Waste Forms Technology and Performance Final Report (2011) / Chapter Skim
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3 Waste Forms
3 Waste Forms
Pages 29-86
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However, the committee has included key historical and review article references in this chapter for interested readers. 3.1 WASTE FORM DEVELOPMENT The concept of immobilizing radioactive waste in either vitreous or crystalline materials is more than 50 years old.
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These alternative waste forms were later determined to be difficult to process, more costly to implement, and not as flexible for accommodating variations in waste composition as borosilicate glass (De et al., 1976; Dunson et al., 1982; Lutze et al., 1979; McCarthy, 1973; McCarthy and Davidson, 1975; Morgan et al., 1981; Ringwood et al., 1981; Schoebel, 1975) , even though 1 The Office of Nuclear Waste Isolation was located at the Battelle Memorial Institute.
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The R&D effort on nuclear waste forms during this period has been summarized by Lutze and Ewing (1988)
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Cements have also been used as binders and to encapsulate granular or cracked waste forms. A recent comprehensive review of cement systems for radioactive waste disposal can be found in Pabalan et al.
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Higher waste loadings for high Higher Table 3.1-1.eps incorporation Cr, Ni, and Fe wastes waste-loaded Constituents are present in the b. Good overall durability borosilicate, glass matrix, and benign crystals c.
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Crystalline Ceramics: Chemical a. High waste loading for single Pyrochlores for Single Phase incorporation constituents single actinide 4a.
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Metal Composites and minimized for Hanford encapsulation b. Superior overall durability- low-activity Granular waste forms must be double containment waste or Waste monolithed for disposal if not c.
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Cements, Geopolymers, Encapsulation a. Low waste loading Savannah River Hydroceramics, Ceramicretes b.
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3.3 WASTE FORM MATERIALS A wide range of materials are potentially suitable for immobilizing radioactive waste. For simplicity of discussion, these waste form materials have been grouped into eight classes based on their phase properties: 1.
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The mechanisms of constituent release are similar to those for natural analogues glasses (basalts) and minerals.
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39 WASTE FORMS Modifying Cations (M) Network Formers (G)
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Glass waste forms can have a wide range of compositions, but they are generally classified using
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• The major properties of glass waste form materials are summarized in Table 3.2. Glass is being used worldwide to immobilize HLW from reprocessing of spent nuclear fuel and targets.
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–4 and (AlO4) –5 glasses and/or alkali volatilization of radionuclides; waste loading and Ewing, 1988 aluminosilicate dependent on rapid cooling, e.g., 20 weight percent glasses UO2 if cooled rapidly but <10 weight percent if cooled slowly; improved durability over borosilicate glass.
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; abandoned because of Lutze and Ewing, 1988; RCRA issues with Pb component, low waste loading Marasinghe et al., 2000; (~20 weight percent) ; poor solubility of certain species Sales and Boatner, 1984 compared to borosilicate glass; tendency to devitrify.
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in al., 2009 TeO2-XCl-Li2O conventional glass or borosilicate glass systems; gels TeO2-XCl-Na2O such as Pt2Ge4S9.6 are used to immobilize actinides, XCl = "mixed chlorides" noble gases, carbon dioxide, and mixed chlorides. simulant at ~19 weight percent
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(weight percent) Produced]
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. k Acidic waste loadings are comprised of fission products and minor actinides; corrosion products and alkali are not included as for neutralized wastes.
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. GCMs offer several potential advantages over glass for use as waste form materials, including increased waste loadings, increased waste form density, and thus smaller disposal volumes.
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that can incorporate Increased Waste Loading Cs and Sr and other radionuclides Unacceptable Durability or Requires Changing Glass Family FIGURE 3.1 Schematic diagram illustrating the durability and waste loading of waste form materials relative to single-phase (homogeneous) glass.
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Begg and K Smith, Zirconolite: CaZrTi2O7 borosilicates borosilicate is the major crystalline phase; for low- ANSTO, written purity actinide wastes, Pu partitions into the communication zirconolite over the glass phase by a factor of 100:1 and Gd neutron absorbers partition into zirconolite; accommodates both actinides and any associated impurities: proliferation resistant because of the low purity and concentration of Pu in the waste form.
