Refractory materials for the melters of plants used in vitrification of radioactive wastes

Abstract

Results of corrosion resistance tests of different types of refractory materials (fusion cast baddeleyite-corundum, high-zirconium, corundum, and chromium-containing materials) in melts of borosilicate and phosphate glass used for vitrification of radioactive wastes are presented. It is shown that the fusion cast high-chromium refractory materials KhPL-85 and KhMG-5, both of which contain more than 80.0% Cr 2 O 3 , possess more than twice the corrosion resistance of the chromium-aluminum-zirconium refractory KhATs-30 (an analog of the refractory material ER 2161) and more than triple that of the baddeleyite-corundum refractories ER 1681 and ER 1711. High-chromium refractory materials may be considered promising candidates for use as the material of melters in plants for vitrification of radioactive wastes.Vitrification of radioactive wastes is a new and promising trend that supports the reprocessing and conversion of hot liquid radioactive wastes into a vitreious state safe for long-term storage. The industrial technology of vitrification of radioactive wastes is based on a process of electrofounding of glass from solutions of wastes, fluxing additions to directly fired glass-making electric kilns (ceramic melter) at temperatures up to 1150°C, and pouring of the vitreous product into thick-walled tanks made of corrosion-proof steel for immobilization and subsequent burial.The German plant Pamela was the first plant provided with a ceramic melter at which highly active wastes were subjected to vitrification [1]. Industrial plants that subject radioactive wastes to vitrification on the basis of a ceramic melter are now functioning in Russia, the United States, and Japan.The first domestic technology of vitrification of highly active liquid radioactive wastes on an industrial scale was implemented in 1987 at FGUP PO Mayak [2]. Three EP-500 furnaces were in operation at this enterprise from 1987 to 2006. A fourth furnace (EP-500/4 type) with a three-year service life has been in operation since 2007; construction of another two furances that would be capable of vitrification and reduction to safe state of around 60 million C of radioactive wastes is planned to be completed by 2012. Obviously, the demand for vitrification furnaces can be expected to increase in the furture with the development of the atomic energy complex in Russia and the growth in the volume of radioactive wastes.A new generation of furnaces of enhanced reliability that satisfy the requirements of ecological safety and possess a service life of up to ten years are now under development. In view of the rather high cost of such furnaces (the EP-500/3 furnace cost more than US$17,000,000 in 2001) and the requirements of maximal reliability and safety, the refractory materials used in the lining of the furnace must exhibit maximal corrosion resistance to the action of molten glass [3].In the EP-500 the refractory brickwork of the furnace that comes into contact with the glass melt is produced from Bk-33 baddeleyite-corundum refractory at OAO Shcherbinsk...

High‐Alumina Boron‐Containing Refractory Castables

“…Moreover, as reported in the proposed phase equilibrium diagrams of the Al 2 O 3 ‐B 2 O 3 system, A 2 B and A 9 B 2 can be found accompanied by a liquid phase above 470°C. Therefore, the formed boron‐rich liquid might lead to the decrease in the castables' mechanical performance (Fig.…”

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

“…The majority of the laboratory trials utilised static corrosion tests, although some 71 71,72 have used agitated test conditions. Figure 6 shows the results of a comparative test of the corrosion resistance of various high Cr 2 O 3 , Al 2 O 3 and ZrO 2 refractories, discussed recently by Sokolov and Gasparyan 174. Fusion cast Al 2 O 3 –Cr 2 O 3 –Fe 2 O 3 –MgO refractories, principally Monofrax K-3, and others including AZS, Cr 2 O 3 and Al 2 O 3 have been widely tested and have become the glass contact refractories of choice for US Department of Energy HLW and LLMW vitrification programmes 70,71,73…”

“…Laboratory based, 68,[70][71][72][73]75,[172][173][174][175] post-service (inactive) 77,95,176 and post-service (radioactive) 74,76 analyses of the performance of type I refractories have been undertaken. The majority of the laboratory trials utilised static corrosion tests, although some 71,72 have used agitated test conditions.…”

“…Figure 6 shows the results of a comparative test of the corrosion resistance of various high Cr 2 O 3 , Al 2 O 3 and ZrO 2 refractories, discussed recently by Sokolov and Gasparyan. 174 Fusion cast Al 2 O 3 -Cr 2 O 3 -Fe 2 O 3 -MgO refractories, principally Monofrax K-3, and others including AZS, Cr 2 O 3 and Al 2 O 3 have been widely tested and have become the glass contact refractories of choice for US Department of Energy HLW and LLMW vitrification programmes. 70,71,[73][74][75][76][77][78] The corrosion mechanisms of Monofrax K-3 have received considerable attention.…”