One point first : a French veteran (former AMX30RC tank driver) has confirmed fully the use of nano levels of nuclear fission in all the “conventional” heavy weaponry of the French army.
The recipe (you’ll need a centrifuge plant, very good explosives, a good cannon or missile and a nuclear reactor) :
Some very depleted uranium (the more depleted, the better, for instance you’ll find that French depleted uranium is officially acknowledged as going down to 0.14% of U235)
A few grams of highly enriched uranium (HEU)
A powerful alpha or gamma emitter, or tritium (produced in a nuclear reactor)
Beryllium used in combination with the alpha or gamma source for neutron generation
Hydrogen-rich plastic !
We make a depleted uranium arrow so that the body is made of highly depleted uranium (in an alliage so very solid) and the tip of highly enriched uranium (without an alliage so highly ductile). The whole ammunition has a percentage of U235 of 0.2%, but you can climb to 0.72% so that the resulting ash can be discarded as coming from the ground (as in the case of the Khiam crater where, in spite of an uranium concentration 10 times higher in a short perimeter around it, UNEP used the fact it was natural uranium to discard the military origin). This allows to use of course more HEU on the tip.