How Much Uranium Does a Reactor Use? First Cores, Reloads and Annual Demand
60-second answer: A 1,000 MWe light-water reactor at a 90% capacity factor uses about 22 tonnes of enriched uranium a year in reloads. Making that takes about 193 tonnes of natural uranium, roughly 0.50 million pounds of U₃O₈, per our worked example below. A new reactor's first core, about 75 tonnes of enriched uranium (per WNA), is a separate one-time purchase.
That answer has assumptions inside it. Capacity factor, thermal efficiency, burnup and the enrichment tails assay all move the number. The calculation below runs end to end so you can reproduce it, and the last section explains how to read shorthand like "170 tU per GWe-year" in our own demand model.
For context, the 81,697,348 lb of U₃O₈ that the Sprott Physical Uranium Trust held on November 5, 2026 (per Sprott) equals about 163 years of reloads for one such reactor.
Rule of thumb: first core vs annual reload
| 1,000 MWe light-water reactor | First core | Annual reload |
|---|---|---|
| Enriched uranium loaded | ~75 t (one time, before commercial operation; per WNA) | ~22 t at 90% capacity factor (our worked example); 24.3 t at 100% output (per WNA) |
The natural uranium behind a first core depends on its loading assays, which developers disclose per design. Do not derive it by multiplying reloads; the section on first cores explains why.
Start with the units
Three unit systems show up in every fuel conversation, and mixed-up units produce most of the wrong answers.
- MWe vs MWth: a light-water reactor's electrical output (MWe) is roughly a third of its thermal output (MWth). Fuel burns against thermal energy; revenue is electrical. Never apply a per-GWe coefficient to a thermal rating.
- Enriched vs natural uranium: the fuel loaded into the core is enriched product. Making one tonne of it consumes several tonnes of natural uranium feed, with the ratio set by the assays. Never add the two together.
- tU vs lb U₃O₈: mined uranium trades in pounds of U₃O₈. One tonne of contained uranium is about 2,600 lb of U₃O₈. Our units converter handles the arithmetic.
The worked calculation, end to end
Take a 1,000 MWe reactor running at a 90% capacity factor with 33% thermal efficiency and a burnup of 45 GWd per tonne of enriched uranium. These are stated assumptions, not measurements of any plant.
Step 1: electricity to thermal energy. 1,000 MWe × 365 days × 90% = 7.88 TWh of electricity a year. At 33% efficiency that requires about 23.9 TWh of thermal energy, or 995,000 MWd (megawatt-days, the unit burnup is quoted in).
Step 2: thermal energy to enriched fuel. At 45 GWd/tU, the reactor consumes 995,000 ÷ 45,000 = 22.1 tonnes of enriched uranium a year. As one formula: annual tU of product = MWe × 365 × CF ÷ (1,000 × efficiency × burnup in GWd/tU).
Step 3: enriched fuel to natural uranium. At 4.5% product assay, 0.711% natural feed and a 0.22% tails assay, each kilogram of product takes (4.5 − 0.22) ÷ (0.711 − 0.22) = 8.72 kg of feed. So 22.1 tU of product needs about 193 tonnes of natural uranium, roughly 0.50 million pounds of U₃O₈ at ~2,600 lb per tU. Change the tails assay and the feed number moves; our SWU guide quantifies the trade-off.
Cross-check against the industry reference: WNA's material balance for a similar reactor (4.5% enrichment, 0.22% tails, 45 GWd/t burnup) runs 211 tonnes of natural uranium to 24.3 tonnes of enriched product a year (WNA, Nuclear Fuel Cycle Overview, updated October 23, 2026). The difference is the output assumption: WNA's figure is for 100% output, 8.76 TWh, against our 90%. Higher-burnup modern cores need less; WNA's 5%-enriched, 65 GWd/t example fabricates 16.9 tU of product a year.
| Assumption | This example | What moving it does |
|---|---|---|
| Capacity factor | 90% | Fuel use scales almost linearly with it |
| Thermal efficiency | 33% | Higher efficiency, less fuel per kWh |
| Burnup | 45 GWd/tU | Higher burnup, fewer tonnes loaded (at higher enrichment) |
| Product assay | 4.5% | Set by fuel design, with burnup |
| Tails assay | 0.22% | Lower tails, less feed but more SWU |
A first core is not a reload
Before a reactor generates anything, its core must be filled. For a 1,000 MWe light-water reactor that first load is about 75 tonnes of enriched uranium (per WNA), roughly three times an annual reload, bought and fabricated before commercial operation. After that, about a third of the core is replaced at each refueling.
Two consequences for demand analysis:
- First cores are one-time inventory demand, and they land before grid dates. A wave of new reactors pulls uranium procurement years ahead of the electricity statistics.
