Adequate design solution and maintenance of circuits with fast reactors cooled by lead and lead-bismuth coolants require taking into account the peculiarities of hydrodynamics of these coolant flows. The design pressure of saturated vapors of lead and its alloys at temperatures of 400–550 °C is 10 −18−10 −10 atm, which is significantly less than that of sodium or water. Processes of traditional cavitation cannot occur in a flow of heavy liquid-metal coolants because of their specific character. The main circulation pumps of reactor circuits are one of their basic elements. In fact, the flow-type parts of these pumps and other vane pumps operating in lead and its alloys cannot be calculated by traditional methods in terms of cavitation characteristics; appropriate calculation formulas are not currently available. To study cavitation processes in a heavy liquid-metal coolant flow, the authors have carried out the experiments aimed at:
- determining the conditions of disconnection of liquid lead and lead-bismuth eutectic column;
- determining the cavitation characteristics of a centrifugal pump transferring lead at a temperature of 500 °C;
- studying the characteristics of ejector (Venturi nozzle) in a liquid metal;
- studying the cavitation erosion effect of the lead coolant on impeller vanes of an axial-flow pump in a limited volume in the FT-4-A stand at a lead flow rate of up to 1200 t/h;
- studying the cavitation characteristics of an axial-flow pump in the FT-4 stand at shaft speeds of 13.34–25 Hz.
These studies are performed with the lead coolant at temperatures of 450°−550°C, oxygen in lead from 10−4−10−5 to 100, flow rates from 20 to 1800 t/h, which corresponds to velocities of the lead coolant flow from 1.0 to 26 m/s.
The experiments have shown that as distinct from water, traditional cavitation processes in a heavy liquid-metal coolant (HLMC) flow are not recorded. The probable cavitation mechanism is gas cavitation. The allowance for the specific character of hydrodynamics of HLMC flows is necessary for adequate design engineering and maintenance of some elements of the reactor circuit.