Hot Particles in the Floodplain of the Yenisei River

Abstract

The purpose of this study was to investigate radionuclide composition of the hot particles found in the floodplain of the Yenisei River and to discuss their possible sources. Since 1995, researchers of the Institute of Biophysics have found a considerable number of hot particles that contain up to 29,000 kBq/particle of ¹³⁷Cs in the Yenisei River floodplain. Investigations of the particles in Krasnoyarsk, Moscow, and Novosibirsk have confirmed their reactor origin and made it possible to roughly estimate their age. Based on comparative analysis of ¹³⁷Cs/¹³⁴Cs ratios, all the particles can be divided into two or three major groups, suggesting that over the 50-year period of the MCC operation, there have been two or three emergency situations at the MCC reactors, with nuclear fuel microparticles released into the Yenisei. Microparticles containing up to 36 Bq/particle of ²⁴¹Am were detected in soil and sediment samples collected at the Yenisei River. In some of these particles the ¹³⁷Cs/²⁴¹Am ratio is high but in the others — low. It remains unknown how these particles have been formed. However, these microparticles occur in floodplain soils and sediments very frequently and, thus, can be considered to be the main form in which radionuclides are present in the Yenisei River floodplain. The presence of a large number of hot particles of different origin in the floodplain of the Yenisei River from the MCC production area down to the town of Yeniseisk (and, probably, farther downstream) is a source of potential health hazard to people.