Real‐time monitoring of crystal accumulation in the high‐level waste glass melters using an electrical conductivity method

• Published in: International journal of applied glass science Vol. 9; no. 1; pp. 42 - 51
• Main Authors: Edwards, Matthew, Matyáš, Josef, Crum, Jarrod
• Format: Journal Article
• Language: English
• Published: Westerville Wiley Subscription Services, Inc 01.01.2018
• Subjects: Accumulation; Aluminum oxide; Cans; Computer simulation; Conductivity; Crystals; electrical conductivity; Electrical resistivity; High level radioactive wastes; high‐level waste glass; Manganese; Melts (crystal growth); Nickel ferrites; Radioactive wastes; Spinel; spinel crystals; Vitrification; Waste treatment
• ISSN: 2041-1286; 2041-1294
• DOI: 10.1111/ijag.12275

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 [Fe, Ni, Mn, Zn]2+[Fe, Cr]23+O4 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 monitor crystal buildup in the melter riser. A vertically configured electrical conductivity (EC) 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. The conductivities of spinel crystals of 20‐24 S/m at 800°C were in excellent agreement with the conductivity of trevorite (NiFe2O4) crystals at 800°C reported in the literature. The conductivities of spinel crystals and measured changes in the conductivity across the accumulated layer allowed for a successful measurement of spinel crystal accumulation in simulated HLW glass.