Progress, since the ITER Physics Basis publication (ITER Physics Basis Editors et al 1999 Nucl. Fusion 39 2137–2664), in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are energy transport in the scrape-off layer (SOL) in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main-chamber material elements, edge localized mode (ELM) energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low- and high-Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma–materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas: refinement in the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral–neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma–materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed.

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Chapter 4: Power and particle control

https://pure.mpg.de/pubman/item/item_2141173_1/component/file_2141172/RothPSI08_Paper_v9.pdf

Recent analysis of key plasma wall interactions issues for ITER

Materials for the plasma-facing components of fusion reactors

Plasma facing and high heat flux materials-needs for ITER and beyond

This paper presents the results of a preliminary assessment conducted to estimate the thermal response and erosion lifetime of the ITER divertor targets clad either with carbon-fibre composite or tungsten during type I ELMs. The one-dimensional thermal/erosion model, used for the analyses, is briefly described. It includes all the key surface heat transfer processes such as evaporation, melting, and radiation, and their interaction with the bulk thermal response, and it is based on an implicit finite-difference scheme, which allows for temperature-dependent material properties. The cases analysed clarify the influence of several ELM parameters on the heat transfer and erosion processes at the target (i.e. characteristic plasma ELM energy loss from the pedestal, fraction of the energy reaching the divertor, broadening of the strike-points during ELMs, duration and waveform of the ELM heat load) and design/material parameters (i.e. inclination of the target, type and thickness of the armour material, and for tungsten only, fraction of the melt layer loss). Comparison is made between cases where all ELMs are characterized by the same fixed averaged parameters, and cases where instead the characteristic parameters of each ELM are evaluated in a random fashion by using a standard Monte Carlo technique, based on distributions of some of the variables of interest derived from experiments in today's machines. Although uncertainties rule out providing firm quantitative predictions, the results of this study are useful to illustrate trends. Based on the results, the implications on the design and operation are discussed and priorities are determined for the R&D needed to reduce the remaining uncertainties.

https://iopscience.iop.org/article/10.1088/0741-3335/45/9/301/pdf

Assessment of erosion of the ITER divertor targets during type I ELMs

Key ITER plasma edge and plasma–material interaction issues

agenzia nazionale per le nuove tecnologie, l' energia e lo sviluppo economico sostenibile A long-term perspective on fusion is mandatory since Europe has a leading position in this field and major expectations have grown in other ITER parties on fusion as a sustainable and secure energy source. China, for example, is launching an aggressive programme aimed at fusion electricity production well before 2050. Europe can keep the pace only if it focuses its effort and pursues a pragmatic approach to fusion energy. With this objective EFDA has elaborated the present roadmap. ITER is the key facility in the roadmap: ITER construction is fostering industrial innovation on a number of enabling technologies. Its licensing, completion of construction and successful operation will be fundamental milestones towards the fusion power plant. Thus ITER success is the most important overarching objective of the programme. Still, the realisation of fusion energy has to face a number of technical challenges. For all of them candidate solutions have been developed and the goal of the programme is now to demonstrate that they will also work at the scale of a reactor. Eight different roadmap missions have been defined and assessed. They will be addressed by universities, research laboratories and industries through a goal-oriented programme detailed here for the Horizon 2020 period. This effort cannot be pursued only at European level – all the opportunities from international collaborations need to be exploited. According to the present roadmap, a demonstration fusion power plant (DEMO), producing net electricity for the grid at the level of a few hundred Megawatts is foreseen to start operation in the early 2040s. Following ITER, it will be the single step to a commercial fusion power plant. Defining, designing, building and operating DEMO requires the direct involvement of industry in the fusion programme that in the coming decades will move from being science-driven, laboratory-based towards an industry-driven and technology-driven venture. This transition requires strengthening the available engineering resources, and has to be facilitated already during Horizon 2020 by specific measures in support of training and education. The success of the roadmap relies on the assumption that adequate resources will be made available by the European Commission and the EURATOM Member States. Coherently with the pragmatic approach advocated here, resources will be focussed on few well-defined objectives. As a consequence, the amount of resources for the roadmap will not exceed the amount originally recommended by the …

Fusion electricity: a roadmap to the realization of fusion energy

To support a request of very substantial resources to build and operate an experimental reactor such as ITER, it is necessary to show that such a device is well positioned on the route towards a reactor and not too far from the reactor in parameter space. For the reactor definition, we choose to start from ITER design and to identify, using the same design tools as in ITER, which enhancements in physics and technology, would be necessary and possible to reach the performance required in a ‘first of a kind’ reactor. The conclusion of our analysis is that the 30 years ITER programme if successful and complemented by a few specialized test beds (e.g. neutron source) constitute a solid and sufficient basis from which to move directly and safely to a ‘first of a kind’ reactor, avoiding a further experimental step.

/pdf/how-far-is-a-fusion-power-reactor-from-an-experimental-2hgvidazjr.pdf

P. Barabaschi

Papers

Key ITER plasma edge and plasma–material interaction issues

Fusion electricity: a roadmap to the realization of fusion energy

How far is a fusion power reactor from an experimental reactor