Supplemental Immobilization of Hanford Low-Activity Waste: Cast Stone Screening Tests

Westsik, Joseph H.; Piepel, Gregory F.; Lindberg, Michael J.; Heasler, P.G.; Mercier, T.M.; Russell, Renee L.; Cozzi, A. D.; Daniel, William E.; Eibling, R.E.; Hansen, E.; Reigel, M.; Swanberg, David J.

doi:10.2172/1126363

Cited by 40 publications

(131 citation statements)

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“…The reductive capacity of LAW Cast Stone, both those prepared previously (see Westsik et al 2013) and newly prepared LAW NW-and SE-Cast Stones with high Tc concentration that had been leached using the EPA 1315 leach test of Cast Stone under air-equilibrated or O 2 -saturated leaching conditions decreased by ~30-70% after leaching compared to the same Cast Stones before leaching. The reductive capacity of both NW-and SE-Cast Stones decreased most significantly when they were fractured and leached under an O 2 -saturated condition because of the increased exposed surface areas from the fractures.…”

Section: Discussionmentioning

confidence: 95%

“…Measure the reductive capacity of different types of dry ingredients, the 8 LAW simulants used in Westsik et al (2013), and short-term cured Cast Stone before and after leaching with different leaching conditions. The reductive capacities of dry ingredients from NW and SE sources, various LAW simulants, and final Cast Stone before and after leaching tests were measured using two different methods, the Ce(IV) and Cr(VI) methods.…”

Section: Executive Summarymentioning

confidence: 99%

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Characterization of Technetium Speciation in Cast Stone

Um¹,

Jung²,

Wang³

et al. 2013

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Executive SummaryThis report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) EM-31 Support Program (EMSP) subtask, "Production and Long-Term Performance of Low Temperature Waste Forms" to provide additional information on technetium (Tc) speciation characterization in the Cast Stone waste form. To support the use of Cast Stone as an alternative to vitrification for solidifying low-activity waste (LAW) and as the current baseline waste form for secondary waste streams at the Hanford Site, additional understanding of Tc speciation in Cast Stone is needed to predict the long-term Tc leachability from Cast Stone and to meet the regulatory disposal-facility performance requirements for the Integrated Disposal Facility (IDF). Characterizations of the Tc speciation within the Cast Stone after leaching under various conditions provide insights into how the Tc is retained and released. The data generated by the laboratory tests described in this report provide both empirical and more scientific information to increase our understanding of Tc speciation in Cast Stone and its release mechanism under relevant leaching processes for the purpose of filling data gaps and to support the long-term risk and performance assessments of Cast Stone in the IDF at the Hanford Site.Various formulations of Cast Stone that include secondary waste simulants and different LAW simulants have been characterized previously. For this report, smaller Cast Stone monoliths were prepared with high Tc concentrations spiked into the 7.8 M Na overall average LAW simulant using dry ingredients from two different sources (referred to as NW and SE). These small Cast Stone monoliths were used for this Tc speciation characterization. The following subtasks are included within the Tc speciation characterization task:1. Measure the reductive capacity of different types of dry ingredients, the 8 LAW simulants used in Westsik et al. (2013), and short-term cured Cast Stone before and after leaching with different leaching conditions. The reductive capacities of dry ingredients from NW and SE sources, various LAW simulants, and final Cast Stone before and after leaching tests were measured using two different methods, the Ce(IV) and Cr(VI) methods. One type of blast furnace slag (BFS) and the high-Ca fly ash were obtained from LaFarge North America Inc. in Pasco, Washington, and these materials are referred to as the NW slag and fly ash. The second BFS and the low-Ca fly ash are the same materials used in the Saltstone processing facility at the Savannah River Site in South Carolina and are referred to as the SE materials. Much more of the solids dissolve in the strong acid (pH ~1-2) environment created by the Ce(IV) method compared to circumneutral pH (~7.0) condition created by the Cr(VII) method. Among the dry ingredients, the reductive capacity measured by the Ce(IV) method was the highest for BFS (0.793 meq/g for NW slag and 0.800 meq/g for SE slag). The reductive ...

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Section: Discussionmentioning

confidence: 95%

Section: Executive Summarymentioning

confidence: 99%

Characterization of Technetium Speciation in Cast Stone

Um¹,

Jung²,

Wang³

et al. 2013

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show abstract

“…3,4,5 • Determine the relationship between the Cast Stone reduction capacity measured by the Angus-Glasser Method 6 and leachability of Tc from depth discrete samples.…”

Section: Objectivesmentioning

confidence: 99%

Cast Stone Oxidation Front Evaluation: Preliminary Results For Samples Exposed To Moist Air

Langton¹,

Almond²

2013

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“…Note however that these limitations resulted in a targeted iodine concentration in the simulated salt solutions that was approximately two orders of magnitude higher than the expected concentration. 2 Future testing at more realistic iodine concentrations may be beneficial.…”

Section: 3mentioning

confidence: 99%

“…1 The current WRPS study is investigating simulated salt solutions at 5.0 M and 7.8 M sodium. 2,3 Increasing the sodium concentration in Cast Stone has the potential to significantly reduce the overall volume of the waste form, increase waste throughput rates, and reduce the time and expense needed to complete cleanup missions.…”

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confidence: 99%