https://fordow.net/blog/posts/enriched-uranium-proliferation...
Is a good explainer about uranium enrichment.
> The most alarming aspect of 60% enrichment is how close it brings a country to weapons-grade material 4344. The enrichment work required to move from 60% to 90% is substantially less than the work needed to reach 60% from natural uranium 4546. This means a country with 60% enriched uranium stockpiles could potentially produce weapons-grade material in a matter of weeks or even days.