[en] Resonant inelastic x-ray spectroscopy at the uranium N₄ absorption edge at 778 eV has been used to reveal the excitations in UO₂ up to 1 eV. The earlier (1989) studies by neutron inelastic scattering of the crystal-field states within the ³H₄ multiplet are confirmed. In addition, the first excited state of the ³F₂ multiplet at ∼520 meV has been established, and there is a weak signal corresponding to the next excited state at ∼920 meV. This represents a successful application of soft x-ray spectroscopy to an actinide sample, and resolves an open question in UO₂ that has been discussed for 50 years. The technique is described and important caveats are drawn about possible future applications. (letter)

[en] We report on first measurements with polarized electrons stored in a medium-energy ring and with a polarized internal target. Polarized electrons were injected at 442 MeV (653 MeV), and a partial (full) Siberian snake was employed to preserve the polarization. Longitudinal polarization at the interaction point and polarization lifetime of the stored electrons were determined with laser backscattering. Spin observables were measured for electrodesintegration of polarized ³He, with simultaneous detection of scattered electrons, protons, neutrons, deuterons, and ³He nuclei, over a large phase space

No abstract available

[en] Full text of publication follows.The modular VHTR is one of six advanced fission systems of interest for meeting the Generation IV goals of attaining highly economic, safe, reliable, sustainable, proliferation-resistant systems. The VHTR offers significant advantages for long-term development of sustainable energy and in particular for heat applications and hydrogen generation. This system can operate with either a direct or indirect cycle and makes use of the high efficiency Brayton cycle. Work on materials investigations for the HTR within Europe recommenced with the EU 5. Framework Programme (5FP) projects HTR-M and M1 [1] and together with other SFP projects (fuel, reactor physics, components, safety,..) and the establishment of the European High Temperature Reactor Technology Network HTR-TN, served as the main European platform for the co-ordination and development of VHTR issues. The HTR-M and M1 projects addressed material requirements for the key components of the direct cycle HTR. The work especially focused on the materials development for the pressure vessel, high temperature components (including turbine), and the graphite core. Alongside this, developments were undertaken on key component issues (HTR-E) associated with the gas turbine, the recuperator and other system developments (e.g. tribology, corrosion, bearings, seals, etc.) concerned the operation and performance of the power circuit components. Within this paper the main highlights from the results of the 5FP programmes affecting material issues are reviewed and examined. For the 6. Framework Programme activities the main European research focus on VHTR is through the RAPHAEL Integrated Project (IP). The project started in 2005 and addresses a range of issues (materials, components, fuel, code qualification, etc.), which are structured in a similar way to the corresponding GIF VHTR projects. The materials issues are addressed within one of the RAPHAEL, sub-projects with a focus on outstanding issues. The main emphasis on materials is for graphite development, materials for the heat exchangers, continuation of vessel qualification and work on design code requirements. The progress of the materials issues within the RAPHAEL-IP, which has reached its mid-term stage will be reviewed and the expected future orientations of the programme described. The main materials issues addressed in the paper are as follows: Reactor pressure vessel: - review and database actions covering existing and new vessel material options; - tests on Mod 9Cr 1Mo steel welded joints under irradiated and non-irradiated conditions to determine suitability for vessel application. High temperature materials: - review and database actions for the control rod and turbine; - review and database actions for the heat exchangers; - tests on selected materials (carbon/carbon (C/C) composites, high alloy steels) at temperature and under short and intermediate times in air, and simulated carburizing and de-carburizing environments. Graphite core: - review of experience plus data base actions for new graphites; - oxidation tests on graphites and C composites; - graphite selection and irradiation testing at 750 deg C and 950 deg C; - micro-structural modelling and development of guidelines. (authors)