Abstract
In the European DEMO program, the design development of a demonstration power plant (DEMO) is currently in its pre-conceptual phase. In DEMO, breeding blankets will use large quantities of lithium, enriched in the isotope lithium-6 (6Li), for breeding the tritium needed to feed the DT fusion reaction. Unfortunately, enriched lithium is commercially not available in the required quantities, which is threatening the success of future power plant applications of nuclear fusion. Even if the manufacturing of the breeding blankets is still two decades ahead of us, it is now mandatory to address the topic of lithium-6 supply and to make sure that a viable supply (and reprocessing) route is available when needed.This paper presents an unbiased systems engineering approach assessing a number of available lithium isotope separation methods by defining requirements, rating them systematically and finally calculating a ranking number expressing the value of different methods. As a result, we suggest using a chemical exchange method based on a lithium amalgam system, but including some important improvements leading to a more efficient and ‘clean’ process (the ICOMAX process) in comparison with the formerly used COLEX process. Furthermore, by modelling activities and experiments in the KIT mercury laboratory (HgLab Karlsruhe), it is shown which work has to be done in the next years to make sure that the technical-scale process is available in time to supply DEMO and future fusion power plants by middle of the 21st century.
Highlights
In the fusion reaction considered for power reactors, the hydrogen isotopes deuterium and tritium are being used as fuel
Using natural lithium as breeder material will not lead to a tritium breeding rate large enough for reactor self-sufficiency
The Aspen® model allows a variation of the reflux ratio and the separation factor and shows the impact on the number of required stages
Summary
In the fusion reaction considered for power reactors, the hydrogen isotopes deuterium and tritium are being used as fuel. Whereas deuterium is available on the market in sufficiently large quantities, tritium is not a primary fuel and has to be bred inside the reactor in so-called breeding blankets These are actively cooled metallic ‘boxes’, installed on the walls of the reactor’s vacuum vessel, and filled with lithium comprising materials (ceramics or eutectic fluids). The only possible solution to overcome this problem is increasing the content of 6Li to a level of some ten percent, strongly depending on the chosen breeding concept [2] This works, as the cross-section of Reaction (1.1) is much larger than that of (1.2) at the fusion neutron energy spectrum [3], leading to a much more efficient tritium breeding
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