H bombs use a small plutonium core fission reaction to initiate a hydrogen fusion reaction. Fission reactions, like what we use in nuke plants, are highly radioactive as are their byproducts. Fusion reactions don’t have these issues, 95+ % of the radiation from an H bomb are from the plutonium core fission reaction.
And 99% of all the radiation in a bomb is released within the fist minute of the blast. The other 1% is fallout blown up into the air.
A H bomb is a Bomb with a fission core, wrapped in heavy water then wrapped in a fission wrapping. A nuetron bomb is simply a bomb without the outer wrapping. Very clean and limited in blast capabilities.