- Do not model a first core as "three years of reloads." It is a disclosed design quantity at specific loading assays. Multiplying an annual coefficient by three substitutes a guess for a number the developer has disclosed.
How long does a fuel load last?
Fuel stays in a reactor for about three years, per WNA. Operators replace about a third of the core every 12 or 18 months, and 18 months is the typical refueling interval worldwide. Higher-burnup fuel allows cycles of around 24 months.
Regional practice differs. WNA reports that over 80% of Asian reactors run 18-month cycles, while over 60% of European reactors run 12-month cycles.
When utilities buy vs when reactors consume
Physical consumption is smooth; procurement is lumpy. Utilities contract years ahead, take deliveries on contract schedules, hold inventory, and send material through conversion, enrichment and fabrication with lead times at each stage. EIA's Uranium Marketing Annual reports deliveries, enrichment-feed deliveries and forward coverage separately, and its 2025 survey shows deliveries and anticipated requirements year by year through 2035. Our coverage tracker charts that forward curve; the gap between contracted deliveries and anticipated requirements is procurement, not reactor physics.
A long refueling interval, as some advanced designs target, changes the timing of purchases more than the cumulative fuel per unit of electricity. Purchases come in bigger, rarer batches with more up-front inventory, while fuel per kWh stays governed by thermal efficiency and burnup.
Why SMRs, HALEU and recycling change the calculation
Everything above assumes a conventional light-water reactor. Three things break the template.
- Design-specific fuel: small modular and advanced designs differ in efficiency, burnup, enrichment and fuel form. A per-GWe coefficient calibrated on the light-water fleet is only a screening number for them. Our reactor tracker follows the pipeline.
- HALEU assays: designs using 5–20% enrichment consume much more separative work and feed per kilogram of product. Supply is covered in our HALEU supply guide.
- Heavy-water reactors and recycling: CANDU-type reactors run on natural uranium with no enrichment step (per WNA), and recycled MOX or reprocessed uranium displaces some fresh feed where it is used, mostly in Europe. See secondary supply.
How to read Yellowcake's demand model
Our site-wide screening coefficient is 170 tU per GWe-year of natural uranium, converted at 0.0026 Mlb U₃O₈ per tU, about 0.44 Mlb per GWe-year. That constant already embeds a fleet-average capacity factor of roughly 85%, so we apply it to nameplate capacity directly. Two rules for using it:
- Never multiply it by a capacity factor again. The utilization is inside the coefficient; applying it twice understates demand.
- Treat it as a screening assumption. It sits below the worked example above, which used a 90% capacity factor and specific assays, and it is labeled modeled wherever it appears, for example in the nuclear-for-AI deal book. For any named project, the design's own fuel specification beats the coefficient.
The methodology page documents the model. When the assumptions change, the figures across the site change with them.
Frequently asked questions
How much uranium does a reactor use per year? A 1,000 MWe light-water reactor at a 90% capacity factor uses about 22 tonnes of enriched uranium a year, made from about 193 tonnes of natural uranium, roughly 0.5 Mlb of U₃O₈. WNA's reference at 100% output is 24.3 tonnes enriched from 211 tonnes natural. WNA's shorthand of about 200 tonnes of U₃O₈ a year sits below our ~228 tonnes of U₃O₈ (193 tU × 1.1792) because the two rest on different assumptions.
How long does a fuel load last? Each fuel assembly stays in the core for about three years, per WNA. Operators replace about a third of the core every 12 or 18 months, and up to around 24 months with higher-burnup fuel.
How much uranium does a nuclear power plant use? Multiply the per-reactor figure by the number of units. A plant with two 1,000 MWe reactors needs about 1 Mlb of U₃O₈ a year in reloads at a 90% capacity factor, on the assumptions above.
How much uranium is in a first core? About 75 tonnes of enriched uranium for a 1,000 MWe light-water reactor, per WNA's reference figures. It is a one-time inventory purchase before commercial operation and should not be modeled as a multiple of annual reloads.
How much uranium per gigawatt? Yellowcake's screening model uses 170 tU of natural uranium per GWe-year (about 0.44 Mlb U₃O₈), with fleet-average utilization already embedded. Physics-based estimates at specific assumptions run higher or lower.
Do reactors buy uranium the year they burn it? No. Utilities contract years ahead, hold inventories, and push material through conversion, enrichment and fabrication with long lead times. EIA's annual survey separates deliveries from requirements because procurement and consumption are different time series.
Do SMRs use more or less uranium than large reactors? Per unit of electricity, it depends on the design's efficiency, burnup and fuel form. Light-water SMRs resemble the existing fleet, while HALEU-fueled designs consume more natural uranium and separative work per kilogram of product but load fuel less often.
Informational only, not investment advice. Every figure links to its primary source so you can check it yourself.