In this report, the mechanism and methods of fixation of acidic waste effluents in grout form are explored. From the variations in the pH as a function of total solids addition to acidic waste effluent solutions, the stages of gellation, liquefaction, slurry formation and grout development are quantitatively revealed. Experimental results indicate the completion of these reaction steps to be significant for elimination of bleed liquid and for setting of the grout to a dimensionally stable and hardened solid within a reasonable period of about twenty eight days that is often observed in the cement and concrete industry. The reactions also suggest increases in the waste loading in the direction of decreasing acid molarity. Consequently, 1.0 molar SBW-180 waste is contained in higher quantity than the 2.8 molar SBW-189, given the same grout formulation for both effluents. The variations in the formulations involving components of slag, cement, waste and neutralizing agent are represented in the form of a ternary formulation map. The map in turn graphically reveals the relations among the various formulations and grout properties, and is useful in predicting the potential directions of waste loading in grouts with suitable properties such as slurry viscosity, Vicat hardness, and mechanical strength. A uniform formulation for the fixation of both SBW-180 and SBW-189 has emerged from the development of the formulation map. The boundaries for the processing regime on this map are 100 wt% cement to 50 wt% cement / 50 wt% slag, with waste loadings ranging from 55 wt% to 68 wt%. Within these compositional bounds all the three waste streams SBW-180, SBW-189 and Scrub solution are amenable to solidification. A large cost advantage is envisaged to stem from savings in labor, processing time, and processing methodology by adopting a uniform formulation concept for fixation of compositionally diverse waste streams. The experimental efforts contained in this report constitute the first attempt at developing a uniform methodology. iv v
EXECUTIVE SUMMARYThe sodium bearing waste (SBW) is an acidic liquid solution of several nitrate components. In view of its acidic nature, one of the aims of the Idaho Completion Project is to have it removed from the storage tanks at Idaho Nuclear Technology and Engineering Center (INTEC), and have it transformed into a disposable solid. Two types of disposable solids are under consideration: grout and silica gel. Commercially available Portland cement, slag and silica gel have been used in the present project for solidifying the three types of waste streams SBW-180, SBW-189 and NWCF Scrub solutions. A large part of this report concentrates on the investigation of the waste fixation in a grout matrix, while preliminary results of waste adsorption onto silica gel are also presented. Neutralizing the waste solutions to a weaker acid is considered important from the point of inhibiting the corrosive effects on cesium ion exchange silico-titanate resins, and for enhancing the retention of wast...
