scholarly journals Simulating the feedback between corrosive gas generation and water availability for the evaluation of radionuclide mobility in the context of radioactive waste disposal

2021 ◽  
Vol 1 ◽  
pp. 109-110
Author(s):  
Laurin Wissmeier ◽  
Joachim Poppei
Keyword(s):  
Radioactive Waste ◽  
Water Availability ◽  
Hydrogen Gas ◽  
Metal Corrosion ◽  
Transport Parameter ◽  
Storage Facility ◽  
Iron Corrosion ◽  
Gas Generation ◽  
Corrosion Reaction ◽  
Source Sink

Abstract. It has been recently recognized that the availability of liquid water may be a controlling factor in the feedback between the physical processes of variably saturated liquid and gas flow on the one hand, and various chemical processes such as metal corrosion in an underground storage facility for radioactive waste on the other hand (e.g., Huang et al., 2021, and reference therein). Iron corrosion in anoxic conditions produces hydrogen gas and consumes water, as expressed by the following stylized chemical equation (e.g., Diercks and Kassner, 1988; Senior et al., 2021): 3Fe+4H2O⟶Fe3O4+4H2 Since water is an educt the corrosion reaction may be suspended or suppressed by the scarcity of water near the corroding surfaces. At the same time, gas pressure build-up through hydrogen generation may limit further water ingress. We developed a model that focuses on the close coupling between gas generation through iron corrosion and water availability. The feedback between iron corrosion, gas generation and liquid phase flow is considered by implementing the corrosion reaction in the subsurface flow and transport simulator PFLOTRAN (Hammond et al., 2012; Lichtner et al., 2015, 2020) making use of its coding provisions to implement source/sink terms for water and gas. These source/sink terms reflect the kinetics of the iron corrosion and its dependence on the educts, where the availability of water is approximated by the local liquid saturation. The model was applied to evaluate the mobility of radionuclides in, and their release from a hypothetical geological storage facility for radioactive waste. The radionuclides are traced through the emplacement chambers and drift by means of advective and diffusive transport. Parameter variations illustrate the influence of crucial modelling parameters on the simulation results.

Study on Mechanical Influence of Gas Generation and Migration on Engineered Barrier System in Radioactive Waste Disposal Facility

2010 ◽  
Author(s):  
Mamoru Kumagai ◽  
Shuichi Yamamoto ◽  
Kunifumi Takeuchi ◽  
Yukihisa Tanaka ◽  
Michihiko Hironaga
Keyword(s):  
Radioactive Waste ◽  
Time Evolution ◽  
Mechanical Stability ◽  
Water Saturation ◽  
Hydrogen Gas ◽  
Gas Pressure ◽  
Radioactive Waste Disposal ◽  
Gas Generation ◽  
Disposal Facility ◽  
Engineered Barriers

In Japan, some radioactive waste with a relatively higher radioactivity concentration from nuclear facilities is to be packaged in rectangle steel containers and disposed of in subsurface disposal facilities, where normal human intrusion rarely occurs. After the closure of a facility, its pore is saturated with groundwater. If the dissolved oxygen of the pore water is consumed by steel corrosion, hydrogen gas will be generated from the metallic waste, steel containers, and reinforcing bars of concrete mainly by anaerobic corrosion. If the generated gas accumulates and the gas pressure increases excessively in the facility, the facility’s barrier performance might be degraded by mechanical influences such as crack formation in cementitious material or deformation of bentonite material. Firstly, in this study, we assessed the time evolution of the gas pressure and the water saturation in a sub-surface disposal facility by using a multi-phase flow numerical analysis code, GETFLOWS, in which a pathway dilation model is introduced and modified in order to reproduce the gas migration mechanism through the highly compacted bentonite. Next, we calculated the stress applied to the engineered barriers of the facility from the results of the time evolution of the pressure and the saturation. Then, we conducted a mechanical stability analysis of the engineered barriers by using a nonlinear finite element code, ABAQUS, in order to evaluate their performances after the closure of the facility.

Modelling Multi-Phase Flow Phenomena in Concrete Barriers Used for Geological Disposal of Radioactive Waste

2007 ◽  
Author(s):  
Dirk Mallants ◽  
Diederik Jacques ◽  
Janez Perko
Keyword(s):  
Radioactive Waste ◽  
Hydrogen Gas ◽  
Phase Flow ◽  
Gas Generation ◽  
Boom Clay ◽  
In Situ Experiments ◽  
Production Of Hydrogen ◽  
Multi Phase Flow ◽  
Engineered Barriers ◽  
Multi Phase

Gas generation and gas transport phenomena occur in geological repositories of radioactive waste. This has been extensively studied over the past ten years, usually within the framework of international projects (MEGAS, PROGRESS, etc.). These studies indicate that the production of hydrogen by anaerobic corrosion of metals is the most important source for gas generation. Laboratory and in situ experiments carried out at SCK•CEN indicate that, in the presence of Boom Clay (the reference geologic formation for deep disposal studies in Belgium), carbon steel suffers generalised corrosion estimated conservatively at 1 μm y−1. Simulations with the finite difference multi-phase flow code TOUGH2 were carried out in an attempt to quantify the effects of hydrogen gas generation on desaturation of initially saturated concrete components of the disposal gallery and the concomitant expulsion of cementitious pore-water into the surrounding host formation. Several simulation cases were considered and addressed differences in initial water saturation degree of concrete, hydrogen gas generation rate, and material porosity. Several conceptual models have been developed to better understand the phenomena at work in the transport of gas in the cementitious engineered barriers and Boom Clay. Multi-phase flow modelling was found to be helpful to get insight into the phenomenology of coupled water-gas flow in the cementitious engineered barriers. However, modeling the discontinuous variation in the conductivity of the clay relative to the gas (creation of preferential pathways) requires incorporation of geomechanical processes in conventional models based on the laws of two-phase flow.

