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The forced recirculation head from the recirculation pumps is very useful in controlling power, however, and allows achieving higher power levels that would not otherwise be possible. The thermal power level is easily varied by simply increasing or decreasing the forced recirculation flow through the recirculation pumps.
These pumps are powered by wet-rotor motors with the housings connected to the bottom of the RPV and eliminating large diameter external recirculation pipes that are possible leakage paths. The 10 internal recirculation pumps are located at the bottom of the annulus downcomer region (i.e., between the core shroud and the inside surface of the RPV).
These are called the pump curves. They are determined by studies, whose methodology is standardized. These curves are specified when water is pumped with a density of 1000 kg/m3 and kinematic viscosity of 1 mm2/s. When the circulating pump is used for liquids of different density and viscosity, the pump curves have to be recalculated.
The pump must be beneath the steam drum to take advantage of the pressure due to the height of the water. If the pump was not there; when it reaches the steam separator and water returns to the pump, the pressure may become low enough in the eye of the impeller to cause cavitation and subsequent damage.
A flow that is not a function of time is called steady flow. Steady-state flow refers to the condition where the fluid properties at a point in the system do not change over time. Time dependent flow is known as unsteady (also called transient [8]). Whether a particular flow is steady or unsteady, can depend on the chosen frame of reference.
Babcock & Wilcox plants (e.g., Three Mile Island) have smaller steam generators that force water through the top of the OTSGs (once-through steam generators; counter-flow to the feedwater) and out the bottom to be recirculated by the reactor coolant pumps. The horizontal design has proven to be less susceptible to degradation than the vertical ...
Corrosion is caused by oxygen in the water. The oxygen causes the metal to oxidize which lowers the melting point of the metal. Foaming and priming are aused when the boiler water does not have the correct amount of chemicals and there are suspended solids in the water which carry over in the dry pipe.
However, there are other types of eddies that are not simple vortices. For example, a Rossby wave is an eddy [ 3 ] which is an undulation that is a deviation from mean flow, but does not have the local closed streamlines of a vortex.