Article ID Journal Published Year Pages File Type
7987395 Nuclear Materials and Energy 2017 9 Pages PDF
Abstract
The high heat flux areas on the vertical divertor targets in the ITER tokamak will consist of cuboid tungsten monoblocks bonded to copper cooling tubes. Three-dimensional ion orbit modelling is used to calculate the heating of tungsten monoblocks during ELMs at the inner vertical target, where the highest surface energy densities are expected. The presence of thin gaps between monoblocks results in exposed edges onto which the heat flux can be focused. ELM ions are focused by their gyromotion onto the magnetically shadowed, long toroidal edges of the monoblocks. The risk of monoblock edge melting is greater than the risk of full surface melting on the plasma-wetted zone. Alternative shaping solutions such as edge chamfering, filleting, and poloidal beveling do not show promise; the melt zone simply migrates to other locations on the monoblocks. Without ELM mitigation, there is a marginal risk of edge melting due to uncontrolled ELMs in the pre-nuclear phase of ITER operation, and an absolute certainty of it in the burning nuclear phase. To avoid edge melting altogether, the surface energy density would have to limited to less than 0.15 MJ/m2.
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Physical Sciences and Engineering Energy Nuclear Energy and Engineering
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