DISTRIBUTION OF IMPURITIES IN STEAM-GENERATING EQUIPMENT IN NUCLEAR POWER AND HEAT-AND-ELECTRICITY PLANTS

A theoretical substantiation and the results of experimental studies of the behavior of impurities in the volume of the boiling medium in equipment in nuclear power and heat-and-electricity plants are presented. It is hypothesized that coarsely dispersed sludge accumulates at the boundary of the turbulent nucleus and viscous sublayer and only a small part of it settles on the heat-transmitting surface. If this hypothesis is correct, then sludge should accumulate and be expelled into the main volume of the working medium when the heat load changes, just like soluble impurities. The experimental data confirm this hypothesis. The quantity of impurities entering modern steam-generating facilities in nuclear power and heat-and-electricity plants is now always greater than the quantity leaving with steam, moisture, and purge water. Therefore, impurities either settle on a heat-transmitting surface or accumulate in the steam-generating volume. To understand the distribution of the different impurities, we present the following classification: macrodistribution ‐ the distribution of impurities over the volume of the working medium; for drum boilers in heatand-electricity plants it is the distribution over the length of the drums; microdistribution ‐ the variation of the impurity content in the boiling layer at the wall. The impurities brought into the steam-generating equipment could be easily soluble in water and insoluble in steam, easily soluble in water and steam, and insoluble in both water and steam. The macrodistribution of water-soluble and steam-insoluble impurities have been studied in greatest detail. A typical example is the behavior of sodium salts (phosphate water softening of boiler water in drum boilers). It follows from the elementary equations of the material and salt balances that the concentration of such an impurity is determined by the relation