This paper investigates the supply chain for nuclear fuel with a particular focus on the market concentration around the production of natural uranium and the technical features of fuel for Russian made VVER reactors. This is meant to identify the two main bottlenecks that could potentially stand in the way of sanctioning Russian origin nuclear fuel. The key findings are that the market for natural uranium is much more concentrated than other energy commodities, and that western nuclear fuel producers already possess a significant amount of experience producing fuel rods for VVER reactors. This paper does not find any economic and technical reason for not imposing sanctions on the Russian nuclear supply chain.