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BBC News Science Team
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The IAEA has described the attacks on Iran’s nuclear facilities as “deeply concerning”.
On Monday, its Director General Rafael Grossi said that military escalation “increases the chance of a radiological release with serious consequences for people and the environment”.
Uranium enrichment sites are used to build up supplies of a particular type – or isotope – of uranium.
“When you dig uranium out of the ground, it comes in two forms: 99.3% is uranium-238 – and 0.7%, or about one atom in 150, is uranium-235, and this is what you need to work in your nuclear reactor,” explains Professor Paddy Regan from the University of Surrey and the UK National Physical Laboratory.
Burst of energy
The process of nuclear enrichment basically means increasing the amount of uranium-235.
This is done by taking uranium in its gas form and spinning it in machines called centrifuges, Prof Regan said.
And because uranium-238 is heavier than the required uranium-235, the two separate out as they spin. This is repeated again and again to boost the enrichment.
Nuclear power stations typically need about 3-5% of this enriched uranium to generate a controlled nuclear reaction that releases energy.
But when the aim is to make a nuclear weapon, a much higher proportion of uranium-235 is needed – about 90%.
Essentially, the more enriched the uranium, the bigger the burst of energy when all those atoms split.
