1,721,549 research outputs found
Electromagnetic disruption analysis in IGNITOR
No full textThe present paper reports a detailed analysis of disruptions in the IGNITOR tokamak. Two different numerical models are used (one axisymmetric, the other three-dimensional), in order to validate the results and to highlight specific effects due to different assumptions. The results show a good agreement between the two codes, when similar assumptions are made, and highlight the potential significance of three-dimensional effects. © 2015 Elsevier B.V
Modelling of the Ignitor scrape-off layer including neutrals
No full textIgnitor is a tokamak project aimed at achieving ignition. In the reference scenario, plasma-surface interactions are controlled by a Mo first-wall/limiter, which constitutes a simple engineering solution but, at the same time, a special challenge for edge plasma modelling. Here the ASPOEL plasma fluid code, already applied to Ignitor in the recent past, is coupled with the neutral Monte Carlo code EIRENE. We study the effects of the neutrals on the plasma density and temperature profiles in the Ignitor scrape-off layer, and compute the particle and heat loads onto the Ignitor first-wall limiter
Modeling of long term effects on plasma facing components for a fusion power reactor
No full textIn a fusion power reactor the Plasma Facing Components (PFC) will experience a thermal and neutron irradiation induced creep together with tensile properties degradation and swelling due to neutron irradiation. So the investigation of the long term creep effects on the materials used for the PFC's in a fusion power plant are of vital importance for the design and safe operation of the device. On the other hand the creep behavior study for a given material requires long and expensive test campaigns, repeated on specimens at different levels of neutron irradiation, because of the material parameters variation due to the cumulated irradiation. In this work we want to investigate if the numerical mechanical simulations employment, according to a proper methodology, could reduce the number of needed creep tests, because this would be a valuable help in defining suitable materials and valid conceptual designs for PFC's. For this reason a method based on the systematic variation of the parameters of the empirical law, e.g. the Norton-Bailey, is outlined. To exemplify it, the behavior of a simplified model is analyzed under thermal and mechanical cyclic loading in a time transient elasto-plastic simulation, including the creep behavior, varying the parameters in the empirical creep law for the material
Innovative design for FAST divertor compatible with remote handling, electromagnetic and mechanical analyses
No full textDivertor is a crucial component in Tokamaks, aiming to exhaust the heat power and particles fluxes coming from the plasma during discharges. This paper focuses on the optimization process of FAST divertor, aimed at achieving required thermo-mechanical capabilities and the remote handling (RH) compatibility. Divertor RH system final layout has been chosen between different concept solutions proposed and analyzed within the principles of Theory of Inventive Problem Solving (TRIZ). The design was aided by kinematic simulations performed using Digital Mock-Up capabilities of Catia software. Considerable electromagnetic (EM) analysis efforts and top-down CAD approach enabled the design of a final and consistent concept, starting from a very first dimensioning for EM loads. In the final version here presented, the divertor cassette supports a set of tungsten (W) actively cooled tiles which compose the inner and outer vertical targets, facing the plasma and exhausting the main part of heat flux. W-tiles are assembled together considering a minimum gap tolerance (0.1-0.5 mm) to be mandatorily respected. Cooling channels have been re-dimensioned to optimize the geometry and the layout of coolant volume inside the cassette has been modified as well to enhance the general efficiency. © 2015 Elsevier B.V. All rights reserved
Modeling of Electromagnetic Loads on DEMO First Stage Divertor
No full textIn this work the analysis of the effects of the poloidal currents flowing on the cooling piping of the divertor armour tiles is carried out. To deal with the complexity of the problem a parametric solving scheme, starting from the nominal plasma current value, was adopted to contemplate the great variability of the possible cases deriving from the experimental data base and to compensate the lack of knowledge due to the not well assessed theory on the plasma wall interaction. Further to overcame the difficulties in modeling the real design of the piping with the necessary spatial resolution to individuate the local current concentration areas the methodology illustrated here is based on shell interfaces for solving either the electric and the mechanical problem. This approach proved to be capable to highlight the critical design areas and was useful to suggest the relative remedial corrections. © American Nuclear Society
Electromagnetic disruption analysis in IGNITOR
No full textThe present paper reports a detailed analysis of disruptions in the IGNITOR tokamak. Two different numerical models are used (one axisymmetric, the other three-dimensional), in order to validate the results and to highlight specific effects due to different assumptions. The results show a good agreement between the two codes, when similar assumptions are made, and highlight the potential significance of three-dimensional effects
Experimental studies with the improved CTS diagnostics on FTU and evidences of scattered wave signals with short time-scale.
