The Chemistry of Americium. IV. The Stability of Am(V) and Am(VI) in Nitric Acid Solutions and in the Solutions Containing Ozone Gas Fluoride, or Phosphate Ions

The coprecipitation technique with BiPO4 and ThF4 was applied to studying the stability of Am(V) and Am(VI) at concentrations lower than 10−6 M. It was found that 241Am(V) and 241Am(VI) were rapidly reduced to 241Am(III) in nitric acid solutions at low acidities and at high temperatures, but the reduction was effectively inhibited by the presence of ozone gas or fluoride ions. On the other hand, 243Am(V) and 243Am(VI) were found to be rather stable in nitric acid solutions, while they were readily reduced to 243Am(III) in phosphate solutions in the same manner as 241Am(V) and 241Am(VI).