Nuclear fuel enrichment range — enriched uranium definition: Enriched uranium may contain fissionable U-235 content in approximately which range (expressed as percent by weight of U-235)?

Introduction / Context:
Enrichment increases the fraction of the fissile isotope U-235 in uranium beyond its natural level (~0.7%) to meet reactor or other application requirements. Understanding the broad range of enrichment is useful in power engineering and nuclear technology contexts.

Given Data / Assumptions:

• Natural uranium: about 0.7% U-235 and the rest mostly U-238.
• Low-enriched uranium (LEU): up to about 20% U-235, commonly 3–5% for light-water reactors.
• Highly enriched uranium (HEU): greater than 20% U-235; special applications can exceed 90%.

Concept / Approach:
By definition, “enriched uranium” is any uranium with U-235 fraction above natural. Practical uses span from a few percent for power reactors to very high percentages for research or other specialized applications. Hence, a very wide range—from just above 1% to well above 90%—fits under the enriched umbrella, up to nearly pure U-235 in theoretical terms (recognizing practical and regulatory limits).

Step-by-Step Solution:

Verification / Alternative check:
Textbook classifications of LEU and HEU confirm that enrichment spans from slightly above natural up to very high percentages depending on application; power fuel and weapons-grade examples illustrate the lower and upper ends.

Why Other Options Are Wrong:

• 1–40%, 10–50%, 1–80%: These subsets omit legitimate higher or lower enriched ranges, making them incomplete.

Common Pitfalls:
Confusing “typical power-reactor enrichment” (3–5%) with the definition of “enriched” more broadly; the term encompasses far more than one application.

Final Answer:
1 to 99%