Vessel Steel Research Articles

The Influence of Copper Coatings on the Corrosion of Carbon Steel Substrates

Within the multi-barrier system proposed for the permanent disposal of spent nuclear fuel, the primary engineered barrier is the sealed metallic container. The proposed Canadian container design involves a carbon steel vessel coated with 3 mm of Cu. Since they will be buried ~500 m below ground, the carbon steel provides the necessary structural support, while the Cu coating provides corrosion resistance.1 The coatings will be formed by either electrodeposition or a cold spray technique. Despite a considerable amount of research into the corrosion behaviour of the outer Cu coating,2 the impact of a defect in the coating on the corrosion of steel remains largely unstudied. Should a defect simultaneously expose both Cu and steel to groundwater, galvanically accelerated corrosion of the steel could increase the accumulation of corrosion damage, by either corrosion propagation through the steel or de-adhesion of the Cu coating from the steel. The goal of this research is to determine the influence of the coating process on these modes of damage accumulation when a through-coating defect is present. To simulate this scenario, Cu-coated carbon steel specimens with a small hole (0.5 mm in diameter) drilled through the coating to the Cu-steel interface are being used. Since strongly saline ground waters are possible, the specimens are exposed to 3 M NaCl solutions with various concentrations of dissolved O2. Using X-ray microtomography, a non-destructive 3D imaging technique, the progression of corrosion damage at the base of the simulated defect is being monitored both in-situ and ex-situ. The corrosion process is also being followed electrochemically by monitoring the corrosion potential and periodically recording the polarization resistance using the linear polarization technique. The potential reflects the relative rates of the chemical reactions occurring on the sample surface and the polarization resistance values reflect the changes in the overall corrosion rate. Results to date show that galvanically accelerated steel corrosion occurs, as expected, in oxygenated solutions, with the corrosion rate and distribution of damage being dependent on the dissolved O2 concentration. The corrosion behaviour also differs depending on the nature of the coating. Coatings produced by a cold spray process exhibited damage propagation along the Cu/steel interface, while electrodeposited coatings did not. Despite this difference in geometry, the overall extent of corrosion is very similar based on damage volume measurements obtained from the X-ray microtomography imaging. The long term goal of this project is to develop a computational model to determine the extent of corrosion damage which could occur on a waste container emplaced in a repository ~500 m below ground in which the redox conditions are evolving from oxic to anoxic. With this goal in mind, a finite element model (based on a COMSOL framework) is being developed to describe the galvanic corrosion process. (1) Scully, J. R.; Edwards, M. Review of the NWMO Copper Corrosion Allowance; NWMO TR-2013-04; NWMO: Toronto, ON, 2013. (2) King, F. Critical Review of the Literature on the Corrosion of Copper by Water; TR-10-69; SKB: Stockholm, Sweden, 2010.

Electrodeposition of Si Film from Water-Soluble KF-KCl Molten Salt and Feasibility of SiCl4 as a Si Source

