LEU meaning

In nuclear regulatory and export control practice, LEU (low enriched uranium) means uranium that has been enriched in the fissile isotope uranium‑235 to less than 20% by weight. It is contrasted with highly enriched uranium (HEU), which is 20% U‑235 or more. LEU is a widely used technical descriptor across nuclear law and non‑proliferation compliance rather than a term generally defined in UK or Irish primary legislation. The 20% threshold reflects established international usage (including IAEA practice) and is used to categorise nuclear material for licensing, safeguards reporting and security measures. Typical legal contexts include: classification of nuclear material, nuclear safeguards accounting and notifications, strategic export and brokering controls, and regulation of the transport and storage of nuclear substances. Reactor‑grade fuel (commonly about 3–5% U‑235) is LEU. Usage is broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland. While the specific regulatory frameworks differ (for example, UK nuclear safeguards and UK strategic export control lists, and in Ireland the Euratom/EU framework and national export controls), the practical meaning of LEU and the less‑than‑20% enrichment boundary are applied in the same way.