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The utilization of composites layered on an additive manufactured substrate, for the production of coil supports for modular coils in small or middle size experimental stellarators is assessed. The focus of the study is a monolithic coil support comprising the coils of a half-period of a stellarator, somewhat similar to the ones in UST_2 and ARIES-CS stellarators. However, the concept may be applicable to quasi-monolithic coil supports (coil forms of NCSX type) or individual coil casings (W7-X type). Coil supports for stellarators require high precision, stiffness and strength for large contorted parts. Traditionally, monolithic coil supports are produced by steel casting/forging and final machining. This production method and material gives accurate, stiff and strong coil supports, but the method may be expensive for monolithic supports due to the geometrical complexity and required accuracy of the structure. In relation to those matters, this work investigates whether a monolithic coil support comprising an additive manufactured resin substrate, which is externally (outward from the coils) surrounded with a thick layer of fibre-reinforced resin, may achieve enough strength and stiffness under middle/high magnetic fields. Finite element calculations are produced to obtain the direction of the principal stresses and their values in compression and tension at different areas of the monolithic support, which is relevant for anisotropic materials. The feasibility of directional application of (carbon) fibres on the winding surface of the stellarator outward from the coils is experimentally tested on a scaled-down additively manufactured prototype of a monolithic support. The strength and stiffness of the composite structure appears sufficient for common magnetic fields in experimental stellarators, and the 3D-composite design and manufacturing was technically feasible.

The paper studies the dimensional accuracy of additively manufactured (AM) coil winding structures for small experimental stellarators fabricated under industrial non-laboratory conditions. Insufficient accuracy is one of the main issues hindering the use of additive manufacturing (AM) for coil windings structures (coil casings and coil forms or frames) for stellarators. The dimensional accuracy of one complex modular coil frame and four planar coil casings is studied for different AM techniques and materials, in particular Selective Laser Sintering (SLS) in polyamide, Stereolithography (SLA) in resin, Fused Deposition Modelling (FDM) in ABS and PolyJet in resin. The measurements are performed by a Mitutoyo Coordinate Measuring Machine. The AM parts are hollow for subsequent internal casting with (fibre-reinforced) resin for strength and performance enhancement, method named 3Dformwork. The paper reports the features of the sample parts, the metrology methodology utilised, the performed measurements and the resulting dimensional deviations for each AM technique. Professional AM in FDM showed deviation between nominal dimensions and measurements of ±0.1% (one sigma, 68% of measurements) and PolyJet ±0.15%. Personal web-based AM in SLA exhibited deviation ±0.3% and SLS in polyamide ±0.4% (one sigma). The PolyJet part showed dimensional instability under harsh environment and would require immediate 3Dformwork. The FDM part presented the lower cost for the particular case study among the professional AM. Thus, high quality PolyJet and FDM additive manufacturing in plastics are at the verge of achieving the requirement of 0.1% minimum accuracy for stellarator coil windings. Therefore, AM may contribute to the fabrication of accurate winding structures for stellarators and other accurate components in fusion.

The ITER equatorial visible and infrared Wide Angle Viewing System (WAVS) provides surface temperature measurements of plasma facing components by infrared (IR) thermography being one of its main roles to protect them from damage. It also images the plasma emission in the visible range. The diagnostic, which comprises 15 lines of sight distributed in four equatorial ports (3, 9, 12 and 17), will contribute to Machine protection, Basic control and Physics analysis in ITER. The design of the diagnostic in the equatorial port 12 (EP12) - comprising three lines of sight - is currently being developed within a Framework Partnership Agreement through a Specific Grant granted by F4E to the Consortium formed by CEA, Ciemat and Bertin Technologies. EP12 has to be operative for the ITER first plasma. The overview of the WAVS opto-mechanical design for the ex-vessel components in EP12 will be presented in the paper. The ex-vessel optics are composed of mirrors and refractive elements which relay the exit image of the port plug at the vacuum window up to the cameras placed inside a shielded cabinet in the Port Cell. The image relay through the Interspace, Bioshield and Port Cell has to cover a length of almost 10 m in order to reach the detectors. The refractive elements are arranged in sub-assemblies (optical modules) mechanically mounted in barrels and next assembled on a support structure. The assembly of these modules on site will be also presented in the paper. Furthermore, the Optical Hinge which is the first component of the ex-vessel optical chain (formed by two folding mirrors) aims to compensate the differential motion between the vacuum vessel and the building, in normal operation and baking. The mechanical assembly and the operation of this component will be also described in the paper.

