1987 Fiscal Year Final Research Report Summary
NEPTUNIUM SEPARATION THROUGH PHOTOCHEMICALLY INDUCED PROCESS
| Project/Area Number |
60470159
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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 | UNIVERSITY OF TOKYO |
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Principal Investigator |
SUZUKI Atsuyuki Professor, University of Tokyo, 工学部, 教授 (50011135)
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| Co-Investigator(Kenkyū-buntansha) |
OKAMOTO Tsuyoshi Research assistant , University of Tokyo, 工学部, 教務職員技官 (40114425)
ENOKIDA Youichi Lecturer, University of Tokyo, 工学部, 講師 (40168795)
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| Project Period (FY) |
1985 – 1987
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| Keywords | PHOTOCHEMISTRY / NEPTUNIUM / LASER / NUCLEAR FUEL REPROCESSING / EXTRACTION CHROMATOGTAPHY / VALANCE ADJUSTMENT / 溶媒抽出 |
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| Research Abstract |
1 Laser photochemical processes offer much promise as alternative means of valence state adjustment in nuclear fuel reprocessing The photochemically induced redox reactions of Np were shown to occur in nitric acid solution, such as used in the Purex process. Since Np distribution between organic and aqueous phases depends upon Np valence state, it is possible to control Np concentration profile in the nuclear fuel reprocessing plant using laser photolysis. Most practically important situations involve the adjustment of trace quantities of Np.
2 In order to determine the valence state fraction under very low concentration where absorption spectrophotometry cannnot be used, the applicability of extraction chromatography has been studied. Np ions of different oxidation states can be qualitatively separated on chromatographic TBP-column by elution with dilute nitric acid and the fraction of valence state can be determined by alpha dosimetry. This method was used in the following experiments
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to determine the redox ratio by photolysis.
3 when Np nitric acid solution adjusted completely to Np(IV) by ferrous sulfamate was exposed to KrF excimer laser radiation (249 nm), oxidation to Np(V) occurred photochemically even in the presence of a reducing reagent in the starting solutions. The experimental results show that the photo-shift exists in equilibrium oxidation ratio after adequate irradiation time. The initial amount of ferrous sulfamate had lettle effect upon the photo-shift but delayed initiation of photo-oxidation. Reaction temperature didn't affect the photo-hift either. The residual Np(VI) was oxidised further by dark reaction after the laser radiation bing off.
4 Np(VI), which was prepared by KMnO4 was photochemically reduced to Np(V) in nitric acid solution by laser photolysis, even in the presence of a strong oxidising reagent in the initial solution. The most noticeable aspects of this photochemical reaction are; 1) Reduction ratio is increasing to a steady-state value governed by the solution condition. 2) Higher reaction temperature and lower acidity are preferred to obtain higher redution ratio. 3) Reduction ratio changes abruptly when laser radiation being off.
5 Extraction experiments were accomplised, in order to obtain more practical data for photochemical separation of Np. Np ions were adjusted to NpnIV) or Np(VI) completely by means of chemical reagents in advance. Solvent extraction operations using 30%TBP(70%n-dodecane) as organic phase were conducted both before and after laser irradiation. The experimental results show that laser irradiation results in significant decrease of the distribution coefficients of Np. Therefore Np valence state adjustment by the laser photochemical method can be incorporated with the conventional Purex process without majour modification.
6 These experimental results of Np rebox reactions were combined with the Purex process simulation code 'ADVANCED MIXSET'. Using this reformed computer code, laser irradiation in a mixser-settler has been shown of great value to control Np concentration profiles and to decontaminate Np from U in the Purex process. Less
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