Understanding heat flux deposition processes is essential for the design of the plasma facing component allowing reliable high power steady state plasma operations. Misalignments up to δ=0.2mm ...between two adjacent CFC tiles have been reported on the Toroidal Pump Limiter of Tore Supra. Heat flux impinging the top and leading edge of the protruding tile are characterized with both IR thermographic system and numerical modelling using 2D particle-in-cell simulations that accounts for the Larmor radius smoothing effect of incident ions. Numerical heat loads are coupled with a 2D thermal model of the tile and with a specific sensor correction to simulate spatial-resolution related effects (necessary here since the tile misalignment is smaller than the spatial resolution of the IR system). In the experiment depicted here, with a misalignment smaller than an ion gyro-radius, the Larmor radius smoothing effect is maximum and overheating of the leading edge is reduced by a factor of two.
•Macro- and micro-segregation were observed in electron beam welded CuCrZr/Inconel 625 joints.•Post-weld aging stimulated the formation of Nb/Mo-rich networks and increments of micro-hardness in ...Inconel-rich irregular islands.•Both the as-welded and aged specimens passed 10,000 cycles of rotary bending fatigue testing under a strain amplitude of 0.1%.•Aging shifted the weakest point of CuCrZr slightly away from the Inconel/CuCrZr weld.
The microstructures and mechanical properties of electron beam welded CuCrZr/Inconel/316 L junctions for WEST project have been investigated. As the welding of ending tubes is performed after the hot isostatic pressing (HIP) for the real components, in this study the CuCrZr tubes were annealed with identical parameters of HIP before welding in order to simulate the real situations of component manufacturing. The junctions were free of defects such as micro-cracks or incomplete penetration. The mechanisms of macro-segregation features, such as beaches, peninsulas, and irregular islands, and of micro-segregation features, such as small spheres, dendrites, Cu-rich particles, and Nb/Mo-rich networks have been discussed. Mechanical testing shows that postweld aging nearly does not improve the tensile strength of the junctions because it just shifts the weakest point of CuCrZr slightly away from the Inconel/CuCrZr weld, but it is beneficial for the tensile elongation of the junctions at 200 °C; meanwhile, postweld aging decreases the hardness of CuCrZr in regions out of the heat affected zone. Cold helium testing performed after rotary fatigue testing indicated that postweld aging does not change the fatigue resistance of the junctions, at least under the current testing conditions. Significant increments in hardness of irregular Inconel-rich islands induced by aging may be attributable to the formation of Nb/Mo-rich networks. This study may be of significance for the manufacturing of ITER divertor components.
► The WEST programme is a unique opportunity to experience the industrial scale manufacture of tungsten plasma-facing components similar to the ITER divertor ones. ► In Tore Supra, it will bring ...important know how for actively cooled W divertor operation. ► This can be done by a reasonable modification of the Tore Supra tokamak. ► A fast implementation of the project would make this information available in due time. ► This allows a significant contribution to the W ITER divertor risk minimization in its manufacturing and operation phase.
The WEST programme consists in transforming the Tore Supra tokamak into an X point divertor device, while taking advantage of its long discharge capability. This is obtained by inserting in vessel coils to create the X point while adapting the in-vessel elements to this new geometry. This will allow the full tungsten divertor technology to be used on ITER to be tested in anticipation of its use on ITER under relevant heat loading conditions and pulse duration. The early manufacturing of a significant industrial series of ITER-similar W plasma-facing units will contribute to the ITER divertor manufacturing risk mitigation and to that associated with early W divertor plasma operation on ITER.
•The manufacturing of the divertor structure and coils has been performed according to the technical specifications.•The scale one dummy coils have been tested, the last test (curing process ...validation) being scheduled to be done in September 2016.•The divertor in situ assembly has been carried out successfully.•The brazing process was carried out with an excellent repeatability.•The impregnation and curing phase of the divertor coils are scheduled to be done in November 2016.
In order to fully validate “ITER-like” actively water cooled tungsten plasma facing units, addressing the issues of long plasma discharges, an axisymmetric divertor structure has been studied and manufactured for the implementation in the WEST (W-Tungsten Environment in Steady state Tokamak) tokamak platform.
This assembly, called divertor structure and coils (4m diameter, 20t), is composed of two stainless steel casings containing an actively water cooled (up to 180°C, 4MPa) copper winding pack designed for a conductor current in the range of 12.5kA (up to 1000s). It must sustain harsh environmental conditions in terms of ultra-high vacuum, high temperatures and electrodynamic loads. One major difficulty is the assembly by induction brazing of individual bended conductor sectors inside the vacuum vessel and the consecutive sealing of the casings by TIG welding.
Therefor development activities have been carried out on a scale one dummy coil, such as brazing, assembly, thermal cycling and electrical insulation tests (5kV ground voltage). Whereas the brazing assembly technics and the conductor installation were validated without major difficulties, different technical solutions for the electrical insulation had to be tested. The chosen solution is a resin epoxy impregnated fiber glass fabric layered around the conductors followed by a polymerization procedure.
In parallel the manufacturing of divertor structure components started in the second half of 2013 with a total delivery at the end of 2015.
The paper will illustrate the technical developments which have been performed in order to fully validate the design. It concerns mainly the dummy coil and the complex conductor installation procedure assisted by virtual reality tools. The manufacturing methods proposed by industry in order to fulfil the technical requirements will be also addressed. Finally the processes and associated tools used in order to implement this large component inside the WEST vacuum vessel will be detailed.
•The mechanical design and integration of the divertor structure have been performed.•The design of the casing and the winding-pack has been optimized.•The coil assembly process has been ...assessed.•The realization of a coil mock-up scale one is scheduled.
In order to fully validate “ITER-like” actively water cooled tungsten plasma facing units, the implementation of an axisymmetric divertor structure in the Tokamak Tore-Supra has been studied. With this major upgrade, the so-called WEST (Tungsten Environment in Steady state Tokamak), Tore-Supra will be able to address the issues of long plasma discharges using a tungsten divertor based on monoblock targets.
The divertor structure and coils assembly are made up of two stainless steel casings containing a copper winding pack cooled by a pressurized hot water circuit (up to 180°C, 4MPa) in which a total divertor current of up to 16×13kA is circulating in steady state. The conductor is electrically insulated and wedged inside the casing in order to be mechanically protected.
The divertor which is designed to perform steady state plasma operation (up to 1000s), must sustain harsh environmental conditions in terms of ultra light vacuum conditions, electromagnetical loads and electrical insulation (5kV ground voltage) under high temperature (180°C).
Therefore, a feasibility study of such a complex structure has been performed. It implied activities on a scale one dummy coil, such as installation, assembly issues and representative tests (electric, thermal and hydraulic).
The manufacturing of the divertor structure, which is a large assembly of 4-m diameter representing a total weight of around 20tonnes, started in the second half of 2013 and is expected to be delivered by the end of 2014.
The paper will illustrate the technical developments and tests performed during 2013 and beginning of 2014 in order to fully validate the design concept before the industrial phase. The manufacturing methods proposed by the contractor in order to fulfil the technical requirements will be also addressed.
