Nuclear Fuel Cycle Calculator
Estimate uranium mass and separative work units (SWU) needed to fuel a nuclear power reactor over one cycle. Used by nuclear engineers and fuel cycle analysts to plan procurement and enrichment costs.
About this calculator
A light-water reactor requires enriched uranium fuel whose production involves two key quantities: the mass of natural uranium feed and the separative work needed to enrich it. Fuel consumption depends on reactor thermal output, capacity factor, and discharge burnup (how hard the fuel is used, in MWd/tonne). The separative work factor uses the value function V(x) = (1 − 2x) × ln((1 − x)/x). SWU per tonne of product = V(xp) − (wp/wf) × V(xf) − (wp/ww) × V(xw), where xp, xf, and xw are product, feed, and tails assays. The calculator combines annual energy output (reactor_power × capacity_factor/100 × 8,766 MWh/yr) with burnup to find fuel mass, then applies the enrichment equation to find total SWU requirements.
How to use
Suppose a 1,000 MWe reactor runs at 90% capacity factor with a burnup of 45,000 MWd/tonne, enriched to 4.5% U-235, and tails assay of 0.3%. Annual energy = 1,000 × 0.90 × 8,766 = 7,889,400 MWh = 329,000 MWd. Fuel needed = 329,000 / 45,000 ≈ 7.3 tonnes of enriched uranium per year. The logarithmic enrichment term ln(4.5/0.3) / ln((4.5−0.3)/0.3) ≈ ln(15)/ln(14) ≈ 2.708/2.639 ≈ 1.026 is then applied to calculate SWU requirements for procurement planning.
Frequently asked questions
What is discharge burnup and how does it affect uranium requirements?
Discharge burnup measures the total energy extracted from each tonne of fuel, expressed in megawatt-days per tonne (MWd/tonne). Higher burnup means more energy is wrung from each fuel assembly before it is removed, so fewer tonnes of enriched uranium are needed annually. Modern LWR fuels achieve 45,000–60,000 MWd/tonne. Increasing burnup generally requires slightly higher enrichment, creating a trade-off that this calculator helps you optimize.
What is a tails assay and why does it matter in uranium enrichment?
The tails assay is the residual U-235 concentration (%) in the depleted uranium 'waste' stream leaving the enrichment plant. A lower tails assay (e.g., 0.2%) extracts more U-235 but consumes more separative work; a higher assay (e.g., 0.35%) uses less SWU but wastes more natural uranium. The economically optimal tails assay depends on the relative prices of natural uranium and enrichment services. Utilities routinely adjust their tails assay contracts as commodity prices shift.
How are separative work units (SWU) used to price uranium enrichment?
Separative work units are the standard commercial measure of the effort required to enrich uranium. Enrichment plants sell capacity in SWU, typically priced in USD per SWU. The total enrichment cost for a fuel reload equals the SWU requirement multiplied by the prevailing SWU price, plus natural uranium feed costs. Because SWU and uranium feed are partial substitutes, buyers can choose a tails assay that minimizes total fuel cost given current market prices for each input.