Wendelstein 7-X (W7-X) is an experimental modular stellarator of the HELIAS type, currently in the second phase of operation in Greifswald, Germany. The stellarator is a complex 3D structure with high level safety requirements. As a result, sophisticated methods are necessary for the analysis of critical components and it is very important to evaluate structural strength of the welded connections between the plasma vessel and the ports. The structural integrity analysis of the welded connection between plasma vessel and ports has been performed for several critical and/or representative port welds. The modelling of the welded connection was performed in two steps. First the geometrical 3D models of these port welds were prepared using the SolidWorks software. The model of a welded connection of the complex shape was modelled by creating a big number of sketches around the perimeter of the port-to-PV connection. Later, the sketches were connected using a loft feature and was transferred to the ABAQUS/Standard FE software. The limit analysis by means of finite element method (ABAQUS code) was used to confirm static strength reliability of port welds. According to the results of the analysis it is possible to conclude that the proposed welding between the plasma vessel and the analysed ports fully meets the structural requirements.

The stellarator experiment Wendelstein 7-X (W7-X) is designed for stationary plasma operation (30 min). Plasma facing components (PFCs) such as the divertor targets, baffles, heat shields and wall panels are being installed in the plasma vessel (PV) in order to protect it and other in-vessel components. The different PFCs will be exposed to different magnitude of heat loads in the range of 100 kW/m(2)-10 MW/m(2) during plasma operation. An important issue concerning the design of these PFCs is the thermomechanical analysis to verify their suitability for the specified operation phases. A series of finite element (FE) simulations has been performed to achieve this goal. Previous studies focused on the test divertor unit (TDU) and high heat flux (HHF) target elements. The paper presents detailed FE thermo-mechanical analyses of a prototype HHF target module, baffles, heat shields and wall panels, as well as benchmarking against tests. (C) 2013 Elsevier B.V. All rights reserved.

The Wendelstein 7-X (W7-X) modular stellarator is in the assembly phase at the Max-Planck-Institut fur Plasmaphysik in Greifswald, Germany. The design of the "basic machine", i.e. without in-vessel components, diagnostics and periphery, is largely completed, structural parameters such as bolt preload, initial conditions for contact elements, etc. are defined, and most of the components are manufactured and partly assembled. Therefore, the focus of structural analysis was shifted towards fast analyses of non-conformities, changes in the assembly procedure, and exploration of operational limits. Assembly-related work is expected to continue until commissioning of the machine, however, with decreasing intensity. In parallel the analysis requirements for in-vessel components, diagnostics and periphery will increase.This paper focuses on the most remarkable results, on special problems which had to be solved, on strategic issues like parameterization, complex finite element model structuring and benchmarking with alternative models in different codes, on assumptions of reasonable safety margins and expected tolerances. and on confirmation of analysis results by tests. Finally it highlights some lessons learned so far, which might be relevant also for other large fusion machines, and gives an outlook on future work. (C) 2011 Elsevier B.V. All rights reserved.

TheWendelstein 7-X (W7-X) modular stellarator is in the assembly phase at the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald, Germany. The goal of the project is to demonstrate that this type of machine is a viable option for a fusion power-plant. The “pentagonal” magnet system of the machine encompasses 50 non-planar and 20 planar superconducting coils with sophisticated support structure. Structural reliability of components as well as resulting deformations and displacements during various modes of operation have to be considered not only for the magnet system but also throughout the whole cryostat whose main components are the plasma vessel, outer vessel, ports, and thermal insulation. A reliable prediction of the W7-X structural behaviour is only possible by employing complex finite element (FE) simulations with a hierarchical set of FE models. A special strategy has been developed and implemented for the task. The design is basically completed, main parameters are defined, and most of the W7-X components are manufactured. Therefore, the focus in the analysis is being shifted to the creation of parametric FE models which allow performing fast analyses of possible nonconformities, changes in the assembly procedure, and future exploration of operational limits. This paper gives an overview of the implemented analysis strategy, the applied safety margins, and focuses on the most remarkable results.

The purpose of the Wendelstein 7-X cryostat is to thermally insulate the magnet system (operating at cryo-temperature) by high vacuum and super insulation, to provide and enclose the working space for the plasma, and to serve as a bearing structure for the system components that have to be placed in the immediate vicinity of the plasma, such as the first wall, the divertor and some of the diagnostic devices. Concerning structural components only, the cryostat is composed of the plasma vessel, the outer vessel and the ports that interconnect the vessels. The cryostat together with the machine base comprises the so called cryostat system, and this is the system that is under consideration in this paper. Due to both the geometrical complexity and the complexity of loading, individual subsystems of the cryostat system could not be analyzed separately. For that reason, a global finite element model of the whole cryostat system had to be created. The paper presents an overview of finite element modeling, simulations with ANSYS performed on this system, and the corresponding calculation results.

The goal of the Wendelstein 7-X (W7-X) stellarator project is to demonstrate that this type of machine is a viable option for a fusion power-plant. At present the W7-X experiment is in the assembly phase at the Max-Planck-Institut for plasma physics in Greifswald, Germany. The reliable prediction of the structural behavior of the W7-X machine is only possible by employing complex finite element (FE) analyses with a hierarchical set of FE models. A special strategy has been developed for the structural analysis which is under implementation now. This paper gives an overview of the analysis strategy, the applied structural criteria and critical issues, and focuses on the most remarkable results. The main attention is paid to the components that have been changed or optimized recently.

The Wendelstein 7-X (W7-X) stellarator project goal is to demonstrate that the stellarator is a viable option for a fusion power plant. W7-X is in an advanced state of construction and has entered the assembly phase at the Max-Planck-Institute fur Plasmaphysik (IPP) in Greifswald, Germany.The W7-X "pentagonal" basic magnet system is highly sensitive to parameter variations; the cryostat comprises two vessels, which are interconnected elastically by 299 ports. The strategy of the structural analysis for this complex mechanical system is being developed and implemented with the ultimate goal to create a tree of numerical models which reliably predict the stellarator structural behaviour.This paper gives an overview of the strategy, addresses the critical issues and focuses on the most interesting results of the analyses. (C) 2007 Elsevier B.V. All rights reserved.