The DU (depleted uranium) 120mm shells he refers to are what's called APFSDS or "Armour Piercing Fin Stabilised Discarding Sabot" Depleted Uranium round for the 120mm Challenger 2 MBT's main armament. He says they will be used for the German Leopard 2 tanks.

The Sabot part is what does the damage, think of it as a dart within the munition (discarding the rest of the round on impact but leaves the dart) that penetrates the target by punching a small hole on the outside, but on the inside of say a tank, it will cause devastating damage! The Depleted Uranium part comes in as it strengthens the Sabot (dart) part of the round, but leaves behind toxic materiel on the target.

These were used in Iraq, many believe they were the cause of many illnesses and medical issues after the troops came home. I personally know one guy who this effected including his offspring.

https://www.iwm.org.uk/collections/item/object/30021556