Boiling water nuclear reactor. Diagram of the workings of a boiling water reactor (BWR), a type of nuclear reactor. In a BWR, the core (yellow columns) is suspended in water (blue). The heat produced by the nuclear reactions boils the water into steam (red). This turns a turbine (green), which drives an electricity generator (grey). The steam then passes through a condenser, which uses water from a cooling pond (lower right), before being passed back into the reactor chamber. The water acts as both the reactor coolant and the moderator. Control rods (blue, between core columns) can be raised or lowered to control the reaction. This is a cheap and simple reactor.