Operation:

The level of water inside a pressurizer is directly dependant upon the temperature, and therefore the density, of the water in the system to that the pressurizer is linked. An increase in system temperature causes the density of the water to decrease. That decreased density causes the water to expand, causing the level of water to rise in the vessel. An increased level of water in a pressurizer is referred to as an insurge. An insurge compresses the vapor space that in turn causes the system pressure to rise. This output in slightly superheated steam in contact along with the subcooled pressurizer liquid. A superheated steam transfers heat to the liquid and to the pressurizer walls. That re-establishes and manages the saturated condition.

A decrease within system temperature causes the density to increase that causes the system water volume to contract. A contraction (drop) in pressurizer water level and increase within vapor space is referred to as an outsurge. The increase within vapor space causes the pressure to drop, flashing the heated water volume and creating more steam. An increased amount of steam re-establishes the saturated state. Flashing continues until the decrease within water level ceases and saturated conditions are restored at a somewhat lower pressure.

In every case, the last conditions place the pressurizer level at a new value. The system pressure stays at around its previous value, with associative small pressure differences during the level change, given in which the level changes are not too extreme.

In original application, relying on saturation to handle all differences in pressure is not practical. In conditions whereas the system water is surging within the pressurizer faster than the pressurizer could accommodate for instance, additional control is acquire through activating the spray. This spray causes the steam to condense more rapidly, by controlling the magnitude of the pressure rise.

While a large outsurge occurs, the level could drop rapidly and the water cannot flash to steam fast enough. This output within a pressure drop. The installed heaters add energy to the water and cause it to flash to steam faster, through decrease the pressure drop. The heaters could also be left on to re-establish the actual saturation temperature and pressure. Within certain designs, pressurizer heaters are energized continuously to make up for heat losses to the environment.

The pressurizer's heater and spray capabilities are designed to compensate for the expected surge volume. A surge volume is the volume which accommodates the expansion and contraction of the system and is designed to be classical of normal pressurizer performance. Plant transients might result in larger than normal insurges and outsurges. While the surge volume is exceeded then the pressurizer might fail to maintain pressure inside normal operating pressures.

Pressurizer operation, involving spray and heater operation, is commonly automatically controlled. Monitoring is needs within the event the control characteristics fail, since the effect on the system could be disastrous without operator action.