Features and analyses of W7-X cryostat system FE model

Abstract

Please cite this article in press as: P. van Eeten, et al., Features and analyses of W7-X cryostat system FE model, Fusion Eng. Des. (2015), http://dx.a b s t r a c t The Wendelstein 7-X stellarator is presently under construction at the Max-Planck-Institute for Plasma Physics in Greifswald with the goal to verify that a stellarator magnetic confinement concept is a viable option for a fusion power plant.The main components of the W7-X cryostat system are the plasma vessel (PV), outer vessel (OV), ports, thermal insulation, vessel supports and the machine base (MB). The main task of the cryostat system is to provide an insulating vacuum for the cryogenic magnet system while allowing external access to the PV through ports for diagnostic, supply and heating systems.The cryostat is subjected to different types of loads during assembly, maintenance and operation. This ranges from basic weight loads from all installed components to mechanical, vacuum and thermal loads. To predict the behavior of the cryostat in terms of deformations, stresses and support load distribution a finite element (FE) global model has been created called the Global Model of the Cryostat System (GMCS).A complete refurbishment of the GM CS has been done in the last 2 years to prepare the model for future applications. This involved a complete mesh update of the model, an improvement of many model features, an update of the applied operational loads and boundary conditions as well as the creation of automatic post processing procedures.Currently the GMCS is used to support several significant assembly and commissioning steps of W7-X that involve the cryostat system, e.g. the removal of temporary supports beneath the MB, transfer of the PV from temporary to the final supports and evacuation of the cryostat. In the upcoming months the model will be used for further support of the commissioning of W7-X which includes the first evacuation of the PV.

Experience with the commissioning of the superconducting stellarator Wendelstein 7-X

“…This was confirmed by the results of the PV strain gauges, but also by the plasma vessel support load and port bellow deformation measurements. All of these measurements showed reasonable agreement with the predictions from the GMCS [19].…”

“…This model has been used to perform detailed calculations for different load cases (cryostat and PV evacuation, PV baking, normal operation with PV and OV evacuated, etc.). Recently an updated version of the GMCS (v3.4) was used to predict the cryostat behavior during its first evacuation and to verify this prediction with a set of different measurements performed during this first evacuation [19].…”

Monitoring of W7-X cryostat commissioning with cryostat system FE model

“…After the cryostat evacuation and magnet system cool down [3] the plasma vessel was evacuated for leak search and subsequent baking with the goal to achieve a pressure of <10 -8 mbar before start of plasma operation.…”

Engineering Challenges in W7-X: Lessons Learned and Status for the Second Operation Phase

“…The GMCS is part of a larger set of FE models used for structural analyses on W7-X components. This set includes the second global model of W7-X which covers the magnet system and its support structure [20]. Both systems can be analyzed independently as there is no relevant mechanical interaction between the two systems.…”