1. Introduction Presently, Si substrate used for solar cells are manufactured by a multi-step process of production of polycrystalline Si, pulling up of single crystalline Si ingot or casting into a mold, and slicing by diamond wire saws. However, this process inevitably produces a large amount of kerf loss, which lowers the yield of the product. Thus, a direct formation of high-quality crystalline Si films on desired substrates at a low cost has been desired as a new production process of crystalline Si solar cells. For this purpose, electrodeposition in high temperature molten salts has been studied as a potential method [1,2]. Recently, we proposed a new electrodeposition process of crystalline Si in which molten KF–KCl is used as an electrolyte and SiCl4as a Si source [3]. In the present study, we first explored the optimum condition for electrodepositing compact and smooth Si films in molten KF–KCl, and then investigated the feasibility of SiCl4gas as a Si source. 2. Experimental The electrodeposition was conducted in a dry Ar atmosphere at 923 K, 1023 K or 1073 K. Reagent-grade KF and KCl were mixed to a eutectic composition (KF:KCl = 45:55 mol%, melting point = 878 K) and loaded in a graphite crucible. The crucible was placed at the bottom of a quartz or stainless steel vessel in an air-tight Kanthal container and dried under vacuum at 673 K for 24 h. A Ag plate was used as the working electrode and a glassy carbon rod as the counter electrode. A Pt wire was employed as the quasi-reference electrode. The potential was calibrated and given with reference to K+/K electrode potential. Galvanostatic electrolysis was conducted with various K2SiF6 concentrations and current densities. The electrolyzed samples were washed in hot distilled water at 333 K for 24 h to remove the adhered salt on the deposit, and dried under vacuum for 12 h. The samples were analyzed by SEM, EDX, EBSD, XRD and Raman spectroscopy. An SiCl4 gas was introduced into KF-KCl molten salt containing no K2SiF6by using argon as a carrier gas. After the introduction, cyclic voltammetry and galvanostatic electrolysis were conducted to confirm the electrodeposition of silicon. 3. Results and discussion The galvanostatic electrolysis was carried out in various current densities and K2SiF6 concentrations in a eutectic KF-KCl melt. The ionic state after the introduction of SiCl4 gas in the melt is regarded as the same with the addition of K2SiF6to the melt. SiCl4 + 6F− → SiF6 2− + 4Cl− (1) From cross-sectional SEM/EDX analysis of the samples, the optimum condition for obtaining compact and smooth Si films has been found to be the K2SiF6 concentration range of 2.0–3.5 mol% and the current density range of 50–200 mA cm−2at 923 K [4]. XRD and Raman spectrocscopy confirmed that the obtained film was crystalline Si. According to the EBSD analysis, the typical crystallite size of the deposited Si was <0.1μm at 923 K, 1–10 μm at 1023 K and 5-30 μm at 1073 K. The dependence of the crystallite size on the deposition temperature could be explained by the crystallization rate of deposited Si. In order to investigate the feasibility of SiCl4 as a Si source, 2.88 mol% of SiCl4 gas was introduced into a pure KF–KCl molten salt. After the introduction, cyclic voltammetry was performed on a Ag electrode to check the existence of Si(IV) ions. The obtained cyclic voltammogram shown in Fig. 1 indicates a couple of redox peaks which is indicative for Si(IV) ions. The concentration of Si(IV) ions is estimated to be 2.30 mol% from the height of peak current density. The sample prepared by galvanostatic electrolysis on a Ag wire at 155 mA cm-2for 30 minutes was confirmed to be a crystalline Si film. Acknowledgement This study was partly supported by the Core Research for Evolutionary Science and Technology (CREST) of the Japan Science and Technology Agency (JST). Reference [1] U. Cohen and R.A. Huggins, J. Electrochem. Soc., 123, 381 (1976). [2] D. Elwell and R.S. Feigelson, Sol. Energ. Mat., 6, 123 (1982). [3] K. Maeda, K. Yasuda, T. Nohira, R. Hagiwara and T. Homma, J. Electrochem. Soc., 162, D444 (2015). [4] K. Yasuda, K. Maeda, T. Nohira, R. Hagiwara and T. Homma, J. Electrochem. Soc., 163, D95 (2016). Figure 1

Conceptual aspects of melting unit vessel cooling by heavy liquid metal coolant

The article presents a conceptual analysis of the feasibility of lead–bismuth coolant application for cooling the melting unit steel vessel designed for implementation of a new efficient radwaste reprocessing technique. In support of the lead–bismuth coolant feasibility, the main advantages and specific features of its application are presented, taking into account significant experience acquired in Russia in handling this coolant (nuclear submarines reactor units and circulation loops), availability of job-proved methods and equipment for the coolant quality control, coolant properties ensuring fire and explosion safety and heat removal capability under high temperature and low pressure conditions. Preliminary calculated estimates were made as for temperature distributions during lead–bismuth cooling of the melting unit steel vessel. Calculations were made for the melting unit normal operation, in the presence of refractory coating and slag lining of a certain thickness formed on the vessel inner surface.Based on the results of the calculated temperature distribution estimates, it can be concluded that lead–bismuth cooling of the melting unit steel vessel in normal operation (i.e. in the presence of refractory coating and slag lining on the vessel inner surface) provides an opportunity to maintain steel surface temperatures which do not exceed the limits at an acceptable flow rate. Data presented in this article have been obtained for the first time and may be useful in designing melting units for radwaste reprocessing.

