No nuke expert by any means. Years ago seem to remember reading about neutron bombs to preserve some of the architecture and infrastructure, it would just do away the those pesky human beings.
From wiki
https://en.wikipedia.org/wiki/Neutron_bomb
"A
neutron bomb, officially termed as a type of
Enhanced Radiation Weapon (ERW), is a low yield
thermonuclear weapon designed to maximize lethal
neutron radiation in the immediate vicinity of the blast while minimizing the physical power of the blast itself. The neutron release generated by a
nuclear fusion reaction is intentionally allowed to escape the weapon, rather than being absorbed by its other components.
[3] The neutron burst, which is used as the primary destructive action of the warhead, is able to penetrate enemy armor more effectively than a conventional warhead thus making it more lethal as a tactical weapon."
Edit add: Another source:
http://www.fact-index.com/n/ne/neutron_bomb_1.html
"A
neutron bomb is a type of
nuclear weapon specifically designed not to produce a massive explosion and significant infrastructure damage, but rather to completely irradiate an area with
neutron radiation, killing all living things while leaving the infrastructure relatively intact. Though a neutron bomb does cause infrastructure damage and some long term radiation (it is still a nuclear weapon after all), they are specifically designed so that ~48 hours after the device is detonated, friendly troops can move into an area and utilize the infrastructure without fear of radiation. Thus, neutron bombs are generally seen more as a
tactical nuclear weapon than a
strategic one. Due to this focus on tactical use, neutron bombs comprise some of the smallest nuclear weapons ever built (though the American bazooka-launched
Davy Crockett warhead is not, as is sometimes claimed, a neutron bomb device -- it employs a standard
fission warhead).
Technical Overview
Neutron bombs, also called enhanced radiation weapons (ER), are small nuclear weapons in which the burst of neutrons generated by the fusion reaction is intentionally not absorbed inside the weapon, but allowed to escape. The X-ray mirrors and shell of the weapon are made of
chromium or
nickel so that the neutrons are permitted to escape. This intense burst of high-energy neutrons is the principle destructive mechanism. Neutrons are more penetrating than other types of radiation so many shielding materials that work well against gamma rays do not work nearly as well. The term "enhanced radiation" refers only to the burst of ionizing radiation released at the moment of detonation, not to any enhancement of residual radiation in fallout (contrast this with salted bombs)."
2nd edit: An interview with the neutron bomb's inventor, Cohen. His opinion on the nuclear give and take and effectiveness of them in 1997
http://www.manuelsweb.com/sam_cohen.htm