No full textIgnitor-like Toroidal Devices for Neutron Production
No full textCompact fusion toroidal machines operating in DT have the potential to become efficient sources of neutrons for material testing. An Ignitor-like device could be envisaged for this purpose, making full use of the intense neutron flux that it can generate without reaching ignition. Preliminary radiation damage estimates for some fusion-relevant materials have shown that few full-power months of operation would provide adequate dpa levels. The main features and technological issues of a High Field Neutron Source Facility based on the Columbus concept, with about 50% more volume than Ignitor, are illustrated and discussed. Optimization of the plasma temperature and density relative to the reference ignition scenario (with the assistance of auxiliary heating power) can achieve considerable reductions of duty cycle requirements. The constraints imposed by flux availability, magnet heating and wall loading will inevitably impose a complete redesign of the machine, with the adoption of novel materials (such as MgB2 superconductor already adopted for Ignitor), and new modes of operation will need be investigate
Preliminary electromagnetic design for divertor of FAST
No full textFusion advanced study torus (FAST) has been designed with the aim to tackle the power exhaust problem with ITER and DEMO relevant bulk plasma. Considerable analysis effort has been spent in EM (electromagnetic) designing of FAST divertor components capable of withstanding the electromagnetic loads expected from the foreseen FAST operative conditions. Plasma disruption EM loads are one of the most critical load conditions for the divertor. Consequently a first dimensioning of the divertor for EM loads is mandatory. The foreseen FAST divertor structure is compact and the configuration is aimed to give to the structure the required mechanical and thermal capability as well as being remote handling compatible. The conceptual EM design of the divertor has been designed for FAST operative conditions and for DEMO relevant "Snow Flake" (SF) magnetic topology. Recently a "Snow Flake" (SF) magnetic topology has been suggested for the divertor region, capable to spread the plasma power flow on a much wider areas, with the possibility of reducing by a factor 4 the power flowing to the divertor tiles [1]. The conceptual design of the divertor has been obtained during activities based on the estimation of EM loads due to a typical Plasma Fast Down disruption event in FAST for the normal configuration and for SF magnetic topology. © 2013 Elsevier B.V
First disruption studies and simulations in view of the development of the DEMO Physics Basis
No full textIn the development of the DEMO Physics Basis an important role is played by the prediction of the plasma disruption features and by the evaluation of the electro-magnetic (EM) and thermal loads associated with these events. Indeed, the kind and number of foreseen plasma disruptions drive the development of the DEMO operation scenarios and the design of vessel and in-vessel components. To characterize a plausible macroscopic plasma dynamics during these events, we will carry out an extrapolation from present-day machines of the main parameters characterizing the disruptions: thermal and current quench time, evolution of plasma current, β and li, safety factor limits, halo current fraction and width, radiated heat fraction. In particular, we will focus on extrapolations for the thermal and current quench characteristic times, due to their importance for the subsequent simulations aimed at the evaluation of the EM and thermal loads. The different options for DEMO design will be taken into account and the possible range of variation of the parameters will be estimated. The 2D axysimmetric MAXFEA and the 3D CarMa0NL codes will be used to evaluate the effects of the induced currents and the EM loads during a disruptive event and to analyze the various design options obtained by the PROCESS code. The results of these simulations, modeled as worst expected events, will be used as input for the system level analysis and design of the vessel and relevant in-vessel components. First simulations with CarMa0NL code including 3D structures are here presented to show the significant effects due to the large access ports. © 2015 Elsevier B.V. All rights reserved
- …
