- At low enrichments (<3% U): Criticality is not possible without a moderator. Large containers (up to 2.5 tonnes) can be used, but moisture ingress must be rigorously prevented.
- At high enrichments (>5% U): Strict criticality controls are required, including geometry control, mass limits, and moderation exclusion.
- UF₆ in liquid form (during processing) is of particular concern because of its higher density compared to the gaseous form.
Lesson 2 ◆ 2.8 Enrichment Facilities and Proliferation Concerns