The short answer to whether a cobalt bomb exists is no; no nation has ever built or tested a weapon specifically designed as this type of radiological device. It remains a hypothetical “salted bomb,” engineered not for maximum blast yield, but for maximum, long-term radioactive fallout. This theoretical weapon is capable of rendering vast areas uninhabitable for decades, a fate far more prolonged than that caused by standard nuclear fallout.
The Theoretical Design of a Salted Bomb
The cobalt bomb is a specific example of a theoretical weapon known as a “salted bomb,” designed to greatly enhance the amount of radioactive contamination. This design begins with a standard thermonuclear weapon, commonly referred to as a hydrogen bomb or H-bomb. A conventional thermonuclear device uses a two-stage process where a fission explosion triggers a fusion reaction.
Instead of the usual casing material, the warhead is wrapped in a jacket made of non-fissile, stable Cobalt-59 (\(^{59}\)Co). When the thermonuclear core detonates, the fusion reaction generates an extremely intense burst of neutrons. These high-energy neutrons bombard the surrounding Cobalt-59 jacket.
The bombardment causes a process called neutron activation, which transmutes the stable Cobalt-59 into the highly radioactive isotope Cobalt-60 (\(^{60}\)Co). The incredible heat of the explosion then vaporizes this newly formed Cobalt-60. This radioactive vapor rises into the atmosphere, condenses into fine dust, and settles back down to Earth, contaminating a massive area as fallout.
Why Cobalt is Used to Maximize Radiological Hazard
Cobalt-60 is considered the ideal material for a long-term radiological weapon because of its specific decay properties. Most isotopes produced by standard fission or fusion reactions have relatively short half-lives, meaning their intense radiation dissipates quickly. In contrast, Cobalt-60 has a half-life of 5.27 years.
This half-life is long enough for the radioactive dust to be distributed globally by atmospheric winds before significant decay occurs. It is also short enough to produce exceptionally intense gamma radiation during its decay. Cobalt-60 decays by emitting a beta particle and two powerful gamma rays with energies of 1.17 MeV and 1.33 MeV.
These high-energy gamma rays are highly penetrating, posing a severe external radiation hazard to any life form in the affected area. Fallout from a cobalt bomb would render large regions effectively uninhabitable for many decades, as the radiation requires ten to twenty half-lives to decay to relatively safe levels.
Development Status and Confirmation of Non-Existence
The concept of the cobalt bomb was first introduced and popularized by Hungarian-American physicist Leo Szilard in 1950. Szilard’s intention was not to promote its development but to serve as a stark warning about the potential for nuclear weapon technology to create a self-defeating “doomsday device.”
The primary deterrent against its construction lies in its lack of strategic military value. A cobalt bomb would contaminate the target area so completely that the land would be useless even to the attacker.
Furthermore, the nature of the long-lived fallout violates the principle of Mutually Assured Destruction (MAD) through self-deterrence. The radioactive cloud would be carried by global weather patterns, eventually contaminating the country that launched the attack and its allies. Because the weapon is designed purely for catastrophic, long-term contamination that respects no borders, its use would be suicidal.