Boiling Water Reactor Power Plants

As the name implies, the water that removes the heat from the reactor core of the boiling water type of LWR is allowed to boil and generate steam directly within the core.34 The steam thus generated (at about 288°C and 10MPa) is used directly to drive the turbine. Steam is delivered to the turbine via a steam separator and a drier that removes the liquid from the water-steam mixture leaving the reactor. Volatile fission products that escape from any defective fuel rods are carried with the steam to the steam turbine. Devices such as catalytic recombiners are incorporated in a BWR system to prevent dangerous buildup of hydrogen and oxygen produced by the radiolysis of water in the core.

Two containment systems are used to prevent release of radioactivity in the event of an accident in a BWR plant. The primary containment is a steel pressure vessel that surrounds the cylindrical reactor vessel and is itself surrounded by reinforced concrete. The building that houses the reactor and the primary containment vessel is constructed of reinforced concrete and constitutes a secondary containment layer. Any radioactive material that escapes from the primary containment vessel is confined within the secondary containment space.

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