![]() However, the body doesn't normally use iridium for biological processes, so such damage is less likely than with other radioactive substances, such as radioactive iodine, Rosner added. Longer-term damage, such as cancer, would occur only if the cells in the body absorbed the radioactive material, which would then continue to emit DNA-damaging gamma-rays over a long period, Rosner said. However, that acute form of radiation sickness would mainly occur if someone were to open up the case or hold the unshielded capsules in his or her hands. "You actually get irradiation burns, tissue damage and necrosis ," Rosner said. The high-energy gamma-rays do their damage directly in the short term. This means the substance can permanently injure a person who handles the radioactive material for minutes to hours, and it can kill people in close proximity within hours to days, according to the agency. The International Atomic Energy Agency defines iridium-192 as a category-2 radioactive substance. The half-life of iridium-192 is about 74 days, meaning that in that space of time, half of the material will have decayed to more stable forms, Rosner said. ![]() However, the iridium-192 is unstable and emits electrons and gamma-rays (highly energetic packets of light) to decay into osmium isotopes and platinum isotopes. The iridium-191 then takes up an extra neutron to become iridium-192. Instead, scientists must put iridium-191 in a nuclear reactor and bombard it with neutrons. Iridium-192 does not typically occur naturally. Iridium-192 is a radioactive isotope, meaning it's a version of iridium with a different number of neutrons than is contained in the dominant forms of the element. It is often recovered as a byproduct of nickel mining, and is used in electrical connections and to harden platinum. Iridium is the 77th element on the periodic table, and is a very dense, platinumlike metal that is highly resistant to corrosion. "But you can scare the bejesus out of people." ![]() ![]() Based on reports of what was allegedly stolen, "you will not make a dirty bomb that has much of an actual health risk, because there's so little material," said Robert Rosner, former director of Argonne National Laboratory and a professor of physics and astronomy at the University of Chicago. ![]()
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