The OP article mentions that part of the manufacturing will make use of the existing “hardened” infrastructure. I've been around hardened infrastructure around certain hazardous industrial equipment but hardening around these old military munition plants is off the charts.
One of the old munitions manufacturing sites I did some things at has been in continuous operation since WW2 making munitions of the same general type. The manufacturing trains and the storage areas are in long, narrow buildings divided into about 20x20ft rooms with doors opening into a wide hallway running the length of the building.
Each manufacturing room has equipment doing one step of the process. Small openings between adjacent rooms pass the pass the munition from room to room via a blast lock such that the rooms are never directly connected by an opening. Walls, ceilings and floors are several feet thick reinforced concrete. Doors to the hallway and to the wall locks are several inch thick of armor grade steel and had a small glass viewing port as thick as the steel door. Equipment now is fully automated and remotely observed by CCTV.
Back in the day, a handful of workers would be in each bay operating the equipment. What was different from my industrial experience is that the manufacturing bays were designed to contain an explosion instead of directing one towards safe direction. In addition, each bay was originally and still is connected to a water deluge system that will fill a bay floor to ceiling in seconds. Refer back to the top where I mentioned that originally, the bays were each staffed with several workers - No escape from fire, explosion or drowning.
My father in law, was a division manager at Pantex. I took him for his last visit in Oct 2009. He died in December 2009.
They once had an incident of an explosion in a bay, caused by cutting shaped charges. Operator error. He violated cut rate, was angry. Lives were lost.