Impact of Particle Agglomeration on Accumulation Rates in the Glass Discharge Riser of HLW Melter

Abstract

The major factor limiting waste loading in continuous high-level radioactive waste (HL W) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with xray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, and on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185±155 11m, and produced >3 mm thick layer after 120 h at 850°C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.

The Effects of Glass Doping, Temperature and Time on the Morphology, Composition, and Iron Redox of Spinel Crystals

“…The remaining four samples (numbers in bold letters in the Table 3) showed higher but still acceptable RSD in the range from 6 to 10%. 3 . Consistent results were obtained for the standard FAS sample.…”

“…1 The major factor limiting waste loading in Hanford high-level waste (HLW) glasses is the precipitation, growth, and subsequent accumulation of spinel crystals [Fe, Ni, Mn, Zn, Sn][Fe, Cr] 2 O 4 in the glass discharge riser of the melter during idling. 2,3 These crystals can reach a size of a few hundreds of micrometers and because of their high density (~5.3 × 10 3 kg/m 3 ) settle down fast, forming a thick sludge layer that prevents the discharge of the molten glass into stainless steel canisters.…”

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

“…This synthesis approach allowed production of a sodium silicate powder with a minimal tendency for foaming during melting. High‐Ni‐Fe glass (Ni1.5/Fe17.5) was used as a simulant of HLW glass for laboratory testing of the probe function. A simulated HLW glass, high‐Ni‐Fe glass, was produced from Hanford waste tank 241‐AZ‐101 simulant described by Hrma et al where additional Ni and Fe were added as oxides (Fe 2 O 3 , NiO).…”

Road Map for Development of Crystal-Tolerant High Level Waste Glasses

“…A significant amount of crystal settling data has been generated in recent studies. [8][9][10][11][12][13][14] However, there is literature available on the settling behavior of crystals as observed in research-, pilot-, and full-scale melter tests that needs to be reviewed and summarized. A thorough literature review will include descriptions of different methodologies for measuring crystal precipitation, settling, and accumulation in molten glasses.…”