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The Pre-Compression Ring (PCR) is an important component of ITER Magnet System. It is designed to generate a radial inward force on every Toroidal Field (TF) coil, putting in compression the shear keys, contrasting the bending of the inner leg and improving the stress distribution on the wedge surface. Stretching the PCR by tensioning 16 bolts on 4 counter flanges generates a total force of 47.8 MN on each coil. The application of such high preload, together with the large number of bolts to be tighten, the limited space available, and obviously the need of preserving the structural integrity of all the components, make this phase of the tokamak assembly far to be trivial. For these reasons, an in-depth analysis of the tightening procedure has been performed by means of FEM analysis, investigating the possible patterns and multi-step sequences to achieve the desired preload. The study led to a deep comprehension of the behavior of the system and permitted to identify and control the main critical aspects, i.e., the increase of stress in the PCR due to the ‘ripple’ and the variation of preload in some portion of the rings when the preload is applied in a different area, both due to the need of operating on a limited number of bolts at each time. The outcome of the investigation is the detailed definition of two multi-step tightening procedures suitable to be adopted for the assembly.

In the ITER magnetic system 18 Toroidal Field coils (TF coils, or TFC) must be assembled so that the Current Center Line (CCL) of the TF magnets is correctly positioned within its tight tolerances. There are two major processes that cause large deformation of the TF coils: the load transfer toward the gravity support, occurring when the temporary inboard vertical support is removed, and the centripetal displacement due to the Pre-Compression Ring (PCR) tensioning. For those processes, specific procedures and tools are being developed, investigating at the same time the proper method to verify the procedures. Monitoring deformations and forces during the application of huge loads is the key for guaranteeing CCL quality, construction schedule, and health & safety matter. As results of the investigation, a part of the components and tools for TF PCR pre-tensioning has been changed from baseline plan: manual tightening multi-jackbolt tensioners (MJT) have been replaced with hydraulic tools and dedicated nuts. Current procedures including the tools design, the FE simulations, and the monitoring system plans are presented in this paper.

A fracture mechanics approach has been adopted in the present study to investigate the fracture toughness behavior of three commercial composite resins for dental use named Clearfil photo posterior, P-50 and Occlusin. The resins have been cast in to ring-shaped specimens for the determination of individual fracture toughness values. The experimentally determined values have been compared with fracture toughness values obtained from the indentation micro-fracture method, which is the currently more popular test method for determining fracture toughness characteristics of composite resins. Occlusin was found to exhibit higher fracture toughness values than any other resin, employing the ring specimen test procedure. However, this was not the case when using the indentation method which gave comparable fracture toughness values for all three resins. It was concluded that the ring specimen provides a simple, accurate and reproducible method for providing a measure of the materials fracture toughness.

Human tumour xenografts (HTXs) are a useful tool for animal experiments especially for evaluation of new antitumour drugs. We have been establishing HTXs, and have developed tumour chemosensitivity panels for new drug evaluation using them.With regard to quality control (problems in changes into mouse-type tumours and/or artificial cross-contamination among tumour lines), we studied genetic profiling, and effects of long-term passaging on tumour properties such as growth and chemosensitivities, and we discuss the use of cryopreservation stock of HTXs and periodic replacement in order to maintain reproducibility of the experimental results.We examined isozyme markers and DNA fingerprinting to identify species and individuality of the tumours, respectively. Growth curves and sensitivities to antitumour drugs were examined using HTXs with different passaging in nude mice.Among the tumours we maintained, five human tumours were found to have changed to mouse origin from their isozyme markers and were excluded. We identified the individuality of tumours which we used for the chemosensitivity panels by DNA fingerprinting, and their properties were stable for long-term passaging in nude mice. However, growth speed and chemosensitivities to drugs were altered with long-term passaging, although DNA fingerprint analysis did not show any obvious changes with passaging.Genetic profiling, such as isozyme markers and DNA fingerprinting, is useful to identify individuality of experimental HTXs, and tumours should be renewed periodically even when there are no signs of artificial contamination when they are used in experiments which require continuous reproducibility of experimental results.

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