Pu(IV) oxyhydroxide colloid growth is investigated with XAFS and LIBD. From combined results a model of colloid formation is proposed, which leads to a face-centered cubic Pu sublattice having cation defects, as observed with EXAFS, and a linear dependency of log [Pu(IV)] on -log [H+] with slope -2, in accord with LIBD. The solubility for Pu(IV) measured with LIBD is close to the lower limit of the solubility curve from previously reported data.

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The first dataset of 236 U/ 238 U in the water column of the Arctic Ocean (AO) is presented and shows the widest range of ratios reported so far in the open ocean, from (5±5) to (3840±260) ×10-12. Surface samples and depth profiles were collected during two GEOTRACES expeditions in 2011-2012 and analyzed for the concentrations of 236 U and 129 I, with the aim of investigating whether the combination of 236 U/ 238 U and 129 I/ 236 U can be used as a new oceanographic tool in the AO. Results show that the distributions of the 236 U/ 238 U and 129 I/ 236 U atomic ratios are consistent with the different water masses in the AO. High 236 U/ 238 U and 129 I/ 236 U ratios in the upper water column (>2000 ×10-12 and >200, respectively) illustrate the penetration of Atlantic waters (AW) into the AO. Lower values were found in Pacific waters (PW) and deep waters of the AO. Rivers seem to represent a temporally and spatially-constrained third anthropogenic source of 236 U but more data is needed to confirm this. In a simple

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Since its inauguration in 2005, the INE-Beamline for actinide research at the synchrotron source ANKA (KIT North Campus) provides dedicated instrumentation for x-ray spectroscopic characterization of actinide samples and other radioactive materials. R&D work at the beamline focuses on various aspects of nuclear waste disposal within INE's mission to provide the scientific basis for assessing long-term safety of a final nuclear waste repository. The INE-Beamline is accessible for the actinide and radiochemistry community through the ANKA proposal system and the European Union Integrated Infrastructure Initiative ACTINET-I3. Experiments with activities up to 1 × 10(+6) times the European exemption limit are feasible within a safe but flexible containment concept. Measurements with monochromatic radiation are performed at photon energies varying between ~2.1 keV (P K-edge) and ~25 keV (Pd K-edge), including the lanthanide L-edges and the actinide M- and L3-edges up to Cf. The close proximity of the INE-Beamline to INE controlled area labs offers infrastructure unique in Europe for the spectroscopic and microscopic characterization of actinide samples. The modular beamline design enables sufficient flexibility to adapt sample environments and detection systems to many scientific questions. The well-established bulk techniques x-ray absorption fine structure (XAFS) spectroscopy in transmission and fluorescence mode have been augmented by advanced methods using a microfocused beam, including (confocal) XAFS/x-ray fluorescence detection and a combination of (micro-)XAFS and (micro-)x-ray diffraction. Additional instrumentation for high energy-resolution x-ray emission spectroscopy has been successfully developed and tested.