It sure didn’t look like the work of a scheming brilliant mastermind here. It was brute force (inasmuch as nuns with bolt cutters could be called force) and it worked.
I think you might want to do some more reading on the others involved and the association with I think it's called "Swords to plow shears". This was more than simply a Nun with bolt cutters. There isn't signs that say processing building here. Nor are the buildings involved visible to the public.
A good chunk of the city of Oak Ridge is DOD/DOE land with one road closed to the public after 9/11 running the length of the city itself. This was just one of several facilities involved in national security. The only visible facilities are a few administrative ones located in the non fenced areas like Warehouse road. The National Lab was also once partially visible on now closed to the public Bethel Valley Road but parts of it were open to the public at one time IIRC. These facilities are several miles apart from each other. Someone had to tell them which building was which.
A little bit more info http://archive.wbir.com/news/article/239165/2/Y-12-demonstrators-release-photo-of-their-security-breach