Kinetics of UO3 dissolution in nitric acid saturated 30% TBP in a hydrocarbon diluent

et al. 2018

The complete recycle of used nuclear fuel (UNF) is desirable to recover the energy value from the remaining U and the higher actinides produced during fuel irradiation; however, the construction of a large-scale reprocessing facility is prohibitively expensive. A simplified flowsheet with a reduced equipment footprint is needed to improve the economic viability. To address this issue, we evaluated a hybrid process which combines the dissolution of UNF pretreated (oxidized) for tritium removal in a tributyl phosphate (TBP) solvent with the solvent extraction cycles required for recovery of the actinide and lanthanide elements. To demonstrate the feasibility of the hybrid process, we prepared actinide solid solutions containing selected fission product elements as surrogates for pretreated, irradiated light water reactor fuel. The distribution of the actinide and fission product elements was measured between the solvent and residual solids to determine dissolution efficiencies. Dissolution of the solid solutions in the TBP solvent was effective for the recovery of both the actinide and lanthanide elements. An increase in the TBP concentration and temperature improved the dissolution efficiencies for these elements. Two-stage dissolutions were successfully used to recover nearly all the actinides and most of the lanthanides from the solid solutions. Our data indicate that most of the fission products generated during fuel irradiation except for the lanthanides and Tc (based on data for Re) would remain in the undissolved solids. The Am/Cm, lanthanides, and other fission product are easily scrubbed from the solvent by contact with nitric acid generating a pure U/Np/Pu stream.

Section: Figure 1 Conceptual Headend Process For the Recycle Of Unfmentioning

confidence: 99%

Dissolution of Used Nuclear Fuel using a TBP/n-paraffin Solvent

et al. 2018

“…In the nitrate form, U can be dissolved (extracted) directly into TBP. The direct dissolution of the UO 3 product into TBP can also be achieved by using TBP pre-equilibrated with nitric acid [2]. Although, the direct dissolution of both UO 3 and UO 2 NO(NO 3 ) 2 into TBP has been demonstrated [3], the extent of dissolution of other components of UNF into a TBP solvent has not been investigated.…”

Section: Figure 1 Conceptual Headend Process For the Recycle Of Unfmentioning

confidence: 99%

Dissolution of Used Nuclear Fuel Using a TBP/N-Paraffin Solvent

et al. 2017

The dissolution of unirradiated light water reactor fuel pellets pretreated for tritium removal by an oxidizing gas was demonstrated using a solvent containing tributly phosphate which is used in the PUREX (Plutonium Uranium Reduction Extraction) process. Dissolution of pretreated fuel in tributyl phosphate could potentially combine fuel dissolution with two cycle of solvent extraction required for separating the actinide and lanthanide elements from other fission products. Simplified flowsheets which reduced the equipment footprint and facility size are needed to improve the economic viability of complete recycle of used nuclear fuel. Dissolutions were performed using used fuel surrogates prepared from both uranyl nitrate and uranium trioxide produced from the pretreatment process by adding selected actinide and stable fission product elements. In the laboratory-scale experiments, the U dissolution efficiency ranged from 80-99+% for surrogates prepared from either the nitrate or oxide forms of pretreated fuel. On average, 80% of the Pu and 50% of the Np and Am in the nitrate surrogate dissolved; however, little of the Np, Pu, or Am oxides which were added to the used fuel surrogate containing uranium trioxide dissolved. Approximately 60-90+% of the lanthanide elements (Nd, Eu, and Ce) in the 3+ oxidation state (as both nitrates and oxides) dissolved; however, little of the Ce in the 4+ oxidation state (as cerium oxide) was solubilized, which was consistent with the transuranic oxides. Only small amounts of Sr (0-1.6%) and Mo (0.1-1.7%) and essentially no Cs, Ru, Zr, or Pd in either used fuel surrogate dissolved.

“…The direct dissolution of the UO3 product into TBP can also be achieved by using TBP pre-equilibrated with nitric acid. [3] Although, the direct dissolution of both UO3 and UO2(NO3)2 into TBP has been demonstrated, [4] the extent of dissolution of other components of UNF into a TBP solvent has not been investigated. Uranium(VI), Pu(IV), Np(IV), and Np(VI) are extracted into TBP as their electro-neutral nitrate salts.…”

Section: Introductionmentioning

confidence: 99%

Dissolution of used nuclear fuel using a tributyl phosphate/n-paraffin solvent

Separation Science and Technology

et al. 2019

The complete recycle of used nuclear fuel (UNF) is desirable to recover the energy value from the remaining U and higher actinides; however, construction of a large-scale facility is extremely expensive. To address this issue, a hybrid process was evaluated in which UNF pretreated for tritium removal is dissolved in a tributyl phosphate (TBP) solvent. The distribution of the actinides and selected fission products was measured between the solvent and residual solids. Dissolution of these elements in the surrogate fuels was very effective. Most fission products from fuel irradiation except for the lanthanide elements would remain in the undissolved solids.