Leachability of radium from ‘mixed cake’ solid waste from monazite processing

Abstract
The ‘mixed cake’ solid waste obtained from monazita processing contains Ra‐228 as the major radiomaclide contaminant. Experiments carried out in the laboratory, simulating natural conditions, estimate the readily leachable fraotion of Ra‐228 in the cake to be about 5% of its total activity. The leaching of Ra in steady state is a function of the solubility of BaSO4 which is a constituent of the cake. Fixing the cake in cement concrete reduces leachability of activity by 2 to 4 orders of magnitude. The leachates in this experiment show Ra‐228 levels comparable with its Derived Limit in drinking water.