Evaluation of the Properties of Cemented Liquid Scintillator Wastes under Flooding Scenario in Various Aqueous Media

Experiments simulating flooding scenario in various aqueous media for a long period were carried out to determine the adequacy of cement-clay composite for solidification/stabilization of spent organic radioactive liquid scintillator wastes. The final cement waste form blocks were immersed in three aqueous media, namely, seawater, groundwater, and tapwater. The immersion process lasted for increasing periods up to 540 days. Following each predetermined interval period, physical and mechanical evaluations of the immersed blocks were determined. In addition, the change in the hydration products was followed by X-ray diffraction and infrared spectroscopy as nondestructive analyses to recognize the deterioration in the microstructure that may occur due to the flooding event. Thermal analysis and scanning electron microscopy were performed to confirm the data obtained. 1. Introduction To determine the radioactivity contents in any specimen based on liquid scintillation technique, the sample under quantification is dissolved or suspended in a cocktail containing an aromatic solvent (e.g., benzene, toluene, and dioxan) and predetermined amounts of other additives known as flours, that is, scintillator. The particles emitted from the radioisotope in the sample transfer their energies to the solvent which in turn transfers that energy to the flours’ molecules that dissipating the energy by emitting light. After this quantification, the spent liquid scintillators are counted as a hazardous organic radioactive waste and should be managed safely [1–3]. This waste could be classified as problematic waste for further processing because of the specific radioactive contamination and the organic nature of this waste. Special treatment options should be developed to address both these characteristics of that waste [4]. The practice of immobilizing radioactive waste with ordinary Portland cement began during the early years of the nuclear industry. This was primarily due to its low cost, availability, and compatibility with aqueous waste. It was soon realized, however, that specific wastes, like scintillator liquid, interact with the cement components causing inhibition or retarding the hydration reaction. To overcome these drawbacks, one or more selected additives were added to the Portland cement mixtures. Several of the more successful mixtures such as sodium silicate, reactive silica, lime, clay, and slag have been identified and commercialized [5]. Solidification/stabilization (s/s) using cement is a chemical treatment process aiming at either binding or