Database / Thermodynamic equilibrium constants / RadionuclidesSummary. The Nagra/PSI Chemical Thermodynamic Data Base has been updated to support performance assessments of the planned Swiss repositories for radioactive waste. The update from version 05/92 to 01/01 involved major revisions for most of the actinides and fission products. Altogether, more than 70% of the database contents have been revised. Data for U, Np, Pu, Am and Tc recommended by the NEA TDB project were considered in the update. Thermodynamic data for Th, Sn, Eu, Pd, Al, and solubility and metal complexation of sulphides and silicates were extensively reviewed. Data for Zr, Ni and Se were examined less rigorously as these elements are currently being reviewed in phase II of the NEA TDB project. Our experiences from this two year team effort can be summarised as follows. Detailed in-house reviews and critical appraisal of NEA recommendations greatly improved the chemical consistency and quality of the selected data. On the other hand, we could discern major gaps in the data, especially missing carbonate complexes. In some systems, e.g. Th(IV)-H 2 O and U(IV)-H 2 O, experimental data could not be described by a unique set of thermodynamic constants. There, a pragmatic approach based on solubility data was chosen for application to performance assessment. The electronic version of our database and information concerning its full documentation is available on our PSI web site (http://www.psi.ch/les).

A comprehensive literature review of thermodynamic data for compounds and complexes of actinides with oxalate, citrate, ethylenediaminetetraacetate (edta) and a-isosaccharinate has been carried out within the scope of the Thermodynamic Data Base project of the Organisation for Economic Co-operation and Development e Nuclear Energy Agency (OECD/NEA). Reliable values could be selected mainly for Am(III), Np(V) and U(VI) complexes, whereas serious data gaps were found for the tetravalent actinides. The redox states U(III), U(V), Pu(V), Am(V), Np(VI), Pu(VI) and Am(VI) are unstable in the presence of the selected organic ligands. Missing or unreliable data in these unstable redox states are of no importance from the viewpoint of application in environmental modelling studies. To cite this article: W.

Abstract. -We present an atlas of high-S/N , high-resolution (∆v ≤ 6 km s −1 ) data of Be star emission and shell profiles. We have collected profiles of Hα and of Fe ii, mostly of the λ5317 transition. These lines have been selected to provide measures for the overall emission strength and for the velocity field in these disks. We have collected data for 77 southern and equatorial programme stars, covering the period 1982-1993. This is the most comprehensive overview of profile shapes in Be disks. We propose a three-dimensional scheme in which most observed profiles can be classified. The parameters are i) inclination, ii) optical depth, and iii) the pattern of the velocity field. A search for short-term variability (timescales between five days and a few minutes) in six stars ended with negative result. Shortest observed timescale for variability is a few days for well-developed disks in binary systems (HR 1910, HR 2142.

Within the scope of the OECD Nuclear Energy Agency (NEA) Thermochemical Data Base Project (TDB) a comprehensive review of selected organic ligands has been carried out by the authors. The selected ligands are oxalate, citrate, ethylenediaminetetraacetate (edta) and α-isosaccharinate (isa), and the elements considered in the review are U, Np, Pu, Am, Tc, Ni, Se and Zr, as well as the necessary basic data concerning protonation of the ligands and interactions with the major competing elements Na, K, Mg and Ca. This review on organic ligands showed that the pragmatic ionic strength correction procedure, the Specific ion Interaction Theory (SIT), chosen as the default method for all NEA TDB reviews, can be applied successfully also to organic ligands. The SIT interaction parameters derived from ligand protonation data for different media, e.g. NaCl and KCl, pass the consistency test when applied to other systems evaluated in the organics review, e.g. solubility data. Hence, the thermodynamic constants selected in this NEA TDB organics review can be used with some confidence in real world applications, provided that SIT is used in the speciation calculations.

Abstract. We carried out optical observations of the field of the X-ray pulsator RX J0806.3+1527. A blue V = 21.1 star was found to be the only object consistent with the X-ray position. VLT FORS spectra revealed a blue continuum with no intrinsic absorption lines. Broad (v ∼ 1500 km s −1 ), low equivalent width (∼-1 ÷ -6Å) emission lines from the HeII Pickering series were clearly detected. B, V and R time-resolved photometry revealed the presence of ∼15% pulsations at the ∼321 s X-ray period, confirming the identification. These findings, together with the period stability and absence of any additional modulation in the 1 min−5 hr period range, argue in favour of the orbital interpretation of the 321 s pulsations. The most likely scenario is thus that RX J0806.3+1527 is a double degenerate system of the AM CVn class. This would make RX J0806.3+1527 the shortest orbital period binary currently known and one of the best candidates for gravitational wave detection.