Carbon Steel Containers Research Articles

Influence of the Al Content on the Electrochemical Behavior of Zn-Al Cold-Sprayed Coatings in the Context of the Deep Geological Disposal of Radioactive Waste

For high-level radioactive waste, the French National Radioactive Waste Management Agency is currently developing a 500 m deep geological disposal facility called Cigéo. Carbon steel containers will be used to contain the wastes in the specific conditions of the disposal. The use of a sacrificial coating was studied as an additional protection for the containers against corrosion. A previous work had shown the possibility to use Zn-Al coatings in this specific medium. To optimize the coatings’ performance, the cold-spraying process was considered instead of the previously used wire arc spraying because it can increase the cohesion between the particles in the coating. Moreover, three aluminum contents, i.e., 5, 15 and 25 wt.%, were considered. The characterization of the obtained coatings revealed a strongly heterogeneous composition for the lower Al content (5 wt.%), with local Al contents from 1.3 wt.% Al to 44.5 wt.% Al. The corrosion study was carried out in a specific solution mimicking the pore solution of the surrounding cementitious material designed for disposal at a temperature of 50 °C. First, the polarization curves acquired with coated steel electrodes revealed the pseudo-passive behavior of the 25 wt.% Al coating, while for the other compositions, the coating remained active. Moreover, the higher aluminum content (25 wt.%) induced an important decrease in potential, with a possible risk of hydrogen embrittlement for the protected steel. Secondly, the sacrificial properties were investigated through 6 months of experiments using coated electrodes with cross-like defects and coated electrodes coupled with bare steel electrodes. Whatever the composition of the coating, the protection was maintained, with the 15 wt.% Al coating giving the best performance.

Investigating of the Effect of Air-Formed Surface Films on Copper Corrosion Properties

Canada’s plan for the safe and long-term management of used nuclear fuel involves utilizing an engineered multi-barrier system that will be deposited in a deep geological repository (DGR).1 Developed and proposed by the Nuclear Waste Management Organization (NWMO), the used fuel bundles will be placed in carbon-steel containers that will be coated with a about 3-mm thick corrosion resistant copper (Cu) coating. To date, Cu corrosion studies have been performed on freshly polished metal coupons that have undergone a rigorous cleaning procedure to eliminate air-formed organic and oxide films from the material’s surface. However, prior to emplacement in a DGR, the containers will be fabricated and stored for periods of time where such surface films can deposit and accumulate.2 Furthermore, a standardized surface preparation/finish procedure has yet to be determined. The influence of air-formed surface films on the Cu coating’s atmospheric and aqueous corrosion behaviour is important to understand the likelihood and extent of localized corrosion under anticipated DGR conditions. This work aims to investigate the effect of aging period, surface roughness, and storage environment on the surface film’s chemical composition, morphology, and influence on Cu corrosion properties using a suite of surface analytical and electrochemical methods. The results will assist in the future development of a surface preparation strategy of the Cu coatings prior to used fuel confinement and DGR deposition. Hall, D. S., Behazin, M., Jeffrey Binns, W. & Keech, P. G. An evaluation of corrosion processes affecting copper-coated nuclear waste containers in a deep geological repository. Prog. Mater. Sci. 118, 100766 (2021).Gateman, S. M. et al. Corrosion of One-Step Superhydrophobic Stainless-Steel Thermal Spray Coatings. ACS Appl. Mater. Interfaces 12, 1523–1532 (2020).

