Induction Heated Cold Crucible Melter Testing with Troublesome High Level Waste Components

Abstract

Two high level radioactive waste (HLW) surrogate vitrification tests were performed at the Scientific & Industrial Association (SIA) Radon bench-scale plant equipped with the 216 mm inside diameter cold crucible melter that is energized by a 60 kW power high frequency generator operated at a frequency of 1.76 MHz. Savannah River Site HLW surrogates were vitrified and glassy products were obtained. Target compositions of waste surrogates, glass-forming additives and borosilicate glasses were specified by Savannah River National Laboratory (SRNL) personnel according to contract between the US Department of Energy (DOE) and SIA Radon. Vitrification of HLW surrogate with commercially available borosilicate Frit 200 and Frit 320 was performed for ∼90 hours of steady-state conditions. Approximately 680 kg was processed and ∼260 kg of glass was produced. The average slurry feed rate, glass productivity and specific glass pour rate reached 8.5 kg/h, 5.4 kg/h, and ∼2960 kg/(m 2 ·day), respectively. Process temperature (measured on melt surface) ranged between 1200-1350 °C (melting) and ∼700 °C (slurry feeding). Glass was homogeneous with only a minor magnetite-type crystalline phase with the spinel structure. The cold crucible demonstrated high resistance to molten glass corrosion. Traces of corrosion were observed on the surface of the cold crucible pipes that came in contact with molten glass at the pouring level. The glasses demonstrated low B, Li, Na, and Si release as measured by the Product Consistency Test (PCT) leaching procedure. Infrared (IR) spectroscopic data indicated the glass network is formed by silicon-oxygen and boron-oxygen tetrahedra. The latter are capable to link alkali ions reducing their leaching.