Feed-to-glass conversion during low activity waste vitrification

Effect of material properties on batch‐to‐glass conversion kinetics

“…[56][57][58] For temperatures above 1000 • C, 𝜆 ef f values were above 3.0 W m −1 K −1 , suggesting influences of thermal radiation and convective heat transfer from the coalescing bubbles. 57 Similar experiments with commercial glass batches showed a slow increase of 𝜆 ef f from 0.4 to 1.1 W m −1 K −1 (corresponding to 𝑎 ef f values from 2 × 10 −7 m 2 s −1 to 5 × 10 −7 m 2 s −1 ) between 200 and 1000 • C and a fast increase to 9 W m −1 K −1 ( 𝑎 ef f = 4 × 10 −6 m 2 s −1 ) by 1200 • C. 59 Faber et al 60 measured 𝑎 ef f of commercial batches as a function of temperature, obtaining 4 × 10 −7 m 2 s −1 for 𝑇 < 900 • C and 4 × 10 −6 m 2 s −1 at 1100 • C. Later, Conradt et al 61 obtained somewhat lower values: 1 × 10 −7 m 2 s −1 for 𝑇 < 900 • C and 4 × 10 −7 m 2 s −1 for 𝑇 > 900 • C. Heat penetration experiments with a fast-dried slurry feed indicated that 𝜆 ef f values are between 0.9 and 1.9 W m −1 K −1 for LAW feeds 62 and between 1.3 and 3.1 W m −1 K −1 for HLW feeds. 11 Because of the higher density of HLW feeds (𝜌 ∼ 1600 kg m −3 ) compared to LAW feeds (𝜌 ∼ 1000 kg m −3 ), the range of 𝑎 ef f values for HLW feeds (7 × 10 −7 to 1.6 × 10 −6 m 2 s −1 ) was similar to LAW feeds (8 × 10 −7 to 1.6 × 10 −6 m 2 s −1 ).…”

Vitrification as a method of soil remediation

“…This method of remediation is the most efficient and most widely used method in cases of contamination with substances of inorganic origin. It is very often also used for the treatment of soil contaminated with metals and radionuclides, because by glazing they are trapped and their release into deeper parts of the soil is prevented [16,34,36,53].…”

“…These techniques are minimally destructive to the site and the costs of their use are lower compared to ex situ techniques. In situ vitrification has a number of advantages over other technologies, especially due to its ability to treat mixed waste, including soil with buried waste or tanks, dried sludge, tailings, sediments, organic waste, chemical waste, radioactive waste, and mixtures of hazardous and radioactive waste [16,19,22,25,35,36,47,51,55,[57][58][59][60][61][62][63][64]. The application of in situ techniques depends on the type of pollution, the conditions prevailing in the contaminated medium as well as the conditions prevailing at that location [20,21].…”

“…In the vitrification process of radioactive liquid waste, the waste is brought to the top of a pool of molten glass contained in equipment called Joule Heated Ceramic Melter (JHCM) [35,36,61,65,66,68]. In the work of Goel et al [61], the treatment of radioactive waste obtained from plutonium production and the melting rate of batch material were investigated.…”

“…The cold cap is a cover of the same thickness that receives even amounts of heat both from the molten glass from below and from the plenum space from above. As the batch moves through the cold cap, chemical reactions and phase transitions occur, through which the batch turns into molten glass that moves downward from the cold cap [36,61,62,69,70]. Upon melting, each batch particle travels vertically downward through the cold cap, and its properties (e.g., density, dissolution rate of solids, reaction kinetics) change in response to increasing temperature [61].…”