Galvanic Coupling of Copper and Carbon Steel in the Presence of Bentonite Clay and Chloride

The long-term containment plan for Canada’s used nuclear fuel employs copper-coated carbon steel (CS) containers encased in compacted bentonite clay buffer boxes. In the hypothetical case of a through-coating defect, galvanic interactions between the Cu coating and the CS vessel are dependent on the conditions at the container surface. A zero-resistance ammeter was used to measure the galvanic current between Cu and CS electrodes at various area ratios in the presence of aerated 1 M NaCl and obstructive layers of bentonite slurry. The presence of bentonite resulted in an order of magnitude decrease in the corrosion rate of the steel. As shown by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis and Raman spectroscopy, the extent of steel corrosion decreased significantly in the presence of bentonite slurry, favouring mild surface etching over oxide growth. Electrochemical impedance spectroscopy (EIS) measurements showed that the total impedance on carbon steel generally increased with bentonite layer thickness, but the total impedance on Cu plateaued when the layer exceeded 6 mm, consistent with trends in galvanic current density on carbon steel. The benign conditions produced by the bentonite slurry are attributed to the slightly alkaline pH and the hindrance of O2 diffusion.

Microbiology of barrier component analogues of a deep geological repository.

Canada is currently implementing a site selection process to identify a location for a deep geological repository (DGR) for the long-term storage of Canada's used nuclear fuel, wherein used nuclear fuel bundles will be sealed inside copper-coated carbon steel containers, encased in highly compacted bentonite clay buffer boxes, and sealed deep underground in a stable geosphere. Because a DGR must remain functional for a million years, it is important to examine ancient natural systems that serve as analogues for planned DGR components. Specifically, studying the microbiology of natural analogue components of a DGR is important for developing an understanding of the types of microorganisms that may be able to grow and influence the long-term stability of a DGR. This study explored the abundance, viability, and composition of microorganisms in several ancient natural analogues using a combination of cultivation and cultivation-independent approaches. Samples were obtained from the Tsukinuno bentonite deposit (Japan) that formed ∼10 mya, the Opalinus Clay formation (Switzerland) that formed ∼174 mya, and Canadian shield crystalline rock from Northern Ontario that formed ∼2.7 bya. Analysis of 16S rRNA gene amplicons revealed that three of the ten Tsukinuno bentonite samples analyzed were dominated by putative aerobic heterotrophs and fermenting bacteria from the phylum Actinobacteria, whereas five of the Tsukinuno bentonite samples were dominated by sequences associated with putative acidophilic chemolithoautotrophs capable of sulfur reduction. The remaining Tsukinuno bentonite samples, the Northern Ontario rock samples, and the Opalinus Clay samples generated inconsistent replicate 16S rRNA gene profiles and were associated primarily with contaminant sequences, suggesting that the microbial profiles detected were not sample-specific but spurious. Culturable aerobic heterotroph abundances were relatively low for all Tsukinuno bentonite samples, culturable anaerobic heterotrophs were only detected in half of the Tsukinuno samples, and sulfate-reducing bacteria (SRB) were only detected in one Tsukinuno sample by cultivation. Culture-specific 16S rRNA gene profiles from Tsukinuno clay samples demonstrated the presence of phyla Bacteroidetes, Proteobacteria, Actinobacteria, and Firmicutes among aerobic heterotroph cultures and additional bacteria from the phyla Actinobacteria and Firmicutes from anaerobic heterotroph plate incubations. Only one nucleic acid sequence detected from a culture was also associated with its corresponding clay sample profile, suggesting that nucleic acids from culturable bacteria were relatively rare within the clay samples. Sequencing of DNA extracted from the SRB culture revealed that the taxon present in the culture was affiliated with the genus Desulfosporosinus, which has been found in related bentonite clay analyses. Although the crystalline rock and Opalinus Clay samples were associated with inconsistent, likely spurious 16S rRNA gene profiles, we show evidence for viable and detectable microorganisms within several Tsukinuno natural analogue bentonite samples.

Corrosion-Enhancing and Corrosion-Reducing Accessories in Bentonite Surrounding Copper-Shielded Containers for Nuclear Waste

Abstract The standard design for the underground disposal of high-level nuclear waste consists of a carbon steel container that hosts the waste shielded by a 5-cm-thick layer of corrosion-resistant...

