Model Assessment of the Migration Capability of Transuranium Radionuclides (Am-241 and Pu Isotopes) and Eu-152 in the System Bottom Sediments-Yenisei River Water by Chemical Fractionation Technique

Sorption of radiotracers Am-241 and Pu-242 and weighable amounts of uranium and stable Eu on bottom sediments in the simulated system bottom sediments-Yenisei river water was studied. At a contact time of 40 min these metals are completely sorbed on the bottom sediments, presumably via association with organomineral complexes and hydrated gels. Along with sorption, these metals can form soluble complexes and stable colloids (pseudocolloids). The distribution factors of Am-241 and Pu-242, and stable Eu in the simulated system between bottom sediments and liquid phases were calculated from the results of sorption experiments. The introduced Am-241 and Eu-152 initially present in radioactively contaminated bottom sediments of the Yenisei river show similar pattern of distribution over differently mobile fractions. The distribution of weighable amounts of stable Eu significantly differs from that of initially present Eu-152 and tracer Am-241 due to decelerated sorption of stable Eu and its considerably higher concentration. A significant part of Pu-242, Am-241, and Eu-152 is associated with mobile fractions of bottom sediments, which, under certain environmental conditions, can pass into river water as migrating species.