Mechanism and Kinetics of Rh(IV) Radiation-Chemical Reduction in HNO3 Solutions

Reduction of Rh(IV) in -irradiated and nonirradiated solutions of HNO₃ (0.3-3.0 M) was studied. In both systems, Rh(IV) is completely reduced to Rh(III). The reduction rates in nonirradiated solutions amount to 50-90% of rates in irradiated solutions. Reduction of Rh(IV) with water is postulated. The rates of Rh(IV) reduction in both irradiated and nonirradiated solutions increase with [Rh(IV)] growth and decrease with an increase in [HNO₃] from 0.5-1 to 2-3 M. The dependence of the reduction rates on the dose rate is weak. Mathematical simulation was used to reveal the mechanism and kinetics of radiation-chemical reduction of Rh(IV) in HNO₃ solutions. The rate constant of Rh(IV) reduction with water was calculated by fitting to the experimental data.     

Redox Reactions of Platinum Elements: XV. Kinetics of Rhodium(III) Oxidation with Xenon Difluoride in Nitric Acid Solutions

The rate of the reaction 2Rh(H₂O)₆ ^{3 +} + XeF₂ = 2Rh(OH)₃ ⁺ + Xe + 2HF + 4H⁺ + 6H₂O is described by the second-order equation -d[Rh(III)]/dt = k ₁[Rh(III)][XeF₂], where k ₁ = 15.4±0.8 l mol^-1 min^-1 at 17.8°C and the solution ionic strength = 2. The activation energy of the reaction is E ₁ = 60.6±1.0 kJ mol^-1. This reaction is complicated by the parallel hydrolysis reaction 2XeF₂ + 2H₂O = 2Xe + O₂ + 4HF. The reaction mechanism includes a slow stage of H atom transfer from Rh(H₂O)₆ ³⁺ to XeF₂ molecule with formation of XeF^. radical as an intermediate. The subsequent stages of Rh(H₂O)₅(OH)³⁺ hydrolysis and reduction of XeF^· radical to Xe proceed rapidly.     

Recycling of uranium from spent RBMK fuel in the nuclear fuel cycle

It is shown that there is promise in using the uranium product obtained by reprocessing spent nuclear fuel from RBMK reactors as a non-initial fuel source for thermal reactors. A technical path for spent nuclear fuel from RBMK reactors is proposed: radiochemical reprocessing and obtaining oxides of recycled uranium. Oxides of the category RBMK-poor are packed and then stored in a near-surface storage facility; oxides of the category RBMK-rich are fluoridated, and UF₆ is fed into separation production for additional enrichment to the required content of ²³⁵U. Additional advantages of recycled RBMK uranium as a source of non-initial ²³⁵U are the low content of ²³²U and the relatively low activity of spent fuel, which simplifies its reprocessing.     

Spent Nuclear Fuel Reprocessing and Nuclear Materials Recycling in Two-Component Nuclear Energy

Atomic Energy - The project Proryv [Breakthrough] now being implemented in our country is aimed at achieving a new quality of large-scale nuclear power, development, origination, and industrial...