Modeling radionuclide migration from activated metallic waste disposal in a generic geological repository in Lithuania

There are two RBMK-1500 type reactors in Lithuania, which are under decommissioning now. Long-lived low and intermediate level radioactive metallic waste generated during operation and decommissioning of the nuclear power plant is foreseen for deep geological disposal (DGR). A preliminary assessment of the radionuclide release from metallic waste and migration through the engineered barriers of the generic DGR in crystalline rocks is presented in this study. The radionuclide flux to backfill and geosphere is investigated for three different container alternatives: (1) disposal of metallic waste in stainless steel containers, (2) disposal in carbon steel containers and (3) disposal in which the container is not a barrier for radionuclide migration. In addition, the impact of surface contamination of the activated waste on the radionuclide flux is investigated. Comparison of maximum fractional flux to backfill between Alternatives 1 and 2 revealed that the container material plays a noticeable role in the migration of long-lived low mobility radionuclides. The maximum fractional flux to the geosphere for all radionuclides increases from Alternative 1 to Alternative 3. Surface contamination is an important parameter when the maximum radionuclide flux to backfill is observed during the early post-closure period.

The anoxic corrosion behaviour of copper in the presence of chloride and sulphide

AbstractThe Canadian used fuel container for the long‐term containment of spent nuclear fuel in a deep geological repository comprises a 3‐mm copper corrosion barrier applied directly to a strong carbon steel container. Although a final site for the Canadian deep geological repository has not yet been chosen, the site selection process has narrowed down to two candidate locations with unique groundwater chemistry, particularly with respect to salinity. Therefore, to ensure the long‐term integrity of the used fuel container, the effect of a range of groundwater chemistries on copper corrosion must be understood. The primary variables of interest are the influence of chloride concentration and the consequences of the interaction of hydrogen sulphide, naturally present in the groundwaters in very low concentrations, with the copper cladding. An additional aspect that has been investigated is the behaviour of copper in pure water. The anoxic corrosion of copper can be inferred by the very slow release of hydrogen gas. In this paper, new data are presented, which demonstrate an extremely sensitive approach to quantify the very limited hydrogen release at 75°C. Initially, corrosion rates under conditions approximating an anticipated Canadian deep geological repository were significantly less than 0.5 nm/year and they invariably declined over the course of several months/years. The presence of chloride or hydrogen sulphide was found, under specific conditions, to stimulate short‐term corrosion behaviour, which was consistent with anion‐assisted surface rearrangement, not bulk corrosion.

The Influence of Vanadium Additions on Isothermally Formed Bainite Microstructures in Medium Carbon Steels Containing Retained Austenite

The influence of V additions on isothermally formed bainite in medium carbon steels containing retained austenite has been investigated using in-situ high energy X-ray diffraction (HEXRD) and ex-situ electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis (EDX) techniques in the transmission electron microscope (TEM). No significant impact of V in solid solution on the bainite transformation rate, final phase fractions or on the width of bainite laths was seen for transformations in the range 375–430 °C. No strong influence on the dislocation density could be detected, although quantitative analysis was impeded by ferrite tetragonality. A reduction in the carbon content of retained austenite Cγ that is not believed to be due to competition with VC or cementite precipitation was observed. No influence of V on the carbon supersaturation in bainitic ferrite Cb could be directly measured, although carbon mass balance calculations suggest Cb slightly increases. A beneficial refinement of blocky MA and a corresponding size effect induced enhancement in austenite stability were found at the lowest transformation temperature. Overall, V additions result in a slight increase in strength levels.

A probabilistic model for estimating the life expectancy of used nuclear fuel containers in a Canadian geological repository: Baseline model

Placement of encapsulated used nuclear fuel in a deep geological repository is recognised internationally as the leading option to achieve containment and isolation from the environment and the public. In Canada, containment and isolation are proposed through an engineered barrier system, which comprises a copper-coated, welded carbon-steel container to encapsulate used fuel, highly compacted bentonite clay buffer, and the geosphere. Critical to regulatory approval and public confidence is the robustness of the engineered barrier system to perturbations capable of affecting the survival of used fuel containers over time scales of interest. However, uncertainty in the evolving conditions of a repository adds to the challenge of used fuel container life predictions. A new probabilistic container survival model is presented, featuring a simple, multi-level Monte Carlo technique to account in part for the unique constraints posed by a deep geological repository layout and an engineered barrier system on lifetime predictions.

