Achieving More Efficient Removal of α-Emitting Radionuclides from the Primary Coolant in Propulsion Reactors

Abstract

The processes through which the α-emitting radionuclides contained in the primary circuit of a propulsion reactor are transferred in the circuit and removed from it in the standard ion-exchange filters are studied. The correlation between the behavior of transuranium elements and iron-containing corrosion product compounds in the primary circuit is considered. During reactor operation at steady power levels, α-emitting radionuclides reside, like iron compounds, predominantly in deposits on the circuit equipment surfaces. When hydrodynamic disturbances occur, these deposits transfer into coolant in the form of insoluble particles, thus intensifying the transfer of α-emitting radionuclides over the circuit. It has experimentally been found that the average deposition time of particles containing α-emitting radionuclides is larger than that of iron-containing particles (their deposition constants are equal to 0.6 h–1 and 0.9 h–1, respectively). This fact gives grounds to suppose that α-emitting radionuclides are nonuniformly distributed in corrosion product deposits and transfer into the coolant predominantly in the composition of particles having a smaller mean radius than that of iron-containing particles. As a result, the reactor’s standard ion-exchange filters show a relatively poor purification efficiency of α-emitting radionuclides (the purification constant is approximately 0.1 h–1 vs. 0.2 h–1 for corrosion product particles as a whole). The metering of hydrazine into the coolant results in that the repeated deposition rate of particles containing α-emitting radionuclides decreases by a factor of seven, due to which up to half of α-emitting radionuclides transferred into the coolant under the effect of hydrodynamic disturbance can be removed from it in the filters.