Maria Gheorghe

Leaching Tests of the Tritium Waste Immobilized in New Cement Mixtures

Abstract The study was conducted in order to determine the immobilization performance of low-level tritium waste in new cement mixtures. The grouts analyzed are fine mortars, fluid, self- compacting, with flowability, able to fill the smallest gaps in the solid waste container. The grouts curing showed compact and structural integrity without pores and cracks, so as to ensure radioactive tritium waste encapsulation. Two types of solid/liquid tritium radioactive waste with known tritium activity have been prepared: one type containing a hydrophilic tritium compound and the other one a hydrophobic tritium compound. The tritium waste was mixed with three different types of grout and poured in a cylindrical mould. The leaching of tritium from waste solidified/encapsulated in the cement mixtures immersed in an aqueous environment has been studied in order to select the most appropriate grout type as waste immobilization matrix. Samples from the liquid surrounding the cements blocks were collected at predetermined time intervals and placed in the liquid scintillation cocktail and measured. The activity of the tritium released was then calculated.

Practical Model of Cement Based Grout Mix Design, for Use into Low Level Radiation Waste Management

Abstract The cement based grouts, as functional performance composite materials, are widely used for both immobilisation and encapsulation as well as for stabilization in the field of inorganic waste management. Also, to ensure that low level radioactive waste (LLW) are contained for storage and ultimate disposal, they are encapsulated or immobilized in monolithic waste forms, with cement –based grouts. The paper includes some research data referring to cement based grout mix design for use as encapsulating/immobilizing system for low level radioactive waste. The work includes cement-based-grout mix design method used practically into establishing of the optimum grout mix based on the water/cement ratio, cement/sand ratio in order to achieve application requiered values of fluidity, segregation resistance, shrinkage and mechanical strengths. These engineering grout characteristics present relevance for simulation experiments of radionuclide leaching from LLW – cement grout encapsulation system.

MINERAL WASTES USED IN ADVANCED COMPOSITE MATERIALS FOR LOW LEVEL WASTE IMMOBILISATION

The common way for low level waste (LLW) immobilization are using of composite cement systems, due to inexpensive, readily available and effective shielding and encapsulating properties. Composite cement system such as concrete contains various materials with different densities as aggregates (about 75-80% of total volume) which play an important role in development of properties. The possible use of mineral wastes in composite cement systems may also improve the shielding performance of material. In this article, authors present some reliable options to replace natural aggregates by mineral wastes. These ultimate wastes namely lead slag, cathode ray tube glass, and fly ash need itself a disposal route. Each of these is compatible with LLW encapsulation process due to its chemical composition and pozzolanic activity.