Design and Analysis of a Metallic Uranium Reactor Type-Pump Using the Magnesiothermy Process

Abstract

This paper shows a methodology to obtain metallic uranium through a magnesiothermy process. Chile has two experimental reactors operated by the “Chilean Nuclear Energy Commission” (CCHEN). One is 5 MW and the other is 10 MW. In order to fulfill international agreements about nuclear energy for testing purposes of these reactors, CChEN purchased 19.9% enriched uranium hexafluoride, also known as the limit of Low Enriched Uranium (LEU). Due to the capacity of these reactors, they need high-density uranium compounds for their fuel, in order to work with LEU. For this reason, the uranium needs a previous conversion into metallic uranium. The conversion laboratory carried out experiences for reduction of UF4 with Mg. The main purpose of this study was to analyze the operating conditions under which the reduction reaction takes place, the designed method and the equipment and materials used. The raw material used was dehydrated UF4, prepared by electrolytic reduction and commercial purity Magnesium. The reaction took place in a cylindrical reactor made of low alloy steel, with a conic section in the lower part. The internal zone was coated with a 2.5 cm thick layer of CaF2. The process started by applying external heating, according to a heating program, developed specially for this purpose. The reduction reaction took place starting at 650°C. The result was a cylinder of uranium metal and MgF2 slag. The crossed cut uranium cylinder showed a smooth and homogeneous surface without inclusions of slag, pores or blisters. The yield of the reaction was of the order of 75% with respect to the expected theoretical value. The uranium cone obtained fulfilled the required conditions for source material for nuclear fuel fabrication, with a uranium content of 97.5%.