Ø            Boiling Water Reactor

In a boiling water reactor, enriched nuclear fuel undergoes nuclear fission in an enclosed pressure vessel.  Water is used both as a coolant for the nuclear fuel and as a moderator to maintain the nuclear fission process.  The water for cooling the nuclear fuel is allowed to boil in the reactor pressure vessel above the reactor core, to produce steam for the turbine-generator.  A certain portion, typically 25 to 40 percent, of each store of nuclear fuel will need to be replaced in between 12-24 months.