If an elderly nun and two of her friends can break through four fences and approach a modern facility holding highly enriched uranium, then there's no hope for the security there. It's almost as if the sentence reflects the government's embarrassment that a contractor had such bang-up security. Honestly, these folks did the D.O.E. and the U.S. federal government a HUGE favor by pointing out glaring security holes. Holes, that, if exploited by a terrorist or militant group, could have lead to a real serious incident.
I'm not arguing for clemency for these folks - they did costly damage to a vital piece of nuclear security infrastructure.
Perhaps the responsibility for uranium storage should be placed in the hands of the military, not civilian agencies like the D.O.E. and government contractors that can't do the job they've been paid to do?