CANDU reactor

CANDU reactor is a type of nuclear reactor designed in Canada, and stands for CANada Deuterium Uranium. It is a type of pressurized heavy water reactor (PHWR) that uses deuterium oxide (heavy water) as its moderator and coolant, and natural uranium as fuel.

Design and Operation

The CANDU reactor design is unique in that it has two separate water systems: the primary coolant loop and the moderator system. The primary coolant loop, which is under high pressure to prevent boiling, transports heat from the fuel to the steam generator. The moderator system, which is at a lower pressure, slows down neutrons to sustain the nuclear chain reaction.

The fuel used in CANDU reactors is natural uranium, which is not enriched like the uranium used in most other types of reactors. This is possible because of the use of heavy water, which is a more effective moderator than regular water.

Advantages

One of the main advantages of the CANDU reactor design is its fuel flexibility. In addition to natural uranium, CANDU reactors can also use enriched uranium, mixed-oxide fuel (MOX), and even thorium. This makes CANDU reactors well-suited for countries that do not have access to enrichment facilities.

Another advantage is the ability to refuel the reactor while it is operating. This is known as on-power refuelling, and it allows for continuous operation and a high capacity factor.

Disadvantages

The main disadvantage of the CANDU design is the high cost of heavy water, which makes up a significant portion of the initial capital cost of the reactor. Additionally, the use of natural uranium fuel results in a higher volume of spent fuel compared to reactors that use enriched uranium.

Safety

CANDU reactors have several safety features, including a negative void coefficient of reactivity and two independent shutdown systems. The negative void coefficient means that if the coolant water turns into steam (which is less dense), the reaction rate decreases, providing a natural safety mechanism.

CANDU Reactors Around the World

There are currently 29 CANDU reactors in operation around the world, in countries including Canada, China, India, Pakistan, Argentina, South Korea, and Romania.

See Also

• Nuclear power
• Nuclear reactor technology
• Pressurized heavy water reactor
• Nuclear fuel cycle