Nuclear microprobe applications to radioactive waste management basic research

Radioactive waste management is one of the major technical and scientific c hallenge to be solved by industrialized countries near the beginning of the 21st century. Relevant questions arise about the extrapolation of the long term-behavior of materials from waste package, engineered barriers and nea r field repository. Whatever the strategical option might be, wet atmospher e or water intrusion through the different barriers constitute the two main remobilization factors for radionuclides in the geosphere and the biospher e. The study of solid alteration processes and elemental sorption phenomena on mineral surfaces is one of the most efficient basic research approaches to assess the long term performance of waste materials. Ion beam analysis and more recently nuclear microprobe techniques have been applied to invest igate exchange mechanisms near representative solid/liquid interfaces such as glass/deionized water, uranium dioxide/granitic or clay water or mineral surface/aqueous solution doped with chemical elements analogue to actinide or fission products. This paper intends to describe the different works th at have been carried out in Saclay using the nuclear microprobe facility. T he coupling of mu RBS, mu PIXE and mu NRA permits to determine the evolutio n of the surface composition induced by chemical reactions involved. Comple mentary observation of solid morphology and solution analysis allows to obt ain a complete elemental balance on exchange processes. (C) 1999 Elsevier S cience B.V. All rights reserved.