Europium

For more than 40 years, weapons-grade plutonium was manufactured by the Krasnoyarsk Mining and Chemical Combine in the now closed town of Krasnoyarsk Krai, Russia, using single-pass uranium-graphite production reactors [447]. Water from the Yenisei River was used for heat removal from the reactor core. Radioactively contaminated water was discharged into the Yenisei River and was a primary source of contamination of bottom sediments and floodland for hundreds of kilometers down gradient from the Krasnoyarsk Mining and Chemical Combine. In 2002, radioactive contamination of the bottom sediments and floodlands was composed primarily of ¹³⁷Cs, ¹⁵²Eu, ¹⁵⁴Eu, and ⁶⁰Co [447]. The decrease in the isotope-amount ratio n(¹⁵⁴Eu)/n(¹⁵²Eu) down the depth profiles (Fig. IUPAC.63.1) enables one to determine the age of bottom sediments and floodlands of the Yenisei River and calculate their average formation rates [447].

Europium isotopes have been used in nuclear-control applications because they are good neutron absorbers [448]. ¹⁵²Eu (with a half-life of 13.5 years), which is produced by ¹⁵¹Eu via the neutron capture reaction ¹⁵¹Eu (n, γ) ¹⁵²Eu, and ¹⁵⁴Eu (with a half-life of 8.59 years) are used as reference sources for calibration in gamma ray spectroscopy (Fig. IUPAC.63.2) [449].