Boiling Water Reactor (BWR) – Advantages and Disadvantages:

In this Boiling Water reactor, enriched Uranium is used as fuel. Enriched uranium contains more fissionable isotope U²³⁵. Water is used as coolant, moderator and reflector like in PWR except the steam is generated in the reactor itself instead of separate steam boiler.

Water enters the reactor at the bottom. It takes up the heat generated due to fission of fuel and gets converted into steam. Steam leaves the reactor at the top and flows into the turbine.

Advantages

1. The pressure inside the reactor vessel is much lower than PWR as water is allowed to boil inside the reactor. Hence, the reactor vessel is much lighter than PWR and reduces the cost of pressure vessel considerably.
2. Since the reactor does not require steam generator, pressurizer, circulating pump and piping’s, the cost is further reduced.
3. Boiling water reactor is more stable than PWR.
4. Thermal efficiency of BWR plant is more than PWR plant.

Disadvantages

1. The BWR has negative power demand coefficient. i.e., when more power is demanded from the reactor, it may produce less.
2. The steam leaving the reactor is slightly radioactive and hence the turbine and the pipings should be properly shielded.
3. Since the boiling of water on the surface of the fuel is allowed, the ‘burn out’ of fuel is more.