[en] Uranium in the solution is determined using an automatic analyzer operating in a discontinuous mode, based on the principle of direct uranium photometry using the Arsenazo III reagent. An envisaged development is discussed of automatic analyzers using data processing which would eliminate the human factor effect. (J.C.)

[en] The method of sampling from the autoclave, instrumentation used and the conditions of analysis are discussed. The analysis of gaseous products was performed using a gas chromatograph. The relative determination error was ±5% in the total series of results. Oxygen and oxides were determined in the products. (J.C.)

[en] The applications are discussed in in-service control of the uranium content in eluates and in ion exchangers, of an industrial spectrometric unit linked to a JPR 12 computer and of the gamma spectrometry method of uranium determination. The technique using the industrial spectrometric unit is based on synchronous counting of pulses in the basic channel (²³⁵U gamma radiation) and in the reference channel (²⁴¹Am). The use of radiometric systems of in-service control of the uranium content in eluates and in ion exchangers in agreement with the chemical analysis of samples increases the technical and economic importance of laboratory analytical chemistry. (J.C.)

[en] The possible determination was studied of gadolinium in the presence of uranium using atomic absorption spectrometry and electrothermal atomization. The unfavourable effect was studied of high uranium concentrations on gadolinium determination. The separation of gadolinium from uranium is mostly performed using ion exchangers or extraction. For determining the quality of nuclear fuel containing 0.1 to 10 mg Gd per 1 g UO₂, separation of gadolinium from the uranium fuel and its concentration are necessary. (J.C.)

[en] The application is described of isotachophoresis in the analysis of rare earth elements. The following electrolyte system was used in the separation of the individual lanthanides: leading electrolyte: 0.025 to 0.030 M NH₄⁺, 0.014 to 0.017 M α-hydroxyisobutyric acid, 0.2 to 0.4% of hydroxyethyl cellulose, and acetic acid up to pH 4.9 to 5.1; trailing electrolyte: 0.02 M uranyl acetate, pH 4.25. The separation and detection of a 10^-4 M mixture of lanthanides proceeded 45 minutes. The requirements are discussed placed by the physico-chemical basis of the method for its successful application. The advantage of the method is very low sample consumption. (J.C.)

[en] The application is discussed of X-ray fluorescence analysis in the study of geological materials, mainly in the determination of uranium and other elements in the liquid phase. The method guarantees sensitivity, accuracy and selectivity of determination and the possibility of automating the measuring and evaluation processes. A method of double correction for radiation scattered in the background was used to improve the accuracy of results, this in view of considerable differences in the contents of soluble components in the solutions. (J.C.)

[en] Automation is discussed of extraction spectrophotometric determination of uranium in a solution. Uranium is extracted from accompanying elements in an HCl medium with a solution of tributyl phosphate in benzene. The determination is performed by measuring absorbance at 655 nm in a single-phase ethanol-water-benzene-tributyl phosphate medium. The design is described of an analyzer consisting of an analytical unit and a control unit. The analyzer performance promises increased productivity of labour, improved operating and hygiene conditions, and mainly more accurate results of analyses. (J.C.)

[en] Methods are described of obtaining rare earth elements from natural raw materials with various contents of the elements. Atomic absorption spectrometry and X-ray fluorescence analysis are mainly used for the analysis of these raw materials, which requires the preparation of representative solutions by suitable decomposition of the raw material. The decomposition which depends on the material's phase composition is effected using inorganic acids or by sintering the sample with a mixture of anhydrous sodium carbonate and sodium peroxide, by leaching the melt with water and dissolving the precipitate in diluted HCl or HNO₃. A chloride solution (pH 1.1-1.2) is the most suitable medium for quantitative precipitation of oxalates of rare earth elements. (J.C.)

[en] The symposium on modern methods of analytical testing of technological processes held in October, 1985 in Czechoslovakia heard a total of 32 papers of which 11 were inputted in INIS. These papers deal with X-ray fluorescence determination of uranium in solutions, the separation of rare earth elements by oxalate precipitation, the application of fluorimetry in inorganic analysis, gadolinium determination in uranium ores, with isotachophoresis applications, nitrogen oxide determinations in gaseous products of pressure leaching of uranium ores, the development of automatic analyzers, the applications of an extraction spectrophotometric analyzer, and a radiometric system for controlling sorption and elution. (J.C.)

[en] The possibility is discussed of replacing chemical analyses in the laboratory by automatic analyzers in the field in association with continuous sampling. Attention is paid to the automation of analytical determination of uranium in solutions from hydrochemical mining. A direct spectrophotometric method was developed based on the reaction of UO₂²⁺ ions with the Arsenazo III reagent in a single-phase dioxane-ethanol-water medium. The results are discussed of Stage 1 of the project ''Development of chemical methods and equipment for automatic process control'' solved in the period 1981-83. Stage 2 (1983-86) is mainly devoted to the development and design of a modular analyzer for the determination of uranium and to microprocessor-based control systems. (J.C.)