Modeling of nuclide releases from perforated radioactive paraffin waste containers

An effect of a pinhole (perforation or pit penetration) that can be formed on the surface of a waste container on the nuclide release is studied. The more realistic pinhole release model is developed from the diffusion-controlled dissolution reaction in consideration of the receding hemispherical concentration front around the pinhole and the relation of the nuclide concentration with its solubility. Except for an initial period, the pinhole release rates rapidly approach to the zero-order kinetics. The steady-state release rates are directly proportional to the diffusion coefficient of the nuclide, the nuclide concentration or the solubility depending on the sub- or super-saturated loading, and the radius of the pinhole not to its area. The predicted results of this theoretical model agree well with experimental results using the leaching test of the paraffin waste form.