EP-4739636-A1 - MOLYBDENUM-RICH SILICATE GLASSES AND METHOD FOR IMPROVING THE SOLUBILITY OF MOLYBDENUM IN A GLASS MELT

Abstract

The present invention relates to a silicate glass comprising from 35 to 45 wt% of silicon dioxide (SiO2), at most 15 wt% of molybdenum trioxide (MoO3), from 4 to 7 wt% of zirconium dioxide (ZrO2), from 1 to 3.5 wt% of phosphorus pentoxide (P2O5), and from 14 to 28 wt% of one or more alkali metal oxides and/or one or more alkaline-earth metal oxides, the weight percentages being expressed relative to the total weight of the glass. The present invention also relates to a method for improving the solubility of molybdenum in a glass melt.

Inventors

• LAURIN, Cloé
• PINET, OLIVIER
• NEYRET, Muriel

Assignees

• Commissariat à l'Energie Atomique et aux Energies Alternatives
• Orano Recyclage

Dates

Publication Date

20260513

Application Date

20240705

Claims (9)

1. 1. Silicate glass comprising: - 35 to 45% mass of silicon dioxide (SiCh), - at most 15% mass of molybdenum trioxide (MoCh), - from 4 to 7% mass of zirconium dioxide (ZrO?), - from 1 to 3.5% mass of phosphorus pentoxide (P2O5), and - from 14 to 28% by mass of one or more alkali metal oxides and/or one or more alkaline earth metal oxides, the mass percentages being expressed relative to the total mass of the glass.
2. 2. Silicate glass according to claim 1, characterized in that the MoOg is present in an amount of between 1 and 15% by mass, in particular between 5 and 14% by mass , more particularly still, between 8 and 13% by mass.
3. 3. Silicate glass according to claim 1 or 2, characterized in that said alkali metal oxide(s) and/or said alkaline earth metal oxide(s) are selected from the group consisting of lithium oxide (U2O), sodium oxide (Na2O), potassium oxide (K2O), rubidium oxide (Rb2O), cesium oxide (CS2O), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO).
4. 4. Silicate glass according to any one of claims 1 to 3, characterized in that said silicate glass further contains at least one element chosen from the group consisting of boron trioxide (B2O3), aluminum oxide (or alumina, AI2O3), and zinc oxide (ZnO).
5. 5. Silicate glass according to any one of claims 1 to 4, characterized in that said silicate glass further contains at least one element chosen from the group consisting of titanium dioxide (TiO2), vanadium oxide (V2O5), manganese oxide (MnO), manganese dioxide (Mn02), cobalt oxide (CoO), iron oxide (Fe2O3), nickel oxide (NiO), chromium oxide (Cr2O3), copper oxide (CuO), zinc oxide (ZnO), yttrium oxide (Y2O3), niobium oxide (Nb20s), technetium oxide (TcCh), lanthanum oxide (La2O3), neodymium oxide (Nd2O3), gadolinium oxide (Gd2O3), praseodymium oxide (Pr2O2), cerium dioxide (CeO2), selenium dioxide (SeO2), tellurium dioxide (TeO2), uranium dioxide (UO2), thorium dioxide (ThCh), europium oxide (EU2O3), antimony trioxide (Sb2O3), americium dioxide (AmO2), plutonium dioxide (PuO2), curium dioxide (CmCh), neptunium dioxide (NpO2), ruthenium dioxide (RuO2), rhodium dioxide (RhO2), palladium oxide (PdO), silver oxide (Ag2O), cadmium oxide (CdO), lead oxide (PbO), tin dioxide (SnO2), ionic fluorine (F-), ionic chlorine (Cl ), ionic sulfur trioxide (SO3 ), palladium (Pd), and rhodium (Rh).
6. 6. Use of zirconium dioxide (ZrO2) in an amount of 4 to 7% by mass and phosphorus pentoxide (P2O5) in an amount of 1 to 3.5% by mass to improve the solubility of molybdenum in a glass melt comprising - 35 to 45% mass of silicon dioxide (SiCh), - at most 15% mass of molybdenum trioxide (MoOs), and - from 14 to 28% by mass of one or more alkali metal oxides and/or one or more alkaline earth metal oxides, the mass percentages being expressed in relation to the total mass of the glass cast iron.
7. 7. Process for improving the solubility of molybdenum in a glass melt comprising - 35 to 45% mass of silicon dioxide (SiO2), - at most 15% mass of molybdenum trioxide (MoO3), and - from 14 to 28% by mass of one or more alkali metal oxides and/or one or more alkaline earth metal oxides, said method comprising a step of adjusting, in the glass melt, the amount of zirconium dioxide (ZrO2) to an amount of 4 to 7% by mass and phosphorus pentoxide (P2O5) to an amount of 1 to 3.5% by mass , the mass percentages being expressed relative to the total mass of the glass melt.
8. 8. Method according to claim 7, characterized in that said glass melt is obtained from a vitrification adjuvant and high-level nuclear waste (HLW) and/or long-lived intermediate-level nuclear waste (LLW-ILW).
9. 9. Method according to claim 7 or 8, characterized in that said HA and/or MA-VL nuclear waste is in the form of an aqueous nitric effluent containing in particular metal or metalloid nitrates, fission products, minor actinides and elements contained in the solutions and effluents from nuclear installations of the nuclear fuel cycle or from nuclear research centers.