Chemical and microbial storage stability studies and shelf life determinations of commercial Brazilian biodiesels stored in carbon steel containers in subtropical conditions

In the present work long term storage chemical and biological stability of three different commercial Brazilian biodiesel fuels have been studied. Commercial biodiesel fuels from soybean, beef tallow, and blend soybean/beef tallow were initially kept for 60 days in their original containers at the laboratory. Subsequently, the biodiesels were transferred to 1 L carbon steel containers and stored at the laboratory for 90 days exposed to room temperature and humidity. Monthly analyzes of some biodiesel chemical characteristics were conducted. After 90 days, biodiesel samples were sent to be evaluated for their susceptibility to microbial contamination by biomass formation and fuel degradationby FTIR. Results show that after 30 days all biodiesel went out of specification to the water content parameter. Similar result was found for the oxidative stability parameter, except for pure beef tallow biodiesel, which went out of specification after 60 days to the acid value parameter. In terms of microbial contamination, at the end of 60 days, the highest biomass formation occurred in pure soybean biodiesel, followed by blend soybean/beef tallow, and neat beef tallow biodiesels. However, the higher ester carbonyl degradation was observed for 100% beef tallow biodiesel. Thus, in the experimental conditions of this study, the limited shelf life of all studied biodiesels was drastically reduced by the hygroscopicity of the fuel, which acts as a facilitator of other degradative processes, including microbial contamination. The commercial soybean biodiesel was considered more vulnerable to long term storage due to its reduced oxidative stability, as well as its higher susceptibility to microbial development. Special care should be addressed by the time that this sort of biodiesel is added to the diesel, unless more robust antioxidant and multipack additives are used, and special handling practices are adopted.

Assessment of gamma radiation shielding properties of concrete containers containing recycled coarse aggregates

This paper presents an assessment of gamma radiation shielding performance, specifically in terms of surface dose rate, of concrete containing virgin and recycled coarse aggregates (RCA) to be used for a transportable concrete container for radioactive waste. In order to evaluate radiation shielding performance of the transportable concrete container a numerical simulation method is performed using Monte Carlo N-particle version 6.1 (MCNP6.1). Prior to evaluating radiation shielding performance of the transportable concrete containers, radiation shielding properties of four different concrete mixtures which have two different compressive strengths, 40 and 70 MPa, containing natural coarse aggregate (NCA) and recycled coarse aggregate (RCA), respectively, are assessed using experimental and numerical simulation methods in terms of linear attenuation coefficient (μ) to verify the reliability of the numerical simulation method. Density, compressive strength, and static modulus of elasticity tests are conducted to determine the parameters for transportable concrete container design. Based on the physical properties of concrete a transportable concrete container is designed. In order to assess the radiation shielding with respect to the maximum surface dose rate of the concrete containers, three different radioactive wastes are assumed to be loaded in the containers with metal drums and radiation shielding analysis is carried out using MCNP6 simulation code for the four different concrete containers, comparing with the existing carbon steel container. It was found that the results from numerical simulation are in good agreement with the experimentally determined results. In terms of the maximum surface dose rate, all concrete containers showed considerably lower surface dose rate than the existing carbon steel container.

