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

Abstract

The authors would like to acknowledge the support of the SRNL Glass Shop for not only constructing but helping to improve the design of glassware used in the dissolution experiments for the U-10Mo scrap recovery flowsheet development. The Glass Shop was able to modify equipment designs and refabricate needed glassware within a matter of days which allowed the project to proceed on schedule.

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

“…The objective for the flowsheets demonstrated for the skull oxide material was to use the same conditions as demonstrated for the dissolution of the U-10Mo-Zr foil and Al-clad U-10Mo-Zr mini-plates. 8 The flowsheet recommendations for the dissolution of the foil and mini-plates were to use a sufficient volume of 4 M HNO3 at the boiling point of the solution to achieve a final acid concentration greater than SRNL-STI-2022-00149 Revision 0 approximately 3.5 M when targeting either 20 or 50 g/L U. For dissolutions targeting 50 g/L U, 0.5 M Fe (as Fe(NO3)3) should be added to the solution to prevent the precipitation of uranyl molybdate.…”

“…Based on the scoping experiment, another dissolution (Exp.183) was performed by dissolving 5.01 g of the U-10Mo casting skull in 150 mL of 4 M HNO3, targeting a 20 g/L U solution with a final HNO3 concentration above 3.5 M. In previous work, it was determined that a final HNO3 concentration between 3.5 and 4.0 M was acceptable in terms of avoiding molybdate precipitates. 8 The final measured free acid for Exp. 183 was 3.6 M which was acceptable.…”

“…The UDS will need to be filtered and washed with fresh dissolving solution to minimize the loss of U to the interstitial liquid. The uranyl nitrate in the filtrate can then be purified using the solvent extraction flowsheets which were demonstrated for the foils and miniplates 18 and converted into metal for recycle to the HPRR fuel fabrication process.…”

“…The Savannah River National Laboratory (SRNL) was requested to develop dissolution flowsheets for casting and fuel fabrication scraps representative of streams shown in Figure 1-2 which will be processed for U recovery. 11,12 The casting scrap includes the U-10Mo skull oxide from alloy preparation. Skull oxide material generated during a U-10Mo casting was shipped from the Y-12 National Security Complex (Y-12) to SRNL for use in dissolution tests.…”

“…Fuel fabrication scraps including U-10Mo-Zr foil and Al-clad U-10Mo-Zr mini-plates were obtained from BWX Technologies, Inc. and were previously used for dissolution flowsheet development. 8 The skull oxide material was used in a series of experiments to demonstrate flowsheets which can be used to safely and efficiently dissolve the oxide material for subsequent U recovery. The dissolution processes were designed to accommodate downstream processing without significant solution adjustments to the extent possible.…”