Electrochemical Measurements during the Anaerobic Corrosion of Steel

2000 ◽  
Vol 663 ◽  
Author(s):  
N.R. Smart ◽  
P.A.H. Fennell ◽  
R. Peat ◽  
K. Spahiu ◽  
L. Werme
Keyword(s):  
Redox Potential ◽  
Silver Chloride ◽  
Steel Wire ◽  
Reference Electrode ◽  
Glass Electrode ◽  
Spent Fuel ◽  
Geologic Repository ◽  
Steel Electrode ◽  
Anaerobic Corrosion ◽  
Corrosion Of Steel

ABSTRACTIn Sweden, it is proposed that spent fuel should be encapsulated in sealed cylindrical canisters for disposal in a geologic repository. The canisters would consist of a thick ferrous inner container and a copper overpack. If mechanical failure of the copper overpack occurred, allowing water to enter, the ferrous inner container would corrode anaerobically and liberate hydrogen. The rate of hydrogen generation due to the anaerobic corrosion of steel in anoxic groundwater has been measured using barometric cells. The aim of the work presented in this paper was to measure the redox potential, Eh and pH in the presence of anaerobically corroding steel, in a barometric cell. Two specially designed barometric cells were constructed. They were equipped with a silver chloride or calomel reference electrode, a gold Eh electrode, a glass electrode, and a steel electrode. The electrodes were allowed to stabilize in anoxic artificial groundwater and then a mass of pickled steel wire was introduced into the test cell. As the wires were added, the redox potential rapidly became more negative due to the rapid consumption of the residual oxygen. The corrosion potential of the steel was stable and a slow drift in pH was observed. The results are compared with the results of geochemical modelling. Extension of the work to investigate the electrochemical parameters in the presence of dissolved uranium species is discussed.

Mechanical Properties of Oxides Formed by Anaerobic Corrosion of Steel

2000 ◽  
Vol 663 ◽  
Author(s):  
N.R. Smart ◽  
A.E. Bond ◽  
J.A.A. Crossley ◽  
P.C. Lovegrove ◽  
L. Werme
Keyword(s):  
Mechanical Properties ◽  
Mild Steel ◽  
Corrosion Product ◽  
Photoelectron Spectroscopy ◽  
Spent Nuclear Fuel ◽  
Control Cell ◽  
Geologic Repository ◽  
Compressive Loads ◽  
Anaerobic Corrosion ◽  
Corrosion Of Steel

ABSTRACTIn Sweden, it is proposed that spent nuclear fuel should be encapsulated in sealed cylindrical canisters for disposal in a geologic repository. The canisters would consist of a thick ferrous inner container and a copper overpack. If mechanical failure of the copper overpack occurred, allowing water to enter, there would be a build up of ferrous corrosion product, which could induce stresses in the outer copper canister. This paper describes an apparatus, the ‘stress cell’, which was designed to measure the expansion caused by the anaerobic corrosion of steel under compressive loads. The apparatus consisted of a stack of steel and copper discs, which were immersed in simulated anoxic groundwater. A system of levers amplified the change in height of the stack, and the displacement was measured using sensitive transducers. Three cells were set up; two contained alternate mild steel and copper discs, and the third, a control cell, consisted of alternate stainless steel and copper discs. A slight contraction of the control cell was observed but no expansion was measured in the mild steel - copper cells.In parallel, coupons of mild steel and cast iron were corroded in anoxic, artificial groundwater at 50°C and 80°C for several months. The coupons were examined by atomic force microscopy (AFM) to determine the mechanical properties and the structure of the corrosion product films, and X-ray photoelectron spectroscopy (XPS) to identify the chemical composition of the film.

Leaching Behavior and α-Decay Damage Accumulation of UO2 Containing Short-Lived Actinides

2000 ◽  
Vol 663 ◽  
Author(s):  
V.V. Rondinella ◽  
J. Cobos ◽  
Hj. Matzke ◽  
T. Wiss ◽  
P. Carbol ◽  
...  
Keyword(s):  
Redox Potential ◽  
Sample Surface ◽  
Spent Fuel ◽  
Geologic Repository ◽  
Experimental Conditions ◽  
Α Decay ◽  
Level Of Activity ◽  
Congruent Dissolution ◽  
High Concentrations ◽  
Α Activity