Stellarator advancement is hindered, among others, by the requirement of geometric complexity at high accuracy and the still scarce universities and research centres following the stellarator line. In this framework, the objectives of the small UST_1 stellarator development were to: (i) explore and test the performance of one possible accurate construction method for stellarators (ii) encourage universities and small fusion research centres to build simple and economical stellarators (iii) educative purpose. Therefore, UST_1 was properly designed to be easily built by a milling machine working on toroidal coordinates, being the winding surface circular poloidally and toroidally. The coil frame is a sole monolithic toroidal thick surface equipped with grooves mechanised by the toroidal milling machine. Only one double pancake is wound in each groove so as to compress the conductor on the laterals of the groove in order to speed up and simplify the winding process. The physics design, the conceptual engineering design and the construction process of UST_1 is presented. The toroidal milling machine is described. The e-beam field line mapping experiments carried out to validate the resulting magnetic configuration are reported. The developed construction method has been proved for the small UST_1 stellarator. Small stellarators are valuable for quick tests of diagnostics, educative purposes, assessment of new confinement concepts, turbulence studies and other applications.

The geometric complexity and high accuracy simultaneously required in magnetic fusion devices, particularly stellarators and tokamaks, hampers the production of fusion components and devices. Rapid manufacturing construction methods, particularly enhanced for fusion, may contribute to a faster cycle and lower cost production of certain components for tokamaks and stellarators. Casting, cutting, forming, welding and mechanising are conventional production techniques for major fusion components, i.e. coil casings, coil frames, vacuum vessels and blankets. Synergies may emerge by combination of additive manufacturing (3D printing) with conventional manufacturing methods. 3D printing combined with resin moulding is tested by construction of the coil frame and the vacuum vessel of a small stellarator, UST_2. Satisfactory coil frames have been obtained by moulding acrylic resin in a special 3D printed polyamide hollow three-dimensional structure. The conceptual engineering design, construction process and validation of the components are described. The presented manufacturing method might contribute to advance the future 3D printing of larger metallic components for fusion.

Geometric complexity of stellarators hampers a straightforward production of conceived optimised magnetic configurations. Integration of the engineering design with new fabrication methods may reduce the production cost and accelerate the production process. A fast cycle production of experimental fusion devices also might result in a faster advance in fusion plasma science. Several different stellarators could be used to test configurations for improved turbulent transport or to validate new divertor configurations. In this framework, and based on the results from the previously built UST_1 stellarator, the present work try to study and validate the feasibility of 3D printing methods (additive manufacturing) for small experimental stellarators. The paper summarises the engineering development, fabrication and validation of a coil frame test sector for the UST_2 stellarator. The definition of the Last Closed Flux Surface and winding surface for the test sector is based on an optimised quasi-isodynamic poloidal stellarator, modified for enhanced in-vessel remote handling manipulation and wide space for divertors. A Filled-sparse coil frame concept is developed to still keep low the cost in spite of the present expensive 3D printing materials and printers.

Physics of stellarators has been optimized up to excellence levels. In contrast, optimization and innovation in the engineering and construction of stellarators is still comparatively modest. Particularly for stellarators but also for tokamaks, geometric complexity, small dimensional tolerances and large size currently imply relatively high fabrication costs, delaying the evolution of the stellarator research line and also hindering tokamaks. In this framework, the small low-cost modular stellarator UST_1, built and operated in a private laboratory, may contribute to the background of cost-reasonable construction methods for small fusion devices, particularly stellarators. The paper summarizes the engineering development and fabrication of UST_1 coils and outlines possible engineering R&D lines for the enhancement of the UST_1 construction methods. UST_1 consists of 12 resistive modular coils wound in grooves mechanised on a single monolithic toroidal frame surrounding the vacuum vessel. A special milling machine working on toroidal coordinates was developed, tested and built in order to accurately mechanise the grooves in the monolithic frame.

