How does a BWR differ from a PWR in terms of coolant and steam generation?

How does a BWR differ from a PWR in terms of coolant and steam generation?

• A. In a BWR, water acts as both coolant and moderator and boils in the core, producing steam directly to drive the turbine, whereas a PWR uses a separate steam generator and a primary coolant loop.
• B. In a BWR, the coolant is gas; in a PWR, liquid water.
• C. In a BWR, there is a separate steam generator; in a PWR, coolant boils in core.
• D. In a BWR, heavy water is used; in a PWR, light water.

Answer: (A)

The essential difference is where and how steam is produced. In a boiling-water reactor, water serves as both coolant and moderator and is allowed to boil inside the reactor core. The steam that forms in the core is sent directly to the turbine, so the turbine is driven by steam that comes straight from the reactor vessel. In a pressurized-water reactor, the reactor coolant remains liquid and is kept at high pressure in a primary loop. Heat is transferred across a boundary in a steam generator to a separate secondary loop, where steam is produced to drive the turbine. This means the primary loop stays contained and hot, while the turbine is powered by steam from a separate circuit.

The essential difference is where and how steam is produced. In a boiling-water reactor, water serves as both coolant and moderator and is allowed to boil inside the reactor core. The steam that forms in the core is sent directly to the turbine, so the turbine is driven by steam that comes straight from the reactor vessel. In a pressurized-water reactor, the reactor coolant remains liquid and is kept at high pressure in a primary loop. Heat is transferred across a boundary in a steam generator to a separate secondary loop, where steam is produced to drive the turbine. This means the primary loop stays contained and hot, while the turbine is powered by steam from a separate circuit.