...The years rolled by and top-secret projects were initiated in America and Israel to replace the old SADM with its heavy weight and excess radioactivity, culminating in the successful development and testing at Dimona during 1981 of the “new” micro nuclear device. Using advanced nuclear physics, the scientists found a way of detonating the new “suitcase” bomb without the use of a Uranium 238 reflector, and further refined the Plutonium 239 in its core to 99.78%.
These measures resulted in a weapon considerably smaller and lighter than SADM, which also had another enormous advantage. The new Dimona micro nuke was the very first critical weapon that could be used in “stealth” mode. Gone was the dirty Uranium 238 reflector, and up went the purity of the smaller Plutonium 239 core.
Plutonium emits only alpha radiation, which is for all practical purposes “invisible” to a standard Geiger counter. In direct contrast with its more deadly cousins beta and gamma, alpha can travel only a few feet and is incapable of penetrating human skin. Remember that this micro nuke is a tiny weapon in terms of critical mass, with its limited number of particles distributed over a very wide area.
You will have to be within five feet to detect a single particle. Though the alpha particles cannot penetrate the skin, such radiation is extremely hazardous if inhaled because Plutonium is the most toxic substance known to man.