Boiling Water Reactor, BWR
Single-circuit nuclear power plant. The water, used as a moderator and a coolant, boils directly in the reactor vessel, and the resulting steam propels the turbine. The design of BWR is very similar to that of PWR. The reactor is a pressure steel vessel 10 metres high, with the reactor core 3.5 metres high and 4.5 metres in diameter. The 4-metre-long fuel rod contains uranium pellets enriched to 2.1—2.6%. The control rods are inserted from below. In the upper part of the reactor, steam has a lower moderating capacity than water, and the probability of fission is thus lower. The pressure of cooling water (7 MPa) is lower than in PWR, and its temperature is about 280 °C. The single-circuit scheme offers higher efficiency, but the turbine can be contaminated by radionuclides because of neutron capture from water. Biological shielding of the turbine during operation and maintenance is necessary.
The BWR is the second most common type of nuclear reactor. In 2022, 61 BWR reactors were in operation and 3 under construction.