Effect of complexing agents (DTPA and oxalic acid) on the extraction behavior of technetium in the TBP-N2H5NO3-HNO3 system

The effect of complexing agents DTPA and H₂C₂O₄ on the extraction-chemical behavior of Tc, as applied to extractive splitting of U and Pu in the Purex process, was studied. The kinetic relationships of catalytic decomposition of N₂H₅NO₃ under the action of Tc in the presence of these agents were determined. Variation of the ratio of the oxidized and reduced Tc species in the course of this process at various HNO₃ concentrations was examined. In the final step of the reaction of N₂H₅NO₃ with Tc in a nitric acid solution, when the reductant content is stabilized, the oxidation of reduced Tc also stops or continues at a considerably lower rate than before stabilization. The presence of DTPA decreases the rate of Tc(IV) oxidation owing to its binding in a complex and decreases the fraction of Tc(VII) in the system by the end of the reaction, with no decrease in the rate of N₂H₅NO₃ decomposition noted under these conditions. The presence of H₂C₂O₄ in solutions decelerates the Tc reduction and the N₂H₅NO₃ decomposition; the oxidation of the reduced Tc either is insignificant or is not observed at all, depending on the conditions and H₂C₂O₄ content.     

Development and Pilot Testing of New Flow Diagrams for Plutonium Purification at the RT-1 Plant

Theoretical Foundations of Chemical Engineering - To modernize the extraction facility of the RT-1 plant, two flow diagrams for plutonium purification have been developed. In the first flow...     

Features of Pu(IV) and Np(IV) Extraction from Nitric Acid Solutions of Uranyl Nitrate with 30% TBP

The extraction of Pu(IV) and Np(IV) from nitric acid solutions containing high concentrations of uranyl nitrate with 30% TBP in hydrocarbon diluent was studied. It was found that, as the Pu(IV) and Np(IV) concentration grows from tens milligrams to several grams at fixed uranyl nitrate (100 g l^-1 and higher) and nitric acid concentrations in the aqueous phase, the distribution coefficients of actinides(IV) increase (for Np to a greater extent than for Pu). This trend becomes more pronounced at higher temperatures. Correlation equations describing this effect are suggested.     

Mathematical Treatment of the Distribution of HN3 in the Liquid-Gas System during Exraction Separation of Uranium and Plutonium

The rates of HN₃ desorption from aqueous and organic solutions (20% TBP in a hydrocarbon diluent) as dependent on the phase stirring intensity and temperature were subjected to mathematical processing. The equation derived for the desorption constant is similar to the mathematical expression of the Arrhenius law. The activation energy of HN₃ desorption from solutions was estimated at 36±3 and 50±10 kJ mol^-1 for aqueous and organic solutions, respectively. The HN₃ desorption rate constant (under experimental conditions) for organic solvents is 6plusmn2 times lower than for aqueous solutions. The empirical values of the pre-exponential factors in the formulas for determining the HN₃ desorption constants were estimated. The empirical expressions derived for the desorption constants provide a possibility of estimating the HN₃ carry-over during reductive stripping of plutonium. The formulas derived are suitable for other extraction processes involving hydrazine decomposition into HN₃.     

Adaptation of RT-1 Plant Technology to Processing of New Types of Spent Nuclear Fuel

Atomic Energy - The issues of including new materials into processing at a radiochemical plant are considered. Taking by way of an example the technology of an RT-1 plant, it is shown that it can...     

The influence of deviations in process parameters on the purification of uranium from different radionuclides

In the present study, the effect of deviations in the process has been determined during the process of the extraction processing of spent nuclear fuel (SNF) VVER-440 on RT-1 plant on the purification of uranium from ⁹⁹Tc, ¹²⁵Sb, ¹⁰⁶Ru, ¹³⁷Cs, ²²⁸Th, etc. The uranium decontamination factors during purification from these nuclides for both cycles of the Purex scheme of plant are calculated. It has been shown that, upon deviations in the process (the short-term shutdown of process, fluctuations of hydrodynamic mode, deposition of elements in the extractors, etc.), an increase in the uranium decontamination factors during purification from most unwanted nuclides is observed, except for technetium. However, it has been found that, at an increased inflow of Tc to the second extraction cycle, the purification of the final uranium product from this element may be insufficient.     

Some special features of the production of forgings and springs in VAZ

The forge shops in VAZ process up to 85,000 tons of bar structural steel yearly, including 18,000 tons of calibrated steel for springs. The average daily yield of forgings and springs is 180 tons. The large scale of the production requires advanced equipment and technological processes that provide high-grade forgings and springs at a minimum labor intensity and consumption of materials.