EU-DEMO Vacuum Vessel Port Closure Plate fastening developments
The EU-DEMO baseline design for the vacuum vessel (VV) currently provides for 48 openings – the so-called VV ports.
These are foreseen to accommodate port plugs containing components, such as front ends for diagnostics and heating systems, first wall protection limiters and the first stages of the VV vacuum system. During the operation of EU-DEMO all these openings have to be closed vacuum tight by so called port closure plates (PCP) allowing for the required high vacuum environment inside the VV. The VV ports also provide access into the VV for scheduled and unscheduled maintenance of the in-vessel components. Opening and re-closing of the PCPs within a reasonably short time is a requirement for EU-DEMO, that shall demonstrate the viability of electricity production by fusion. Due to the activation of the components, all work must be carried out with remote maintenance.
In the field of high vacuum technology, connections using a large number of bolts are an established method for fastening PCPs. From the experience of existing fusion experiments, some disadvantages of bolted flanges are known. In particular, these are the rather long duration of the opening process and the possible fretting.
This paper summarises and describes the current status of the development of possible alternative PCP fastening concepts with improved characteristics. Furthermore, it gives a first overview of the activities that have been started in relation to the qualification of a welded gasket. The approach to collaborate with industry to take advantage of proven methods and ensure the mutual transfer of knowledge is also presented. It is intended to increase industry involvement in the development of future fusion power plants.