This type of attack isn't likely to cause a 'meltdown', since the uranium is usually in a very hot vaporous form while being centrifuged. If the containers rupt

This type of attack isn't likely to cause a 'meltdown', since the uranium is usually in a very hot vaporous form while being centrifuged. If the containers rupture, it will spread out and condensate in a thin layer that's not very likely to reach criticality. Nuclear reprocessing absolutely has dangers, but meltdowns aren't really the issue.