Looks like the penetrator could be depleted uranium, but other than concern in the public eye over the word "uranium" and the fear it implies, there isn't much to worry about with depleted uranium, hence the word depleted. If this was a manufacturer's made cutaway it could be that the DU was replaced by steel or some other non-DU metal. There is no lethal or dangerous radiation coming from DU, only alpha, which is so weak it will not penetrate a sheet of paper. The only hazard with DU is ingestion or absorption through open cuts, sores, etc. of dust or particles. The hazard of DU in the larger caliber penetrators is after impact with the target when DU dust and residue is in and around the target that can be ingested if it becomes airborne. It is then heavy metal poisoning. Just don't lick or chew on the 12.7 penetrator and if you handle the penetrator wash your hands and all is well.
I do have to respectfully disagee though that DU is not a penetrator. It is a very effective penetrator of armor and because of its pyrophoric properties is a much more lethal penetrator than copper. The attachment is a 20mm DU penetrator effectively passing thru a tank. Admittedly the armor it went through is not the heaviest part of the tank and why they would place the tank on its side is unknown, but it is an impressive sight.