Results of tritium monitoring in the environment of the Maišiagala radioactive waste repository

Abstract

A shallow-land radioactive waste storage facility was commisioned in 1963 in an ecologically sensitive locality~ 30 km from Vilnius, Lithuania. To ensure radiation safety, monitoring activities have been performed that take into account the migration of tritium. Tritium analysis in groundwater, soil moisture, and plants indicates obvious leakage from the repository. Liquid scintiliation counting (LSC) involving an ultra low-level device. QuantulusTM (Wallac), is used for tritium measurement. By 2005, there were 8 monitoring boreholes installed in different directions and distances from the vault. In January 2005, 2 new boreholes were installed 0.5 m from the wall of the vault. Soil samples were taken every 0.5 m to a depth of 13.5 m, and tritium was determined in all samples from both boreholes. Maximum activity concentration (100,000 Bq/L) was measured at a depth of 8-8.5 m. Analyses of some LSC spectra revealed possible contamination of groundwater by 137Ca, and this has been confirmed by low-level gamma spectrometry. The storage facility requires continuous monitoring and management in the future.