How do Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR) create steam?

Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR) both generate steam through the heat produced during the fission process of uranium fuel in the reactor core. In a BWR, water is allowed to boil directly in the reactor core, creating steam that drives the turbines for electricity generation. In a PWR, the reactor core heats water in a primary loop, which is then transferred to a secondary loop where it can produce steam without boiling in the reactor core itself.

This process relies on the immense heat generated from nuclear fission reactions, where the splitting of atomic nuclei releases energy. The essential role of this heat makes the correct choice pivotal in understanding how these reactors function.