Disassembly and sampling of graphite ball fuel elements

In the scope of the THTR postirradiation examination program, irradiated ball-type fuel elements must be examined and prepared for advanced experiments. This requires a controlled breaking-open of the graphite shell for taking samples of definite size and dimensions from the inner and outer parts of the fuel element. In the present report are described two special pieces of equipment which have been developed and constructed for this purpose. They emphasize avoiding contaminationof the neighbouring equipment of the box, and diminishing the inevitable cross-contamination of the surfaces of the samples themselves by means of a suitableventilation procedure

Curvature dependence of semiclassical corrections to ray optics: How Goos-Hänchen shift and Fresnel filtering deviate from the planar case result

Ray optics is a useful tool even in the regime where, actually, full wave calculations would be appropriate. However, wave-inspired adjustments are needed to ensure the accuracy of ray-based predictions. Here, we investigate these semiclassical corrections to the ray picture —the Goos-Hänchen shift and the Fresnel filtering effect— for the reflection of light beams at curved, rather than planar, interfaces. We present analytical and numerical results that highlight the role of boundary curvature and show clear deviations from the planar case. The Goos-Hänchen shift is decreased at convexely curved interfaces present in optical microcavities and microlasers compared to the planar case, and increased for concave curvature. In contrast, the Fresnel filtering effect is increased by both kinds of curvature. For a straightforward explanation of these findings we introduce an intuitive picture that explicitly takes curvature into account and that allows for a qualitative understanding of the beam shift behaviour