Durabilities and Microstructures of Radioactive Glasses for Immobilization of Excess Actinides at the Savannah River Site

Bibler, N.E.; Ramsey, W.G.; Meaker, T.F.; Pareizs, J. M.

doi:10.1557/proc-412-65

Cited by 26 publications

(9 citation statements)

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“…2 The initial glass composition developed for the vitrification of plutonium was based on these high lanthanide content glasses with the expectation that the ability to accommodate high lanthanide content would translate to the accommodation of plutonium within the glass. 3,4 The ability of high lanthanide content glasses to accommodate plutonium was demonstrated with this composition and the resulting glass was shown to exhibit excellent durability (as defined by the Product Consistency Test (PCT)). A drawback was identified with this composition, however, in that the formulation included listed Resource Conservation and Recovery Act (RCRA) metals namely lead and barium.…”

Section: Previous Actinide Glass Formulation Developmentmentioning

confidence: 99%

Development of an Alternative Glass Formulation for Vitrification of Excess Plutonium

Marra¹

2006

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Revision 0iii EXECUTIVE SUMMARYThe Department of Energy Office of Environmental Management (DOE/EM) plans to conduct the Plutonium Disposition Project at the Savannah River Site (SRS) to disposition excess weapons-usable plutonium. A plutonium glass waste form is a leading candidate for immobilization of the plutonium for subsequent disposition in a geologic repository. A reference glass composition (Lanthanide Borosilicate (La 2 O 3 -B 2 O 3 -SiO 2 (LaBS)) -Frit B) was developed and testing with the LaBS Frit B composition is underway to provide data to support the Yucca Mountain License Application process. The objective of this task was to investigate alternative frit compositions and/or processing conditions that may improve the performance of the reference Frit B -LaBS glass in the repository. The current LaBS Frit B composition was used as the baseline for alternative glass formulation development efforts. A review of the literature and past high actinide concentration glass development efforts was conducted to formulate candidate compositions for testing. Glass science principles were also utilized to determine candidate frit components that may meet task objectives. Additionally, glass processing methods (e.g. slow cooling or induced heat treatment) were investigated as potential means to improve the glass durability and/or minimize fissile material and neutron absorber separation. Based on these analyses, a series of candidate surrogate glasses were fabricated and analyzed. One composition was then selected for fabrication with PuO 2 and subsequently analyzed.A phase equilibrium approach, developed from the assessment of previous high lanthanide glass formulations, was used to recommend modifications to the SRNL Frit B composition. A specific recommendation to increase Ln 2 O 3 a content with concurrent reduction of Al 2 O 3 and SiO 2 content proved to be successful in improving the melting behavior and component solubility of the glass. This change moved the formulation from a compositional region of potential glass-in-glass phase separation toward a region near a low melting eutectic trough. The resulting LaBS Frit X composition was fabricated and tested.The chemical durability of the LaBS Frit X glass was shown to be equivalent to the reference Frit B composition as measured by the Product Consistency Test (PCT). The Frit X composition demonstrated improved component solubility in surrogate and plutonium testing. This composition also exhibited improved devitrification behavior that could translate to lower glass processing temperatures and minimize any negative impacts on glass pouring.Testing with the LaBS Frit X composition also indicated the potential to intentionally precipitate a PuO 2 -HfO 2 solid solution phase. This could result in a means to dramatically improve the plutonium leach performance in the repository by the formation of a highly insoluble phase with an inherent neutron absorber. Preliminary testing indicated that glass heat treatment could be used to intentionally form this phase...

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Section: Previous Actinide Glass Formulation Developmentmentioning

confidence: 99%

Development of an Alternative Glass Formulation for Vitrification of Excess Plutonium

Marra¹

2006

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“…Technology Center, SRTC) in support of the Plutonium Immobilization Program (PIP) [7,8,9]. Two frit compositions were developed for LaBS glass.…”

Section: Introductionmentioning

confidence: 99%

“…Due to the additional neutron absorbers present in the Frit B formulation, this frit became the reference composition at the culmination of PIP glass testing in 1997 [9]. PCT results for the LaBS Frit A compositions have been previously published [7,10], while only limited, unpublished PCT durability testing was performed on the LaBS Frit B composition.…”

Section: Introductionmentioning

confidence: 99%

Glass fabrication and product consistency testing of lanthanide borosilicate glass for plutonium disposition

