Direct chlorination of UO2 to UCl3 is being developed to enable synthesis of fuel salt for molten chloride fast reactors from commercial spent nuclear fuel. If this process can be successfully developed at reasonable cost and minimal waste generation, it could be relevant for management of spent nuclear fuel as well as fueling the next generation of advanced nuclear reactors. The studied approach is based on work published by researchers from Japan involving reaction of ZrCl4 with UO2. In the experiments we will be reporting, NiCl2 was reacted with a metallic Zr rod in molten LiCl-KCl to produce dissolved ZrCl4. A stable concentration of 1 wt.% ZrCl4 in the molten salt was achieved over the course of a two-hour experiment when an initial 5 wt.% of NiCl2 was added to the salt. Despite the high saturated vapor pressure of ZrCl4, it remained dissolved in the molten salt over the course of the experiment. UO2 particles were then immersed in the salt along with a Zr metal rod. Concentration of U in the salt versus time as measured with inductively coupled plasma mass spectrometry (ICP-MS) will be reported. An important question to address is the relative ratio of UCl4 to UCl3 produced through this method. Results of electrochemical methods (cyclic voltammetry and open circuit potentiometry) will be reported to address this question. This preliminary work is a first step towards studying the direct introduction of ZrCl4 in the salt via sparging ZrCl4 vapor into the salt. This system will be explained and future experiments will be discussed.

Chlorination of UO2 to UCl3 in a molten LiCl-KCl using ZrCl4

ACS Fall 2021

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