CANDU (CANada Deuterium Uranium) is a type of nuclear power plant that uses natural uranium as fuel and heavy water (deuterium oxide) as a coolant and neutron moderator. CANDU reactors are designed to be highly flexible and can use a variety of fuel types, including recycled fuel from other reactors. They are also designed to be able to operate at a variety of power levels and can be used for both electricity generation and research purposes.CANDU reactors were developed in Canada and are used in several countries around the world, including Argentina, China, India, Pakistan, Romania, and South Korea. They are known for their high efficiency and safety record and have been used in a variety of applications, including electricity generation, desalination, and medical isotope production.