Crawford

Marra

Bibler

2007

Journal of Alloys and Compounds

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The Department of Energy Office of Environmental Management (DOE/EM) plans to conduct the Plutonium Disposition Project at the Savannah River Site (SRS) in Aiken, SC, to disposition excess weapons-usable plutonium. A plutonium glass waste form is a leading candidate for immobilization of the plutonium for subsequent disposition in a geologic repository. The objectives of this present task were to fabricate plutonium-loaded lanthanide borosilicate (LaBS) Frit B glass and perform testing to provide near-term data that will increase confidence that LaBS glass product is suitable for disposal in the proposed Federal Repository. Specifically, testing was conducted in an effort to provide data to Yucca Mountain Project (YMP) personnel for use in performance assessment calculations. Plutonium containing LaBS glass with the Frit B composition with a 9.5 wt% PuO 2 loading was prepared for testing. Glass was prepared to support glass durability testing via the ASTM Product Consistency Testing (PCT) at Savannah River National Laboratory (SRNL). The glass was characterized with X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) prior to performance testing. This characterization revealed some crystalline PuO 2 inclusions with disk-like morphology present in the asfabricated, quench-cooled glass. A series of PCTs was conducted at SRNL with varying exposed surface area and test durations. Filtered leachates from these tests were analyzed to determine the dissolved concentrations of key elements. The leachate solutions were also ultrafiltered to quantify colloid formation. Leached solids from select PCTs were examined in an attempt to evaluate the Pu and neutron absorber release behavior from the glass and to investigate formation of alteration phases on the glass surface. A series of PCTs was conducted at 90°C in ASTM Type 1 water to compare the Pu LaBS Frit B glass durability to current requirements for High Level Waste (HLW) glass in a geologic repository. The PCT (7-day static test with powdered glass) results on the Pu-containing LaBS Frit B glass at SA/V of ≈ 2000 m -1 showed that the glass was very durable with an average normalized elemental release value for boron of 0.013 g/m 2 . This boron release value is ≈ 640X lower than normalized boron release from current Environmental Assessment (EA) glass used for repository acceptance. The PCT-B (7, 14, 28 and 56-day, static test with powdered glass)

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“…This glass has been shown to accommodate up to 10 weight percent Pu along with rare earth elements (REE)[ 11, which may be used as neutron absorbers (Gd). The durability of Pu-loaded LaBS glasses has been $own to be -5Ox better than high level waste (HLWZglasGs produced at the Defense Waste Processing facility @WPF) [2].…”

Section: Introductionmentioning

confidence: 99%

Homogeneous glass processing region defined for a lanthanide borosilicate glass composition for the mobilization of plutonium using thorium as a surrogate

Meaker¹

1996

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DISCLAIMER This SummaryA ternary diagram showing the homogeneous glass processing region of a base frit, rare earth oxide and thorium oxide has been developed for a residence temperature of 1475" C. Thorium oxide was used as a plutonium surrogate. All Tho2 glasses that were processed included a 1:l mole ratio of Th to Gd. Gadolinium is added to the glass as a neutron absorber. Forty individual glass compositions were melted at 1475" C for 4 to 6 hours with periodic stirring. Two glasses (B-20-25 and B-25-25) were processed with a Tho2 loading of 25 weight percent (oxide) without amorphous phase separation or crystalline species detected by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) or Transmissicn Electron Microscopy (TEM). These were processed with 55 weight percent frit, 20 weight percent rare earth oxides and 50 percent frit, 25 percent rare earth oxides.Crystalline species that formed outside of the homogeneous glass processing region due to solubility limits or insufficient processing temperature were identified. Amorphous phase separation was detected arad examined by TEM at high Tho2 loadings (20 to 30 weight percent oxide). The base frit was able to dissolve up to 65 weight percent rare earth oxides when thorium oxide was not present.Durability testing will be performed on three glasses from three different regions of the homogeneous glass processing region. Product Consistency Test (PCT) results are pending and will be added to this document under a future revision.'

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Durabilities and Microstructures of Radioactive Glasses for Immobilization of Excess Actinides at the Savannah River Site

Cited by 26 publications

References 1 publication

Development of an Alternative Glass Formulation for Vitrification of Excess Plutonium

Development of an Alternative Glass Formulation for Vitrification of Excess Plutonium

Glass fabrication and product consistency testing of lanthanide borosilicate glass for plutonium disposition

Homogeneous glass processing region defined for a lanthanide borosilicate glass composition for the mobilization of plutonium using thorium as a surrogate

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