Radiological weapon

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 because it is not a true nuclear weapon and does not yield the same destructive power. It uses conventional explosives to spread radioactive material, most commonly the spent fuels from nuclear power plants or radioactive medical waste.

Explanation
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 was undertaken. The radiological source and quality greatly impacts the effectiveness of a radiological weapon.

Factors such as: energy and type of radiation, half-life, size of explosion, 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: 137Cs, used in radiological medical equipment, 60Co, 241Am, 252Cf, 192Ir, 238Pu, 90Sr, and 226Ra. 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.

History
The history of radioactive weaponry may be traced to a 1943 memo to Brigadier General Leslie Groves of the Manhattan Project. Transmitting a report entitled, "Use of Radioactive Materials as a Military Weapon," the 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.

Deployment
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.

Military uses
Radiological weapons are widely considered to be militarily useless for a state-sponsored army and are not believed to have been deployed 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. Furthermore, area-denial weapons are generally of limited use to an attacking army, as it slows the rate of advance. Finally, like biological weapons, radiological weapons can take days to act on the opposing force. They therefore not only fail in neutralizing the opposing force instantly, but they also allow time for massive retaliation.

Iraq
Iraq under Saddam Hussein is reported to have tested a radiological weapon in 1987 for use against Iran. This weapon was found to be impractical because the radioactive isotopes in the weapon would decay quickly, rendering it useless within a week after the weapon was manufactured. Furthermore, it was found that for the radioactive material to spread, weather conditions had to be ideal. These problems are in general shared by all forms of air-borne radiological warfare.

Damage assessment
There is currently (as of 2007) an ongoing debate about the damage that terrorists using such a weapon might inflict. Many experts believe that such a bomb would be unlikely to harm more than a few people and hence it would be no more deadly than a conventional bomb. 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 is, e.g., made by physicists Peter D Zimmerman et al. (King's College London) who reexamined the Goiânia accident which is arguably comparable. (Ref.: Nature Science Update of 5 May 2004)