Leaching of 137Cs and 90Sr contaminated soils by FeCl3 and NH4Cl solutions

The leaching of Cs-137 and Sr-90 radionuclides contaminated soils by solutions of FeCl2 and NH4Cl in batch (static), column (continuous-ftow) and field (Chernobyl region) experiments is investigated. The eluent solution is a 1:1 mixture of 0.01-0.02 mol l(-1) FeCl3 and NH4Cl. The equilibrium distribution coefficients of Cs-137 and Fe3+ between a Chernobyl sandy loam sample and the eluent are determined to be 25 and 3800, respectively. The first order rate constants of ion exchange reactions for the 0.01M eluent were 10(-6) s(-1) for Cs-137 and 10(-4) s(-1)' for Sr-90. In the Chernobyl region, a 10x10m plot with radioactivity up to 2000 Mbq km(-2) (50 Ci km(-2)) was selected for decontamination by an 'in situ' leaching technology der eloped within the plot. For example, the leaching time to 30-40% residue radioactivity to a depth of at least 0.5 m is 15 days; in addition, the consumption of the eluent is 3-4 m(3) m(-2) for Cs-137 and 1.5-2 m(3) m(-2) for Sr-90, at a flux of 8-10 1 h(-1) m(-2).