GEOLOGIC FRAMEWORK MODEL DEVELOPMENT FOR CHARACTERIZING SUBSURFACE ACTINIDE TRANSPORT IN AN ARID ALLUVIAL BASIN ENVIRONMENT - NEGEV DESERT, ISRAEL

Nuclear power has contributed to the reduction of greenhouse gas emissions while maintaining the world’s energy production needs. Compared to conventional power production, the amount of waste produced is relatively small, though nuclear waste presents a unique challenge to safely manage. The deep underground isolation and storage of nuclear waste is a potential solution to this problem but requires rigorous subsurface characterization.

In this project, the subsurface of the Negev desert of Israel is being evaluated as a potential repository site for radioactive waste. The geographic isolation, arid climatic conditions and deep (~500m) water table of the northeast Negev desert point to the existence of a natural barrier to radionuclide migration within a deep vadose zone.

The southern margin of Israel (Levantine margin) records a poly-phase extensional to compressional tectonic history dominated by late Permian to Mesozoic rifting and compression beginning in the late Cretaceous. This tectonic history is responsible for the formation of a series of monoclinal folds and thrust faults along reactivated rift-related normal faults. The subsurface geology of the NE Negev Desert records events associated with compressional syntectonic deposition, uplift and erosion that continued through the late Oligocene and resulted in the closure of the Tethys ocean.

Our study area is located in the Yamin Plain where the vadose zone consists of a stratigraphic succession of Neogene terrestrial alluvial deposits unconformably overlaying a succession of low and high permeability layers of Late Cretaceous shallow marine sediments consisting of bituminous chalks, marls, cherts, phosphorites and limestones. Along with hydrologic measurements and geochemical experiments, a Geologic Framework Model (GFM) of the Yamin Plain Alluvial Basin is being built to facilitate the construction of a computational mesh for flow and transport simulations. Outcrop exposures, wellbore and geophysical data were collected and are integrated in the context of the last 40Ma tectonic history of the region to produce the GFM. Preliminary results will be presented that suggest that the composition, mineralogy and geologic structure of the NE Negev subsurface is conducive to the presence of a natural barrier to radionuclide migration.