Fuel properties of the oils produced from the pyrolysis of commonly-used polymers: Effect of fractionating column

The effects of using a packed column as a fractionating system on thermal degradation of commonly-used polymers have been studied. The polymers investigated were virgin polyethylene (LDPE and HDPE), polypropylene (PP), and polystyrene (PS), as well as two post-consumer polymer mixtures, namely municipal plastic waste (MPW) and scrap tire. The experiments were carried out under atmospheric pressure in a 6L semi-batch stainless steel vessel equipped with the fractionating system. The system led to total elimination of wax formation, color improvement, and reduction in the density of the resultant pyrolysis oils. The oils were analyzed according to ASTM D86, the standard test method for boiling range distribution of petroleum fractions. The obtained values were compared to the Iran standard limits established for diesel (ISIRI4903) and gasoline (ISIRI4904). Furthermore, Fourier transform infrared spectroscopy (FT-IR) was utilized to determine the chemical composition of the oils. Finally, the spectra of the generated tire and MPW-derived oils were compared with the spectra of conventional fuels, gasoline and diesel.

Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment.

External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ∼5 ms. The addition of the external copper coils effectively increases this time to ∼7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M. C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each external coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.

Thermo-mechanical behaviour during encapsulation of glass in a steel vessel

Quantitative numerical simulations and qualitative evaluations are conducted to elucidate thermo-mechanical behaviour during pouring and solidification of molten glass into a stainless-steel cylindrical container. Residual stress and structural integrity in this casting/vitrification process is important because it can be used for long-term storage of high-level nuclear wastes. The predicted temperature and stress distributions in the glass and container agree well with previous measurements of the temperature histories and residual stresses. Three different thermal-stress models are developed using the finite-element method and compared. Two simple slice models were developed based on the generalized plane strain assumption as well as a detailed two-dimensional axi-symmetric model that adds elements according to the stages of pouring glass into the stainless steel container. The results reveal that mechanical interaction between the glass and the wall of the stainless steel container generates residual tensile stresses that approach the yield strength of the steel. Together, these results reveal important insights into the mechanism of stress generation in the process, the structural integrity of the product, and accuracy of the modelling-tool predictions.

Quick Preparation of Moisture-Saturated Carbon Fiber-Reinforced Plastics and Their Accelerated Ageing Tests Using Heat and Moisture.

A quick method involving the control of heat and water vapor pressure for preparing moisture-saturated carbon fiber-reinforced plastics (CFRP, 8 unidirectional prepreg layers, 1.5 mm thickness, epoxy resin) has been developed. The moisture-saturated CFRP sample was obtained at 120 °C and 0.2 MPa water vapor in 72 h by this method using a sterilizer (autoclave). The bending strength and viscoelastic properties measured by a dynamic mechanical analysis (DMA) remained unchanged during repetitive saturation and drying steps. No degradation and molecular structural change occurred. Furthermore an accelerated ageing test with two ageing factors, i.e., heat and moisture was developed and performed at 140–160 °C and 0.36–0.62 MPa water vapor pressure by using a sealed pressure-proof stainless steel vessel (autoclave). The bending strength of the sample decreased from 1107 to 319 MPa at 160 °C and 0.63 MPa water vapor pressure in 9 days. Degraded samples were analyzed by DMA. The degree of degradation for samples was analyzed by DMA. CFRP and degraded CFRP samples were analyzed by using a surface and interfacial cutting analysis system (SAICAS) and an electron probe micro-analyzer (EPMA) equipped in a scanning electron microscope.

Prediction of falling film evaporation on the AP1000 passive containment cooling system using ANSYS FLUENT code

AP1000 nuclear plant is an advanced pressurized reactor developed by Westinghouse Electric Company (WEC), with several passive systems applied to the plant to increase its safety. One of the main passive systems is the passive containment cooling system (PCCS), which aims to ensure the integrity of the containment and remove decay heat from the containment during postulated accidents. Film evaporation outside the steel vessel wall plays an important role for the heat removal process in the PCCS. In this study, the Eulerian Wall Film model in ANSYS FLUENT is applied to study falling film evaporation and natural convection outside the PCCS of AP1000. The thermal–hydraulic phenomena of both liquid film and gas mixture in the outside air flow path of the PCCS are analyzed. The Eulerian Wall Film model shows promising performance in modeling falling film behavior and mass transfer between liquid film and gas phase.

