Experimental validation of 3D simulations of tungsten melt erosion under ITER-like transient loads

Базылев, Б.; Janeschitz, G.; Landman, I.; Loarte, A.; Federici, G.; Merola, M.; Житлухин, А. М.; Podkovyrov, V. L.; Климов, Н. С.; Linke, J.; Hirai, T.

doi:10.1016/j.jnucmat.2009.01.214

Cited by 42 publications

(40 citation statements)

References 7 publications

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“…JET results are consistent with simulations of tungsten melting and propagation using the MEMOS code [33], which has been used to inform decisions on the choice of tungsten as the material for the first divertor in ITER. The results have also given confidence that flash melting of the tungsten divertor elements by ELMs is relatively benign compared to bulk melting as reported in other experiments [34].…”

Section: Bulk Tungsten Melt Experimentssupporting

confidence: 57%

Overview of the JET results

Romanelli¹,

Abhangi²,

Abreu³

et al. 2015

Nucl. Fusion

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Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.

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Section: Bulk Tungsten Melt Experimentssupporting

confidence: 57%

Overview of the JET results

Romanelli¹,

Abhangi²,

Abreu³

et al. 2015

Nucl. Fusion

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“…During tokamak experiments the situation is quite different. In ITER the plasma pressure may reach 10 3 P a and even higher values during ELMs (10 4 P a) [18], hence only during ELMs a significant plasma pressure could be accessible to drive the melt. Under TEXTOR conditions F p is typically 200P a and thus small in comparison to F j×B which moves the material along the sample edge, perpendicularly to the magnetic field.…”

Section: Results and Measurementsmentioning

confidence: 99%

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

et al. 2011

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Behavior and characteristics of tungsten under impinging high heat-fluxes are investigated in view of the material choices for future devices such as ITER and DEMO. Experiments have been performed in the edge of the TEXTOR tokamak to study melt-layer motion, macroscopic melt layer erosion as well as the changes of the material properties. The parallel heat-flux ranges around q ∼ 45M W/m 2 allowing samples at an impact angle of 35 • to be exposed to 20 − 30M W/m 2 . Melt-layer motion perpendicular to the magnetic field is observed following a Lorentzforce originating from thermoelectric emission of the hot sample. Up to 3 g of tungsten are redistributed forming mountain like structures at the edge of the sample. The typical melt layer thickness is 1 − 1.5mm. Those hills are particularly susceptible to even higher heat-fluxes of up to the full q . Locally the temperature can reach up to 6000K, high levels of evaporation are causing significant erosion in form of continuous fine-spray (∼ 1 · 10 24 atoms m −2 s −1 ). Vaporshielding is occurring and hindering the further heating of the samples. In addition the formation of ligaments and splashes occurs several times during the melt phase ejecting droplets in the order of several 10µm up to 100µm probably caused by a Kelvin-Helmholtz instability evolving in the melt. In terms of material degradation several aspects are considered: formation of leading edges by redistributed melt, bubble formation and re-crystallization. Bubbles are occurring in sizes between µm and 200 µm while recrystallization increases the grain size up to 1.5 mm. The power handling capabilities are thus severely degraded. Melting of Tungsten in future devices is highly unfavorable and needs to be avoided especially in light of uncontrolled transients and possible unshaped PFCs

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“…Moreover the forces acting on the melt layer and the droplets will be different, because the plasma pressure will be much more dominant. In addition, the expected depth of the melt layer caused by transients will also be smaller [79], which also might influence its evolution. If tungsten is not the only PFM in a tokamak, mixed material effects could influence the performance of the W PFCs.…”

Section: Arcs and Meltingmentioning

confidence: 99%

Preparing the scientific basis for an all metal ITER

Neu

Taskforce²,

Contributors³

2011

Plasma Phys. Control. Fusion

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Abstract. The use of beryllium, carbon and tungsten as plasma-facing materials (PFMs) in ITER calls for dedicated investigations on their behaviour under the expected particle and power loads and neutron irradiation. Their simultaneous use implies the formation of mixed materials during plasma operation, which can have significantly different properties compared to the initial materials concerning thermo-mechanical behaviour and T retention. This contribution presents the latest results on these issues mainly achieved under the umbrella of the European taskforce on Plasma Wall Interaction. While laboratory results provide the basis for the understanding of the basic properties and the behaviour of PFMs, experiments in fusion devices are indispensable in order to test their integral performance, incorporating also the internal feedback on the plasma properties. For this reason ASDEX Upgrade has been converted to a full W device, while JET is beginning operation with its ITER-like wall consisting of a Be main chamber plasma-facing components and a W divertor. In parallel, dedicated W experiments are performed in several devices in order to investigate specific uncertainties such as the characteristics of melt layer movement in the presence of a strong magnetic field. Based on the results on ASDEX Upgrade, which reveal a narrower operational space as compared to the operation with graphite plasma facing components but also provide tools for a successful operation with tungsten, the experiments at JET will provide a unique opportunity to address specific issues related to the parallel use of Be and W as PFMs with plasma parameters closest to those of ITER. Amongst these are the anticipated but still to be demonstrated reduction in hydrogen retention compared to a carbon device, the test of conditioning procedures, mixed materials effects, erosion and transport, the effect of ELMs and ELM mitigation methods as well as the behaviour of melt layers and their influence on plasma operation under steady state and transient heat loads.

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Experimental validation of 3D simulations of tungsten melt erosion under ITER-like transient loads

Cited by 42 publications

References 7 publications

Overview of the JET results

Overview of the JET results

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

Preparing the scientific basis for an all metal ITER

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