Tuesday, October 20, 2026

@convequity Oct 16

Convequity on X

Our least-favoured bet on next-generation nuclear: light-water SMRs. Smaller does not automatically mean cheaper. A 50–300 MW small modular reactor produces far less power than a 1 GW plant, but containment, site infrastructure and other costs may not shrink proportionately. Factory production and simpler safety systems can help, but those savings must outweigh the loss of scale. The result could be a higher cost per installed kilowatt, not a lower one. Advanced alternatives offer higher temperatures and more industrial uses. But we think many face a bigger obstacle than licensing: securing enough fuel. To understand the investment trade-offs, separate two questions: what cools the reactor, and what fuels it? Light water → Proven technology, established fuel supply. Uses ordinary water and fuel typically enriched below 5% uranium-235. Runs at around 300°C under pressure, producing electricity and lower-temperature heat. Its advantage is maturity; its limitation is that it cannot directly supply the hottest industrial processes. Shrinking it does not necessarily improve its economics. Sodium → Higher temperatures without high pressure. Transfers heat efficiently and operates near atmospheric pressure, reducing the need for heavy pressure-containing equipment. The catch: sodium burns in air and reacts violently with water, requiring strict separation and additional safeguards. Helium → High-temperature heat without a chemically reactive coolant. Can reach roughly 750°C or more, supporting more efficient electricity generation and industrial heat. Helium does not burn or react chemically, but the system operates under pressure and must stay leak-tight. Leading designs also require specialised TRISO fuel. Fluoride salts → High-temperature heat at low pressure, without sodium’s fire risk. The challenges are corrosion, suitable materials and preventing the salt from freezing. Some designs, such as Kairos Power’s, use salt to cool solid TRISO fuel. Others dissolve the fuel in the salt itself. These are different designs with different fuel requirements. Then come two separate fuel bottlenecks: HALEU is about uranium enrichment. It contains more than 5% but less than 20% uranium-235. Many leading sodium-, helium- and fluoride-salt-cooled designs need it, although not every advanced reactor does. Western production remains limited. Centrus Energy ($LEU) has produced small quantities with demonstration equipment and targets new enrichment capacity in 2029. We do not expect sufficient supply for broad deployment before the late 2020s at the earliest. TRISO is about fuel manufacturing — not a type of coolant. Tiny uranium-bearing particles are wrapped in carbon and ceramic layers designed to retain radioactive fission products even at roughly 1,600°C. That is a major safety advantage, but manufacturing and quality control are demanding. US production already exists, but capacity needs to expand substantially. X-energy’s ( $XE) larger TX-1 facility is still under construction. Helium-cooled and some salt-cooled designs therefore face both bottlenecks: getting HALEU, then turning it into finished TRISO fuel. For investors, a reactor licence is not a fuel supply chain. And a smaller reactor is not automatically a better investment.