EFDA finances a training programme called Goal Oriented Training Programme for Remote Handling (GOT RH), whose goal is to train engineers in Remote Handling for ITER. As part of this training programme, the conceptual design of the mechanical interface between Upper Port Plug (UPP) and Cask and Plug Remote Handling System (CPRHS) as well as the conceptual design of the needed tools for UPP Remote Handling is carried out. The paper presents the conceptual design of the UPP/Gripping Tool Interface. This includes the conceptual design of the gripping tool for introducing/removing the UPP in/from the ITER port and the mechanical features on both sides of the UPP/Gripping Tool Interface (e.g. alignment features, mechanical connectors, fasteners). In order to develop the design of the interface between UPP and CPRHS it is necessary to first identify the functional requirements of the Transfer Cask System (TCS) and the CPRHS, such as required degrees of freedom (DoF), required performances of system, geometrical constraints, loading conditions, alignment requirements, RAMI requirements. These requirements are the input data for the design of the interface between UPP and gripping tool and some of them are also described in the paper.

One of the most technically challenging activities of the IFMIF facility is the maintenance and the refurbishment of its components, and among these the target system appears to be critical since it is located in the most severe region of neutron irradiation (60 dpa/fpy). Two different target assembly systems have been developed: the first is known as integral target while the second one is based on the so called replaceable backplate bayonet concept. The present remote handling (RH) procedures developed for the refurbishment of the removable backplate foresee the removal of all the components from the upper part of the test cell. This operation has a strong impact on the intervention time for the backplate refurbishment which has to be repeated at least every year. Consequently the need to update the RH strategy for the refurbishment of this component becomes a precondition in order to fulfill the stringent requirement to enhance the duty cycle of IFMIF plant. In this paper two potential approaches are presented: the first relies on the possibility to perform all the refurbishment operations in situ in the test cell cavern, whilst the second one foresees to perform these operations off-line in a hot cell. Advantages and disadvantages of these approaches together with the RH requirements for the refurbishment operations of the backplate bayonet concepts are also reported.

Present pathway to fusion reactors includes a rigorous material testing program. To reach this objective, irradiation facilities must produce the displacement damage per atom (dpa), primary knock-on atom (PKA) spectrum and gaseous elements by transmutation reactions (He, H) as closely as possible to the ones expected in the future fusion reactors (as DEMO).The irradiation parameters (PKA spectra and damage function) of some candidate materials for fusion reactors (Al2O3, SiC and Fe) have been studied and then, the suitability of some proposed experimental facilities, such as IFMIF and TechnoFusion, to perform relevant tests with these materials has been assessed.The following method has been applied: neutron fluxes present in different irradiation modules of IFMIF have been calculated by the neutron transport McDeLicious code. In parallel, the energy differential cross sections of PKA have been calculated by using the NJOY code. After that, the damage generated by the PKA spectra was analyzed using the MARLOWE code (binary collision approximation) and custom analysis codes. Finally, to analyze the ions effects in different irradiation conditions in the TechnoFusion irradiation area, the SRIM and Marlowe codes have been used. The results have been compared with the expected ones for a DEMO HCLL reactor.

A coherent design of the remote handling system with the design of the components to be manipulated is vital for reliable, safe and fast maintenance, having a decisive impact on availability, occupational exposures and operational cost of the facility. Highly activated components in the IFMIF facility are found at the Test Cell, a shielded pit where the samples are accurately located. The remote handling system for the Test Cell reference design was outlined in some past IFMIF studies. Currently a new preliminary design of the Test Cell in the IFMIF facility is being developed, introducing important modifications with respect to the reference one. This recent design separates the previous Vertical Test Assemblies in three functional components: Test Modules, shielding plugs and conduits. Therefore, it is necessary to adapt the previous design of the remote handling system to the new maintenance procedures and requirements. This paper summarises such modifications of the remote handling system, in particular the assessment of the feasibility of a modified commercial multirope crane for the handling of the weighty shielding plugs for the new Test Cell and a quasi-commercial grapple for the handling of the new Test Modules.

A diagnostic based on a set of fission ionization chambers is proposed for the IFMIF Test Cell in order to achieve on-line control of the irradiation parameters. These chambers are widely used in fission reactors; however the IFMIF environment (neutron spectrum, high neutron fluxes, gamma doses, reduced space, etc. …) requires a careful design of the whole diagnostic. This work shows the current status of the diagnostic development, which is being performed in the framework of the Broader Approach activities. The definition of the diagnostic strategy is addressed to establish the main specifications and requirements of the IFMIF fission chambers and their deployment. The map that the signal of a set of fission chambers will supply has been assessed by taking into account their sensitivity, their positioning inside the Test Cell and the IFMIF neutron flux. The results show that this experimental system will be capable of measuring and characterizing the high neutron fluxes expected for IFMIF.