No. That is not a nuke. It is a mass simulator, specifically the electronic model of a mass simulator for a warhead. The various colors represent density of material. This would be used during aerodynamic simulations. That is why it is behind the graph about processors. This also explains the simple geometry as keeping things simple reduces the number of calculations.

(Note that nuke warheads fall nose-first, the opposite of space capsules. So the dense material is packed in the nose, with the lighter stuff at the back.)

The nearby disk looks like a represention of airflow around a falling warhead. They, like apollo, likely had an offset center of gravity that allowed them to stear by rotation, creating the asymetrical airflow shown on the disk. Falling in a spiral also probably frustrates interception. So that whole corner of the image is advertising Sandia's ability to do aerodynamic simulations.