Description

DESCRIPTION TITLE: MOLYBDENUM-RICH SILICATE GLASSES AND METHOD FOR IMPROVING THE SOLUBILITY OF MOLYBDENUM IN A GLASS CAST IRON TECHNICAL AREA The present invention relates to the general field of vitrification and more particularly to the field of vitrification of nuclear waste. Indeed, the present invention provides silicate glasses whose composition, particularly in terms of the quantity of zirconium dioxide (ZrO2) and phosphorus pentoxide (P2O5), makes it possible to obtain a glass cast iron rich in molybdenum without phase separation at the vitrification temperatures used in industrial processes. The present invention also relates to a method for improving the solubility of molybdenum in a glass melt. STATE OF THE PRIOR ART Nuclear waste is classified, according to the applicable regulations, on the one hand, according to the radioactive period of the radionuclides it contains: very short-lived waste (less than 100 days), short-lived (or VC i.e. less than 31 years) and long-lived (or VL i.e. greater than 31 years) and, on the other hand, according to its initial level of radioactivity (very low-level waste (VLL), low-level waste (LL), intermediate-level waste (IL) and high-level waste (HLW)). Thus, HA nuclear waste that is always long-lived (HA-VL) contains radionuclides emitting a, P, and y radiation and consists of fission products, activation products and minor actinides from the processing of spent fuel or from the spent fuel itself. Intermediate-level waste (ILW), for its part, contains significant quantities of a emitters, generally actinides. This ILW can be short-lived waste (ILW-VC) or long-lived waste (ILW-VL). Among ILW, only ILW-VL waste is treated by vitrification. The latter comes in particular from rinsing, sanitation, decontamination of nuclear installations, nuclear research centres or fuel cycle plants and sludge from effluent treatment operations. Among the nuclear waste management techniques, vitrification is commonly used for HA and MA-VL nuclear waste. This process consists of incorporating, in an amorphous material i.e. a glass of suitable composition such as sodium alumino-borosilicate, all the elements contained in the HA and MA-VL nuclear waste as defined above. The radionuclides are integrated in the form of oxides and are an integral part of the vitreous network. In practice, the industrial process of continuous vitrification consists of feeding a melting crucible heated by induction with the calcinate of HA and MA-VL nuclear waste and a vitrification adjuvant (or glass frit). However, there are other vitrification processes such as, for example, processes using direct induction furnaces (cold crucible), indirect induction furnaces (the walls of the furnace heating the glass), electrode furnaces or gas furnaces. Molybdenum is an element present in high concentrations in HA waste from the processing of certain old fuels and in MA-VL waste from the clean-up of nuclear facilities. To be produced on an industrial scale, the cast iron formed by the mixture comprising vitrification additives and MA-VL or HA waste in calcined form must be single-phase. However, molybdenum (Mo) is relatively poorly soluble in borosilicate glasses and tends to cause phase separation of the cast iron beyond 3% mass at 1100°C (which corresponds to 1 to 2% moi in simple borosilicates) in the packaging glasses for HA nuclear waste. Its content in the packaging glasses is therefore limited, which requires the production of a relatively large number of final packages for the immobilization of molybdenum-rich waste. Some patents have already addressed the issue of increasing the solubility of molybdenum in nuclear waste conditioning matrices. For example, patent application CN 110590161 A proposes adding vanadium in the form of vanadium pentoxide (V2O5) to the mixture comprising vitrification adjuvants and waste. nuclear [1]. This process cannot take advantage of the vanadium present in nuclear waste since the latter does not contain any, which increases the cost of such a process. International application WO 2009/039059 A1 [2] proposes, instead of adding the frit containing SiCh, B2O3 and AI2O3 to the nuclear waste, to add at least one of the three main constituents of this frit directly as an additive (raw chemical) in the waste solution, which would limit the formation of secondary phases. For molybdenum in particular, it is indicated that by removing B2O3 and AI2O3 from the frit and introducing them into the waste, the secondary molybdenum phases redissolve more quickly or form only little or not at all. This international application is therefore not aimed at improving the solubility of molybdenum but just at improving the redissolution of the molybdic phases. Furthermore, there are several scientific publications aimed at increasing the solubility of molybdenum in borosilicate glasses for the packaging of nuclear waste. Prakash et al, 2019 study the homogeneity of simplified borosilicate glasses SiO