Radium partitioning and physical separability in multiphase NORM oily sludges: a radiochemical framework for centrifugal treatment

Abstract Naturally occurring radioactive material (NORM) oily sludges are heterogeneous multiphase systems in which radiochemical partitioning does not necessarily translate into physical separability. This review critically compares reported radium distributions, host phases and oily-sludge separation studies and proposes a coupled framework combining the apparent distribution coefficient, K d , with a radium-bearing-solids recovery efficiency, η s . Quantitative evidence shows strong but matrix-dependent radium association with sulfate solids, while fine particles, colloids and emulsions can limit recovery. Isotope-specific activity-balance closure is proposed as a primary criterion for evaluating centrifugal volume reduction and its limitations.