Real-Time Monitoring Of Crystal Accumulation In The High-Level Waste Glass Melters Using An Electrical Conductivity Method

During the vitrification of high-level radioactive waste (HLW) in HLW melters in the Waste Treatment and Immobilization Plant located in Washington State, spinel crystals may precipitate from glass and accumulate in the melter riser, preventing the discharge of molten glass into canisters. Therefore, an effort is being made to develop an electrical conductivity method to monitory crystal buildup in the melter riser. A vertically configured electrical conductivity probe with an alumina shaft and Pt-10%Rh-electrodes was designed and tested in standard conductivity solutions and glass melts both with and without spinel crystals. The EC probe measured conductivity in conductivity solutions within 10% of their certified values and showed a linear relationship with increased spinel layer thicknesses. Testing in silicate glass containing spinel crystals allowed for the determination of spinel conductivity as a function of temperature.