.....Think of a magnesium fire ...
I have in mind a uranium bullet that penetrates tank armour and becomes incandescant but remains intact. they are said to rattle around in the tank.
If there was a moab, I don’t think the explosion would be capable of disintegrating the uranium mass. It might be blown away, but is intact where it landed. If intact, it is recoverable.
It could go either way.
Were I the attacker I’d do all I could to light it. Thermite cluster munitions maybe?