I’m new to the Energy Central community and glad to contribute with my first analysis here. This is a quantitative work I worked in at Raw Science on nuclear fuel cycles, critical materials and energy-system constraints.
When we talk about next-generation reactors, most of these small modular reactors and microreactors are designed to use HALEU, enriched uranium between 5% and almost 20% U-235. This higher enrichment allows for smaller cores, higher power density, and longer refueling intervals, but we should also consider that it not just the slightly more enriched fuel used in conventional reactors: for every ton of product, it requres a much higher demand on both the uranium conversion and enrichment infrastructure.
For instance, one ton of 19.75% HALEU produced from natural uranium at a 0.20% tails assay, the enrichment mass balance requires almost 39 tons of natural uranium feed (approx. 45 tons of U₃O₈) and around 45 tSWU of separative work. Compared with standard 4.5% light-water-reactor fuel at the same tails assay, this represents 5 to 6 times more natural uranium and almost 6 times more SWU per ton of enriched product.
Hence, the debate on nuclear fuel may not only focus on uranium mining but also take into account conversion and enrichment steps, and in the case of HALEU, these two last processes can become significant constraints. The critical variable that links them is the tails assays: i.e., the concentration of U-235 that remains in the depleted uranium stream after the enrichment step.
Lower tails allow the recovery of more U-235 from each unit of feed. and this reduces natural-uranium demand but requires, on the other hand, more separative work (SWU). Higher tails do the opposite: they save SWU but consume more uranium and conversion capacity. And this relationship can influence the market.
Expensive enrichment can mean higher uranium demand
When the SWU price increases in comparison to the uranium feedstock, the cost-optimal point shifts toward a higher U-235 content in the tails; this means that, in effect, the enrichment plant leaves more U-235 in the depleted stream, since extracting it requires an increasingly more expensive separation process. The direct consecuence is a higher demand for natural uranium even though the amunt of enriched fuel required by the reactors has not changed.
The mass balance model that I describe in detail in Raw Science illustrates this effect pretty well. If we keep the price of uranium constant and shift from a scenario based on legacy service costs to the current spot market scenario, the calculated initial cost of one ton of 19.75% HALEU increases by 40.4%. And this increase arises from fuel cycle services: conversion costs that skyrocket, and the contracted price of enrichment which doubles. By legacy service costs I mean the situation (or the relatively low price of conversion and enrichment) that prevailed before 2022, that is, before the Russian ban.
The difference between spot prices and long-term contracts prices is also an interesting point. In the case of the spot market analyzed, the price of uranium is $86.38/lb of U₃O₈, the price of conversion is $64.50/kgU, and the price of enrichment is $200/SWU. For contracted market, the corresponding princes are actually $95.50/lb for uranium, $55.50/kgU for conversion, and $173/SWU. And this, of course affect the final front-end price for the enrichment of uranium.
Despite the higher contracted uranium price, the contracted case produces a slightly lower calculated front-end cost: approximately $19 million per ton of 19.75% HALEU, compared with over $20 million under prompt-market prices. And this tells us where the bottlneck of enrichment may be: a prompt buyer is paying for access to scarce near-term conversion and enrichment capacity. A long-term buyer gives suppliers committed volumes, scheduled deliveries and predictable revenu: conditions that can support investment in additional capacity. If we see that with a broader view, than an advanced-reactor buildout requires more than reactor orders and additional uranium mines: it requires coordinated investment across conversion, enrichment, deconversion and fabrication. So that, the next nuclear supply squeeze may not first appear at the mine or at the reactor site. but inside the relatively small number of facilities capable of converting uranium and performing the separative work required to reach HALEU assays.