ABSTRACTUO2 containing short-lived α-emitters, the so-called α-doped UO2, can simulate type (i.e. α- decay) and level of activity of spent fuel at the time when it might become exposed to groundwater in a geologic repository during storage. This allows studying α-radiolysis effects on the dissolution of the fuel matrix. Additionally, UO2 with high concentrations of α-emitters accumulate, during experimentally acceptable short times, the amount of decays, hence of property modifications, corresponding to long storage times for spent fuel. UO2 containing ∼10 and ∼0.1 wt% 238Pu was fabricated and tested. Leaching experiments in deionized water under unaerated conditions, with continuous monitoring of the evolution of the redox potential and pH in the leaching solutions, were performed. The Eh measurements showed a fast increase of the redox potential in the case of the material with the highest α-activity, while the UO2 containing ∼0.1 wt% 238Pu increased its potential more slowly. The redox potential for undoped UO2 decreased steadily during the experiment. As previously observed, higher fractions of U were released in the case of α-doped UO2 compared to undoped UO2. The fractions of U and Pu released during leaching from the α-doped materials were very similar, suggesting that congruent dissolution occurred. After leaching times longer than 10 h, only dissolved species were present in the solutions. Under these experimental conditions, characterized by relatively low values of the ratio sample surface/leachant volume, a dependence of the released amounts on the α-activity of the samples was observed. Periodical measurements of parameters like hardness, showed a rapid buildup of radiation damage in the material with the high α-activity. After more than two years, noticeable changes, namely an increase of the hardness, have begun to be observed also for the material with the low concentration of 238Pu.

Anaerobic Corrosion of Steel in Bentonite

2003 ◽  
Vol 807 ◽  
Author(s):  
Nicholas R. Smart ◽  
Andrew P. Rance ◽  
Lars O. Werme
Keyword(s):  
Spent Nuclear Fuel ◽  
Hydrogen Generation ◽  
Bentonite Clay ◽  
Geologic Repository ◽  
Corrosion Rates ◽  
Surrounding Matrix ◽  
Ferrous Material ◽  
Anaerobic Corrosion ◽  
Corrosion Of Steel

ABSTRACTIn Sweden, spent nuclear fuel will be encapsulated in sealed cylindrical canisters, consisting of a ferrous insert and a copper outer container, for disposal in a geologic repository. Ferrous support structures will also be used in the repository, which will be backfilled with bentonite clay. Once any residual oxygen has been consumed, any ferrous material exposed to anoxic groundwater will undergo anaerobic corrosion, liberating hydrogen, forming a magnetite film, and releasing iron ions into the surrounding matrix. In order to characterise these processes the rate of hydrogen generation of steel in bentonite was measured using a barometric gas cell technique. The initial corrosion rates were found to be higher than measured previously in comparable aqueous solutions, but the long-term corrosion rates were similar. Analysis of the bentonite matrix showed that iron produced by corrosion had penetrated into the bentonite matrix, suggesting that ferrous ion exchange had occurred.

Facile and Fast Detection of Genistein in Derris scandens by Square Wave Voltammetry using a Cobalt(II) Phthalocyanine-Modified Screen-Printed Electrochemical Sensor

2020 ◽  
Vol 16 (3) ◽  
pp. 341-348
Author(s):  
Surinya Traipop ◽  
Suchada Chuanuwatanakul ◽  
Orawon Chailapakul ◽  
Eakkasit Punrat
Keyword(s):  
Electrochemical Sensor ◽  
Square Wave Voltammetry ◽  
Silver Chloride ◽  
Reference Electrode ◽  
High Sensitivity ◽  
Plastic Substrate ◽  
Fast Analysis ◽  
Square Wave ◽  
Wave Voltammetry ◽  
Screen Printed

Background: Recently, Derris scandens, a Thai herbal medicine with anti-inflammatory activity, is widely used as beverage and supplementary food. When the traditional medicine is a choice for health therapy, the simple and reliable equipment is required to control the suitable consuming amount of the active component. Objective: To develop the electrochemical sensor for genistein determination in Derris scandens with high sensitivity and rapid operation. Methods: An in-house screen-printed electrochemical sensor consisting of a three-electrode system was developed for genistein determination. A silver/silver chloride (Ag/AgCl) reference electrode, a carbon counter electrode and a carbon working electrode were prepared on a 0.3-mm-thick plastic substrate by the screen-printing technique using conductive ink. The dimensions of each sensor were 2.5×1.0 cm. Only 50 µL of sample solution was required on this device for the determination of genistein concentration by rapid response square wave voltammetry. Results: The oxidation peak of genistein appeared with good response in acidic media at a peak potential of 0.6 V. Moreover, the signal was enhanced by modifying the conductive carbon ink with cobalt( II) phthalocyanine. Under the optimized conditions, the linear range was found to be 2.5-150 µM and the detection limit was 1.5 µM. Moreover, the small volume extraction was successfully developed without any further pre-concentration. This proposed method was applied to determine genistein in Derris scandens with satisfying results. Conclusion: The proposed method is promising as an alternative method for genistein determination with facile and fast analysis.

