How does a Boiling Water Reactor (BWR) generate steam?

• A. The primary water is boiled directly in the reactor vessel to create steam sent to the turbine.
• B. Heat is transferred from the primary loop to a separate steam generator.
• C. Water is boiled in a separate boiler outside the reactor.
• D. Steam comes from cooling towers only.

Answer: (A)

In a Boiling Water Reactor, steam is produced directly in the reactor vessel by boiling the primary coolant. The reactor core heats the water to its boiling point at the reactor pressure, so steam forms inside the vessel itself. That steam then goes straight to the turbine to drive it, and after passing through the turbine it is condensed and returned as feedwater to the reactor. There’s no separate heat exchanger outside the reactor for steam generation in this design. Cooling towers, meanwhile, are used only to remove heat from the condenser, not to generate the driving steam. So the defining point is that the boiling happens inside the reactor vessel, and the steam sent to the turbine comes directly from that boiling.