Tomitaro Ishimori

SOLVENT EXTRACTION BEHAVIOR OF MACROAMOUNTS OF ELEMENTS IN 100% TBP-NITRIC OR HYDROCHLORIC ACID SYSTEMS

The acid dependence curves of 15 inorganic ions in macroamounts were surveyed for the system of 100% TBP-HC1 and HNO3, and compared with results obtained in tracer work previously reported. In most cases, theKd values measured in a system containing 0.1m/l salt are little different from those determined by radioactive tracers. The acid dependence behavior of ferric and zinc chloride were especially studied with varying metal ion concentrations. Additional experiments were carried out for ferric and zinc chloride in the system of 1 % (w/v) TBPO and 5 % (w/v) TOPO toluene-HCl. In these cases theKd values lowered with increasing chloride concentration.

URANIUM AMALGAM FROM AQUEOUS SOLUTION.

Abstract Various factors which influence the extractibility of uranium from aqueous uranyl solution with sodium amalgam have been investigated. Conditions for the virtually complete extraction of uranium from aqueous solution are described. Uranium amalgam containing more than 50 mg U/ml Hg has been obtained in one extraction.

Praseodymium-143 from Neutron-Irradiated Uranium

From neutron-irradiated uranium cooled for about 2 days, 143Pr was separated indirectly by solvent extraction. After removing uranium and some extractable nuclides with bis(2-ethyl hexyl)orthophosphoric acid from 10 M nitric acid solution, 143Ce was extracted with bis(2-ethyl hexyl) orthophosphoric acid (n-heptane diluent) from a 10 M nitric acid solution containing potassium bromate. Then, 143Pr was purified after most of the 143Ce had decayed off. Detailed measurements indicated a half-life of 13.55 ±0.02 days and maximum β-ray energy of 0.93±0.05 MeV.

Determination of small amounts of TBP and DBP in uranyl nitrate solutions.

Tri- and dibutylphosphate (TBP and DBP) in concentrated uranyl nitrate solution are determined by a method based on the solvent extraction of zirconium-95. The distribution ratio of zirconium-95 between dilute solutions of TBP and DBP in dodecane and 10M hydrochloric acid and 1Mnitric acid respectively is measured. There is a logarithmic relationship between the distribution ratio and concentration of TBP and DBP, which enables them to be determined rapidly and with an error of +/- 10% over the range 1-100ppm of TBP and 40-600 ppm of DBP. The lower limit is 0.5 ppm for TBP and 10 ppm for DBP.

A Method of Preparing of Cobalt-58

Carrier-free 58Co produced through (n, p) reaction, is usually prepared by ion exchange, but in this study the graded multistage solvent extraction method was successfully applied to the separation of 58Co from nickel. Nickel sponge of high purity was irradiated for 151ir in the JRR-1 reactor at Tokai. A dilute hydrochloric acid solution of about 0.2 mC of 58Co was obtained from l g of nickel sponge by the above mentioned method. The radiochemical purity was determined by means of γ-spectrometry and decay curve measurement.

Some Complex Compounds of Neptunium (IV) and Related Ions

Summary The phenylarsonate, oxalate, mandelate and ethylenediaminetetraacetate of neptunium (IV) were radiochemically surveyed by the solvent extraction technique. An equation given by SCHUBERT as well as another one evolved by ISHIMORI for the composition of complex compounds, were applied to the measured distribution ratios in a di-(2-ethyl-hexyl)-phosphoric acid-hydrochloric acid system containing a complexing agent. The determined molar ratios of the complexing agents: neptunium (IV) were 2, 4 and 1 for phenylarsonate, oxalate and ethylenediaminetetraacetate, respectively. No mandelate of neptunium (IV) was observed in the acidity range studied. The dissociation constants for most of the complex compounds were calculated.

Uranium Oxysulfide and Thorium Disulfide from Organic Extracts of Thiocyanates in Aqueous Solution

Uranium oxysulfide was prepared from 1-pentanol extract of uranium (VI) thiocyanate by vacuum distillation and calcination of the distillation residue. Thorium disulfide was similarly prepared from thorium thiocyanate complex in aqueous phase.

Uranium Dioxide from Uranyl Nitrate-Tri-n-Butyl Phosphate Solution

Uranium in uranyl nitrate-TBP solution was converted into dioxide by vacuum distillation and ignition. In vacuum distillation, TBP and its diluent were recovered at 40°–150°C in nitrogen stream under 1–5mmHg. The residue of distillation was incinerated in nitrogen stream with 0.1∼1.OmmHg by raising the temperature from 400° to 1,300°C. The final product is a black powder of UO2, identified by X-ray diffraction, by density measurement and by chemical analyses. Uranyl nitrate TBP solution is evolved during fuel reprocessing, and thus the vacuum distillation reported here could be applied to the solution in order to simplify the process.

FRACTIONAL EXTRACTION OF ZIRCONIUM, NIOBIUM, AND NEPTUNIUM WITH TRI-n-BUTYL PHOSPHATE.

Radioactive Zr, Nb and Np were separated from each other by a continuous fractional extraction method. The extraction of Zr and Nb was carried out with 1 % TBP in chloroform from the 10N hydrochloric acid solution of irradiated U. Under these conditions, Zr, Nb and Np could be extracted continuously with the organic solution, while U and other F.P. remained in the aqueous solution. Finally, Zr in the organic solution was back-extracted with concentrated hydrochloric acid containing 1sim;2 drops of hydrofluoric acid. The method is convenient for the separation of Zr, Nb and Np from the F.P. The distribution ratios in the extraction system have also been obtained for a number of radioactive nuclides.

Isolation of Radioniobium from γ-Irradiated Molybdenum Oxide

A reverse-phase chromatographic isolation procedure for Nb from Mo and Tc is given. The separation is performed with TBP (tri-n-butyl phosphate) on celite column. Molybdenum oxide was irradiated with 20MeV bremsstrahlung, which produces a mixture of 93mMo, 99Mo; 91mTc; 91mNb, 95mNb, 95Nb and 96Nb. The irradiation was applied to a 6 N HC1 solution of the target. Separation was repeated twice, which resulted in isolation of the radioniobium with a decontamination factor of 104 both for Mo and for Tc. Decay analysis of the activity showed that radioniobium thus separated was composed of 91mNb, 95mNb, 95Nb and 96Nb. The γ-spectrum of 96Nb was obtained by subtraction of the spectrum taken 119 hr after the end of irradiation from that of 74 hr.