Boiling water reactor
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Nuclear reactor with water as a coolant and as a moderator,
boiling in the core. The resulting steam is generally used directly
to drive a turbine. Example: Nuclear Power Plant Krümmel, 1 316
MWe (Germany). The fuel elements containing the uranium dioxide are
located in the pressure vessel, two thirds of which are filled with
water. The water flows through the core from bottom to top and removes
the heat developed in the fuel elements. Part of the water evaporates.
Following steam-water separation in the upper part of the pressure vessel,
the saturated steam at a temperature of about 290 °C and a pressure
of approx. 70 bar (7 MPa) is fed to the turbine. This amounts to up
to 4 500 t steam per hour. The turbine is coupled to a three-phase generator.
The steam exiting the turbine is liquefied in the condenser. For this
purpose about 120 000 m3 cooling water per hour is required
and is taken from a river, or in the case of closed-circuit cooling
operation, is derived from the cooling tower circuit. The feed water
is heated to a temperature of about 215°C by means of a heating
system and refed into the reactor. The control rods containing the neutron-absorbing
material are inserted in the core from below by means of an electromotor
(normal drive) or hydraulically (trip). The piping leads out of the
containment into the engine house. A number of safety devices are installed
to achieve immediate isolation of the reactor from the engine house
in case of a malfunction.
Diagram boiling water reactor

Principle of a nuclear power plant with
boiling water reactor
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