Question

. “The half-life of Ir-192 is 74 days, so complete city blocks may be contaminated for years.” Explain this statement.

Answer 1

Iridium-191 is a radioactive isotope of element Iridium, which emits gamma and beta radiations as it decays. Iridium-192 does not typically occur naturally. Instead, scientists must put iridium-191 in a nuclear reactor and bombard it with neutrons. The iridium-191 then takes up an extra neutron to become iridium-192.

Platinum-coloured, but with a slight yellowish cast

Half-life of Iridium-191 is 73.83 days, because of this value for its half-life, contamination would last years.

Half-life is defined as the time it takes for one half of a radioactive element to decay into a daughter isotope.

Iridium-192 as a category-2 radioactive substance—meaning that 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

Iridium-192 is a dangerous radioactive material. Iridium-192 is an unstable isotope and emits both electrons and gamma-rays (highly energetic packets of light) which later decay into osmium isotopes and platinum isotopes, which are more stable and less dangerous.

Iridium-192 decays to stable platinum-192 or osmium-192 by emitting a beta particle or by electron capture respectively, most of these decays, 95% are by beta emission and the remaining 5% by electron capture.

One nucleus is independent of what other nuclei are doing. After one half-life only half of the original radioactive nuclei are still there and it will take another half-life for half of those to decay, leaving us with a quarter of the initial amount after two half-lives. After three half-lives there will be one-eighth left and so on. So the radiations will never go down to zero if the initial sample is infinitely large.

So complete city blocks might be uninhabitable for years.