[en] This paper summarizes the recent activities in the research programme ''Geochemistry of Long-Lived Transuranic Actinides and Fission Products''. The following three important geochemical processes have been studied under laboratory conditions: dissolution of neptunium dioxide in aqueous solution; sorption of neptunium on naturally-occurring iron-containing minerals; alteration of chlorite and its relevance to the uranium redistribution in the vicinity of the ore deposit

[en] Uranium ore bodies in the Alligator Rivers Uranium Province in Australia have been studied since 1981 as analogues of radioactive waste repositories. The main objectives were to understand the processes governing the migration of radionuclides, particularly uranium- and thorium- series radionuclides, under groundwater flow, to develop and test models to describe this migration, and to demonstrate the applicability of the results to the safety analysis of radioactive waste repositories

[en] The migration behaviour of transuranic elements Np, Pu, Am and Tc has been studied by static and dynamic experiments under aerobic as well as anaerobic (N₂ + 3% H₂) conditions for the geological samples from Gorleben aquifers (Germany) and also for the glauconite mineral. The geochemical parameters varied are: pH from 5 to 7, Eh by addition of SnCl₂ or hydrazine and salinity with NaCl concentration from 0.01 to 3.0 M

[en] The programme, of which the results were discussed in this document, has been implemented in close co-operation with another Co-ordinated Research Programme of the Agency, namely F2.30.06 - Nuclear techniques in the study of pollutant transport in the environment: interaction of solutes with geological media (methodological aspects). The main goal of this CRP is the elaboration of nuclear techniques for laboratory and field determinations of pollutant migration mechanisms and those characteristics of geological media and pollutants which control environmental mass transfer. Isotope tracer methods, and to a lesser degree nuclear well logging, are being elaborated and evaluated within the framework of the programme

[en] The calculation of the natural production of long-lived radionuclides has been studied. Long-lived radionuclides (¹²⁹I, ⁹⁹Tc, ⁸¹Kr, ³⁶Cl, ²³⁹Pu, ²³⁷Np, ¹⁴C) are constantly produced in underground rocks by various nuclear processes such as reactions with neutrons or with alpha particles and also spontaneous fission of ²³⁸U. Calculation of natural production of radionuclides requires information on the chemical composition of the rock and various physical parameters

[en] A speciation of the chemical state of actinides in groundwater is an essential prerequisite for a better understanding of their migration phenomena in a given aquifer system. This exercise, however, demands a direct speciation method of high sensitivity which corresponds at least to the solubility range of actinides in groundwater. For this purpose, a number of highly sensitive spectroscopic methods have been developed in our laboratory, using laser as a powerful light source, and applied to the speciation of aqueous actinides in the submicromolar range: from 10^-6 mol/L to 10^-12 mol/L. Three different spectroscopic methods are briefly described in this paper

[en] Beijing Research Institute of Uranium Geology has carried out a research programme of deep underground disposal for high-level radioactive wastes sponsored by the China National Nuclear Corporation (CNNC) since 1985. Analogue studies have been focused on bentonite as a buffer material. Evaluation of a uranium ore body in granite as an analogue of a radioactive waste repository was commenced last year under the support of CNNC and IAEA

[en] The initial natural analogue studies at the Cigar Lake uranium deposit were reported at the first RCM in 1988 and additional work has been undertaken since 1989 in co-operation with the Swedish Nuclear Fuel and Waste Management Co. (SKB). Field and laboratory work was carried out on samples of ore, host rock and groundwater and cores from a new drillhole through the ore zone were examined in detail. Two new samples (CS-615 and CS-620) were analyzed by a number of methods including X-ray Photo-electron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), chemical and instrumental analysis. Analysis of plutonium-239, iodine-129 and technetium-99 were carried out at Los Alamos National Laboratory (LANL), as well as iodine-129 at the University of Toronto

[en] Natural plutonium is exclusively the product of uranium neutron capture. The rate of natural plutonium production is a function of the uranium concentration and the fluence and energy spectrum of neutrons in the rock. In natural systems that have been closed to the loss and/or gain of plutonium and uranium for several half-lives of the radioactive product ²³⁹Pu - about 10⁵ years - the two actinide elements attain a state of secular equilibrium. In such a state the Pu/U ratio is proportional to the plutonium production rate

[en] It is now well-recognized that the study of natural geochemical systems can help us to gain a better understanding of the different processes of radionuclide mobilization, transport and retardation in the far field, and provide a means of testing the thermodynamic databases and transport codes which underpin performance assessments of radioactive waste repositories. The British Geological Survey has been carrying out a programme of natural analogue studies of radionuclide migration at four sites: the sediments of Loch Lomond, Scotland, and the sediments at Broubster in Caithness, N Scotland, at Needle's Eye near Dalbeattie, SW Scotland, and at the disused South Terras mine, near St. Stephan, Cornwall. In various ways these post-glacial sediments have played host to the transport and retardation of U/Th decay series isotopes, rare earth elements and iodine over long time-scales and over distances up to 100 m or more