Iran breaches Uranium enrichment limits and what it really means:
- US President Donald Trump announced that he will add to existing sanctions on Iran, after the Tehran admitted that it surpassed uranium enrichment levels that were set by the Iran Nuclear Agreement in 2015.
- According to the deal, Iran could not enrich uranium above 3.67 percent.
- The 3.67 percent level is enough for nuclear power reactors, but far short of the 90 percent needed for weapons.
What does it means:
- Iran claims it has enriched uranium to 4.5%, breaking the limit of 3.67% set during the 2015 nuclear deal.
- The move was a response to the U.S. violating the terms of the deal under President Donald Trump's administration. To a certain extent, this is a question with a simple, chemical answer.
- Uranium comes in a few different forms (or "isotopes").
- All of them have the same number of protons (92) but a different number of neutrons. By far, the most common such isotope in nature is uranium-238, which has 146 neutrons.
- On Earth, this isotope makes up 99.3% of any sample of naturally occurring uranium. But for nuclear reactors (or weapons), that flavor isn't very useful.
- Dense clusters of uranium-238 don't tend to start nuclear chain reactions. The second most common isotope, however, uranium-235 (making up just about 0.7% of any sample of natural uranium and containing 143 neutrons), does tend to start nuclear chain reactions.
- In these reactions, the nuclei of the uranium atoms split into smaller nuclei and release neutrons. Those neutrons then cause other nuclei to split, releasing more neutrons for a self-sustaining "chain" reaction that emits enormous amounts of energy.
- Enriching uranium is the process of sorting uranium-238 atoms out of a uranium sample such that the sample includes a higher proportion of uranium-235. Uranium enriched to 3.67% is 3.67% uranium-235. Uranium enriched to 4.5% is 4.5% uranium-235. And so on.
Does Iran enrich enough uranium to make bombs?
- 4.5% is enriched enough for Iran to power its peaceful, already-active Bushehr nuclear reactor.
- But that level falls far short of the standard 90% threshold for "weapons-grade" uranium.
- And enriching uranium to 90% is an enormous technical challenge. It requires building and operating very advanced centrifuges.
- Centrifuges are common enough pieces of laboratory equipment. They spin samples of material around so as to generate centrifugal force. Under that intense force, heavier and lighter materials tend to separate.
- However, a common laboratory centrifuge is nowhere near powerful enough to separate uranium-235 from uranium-238.
- The two isotopes are nearly, but not quite, identical in mass. And a sample of uranium contains very little uranium-235.
- To extract the 137 lbs. (62 kilograms) of uranium-235 necessary to build the bomb dubbed "Little Boy" that was dropped on Hiroshima, Japan, the United States in 1945 expended a full 10% of its national energy supply, according to "The Making of the Atomic Bomb" (Simon & Schuster, 1995).
- The original uranium sample weighed 4 tons (3,600 kilograms). And 20,000 people helped build the refining facility that made the bomb, a facility that required 12,000 people to operate.
- It's not infeasible that Iran could enrich a significant stockpile of weapons-grade uranium.
- But the 4.5% mark doesn't represent a significant step in that direction, except in symbolic terms.
- Iran has also threatened to enrich uranium to 20%, which is closer but still not weapons grade.