What component maintains very high pressures in a Pressurized Water Reactor system?

In a Pressurized Water Reactor (PWR) system, the component that maintains very high pressures is the electrically heated pressurizer. This component plays a crucial role in the reactor's operation by ensuring that the primary coolant remains in a liquid state, even at high temperatures. The pressurizer helps to control the pressure in the system by adjusting the volume of water and steam, which also contributes to the safety and efficiency of the reactor.

As water is heated within the reactor core, it tends to turn into steam, which would normally reduce pressure. The pressurizer compensates for this by using electrical heating to maintain a specific temperature and pressure level, which is critical for safe and efficient operation. It can also accommodate variations in pressure by allowing for expansion and contraction of the coolant, ensuring that the system remains stable.

Other components listed, such as a safety relief valve, pressure regulator, or cooling tower, serve different functions within the overall nuclear system but do not specifically maintain the high pressures essential for the PWR operation like the electrically heated pressurizer does.