卷 65, 编号 5 (2023)

A thermal analysis of a solution of acetohydroxamic acid in 12 mol/L HNO₃ was carried out. The activation energy, the speci c thermal e ect, the duration and rate of the exothermic reaction, the pre-exponential factor, the onset temperature and self-heating value of the sample, and the change in pressure and the speci c volume of the evolved gases were determined. It was shown that under experimental conditions this reaction proceeds in the autocatalytic mode. On the basis of experimental data, a kinetic equation for the reaction was obtained, which was used to create a model of the reaction under various conditions. The reliability of the simulation results was veri ed by di erential scanning calorimetry.

The in uence of HNO₃ concentration on the extraction of Eu(III), Am(III) and Cm(III) by N,N,N',N'tetrabutyldiglycolamide in 5 diluents (nitrobenzene, toluene, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane and chloroform) was studied. The dependence of the distribution ratios of the listed metals on the nature of the diluent was examined. The extraction of Eu(III), Am(III) and Cm(III) decreases in the following order: nitrobenzene > m -tri uoromethylnitrobenzene > mixture of n -dodecane and decanol-1 (90 : 10 vol/vol) > tetrachloromethane > 1,2-dichloroethane > benzene > 1,1,2,2-tetrachloromethane > toluene > chloroform. The conditions for the separation of Eu(III)/Am(III) and Am(III)/Cm(III) pairs were determined. The explanation of the observed increase of the Am(III)/Cm(III) separation factors with the increase of the nitric acid concentration in the equilibrium aqueous phase was suggested.

The paper presents the results of testing the puri cation of real liquid radioactive waste from radionuclides - bottom residues of the Kola and Beloyarsk nuclear power plants (NPP), as well as low-level wastewater from the radiochemical building of the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences (IPChE RAS) by the method of nano ltration (NF) using a polymer membrane manufactured by the Russian company «RM Nanotech». It has been shown that in the case of single-stage NF puri cation bottoms of the Kola (NPP), the coe cient of puri cation from ⁶⁰Co is 2.8, while puri cation from ¹³⁷Cs practically does not occur. When cleaning the bottom residues of the Beloyarsk NPP from ⁶⁰Co using a ve-stage scheme, a coe cient of puri cation from ⁶⁰Co equal to 388 was obtained. The combination of nano ltration puri cation and selective sorption of cesium on the ferrocyanide sorbent Temoksid-35 makes it possible to obtain a dry salt residue that is not related to radioactive waste. When using the method of nano ltration for the treatment of low-level wastewater of the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, the degree of puri cation was, %: ¹³⁷Сs ~ 75; ⁹⁰Sr ~ 91; ²⁴¹Am ~ 99.5; ¹⁵²Eu ~ 91; ²³⁹Pu ~ 99.5.

The ⁸²Sr/⁸²Rb generator is used to produce a medical radiopharmaceutical rubidium-82 chloride in saline solution for PET investigation. In this work, we studied the effect of the amount of stable strontium and calcium delivered to the sorbent (hydrated tin dioxide), on the maximum volume of radiopharmaceutical solution that can be obtained from the generator. Sr and Ca may be delivered to the sorbent from the initial solution of strontium-82 or from the eluent (0.9% NaCl) during medical application of the generator. It is shown that this volume depends on the value C_Sr + 0.11C_Ca, where C_Sr and C_Ca - molar concentrations of the elements in 1 g of the sorbent. The obtained results make it possible to increase significantly the productivity and reliability of the used generators.

Modern contamination of global and «Chernobyl» ¹³⁷Cs in lake-river systems bottom sediments is estimated. Drainage lakes of North-Western Russia were investigated. Kopanskoe Lake, located south of the Gulf of Finland, is on the trail of the «Chernobyl» ¹³⁷Cs fallout, whereas Ladoga, Sukhodolskoe, Vuoksa, Imandra lakes are located at its periphery, in Karelia and Kola Peninsula. Following parameters are distinguished: lakes bottom ¹³⁷Cs pollution density (kBq/m²), distribution of ¹³⁷Cs in the pro le of bottom sediments, ¹³⁷Cs di usion coe cients ( D ) in bottom sediments and content of the exchange chemical form of the radionuclide. ¹³⁷Cs contamination of the lakes was formed due to suspended matter sedimentation with ¹³⁷Cs, ¹³⁷Cs sorption and di usion in bottom sediments. With sedimentation ≥3 mm/year, the concentration of ¹³⁷Cs increased from the top to the bottom of the core (lakes Vuoksa, Ekostrovskaya Imandra), re ecting the gradual process of ¹³⁷Cs migration into the sediments. The opposite trend of ¹³⁷Cs concentration was observed in the bottom sediments of lakes Ladoga and Sukhodolskoe with sedimentation ≤0.5 mm/year. Here ¹³⁷Cs di usion with D = (0.5-6.2) ×10^-8 cm²/s caused slow radionuclide transfer in the bottom sediments. The main supply of ¹³⁷Cs was contained in the top layer 0-5 cm. 14.4-20 % of absorbed ¹³⁷Cs in lake Sukhodolskoye bottom sediments were was in an exchange chemical form, extracted into solution 1 М NH 4 Aс.

The radioecological situation at the site of the peaceful underground nuclear explosion «Crystal» after removal land cover and installation of the arti cial cover of rock from nearby quarry above the epicenter is considered. In 2012 the ambient dose equivalent rate of gamma radiation varied from 0.04 to 0.066 μSv/h, in 2019 the content of radionuclides in soils was (Bq/kg): ⁹⁰Sr 2.5-5.3, ^239,240Pu 0.03-25.4, ¹³⁷Cs <2.0. In 2018-2020 the activity of radionuclides in surface water was (Bq/dm³): in runo from under the arti cial cover ³H 4-12, ⁹⁰Sr 0.004-0.4, ^239,240Pu <10^-6, in local river water ³H 4-10.2, ⁹⁰Sr 0.004-0.3. At present, the impact of surface runo from the «Crystal» site on the river network is assessed as insigni cant. No more than 1/3 of ³H in the local river water comes with precipitation, and the rest of ³H comes from the «Crystal» explosion zone, mainly by an underground route. At least 91-96% of ⁹⁰Sr in the local river water is due to the «Crystal» explosion: part of it comes from the explosion zone by an underground route, part is washed o from the surface of landscapes.