Editing Pressurized water reactor (section)

=== Pressurizer ===
{{Main|Pressurizer_(nuclear_power)|l1=Pressurizer}}

Pressure in the primary circuit is maintained by a pressurizer, a separate vessel that is connected to the primary circuit and partially filled with water which is heated to the saturation temperature (boiling point) for the desired pressure by submerged electrical heaters. To achieve a pressure of {{convert|155|bar|MPa}}, the pressurizer temperature is maintained at 345&nbsp;°C (653&nbsp;°F), which gives a subcooling margin (the difference between the pressurizer temperature and the highest temperature in the reactor core) of 30&nbsp;°C (54&nbsp;°F). As 345&nbsp;°C is the boiling point of water at 155 bar, the liquid water is at the edge of a phase change. Thermal transients in the reactor coolant system result in large swings in pressurizer liquid/steam volume, and total pressurizer volume is designed around absorbing these transients without uncovering the heaters or emptying the pressurizer. Pressure transients in the primary coolant system manifest as temperature transients in the pressurizer and are controlled through the use of automatic heaters and water spray, which raise and lower pressurizer temperature, respectively.<ref>{{harvnb|Glasstone|Sesonske|1994|p=767}}</ref>