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A radiological weapon or radiological dispersion device (RDD) is any weapon that is designed to spread radioactive material with the intent to kill, and cause disruption upon a city or nation.
It is primarily known as a dirty bomb or salted bomb because it is not a true nuclear weapon and does not yield the same explosive power. It uses conventional explosives to spread radioactive material, most commonly the spent fuels from nuclear power plants or radioactive medical waste.
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Radiological weapons have been suggested as a possible weapon of terrorism used to create panic and casualties in densely populated areas. They could also render a great deal of property useless for an extended period, unless costly remediation were undertaken. The radiological source and quality greatly impacts the effectiveness of a radiological weapon.
Factors such as: energy and type of radiation, half-life, longevity, availability, shielding, portability, and the role of the environment will determine the effect of the radiological weapon. Radioisotopes that pose the greatest security risk include: 137
Cs, used in radiological medical equipment, 60
Co, 241
Am, 252
Cf, 192
Ir, 238
Pu, 90
Sr, and 226
Ra.
All of these isotopes, except for the latter, are created in nuclear power plants. While the amount of radiation dispersed from the event will likely be minimal, the fact of any radiation may be enough to cause panic and disruption.
The professional history of radioactive weaponry may be traced to a 1943 memo from James Bryant Conant, Arthur Holly Compton, and Harold Urey, to Brigadier General Leslie Groves of the Manhattan Project and to a 1940 science fiction story, "Solution Unsatisfactory"[1] by Lt. J. G. Robert A. Heinlein, USN(R). Transmitting a report entitled, "Use of Radioactive Materials as a Military Weapon," the Groves memo states:
As a gas warfare instrument the material would ... be inhaled by personnel. The amount necessary to cause death to a person inhaling the material is extremely small. It has been estimated that one millionth of a gram accumulating in a person's body would be fatal. There are no known methods of treatment for such a casualty.... It cannot be detected by the senses; It can be distributed in a dust or smoke form so finely powdered that it will permeate a standard gas mask filter in quantities large enough to be extremely damaging....Radioactive warfare can be used [...] To make evacuated areas uninhabitable; To contaminate small critical areas such as rail-road yards and airports; As a radioactive poison gas to create casualties among troops; Against large cities, to promote panic, and create casualties among civilian populations.
Areas so contaminated by radioactive dusts and smokes, would be dangerous as long as a high enough concentration of material could be maintained.... they can be stirred up as a fine dust from the terrain by winds, movement of vehicles or troops, etc., and would remain a potential hazard for a long time.
These materials may also be so disposed as to be taken into the body by ingestion instead of inhalation. Reservoirs or wells would be contaminated or food poisoned with an effect similar to that resulting from inhalation of dust or smoke. Four days production could contaminate a million gallons of water to an extent that a quart drunk in one day would probably result in complete incapacitation or death in about a month's time.
The United States, however, chose not to pursue radiological weapons during World War II, though early on in the project considered it as a backup plan in case nuclear fission proved impossible to tame. Some US policymakers and scientists involved in the project felt that radiological weapons would qualify as chemical weapons and thus violate international law.
One possible way of dispersing the material is by using a dirty bomb, a conventional explosive which disperses radioactive material. Dirty bombs are not a type of nuclear weapon, which requires a nuclear chain reaction and the creation of a critical mass. Whereas a nuclear weapon will usually create mass casualties immediately following the blast, a dirty bomb scenario would initially cause only minimal casualties from the conventional explosion.
Means of radiological warfare that do not rely on any specific weapon, but rather on spreading radioactive contamination via a food chain or water table, seem to be more effective in some ways, but share many of the same problems as chemical warfare.
Radiological weapons are widely considered to be militarily useless for a state-sponsored army and are initially not hoped to be used by any military forces. Firstly, the use of such a weapon is of no use to an occupying force, as the target area becomes uninhabitable (due to the fallout caused by radioactive poisoning of the involved environment).
Furthermore, area-denial weapons are generally of limited use to an attacking army, as it slows the rate of advance.
A dirty bomb is a radiological weapon dispersed with conventional explosives.
There is currently (as of 2007) an ongoing debate about the damage that terrorists using such a weapon might inflict. Many experts believe that a dirty bomb such that terrorists might reasonably be able to construct would be unlikely to harm more than a few people and hence it would be no more deadly than a conventional bomb. Furthermore, the casualties would be a result of the initial explosion, because alpha and beta emitting material needs to be inhaled to do damage to the human body. Gamma radiation emitting material is so radioactive that it can't be deployed without wrapping an amount of shielding material around the bomb that would make transport by car or plane impossible without risking detection. Because of this a dirty bomb with radioactive material around an explosive device would be almost useless, unless said shielding was removed shortly before detonation. This is not only because of the effectiveness but also because this material would be easy to clean up. Furthermore, the possibility of terrorists making a gas or aerosol that is radioactive is very unlikely because of the complex chemical work to achieve this goal.[2]
Hence, this line of argument goes, the objectively dominant effect would be the moral and economic damage due to the massive fear and panic such an incident would spur. On the other hand, some believe that the fatalities and injuries might be in fact much more severe. This point was made by physicist Peter D. Zimmerman (King's College London) who reexamined the Goiânia accident which is arguably comparable.[3] and popularized in a subsequent fictionalized account produced by the BBC and broadcast in the United States by PBS.[4] The latter program showed how shielding might be used to minimize the detection risk.
A salted bomb is a variation of a nuclear weapon designed to produce large quantities of radioactive fallout, rendering a large area uninhabitable.[5] The term is derived both from the means of their manufacture, which involves the incorporation of additional elements to a standard atomic weapon, and from the expression "to salt the earth", meaning to render an area uninhabitable for generations. The idea originated with Hungarian-American physicist Leo Szilard, in February 1950. His intent was not to propose that such a weapon be built, but to show that nuclear weapon technology would soon reach the point where it could end human life on Earth.[5][6]
Salted versions of both fission and fusion weapons can be made, by a change in the materials used in their construction. The idea is to increase the normal production of radioactive fallout by placing inside the weapon a quantity of an element that can be converted to a highly radioactive isotope by neutron bombardment.[5] When the bomb explodes, the element absorbs neutrons released by the nuclear reaction, and is converted to its radioactive form. The explosion and mushroom cloud scatters the radioactive material over a wide area, leaving the targeted area highly radioactive, and uninhabitable to humans far longer than an area affected by typical nuclear weapons.
In a salted hydrogen bomb, the radiation case around the fusion fuel, which normally is made of some fissionable element, is replaced with a metallic salting element. Salted fission bombs can be made by replacing the tamper between the fissionable core and the explosive layer with a metallic element. The energy yield from a salted weapon is usually lower than from an ordinary weapon of similar size as a consequence of these changes.
The radioactive isotope chosen for the fallout material is usually a high intensity gamma ray emitter, with a half-life long enough that it remains lethal for an extended period. It also must have a chemistry that causes it to return to earth as fallout, rather than stay in the atmosphere after being vaporized in the explosion.
One example of a salted bomb is a proposed cobalt bomb, which uses the radioactive isotope cobalt-60 (60Co). Other non-fissionable isotopes can be used, including gold-198 (198Au), tantalum-182 (182Ta) and zinc-65 (65Zn).[6]
No salted bomb has ever been atmospherically tested and as far as is publicly known none have ever been built.[5] The United Kingdom did test a 1 kiloton bomb incorporating a small amount of cobalt as an experimental radiochemical tracer at their Tadje testing site in Maralinga range, Australia on September 14, 1957.