Evaluation of Used Fuel Disposition in Clay-Bearing Rock

Jové-Colón, Carlos F.; Payne, Clay; Knight, Andrew W.; Ho, Tuan Anh; Rutqvist, Jonny; kim, Kunwi; Xu, Hao; Guglielmi, Yves; Caporuscio, Florie; Sauer, Kirsten; Rock, Marlena; M., Houser, L.; James, Jerden,; Gattu, V. K.; Ebert, W. L.

doi:10.2172/1481545

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“…The analcime-wairakite composition range likely is a result of the bulk composition of the system and the zeolite-forming reactions. The low aqueous silica activities observed in this set of experiments may indicate that wairakite is stable with respect to analcime (Jove Colón et al, 2017) or that the formation of zeolite minerals keeps aqueous silica levels low. The crystal structure of the zeolite reaction product is a topic of continued investigation (i.e., orthorhombic analcime versus monoclinic wairakite) and the reaction products are referred to as analcime- (Figure 10).…”

Section: Clay Mineral Alterationmentioning

confidence: 82%

Engineered Barrier System R&D and International Collaborations – LANL (FY20): Spent Fuel and Waste Disposition

Caporuscio

Sauer

Rock

et al. 2020

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Over the past seven years the Spent Fuel and Waste Science and Technology has investigated Engineered Barrier Systems (EBS) at higher heat loads (200 to 300 °C) and pressure (150 bar). This document presents the summary of Opalinus Clay experiments (EBS-14 to EBS-26). These results include clay mineral analyses, authigenic mineral formation, and steel interface and corrosion results. The past few years of experimental work focused on the interactions of Opalinus Clay wall rock and EBS components (e.g., bentonite, metal, and cement) at repository conditions and steel corrosion rates. Starting in FY-18, ordinary Portland Cement was added to the experimental system. A series of eight-week experiments were run in FY-18 (EBS-23 and EBS-24) and FY-19 (EBS-25 and EBS-26). Various types of stainless steel (316SS, 304SS, and LCS) were added to the experiments; future characterization will quantify the corrosion rates. This report documents the geochemical and mineralogical results of experiments EBS-14 through EBS-22, which included Opalinus Clay ± Wyoming Bentonite ± metal (Cu, 316SS, 304SS, and LCS). These experiments were conducted at 200 to 300 °C, 150 bar, and 6 weeks to 6 months. The aqueous solutions at 300 °C remained undersaturated with respect to quartz. Montmorillonite remained stable at 200 and 300 °C and very minor illite/illite-smectite was observed. Clay minerals in the Opalinus Clay fragments experienced significant changes at 300 °C, including the formation of illite, illite-smectite, and chlorite-smectite. Authigenic analcimewairakite was a major mineralogical product that formed at 300 °C along fractures and edges of Opalinus Clay fragments and within the bentonite matrix, but was not observed in the 200 °C products. The analcime-wairakite composition varies with the bulk composition of the system. Montmorillonite illitization within the Wyoming Bentonite EBS material was likely limited by the bulk chemistry of the system (i.e., low potassium and aluminum). Authigenic illite was likely limited to the Opalinus Clay fragments and nucleated on pre-existing illite in the shale. Previous experiments with only Wyoming Bentonite documented the transformation of precursor clinoptilolite into analcime with a sodium-and silica-rich composition. Results from Opalinus Clay-only 300 °C experiments indicate that the dissolution and re-precipitation of other phases, such as kaolinite, calcite, and smectite, may also contribute to zeolite formation, as Opalinus Clay does not contain the clinoptilolite precursor. Further, the low permeability limited authigenic analcime formation to fractures and edges of the Opalinus Clay fragments. Preliminary characterization of reaction products from the 200 °C Opalinus Clay-Wyoming Bentonite-Portland Cement experiment series are presented. Significant mineralogical changes occur with the introduction of cement. Structural degradation of the smectite mineral structure from within Wyoming Bentonite, due formation of interlayered illite, silica cementation, and/or CSH mineral intergro...

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