A salted bomb is a nuclear weapon designed to kill or to render an area uninhabitable by means of radioactive fallout. Such bombs are created by taking a fission or fusion [aka atomic or hydrogen] bomb and surrounding it with material containing an element that will be converted to a radioactive isotope by neutrons generated when the bomb is detonated.
The attraction of salted bombs is that by varying the lining material different effects can be produced. For example, lining a bomb with lithium will result in part of the lithium being converted to fluorine 18. This would very rapidly kill people downwind of the bomb. Fluorine 18 has a half-life of only two hours. That means that the fallout loses half its potency every two hours. An attacker’s troops would be able to move into a city that had been attacked by a fluorine 18 salted bomb within a day or so.
The Soviet Doomsday Machine that exploded at the end of the 1964 satirical film Dr. Strangelove was a bomb salted with cobalt. Detonating such a bomb would produce the radioactive isotope cobalt 60. This has a half-life of 5.26 years. Such a long half-life would give the fallout time to spread around the world, killing all animal life [including us]. This is the premise of the 1957 novel On the Beach by Nevil Shute.
A sense of how salted bombs might be created and used is given by these pages from a 1976 novel.
The Shah had a program to develop nuclear weapons and here he discusses a ‘shopping list’ for salted bombs with his weaponeer.
A salted bomb is not the same as a dirty bomb. Dirty bombs are easier to produce because the consist of a conventional explosive surrounded by some radioactive material. Dirty bombs are terrorist weapons. A salted bomb requires a nuclear bomb to generate the neutrons which produce the radioactive isotope and can therefore only be produced by states.
A salted bomb is not the same as a neutron bomb. Neutron bombs were produced to attack tank formations [armoured vehicles are highly resistant to the heat and blast effects of conventional nuclear weapons]. They kill tank crews by bombarding them with a blast of neutrons and produce less heat, blast and fallout than conventional nuclear weapons. Neutron bombs were also produced to protect cities and silos by disrupting the warheads of incoming nuclear missiles.
Gold has been proposed for short-term fallout (days), tantalum and zinc for fallout of intermediate duration (months), and cobalt for long term contamination (years).
A cheaper salted bomb could be produced by lining a warhead with common salt. Salt is a compound of sodium and chlorine. When a bomb lined with salt is detonated the sodium is converted to sodium 24 which is a highly radioactive isotope with a half-life of fifteen days. Sodium 24 fallout is also produced when unsalted nuclear weapons are detonated in the sea.
A sodium 24 exposure calculator is shown below.
No country has admitted to having salted bombs but it would be surprising is several did not have them. Israel is believed to have several in various ‘flavours’. Pakistan may also have them. Salted bombs create a wide range of strategic options that are not available with nuclear weapons that only produce heat and blast.
Salted bombs would not be easy to use. An attacker would need to know the wind direction over the target and use a salt which produced a fallout that was heavy enough to fall to the ground fairly rapidly, rather the floating off high in the atmosphere.
Salted bombs could have a defensive application. If a country was being invaded by a superior enemy it could use salted bombs to create ‘no go’ areas in front of the attacking troops.