Question: If we do somehow manage to secure Iran’s enriched uranium supply, how exactly will we “destroy” something like that? — BBN, Tel Aviv, Israel
Answer: It’s not so much a matter of “destroying” it, it’s more a matter of rendering it useless for the production of a nuclear weapon. And that can be done in a few ways …
First, you need to recognize that uranium is an element, and as such cannot be “destroyed” by typical chemical processes like incineration or explosion. It can combine with many other elements to form molecules, but the uranium will still be there. To “destroy” the uranium you could simply allow it to fission. Uranium will randomly fission on its own, as it’s an unstable nucleus, but does so with a half-life of 700 million years. The usual decay process involves the emission of an alpha particle (helium nucleus) which converts U-235 to Thorium-231 — still radioactive but not bomb grade material. Unfortunately, that’s a really slow process.
You can speed that process up by injecting neutrons, as shown in the graphic, but that unfortunately leads to a nuclear explosion. Not a good way to “destroy” uranium.
When uranium fissions the large atom splits into two strongly repelling fragments, each typically around half the size of U-235. The most common resulting elements group into two main mass peaks: mass ~95 (mostly Rubidium, Yttrium, Zirconium, Niobium) and mass ~135 (mostly Xenon, Cesium, Barium). It’s the strong repulsion of these fragments the generates the kinetic energy (aka “heat”) of nuclear weapons and nuclear power plants.
So if you want to “destroy” weapons grade uranium, the preferred method is de-enrichment, sometimes called downblending. Highly enriched uranium (HEU) can be used for weapons if it contains 90% or more U-235. To downblend this material it is mixed with depleted uranium (about 0.2%–0.3% U-235) or natural uranium (0.7% U-235). The end product is low enriched uranium (LEU) containing 3%–5% U-235, which is the standard concentration for commercial nuclear power plants.
This process irreversibly changes weapons-grade uranium into civilian reactor fuel. It was used extensively in the historic U.S.–Russian Megatons to Megawatts program, which converted 500 metric tons of Russian weapons-grade uranium into commercial nuclear fuel between 1993–2013. In the United States, downblending operations are authorized and conducted at specialized facilities, such as the BWXT sites and the Department of Energy’s Savannah River Site.
Of course, you can’t just blend uranium like you would ingredients for a cake. HEU is in a metallic form, either as pure uranium or uranium oxide. You have to use a chemical reaction with fluorine to convert it to uranium hexafluoride (UF6). This compound will sublimate into a gaseous state when heated to 56.5°C, which can then be easily blended with other lower-enriched uranium also in gaseous form. This is what UF6 looks like sealed in a glass ampule:
If you’re wondering how uranium gets enriched in the first place, see my July 7, 2025 post How Uranium is Enriched. Might help with understanding how we de-enrich it.
So after the downblending, the uranium needs to be turned back into a pure metal (if purposed for a weapon) or into uranium dioxide (if purposed for reactor fuel). This requires a reduction reaction involving highly reactive metals like magnesium or calcium. When heated under strictly controlled conditions, the reducing agent can react with the fluorine leaving behind elemental uranium or uranium dioxide.
For reactor fuel, the uranium dioxide (UO2) is sintered into pellets that stack inside the reactor fuel rods. This is what they look like:
That matte black color is typical for UO2. But in the form of pure uranium, it has a silvery-white color like many other metals. These samples were produced by the Manhattan Project circa 1945:
So if we ever do get control of Iran’s HEU, there are peaceful ways to “destroy” it. We know how to do that. The trick will be getting possession of their HEU, and verifying we have all of it.
Next Week in Sky Lights ⇒ The DC Reflecting Pool and New Pond Syndrome