What is the key operational difference between a pressurized water reactor and a boiling water reactor?

The distinction between a pressurized water reactor (PWR) and a boiling water reactor (BWR) lies primarily in how they handle the cooling water and steam generation. In a pressurized water reactor, the primary loop is kept under high pressure to prevent the water from boiling, which allows it to transfer heat from the reactor core to a steam generator. In this process, the primary coolant does not boil; instead, it transfers heat to a secondary water loop, which then turns into steam to drive the turbines.

This operational setup is critical because it allows the primary system to remain separate from the secondary system, ensuring that the radioactive materials within the primary loop do not mix with the steam that powers the turbine. This separation can enhance safety and containment features, which is a significant operational characteristic of PWRs.

In contrast, boiling water reactors allow the water in the reactor core to boil directly, generating steam in the same loop that directly feeds the turbines. This streamlined process eliminates the need for steam generators, but it also means that the secondary system and radioactive materials are not as distinctly separated as in PWRs.

Thus, the correct answer emphasizes how PWRs maintain separation between primary and secondary water through the use of steam generators, which is indeed