This paper presents the results obtained from coprecipitation experiments of uranyl solutions in the presence of metallic iron and/or its alteration phases in synthetic bentonitic-granitic composition water. Experiments were done under oxidising conditions at room temperature. The pH range covered was 7.4 -8.8. Changes in the uranium concentrations and the characterisation of the secondary phases formed in the experiments were done using XRD and SEM-EDS and are presented herein.Final uranium concentration values were in the range of 2·10 -5 -5·10 -4 mol (kg of H 2 O) -1 . In all cases, results from these experiments did not show evidence of a clear effect due to the presence of iron (metallic or previously corroded) on the uranium concentration. These data were similar to those obtained by coprecipitation in similar conditions but in absence of iron material.Boltwoodite was observed [K 2 (UO 2 ) 2 (SiO 3 ) 2 (OH) 2 ·3H 2 O] in iron surface materials and characterized in all experiments. Based on the experimental data obtained (uranium concentration in solution and bulk solid phase characterisation) we propose the following surface-mediated reaction: 2
Any environmental performance assessment of spent nuclear fuel disposal requires a prediction of the spent fuel matrix alteration rate when contact with groundwater is established. Taking into account the disposal design, the groundwater at the expected depth of the repository are generally reducing. These reducing redox conditions near the spent fuel surface may be changed to oxidising conditions by the radiolysis of water, due to radiation associated with the waste. This study is focussed on determining the influence of the γ radiation on the spent fuel matrix alteration rate under simulated repository conditions. A series of sequential leaching experiments under controlled conditions have been done. The experiments simulate the repository environmental conditions when engineering barriers are degraded and groundwater arrives at the surface of the spent fuel. In these experiments SIMFUEL (SIMulated FUEL) was used as analogue of spent fuel. Two types of leachant (i.e., granitic water and bentonitic-granitic water) were used in the leaching experiments. These experiments were irradiated using γradiation at an industrial irradiation facility with a 60 Co source. The results obtained in this study show different behaviour as a function of both the leachant used in the leaching experiments and the initial atmosphere used in the experiments. As a preliminary conclusion of this experimental work, under γ radiation and a small partial pressure of H 2 (1 bar) in the first steps of the leaching process has a beneficial effect since U in solution is lower than any other conditions and overall alteration rate is minimized. For experimental times longer than one day, a clear increase of the U in solution is revealed in the experimental run products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.