Modified Zirflex Process for Dissolution of 1–10% U-Zr Alloy Fuels in Aqueous NH₄F-NH₄NO₃-H₂O₂

A Modified Zirflex process was developed in the laboratory for dissolution of 1–10 % uranium-zirconium alloy fuels clad in Zircaloy-2 to produce a nitrate solution from which uranium can be recovered by conventional solvent extraction methods. A flowsheet is presented for dissolution of 7% uranium-zirconium alloy in 5.4 M NH₄F-0.33 M NH₄NO₃. Enough 1 M H₂O₂ is added continually during dissolution to yield 0.13 M H₂O₂ in the final solution, neglecting the amount reacting. Dissolution of a 70-mil thick sample is complete in 1 hr. The solvent extraction feed is prepared by adding aluminum nitrate and nitric acid to the dissolver solution to yield a stable solvent extraction feed solution of 0.0075 M uranium, 0.25 M zirconium, 1 M aluminum, 2 M fluoride, and 1 M nitric acid. The off-gas is approximately 98.5% NH₆, 1% H₂, 0.3% O₂, and 0.2% N₂. Conventional stainless steel such as 309SNb or Hastelloy F appear to be suitable materials of construction with corrosion rates varying from 0.1 to 3.0 mils/month.