The boiling water reactor is also often abbreviated as BWR. It is typically used for methanol synthesis, but it can also be used for other exothermic reactions, such as methanation or water-gas shift.

A boiling water reactor contains a tube bundle which typically consists of several thousands of tubes. The catalyst is loaded in the tubes which are cooled from the shell side by boiling water – hence the name “boiling water reactor”. The temperature of the boiling water is controlled by adjusting the pressure.