Well, I mixed the depleted and decayed with a bit of license....
D-38 is technically "reactor depleted", relying on processed material, and reducing the amount of U238, which has a much shorter half life than other Uranium isotopes. This process occurs in nature, and in mining activity.
When you hear about radioactive dating of material, it is calibrated with the fixed ratio of Pb204 to the primordial amounts of the other lead isotopes and used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium.
In reality, primordal lead, ie 4.5 Billion years old, is not that common, with as you state, most lead in nature is an isotope, or oxide as you will, which has decayed from Polonium, Thallium, and Uranium.
I would note that DU, with the half life of U238, has spent the alpha radiation, but still emits overall radiation levels of around 60% of natural occurring Uranium.
Most commercial aircraft use DU as counterweight in the ends of the wings...should an aircraft crash, and burn...you have a serious emergency that very few, if any people, realize...
In ammunition, one of the factors was density, being almost 2 times as dense as lead, and on impact, the round would ignite. For small caliber ammunition, it was 'self-sharpening" meaning that it would not deform as lead, but would fragment, into sharp pieces.
Additional notes: I looked up reactor core. The core is made up of scintered uranium oxide, compressed with graphite and carbon. This is why DU from reactors is so dense and brittle.