I think 20% is sufficent to get a reactor started.
A bomb needs around 90% for it to work assuming all other factors are designed correctly.
BTW, the North Korea, India and Pac bombs were all considered duds because the “other factors” failed.
Other than the radiation effects, 2-3 semi’s filled with Nh3OH would have yielded the same and have been MUCH cheaper.
About 3% enrichment will operate a commercial reactor. About 8% will operate a compact propulsion reactor. About 20% will make a low yield, large nuclear weapon. About 90% will make a small, efficient bomb that will fit on a missile.
It is difficult to get to 20% enrichment; not so hard to go from 20 to 90% enrichment. It just takes a little more time.