Ceramic Pebble Production from the Break-Up of a Molten Laminar Jet
Oliver Leys  1, *@  , Patrick Waibel  2@  , Jörg Matthes  2@  , Regina Knitter  1@  
1 : Institute for Applied Materials - Karlsruhe Institute of Technology
Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen -  Germany
2 : Institute for Automation and Applied Informatics - Karlsruhe Institute of Technology
Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen -  Germany
* : Corresponding author

Lithium rich ceramic pebbles are required for tritium breeding in future fusion reactors. The pebbles will be installed in the form of pebble beds in the wall of the reactor and upon irradiation, will generate tritium to be used as a fuel for the fusion reaction. A melt-based process has been developed at the Karlsruhe Institute of Technology, which produces pebbles from the break-up of a molten jet. Synthesis powders are heated in a platinum alloy crucible to approximately 1400 °C, after which a pressure is applied to the system, forming a jet through a nozzle on the underside of the crucible. The jet then breaks up while entering a cooling tower, where the droplets are solidified using a liquid nitrogen spray system. The produced pebbles generally have sizes ranging from 250 to 1250 µm.

Recent research has focused on the optimisation of the jet break-up stage of the production process. An image processing algorithm (specifically written for this process), was used in conjunction with a high-speed camera to determine various jet and droplet characteristics shortly after ejection from the nozzle. Initial studies focused on the effects of the operating pressure and more recently, a method for applying desired frequencies to induce the jet break-up at high temperatures was developed. It has been shown that under controlled conditions, it is possible to produce a monodisperse break-up of the jet as well as change the droplet size and spacing. These studies resulted in a higher degree of monodispersity as well as a higher production yield.


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