[link to en.wikipedia.org]

At 94 atomic weight plutonium is the heaviest into Jupiter now....

This article states "70,000,000 bars at the center of Jupiter..."

Let's say the Pu pellets eventually break up and melt at about 1/2 way into Jupiter, if they do not fission at this point, you have widely separating "globs", tiny to a bit larger globs, of Pu drifting around but ever falling to the center....

If they do fission early, and at just 10,000,000 bars you would not need much to do it....just a tiny bit, you would get these fissioning nuclear fissile events that we are seeing come out of Jupiter....these might be from slightly larger "globs" that did not separate enough.

Whatever DOES NOT fission, makes its way to the center of Jupiter, atom by atom if need be until ENOUGH has accumulated at the center to FISSION at 70,000,000 bars.

How much Pu does that take? Not much!