Late last week, Israel targeted three of Iran’s key nuclear facilities – Natanz, Isfahan and Fordow – killing several Iranian nuclear scientists.
The facilities are heavily fortified and largely underground, and there are conflicting reports of how much damage has been done.
Natanz and Fordow are Iran’s uranium enrichment sites, and Isfahan provides the raw materials, so any damage to these sites would limit Iran’s ability to produce nuclear weapons.
But what exactly is uranium enrichment and why does it raise concerns?
To understand what it means to “enrich” uranium, you need to know a little about uranium isotopes and about splitting the atom in a nuclear fission reaction.
All matter is made of atoms, which in turn are made up of protons, neutrons and electrons. The number of protons is what gives atoms their chemical properties, setting apart the various chemical elements.
Atoms have equal numbers of protons and electrons. Uranium has 92 protons, for example, while carbon has six. However, the same element can have different numbers of neutrons, forming versions of the element called isotopes.
This hardly matters for chemical reactions, but their nuclear reactions can be wildly different.
When we dig uranium out of the ground, 99.27 per cent of it is uranium-238, which has 92 protons and 146 neutrons. Only 0.72 per cent of it is uranium-235 with 92 protons and 143 neutrons (the remaining 0.01 per cent are other isotopes).
For nuclear power reactors or weapons, we need to change the isotope proportions. That’s because of the two main uranium isotopes, onlyuranium-235 can support a fission chain reaction: one neutron causes an atom to fission, which produces energy and some more neutrons, causing more fission, and so on.
This chain reaction releases a tremendous amount of energy. In a nuclear weapon, the goal is to have this chain reaction occur in a fraction of a second, producing a nuclear explosion.
In a civilian nuclear power plant, the chain reaction is controlled. Nuclear power plants currently produce 9 per cent of the world’s power. Another vital civilian use of nuclear reactions is for producing isotopes used in nuclear medicine for the diagnosis and treatment of various diseases.
To “enrich” uranium means taking the naturally found element and increasing the proportion of uranium-235 while removing uranium-238.
There are a few ways to do this (including new inventions from Australia), but commercially, enrichment is currently done with a centrifuge. This is also the case in Iran’s facilities.
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