Who makes nuclear fuel assemblies

The physical product is unremarkable to look at: ceramic uranium dioxide pellets, each about the size of a pencil eraser, stacked inside sealed zirconium alloy tubes, bundled into assemblies several metres long. One pellet holds roughly the energy of a tonne of coal.

What makes this stage strategically interesting is that fabrication is where the fuel chain stops being fungible. Every dimension of an assembly, rod diameter, lattice pitch, grid spacer design, the burnable poisons blended into the pellets, is specific to a reactor design, and changing supplier means requalifying the fuel with the regulator, which takes years.

That lock-in had direct geopolitical consequences. Reactors of Soviet design were built with the assumption that TVEL would supply their fuel forever, and for decades it did. Westinghouse spent years developing VVER-compatible assemblies at Västerås and Columbia, and those qualifications are what allowed Ukraine, the Czech Republic, Bulgaria, Slovakia and Finland to move off Russian fuel after 2022. The reactors did not change; the supply chain did, slowly and at considerable expense.

Fabrication is also where the fuel chain divides by reactor type. A CANDU operator needs no enrichment at all, so its chain runs mine to mill to conversion to fabrication and stops. An AGR operator in the UK depends on a single line at Springfields that exists to serve one fleet and must outlive it.