Dissolution of Zirconium-Bonded, Monolithic, Uranium-Molybdenum Fuel for Uranium Recovery

Abstract

A potentially explosive uranium-zirconium or uranium-niobium intermetallic phase will be present in U-10Mo fuels fabricated with zirconium or niobium bonding layers. This intermetallic phase forms during fabrication and may grow during irradiation.

Dissolution Flowsheet for U-10Mo Scrap Generated from the Fabrication of High Performance Research Reactor Fuel

“…Stepinski et al and Jerden et al used this information as the basis for flowsheet recommendations for the dissolution of U-Mo scrap generated during the fabrication of USHPRR fuels. 3,4 Researchers at Argonne National Laboratory (ANL) performed small-scale dissolutions using 0.2 to 1.2 g of U-10Mo, U-8Mo-Zr, and U-10Mo-Zr foils to demonstrate flowsheets for the dissolution of HPPR fuel fabrication scrap. [5][6][7] The dissolution of off-specification fuel plates was simulated by dissolving small pieces of an Al-6061 alloy prior to the U-Mo-Zr foil.…”

“…14 These conditions are present during hot rolling and HIP operations used during USHPRR fuel fabrication. 4 Therefore, the dissolution flowsheet for the U-10Mo-Zr foil must be developed assuming that the UZr 2 phase is present in scrap foil and rejected fuel plates. Throughout the dissolutions performed in this medium, the alloys remained shiny and no trace of the explosive solids were detected.…”

“…The formation of stable Zr fluoride complexes (ZrF 4(aq) , ZrF 3 + , ZrF 2 2+ and ZrF 3+ ) allows the UZr 2 intermetallic phase to dissolve at a rate similar to the U metal and prevents the buildup of potentially explosive material. 4 1.4 Caustic Dissolution of U Metal Prior to designing the dissolution flowsheet for rejected U-10Mo-Zr fuel plates, the strategy for removing the Al cladding must be selected. Two options exist for the dissolution of the cladding material.…”

Options Analyses for Back-End of the Fuel Cycle for Ushprr U-Mo Monolithic Fuel

“…The presence of a Zr-bonding layer for the monolithic U-Mo fuel puts a difficulty on aqueous processing of this fuel. The interface between the U-Mo fuel and the Zr layer is likely to contain U-Zr compounds that can react explosively when dissolved in nitric acid alone [1,[7][8][9][10][11][12]. It is, therefore, common practice to dissolve fuels that contain U-Zr intermetallic compounds in nitric acid containing significant quantities of hydrofluoric acid.…”

Dissolution Flowsheet for Skull Oxide Generated during U-Mo Alloy Casting for High Performance Research Reactor Fuel

“…Stepinski et al summarized previous work used to develop dissolution flowsheets for irradiated U-Mo fuels as part of the NNSA's Fuel Fabrication Capability Project in 2008 2. The document provides a comprehensive review of U-Mo dissolution technology up to this date.Stepinski et al and Jerden et al used this information as the basis for flowsheet recommendations for the dissolution of U-Mo scrap generated during the fabrication of USHPRR fuels 3,4. Researchers at Argonne National Laboratory (ANL) performed small-scale dissolutions using 0.2 to 1.2 g of U-10Mo, U-8Mo-Zr, and U-10Mo-Zr foils to demonstrate flowsheets for the dissolution of HPRR fuel fabrication scrap [5][6][7].…”