Electrical conductivity and X-ray diffraction studies on non-stoichimetric U₃O_8-x phase were carried out simultaneously in the range 765° ?? T ?? 995°C and 10^-4 ?? Po₂ ?? 1atm. The plot of logσ vs. log Po₂, showed many refractions which corresponded with the phase transitions determined by thermogravimetry reported in the preceding paper. Based on the data of both electrical conductivity and thermogravimetry, the non-stoichimetric defect structures of various U₃O_8-x phases are interpreted as consisting of singly charged oxygen interstitials (O i ') and doubly charged oxygen vacancies (Vo). Some of the X-ray diffraction lines were found to undergo splitting with decreasing oxygen partial pressure. These splits are qualitatively discussed in reference to the out-of-step structure model. The mechanism of electrical conduction in the high temperature hexagonal U₃O_8-x phases is surmised to be the hopping of small polarons.

View full abstract

The rate of accumulation of radioactive waste will rise with the increase of nuclear power generation. If the radioactive nuclides produced in nuclear power plants can be separated according to their half-lives, the measures for permanent disposal will be limited to the waste containing only the long-lived nuclides, and the volume of such waste will thereby be markedly reduced. The short-lived nuclides will decay away in a relatively short time, after which they will be disposed of without danger as non-radioactive waste.
Duolite CS-100R, which is a cation exchange resin of weakly acid type, and, when impregnated with citrate or iminodiacetate ion, Amberlite IRA-402, an anion exchange resin of strongly basic type, both showed strong affinities with the short-lived ⁵⁹Fe (45.6 day) and ⁶⁴Cu (12.8 hr), while such long-lived nuclides as ⁹⁰Sr (27.7 yr) and ⁶⁰Co (5.3 yr) were found to be expelled from the resin by Fe and Cu. With Amberlite IRA-402, ground and sifted to 40100 mesh and impregnated with citrate ion, through which the sample solution was passed at a specific space velocity of 25, about 90 % of the Fe and about 80 % of the Cu contained in the sample were absorbed in the resin, while all the long-lived radionuclides passed through.
If this resin is loaded in a column installed upstream of the conventional demineralizers of a nuclear power station, most of the short-lived nuclides will be separated from the long-lived radioactivity requiring permanent disposal, thus markedly reducing the amounts of waste requiring handling as permanent waste.

View full abstract

Trace impurities including Yb in commercially available Lu203 of high purity were determined by neutron activation followed by cation-exchange separation with a-hydroxyisobutyrate. After irradiation in reactor, the Lu₂O₃, together with about the same quantity of Yb carrier, was dissolved in HC1, and fed to a cation-exchange resin column. Lutetium, Yb, Tm and some other rare earths were eluted successively, using a-hydroxyisobutyrate and citrate solutions as eluants. The addition of Yb carrier facilitated the analysis of Yb which is difficult to separate from Lu, and this permitted the determination of Yb of quantities as small as a few ppm.
The impurities found present in this sample of Lu₂O₃ were : 0.26 ppm Sc, 395 ppm Yb, 150 ppm Tm, 12 ppm Tb and 2.3 ppm Eu.

View full abstract

Considering the three steps of (1) Deposition of iodine on the stainless steel, (2) Formation of metallic iodides, on the metal surface and (3) Sublimation of the iodides into the stream, the reaction rate between dilute iodine vapor and stainless steel in high-temperature argon stream was obtained. The rate was determined by shallow-bed method, using a thin bed of granular stainless steel. The apparent rate constant obtained from the reaction rate was expressed in reference to unit surface area of the stainless steel grains. The rate of deposition of radioiodine on the stainless steel was found to correspond to less than 10 % of the concentration of iodine in the stream.

View full abstract