CORROSION OF COPPER-COATED STEEL HIGH LEVEL NUCLEAR WASTE CONTAINERS UNDER PERMANENT DISPOSAL CONDITIONS

The corrosion of high level nuclear waste containers under permanent disposal conditions can occur via a number of processes which change in importance as the environment within a deep geologic repository evolves from oxic to anoxic. The container design involves a copper coating on a steel vessel. The characteristics of these coatings are being assessed using standard analytical methods, including microscopy and electron backscatter diffraction. The corrosion processes on the surface of the coatings and at through-coating defects are also being investigated electrochemically. Although minor differences exist, the surface corrosion of cold sprayed and electrodeposited coatings generally exhibited similar corrosion behaviour to standard wrought copper. Corrosion at the base of a simulated through-coating defect in a cold-sprayed coating was found to proceed via galvanic coupling to oxygen reduction on the coating surface. Besides accumulating damage at the base of the defect, corrosion propagated along the copper/steel interface, most likely a consequence of the damage inflicted during the deposition process.

Enrichment and identification of biosurfactant-producing oil field microbiota utilizing electron acceptors other than oxygen and nitrate

Microorganisms indigenous to an oil reservoir were grown in media containing either sucrose or proteins in four steel vessels under anoxic conditions at 30°C and 8.3MPa for 30days, to enrich biosurfactant producers. Fermentation of substrate was possible in the protein-containing medium and either fermentation or respiration through reduction of sulfate occurred in the sucrose-containing medium. Growth of microorganisms led to 3.4–5.4-fold surface tension reduction indicating production of biosurfactants in amounts sufficient for enhancement of gas-driven oil recovery. Analysis of sequenced cpn60 amplicons showed that Pseudomonas sp. highly similar to biosurfactant producing P. fluorescens and to Pseudomonas sp. strain TKP predominated, and a bacterium highly similar to biosurfactant producing Bacillus mojavensis was present in vessels. Analysis of 16S rDNA amplicons allowed only genus-level identification of these bacteria. Thus, cpn60-amplicon analysis was a more relevant tool for identification of putative biosurfactant producers than 16S rDNA-amplicon analysis.

The role of material efficiency to reduce CO2 emissions during ship manufacture: A life cycle approach

Low carbon shipping research focuses on energy efficiency and mitigation measures related to operations and technology. However, reducing energy use and greenhouse gas emissions associated with a vessel’s material production receives limited attention. Material efficiency is defined as “providing material services with less material production and processing”. The current business model for ship building and breaking does not embrace fully material efficiency principles. Exploring a case study of a vessel's steel hull, this study applies a Life Cycle Assessment approach to determine the effectiveness of material efficiency to reduce CO2 emissions. When compared to Business as Usual, designing and manufacturing for 100% hull reuse provides an emissions reduction of 29% from 221,978t CO2 to 158,285t CO2; 50% reuse provides a 10% reduction (199,816t CO2). From a technical and safety perspective there remain key barriers that need addressing: a vessel’s hull would require to be designed for dismantling to improve reuse; the operation and maintenance schedule must ensure the value of the steel is retained and; data must flow between key stakeholders on the quality of the steel. Despite these challenges, progressing material efficiency would require different business models that reach out and integrate the whole supply chain. There is a need for public and privately funded demonstration projects at a range of scales and markets, to provide investors the confidence that there is retained value in the steel hull when it reaches its end-of-life.

FTIR study of ageing of γ-irradiated biopharmaceutical EVA based film

In the biopharmaceutical and biotechnological industries, disposable plastic bags are used to replace stainless steel vessels. A single-use bag is made up of a film, very often a multilayer structure, which provides good sealability of the contact layer, robustness and barrier to gas. Ethylene vinyl acetate (EVA) is one of the materials constitutive of this multilayer structure. Because these single-use plastic bags have to be sterile upon delivery, they are irradiated at doses between 25 and 45 kGy. The present work aims to investigate the effects of γ-irradiation on the surface of the multilayer film by Fourier Transform Infrared (FTIR) spectroscopy. Optical spectroscopy techniques are of great interest for chemical analysis and are used to obtain information on the composition of materials, in our present case polymers. The chemical changes are monitored over time (up to 12 months) after γ-irradiation (up to 270 kGy) using FTIR to study the composition and stability of the film. The chemometric method called Principal Component Analysis (PCA) is used to highlight the changes in shift or intensity in the oxidation zone and in the unsaturated group zone.

