112 research outputs found
The DEMO magnet system – Status and future challenges
We present the pre-concept design of the European DEMO Magnet System, which has successfully passed the DEMO plant-level gate review in 2020. The main design input parameters originate from the so-called DEMO 2018 baseline, which was produced using the PROCESS systems code. It defines a major and minor radius of 9.1 m and 2.9 m, respectively, an on-axis magnetic field of 5.3 T resulting in a peak field on the toroidal field (TF) conductor of 12.0 T.
Four variants, all based on low-temperature superconductors (LTS), have been designed for the 16 TF coils. Two of these concepts were selected to be further pursued during the Concept Design Phase (CDP): the first having many similarities to the ITER TF coil concept and the second being the most innovative one, based on react-and-wind (RW) Nb3Sn technology and winding the coils in layers. Two variants for the five Central Solenoid (CS) modules have been investigated: an LTS-only concept resembling to the ITER CS and a hybrid configuration, in which the innermost layers are made of high-temperature superconductors (HTS), which allows either to increase the magnetic flux or to reduce the outer radius of the CS coil. Issues related to fatigue lifetime which emerged in mechanical analyses will be addressed further in the CDP. Both variants proposed for the six poloidal field coils present a lower level of risk for future development. All magnet and conductor design studies included thermal-hydraulic and mechanical analyses, and were accompanied by experimental tests on both LTS and HTS prototype samples (i.e. DC and AC measurements, stability tests, quench evolution etc.). In addition, magnet structures and auxiliary systems, e.g. cryogenics and feeders, were designed at pre-concept level. Important lessons learnt during this first phase of the project were fed into the planning of the CDP. Key aspects to be addressed concern the demonstration and validation of critical technologies (e.g. industrial manufacturing of RW Nb3Sn and HTS long conductors, insulation of penetrations and joints), as well as the detailed design of the overall Magnet System and mechanical structures
Advance in the conceptual design of the European DEMO magnet system
The European DEMO, i.e. the demonstration fusion power plant designed in the framework of the Roadmap to Fusion Electricity by the EUROfusion Consortium, is approaching the end of the pre-conceptual design phase, to be accomplished with a Gate Review in 2020, in which all DEMO subsystems will be reviewed by panels of independent experts. The latest 2018 DEMO baseline has major and minor radius of 9.1 m and 2.9 m, plasma current 17.9 MA, toroidal field on the plasma axis 5.2 T, and the peak field in the toroidal-field (TF) conductor 12.0 T. The 900 ton heavy TF coil is prepared in four lowerature-superconductor (LTS) variants, some of them differing slightly, other significantly, from the ITER TF coil design. Two variants of the CS coils are investigated - a purely LTS one resembling the ITER CS, and a hybrid coil, in which the innermost layers made of HTS allow the designers either to increase the magnetic flux, and thus the duration of the fusion pulse, or to reduce the outer radius of the CS coil. An issue presently investigated by mechanical analyzes is the fatigue load. Two variants of the poloidal field coils are being investigated. The magnet and conductor design studies are accompanied by the experimental tests on both LTS and HTS prototype samples, covering a broad range of DC and AC tests. Testing of quench behavior of the 15 kA HTS cables, with size and layout relevant for the fusion magnets and cooled by forced flow helium, is in preparation.</p
Plasma physics and control studies planned in JT-60SA for ITER and DEMO operations and risk mitigation
| openaire: EC/H2020/633053/EU//EUROfusionA large superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMO have been clarified through those studies.Peer reviewe
Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation
WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017–2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m−2 were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described
Friction factor correlation for the central cooling channel in cable-in-conduit super-conductors for fusion magnets
Three steps of serpentinization in an eclogitized oceanic serpentinization front (Lanzo Massif - Western Alps)
International audienceThe Lanzo peridotite massif is a fragment of oceanic lithosphere generated in an ocean-continent transition context and eclogitized during alpine collision. Despite the subduction history, the massif has preserved its sedimentary oceanic cover, suggesting that it may have preserved its oceanic structure. It is an exceptional case for studying the evolution of a fragment of the lithosphere from its oceanization to its subduction and then exhumation. We present a field and petrological study retracing the different serpentinization episodes and their impact on the massif structure. The Lanzo massif is composed of slightly serpentinized peridotites (<20% serpentinization) surrounded by an envelope of foliated serpentinites (100% serpentinization) bordered by oceanic metabasalts and metasedimentary rocks. The limit between peridotites and serpentinites defines the front of serpentinization. This limit is sharp: it is marked by the presence of massive serpentinites (80% serpentinization) and, locally, by dykes of metagabbros and mylonitic gabbros. The deformation of these gabbros is contemporaneous with the emplacement of the magma. The presence of early lizardite in the peridotites testifies that serpentinization began during the oceanization, which is confirmed by the presence of meta-ophicarbonates bordering the foliated serpentinite envelope. Two additional generations of serpentine occur in the ultramafic rocks. The first is a prograde antigorite that partially replaced the lizardite and the relict primary minerals of the peridotite during subduction, indicating that serpentinization is an active process at the ridge and in the subduction zone. Locally, this episode is followed by the deserpentinization of antigorite at peak P-T (estimated in eclogitized metagabbros at 2-2.5 GPa and 550-620 °C): it is marked by the crystallization of secondary olivine associated with chlorite and/or antigorite and of clinopyroxene, amphibole and chlorite assemblages. A second antigorite formed during exhumation partially to completely obliterating previous textures in the massive and foliated serpentinites. Serpentinites are an important component of the oceanic lithosphere generated in slow to ultraslow spreading settings, and in these settings, there is a serpentinization gradient with depth in the upper mantle. The seismic Moho limit could correspond to a serpentinization front affecting the mantle. This partially serpentinized zone constitutes a less competent level where, during subduction and exhumation, deformation and fluid circulation are localized. In this zone, the reaction kinetics are increased and the later steps of serpentinization obliterate the evidence of this progressive zone of serpentinization. In the Lanzo massif, this zone fully recrystallized into serpentinite during alpine subduction and collision. Thus, the serpentinite envelope represents the oceanic crust as defined by geophysicists, and the sharp front of serpentinization corresponds to an eclogitized seismic palaeo-Moho
Investigations About Quench Detection in the ITER TF Coil System
22nd International Conference on Magnet Technology (MT), ITER Org, Marseille, FRANCE, SEP 12-16, 2011International audienceDue to the large stored energy (40 GJ) and the small allowed number of fast discharges (50), severe requirements have been put in the ITER project for the Toroidal Field (TF) coil system in comparison with the Poloidal Field (PF) and Central Solenoid (CS) systems, aiming at avoiding any fast discharge not related to a quench. A very important point, which has to be examined, is whether a quench detection based on a co-wound tape, recommended in the ITER project, and located inside the conductor insulation is compulsory to ensure the inductive voltage compensation. Another possible solution is the balance of the voltage of TF coils or TF coils subcomponents. The sensitivity of the quench detection systems is examined according to the different types of flux variations experienced in the machine. During plasma discharge, the sensitivity to poloidal flux variations and plasma paramagnetism is highlighted, the last effect being illustrated for Tore Supra. It is eventually recommended to select the quench detection by balancing coils or coils subcomponents. This solution has been adopted for Tore Supra, KSTAR and in JT-60SA project. The level of refinement should be adjusted during commissioning, as a function of the required voltage detection level (0.4 V) and to the required holding time (1 s)
Thrusting and sinistral wrenching in a pre-Eocene HP-LT Caribbean accretionary wedge (Samanà peninsula, Dominican republic)
Friction factor correlation for the central cooling channel in cable-in-conduit super-conductors for fusion magnets
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