Cement solidification of simulated off-gas condensates from vitrification of low-level nuclear waste solutions

• Published in: Waste management (Elmsford) Vol. 21; no. 6; pp. 543 - 553
• Main Authors: Katz, A, Brough, A.R, Kirkpatrick, R.J, Struble, L.J, Sun, G.K, Young, J.F
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2001; New York, NY Elsevier Science
• Subjects: Applied sciences; Blast furnace slag; Calorimetry; Cement; Environmental Pollution - prevention & control; Exact sciences and technology; Fly ash; Gases; Grouting; Hydrogen-Ion Concentration; Incineration; Low-level nuclear waste (LLW); Manufactured Materials; NMR; Pollution; Radioactive Waste; Radioactive wastes; Refuse Disposal - methods; Temperature; Wastes; XRD; Fly ash; NMR; Low-level nuclear waste (LLW); Grouting; Cement; Calorimetry; XRD; Blast furnace slag; Property composition relationship; Stabilization; Waste treatment; Vitrification; Liquid waste; Compressive strength; NMR spectrometry; Additive; Silicon 29; Condensates; Hydraulic binder; Mechanical properties; Attapulgite; Portland cement; X ray diffraction; Aluminium 27; Tailings; Solidification; Magic angle; Mineralogical analysis; Inorganic binder; Properties of materials; Thermal analysis; Low level radioactive waste
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/S0956-053X(00)00105-7

Solidification in a cementitious matrix is a viable alternative for low-level nuclear waste management; it is therefore important to understand the behavior and properties of such wasteforms. We have examined the cementitious solidification of simulated off-gas waste streams resulting from the vitrification of low-level nuclear waste. Different possible methods for scrubbing the off-gasses from a vitrifier give rise to three possible types of waste compositions: acidic (from aqueous dissolution of volatile NO x and PO x carried over from the vitrifier), basic (from neutralizing the former with sodium hydroxide), and fully carbonated (arising from a direct-combustion vitrifier). Six binder compositions were tested in which ordinary Portland cement was replaced at different proportions by fly ash and/or ground granulated blast furnace slag. A high solution to binder ratio of 1 l/1 kg was used to minimize the volume of the wasteform and 10% attapulgite clay was added to all mixes to ensure that the fresh mix did not segregate prior to setting. The 28-day compressive strengths decreased when a high proportion of cement was replaced with fly ash, but were increased significantly when the cement was replaced with slag. The heats of hydration at early age for the various solids compositions decreased when cement was replaced with either fly ash or slag; however, for the fly ash mix the low heat was also associated with a significant decrease in compressive strength. High curing temperature (60°C) or the use of extra-fine slag did not significantly affect the compressive strength. Recommendations for choice of binder formulations and treatment of off-gas condensates are discussed.