CANDU burns natural unenriched uranium.

moderator, coolant

CANDU, a reactor type designed in Canada which uses heavy water as the primary coolant.

It is different for all reactor types, but I'll tell you about the CANDU, as it is widely used, and I know the most about it. Each CANDU reactor holds 4500-6500 fuel bundles at one time, each 50cm long and 10cm in diameter, each weighing about 20kg. Each produces roughly 1GWh (gigawatt hour) of power during its time in the reactor.

CANDU Reactors are specifically designed such that they do not require enriched uranium, and can operate entirely on naturally-occurring uranium. A CANDU design is generally used by parties that do not desire uranium enrichment facilities, due to the cost of those facilities.

That said, a CANDU reactor CAN use enriched uranium, they are fully capable of supporting that fuel type.