if it is so easy
then what is iran waiting for?
Well the only and rather the most critical building block for a nuke is the fissile material. Purer the material, smaller the critical mass pile and hence smaller the device. But you should understand that "Anything" that spontaneously disintegrate or technically speaking, radioactively decay in to smaller/lighter atoms by breaking bigger atoms and in process releases energy,free neutrons and protons can be termed as "Nuke". These substances do this thing spontaneously only when they come together in critical mass. Now a "Nuke" could have anything in it as a fissile material, but it's quantity will vary. Quantity will have to vary not because of yield but because of the critical mass of the substance. Yes more material than critical mass more yield, But bare minimum weight of the material should be it's critical mass.
Eg: The nominal spherical critical mass for an untampered U235 nuclear weapon is 56 kg. Pu-239 has the smallest critical mass, spherical untampered critical mass is about 11 kg.Pure uranium-233 has a critical mass of about 15kg. Heck even the most un reactive metal in the family Thorium, Th229 can be weponised with a critical mass of 2839Kg or 994Kg with steel reflector plates.
So the above just goes on to show that creating weapons grade material is to have right amount of fissile material. Now one would ask "How can we get theses assorted metals?? Super powers are investing billions on nuclear reactors for harvesting them and won't sell those designs." Well one dose not need those shiny new reactors for creating weapons grade fissile material, if one knows what they are doing. Donn believe me, well then just look at
Chicago Pile-1 As described by Enrico Fermi himself ,"a crude pile of black bricks and wooden timbers.".All it was needed was the a solid technical knowledge base. And that was the reason why teenagers are building these reactors in their backyard.
The Radioactive Boy Scout . Note the year :1995, before the age of Wikipedia.
So yes it's easier to make Nuke than making a high performance Jet Engine.