Risk Perception Mapping: Using Ethnography to Define the Locally Affected Population for a Low-Level Radioactive Waste Storage Facility in Michigan

1991 ◽  
Vol 93 (3) ◽  
pp. 611-635 ◽  
Author(s):  
Richard W. Stoffle ◽  
Michael W. Traugott ◽  
John V. Stone ◽  
Paula D. McIntyre ◽  
Florence V. Jensen ◽  
...  
Keyword(s):  
Risk Perception ◽  
Radioactive Waste ◽  
Storage Facility ◽  
Low Level ◽  
Waste Storage ◽  
Low Level Radioactive Waste ◽  
Radioactive Waste Storage

scholarly journals Thickness-dependent photoelectrochemical properties of a semitransparent Co3O4 photocathode

2018 ◽  
Vol 9 ◽  
pp. 2432-2442 ◽  
Author(s):  
Malkeshkumar Patel ◽  
Joondong Kim
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Hydrogen Generation ◽  
Hydrogen Gas ◽  
Generation Rate ◽  
Alkaline Electrolyte ◽  
Stoichiometric Ratio ◽  
Gas Generation ◽  
Pec Cells ◽  
Gas Generation Rate

Co3O4 has been widely studied as a catalyst when coupled with a photoactive material during hydrogen production using water splitting. Here, we demonstrate a photoactive spinel Co3O4 electrode grown by the Kirkendall diffusion thermal oxidation of Co nanoparticles. The thickness-dependent structural, physical, optical, and electrical properties of Co3O4 samples are comprehensively studied. Our analysis shows that two bandgaps of 1.5 eV and 2.1 eV coexist with p-type conductivity in porous and semitransparent Co3O4 samples, which exhibit light-induced photocurrent in photoelectrochemical cells (PEC) containing the alkaline electrolyte. The thickness-dependent properties of Co3O4 related to its use as a working electrode in PEC cells are extensively studied and show potential for the application in water oxidation and reduction processes. To demonstrate the stability, an alkaline cell was composed for the water splitting system by using two Co3O4 photoelectrodes. The oxygen gas generation rate was obtained to be 7.17 mL·h−1 cm−1. Meanwhile, hydrogen gas generation rate was almost twice of 14.35 mL·h−1·cm−1 indicating the stoichiometric ratio of 1:2. We propose that a semitransparent Co3O4 photoactive electrode is a prospective candidate for use in PEC cells via heterojunctions for hydrogen generation.

scholarly journals Remedial Treatment of Corroded Iron Objects by EnvironmentalAeromonasIsolates

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Wafa M. Kooli ◽  
Thomas Junier ◽  
Migun Shakya ◽  
Mathilde Monachon ◽  
Karen W. Davenport ◽  
...  
Keyword(s):  
Iron Reduction ◽  
Building Materials ◽  
Solid Phase ◽  
Corrosion Products ◽  
Metal Corrosion ◽  
Economic Losses ◽  
Cytotoxic Activities ◽  
Iron Corrosion ◽  
Pathogenic Potential ◽  
Wide Range

ABSTRACTUsing bacteria to transform reactive corrosion products into stable compounds represents an alternative to traditional methods employed in iron conservation. Two environmentalAeromonasstrains (CA23 and CU5) were used to transform ferric iron corrosion products (goethite and lepidocrocite) into stable ferrous iron-bearing minerals (vivianite and siderite). A genomic and transcriptomic approach was used to analyze the metabolic traits of these strains and to evaluate their pathogenic potential. Although genes involved in solid-phase iron reduction were identified, key genes present in other environmental iron-reducing species are missing from the genome of CU5. Several pathogenicity factors were identified in the genomes of both strains, but none of these was expressed under iron reduction conditions. Additionalin vivotests showed hemolytic and cytotoxic activities for strain CA23 but not for strain CU5. Both strains were easily inactivated using ethanol and heat. Nonetheless, given a lesser potential for a pathogenic lifestyle, CU5 is the most promising candidate for the development of a bio-based iron conservation method stabilizing iron corrosion. Based on all the results, a prototype treatment was established using archaeological items. On those, the conversion of reactive corrosion products and the formation of a homogenous layer of biogenic iron minerals were achieved. This study shows how naturally occurring microorganisms and their metabolic capabilities can be used to develop bio-inspired solutions to the problem of metal corrosion.IMPORTANCEMicrobiology can greatly help in the quest for a sustainable solution to the problem of iron corrosion, which causes important economic losses in a wide range of fields, including the protection of cultural heritage and building materials. Using bacteria to transform reactive and unstable corrosion products into more-stable compounds represents a promising approach. The overall aim of this study was to develop a method for the conservation and restoration of corroded iron items, starting from the isolation of iron-reducing bacteria from natural environments. This resulted in the identification of a suitable candidate (Aeromonassp. strain CU5) that mediates the formation of desirable minerals at the surfaces of the objects. This led to the proof of concept of an application method on real objects.

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