Enriched uranium is an uranium with more than 0,7 % uranium 235.

- the energy released from enriched uranium is higher compared to natural uranium
- the amount of uranium needed for a reactor is lower
- research reactors work only with enriched uranium
- atomic bombs have highly enriched uranium or plutonium

Uranium is enriched in the isotope uranium-235, producing uranium-238 as waste.

Yes, CANDU (CANada Deuterium Uranium) reactors can use natural uranium as fuel without enrichment due to their unique design that uses heavy water as a moderator to assist with neutron capture and fission. However, some CANDU reactors can and do use slightly enriched uranium or recycled fuel to enhance performance.