The Role of Physical Parameters on the Overflow Probability of a Radioactive Near Surface Repository for Low & Intermediate Level Wastes: The Case of Abadia de Goiás

In an earlier work, a model has been developed for evaluating the overflow probability of the radioactive waste near surface repository of Abadia de Goiás, Brazil for safety and licensing purposes. Water infiltration inside the repository is influenced by a set of design and physical parameters. However, an analysis on the variability of these parameters has not yet been performed. This paper discusses the variability of each of these parameters and possible dependencies among them and also time dependencies. This analysis is important for a future sensitivity analysis concerning the overflow probability. It is simpler to analyze the influence of those parameters that are not rates, e.g., the repository internal base area, because an eventual shape variability does not bring any difficulty since it is just a matter of varying the shape and dimensions. Some parameters, like the internal porosity of the repository are dimensionless. The analysis of rate parameters, like the rainfall rate, is more complicated and dependencies have been detected. If one considers that the rainfall rate is the highest available, the overflow probability might be as high as 99%, as estimated in the mentioned earlier work. In this sense, a realistic sensitivity analysis on the overflow probability is due so that the most influential parameters can be identified and design and operational modifications on the safety side implemented.

Keywords: Radioactive waste repository, Rainfall rate, Evapotranspiration rate, Porosity, Degradation, Water infiltration, Overflow probability.

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