Influence of iron corrosion on nuclear glass alteration processes: nanoscale investigations of the iron-bearing phases

ABSTRACTA carbon steel container including nuclear glass has been altered for 2 years in Andra’s Underground Research Laboratory to simulate the behaviour of waste package. Post-mortem analyses at different scales (macro–micro–nano) have been performed to identify neoformed phases on iron corrosion products (ICP) and in the glass alteration layer (GAL). It has been shown at nanometric scale that important quantities of iron and silicon were found in the GAL and in the ICP respectively. Using a comparative approach with phyllosilicate references, STXM, at Si-K edge, suggests presence of trioctahedral species in the GAL and in ICP. Relevant fits of the STXM spectra are obtained with a Fe-rich chlorite for the nanostructured GAL, which could be formed according to chloritisation mechanism.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Galvanic corrosion of copper-coated carbon steel for used nuclear fuel containers

ABSTRACTCanada is currently considering Cu-coated carbon steel containers for the long-term storage of used nuclear fuel in a deep geological repository. The Cu coating provides a corrosion-resistant barrier, protecting the underlying steel from coming into contact with groundwater. However, galvanically accelerated corrosion of steel is possible if there is a defect through the Cu coating. To investigate this scenario, the progression of steel corrosion at the base of a simulated though-coating defect was imaged using synchrotron X-ray micro-computed tomography. Results show that coatings produced using different methods (cold spray, annealed cold spray, electrodeposition) lead to different corrosion propagation geometries. These findings can be used for modelling steel corrosion at a though-coating defect under deep geological repository conditions.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Softening Kinetics of Plain Carbon Steels Containing Dilute Nb Additions

The recrystallisation and precipitation kinetics of a plain carbon steel with 0.017 % Nb were studied using the double-hit deformation technique for interpass holding of 5 and 20s. The present study focuses on the effect of prestrain and deformation temperature on recrystallisation behaviour of the investigated steel. The fractional softening was calculated based on the percentage difference between the areas under the interrupted and uninterrupted deformations flow curves. The T5% and T95%, marking the beginning and end of recrystallisation, respectively, are determined as a function of strain. Quantitative microstructural studies validated the findings from the softening studies. The predicated results of recrystallisation regime are found to be in agreement with industrial observation and other experimental measurement for this steel. It can be seen that the dilute additions of Nb can influence the static recrystallisation of austenite under certain rolling condition which may lead to improved mechanical properties of steel.

NOx emissions and the component changes of ternary molten nitrate salts in thermal energy storage process

The objective of this work is to investigate the NOx emissions from HITEC (ternary molten nitrates of 7wt.%NaNO3-53wt.%KNO3-40wt.%NaNO2) in thermal energy storage (TES) process and the effects of 45# carbon steel (1045, ASTM) on NOx emission as well as the component changes in HITEC. Referring to the national environmental protection standard (HJ479-2009) in China, NOx emissions in tail gases were measured in one hour for heating the molten salts in a quartz glass boat during TES process. Furthermore, the concentrations of nitrate and nitrite ion in molten salts samples were determined, and chemical thermodynamic calculations of related reactions were carried out to explain the mechanism of NOx emissions. The results show that HITEC contained in a quartz glass or carbon steel container in air atmosphere can release NOx in the operating temperature range, which were caused by several reactions between nitrate and SiO2 or Fe. The concentrations of NOx emissions increase with the rise of temperature. In the practical application, NOx emission is acceptable since the amount of NO2 or NO will dramatically decreased in the liquid salts by reacting with NaNO2.

INFLUENCE OF MAGNETIC FIELDS OF VARYING INTENSITY ON THE MORPHOLOGICAL VARIABILITY OF LONG-LEGGED WOOD FROG LARVAE (RANA MACROCNEMIS) AFTER THE EXPOSURE PERIOD FROM NEURULA TO HATCHING

Aim. The aim is to study morphological diversity of long-legged wood frog larvae after continuous exposure to a magnetic field of varying intensity during embryonic development from neurula to leaving the egg membranes. Methods. We have created hypermagnetic conditions by increasing the tension of the natural magnetic field. Petri dish with fragments of laid eggs has been placed in a low carbon steel container (20,5x17x9). Outside, the container has been covered with a shell made of sheet copper. Results. Rana macrocnemis, obtained in the first experiment, compared with the control specie, showed a significant increase in tail and body length. The second experiment showed an increase in tail and body length. The third experiment, compared to the control specie, showed no difference. The fourth experiment showed an increase in tail and body length. The fifth experiment also showed an increase in tail and body length. Conclusions. The effect of magnetic fields on the embryonic development period from neurula to hatching showed that the length of the trunk is a more stable feature, the tail length increases in the experiments, and only in the third experiment it remained unchanged compared to control species.

