Steam reforming as a method to treat Hanford underground storage tank (UST) wastes

Abstract

This report summarizes a Sandia program that included partnerships with Lawrence Livermore National Laboratory and Synthetica Technologies, Inc. to design and test a steam reforming system for treating Hanford underground storage tank (UST) wastes. The benefits of steam reforming the wastes include the resolution of tank safety issues and improved radionuclide separations. Steam reforming destroys organic materials by first gasifying, then reacting them with high temperature steam. Tests indicate that up to 99% of the organics could be removed from the UST wastes by steam exposure. In addition, it was shown that nitrates in the wastes could be destroyed by steam exposure if they were first distributed as a thin layer on a surface. High purity alumina and nickel alloys were shown to be good candidates for materials to be used in the severe environment associated with steam reforming the highly alkaline, high nitrate content wastes. Work was performed on designing, building, and demonstrating components of a 0.5 gallon per minute (gpm) system suitable for radioactive waste treatment. Scale-up of the unit to 20 gpm was also considered and is feasible. Finally, process demonstrations conducted on non-radioactive waste surrogates were carried out, including a successful demonstration of the technology at the 0.1 gpm scale.