[Blood of Tyrants]

As far as I know, the cockpits are the only armored sections, and not all of them are.

[JasonC]

Think A-10. Those are heavily armored, to withstand ground fire up to 23mm AA. This sounds like a uranium metal liner for a HEAT warhead. HEAT channels an explosive jet to direct a stream of molten metal at the plate the warhead strikes. A denser metal makes a better "cutting tool" than a less dense one. Tungsten, lead, or uranium will all serve. (Why use uranium? Gets rid of nuclear reactor fuel byproducts). This is not a radiological weapon, dirty or otherwise. It is a conventional air to air heat seeking missile, the Russian version of the AIM-9 Sidewinder, that uses uranium for its properties as a dense metal in its HEAT warhead design.