Exploration of isotopic effects on liquid metal surface properties relevant to liquid plasma-facing
component development for NSTX-U.

Martin Nieto-Perez, Pennsylvania State University (Principal Investigator)
Daniel Andruczyk, University of Illinois at Urbana-Champaign (Co-Investigator)

PROJECT SUMMARY.

This proposal aims to investigate the effect of lithium isotopic makeup on some of its
physicochemical properties that are considered relevant for the design of liquid metal plasma facing
components. Extensive experimental studies have already been performed to obtain
physical and chemical properties of molten lithium in the context of liquid metal plasma facing
components (LMPFCs) for fusion devices. Exposure of these LMPFCs to the neutrons produced
by the fusion reactions helps to breed tritium, which is part of the fuel required in fusion devices.
Any eventual commercial fusion power plant will need to be self-sufficient in tritium, so the
breeding and burning rates must at least match; achieving this condition utilizing materials
containing the natural abundance of lithium will present a challenge, which might be overcome by
using materials enriched with the isotope 6Li for the operation of LMPFCs, since this isotope is
the one that is capable of breeding tritium more efficiently. Under that scenario, it is desirable to
know if the isotopic makeup of lithium has any effect on its physicochemical properties, which
ultimately impact the design and performance of LMPFCs systems.

This research can potentially advance the design of liquid metal systems, both for power exhaust
and fuel cycle, by determining the LMPFC design and operation implications of having a working
fluid with an isotopic make-up more closely resembling that expected in a commercial, quasisteady-
state fusion reactor that operates with enriched lithium components to achieve fuel self sufficiency.
Even if the effect is found to be negligible after the work on this proposal, it will
remove the existing uncertainty about the effect and move forward with designs using the known
properties.