An examination of new procedures for fractionation of plutonium- and americium-bearing sediments

Sediment from the Ravenglass estuary has been fractionated by procedures which might be expected to bring about no change in the chemical forms of the bound plutonium and americium. The action of molten N-methylmorpholine-N-oxide (NMMNO) on the sediment extracts 20% of the ²³⁹Pu and ²⁴¹Am, possibly in forms associated with humic-like materials. On dialysis, these extracts appear to lose 40% of the ²³⁹Pu and 20% of the ²⁴¹Am. However, on pretreatment with base there is no significant loss of radioactivity on subsequent dialysis and this may indicate the existence of cationic forms of these elements. High gradient magnetic separation (HMGS) has fractionated the clay constituents (<0.2 μm and 0.2-2.0 μm) into three subfractions. From an analysis of the ²³⁹Pu/²⁴¹Am ratio it would appear that there is no conservation of isotopic ratios; this might indicate that the environmental forms of ²³⁹Pu and ²⁴¹Am exhibit markedly different affinities for the organo-mineral phases of the sediment.