Vitrification of a simulator of Savannah River site (USA) wastes with high iron and aluminum content on bench and commercial facilities with a cold crucible

Abstract

Bench and commercial-facility experiments have been performed on cold-crucible vitrification of a simulator of high-level wastes from the Savannah River site (USA). The wastes contained up to 29 mass% Fe 2 O 3 and 26 mass% Al 2 O 3 . The specific product flow reached 1700 and 2450 kg/(m 2 ·day) with specific energy consumption 14-16 and 9-10 kW·h/kg, respectively. The crucibles did not undergo any appreciable corrosion during the period of the work performed and are reusable. The product consisted of a borosilicate matrix, containing up to 10 vol.% crystalline phase of spinel. The method of induction melting in a cold crucible is especially effective for crucibles with a large diameter, since the specific productivity increases and the specific energy consumption on the vitrification of high-level wastes decreases.The successful demonstration of the possibility of vitrifying iron-containing high-level wastes -SB2 pulps from tanks at the Savannah River site -by the method of induction melting in a cold crucible [1, 2] has made it possible to proceed to the next stage of the work -a study of the possibility of vitrifying a simulator with a high content of iron and aluminum -SB4 pulps ( Table 1). The same bench and commercial facilities for vitrifying liquid radioactive wastes from the Moscow Scientific and Industrial Association Radon with 520 and 860 mm high cold crucibles with inner diameters 216 and 418 mm, respectively, were used for this purpose.A high concentration of sodium and aluminum in the wastes created a danger of chemically unstable phases of nepheline forming, so that the American specialists developed the frit composition 503-R4, which does not contain sodium oxide [3] and makes it possible to obtain glass, satisfying the criterion SiO 2 /(SiO 2 + Na 2 O + Al 2 O 3 ) > 0.62 (the concentration of the components is expressed in mass fractions), without crystallization of nepheline [4].For the experiment on the bench facility, the wastes simulator was prepared from the reagents with the addition of water. The reagents H 3 BO 3 , Li 2 CO 3 , and SiO 2 were taken in the mass ratio corresponding to be 503-R4 frit: 16 B 2 O 3 , 8 Li 2 O, and 76 SiO 2 . Two portions of a batch were prepared in the form of sludge containing 40 and 60 mass% of wastes oxides in the glass and 31-32 and 42-43 mass% water (B1 and B2), respectively.

Corrosion of glass contact refractories for the vitrification of radioactive wastes: a review

“…No CCM crucible corrosion was observed during vitrification trials of simulated US HLW 39. However, Kobolev et al 185 noted traces of corrosion on the surface of the pipes that came into contact with molten glass at the pouring level during bench scale trials of other simulated HLW vitrification.…”

“…Cold crucible melters have been trialled and/or implemented in USA, France, Korea, Russia and elsewhere. [1][2][3]26,[39][40][41] Plasma melting has yet to be widely implemented for radioactive waste vitrification; however, it has been used for non-radioactive waste vitrification and there is considerable interest in its potential use for LLW, ILW and mixed waste vitrification. 3,[42][43][44][45][46][47][48] Vitrification technologies of primary importance to this review are therefore:…”

Vitrification of a high-level iron-aluminate wastes simulator in a cold crucible

“…One negative aspect of vitrification is the formation of nepheline, which depletes the matrix glass phase of aluminum and silicon and, in consequence, lowers the chemical resistance of the glass product [2]. The present work is a continuation of studies of the possibility of vitrifying high-level wastes which contain a high concentration of aluminum and iron by the method of induction melting in a cold crucible [3][4][5]. The objective of the present work is to determine the maximum content of wastes in the glass product that does not result in the precipitation of appreciable quantities of nepheline and the technological parameters of the melting in a crucible during the vitrification of a simulator of highlevel wastes.…”

“…A portion of the wastes simulator in the form of pulp (P1) was prepared using a procedure developed at the Savannah River National Laboratory, where manganese dioxide and iron and nickel hydroxides are precipitated and then a solution of sodium hydroxide and nitrate with pH 10.5 is added followed by the remaining components of the wastes [6], and another portion (P2) was prepared from reagents by a simplified method as described in [5]. In all, four charges in the form of sludge were prepared from the wastes simulators and 503-R4 frit with composition (wt %) B 2 O 3 16, Li 2 O 8, SiO 2 76, calculated for obtaining glass with 60 and 70 wt % high-level wastes simulator (Table 1).…”

“…The remaining 10% of the input power is expended on the evaporation of water, heating the charge, melting the calcinate, and homogenizing the melt. The main reason for the low efficiency of the process is the small size of the crucible -for vitrification of the wastes simulator in large-diameter crucibles the thermal energy going to vitrifying the wastes reaches 30-40% [4,5]. High water content in sludges and an increase of the mass of the wastes in the charge have a negative effect on vitrification.…”