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

[摘要] 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% PuO2 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 PuO2 inclusions with disk-like morphology present in the as-fabricated, 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 degrees C in ASTM Type I 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 approximate to 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 approximate to 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) normalized elemental releases were similar to the normalized elemental release values from PCT-A testing, indicating that the LaBS Frit B glass is very durable as measured by the PCT. Normalized plutonium releases were essentially the same within the analytical uncertainty of the lCP-MS methods used to quantify plutonium in the 0.45 mu m-filtered leachates and ultra-filtered leachates, indicating that colloidal plutonium species do not form under the PCT conditions used in this study. Published by Elsevier B.V.

[发布日期] 2007-10-11

[效力级别]  Proceedings Paper

[关键词] plutonium disposition;lanthanide borosilicate glass;leach testing