ELECTRODE POTENTIALS OF THORIUM TETRACHLORIDE IN ALKALI CHLORIDE MELTS

1964 ◽  
Vol 42 (6) ◽  
pp. 1315-1322 ◽  
Author(s):  
R. Srinivasan ◽  
S. N. Flengas
Keyword(s):  
Silver Chloride ◽  
Gravimetric Method ◽  
Reference Electrode ◽  
The Other ◽  
Alkali Chloride ◽  
Electrode Potentials ◽  
Silver Chloride Reference Electrode ◽  
Chloride Melts ◽  
Silver Silver ◽  
Silver Silver Chloride

The electrode potentials of the system Th, ThCl4 (KCl, NaCl) were measured at various concentrations of thorium chloride, and at temperatures between 670 °C and 850 °C, using a silver – silver chloride reference electrode. It was shown by a direct gravimetric method that the reaction,Th(metal) + ThCl4(melt) = 2ThCl2(in melt),postulated by previous investigators, did not take place.The activity coefficients, and the other partial molal properties of the solutions of ThCl4, in the equimolar mixture of potassium and sodium chlorides, were calculated as a function of temperature from the e.m.f. measurements.

Thermodynamics of electrolyte solutions: activity coefficients of NaCl in the NaCl–NiCl2–H2O system at 25, 35, and 45 °C

1990 ◽  
Vol 68 (2) ◽  
pp. 294-297 ◽  
Author(s):  
Ch. Venkateswarlu ◽  
J. Ananthaswamy
Keyword(s):  
Activity Coefficients ◽  
Silver Chloride ◽  
Osmotic Coefficients ◽  
Reference Electrode ◽  
Nickel Chloride ◽  
Electrolyte Solutions ◽  
Pitzer Formalism ◽  
Harned Coefficients ◽  
Silver Silver ◽  
Silver Silver Chloride

The activity coefficients of NaCl in the NaCl–NiCl2–H2O system were estimated at 25, 35, and 45 °C and total ionic strengths of 0.5, 1.0, 2.0, and 3.0 m by an EMF method using a Na-ion selective electrode and a silver–silver chloride reference electrode. The Harned coefficients were calculated at all the temperatures studied. At 25 °C the data were analysed using the Pitzer formalism. The osmotic coefficients and the excess free energies of mixing were also calculated at 25 °C. Keywords: activity coefficients, sodium chloride, nickel chloride, Pitzer equations, thermodynamics.

Analogues for the Corrosion-induced Expansion of Iron in HLW containers

2003 ◽  
Vol 807 ◽  
Author(s):  
Nicholas R. Smart ◽  
Rachel Adams ◽  
Lars Werme
Keyword(s):  
Cast Iron ◽  
Natural Waters ◽  
Spent Nuclear Fuel ◽  
Severe Damage ◽  
Geologic Repository ◽  
Iron Corrosion ◽  
Aqueous Environments ◽  
Archaeological Materials ◽  
Anaerobic Corrosion ◽  
Magnetite Film

ABSTRACTIn Sweden, spent nuclear fuel will be encapsulated in sealed cylindrical canisters, consisting of a cast iron insert and a copper outer container. The canisters will be placed in a deep geologic repository and surrounded by bentonite. If a breach of the outer copper container were to occur the cast iron insert would undergo anaerobic corrosion, forming a magnetite film whose volume would be greater than that of the base metal. In principle there is a possibility that accumulation of iron corrosion product could cause expansion of the copper canister. Anaerobic corrosion rates are very slow, so in the work described in this paper reference was made to analogous archaeological materials that had been corroding for long periods in natural anoxic aqueous environments. This paper describes a number of archaeological artefacts containing iron and copper corroding in constrained geometries in anoxic natural waters. No evidence has been obtained which would suggest that severe damage is likely to occur to waste canisters as a result of expansive corrosion of cast iron under repository conditions.

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