Waste form development/test: polyethylene and modified sulfur cement solidification of LLW

Low-density polyethylene and a modified sulfur cement have been selected for further study as new potential solidification agents for LLW streams including dry evaporator concentrates, incinerator ash and ion exchange resins. These binder materials are thermoplastic and are processed by use of a screw-type extruder or an air-powered dual action mixer. The studies have utilized ''bench scale'' systems with sufficient capacity to enable reliable determination of the effects of processing parameters such as temperature requirements, feed rates, mixing methods, waste pretreatment and solidification kinetics. Maximum waste loadings have been obtained for polyethylene by use of the screw extruder under controlled conditions. The modified sulfur cement system is processed more effectively by the dual action mixer due to its very low melt viscosity. Simulated waste forms produced using acceptable formulations, are being tested to develop a data base of relevant waste form properties. Several tests underway include immersion, leaching, compressive strength and thermal stability