Experimental contribution to the corium thermodynamic modelling – The U–Zr–Al–Ca–Si–O system

During a severe accident in a nuclear reactor, extreme temperatures may be reached (T>2500K). In these conditions, the nuclear fuel may react with the Zircaloy cladding and then with the steel vessel, forming a mixture of solid–liquid phases called in-vessel corium. In the worst scenario, this mixture may penetrate the vessel and reach the concrete underneath the reactor. In order to develop the TAF-ID thermodynamic database (www.oecd-nea.org/science/taf-id) on nuclear fuels and to predict the high temperature behaviour of the corium+concrete system, new high temperature thermodynamic data are needed. The LM2T at CEA Saclay centre started an experimental campaign of phase equilibria measurements at high temperature (up to 2600K) on interesting corium sub-systems. In particular, a heat treatment at 2500K has been performed on two prototypic ex-vessel corium samples (within the U–Zr–Al–Ca–Si–O system) with different amounts of CaO and SiO2. The results show that depending on the SiO2-content, the final configuration of the samples can be significantly different. The sample with the higher CaO-content showed a dendritic structure representative of a single quenched liquid phase, whilst the sample richer in SiO2 exhibited a microstructure which suggests the presence of a liquid miscibility gap. Furthermore a new laser heating setup has been conceived. This technique allows very high temperature measures (T>3000K) limiting the interactions between the sample and the surroundings.

Neutronics studies for the design of the European DEMO vacuum vessel

The DEMO vacuum vessel, a massive water cooled double-walled steel vessel, is located behind breeding blankets and manifolds and it will be subjected to an intense neutron and photon irradiation. Therefore, a proper evaluation of the vessel nuclear heat loads is required to assure adequate cooling and, given the significant lifetime neutron fluence of DEMO, the radiation damage limit of the vessel needs to be carefully controlled. In the present work nuclear heating, radiation damage (DPA), helium production, neutron and photon fluxes have been calculated on the vacuum vessel at the inboard by means of MCNP5 using a 3D Helium Cooled Lithium Lead (HCLL) DEMO model with 1572MW of fusion power. In particular, the effect of the poloidal gap between the breeding-blanket segments on vacuum vessel nuclear loads has been estimated varying the gap width from 0 to 5cm. High values of the nuclear heating (≈1W/cm3), which might cause intense thermal stresses, were obtained in inboard equatorial zone. The effect of the poloidal gap on the nuclear heating resulted to be moderate (within 30%). The radiation damage limit of 2.75DPA on the vessel is almost met with 1cm of poloidal gap over DEMO lifetime. A comparison with Helium Cooled Pebble Bed blanket is also provided.

Rapid and repeatable methane storage in clathrate hydrates using gel-supported surfactant dry solution

Gel-supported surfactant dry solution (GDS) was prepared by mixing gelling agent, sodium dodecyl sulfate (SDS) solution, hydrophobic silica nanoparticles and air in a high speed blender. GDS has the merits of surfactant dry solution (DS) and gel-supported dry water (GDW). The stack of micron-sized GDS droplets provides abundant gas transport channels and large surface area for gas–liquid contacting. Each droplet is a micro system with active surface and gelling structure. Methane storage in clathrate hydrates using GDS was investigated in a stainless steel vessel without stirring under the condition of 5.0MPa and 273.15K. The results demonstrated that the dispersed GDS droplets could significantly enhance formation kinetics, storage capacity and storage repeatability of methane hydrate. In addition, GDS exhibited faster storage rate (4.5221m3m−3min−1) and higher storage capacity (152.23m3m−3) than GDW. Compared with SDS-DS, GDS has similar storage rate and better storage repeatability (by experiment of 9 cycles), but its storage repeatability slightly became poor and capacity decay occurred due to the agglomeration of droplets after these cycles of hydration/dissociation.

Self-Recovering Section of RPV Steel Radiation Embrittlement Kinetics as Indication of Material Smart Behavior

