 What are boiling water and pressurized water reactors? The fuel rods in a nuclear reactor are suspended in a water bath contained in a large metal container somewhat like a gigantic pressure cooker. A typical reactor vessel might be 15 feet in diameter and 20 feet high and some are even larger. In boiling water reactors, or BWRs, the water is allowed to boil and the heat generated in the fuel rods is carried away in steam. In pressurized water reactors, or PWRs, the water is held at very high pressure on the order of 2,000 pounds per square inch. More than 60 times the pressure in the tires of a typical car. In that situation, the water cannot boil. The water in a PWR carries the heat away while remaining liquid and passes through a steam generator to generate the steam to turn the turbine. In short, special enriched uranium packed in fuel rods and started on a chain reaction turns water into steam to turn a turbine so you can have electricity to run your computers and keep the lights on.