Cobalt bomb
Encyclopedia
A cobalt bomb is a theoretical type of "salted bomb
": a nuclear weapon
intended to contaminate an area by radioactive material, with a relatively small blast
.
The weapon's tamper would be composed of ordinary cobalt
metal, which the nuclear explosion would then transmute
to the radioactive isotope cobalt-60
(60Co), which would produce deadly nuclear fallout
.
As far as is publicly known, no cobalt bombs were ever built. The Operation Antler/Round 1 test by the British at the Tadje site in the Maralinga range
in Australia on 14 September 1957 tested a bomb using cobalt as a radiochemical tracer, but was considered a failure.
. 60Co decays into an excited 60Ni by beta decay
. The excited 60Ni then transitions to a ground state
60Ni, releasing gamma radiation.
The concept of a cobalt bomb was originally described by physicist Leó Szilárd
, who suggested that an arsenal of cobalt bombs would be capable of destroying all human life on Earth (though his conclusions are disputed). Cobalt was chosen because of the fallout
, that would have a half-life
of 5.27 years and would be intensely radioactive at the same time. While there exist isotopes with a longer half-life than 60Co, they are also insufficiently radioactive. Many isotopes are more radioactive (gold-198, tantalum-182, zinc-65, sodium-24, and many more), but they would decay faster, possibly allowing some population to survive in shelter
s.
To provide a point of reference: to equally distribute 1 gram of cobalt per square kilometer of Earths surface one would need 510 tonnes, and fallout does not reach all areas in equal amounts. While the sheer size and cost of such a weapon makes it unlikely to be built, it is technically possible because there is no maximum size limit for a thermonuclear bomb.
However, the effects of nuclear weapons, including blast, physical damage and fallout, do not scale up linearly with weapon size or yield; the magnitude of these effects increases more gradually than the energy released by the nuclear detonation. Stratospheric scientist and Australian peace activist Brian Martin has published analyses demonstrating this crucial weakness in the idea that the planetary nuclear arsenal is several times as large as that required to destroy all life on Earth; this analysis would have implications for the real versus the assumed lethality of the cobalt bomb to all life on Earth.
Salted bomb
A salted bomb is a variation of a nuclear weapon designed to produce enhanced quantities of radioactive fallout, rendering a large area uninhabitable...
": a nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
intended to contaminate an area by radioactive material, with a relatively small blast
Blast
Blast or The Blast may refer to:*Explosion, a rapid increase in volume and release of energy in an extreme manner*Detonation, an exothermic front accelerating through a medium that eventually drives a shock front-Film:...
.
The weapon's tamper would be composed of ordinary cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
metal, which the nuclear explosion would then transmute
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...
to the radioactive isotope cobalt-60
Cobalt-60
Cobalt-60, , is a synthetic radioactive isotope of cobalt. Due to its half-life of 5.27 years, is not found in nature. It is produced artificially by neutron activation of . decays by beta decay to the stable isotope nickel-60...
(60Co), which would produce deadly nuclear fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
.
As far as is publicly known, no cobalt bombs were ever built. The Operation Antler/Round 1 test by the British at the Tadje site in the Maralinga range
British nuclear tests at Maralinga
British nuclear tests at Maralinga occurred between 1955 and 1963 at the Maralinga site, part of the Woomera Prohibited Area, in South Australia. A total of seven major nuclear tests were performed, with approximate yields ranging from 1 to 27 kilotons of TNT equivalent...
in Australia on 14 September 1957 tested a bomb using cobalt as a radiochemical tracer, but was considered a failure.
Mechanism
The cobalt tamper would be transmuted into the isotope 60Co upon initiation and bombardment by neutron radiationNeutron radiation
Neutron radiation is a kind of ionizing radiation which consists of free neutrons. A result of nuclear fission or nuclear fusion, it consists of the release of free neutrons from atoms, and these free neutrons react with nuclei of other atoms to form new isotopes, which, in turn, may produce...
. 60Co decays into an excited 60Ni by beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
. The excited 60Ni then transitions to a ground state
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...
60Ni, releasing gamma radiation.
The concept of a cobalt bomb was originally described by physicist Leó Szilárd
Leó Szilárd
Leó Szilárd was an Austro-Hungarian physicist and inventor who conceived the nuclear chain reaction in 1933, patented the idea of a nuclear reactor with Enrico Fermi, and in late 1939 wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project that built the atomic bomb...
, who suggested that an arsenal of cobalt bombs would be capable of destroying all human life on Earth (though his conclusions are disputed). Cobalt was chosen because of the fallout
Fallout
Fallout or nuclear fallout is the residual radiation hazard from a nuclear explosion.Fallout may also refer to:*Fallout , a 1997 post-apocalyptic computer role-playing game released by Interplay Entertainment...
, that would have a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 5.27 years and would be intensely radioactive at the same time. While there exist isotopes with a longer half-life than 60Co, they are also insufficiently radioactive. Many isotopes are more radioactive (gold-198, tantalum-182, zinc-65, sodium-24, and many more), but they would decay faster, possibly allowing some population to survive in shelter
Bomb shelter
A bomb shelter is any kind of a civil defense structure designed to provide protection against the effects of a bomb.-Types of shelter:Different kinds of bomb shelters are configured to protect against different kinds of attack and strengths of hostile explosives. For example, an Air-raid shelter...
s.
To provide a point of reference: to equally distribute 1 gram of cobalt per square kilometer of Earths surface one would need 510 tonnes, and fallout does not reach all areas in equal amounts. While the sheer size and cost of such a weapon makes it unlikely to be built, it is technically possible because there is no maximum size limit for a thermonuclear bomb.
However, the effects of nuclear weapons, including blast, physical damage and fallout, do not scale up linearly with weapon size or yield; the magnitude of these effects increases more gradually than the energy released by the nuclear detonation. Stratospheric scientist and Australian peace activist Brian Martin has published analyses demonstrating this crucial weakness in the idea that the planetary nuclear arsenal is several times as large as that required to destroy all life on Earth; this analysis would have implications for the real versus the assumed lethality of the cobalt bomb to all life on Earth.