Influence of neutron irradiation on reactor pressure vessel (RPV) steel degradation are examined with reference to the possible reasons of the substantial experimental data scatter and furthermore -nonstandard (non-monotonous) and oscillatory embrittlement behavior. In our glance this phenomenon may be explained by presence of the wavelike recovering component in the embrittlement kinetics. We suppose that the main factor affecting steel anomalous embrittlement is fast neutron intensity (dose rate or flux), flux effect manifestation depends on state-of-the-art fluence level. At low fluencies radiation degradation has to exceed normative value, then approaches to normative meaning and finally became sub normative. Data on radiation damage change including through the ex-service RPVs taking into account chemical factor, fast neutron fluence and neutron flux were obtained and analyzed. In our opinion controversy in the estimation on neutron flux on radiation degradation impact may be explained by presence of the wavelike component in the embrittlement kinetics. Therefore flux effect manifestation depends on fluence level. At low fluencies radiation degradation has to exceed normative value, then approaches to normative meaning and finally became sub normative. As a result of dose rate effect manifestation peripheral RPV’s zones in some range of fluencies have to be damaged to a large extent than situated closely to core. Moreover as a hypothesis we suppose that at some stages of irradiation damaged metal have to be partially restored by irradiation i.e. neutron bombardment. Nascent during irradiation structure undergo occurring once or periodically transformation in a direction both degradation and recovery of the initial properties. According to our hypothesis at some stagem(s) of metal structure degradation neutron bombardment became recovering factor. Therefore self-recovering section of RPV steel radiation embrittlement kinetics is an indication of material smart behavior. As a result oscillation arise that intern lead to enhanced data scatter. Disclosure of the steel degradation oscillating is a sign of the steel structure cyclic self-recovery transformation as it take place in self-organization processes. This assumption has received support through the discovery of the similar “anomalous” data in scientific publications and by means of own additional experiments. Data obtained stimulate looking-for ways to management of the structural steel radiation stability (for example, by means of nano-structure modification for radiation defects annihilation intensification) for creation of the intelligent self-recovering material. Expected results: - radiation degradation theory and mechanisms development, - more adequate models of the radiation embrittlement elaboration, - methods and facility development for usage data of the accelerated materials irradiation for forecasting of their capacity for work in realistic (practical) circumstances of operation, - search of the ways for creating of the stable under neutron irradiation self-recovery smart materials.

Electrochemical Oxygen Reduction Activity of Cobalt-Nitrogen-Carbon Composite Catalyst Prepared by Single Precursor Pyrolysis under Autogenic Pressure

The synthesis of high surface area nitrogen doped carbonaceous catalyst was performed by employing a simple and unique RAPET (Reaction under Autogenic Pressure at Elevated Temperature) method. RAPET procedure involves the utilization of reactive gases formed during the pyrolysis of unsupported cobalt phthalocyanine (CoPc) in a closed stainless steel vessel without the flow of any gases from external source, temperatures of 900°C and estimated pressure of 2.5 × 107 Pa. X-ray diffraction patterns and XPS of CCoPc-900 (CoPc heat treated at 900°C by RAPET) indicate the formation of metallic phases of cobalt. These materials are found to catalyze oxygen reduction reaction (ORR) in alkaline solution. CCoPc-900 exhibited an improved electroactivity toward ORR in comparison to CCoPc-700 (CoPc heat treated at 700°C by RAPET) and CCoPc-900-OV (CoPc heat treated at 900°C in an open vessel under nitrogen flow). The oxygen reduction in the above-said carbonized materials proceeds through the formation of hydrogen peroxide followed by further reduction to water. Using RRDE (rotating ring disk electrode) experiments, we show that the ORR kinetics on CCoPc-900 is marginally better than CCoPc-900-OV.

Decreasing Thermal Stresses in Steam Generator Collector Weld's Area Using External Cooling

Numerous WWER-440 steam generators showed a very serious problem of cracking in weld joints which are connecting primary collectors to the steam generator's vessel. As a cause of this cracking was determined stress corrosion cracking mechanism. The weld is connecting austenitic steel collector to the carbon steel vessel, so it is a dissimilar metal weld. There are two approaches how to lower the possibility of stress corrosion cracking in the weld. First one is to improve the secondary water chemistry in the weld's surrounding to stop the corrosion and second one is to decrease presented stresses in weld's area. It is better to combine both approaches. This paper deals with the second approach of possibilities to decrease presented stresses. Inspired by Russian study of external cooling on WWER-1000 steam generators, it was an attempt to adapt the external cooling idea on the WWER-440 steam generators and their problem of weld cracking. It was shown that by using the external cooling it is possible not just lower the presented tensile stresses but to change the tensile stresses into compressive stresses. This will of course result in significant reduction of stress corrosion cracking possibility in the steam generator primary collector weld's area.

