Assessment of the Safe Isolation of Solid Radwaste in Subsurface Repositories

Resumo

A calculation of the removal of radionuclides by groundwaters from a subsurface repository of solid low-level waste was performed. A two-dimensional model of the groundwater flow and advective-dispersive transport of radionuclides in a vertical section of a subsurface aquifer, along which radionuclide-contaminated groundwater moves from the repository to an open body of water, was studied. Data from many years of experimentation on the leaching of cemented low-level waste were used in the calculations. It was shown that the rocks of the aquifer effectively retain medium half-life radionuclides (⁶⁰Co, ¹³⁷Cs, ⁹⁰Sr). An engineered barrier – a 0.7 m thick layer of consolidated bentonite clay – can secure the safety of a repository for long-lived transuranium radionuclides (²³⁵U, ²³⁹Pu) for 20000 years.