Only thing to add, neutrons are very high energy, they can go through 8 feet of lead.
Lead just doesn’t work with neutrons, they have too much energy.
If you can dampen the energy of neutrons, like adding speed bumps, then the lead will finally stop it.
But this experiment is so small, they either have hardly no neutrons or none at all. I believe none at all myself.
Know why he is in Florida, wants to defraud some of those rich seniors.
*Which* neutrons have high energy? The neutrons sitting inside the carbon atoms in the plastic in my keyboards aren't going through eight feet of anything: they're just wobbling there, in accordance with the Uncertainty Principle.
Cheers!
My understand is that fission can be encouraged by slowing neutrons down (thermal neutrons) by surrounding the fuel elements with a "moderator" like graphite. The first controlled chain reaction was observed in a "pile" of graphite blocks interspersed with the uranium fuel rods. There were also "control rods" used to regulate the number of fission events by absorbing neutrons. Elements like boron or xenon gas come to mind as neutron absorbers. Rods all the way in to quench the reaction completely, partly withdrawn to permit fission events, all the way out gives one a "Chernobyl".
Regards,
GtG
PS Old timers still refer to nuclear reactors as "piles", old memories die hard.