Could Iran have been about to make a nuclear weapon? Uranium enrichment explained
When Israeli aircraft recently hit a uranium-enrichment complex in the country, Iran could have been far from “rupture”, the capacity to quickly transform uranium “yellowcake” into bombardic quality fuel, with its new high-speed centrifuges
The men work inside a uranium conversion installation just outside the city of Isfahan, Iran, on March 30, 2005. The installation of Isfahan made hexafluride gas, which was then enriched by feeding it in centrifuges in an installation in Natanz, Iran.
Friday, in the dark, the local time, the local time, the Israeli military planes struck one of the Iranian uranium complexes near the city of Natanz. The warheads aimed to do more than break the concrete; They were supposed to buy time, according to reports. For months, Iran seemed to get closer and closer to “breakout”, the moment when its increasingly enriched uranium stock could be converted into fuel for a nuclear bomb. (Iran denied having continued the development of nuclear weapons.)
But why has the strike occurred now? Consideration could involve the operation of enrichment complexes. Natural uranium is made up almost entirely of uranium 238, or U-238, a relatively “heavy” isotope (which means that it has more neutrons in its nucleus). About 0.7%is only uranium 235 (U-235), a lighter isotope capable of maintaining a nuclear chain reaction. This means that in natural uranium, only seven atoms in 1000 are the lighter U-235 and ready for cracks; “Enrichment” simply means increasing the percentage of U-235.
U-235 can be used in warheads because its nucleus can easily be divided. The International Atomic Energy Agency uses 25 kilograms of U-235 content as the reference amount deemed sufficient for a first generation implosion bomb. In such a weapon, the U-235 is surrounded by conventional explosives which, when exploded, compress isotope. A separate device releases a flow of neutron. (Neutrons are the neutral subatomic particle in the nucleus of an atom which adds to their mass.) Each time a neutron strikes an atom U-235, the fissions of atoms; It divides and spits, on average, two or three fresh neutrons – no longer an explosion of energy in the form of heat and gamma radiation. And the neutrons emitted in turn strike other U-235 nuclei, creating an autonomous chain reaction among the U-235 atoms which were wrapped together in a critical mass. The result is a nuclear explosion. On the other hand, the most common isotope, U-238, generally absorbs slow neutrons without division and cannot lead to such a devastating chain reaction.
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To enrich uranium to contain enough U-235, the “Yellowcake” uranium powder which comes out of a mine must go through a long conversion process to transform it from a solid into a gas hexafluoride. First of all, a series of chemical processes refine uranium and then, at high temperatures, each atom of uranium is linked to six fluorine atoms. The result, uranium hexafluoride is unusual: below 56 degrees Celsius (132.8 degrees fahrenheit) is a white and waxy solid, but just above this temperature, it sublime in a dense and invisible gas.
During enrichment, this uranium hexafluoride is loaded in a centrifuge: a metallic cylinder which turns to tens of thousands of revolutions per minute – deeper than the blades of a jail engine. While the heavier U-238 molecules derive towards the wall of the cylinder, the lighter U-235 molecules remain closer to the center and are siphoned. This new gas slightly U-235 Richer is then put in the next centrifuge. The process is repeated 10 to 20 times because more and more enriched, the gas is sent by a series of centrifuges.
Enrichment is a slow process, but the Iranian government has been working there for years and already has around 400 kilograms of uranium enriched at 60% U-235. This does not cost the 90% necessary for nuclear weapons. But while the IR-1 centrifuges of the first generation of Iran swirl around 63,000 revolutions per minute and do relatively modest work, its new IR-6 models, built from high-resistance carbon fiber, run more quickly and produce much more enriched uranium.
Iran has installed thousands of these units, especially at Fordow, an underground enrichment installation built under 80 to 90 meters of rock. According to a report published Monday by the Institute for Science and International Security, the new centrifugals could produce enough U -235 uranium at 90% for an warhead “in as little as two to three days” and enough for nine nuclear weapons in three weeks – or 19 at the end of the third month.
