Isotopes of ruthenium

Naturally occurring ruthenium is composed of seven stable isotopes: 96, 98-102, 104. Additionally, 27 synthetic radioactive isotopes have been discovered. Of these radioisotopes, the most stable are ¹⁰⁶Ru with a half-life of 371.8 days or 1.018 years, ¹⁰³Ru, with a half-life of 39.245 days, and ⁹⁷Ru with a half-life of 2.837 days.
The other known isotopes run from ⁸⁷Ru to ¹²⁰Ru, and most of these have half-lives that are less than five minutes, except ⁹⁴Ru, ⁹⁵Ru, and ¹⁰⁵Ru.
The primary decay mode before the most abundant isotope, ¹⁰²Ru, is electron capture to isotopes of technetium, and after beta emission to isotopes of rhodium. Double beta decay is the allowed mode for the two observationally stable isotopes: ⁹⁶Ru and ¹⁰⁴Ru.
Because of the volatility of ruthenium tetroxide, ruthenium isotopes with relatively short half-life are considered the next most hazardous airborne isotopes, after iodine-131, in case of release by a nuclear accident. The two most important isotopes of ruthenium so released are those with the longest half-life: ¹⁰³Ru ¹⁰⁶Ru.

List of isotopes

Alleged ruthenium-106 leak

In September 2017 an estimated amount of 100 to 300 TBq of ¹⁰⁶Ru was released in Russia, probably in the Ural region. It was, after ruling out release from a reentering satellite, concluded that the source was either in nuclear fuel cycle facilities or radioactive source production. In France levels up to 0.036mBq/m³ of air were measured. It was estimated that for distances of the order of a few tens of kilometres, contamination levels may have exceeded the limits for non-dairy foodstuffs.

Asteroid that ended the Cretaceous period

The ratios of the amounts of ruthenium isotopes were used to determine the age of the asteroid which exterminated the dinosaurs at the end of the Cretaceous period, and to show that it originated beyond Jupiter in the outer solar system.