One example is the radiological accident occurring in Goiânia, Brazil, between September 1987 and March 1988: Two metal scavengers broke into an abandoned radiotherapy clinic and removed a teletherapy source capsule containing powdered caesium-137 with an activity of 50 TBq.
After two weeks of spread by contact contamination causing an increasing number of adverse health effects, the correct diagnosis of acute radiation sickness was made at a hospital and proper precautions could be put into procedure.
[8] This raises worries of terrorists using powdered alpha emitting material, that if ingested can pose a serious health risk,[9] as in the case of Alexander Litvinenko, who was poisoned by tea with polonium-210.
[11] When United States Attorney General John Ashcroft on June 10, 2002, announced the arrest of José Padilla, allegedly plotting to detonate such a weapon, he said: [A] radioactive "dirty bomb" ... spreads radioactive material that is highly toxic to humans and can cause mass death and injury.This public fear of radiation also plays a big role in why the costs of a radiological dispersal device impact on a major metropolitan area (such as lower Manhattan) might be equal to or even larger than that of the 9/11 attacks.
[8] Assuming the radiation levels are not too high and the area does not need to be abandoned such as the town of Pripyat near the Chernobyl reactor,[12] an expensive and time-consuming cleanup procedure will begin.
Possible radiological dispersal device material could come from the millions of radioactive sources used worldwide in the industry, for medical purposes and in academic applications mainly for research.
[19] There exist thousands of such "orphan" sources scattered throughout the world, but of those reported lost, no more than an estimated 20 percent can be classified as potential high security concerns if used in a radiological dispersal device.
[20] In December 2001, three Georgian woodcutters stumbled over such a power generator and dragged it back to their camp site to use it as a heat source.
Although a terrorist organization might obtain radioactive material through the "black market",[23] and there has been a steady increase in illicit trafficking of radioactive sources from 1996 to 2004, these recorded trafficking incidents mainly refer to rediscovered orphan sources without any sign of criminal activity,[17] and it has been argued that there is no conclusive evidence for such a market.
[25] The first attempt of radiological terror was reportedly carried out in November 1995 by a group of Chechen separatists, who buried a caesium-137 source wrapped in explosives at the Izmaylovsky Park in Moscow.
A Chechen rebel leader alerted the media, the bomb was never activated, and the incident amounted to a mere publicity stunt.
[26][21] In December 1998, a second attempt was announced by the Chechen Security Service, who discovered a container filled with radioactive materials attached to an explosive mine.
The bomb was hidden near a railway line in the suburban area Argun, ten miles east of the Chechen capital of Grozny.
This suspicion was raised by information obtained from an arrested terrorist in U.S. custody, Abu Zubaydah, who under interrogation revealed that the organization was close to constructing a dirty bomb.
[28] It has been doubted whether José Padilla was preparing such an attack, and it has been claimed that the arrest was highly politically motivated, given the pre-9/11 security lapses by the CIA and FBI.
[30] In January 2009, a leaked FBI report described the results of a search of the Maine home of James G. Cummings, a white supremacist who had been shot and killed by his wife.
Investigators found four one-gallon containers of 35 percent hydrogen peroxide, uranium, thorium, lithium metal, aluminium powder, beryllium, boron, black iron oxide and magnesium as well as literature on how to build dirty bombs and information about caesium-137, strontium-90 and cobalt-60, radioactive materials.
[37] Dirty bombs may be prevented by detecting illicit radioactive materials in shipping with tools such as a Radiation Portal Monitor.
[40] Sodium iodide scintillator based aerial radiation detection systems are capable to detect International Atomic Energy Agency (IAEA) defined dangerous quantities of radioactive material [41] and have been deployed by the New York City Police Department (NYPD) Counterterrorism Bureau.
[42] The IAEA recommends certain devices be used in tandem at country borders to prevent transfer of radioactive materials, and thus the building of dirty bombs.
The IAEA also defines the following types of instruments:[43] Legislative and regulatory actions can also be used to prevent access to materials needed to create a dirty bomb.
Thus, they tended to disperse large amounts of unused fissile material, and the fission products, which are on average much more dangerous, in the form of nuclear fallout.
But the Castle Bravo accident of 1954, in which a thermonuclear weapon produced a large amount of fallout that was dispersed among human populations, suggested that this was not what was actually being used in modern thermonuclear weapons, which derive around half of their yield from a final fission stage of the fast fissioning of the uranium tamper of the secondary.