Fact Check: "Enriching uranium to 90% purity is necessary for nuclear weapons."
What We Know
Enriched uranium is a form of uranium in which the concentration of uranium-235 (U-235) has been increased through isotope separation. Naturally occurring uranium consists mainly of uranium-238 (U-238), with only about 0.7% being U-235, which is the isotope that can sustain a nuclear chain reaction (Wikipedia).
For nuclear weapons, uranium must be highly enriched, typically defined as having more than 20% U-235 content. Weapon-grade uranium is generally considered to be enriched to 90% U-235 or more (Fact Sheet). The enrichment process involves using centrifuges to separate U-235 from U-238, which is not useful for sustaining a nuclear reaction in weapons (NRC.gov).
While low-enriched uranium (LEU), which contains less than 20% U-235, is used in most nuclear reactors for electricity generation (typically around 3-5% U-235), highly enriched uranium (HEU) is necessary for nuclear weapons and some specialized reactor designs (Wikipedia, World Nuclear Association).
Analysis
The claim that "enriching uranium to 90% purity is necessary for nuclear weapons" is partially true. While it is accurate that uranium must be highly enriched to be used in nuclear weapons, the threshold for weapon-grade uranium is generally considered to be around 90% U-235. However, technically, uranium enriched to as low as 20% can still be weapon-usable, although it would require a significantly larger quantity to achieve a critical mass necessary for a nuclear explosion (Wikipedia, Fact Sheet).
The distinction between 20% and 90% enrichment is crucial. Enriching uranium to 20% represents about 90% of the effort needed to produce weapon-grade material, making it a critical threshold for proliferation concerns (Fact Sheet). Thus, while 90% enrichment is the standard for weapon-grade uranium, it is not the only level that can be used for nuclear weapons, albeit less practically.
The sources used in this analysis are credible, with the Wikipedia entry providing a comprehensive overview of uranium enrichment and its applications, while the NRC and World Nuclear Association offer authoritative insights into the technical aspects of uranium enrichment processes. The Fact Sheet from the Arms Control Center also provides a balanced view of the implications of uranium enrichment for both civilian and military purposes.
Conclusion
Verdict: Partially True
The claim that enriching uranium to 90% purity is necessary for nuclear weapons is partially true because while 90% enrichment is the standard for weapon-grade uranium, uranium enriched to as low as 20% can also be weapon-usable, albeit less efficiently. Therefore, while 90% is a critical threshold for nuclear weapons, it is not strictly necessary for the creation of a nuclear weapon.
