[en] If a graphite reflector of a pebble bed reactor is equipped with insertable absorber rods power control is achieved by less insertion depth of these rods than would be required for conventional designs for the same type of reactor. Therefore the difficulties growing with insertion depth and the danger of damaging fuel elements are reduced. With less stroke, the drives of the control rods are simplified, too. A means for this is doping the graphitic reflector bottom and the lower part of the reflector with neutron-absorbing material. A partial flow of neutrons forced downwards on insertion of the control rods into the upper zone of the reflector will be absorbed in this lower region. A formula is given for this doping. (HP)

No abstract available

[en] In a multiferroic material, ferromagnetism (FM) and ferroelectricity (FE) coexist, presenting exciting opportunities for research into new phenomena and technological innovation. Bismuth Ferrite (BiFe0₃) is among the rare cases where both properties exist at room temperature [1]. As such, its use in functional thin film heterostructures, like multiferroic tunnel junctions or exchange bias systems, which combine multiferroic (MF) and ferromagnetic layers, such as La_0.67Sr_0.33MnO₃ (LSMO), is of particular interest. Most important in these thin film systems are the interactions across the interface between layers. Using polarised neutron reflectivity (PNR) and resonant X-ray reflectometry (XRMR), we have studied LSMO/BiFe0₃ bilayers, focusing on intriguing interfacial physics. PNR was performed at the Bragg Institute, ANSTO, Sydney, Australia; NRC-CNBC, Chalk River, Canada; and FRM-II, Munich, Germany. XRMR measurements were performed at BESSY II, Helmholtz Center Berlin, Germany. A simultaneous analysis of the PNR and XRMR datasets yielded detailed insight into the stoichiometry and magnetic depth profile of the bilayer system. Our results indicate a depleted FM magnetic region, which corresponds with a modified stoichiometry, extending ~2 nm into the LSMO at the bilayer interface region. This is significantly larger than the atomic scale interface roughness and contradicts models of spin or orbital reconstruction at the interface layer.

[en] A new method for fabricating Floating Supported Bilayers (below left) is reported, which uses a self assembled monolayer of thiolipid on a gold surface as a support for the membrane. The thiolipid layer was characterised by SPR and Neutron Reflection, and almost complete coverage of the surface by the lipid was seen. This high coverage resulted in similarly high coverage of the subsequent bilayer, with the reflectivity measurements suggesting an essentially defect-free floating membrane of DPPC in the gel phase. See below right for the fitted density profile from Neutron Reflectivity measurements. This demonstrates that the surface coverage is › 99% in both the tethered and floating layers.

No abstract available

[en] The aim of our study carried out during the last 5-6 years was to find the hidden organic materials (for example explosives or drugs) in bulk objects with the neutron reflection and activation methods. The applicability of the concept of the differential σ_β and integral Σ_β reflection cross sections is also demonstrated. Further investigations are also recommended to improve the neutron reflection method. (author)

[en] The side reflector is placed and supported above the hot gas plenum over some rows of supporting columns on the bottom layers of the reactor core extended outwards, where the hot gas plenum is extended by the free space between these supporting columns. The hot gas plenum is bounded radially by the thermal side shield or liner provided with thermal insulation in this area. The hot gas ducts are connected to the thermal side shield or the liner. An annular space seal is situated immediately above the hot gas duct connections in the annular space between the outer wall of the side reflector and the thermal side shield or liner. (orig./HP)

No abstract available

[en] The description is given of a renewable lower reflector structure for a high temperature pebble bed reactor of the type comprising a cylindrical or prismatic graphite vessel wrapped in concrete and terminating at its lower end with a conical or pyramidal bottom fitted with a central aperture allowing the pebbles to be discharged by gravity. This structure includes a bed of several layers of protective graphite pebbles on the bottom and, fitted vertically so as to be removable along the centre line of the central aperture through the reflector and the concrete, a graphite block drilled in its centre to allow the discharge of the fuel pebbles and the protective pebbles. The graphite block rises above the level of the central aperture by an extent corresponding to the thickness of the bed when the reactor is working

[en] A drive system that utilizes a linear induction motor has been devised which replaces the current pneumatic/hydraulic system. It is a less-complex system permitting easier servicing