of hafnium dioxide and of a hafnium-zirconium mineral concentrate was studied. The natural radioactivity was supposed to be due to the superheavy elements in the investigated samples. Under the experimental conditions the volatility of all chlorides--except for that of the superheavy metals--is so high, that the assumption can be held as admissible. The results indicate that if superheavy elements are present in the investigated minerals, their concentration is less than 2.5x10-13 g.g-1 and 0.3x10-13 g.g-1, respectively. (T.F.)