The Urgent Compelling Need to Swap on a Global Scale from Indirect Mouse Calorimetry (IMC) Towards Direct Mouse Calorimetry (DMC) in Determining the Basal Metabolic Rate (BMR): A Principle of Proof Study

Mouse models are important in Biomedical- and Life Sciences. Recently it has been stated that the genetically engineered mouse models for contemporary Obesity and/or Type-2 diabetes (DM2) will in most cases deliver heavily metabolically abnormal animals due to changed gut microbiotics with increased anaerobic CO2 production. Therefore, it can be questioned if indirect calorimetry which it at this moment “the golden standard” in all mouse laboratories over the world, still can be practiced because it is dependent on the conversion factor Respiratory-Quotient (RQ-value: CO2/O2) for expressing energy expenditure into Heat production (HP) in [mW]. Direct calorimetry, however, can accurately quantify HP and thus Basal Metabolic Rate (BMR) in both metabolically normal and abnormal states. In this first manuscript we determined physical properties and characteristics of a former aquatic flow-through twin detection Setaram calorimeter used for measuring Basal Metabolic Rate of fish under adverse environmental conditions (anoxic-, hypoxic-, acid- environmental water). Our objective of this study was to determine if this Setaram calorimetric system with stainless steel vessel of 1 liter could be used in the physical medium air in order to measure energy expenditure in mouse models. This first [Technical note] describes the physical properties and characteristics in the medium water and air of this calorimetric set up. Characteristics of the calorimetric system in air were for the initial baseline over 80 minutes a heat flow of 13.44 ± 1.611 (mW) and for the end baseline over 175 minutes 14.95 ± 1.79 (mW) so the A¢ÂˆÂ†-Baseline (initial –end) was 13.44-14.95 = -1.51 (mW). The drifting baseline over the total experiment of 33h was (14.95 / 13.44) * 100% = 1.1124% with a drifting baseline per hour was 0.035 % per hour which are common values for twin detection Calvin calorimeters. We calculated based on the heat transfer characteristics from water to stainless steel (aquatic calorimeter) in combination with the specific heat capacity of water Cp-water of 4,1884 [kJ K-1] vs Cp-air is 0.001293 [kJ K-1] an aquatic time-constant τwater of 30.48 min vs τair or = 0.019605 min. Because the τair was so small deconvolution techniques (earlier successfully applied in water), correcting for the lag time of the system had no effect. This study also includes the first successful “principle of proof” pilot-experiment with one single mouse locked up for ≈ 14 h proves that measuring the energy expenditure with a single mouse in the 1 liter stainless steel calorimetric vessel in the medium air corresponds to measured values of wild strain mouse used in indirect calorimetry (IMC) (of ≈10 mW/g). A precondition was that in order to prevent suffocating of the mouse in the one liter vessel both vessel (Measurement and Reference: twin detection measurement were supplied with one liter of air per minute- with this former aquatic flow-through twin detection Setaram calorimeter. Although there is in Bio-calorimetry a switch to cell-, (sub)cellular, molecular and biomolecular interactions, this study with “whole animal” calorimetry proves that at the organismal level important fundamental questions are still unanswered and open related to the pathogenesis of human diseases like Obesity and metabolic related disorders like Type-2 Diabetes and more fundamental Life Sciences related processes like ‘ageing’. In addition, also the research area of nutraceuticals can be tested with DMC.

EXPERIMENTAL INVESTIGATION OF POSSIBLE USE OF HDPE AS THERMAL STORAGE MATERIAL IN THERMAL STORAGE TYPE SOLAR COOKERS

Many Phase Change Materials (PCMs) have been investigated by researchers. They reported limitations of PCMs for use in the thermal storage systems, some of them are: high volumetric change in the PCM while undergoing phase change and low thermal conductivity of the PCMs. Literature survey shows that High Density Polyethylene (HDPE) has relevant thermal properties and can be used as PCM. To investigate the possible use of HDPE in the thermal storage type solar cookers. The simple thermal storage device cum cooking device was designed with two stainless steel utensils easily available in the market. Use of HDPE as the PCM in the thermal storage will eliminate the problem of volumetric change as it has low volume change property during phase transition. To eliminate problem of low thermal conductivity rectangular brass fins were used in the design. Bottom of smaller stainless steel vessel (cooking cavity) was brazed with rectangular brass fins in radial manner with roughly equal angular spacing. HDPE was filled in the void space between cooking cavity with fins and outer stainless steel vessel. The device was then tested for heating, cooling and cooking. The results obtained and conclusions drawn from the experimentation are enlisted in this paper.