Radiochemistry最新文献

The paper describes a continuous numerical model of polluted groundwater plumes near the LRW storage reservoirs Lake Karachay and Staroye Boloto of Mayak Production Association. This model, developed by Gidrospetsgeologiya, is based on the long-term monitoring of data obtained by Facility-Focused Monitoring System (FFMS). The model is regularly updated as the FFMS database is augmented, new data of engineering-geological and hydrogeological surveys are obtained, and new tasks are set to assess the hydrogeological safety of nuclear facilities at the industrial site of Mayak Production Association.

Cement mortars and compounds prepared in the course of the development of a process for solidification of the solution fraction of alkaline high-level waste (HLW) accumulated at the Mayak Production Association were studied. Only materials commercially available in Russia were included in dry mix formulations. The spread, bleeding, final setting, and heat release were determined for model inactive cement mortars, and the compression strength, frost resistance, and water resistance, for the compounds. The ¹³⁷Cs leach rate was determined for the cement compounds with real solidified high-level solutions. The formulation meeting the whole set of regulatory and technological requirements to cemented radioactive waste, provided that the compound is placed in limited-volume containers (e.g., in NZK-type containers), was developed.

The study is aimed at reconstruction of the parameters of the source from which the Techa River was contaminated in the period 1949–1956 and deals with the migration of γ-emitting nuclides (GENs), namely, of ⁹⁵Zr and ⁹⁵Nb, in the river system. The archive (1951) results of measuring the specific activity of the sum of β-emitting nuclides (BENs), A_Σ (μCi/kg), in the soil and plants in the Techa riverside regions that are not flooded by floodwaters are analyzed. Analysis shows that the radioactive contamination of riverside territories is not associated with atmospheric discharges from the enterprise stacks and that the measurement results do not correspond to the commonly accepted views on the contamination distribution. In particular, contamination of the riverside soil and plants varied nonmonotonically with increasing distance from the river bank and along the river (spotty contamination pattern was observed), whereas the absolute values of BEN specific activities were constant throughout the territory within an order of magnitude. Furthermore, the depth distribution of BEN specific activities in soil up to 0.5 m was virtually uniform, and in some cases the activity increased with the depth. Finally, the plants had both external (on leaves) and internal (in roots) contamination, and in some cases the BEN specific activity in stems and leaves was lower than in roots. Presumably, the radioactive contamination of the soil and plants was determined by ⁹⁵Nb and was due to entrainment of an aqueous aerosol from the river water surface with the wind. The model calculations explain all the unusual distribution patterns observed and allow estimation of the upper boundary of the mean (for summer 1951) ⁹⁵Nb activity concentration in the river water.

The causes of the abnormally high mobility of ⁹⁵Nb in Techa River water are discussed from the viewpoint of general niobium chemistry, specific features of its chemistry on the tracer concentration level, and mode of its supply into the system.

The results of cesium recovery from seawater with commercially available Termoxid sorbents (Termoxid 35, Termoxid 3A) under laboratory and expeditionary conditions are presented. The dynamic exchange capacity and the total dynamic exchange capacity of the sorbents for cesium were determined. The breakthrough curves of cesium sorption were plotted for different seawater flow rates, and the physicochemical relationships (isotherm and kinetics) of sorption were studied. The efficiency of ¹³⁷Cs recovery from large volumes of seawater by Termoxid sorbents under expeditionary conditions was evaluated.

Agents for uranium stripping from a 30% solution of TBP in decane, loaded with 110–116 g/L uranium, were studied. The uranyl nitrate solubility in ammonium acetate and formate solutions was studied. The uranium distribution ratio as a function of the concentrations of ammonium acetate and formate was determined. Comparative trials of the suggested stripping agents were performed. Ammonium acetate and formate were shown to be suitable for uranium stripping.

The possibility of decontaminating radioactively contaminated metal surfaces using laser treatment was examined. The results obtained show that the use of laser treatment allows the metal waste to be transferred from the low-level waste (LLW) category to the very low-level waste (VLLW) category. It is appropriate to use the local gas treatment system for preventing the contamination of the working zone and equipment with radioactive aerosols.

TThe paper justifies great practical relevance of the problem of corrosion and erosion resistance of the refractories used as a structural element in direct electric heating furnaces intended for high-level waste vitrification. The list of the main promising materials is provided, as well as the algorithm of assessing their resistance to borosilicate melts during operation of electric furnaces. Corrosion tests of the refractory materials were carried out under static and dynamic conditions in low-melting borosilicate glass and in the melt of borosilicate glass containing simulated liquid high-level waste (HLW). The refractories that are most resistant to the glass melt under conditions of HLW solidification were identified. The results obtained will be useful for selecting the lining material for removable and small-size melters.

In the 1950s, V-2 reservoir (Lake Kyzyl-Tash) was used for cooling industrial uranium–graphite reactors (IUGRs). When water passed through the IUGR core, activation radionuclides (ARs) were produced by nuclear reactions of reactor neutrons with nuclei of chemical elements present in water and were accumulated in water. The AR activity concentration in water from V-2 reservoir depends on the concentration of chemical elements in the reservoir. Data on the content of 16 elements in V-2 water in the period 1948–1956 were collected. These data were analyzed taking into account the characteristic natural abundance of elements in water of the Irtyash–Kasli lake system and the additional technogenic pollution of the reservoir in the course of its operation. The main source of AR transfer from V-2 reservoir to the Techa River was controlled water discharge through open shutters of the P-2 dam (or uncontrolled water seepage through closed shutters). A mathematical model was suggested, and the activity concentrations in V-2 water were calculated for 16 elements and 31 nuclear reactions yielding 20 ARs. The model was verified using the archive data on the activity concentrations of ³²Р in V-2 water in 1953–1956. All the calculation results well agree with the available experimental data. The source term for AR transfer from V-2 reservoir to the Techa River in relation to the water flow rate through P-2 dam was determined. The experimental data on the scale of the distribution of the ³²Р activity concentration along the Techa River were analyzed. The results obtained allow taking into account the AR contribution to the total radioactive pollution of the river and evaluating the possible radiation impact on the population and biota.