Characterization of Solidified Radioactive Waste and Container due to the Incorporation of High Density Polyethylene Gra
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almost twice as much mechanical strength than samples prepared with stone aggregate. Samples prepared with PEHD granules and powder have mechanical strength resistance up to 13.5 percent higher than ones prepared with PEHD granules, solely. Improved Mechanical strength resistance of tested samples accommodates trend that functionally depends on the percentage of PEHD powder added in formulation. INTRODUCTION Using cementation as a technique for immobilizing radioactive waste materials, mortarradioactive waste mixtures were prepared [1,2,3]. After a curing period in appropriate containers, such solidified radioactive waste-mortar monoliths are planned to be placed in an engineered trench system, adopted as a concept for the final disposal of such waste materials. The hardened mortar matrix presents the first barrier to radionuclides release particularly by leaching, either under normal or accident conditions, in prolonged periods of disposal [4,5,6,7,8,9,10]. The solidified waste forms, hardened either in metal drums or in concrete containers would be placed in trench cells, one above the other, up to four in height [11,12]. Good mechanical and physico-chemical properties of the solidified radioactive waste form are important under normal and accident conditions, e.g., earthquake and flooding. In the investigations presented in this paper, one of the goals was to improve mechanical 1261 Mat. Res. Soc. Symp. Proc. Vol. 556 ©1999 Materials Research Society
properties of the final, immobilized radioactive waste material and appropriate container for such waste form. Powder and granules of the high density polyethylene (PEHD) were used to prepare mortar based matrices for immobilization of radioactive waste materials containing Cs-137, as well as containers for solidified radioactive waste form, similar to the preparation of mortar matrices with stone aggregate. PEHD powder and granules were added to mortar matrix preparations with the objective of improving physico-chemical characteristics of the radwastemortar matrix mixtures, in particular the leach-rate of the immobilized radionuclide, as well as mechanical characteristics either of mortar matrix and container. PEHD replaced all of the normally used stone aggregate and part of total cement, in order to decrease porosity and density of the mortar matrix and to avoid the phenomenon of stone aggregate segregation at the bottom of the immobilized radioactive waste cylindric form [13,18]. Satisfying this goal, we tried to obtain better characteristics of the radioactive waste mortar mixture. The experimental work was based on previous investigations on mortar matrices for the immobilization of radioactive waste solutions containing "'Cs. These investigations included addition of high density polyethylene (PEHD) granules to the mortar matrix formulation. The PEHD substituted for the stone aggregate normally used in the mortar matrix formulation [15,16,17,18]. Seven types of matrices, differ in the percentage of granules and filler material added, were investigated. In t
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