Absolutely 100% correct. Thanks to Teller and Oppenheimer, we were given a weapon that is almost pure radiation that goes all the way thru the planet to the core (so underground shelters are useless). It simply vaporizes all organic life forms that are fauna based (animals and people) without destroying buildings or flora (plants). The radiation goes away enough in about four days for the area to be occupied without fear of radiation poisoning. You can limit the dispersal by adjusting the altitude at which the weapon is detonated and by the size. Local populations would only have to evacuate (and take livestock and pets) for a short time before they could move right back. So why did Jimmy (Peanut Brain) Carter remove that weapon from the arsenal of Freedom? He had our stockpiles eradicated.
I hesitate to correct you on this because it sounds like this is a deeply held belief. I am not sure where you are getting your information... but it is inaccurate, greatly exaggerated and worst of all it just makes you sound silly.
Neutron radiation has no electrical charge and the particles vary in size... so shielding does create some interesting challenges. Effective shielding generally requires a composite structure with elements of both high and low atomic numbers. But neutron radiation does not penetrate to the core of the earth and underground shelters can still be effective. It also does not vaporize animals while leaving plants intact.
I am not a nuclear scientist but for years I was one of the leaders of a big city hazmat team and we spent a great deal of time studying nuclear threats. You should go ahead and do a little more research... and probably not on the websites that gave you this phony information.