METHOD FOR DETERMINING NITROGEN CONTENT IN URANIUM HEXAFLUORIDE Russian patent published in 2021 - IPC C01G43/06 G01N27/62 

FIELD: nuclear industry.

SUBSTANCE: method is proposed for determining the nitrogen content in uranium hexafluoride (UHF) by measuring the intensity of the analytical signal - optical density in the test sample, including hydrolysis of the UHF sample with sodium hydroxide solution, reduction of nitrate and nitrite nitrogen to ammonia, separation of ammonia by distillation from an alkaline solution, absorption of released ammonia by solution sulfuric acid and the determination of the ammonia content by the spectrophotometric method with Nessler's reagent in cuvettes with an absorbing layer thickness of 50 mm relative to the "blank" sample solution, where the hydrolysis of the UHF sample is carried out from the UHF sample weighing 7.5÷10 g, reduction of nitrite and nitrate nitrogen in UHF is carried out using 3÷4 g of a mixture of Devard's alloy and zinc powder, taken in a mass ratio (1:5÷6) in finely divided form, the absorption of released ammonia is carried out with a solution diluted to 0.02÷0.1 M sulfuric acid, the measurement of optical density is carried out after adding Nessler's reagent in an amount of 1 cm3 at a wavelength of 421÷426 nm, according to the measured value of optical density according to the equation of the calibration dependence, built in the range from 2.5 to 50 mcg of nitrogen, calculate the mass of nitrogen, according to the found mass of nitrogen and the calculated mass of uranium in the sample, the mass fraction of nitrogen to uranium in UHFs is calculated, according to the relative total error of the analysis result established at P=0.95 for n=2, the confidence limits of the absolute error of the analysis result are calculated, the mass fraction of nitrogen to uranium in SPU, internal operational control of the method accuracy is carried out using control samples containing nitrate nitrogen in an amount of 0.55÷10 mcg/g uranium, prepared on the basis of high-purity UHF hydrolyzed with water, and the established standard for error control, the preparation of solutions of samples, samples for control and reagents is carried out using distilled water, additionally purified at a complex water purification plant, providing a specific electrical resistance of purified water of at least 18 Mohm⋅cm.

EFFECT: creation of such a method for determining the mass fraction of nitrogen in UHFs, which, excluding the disadvantages inherent in known methods, would provide a reliable determination of the nitrogen content in UHFs with its content at the level of 0.5÷1⋅10^-4 wt. to uranium.

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