caa a22 4500 37892723X CHVBK 20180305123620.0 cr unu---uuuuu 161128e20041101xx s 000 0 eng 10.1524/ract.92.9.765.54973 doi (NATIONALLICENCE)gruyter-10.1524/ract.92.9.765.54973 Results of the colloid and radionuclide retention experiment (CRR) at the Grimsel Test Site (GTS), Switzerland - impact of reaction kinetics and speciation on radionuclide migration [Elektronische Daten] [Horst Geckeis, Thorsten Schäfer, W. Hauser, Thomas Rabung, T. Missana, C. Degueldre, A. Möri, J. Eikenberg, Th. Fierz, W. R. Alexander] The influence of smectite colloids on the migration behaviour of U(VI), Th(IV), Pu(IV), Am(III), Np(V), Sr(II) and Cs(I) is investigated within the Colloid and Radionuclide Retardation experiment (CRR). Two in situ experiments in a well-characterized granitic fracture zone are carried out in presence and absence of bentonite colloids. Radionuclide retardation observed in the field studies increases in the sequence Np(V)∼U(VI)<Sr(II)<Cs(I), where a small fraction of colloid borne breakthrough is only stated for Cs(I) in presence of bentonite colloids. Am(III) and Th/Pu(IV) mainly migrate as colloids without retardation in the presence and absence of smectitic colloids. The radionuclide migration behaviour is discussed on the basis of results obtained in laboratory batch sorption experiments and spectroscopic studies. Consistent with the field observation, laboratory derived Kd values increase in the order Np(V)∼U(VI)<Sr(II)<Cs(I). Significant kinetic hindrance for the sorption to fault gauge minerals is observed for Sr(II) and Cs(I), but notably for Am(III) and Pu(IV). The slow sorption reaction of tri- and tetravalent actinide ions is explained by their kinetically hindered dissociation from colloidal species. In order to explain the colloidal behaviour of tri- and tetravalent actinides even in absence of bentonite colloids, ultracentrifugation and spectroscopic experiments are performed. It is found that up to 60% of Pu(IV) and Am(III) species can be centrifuged off. Adding Cm(III) (5×10-8mol L-1) into both injection solutions instead of Am(III) allows for a spectroscopic study by using the time resolved laser fluorescence spectroscopy (TRLFS). Peak position and fluorescence lifetimes (λ=604nm, τ=110-114μs) together with the fact that Cm(III) can be widely separated by ultracentrifugation, suggest the existence of inner-sphere surface complexes on groundwater and bentonite colloids. Carbon K-edge XANES analysis of the bentonite colloids reveal the presence of natural organic constituents. They are mainly of aliphatic nature containing high fractions of carboxylate groups. A contribution of these organic species towards the bentonite colloid stability and sorption of actinides is assumed to be likely. © 2004 Oldenbourg Wissenschaftsverlag GmbH Laboratory techniques, experiments nationallicence Analytical chemistry nationallicence Inorganic chemistry nationallicence Geckeis Horst aut Schäfer Thorsten aut Hauser W. aut Rabung Thomas aut Missana T. aut Degueldre C. aut Möri A. aut Eikenberg J. aut Fierz Th aut Alexander W. R. aut Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 92/9-11/2004(2004-11-01), 765-774 0033-8230 92:9-11/2004<765 2004 92 ract https://doi.org/10.1524/ract.92.9.765.54973 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1524/ract.92.9.765.54973 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Geckeis Horst aut NATIONALLICENCE 700 1- Schäfer Thorsten aut NATIONALLICENCE 700 1- Hauser W. aut NATIONALLICENCE 700 1- Rabung Thomas aut NATIONALLICENCE 700 1- Missana T. aut NATIONALLICENCE 700 1- Degueldre C. aut NATIONALLICENCE 700 1- Möri A. aut NATIONALLICENCE 700 1- Eikenberg J. aut NATIONALLICENCE 700 1- Fierz Th aut NATIONALLICENCE 700 1- Alexander W. R. aut NATIONALLICENCE 773 0- Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 92/9-11/2004(2004-11-01), 765-774 0033-8230 92:9-11/2004<765 2004 92 ract CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter