1992 Fiscal Year Final Research Report Summary
REDOX BEHAVIOUR OF NEPTUNIUM IN PUREX EXTRACTION PROCESSES
| Project/Area Number |
03453166
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Nuclear engineering
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
INOUE Yasushi Tohoku University,Faculty of Engineering,Professor, 工学部, 教授 (60005858)
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| Co-Investigator(Kenkyū-buntansha) |
TOCHIYAMA Osamu Tohoku University,Faculty of Engineering,Associate Professor, 工学部, 助教授 (70005479)
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| Project Period (FY) |
1991 – 1992
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| Keywords | neptunium / nitrous acid / nitric acid / Purex process / solvent extraction / TBP / oxidation / kinetics |
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| Research Abstract |
In order to clarify the distribution behavior of neptunium in the Purex extraction processes, the equilibrium and rate of the extraction of neptunium into 30% TBP-dodecane were examined as a function of nitrous acid (3-6 M) and nitrous acid (10^<-4>-10^<-2> M) concentrations. It was shown that the rapid equilibrium between nitric and nitrous acids controlls the redox potential of the aqueous phase, which in turn controlls the ratio of the concentrations of extractable Np(VI) to unextractable Np(V). The redox potential can be quantitatively described with using the activities of nitric acid, nitrous acid and water in nitric acid solutions:
E/V = 0.951 + 0.058・log<@D7{HNO<@D23@>D2}<@D12@>D1(/){HNO<@D22@>D2}<@D11/2@>D1{H<@D22@>D2O}<@D11/2@>D1@>D7 By examining also the rate of the extraction of neptunium into TOPO-dodecane, the ratedetermining step was confirmed to be the oxidation of Np(V) to Np(VI) in the aqueous phase. The rate of the reaction was obtained to be:
k/h = 5.44 x {HNO_3}^<1.02>{HNO_2}^<0.56>
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Research Products
(2 results)
