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On Friday the head of the International Atomic Energy Agency, Rafael Grossi, told the UN Security Council that "the above-ground part of the pilot fuel enrichment plant, where Iran was producing uranium enriched up to 60% U-235, has been destroyed".

What's left over after this process removes some of the U-235 is called depleted uranium.

U-235 has a half life of about 700 million years and represents about 0.72% of natural uranium.

Natural uranium is composed primarily of three isotopes: U-234, U-235 and U-238.

Depleted uranium is mainly U-238, with small amounts of other isotopes, including U-235.