Fabrication of Cermet Nuclear Fuels Designed for the Transmutation of Transuranic Isotopes

Abstract

The Uranium Extraction (UREX) family of processes uses solvent extraction techniques designed to partition spent uranium and transuranic (TRU) isotopes from fission product waste. Once separated, the collective TRU elements (Np, Pu, Am, and Cm) can be recycled in advanced nuclear energy systems. A zirconium matrix cermet is proposed as a fuel form for this application. Processing methods have been designed to convert the TRU product and spent Zircaloy cladding into feed materials for the hot extrusion of the cermet fuel pins. The TRU conversion process is being developed using a surrogate mixture of uranium and cerium nitrate solutions to generate mixed oxide microspheres. The Zircaloy recovery process is a hydride-dehydride method that is being demonstrated at the bench scale. The powder products from these methods may be combined through hot extrusion into a cermet composite; demonstration experiments using zirconium powder and zirconia microspheres have been completed.

Hydride Formation Process for the Powder Metallurgical Recycle of Zircaloy from Used Nuclear Fuel

“…[2][3][4] As part of this effort, a 3-year demonstration project was initiated to develop a near-term storage option for TRU oxides isolated through UREX+ processing. [5,6] More specifically, a Zircaloy matrix cermet was considered as a storage form for TRUs with the understanding that the cermet also has the ability to serve as an inert matrix fuel form for TRU burning after intermediate storage. One of the goals for this project was to develop the processing methods required to transform used Zircaloy cladding and the effluent TRU nitrate solutions into a zirconium matrix cermet storage form.…”

“…The experimental apparatus consisted of a controlled atmosphere reaction vessel inserted into a horizontal tube furnace, as described by McDeavitt et al [5,6] The vessel is a closed-end alumina tube sealed with a gasketed stainless steel end cap that has been configured to allow the process gas to enter and exit the vessel as well as a thermocouple to monitor sample temperatures. The process gas enters the vessel through a coiled copper tube that delivers the gas within the sealed tube near the Zircaloy test specimen; the coil is inside the vessel in the heated zone of the furnace to preheat the process gases.…”