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Diopside: CaMgSi2O6 Eucryptite: LiAlSi2O6 Spodumene: LiAlSi2O6 Nepheline: NaAlSiO4 Diopside Borosilicate Waste loadings of ~30 weight percent could be Donald et al., 1997; Diopside: CaMgSi2O6 borosilicates achieved using these materials for European Lutze and Ewing, Powellite: CaMoO4 and Japanese commercial wastes, which 1988; Lutze et al., Perovskite: CaTiO3 normally accommodate ~16 weight percent; 1979; Ninomiya et al., glasses were melted at 1,300°C and controlled 1981 crystallization was carried out at temperatures in the range 800°C-1,100°C; Cs was in the diopside phase; La, Ce, Nd, and Pr were in the perovskite phase; Sr and Sm were in the glass phase; noble metals were metallic.
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et al., 2004; Vance et al., 1996a,b; Zyryanov and Vance, 1997 Alkali titanium Sodium titanium Formed by HIPing calcine (70 weight percent) Donald et al., 1997; Corundum: Al2O3 silicate silicates with Si, Ti, Al metal, and alkali oxides; for Lutze and Ewing, Cristobalite: SiO2 high Zr containing ICPP wastes.
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Silicate based Basalt Complex natural For Purex wastes: Different waste loadings from different waste Donald et al., 1997; oxide based on Si, Augite: (Ca, Mg, sources are possible; glasses melt in the range Hayward, 1988; Lutze Ca, Mg, Fe, Al, 1,300°C-1,400°C. Crystallization is carried and Ewing, 1988; Saidl Fe)
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PO4 crystallizes at 1,150°C and allowed to furnace al., 1996; Zhao et al., cool; investigated primarily for phosphate-rich 2001 or fluoride-rich waste streams including ICPP CaF2 wastes. Low temperature Bi-oxide based Mordenite zeolite Low-temperature sintering allows for glass Garino and Nenoff, sintering glasses glasses encapsulation of volatile gas-containing 2011; Garino, et al., matrices (e.g., AgI-MOR)
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. Murataite Also a derivative of the isometric Lian et al., 2002; Morgan fluorite structure A6B12C5TX40-x with and Ryerson, 1982; Sobolev multiple units of the fluorite unit cell; et al., 1997a,b; Stefanovsky et hosts U, Pu, and rare earth elements.
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3; distorted cubic structure; Utsonomiya et al., 2002; BO6 octahedra and XO4 tetrahedra Yudintsev, 2001, 2003; establish a framework structure Yudintsev et al., 2002 alternately sharing corners; A and B sites can host actinides and rare earth elements, and X =Si4+, Fe3+, Al3+, Ga3+, Ge4+, and V5+, making silicate, ferrite, aluminate, gallate, germinate, and vanadate garnets. Britholite (silicate (REE, Ca)
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; certain zeolites can be converted to condensed oxide ceramics by heating. This process is particularly attractive for waste form fabrication because capture and storage is preformed with minimal steps.
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. a naturally occurring feldspathoid 2000 mineral; incorporates the alkali, alkaline earths, rare earth elements, halide fission products, and trace quantities of U and Pu; sodalite is being investigated as a durable host for the waste generated from electro refining operations deployed for the reprocessing of metal fuel; minor phases in HLW supercalcine waste formsb where they retained Cs, Sr, and Mo, e.g., Na6[Al6Si6O24]
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. Phosphates Monazite CePO4 or LaPO4; very corrosion Boatner and Sales, 1988; resistant and can incorporate a large Ewing and Wang, 2002; range of radionuclides including Ewing et al., 1996; Glorieux actinides and toxic metals into its et al., 2009; Montel et al., structure; has been proposed as 2006; Wronkiewicz et al., a potential host phase for excess 1996; Zhang and Vance, weapons plutonium and as a host 2008 phase for radionuclides and toxic metals in glass-ceramic waste forms for low-level and hazardous wastes.
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. or more crystalline phases.6 Single-phase crystalline ceramics (Table 3.5)
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They have 1979a,b; Roy, 1977, very high loadings of fission products, 1979 typically 70 weight percent (simulated by stable isotopes in the experimental work) , and the chemistry of the different phases is driven by the fission products as majority components.
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Like crystalline ceramics, metal waste forms can consist of single or multiple phase assemblages, and the waste form itself can be granular or monolithic. Metal waste forms can be fabricated sintering or casting.
