Scientists Detect Signs of a Hidden Structure Inside Earth's Core

I'd be interested to hear from someone with geological expertise what the likelihood of a dense inner core of fissible elements (uranium, plutonium, etc.), and/or their decay products (ultimately lead), within the iron-nickel inner core might be.

I'm aware that radioactive decay from such heavy elements accounts for about half of the heat production within the Earth (the remainder being the legacy of gravitational potential energy of formation). But it's been unclear whether density differentials and plasticity are sufficient for heavier elements to sink within or remain distributed throughout the nickel-iron of the imputed interior.