Why is depleted uranium not needed for armour piercing ? Nuclear reactors work like any fire : carbon and hydrogen increase energy output. As in a Diesel motor, pressure also helps. Here https://en.wikipedia.org/wiki/Critical_mass#Changing_the_point_of_criticality -> "Varying the density of the mass The higher the density, the lower the critical mass." — This is used in ALL nuclear bombs. And it allows to reach a much more limited supercriticity with very little pieces of highly enriched uranium or plutonium. A few grams only, that are used indeed in all CONVENTIONAL antitank warheads. So they do not need DU. DU is added since Vietnam to genocide people ! Iraq, Afghanistan, Pakistan, Yemen, Syria… Even a retired French Army general (P-M Gallois) said it is a "crime against humanity" !