They have a big particle accelerator used for nuclear physics.
It also is used to check out satellite electronics to assure that cosmic rays or the van Allen belt does not mangle up the sat, costing big bucks if they fail or scramble data.
They also do spacecraft shielding tests for manned flight.
The accelerator and its feeder (Tandem van de Graaf with a linear accelerator and storage ring) are all underground.
They do a bunch of other things but those are the things I’ve been involved with there.
Sounds important,are there private companies that can do this work?
Well, it’s very old. It was old when I visited there in the 1970’s in my grad student days. I can’t make any judgement as to its current viabilty, although I would think it might be a unique resource.
OTOH, its primary mission has passed it by, I feel sure.