Basic Research Needs on Physical Chemistry of Radionuclides in the Nuclear Fuel Cycle

Abstract

AbstractFrom uranium-ore treatment to spent fuel recycling, waste treatment and conditioning and to final storage of waste packages, radionuclides are involved in numerous chemical and physical reactions. The understanding of their chemical forms (speciation) and behavior as well (retention, complexation,...), as a function of the environment conditions (T, P, solid/liquid/gas interfaces), are key issues for the development of the industrial nuclear activities. Dedicated analytical tools are needed to determine the radionuclide concentrations and speciation in the liquids, solids and gas, over a wide range of concentrations and matrixes. The obtained experimental data on radionuclide speciation are integrated in dedicated data bases, supporting various models used to simulate the system behavior (i.e. RN migration under geological disposal, RN contamination in the primary fluids of nuclear power plants, RN behavior in the PUREX process, etc.). There are several needs in the following domains of the fuel cycle :♦ The development of innovative methods to enhance analytical performances of isotopic composition of elements in irradiated fuels or waste streams arising from processed spent fuels. Isobaric interferences may be suppressed by specific ion-molecules reactions in collision/cell coupled with Mass Spectrometer, instead of preliminary chromatographic separations.♦ The thermo chemistry at high temperature and pressure of the coolant fluids of the nuclear power plants, to model the solid/liquids interactions controlling its contamination by the activated products and hideout processes.♦ The development of scientific and operational models of the radiolysis of organic molecules and materials, under extreme conditions (γ and α radiolysis), to understand the controlling long-term degradation phenomena ( i.e. H2 degassing in the waste packages).♦ The fundamental understanding of sorption processes of redox sensitive elements such as U on specific mineral surfaces, in the presence of organic molecules, to develop dedicated tools for radionuclide monitoring and measurement in the environment.