Matae Iwasaki

Kinetic studies of the fluorination of uranium oxides by fluorine—I: The fluorination of U3O8 and UO3

Abstract The reactions of U 3 O 8 and UO 3 with fluorine have been studied in the temperature range from 350 to 440°C with a thermobalance. The overall reaction consists of two steps. In the first step reaction, these oxides change to uranyl fluorides and in the second to UF 6 . In the case of U 3 O 8 , the first step reaction influenced the rate of the second step, so that the formation of the UF 6 was slow at first, where an induction period was seen, and finally followed the linear law. The rate of the first step reaction of UO 3 was much faster than the second step, and the great part of the overall reaction followed the linear law. The activation energies of the second step reactions for U 3 O 8 and UO 3 were 21·3 and 22·0 kcal/mole respectively. An almost linear relationship was found to exist between the reaction rate and the partial pressure of fluorine. For U 3 O 8 , the formation rate of UF 6 was nearly proportional to the surface area determined by gaseous adsorption.

Preliminary study on sublimation separation of 99Mo from neutron- irradiated UO2

Abstract For the purpose of developing the method of separating 99 Mo from irradiated UO 2 by sublimation, fundamental studies have been made on the temperature dependencies of sublimation of 99 Mo, 132 Te and 103 Ru and also on the behavior of 131 I, which is an important nuclidee because of the hazardness. The irradiated UO 2 is converted to U 3 O 8 by heating at about 500°C in an oxygen atmosphere of 1 2 kg/cm 2 and then the nuclides are separated from U 3 O 8 by heating at 1200°C under vacuum. The sublimated 131 I is identified to be elemental iodine and iodide, and it is trapped on copper metal grains. The trapped iodine is recovered as HI by heating in H 2 gas at 550°C; it is radiochemically pure.

Tritium separation by laser multiple-photon dissociation of CDTCl2/CD2Cl2 mixture

Abstract Selective multiple-photon dissociation of CDTCl 2 in CD 2 Cl 2 was studied using a TEA CO 2 laser. The dissociation rate of CDTCl 2 had a maximum value at 927 cm −1 (P (38) line) irradiation. The frequency agreed with the calculated ν 7 vibrational frequency (929 cm −1 ) of CDTCl 2 within the accuracy of the calculation. The tritium enrichment factor β prod was obtained to be 29 −15 +156 at 3 Torr total pressure and at 907.8 cm −1 irradiation.

Fluorination behaviors of the complexes of RbFUF4 and CsFUF4 systems

Abstract The reaction behaviors between some complex fluorides of MFUF 4 system (M = Rb or Cs) and fluorine were investigated. In all the cases, uranium was oxidized to hexa-valent state at the temperatures between 300 and 500°C and M 2 UF 8 type complex was formed, except for the cases of 3MF·UF 4 type complexes. In the fluorinations of 3MF·UF 4 , products with the composition of M 3 UF 9 were formed. A change in the stability of RbFUF 6 systems with RbF/UF 6 ratio was also investigated.

The formation of Rb2UF8 by fluorination of RbF·UF4

Abstract The complex Rb 2 UF 8 was obtained by fluorinating the known complex RbF·UF 4 at 400°C with fluorine gas which was diluted to 10% with nitrogen. The reaction was as follows: 2(RbF·UF 4 )+2F 2 → Rb 2 UF 8 + UF 6 . The valence of uranium in this complex was confirmed to be in hexa-valent state by observing the visible and near-IR absorption spectra. The IR spectrum was also obtained and two strong absorptions were assigned to UF stretching and FUF bending vibrations.

Infrared Absorption Spectra of Potassium Uranium Fluorides

In the first paper of this series, a qualitative interpretation was given of the far infrared spectra of several sodium uranium fluorides in the NaF-UF4 system. The purpose of this work has been to obtain information concerning the U-F vibrations in the uranium complex fluorides in the KF-UF4 system and furthermore to relate the band location of the U-F stretching vibration with the change of valency states of uranium.

Normal coordinate analysis of potassium and rubidium fluoaluminates

Infrared absorption spectra of alkali fluoaluminate crystals MAlF4 (M: K and Rb) have been measured in the frequency region from 4000–30 cm−1. Both the intramolecular vibrations such as the Al–F bond stretching and the F–Al–F bending vibrations and the lattice vibrations due to the interaction between the inner complex and the outer ions have been observed in the frequency regions of 800–160 cm−1 and below 160 cm−1, respectively. A normal coordinate analysis of the crystal as a whole has been carried out on the basis of a simple valence force field. The force constants of the Al–F stretching, F–Al–F bending, and M · · · F interaction have been obtained and discussed in relation to the interatomic distances. It has also been found that the simple valence force field assumed here is adequate for these complex fluorides.

The infrared spectrum of tripotassium uranyl fluoride

Abstract The infrared absorption spectrum of tripotassium uranyl fluoride (K 3 UO 2 F 5 ) has been observed in the frequency region 4000-30 cm −1 . A normal coordinate analysis of the (UO 2 F 5 ) 3− anion, neglecting K + ions, has been carried out using Wilsons FG matrix method. On the basis of the results of this treatment, six of the nine bands observed for K 3 UO 2 F 5 are reasonably assigned either to the i.r.-active fundamentals or to i.r.-active combination tones for the inner (UO 2 F 5 ) 3− anion. The other three bands are assigned tentatively to the lattice vibration modes of outer K + ions with inner (UO 2 F 5 ) 3− anion. Brief discussions are also given on the force constants obtained for the U—O and U—F bonds in the (UO 2 F 5 ) 3− anion.

Chemical Analysis of Bromine Trifluoride

The chemical analysis of bromine trifluoride (BrF3) was studied with the view to establishing a method for determining the purity of this substance, as attained by vacuum distillation. The sample bromine trifluoride was hydrolyzed in NaOH solution. The fluorine in the bromine trifluoride was converted to fluoride (F-) by the hydrolysis, and could thus be determined by thorium nitrate titration(1). The bromine in the bromine trifluoride was converted to bromide (Br-), hypobromite (BrO-) and bromate (BrO- 3), and was determined by the Mohr method, after reducing the BrO- and BrO- 3 to Br- with hydrazine hydrate (H2NNH2-H2O). A value of 2.97±0.03 wes obtained as ratio of fluorine to bromine for purified bromine trifluoride, and 2.84 for unpurified bromine trifluoride. Prior to analyzing the sample bromine trifluoride the conditions for reducing BrO- 3 to Br- by hydrazine hydrate were studied, using KBrO3 solution as sample. It was found that the alkalinity of the sample solution and the reduction temperature...

Fluorination of Uranium Metal by Fluorine Gas

A study has been made on the fluorination of uranium metal chips to UF6 with fluorine gas in the temperature range of 100° to 400°C. The formation of UF6 was influenced by the concentration and the flow rate of fluorine gas and by the reaction temperature. The reaction occurred apparently above 200°C. Uranium metal was first converted to low fluorine content compound such as UF3 or UF4-x, then to UF4 and finally to UF6. The intermediate compounds were confirmed by X-ray analysis and by their color.