Erosion in the Yamin Plain – A Major Concern for Near Surface Radioactive Waste Disposal Facilities - The 29th Conference of the Nuclear Societies in Israel

The national site for radioactive waste disposal in near surface mode is located in the Yamin Plain (YP), north-east Negev Desert, Israel. Reducing dispersion of radioactive material from these waste facilities to the environment, especially after the institutional control period (ICP), is a major concern NRCN is responsible for. Since the YP is composed of sandy soil, under the current climate, erosion during flow events and extreme floods is the dominant process governing the landscape in the region and therefore an important issue for near surface disposal. In this work we review qualitative and quantitative methodologies which have been applied over the past years in the attempt to understand the Fluvial and Aeolian erosion processes in the plain: biological soil crusts (BSC); geomorphic mapping based on aerial photographs and satellite imaging; wind tunnel; optical stimulation luminescence (OSL), ¹⁰Be cosmogenic isotope; and Kineros2 modelling of runoff and erosion.

After the YP was closed, grazing in the area was eliminated, resulting in BSC and vegetation development and sand dune stabilization. The BSC in the YP were investigated in manner of microbial composition and its effect on fluvial erosion using runoff plot experiments. These showed the increase in runoff in plots with BSC in comparison to those without. Wind tunnel experiments over un-disturbed and disturbed plots showed that aeolian erosion is negligible.

The drastic effects of erosion in the YP were initially identified through geomorphic mapping of aerial and satellite images, in which drastic changes in channel width before and after flow events were identified. Two quantitative methods were then applied for erosion rates in the YP: OSL and the ¹⁰Be cosmogenic isotope. Sand samples along channel terraces in the E`fe sub-basin (northwest area of YP), were analyzed for OSL, revealing that in the last 14,000 yr an erosion rate of 0.5 mm/yr existed. On the other hand, ¹⁰Be cosmogenic isotope analysis of sand and chart pebbles in the E`fe and Yamin sub-basins gave an average erosion rate of 0.0176±1.13 mm/yr in the last ~200 ky. This order of a magnitude difference requires further investigation while using additional tools. Finally, the preliminary calibration of the Kineros2 model with four flow events was done. The calibration of this model to the YP is necessary for future assessments of erosion rates.

From all these studies it is clear that erosion in the YP is a major process and a primary concern for the waste sites. Proper understanding of the erosion potential, in the different sub-basins of the YP, under the current and future climate regime is critical in the planning of these facilities. In parallel, research to upgrade the cover layer of these facilities with new materials, is also being done.