What is CANDU?

CANDU stands for "CANada Deuterium Uranium". 

It's a Canadian-designed power reactor of PHWR type (Pressurized Heavy Water Reactor) that uses heavy water (deuterium oxide) for moderator and coolant, and natural uranium for fuel.

CANDU-features and advantages

• CANDU is the most efficient of all reactors in using uranium: it uses about 15% less uranium than a pressurized water reactor for each megawatt of electricity produced
• Use of natural uranium widens the source of supply and makes fuel fabrication easier. Most countries can manufacture the relatively inexpensive fuel
• There is no need for uranium enrichment facility
• Fuel reprocessing is not needed, so costs, facilities and waste disposal associated with reprocessing are avoided
• CANDU reactors can be fuelled with a number of other low-fissile content fuels, including spent fuel from light water reactors. This reduces dependency on uranium in the event of future supply shortages and price increase.
• Heavy water (deuterium oxide) is highly efficient because of its low neutron absorption and affords the highest neutron economy of all commercial reactor systems. As a result chain reaction in the reactor is possible with natural uranium fuel
• Heavy water used in CANDU reactors is readily available. It can be produced locally, using proven technology. Heavy water lasts beyond the life of the plant and can be re-used.
• Reactor core comprising small diameter fuel channels rather that one large pressure vessel
• Allows on-power refueling - extremely high capability factors are possible
• The moveable fuel bundles in the pressure tubes allow maximum burn-up of all the fuel in the reactor core
• Extends life expectancy of the reactor because major core components like fuel channels are accessible for repairs when needed.  

Courtesy: https://canteach.candu.org/