The full-scale cold crucible test on vitrification of sludge batch 4 (SB4) Savannah River Site HLW surrogate using a 418 mm inner diameter stainless steel crucible was carried-out for 66 hrs. Commercially available Frit 503-R4 (8 wt.% Li 2 O, 16 wt.% B 2 O 3 , 76 wt.% SiO 2 ) was used as a glass forming additive at a calcine to frit ratio of 1:1 (50 wt.% calcine, 50 wt.% frit). Two portions of slurry prepared from frit and mixture of chemicals simulating waste in amount of ~750 kg and from frit and waste surrogate prepared by the SRT-MST-2007-00070 procedure in amount of ~1,300 kg with water content of ~27 and ~50 wt.%, respectively, was processed and ~875 kg of the vitrified product in total (~415 + 460 kg) was obtained. Average parameters were as follows: vibration power -121.6 to 134.1 kW, feed rate (capacity) -25.1 to 39.8 kg/hr, glass pour rate (productivity) -14.0 kg/hr specific energy expenses for feed processing -4.8 to 3.4 kW×hr/kg, specific energy expenses for glass production (melting ratio) -8.7 to 9.6 kW×hr/kg, specific glass productivity -2453 kg/(m 2 ×d). The product was composed of major vitreous and minor spinel structure phases. No nepheline phase was found. Average degree of crystallinity was estimated to be ~12 vol.%. Cesium was found to be the most volatile component (up to ~60 wt.% of total). Lithium, sodium and boron are less volatile. Other major feed constituents (Al, Si, Mg, Fe, Mn) were not volatile but their carry-over with gas-vapor flow occurred.
Two experiments on the vitrification of a surrogate for the wastes from the Savannah River plant (USA) have been performed on a cold-crucible (inner diameter 216 mm) induction-melting bench facility at the Moscow Scientific and Industrial Association Radon (1.76 MHz, 60 kW). To obtain borosilicate glasses with two compositions containing 45 mass % oxides of the wastes (computed) a slurry with moisture content about 60 mass % and a mixture of reagents as the glass-forming additives gave a mass velocity of the slip 8 kg/h on average, glass output about 2 kg/h, and specific glass product rate about 47 kg/(m 2 ⋅h). The specific energy consumption was 20 kW⋅h/kg. It was shown that the mass velocity of the slip can be increased to 18 kg/h. Switching to glass-forming additives consisting of the special borosilicate frit-200 and -320 and lowering the water content in the slurry to 25-30 mass % increases the productivity of the process by 15-35%. The specific glass production rate reaches 100 kg/(m 2 ⋅h). The glasses produced contained a small quantity of a magnetitic spinel phase.Vitrification is now the best developed method of solidifying liquid radioactive wastes, especially high-level wastes. High-level wastes are vitrified commercially in metal induction melters at the average frequency (10-50 kHz) or joule-heated ceramic melters. One of the new methods being developed most intensively in France and our country is induction melting in a cold crucible at frequencies above 300 kHz, for example, in the Moscow Scientific and Industrial Association Radon facility for vitrifying medium-level wastes at 1760 kHz. This technology is of interest because it has certain advantages, such as a higher specific capacity and no contact between the melt and the refractories and electrodes, which increases the life span and operational reliability of the melter and allows much smaller dimensions thereby facilitating disassembly and removal after the melter is removed from operation [1,2].The experiments described in the present paper on the vitrification of surrogates of high-level wastes from one of the facilities of the US Department of Energy were performed within the framework of a signed contract. The objective of the present paper is to estimate the technological parameters of cold-crucible induction melting of a charge containing a surrogate of one form of high-level wastes (SB2) from the Savannah River facility and to determine the structure and properties of the glasses in order to compare them with those obtained in the USA using a ceramic melter.
An increase of the water content of a simulator of sludges from the test area at the Savannah River Plant (USA) which are vitrified in a cold crucible with inner diameter 236 mm from 50 to 70 wt % results in a substantial reduction of the mass loading rate of the sludge, production of molten glass, and specific production of the glass product. The specific energy expenditures on vitrification increase by more than a factor of 2. The formation of an undesirable nepheline phase is observed in samples containing more than 60 wt % wastes simulator. The chemical stability of the glass product remains high even when its wastessimulator content is 65 wt %.Vitrification is being studied in the USA as the main method of reprocessing liquid radioactive wastes, specifically, high-level wastes from a site in Savannah River (USA) [1]. Part of such wastes, for example, SB4 pulp, contains highly concentrated sodium, aluminum, and iron. 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.The experiments were performed in a cold crucible, whose inner diameter and height are 236 mm and 520 mm, respectively, in a stand facility [3]. 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 sludges S1 and S3 were prepared from P2 pulp and frit; the sludges S2 and S4 were prepared from P1 pulp and frit with water content 50 and 70 wt %, respectively. .x-Ray phase analysis (DRON-4 diffractometer, FeK α radiation) shows that the phase composition of the charges does not depend on the method of preparation: the main components in all pre-dried charges are aluminum hydroxide Al(OH) 3 in the form of gibbsite and goethite FeOOH and sodium nitrate (nitratin) NaNO 3 . Negligible amounts of manganese and nickel oxides-hydroxides, thenardite (Na 2 SO 4 ), an...
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