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Characterization of Size, Composition and Origins of Dust in Fusion Devices
Closed for proposals
Project Type
Project Code
F41025CRP
1490Approved Date
Start Date
Expected End Date
Completed Date
23 January 2013Description
The interaction of hot plasmas with the wall materials in a fusion machine such as ITER will cause material to erode from the surface and form dust particles. These dust particles will contain tritium in varying degrees, depending on their origins. The dust may also be toxic and pose a fire risk if released in an accident. Dust particles can also become electrically charged and interact with the plasma and electric fields, degrading the performance of the fusion device. The possible extremely important impacts of dust particles in fusion devices, such as ITER, have resulted in the International Fusion Research Council Subcommittee on Atomic and Molecular Data recommending the formation of a Coordinated Research Project on "Characterization of size, composition and origin of dust in fusion devices". An overall objective of this CRP will be accumulation of new scientific knowledge on dust to address these important issues for fusion research.
Specific objectives
The specific objective of this CRP is to generate data for use in determination of the particle size, composition and origins of dust particles in fusion devices. While some work has been done in this area, past studies have led the fusion community to realize that additional data on properties of dust are important in the development of future fusion devices. Specific data to be generated include optical properties of dust, such as spectroscopic data, including index of refraction, as a function of temperature, data on dust production rates, especially in transient events such as ELMs (edge localized mode) and on the efficiency of transformation of deposited layers to dust. Work will be undertaken to reduce uncertainties in existing data as well as generate new data where needed. In addition to experimental measurements, theoretical models will be assessed with the possible applications diagnostics and transport of dust in plasmas. Possible diagnostic methods will be examined and data needs for such methods assessed. The expertise represented in the potential participants should allow significant progress to be made in all of these areas.
Impact
With the choice of the toxic metal beryllium as the first wall material for experimental fusion energy devices such as JET and ITER, there has been much concern about the formation and properties of the beryllium dust that may form during the routine operation of these reactors, particularly as a result of plasma-wall interactions. JET and KSTAR have produced experimental data on such dust, and this CRP has helped to clarify the origins and morphology of dust particles.
Relevance
Since this CRP completed (in 2011), it has become clear that beryllium dust is not formed in the large quantities that was feared before large-scale experiments in KSTAR and JET (using the beryllium-clad ITER-like wall (ILW)): over 100 times less dust is produced than in similar devices with carbon walls under comparable conditions. Given the extreme toxicity of beryllium and the larger quantities used in ITER, the issue is still of concern and the findings and recommendations of this CRP are of great relevance to the operation of this and similar experimental devices in the future.