>>507426652 (OP)What you really want to make nukes easily is plutonium to use as a lightweight neutron trigger.
the hard part is getting plutonium, which is an artificial element, IE it's half life is so short you have to manufacture it.
You can use Uranium 235 but then you still need alot of material to get it started as intended.
alternate layers of deuterium, tritium, and helium 3 or 4 to make extra spicy
also some materials reflect neutrons, see also demon core incident