Corrosion behaviour of waste disposal container in sub-surface disposal system

This study was conducted in order to clarify the long term corrosion behaviour of containers made of carbon steel. Natural immersion crevice corrosion tests were carried out for 360 days in an alkaline and reducing environment using a combination of materials including carbon steel and welding materials or bolts. In addition, potentiostatic crevice corrosion tests were carried out for 90 days. In both tests, there was no evidence to suggest localised corrosion in the different kinds of metal contact parts, including carbon steel, welding materials and bolts. It was also recognised that crevice corrosion was less likely to be generated on disposal container materials. From these experimental results, it is believed that the possibility of localised corrosion is extremely low if the environment around the carbon steel container is maintained under highly alkaline and reducing conditions.

NOx emissions and NO2- formation in thermal energy storage process of binary molten nitrate salts

Referring to the national environmental protection standard of PR China, HJ479-2009, NOx emissions and the effect of 45# carbon steel (1045, ASTM) on it in thermal energy storage (TES) process of binary molten nitrate (BMN) salts (a eutectic salt mixture named as solar salt with the component of 60% NaNO3 and 40% KNO3) are discussed in this paper. The accumulative absorption concentrations of NOx emissions in tail gases of molten salts heated at different temperatures were measured to study the thermal decomposition situation of molten salts in TES process. Furthermore, the concentrations of nitrite ion in molten salts samples were determined and chemical thermodynamic calculations of related reactions were done to explain the results. The research shows that BMN salts contained in silica or carbon steel container in the air under certain conditions can release NOx in its use of temperature range. The concentrations of NOx emissions and nitrite ion in molten salts both increase with the rise of the temperature. After contacting with 45# carbon steel, the total concentrations of NOx emissions and nitrite ion in molten salts increased, which may be caused by Fe component in the carbon steel.

Simulations of long-term anaerobic corrosion of carbon steel containers in Canadian deep geological repository

Carbon steel is a candidate container material for the disposal of used fuel in a deep geological repository in sedimentary host rock in Canada. Prediction of the long term anaerobic corrosion behaviour of the container is important, not only because it partly determines the container lifetime but also because the products of the corrosion reaction, Fe(II) and H2, can impact the properties of the clay based sealing materials and host rock. A mechanistically based numerical model is described that predicts both the long term corrosion rate and the effects on the repository environment, including the periodic build-up and release of H2, the precipitation of Fe3O4 within the bentonite buffer, and the alteration of montmorillonite to a non-swelling clay. The results of a reference simulation for a repository in shale host rock are described.

Insight into the mechanism of carbon steel corrosion under aerobic and anaerobic conditions

We particularly focused our study on identifying the corrosion products formed at 30 °C on carbon steel under aerobic and anaerobic conditions and on following their evolution with time due to enhanced microbial activity under environmental and geological conditions. The nature and structural properties of corrosion products were investigated by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD) and confocal micro-Raman spectroscopy. Structural characterisation clearly showed the formation of iron oxides (magnetite and maghemite) under aerobic conditions. Under anaerobic conditions, the first corrosion product formed on the steel surface was nanocrystalline mackinawite, which was then followed by a fast transformation process into the pyrrhotite phase, and the Raman spectrum of monoclinic pyrrhotite was proposed for the first time. Finally, this study also shows that in the context of geological disposal of radioactive waste, the corrosion of carbon steel containers in anoxic and sulphidogenic environments sustained by sulphate-reducing bacteria may not be a problem notably due to the formation of a passive layer on the steel surface.