DETERMINATION OF PLUTONIUM IN ENVIRONMENTAL-SAMPLES BY CONTROLLED VALENCE IN ANION-EXCHANGE

The title method was successfully used for collecting Pu-239, Pu-249 f rom 200 litres of seawater by coprecipitation with 16 g FeSO4 . 7H2O u nder reducing conditions without filtering. The plutonium is leached b y concentrated HNO3 + HCI from the coprecipitate and the solid particl es. The precipitate is heated at 400-degrees-C and digested in aqua re gia. Na2SO3 and NaNO2 have been applied to obtain the Pu4+ valence sta te in 0.571 N HN03 for different samples. Plutonium and thorium are co adsorbed on anionic resin from 8N HN03. The column is eluted with 8N H N03 containing fresh NaNO2 to keep the Pu4+ state for uranium decontam ination. The system of the column is changed from 8N HNO3 to concentra ted HCl with 50 ml concentrated HCI containing a few milligrams of NaN O2. Further decontamination of thorium was achieved by elution with co ncentrated HCI instead of 9N HCl. The plutonium is successfully stripp ed by H20, NaOH, 2N HNO3 and 0.5N HNO3 containing 0.01M NaNO3. The che mical yield of plutonium for a 200 l seawater sample is 60-80%. The re solution of the electroplated thin source is very good.