Structural pre-conceptual design studies for an EU DEMO equatorial EC port plug and its port integration
Introduction
For the EU DEMO Tokamak, EC launching systems for plasma heating and stabilization are under development. Based on the 2017 engineering baseline, the 2018 physics baseline, and the port plugs being radially recessed to the level of the Vacuum Vessel (VV) inner shell and hence not blocking the vertical extraction of the outboard BB segments [1], a pre-conceptual design study of an EU DEMO equatorial EC launcher has been made. For optimum performance [2], the design study features a hybrid concept with MSA and also OEWG antennas. The MSA is considered for plasma stabilization and has a (partially) quasi-optical beam layout with steerable mirrors at a recessed position behind the radial extension of the breeding blankets [3]. Beside the MSA, also an OEWG antenna is designed for the EC Launcher, which will be used for plasma heating only.
The pre-conceptual design of the EC Launcher features structural components, which can accommodate this hybrid millimeter-wave system accordingly. It also comprises shielding elements, cooling installations and interface provisions for the integration of the optical system. All structural components were designed with respect to available design requirements on position and dimensions, mechanical and thermal loads, nuclear constraints, physics performance, maintenance and geometrical and functional interfaces.
The CAD model is set up by parametric skeleton geometries, which guarantees a relatively flexible design to cope with moving targets and potential future baseline changes (e.g. the concept of an RSA).
Section snippets
DEMO Engineering baseline 2017
Fig. 1 outlines a cross-section of the EU DEMO engineering baseline model 2017 [4], having installed the EC launcher already. This model provides the current layout of the EU DEMO Tokamak, including the breeding blankets, the vacuum vessel with its vertical upper ports, the bioshield, the cryostat and many more interfacing and design-relevant components of an EC Launcher for a future EU DEMO reactor.
EC Launcher design
Beside the engineering baseline model 2017, the EC launcher design is made according to the physics baseline model 2018 and the latest optical system design, provided by the Italian Institute for Plasma Science and Technology (ISTP) [2], (cf. Fig. 2).
It is comprised of an MSA with two sections of three beamlines each for NTM (Neo-classical Tearing Modes) control and two further OEWG antenna sections with eight waveguides each for plasma heating. Both systems are arranged in a symmetric layout
Equatorial port for the EC launcher
The equatorial ports in the current EU DEMO concept offer the possibility of customized dimensions for particular installations. The dimensional limits are set on principle by the poloidal clearance between the poloidal field coils and the toroidal clearance between the toroidal field coils only while the maximum radial extension is defined by the position of the Bioshield.
This means in fact a maximum height of the equatorial port of 4000 mm and a maximum width of around 4700 mm. The greatest
EC Launcher port plug design
The mirrors of the In-Vessel millimeter wave system require precise and safe installation into the DEMO equatorial port. Thus they are mounted into dedicated port plugs, which are basically massive structural components with customized shapes and cut-outs which guarantee undisturbed beam propagation into the plasma, maximum neutron shielding properties and straightforward maintenance processes. Due to their position close to the plasma also active cooling of the plugs will be required.
One
Maintenance concept
Preliminary evaluations indicate the installations of the EC launcher as to be maintained either regularly or on purpose during EU DEMO operational lifetime. In order to perform the required procedures in an effective way, the replacement of the plugs is preferred instead of the replacement (or repair) of individual mirrors or other smaller sized components.
The SM EPP and its integration is designed for multiple replacement during DEMO operation, which is why the whole procedure is planned to
Closure plate assembly
The maintenance concept described in chapter 6 requires an adequate layout for the accessible vacuum boundary of the equatorial port. Thus, this so-called closure plate has been sub-divided into a staggered assembly, consisting of several elements, to be opened for dedicated purpose.
The main closure plate (1) is formed as a massive plate, which areal dimension is 3880 × 2830 mm². It has a thickness of 110 mm and carries all other sub-plates. It is attached to the port extension by bolts and its
Neutronic considerations
In the EU DEMO plant description document [6], neutronic design limits are given regarding neutron damage, Helium production and Shutdown dose rates for several areas and types of components for an EU DEMO reactor.
Since the demonstration of fulfilling these design limits with the pre-conceptual design can be made not before a dedicated MCNP neutronic analysis has been run, a rather conservative approach has been chosen for designing the EC Launcher components. Typical consequences from this
Versatility of the design
The present pre-conceptual design of the EC launcher prefers a combination of OEWG with a quasi-optical dogleg beam configuration for plasma heating and a MSA concept for NTM stabilization. However, the current concept of an equatorial port with dedicated port plugs for individual millimeter-wave component assemblies and optional auxiliary shield blocks has the freedom to be adapted easily for further millimeter wave concepts as well. Another important feature, which offers particular design
Conclusion
A EUROfusion task has been placed to advance the pre-conceptual design for an EU DEMO EC launcher. Starting from the engineering baseline 2017 model, the physics baseline 2018 and a new MSA and OEWG antenna design from ISTP, a design concept has been established and corresponding CAD models were created. Beside proper integration into the baseline models, also RH maintenance schemes and neutronic aspects were taken into account. The model will be the basis for forth-coming MCNP- and EM-analyses.
CRediT authorship contribution statement
Peter Spaeh: Conceptualization, Methodology, Software, Data curation, Writing - original draft, Vizualisation. Christian Bachmann: Conceptualization, Project administration, Funding acquisition. René Chavan: Investigation. Aljaz Cufar: Software, Formal analysis, Data curation. Thomas Franke: Conceptualization, Methodology, Writing - review & editing, Project administration. Dirk Strauss: Conceptualization, Supervision, Project administration, Funding acquisition. Minh Quang Tran: Supervision,
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the EURATOM research and training programme 2014-2018 and 2019-2020 under grant agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
References (6)
Overview over DEMO design integration challenges and their impact on component design concepts
Fusion Eng. Des.
(2018)EU DEMO EC equatorial launcher pre-conceptual performance studies
Proceedings of this Conference
(2019)Initial port integration concept for EC and NB systems in EU DEMO tokamak
Fusion Eng. Des.
(2019)
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2022, Fusion Engineering and DesignCitation Excerpt :Cooling spirals are foreseen at each joint, for proper cooling of the mirror and of each moving pantograph element (Fig. 4). The EC optical system in-vessel components are integrated into the EC equatorial port plug (EPP) structural system [15]. The proposed design optimizes precise alignment, mechanical robustness, operational reliability and maintainability [16].
Containment structures and port configurations
2022, Fusion Engineering and DesignCitation Excerpt :Both, gyrotrons operating at fixed frequencies and gyrotrons with tunable frequencies are feasible with this design concept. From the gyrotrons the EC millimeter-wave power of maximum 130 MW will be transmitted into the plasma by 108 transmission lines, which are integrated into six equatorial ports [47, 48]. Other variants with a different number of ports were studied but are either occupying too many ports or could not achieve the system availability.