Evaluation of homogeneity of radioactive waste forms: Statistical criteria

A set of statistical tests is proposed to evaluate the homogeneity of radioactive waste forms. These criteria were applied to cemented wastes forms by using natural thorium and uranium compounds as tracers simulating insoluble and soluble wastes, to evaluate the chemical homogeneity of the final product. The concentration of tracers in the samples were measured by using the delayed neutron counting technique which allows for the determination of uranium and thorium simultaneously. The same set of statistical tests can be applied to evaluate the homogeneity of all chemical and physical quantities necessary to characterize the waste forms (e.g., compressive strength, density, permeability, porosity, leaching rate, thermal conductivity, etc.). the possible influence of the water to cement ratio, (WIC), and salt contents in the waste stream was also investigated. The mixing technique used to produce the cemented waste forms proved to be good enough as a standard method to obtain a homogeneous product.