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. Metal waste forms are being used by DOE-EM to immobilize metallic fuel waste, including fuel hulls, at INL.
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that chemically binds contaminants such as chromium and technetium as insoluble species, thus reducing their tendency to leach from the waste form. Experimentation has shown that leaching of chromium and technetium was effectively reduced to levels that would allow all projected future salt solution compositions to be processed into Saltstone (MMES et al., 1992)
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. More recently, geopolymers have been investigated as a waste form for stabilization of Resource Conservation and Recovery Act metals; as binders for granular mineral wastes produced by fluidized bed steam reforming for low-activity waste at Hanford; and for the stabilization of cesium-137 and strontium-90 wastes.
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Hydroceramic waste forms have several potential applications to DOE-EM waste streams. They have been shown to be effective for immobilizing low-activity sodium-bearing waste at INL.
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The committee judges that there are many potential applications of new and improved waste form materials to DOE-EM waste streams. Table 3.7 illustrates the potential compatibility of the waste form materials described in this chapter to some of the DOE-EM waste streams that were described in Chapter 2.
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High-Sodium Waste INL: Sodium P P C C P P bearing waste SRS: Low-activity Fission waste/saltcake/ P P P P C P Products (FP) , supernate low U, Pu Hanford: Low activity waste/ C P P P P P P saltcake/supernate Other Spent fuel and Pu, FP, TRU, non-irradiated/ P U irradiated Cesium-strontium Cs, Sr P P P P P capsules Tank heels FP, U C Excess plutonium Pb Pu P P P P oxides continued
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Of course, compatibility is just one of several considerations in selecting a waste form material to immobilize a specific waste stream. Other considerations include the ease of processing, cost, and risk.
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1982. "Stability and Alteration of Naturally Occurring Low-Silica Glasses: Impli cations for the Long Term Stability of Waste Form Glasses," Scientific Basis for Nuclear Waste Management V, W
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1982. "Dissolution of Tailored Ceramic Nuclear Waste Forms," Nucl.
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2004. "Iron Phosphate Glasses: An Alternative for Vitrifying Certain Nuclear Wastes," Final Report for the U.S.
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1979. "Natural Glasses: Analogues for Radioactive Waste Forms," Scientific Basis for Nuclear Waste Management I, G
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as a Host Phase in Crystalline Waste Form Ceramics," Scientific Basis for Nuclear Waste Management XVIII, T Murakami and R
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1988. "Tailored Ceramics," In Radioactive Waste Forms for the Future, W
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1982b. "Ce ramic Nuclear Waste Forms," In Proceedings of International Seminar on Chemistry and Process Engineering for High Level Liquid Waste Solidification, Julich, FRG, Juel-Conf 42(2)
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1979. "Characterization of Glass and Glass Ceramic Nuclear Waste Forms," in Scientific Basis for Nuclear Waste Management I, G
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2000. "Vitrified Iron Phosphate Nuclear Waste Forms Containing Multiple Waste Components," Ceram.
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1979b. "Crystal Chemistry of the Synthetic Minerals in Current Supercalcine-Ceramics," Ceramics in Nuclear Waste Management, CONF-790420, National Technical Information Service, Springfield, Virginia, 315-320.
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2000. "Characterization of a Ceramic Waste Form Encapsulating Radioactive Electrorefiner Salt," Scientific Basis for Nuclear Waste Management XXIII, R
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2009. "Review of Literature and Assessment of Factors Relevant to Performance of Grouted Systems for Radioactive Waste Disposal," CNWRA 2009-001, Center for Nuclear Waste Regulatory Analysis, San Antonio, Texas.
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1979. "Science Underlying Radioactive Waste Management: Status and Needs," Scientific Basis for Nuclear Waste Management I, G.J.
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2000. "Char acterization of a Glass-Bonded Ceramic Waste Form Loaded with U and Pu," Scientific Basis for Nuclear Waste Management XXIII, R
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1995. "Candidate Glass-Ceramic Waste Forms for Immobilization of the Calcines Stored at the Idaho Chemical Processing Plant," Ceram.
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1983. "Department of Energy's Selection of High Level Waste Forms," In The Treatment and Handling of Radioactive Wastes, A
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2001. "Gadolinium Borosilicate Glass-bonded Gd-Silicate Apatite: A Glass-Ceramic Nuclear Waste Form for Actinides," Mat.
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