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Abstract  

The redox titration of antimony(III), labeled with125Sb(III), by potassium iodate was radiometrically investigated using the burette method and the standard series method. The stoichiometry of the redox process was determined. The redox valence (the number of equivalents per mol) of potassium iodate for the oxidation of antimony(III) to antimony(V) was found to be 6, differing from the results obtained using the usual visual indicator method, where the value was shown to be 4. This disagreement in the equivalents of potassium iodate for the oxidation of antimony(III) is discussed.

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Redox substoichiometry in isotope dilution analysis

V. The use of potassium bromate as the oxidizing agent in the analysis of metallic zinc for antimony

Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Kambara, J. Suzuki, H. Yoshioka, and Y. Watanabe

Abstract  

Radiometric titration of antimony(III) with potassium bromate in hydrochloric acid media using the standard series method provided much valuable informations on the titration errors which depended on the concentrations of the acid and antimony(III). The hydrochloric acid concentrations between 2.5 and 3.0M were found to be optimum for the oxidation of antimony(III) amounts of 4 μg or less. Under these optimum reaction conditions the redox substoichiometric isotope dilution analysis was applied to the determination of antimony in metallic zinc and the satisfactory results were obtained, without the separation of matrix element. Also, the merits of various oxidizing agents hitherto studied for the quantitative oxidation of antimony(III) were compared and discussed.

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Redox substoichiometry in isotope dilution analysis

II. Determination of antimony content in metallic zinc

Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Kambara, J. Suzuki, H. Yoshioka, and N. Nakajima

Abstract  

Isotope dilution analysis using the redox substoichiometric principle has been applied to the determination of antimony content in metallic zinc. As the substoichiometric reaction, the oxidation of trivalent to pentavalent antimony with potassium permanganate was used, followed by separation of these species by the BPHA extraction of trivalent antimony. Determination of antimony contents less than 0.5 μg was found to be possible with good accuracy, without separation of zinc ions. The antimony content in metallic zinc was determined to be 19.7±0.8 ppm, in good agreement with the results obtained by the other analytical methods.

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Abstract  

Positron lifetime spectra were measured as a function of the time for metallocene polyethylene (mPE), poly(methyl methacrylate) (PMMA), polyamide (PA), and polycarbonate (PC). A decrease in o-Ps intensity with the elapsed time was observed in mPE and PC measured at room temperature and in PMMA measured at 225 K. Formation of free radicals has been supposed to be one of the causes of this effect. The effect of maleic-anhydride (maH) grafted copolymers and its ionomers in mPE/PA blends was also studied. The change in the positron lifetime distribution with increasing maH and the ionomer content revealed an enhanced interaction between mPE and PA phase and the decrease of dispersed mPE particles, which reflected good compatibility of the blend.

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Abstract  

In order to be more confident of the performance assessment of high-level radioactive waste disposal, radionuclide transport must be investigated in more detail in the disturbed host rock region adjacent to the engineered barriers where disturbance has been introduced during the construction and waste-emplacement period. Geochemical, hydrological, and rock-mechanical properties should be quite different from those of undisturbed host rock. We have to elucidate the effect of bentonite intrusion into intersecting fractures from the standpoint of radionuclide confinement. In the present work, sorption distribution ratios (Kd's) of Np and Am are measured experimentally for various values or redox potential (Eh) in a simulated rock fracture filled with bentonite. The Kd of Am is approximately 6.5×103 ml/g and found to be insensitive to the redox potential. Under anaerobic conditions, the Kd of Np is approximately 6×104 ml/g. Under aerobic conditions, Kd is as small as 30 to 100 ml/g. This is the first report to measure the sorption behavior of Np and Am in a simulated rock fracture filled with bentonite (namely, in a disturbed zone) under pH, Eh and ionic strength control. We aan make use of these Kd data for numerically evaluating the mass transfer from bentonite filled fractures into the water-flowing fracture network1.

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Abstract  

A radiometric method based on the redox substoichiometry has been developed for the determination of tellurium. The oxidation of tellurium(IV) to tellurium(VI) with potassium dichromate was employed as the substoichiometric reaction, followed by TBP (tributyl phosphate) extraction of the unreacted tellurium(IV) as the substoichiometric isolation. The oxidation of tellurium(IV) with dichromate under the substoichiometric conditions was incomplete. The chemical yield of tellurium(VI) produced by the oxidation of tellurium(IV) with dichromate was 83%. It was found that a tellurium content of 50 to 160 g could be determined with an accuracy of ±1.3% by means of the comparison method.

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Redox substoichiometry in isotope dilution analysis

IV. Determination of antimony content in metallic tin

Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Kambara, J. Suzuki, H. Yoshioka, and Y. Ugai

Abstract  

The oxidation reaction of antimony(III) with potassium dichromate has been investigated radiometrically. The quantitative oxidation of antimony(III) was found to be not disturbed even in large amounts of tin(IV). On the basis of these results the redox substoichiometric isotope dilution analysis using potassium dichromate as the oxidizing agent was proposed for the determination of antimony in metallic tin. The antimony content of 1.22±0.05 μg in metallic tin (10 mg) was determined without separation of the matrix element.

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Summary  

We present a new trial to measure real time water movement in a living plant using the positron emitting radionuclide, 15O. 15O was prepared by 14N(d,n)15O reaction and 10 ml of 15O labeled water (2 GBq) was supplied from the root of a soybean plant. To detect activity, an imaging plate (IP) as well as a BGO detector system were used. Since the half-life of 15O is extremely short, (T 1/2= 122 s), water uptake measurement was performed only for 20 minutes. In order to get [15O]waterimage, an IP was exposed to the plant for 1 minute for two times. Since the exposure to an IP requires dark condition, a BGO detector system was developed to measure [15O]waterunder light condition. A couple of BGO probes was set at the lowest stem and the gamma-rays (0.511 MeV) emitted from the radionuclide were measured through coincidence counting and compared with the radioactivity measured from an IP image. Using this system, we have found that the water uptake activity of the plant was drastically reduced under high humidity (99%) and dark condition.

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Abstract  

We have constructed a new system which could analyze a position distribution of several elements in a sample with 2 dimensional prompt γ-ray analysis (2D PGA) system using focused neutron beam at JAEA. We aimed that the system could analyze local information in a sample with a good signal γ-ray from interested elements to noise of background γ-ray ratio. As a result, this system could determine the position resolution and spatial resolution within 1 mm.

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