Separative work (SWU), feed required, and the full dollar cost of enriched uranium — feed, conversion and SWU — on one page. Other calculators stop at SWU; this one carries it through to $/kg and shows the HALEU vs LEU cost premium side by side. Every formula is shown with its working.
Live visualization — natural feed → cascade → product + tails, bar widths scale with mass per kg product
Feed / product—SWU / kg—Waste / product—
Enrichment job
LEU is below 5%. HALEU is 5–20% (19.75% nominal). Must be above the feed assay.
The U-235 left in the depleted tails. Lower tails = less feed but more SWU. Benchmark basis = 0.20%.
Natural uranium = 0.711%. Edit only for re-enrichment of tails or reprocessed uranium.
Prices spot · Aug–Sep 2026
≈ $90 / lb U₃O₈
$ / kgU, applied to the feed mass (U₃O₈ → UF₆, before the cascade). NA spot ≈ $65/kgU.
Results — per this job
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Natural feed required
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Mass of natural uranium that must be fed to the cascade.
Show the math ▾
Separative work required
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Show the math ▾
Total cost feed + conv + SWU
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Feed Conversion SWU
Show the math ▾
Unit cost of enriched product
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Cost per kg of enriched uranium product (EUP), all three steps included.
HALEU vs LEU — cost premium your tails & prices
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Per kg product
LEU 4.5%
HALEU 19.75%
Premium ×
LEU 4.5% — /kg
HALEU 19.75% — /kg
Frequently asked questions
What is a separative work unit (SWU)?
A separative work unit (SWU) measures the effort required to separate uranium isotopes during enrichment. It is defined through the value function V(x) = (2x−1)·ln(x/(1−x)), and the separative work for a job is SWU = P·V(x_p) + W·V(x_w) − F·V(x_f), where P, W and F are the product, waste and feed masses and x is each stream's U-235 fraction. SWU is independent of price: it quantifies physical separation effort, and the market then attaches a dollar value per SWU.
How much more does it cost to enrich HALEU than LEU?
Per kilogram of product, enriching to 19.75% HALEU costs several times more than to 4.5% LEU. At 0.711% natural feed and 0.20% tails, HALEU needs about 45.1 SWU/kg versus about 7.7 for LEU (a 5.9× ratio), and roughly 38 kg of natural feed per kg of product versus about 8.4. At 2026 spot prices (SWU ≈ $200, conversion ≈ $65/kgU, feed ≈ $234/kgU) that works out to roughly $20,000/kg for HALEU against roughly $4,000/kg for LEU — about a 5× premium. Exact figures depend on the tails assay and prices you enter above.
Why is HALEU so expensive to enrich?
Two costs rise together. Reaching 19.75% requires far more separative work per kilogram than reaching 4.5%, and it also requires far more natural uranium feed. Because the conversion fee is charged on the feed mass, it scales up with the feed as well. So HALEU pays more on all three fronts — feed, conversion and SWU — at the same time, which is the cost wall that advanced-reactor and SMR fuel must clear.
How much SWU does it take to make 19.75% HALEU versus 4.5% LEU?
Assuming natural uranium feed at 0.711% U-235 and a tails assay of 0.20%, producing one kilogram of 19.75% HALEU requires about 45.1 SWU, while one kilogram of 4.5% LEU requires about 7.7 SWU — a ratio close to 5.9. These are this calculator's benchmark anchors. Raising the tails assay reduces both numbers because less U-235 is left behind in the tails stream.
What is the tails assay and how does it change the cost?
The tails assay is the fraction of U-235 left in the depleted uranium that leaves the cascade, typically 0.20%–0.30%. A lower tails assay squeezes more U-235 out of each kilogram of feed, so you buy less natural uranium but spend more separative work; a higher tails assay does the reverse. Enrichers choose an optimum tails assay that minimizes total cost for the prevailing ratio of uranium price to SWU price — which is why this tool lets you edit it.
How is the price of enriched uranium calculated?
The cost of enriched uranium product has three components. Feed: the feed mass × the uranium price per kgU. Conversion: the feed mass × the conversion fee, because uranium is converted from U₃O₈ to UF₆ before it enters the cascade. Enrichment: the separative work × the SWU price. Fabrication is added separately and is not modelled here. In formula form: cost = F·(feed$ + conversion$) + SWU·(SWU$).
What SWU, conversion and uranium prices does this calculator use?
The default prices reflect 2026 spot levels — enrichment at record highs around $200–215/SWU, conversion around $65/kgU, and natural uranium around $90/lb U₃O₈ (≈ $234/kgU). All three are editable, so you can enter current market numbers or your own contract prices. Real published spot prices are proprietary to TradeTech and UxC; the defaults are drawn from their month-end figures and refresh from an editable price file.
Educational estimate — not a procurement quote or fuel-supply contract basis. This tool uses the ideal-cascade separative-work model (Benedict–Pigford–Levi value function) with user-supplied spot prices. Real enriched-uranium pricing depends on term contracts, enricher-specific tails optimization, UF₆ vs U₃O₈ accounting, fabrication, financing and logistics not modelled here. Verify against enricher quotes and your own fuel-cost model before acting.
How to use this calculator
Work out the separative work (SWU), the natural uranium feed, and the full dollar cost to enrich uranium to any assay — then compare HALEU against LEU on the same basis.
1. Describe the enrichment job
Product assay x_p — how enriched you want the product (e.g. 4.95% for a PWR reload, 19.75% for HALEU). Use the preset buttons or type any value.
Product mass P — how much enriched product you need, in kg or metric tonnes (MTU).
Tails assay x_w — the U-235 left behind in the depleted tails. Lower tails squeeze more U-235 out of each kg of feed, so you buy less uranium but spend more SWU. 0.20–0.30% is typical.
Feed assay x_f — 0.711% for natural uranium. Change it only for re-enriching tails or reprocessed uranium.
2. Set the prices
SWU price — the market rate for one separative work unit. Enrichment spot hit record highs in 2026.
Feed price — the cost of natural uranium, in $/kgU. Roughly $/lb U₃O₈ × 2.6.
Conversion — the fee to turn U₃O₈ into UF₆ before enrichment. It is charged on the feed mass, so it scales with how much uranium you buy — which is why it weighs more heavily on HALEU. Switch it off to see SWU + feed only.
3. Read the results
Feed required, SWU required, and the total cost broken into feed / conversion / SWU, plus the unit cost per kg of product.
The HALEU vs LEU card re-runs the whole calculation for 4.5% and 19.75% at your tails and prices, and shows the premium multiplier — the headline number for HALEU economics.
V is the dimensionless separation potential; SWU measures the effort to separate isotopes, independent of price. Assays are converted to fractions internally. Every number and its source is in the footer.