The fuel cycle at a glance

Uranium travels a long circuit before it fissions inside a core. It leaves the mine as ore with less than 1% uranium, gets concentrated at the mill to 80% or more, that concentrate (yellowcake) is converted into uranium hexafluoride so isotopes can be separated, and in most of the world's reactors that UF₆ is enriched from the natural 0.7% to 3–5% uranium-235. Once the uranium is at the right concentration, fabrication turns it into ceramic pellets inside metal cladding, and those fuel assemblies spend three to six years inside the reactor releasing heat. On the way out, spent fuel first goes to a pool and then, depending on the country, to a dry cask or to a reprocessing plant that recovers the uranium and plutonium still worth using.

Not every reactor needs the conversion and enrichment stages. Those moderated by heavy water, Canada's CANDUs and Atucha's German-designed PHWRs, absorb so few neutrons that the chain reaction can sustain itself on natural uranium, with no need to concentrate the uranium-235. Argentina takes that shortcut at Embalse and Atucha II; Atucha I is the exception, running on slightly enriched uranium at 0.85% since 2001 to roughly double fuel burnup. That shortcut completely changes the industrial chain a country needs: mining, conversion to uranium dioxide and fuel fabrication are enough, with almost no need for UF₆ plants or centrifuges of its own.

Argentina built that shorter chain. Uranium is mined and concentrated in the country, Dioxitek in Córdoba converts it into uranium dioxide, CONUAR and FAE in Ezeiza fabricate the fuel assemblies, and those assemblies go straight to Atucha II and Embalse without passing through any enrichment plant; Atucha I's fuel blends in a share of imported, slightly enriched uranium, up to 0.85% U-235. The country's only enrichment plant, in Pilcaniyeu, plays no part in that blend: its purpose is to supply research reactors and the CAREM, the first domestically designed PWR, which does need low-enriched uranium. The heavy water that makes that shortcut possible is itself a local product, made at the PIAP plant in Arroyito, Neuquén.

The seven entries in this group cover each stage with its numbers, its plants and its sources: mining and in-situ leach, UF₆ conversion, enrichment and SWU, fuel fabrication, HALEU and TRISO for advanced reactors, spent fuel and dry storage, and heavy water. Together they trace both the international cycle a PWR or BWR depends on and the shorter, heavy-water route that Argentina and a handful of other countries built instead.