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The specific feature of heavy liquid-metal coolants (HLMC) is the possibility to form solid-phase impurity particles, which requires a deep study of characteristics of the wall boundary layer enriched with impurity particles. This is necessary for a fundamental understanding of the processes occurring on contact surfaces and triboprocesses to validate the use of materials for developing fast reactors with these coolants. The paper deals with results of experimental studies of structures and characteristics of the wall boundary layer. The use of the thermal shock technique enabled us to experimentally determine the wall boundary structure typical of circuits with heavy liquid-metal coolants (lead or lead-bismuth alloy). It has been experimentally demonstrated that the wall boundary region is a multicomponent structure: 1 – steel; 2 – oxide coating; 3 – layer of loose deposits weakly adhering to oxide coating; 4 – gas phase (due to unwettability of oxide surface by coolant); 5 – impurity-rich diffusion layer of boundary turbulent layer; 6 – boundary turbulent layer; 7 – impurity particles in coolant flow close to wall boundary region, which do not adhere to layers 3 and 5. It is found that long-term HLMC circulation in channels leads to an increase in the surface roughness of constructional materials due to the deposition of solid-phase impurities, which should be taken into account in tribological studies. The experimental results have also shown that the microhardness of structures of the wall boundary layer is an order different from the microhardness of both steel and solidified lead ingot (HVsteel = 245, HVwall boundary layer = 60, HVlead = 6), which permits to assume that the wall boundary layer is a rheological fluid. Also the chemical analysis of deposits on construction material surfaces is presented. The chemical analysis included X-Ray method and elemental analysis.

The purpose of this paper is optimization of methods for calculating of flow parts of impeller pumps for high-temperature lead coolant, taking into account specific cavitation performance of the lead coolant [1]. The article presents the studies of cavitation performance of the high-temperature coolant. The studies were conducted in the lead coolant medium at 450–550 °C, flow rate up to 25–30 m/s and lead flow pressure from 0 to 5.0 kgf/cm2 (atm), at oxygen content in lead from 10−5–10−4 up to saturation, as well as in the presence of solid phase of lead oxides in the flow and in the experimental loop with such coolant. With a view to improving the representativeness of the research results, conditions of occurrence and characteristics of gaseous cavitation in the lead coolant flow were determined using three independent methods [2, 3]. The research showed that gas cavitation can take place in lead flows in the vane-type pumps and other components of circulation loops followed by apertures of lead flow discontinuity (bubbles, caverns, etc.), filled up with diluted gas with subsequent disappearance of these apertures of flow discontinuity. Traditional cavitation with formation and subsequent collapse of lead vapors in reactor loops with lead and lead-bismuth coolant is not possible. Cavitation performance of lead coolant is identified.

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