Densities of Supercritical Fluids Containing CO2 and Tri-n-butylphosphate

Sawada, Kayo; Tomioka, Osamu; Shimada, Takashi; Mori, Yukihide; Enokida, Youichi; Yamamoto, Ichiro

doi:10.3327/jnst.43.98

J. Nucl. Sci. Technol.

2006

DOI: 10.3327/jnst.43.98

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Densities of Supercritical Fluids Containing CO2 and Tri-n-butylphosphate

Kayo Sawada

Osamu Tomioka

Takashi Shimada

et al.

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Cited by 2 publications

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“…Based on study a schematic flowsheet for SNF reprocessing using CO 2 as diluent was suggested. Based on the data from Russia, United States, Japan, United Kindom and India, Super-DIREX ( Super Critical Fluid Direct Extraction, Mitsubishi)) process was suggested in Japan97,98 . In Super-DIREX, SC-CO 2 containing TBP-HNO 3 adduct is fed toThe whole SFE process is matter of choosing suitable complexing ligand which can efficiently complex with metal ion.…”

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Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

Kumar¹

2022

J. ISAS

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In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

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Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

Kumar¹

2022

J. ISAS

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“…[1][2][3][4][5][6][7][8] Among these studies, a method has been studied in which decladded spent fuels are "directly" treated by the supercritical fluid, a single-phase mixture of HNO3, H2O and tri-n-butylphosphate (TBP) in supercritical carbon dioxide (SC-CO2). [9][10][11] Here, "directly" means "without a dissolution process".…”

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Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO3 and H2O in Supercritical CO2

et al. 2006

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Several studies have been performed to extract actinides from the spent nuclear fuels using supercritical fluids. [1][2][3][4][5][6][7][8] Among these studies, a method has been studied in which decladded spent fuels are "directly" treated by the supercritical fluid, a single-phase mixture of HNO3, H2O and tri-n-butylphosphate (TBP) in supercritical carbon dioxide (SC-CO2). [9][10][11] Here, "directly" means "without a dissolution process". For the decladding process, the spent fuel is treated thermally in air and is pulverized by the stress of the swelling through oxidation of UO2 to U3O8 during the cladding. Uranium and plutonium in the solid fuel can be directly extracted into the supercritical fluid. The single-phase mixture of HNO3, H2O and TBP in SC-CO2 is reactive with U3O8. 8,12,13 As a result of the reaction, the uranium oxide is converted into UO2(NO3)2 and extracted as UO2(NO3)2·2TBP in the supercritical fluid. The dissolution and extraction simultaneously proceed in this series of reactions. Because uranium and plutonium are extracted from the spent fuel into the supercritical fluid, the fission products in the spent fuel can remain as solids. Therefore, the direct extraction can decrease the amount of secondary radioactive wastes by omitting the acid dissolution processes, which usually generates a large amount of highly radioactive liquid waste. This technique investigated in these studies can be useful for analytical purposes, because the minimization of the waste solution in the chemical analyses for process management becomes very important in spent nuclear fuel reprocessing plants.In an extraction process for nuclear fuel reprocessing, a higher extraction capacity and higher decontamination ability are desirable. For the former, the contact time of the spent fuel and supercritical fluid is long enough, over 2 min, and an equivalent extraction capacity for the TBP complex is expected. 9 For the decontamination nature, which is more sensitive to the chemical conditions during the direct extraction, we performed some experiments to evaluate the decontamination nature of the direct extraction process using a single-phase mixture of HNO3, H2O and TBP in SC-CO2. Prior to the experiments under high pressure, we performed the experiments at ambient pressure without SC-CO2 in order to determine the effect of SC-CO2 on the decontamination. Experimental ChemicalsAs simulated materials for the spent fuel, we prepared a mixture of U3O8 and metal or metal oxides as the fission products. The composition of the simulated fuel used in our experiments is as follows: U3O8 (92.22), SrO (0.40), ZrO2 (0.85), MoO3 (1.15), RuO2 (0.99), Pd (0.85), CeO2 (1.38) and Nd2O3 (2.16). The values in parentheses indicate the weight fraction of each chemical. The fraction of each element was proportional to the calculated results based on the ORIGEN-II computer code for PWR fuel of 45000 MWd t -1 . Based on the condition of the elements in the spent nuclear fuel, SrO, ZrO2, MoO3, RuO2, Pd, CeO2 and Nd2O3 were selected; these were...

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Densities of Supercritical Fluids Containing CO2 and Tri-n-butylphosphate

Cited by 2 publications

References 15 publications

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO3 and H2O in Supercritical CO2

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