scholarly journals On the control of coolant parameters in long-life facilities

2020 ◽  
Vol 6 (3) ◽  
pp. 137-141
Author(s):  
Yury G. Cherednichenko ◽  
Oleg E. Levin
Keyword(s):  
Oxygen Content ◽  
Temperature Region ◽  
Power Plants ◽  
Oxidation Potential ◽  
Oxygen Activity ◽  
Maximum Temperature ◽  
Pure Lead ◽  
Oxidation Potentials ◽  
Dissolved Oxygen Control ◽  
Long Life

When nuclear power plants with heavy coolants are brought to operating mode as well as during their operation, it is necessary to control and maintain the oxygen content in the coolant within the specified limits. As a rule, the oxygen content in metal melts is controlled by sensors based on solid oxygen-ionic electrolytes. The article presents an analysis of the methodological aspects of dissolved oxygen control in non-isothermal circulating loops with metal coolants, using such sensors. It is shown that in the presence of dissolved loop wall materials and suspensions of their various oxides in the coolant, control over the values of the oxygen activity and concentration calculated for a pure coolant is in general unjustified. The authors present the experimental results of the distribution of oxidation potentials along the loop depending on the coolant temperature, obtained during long-term tests of cladding samples in a lead melt in two circulation facilities – SM2-M and TsU1-M – which differ in principal methods for maintaining specified oxygen conditions. In the low temperature region, the experimental values of the oxidation potential in both facilities are lower than those calculated for pure lead, which leads to a difference by two or more times of the calculated oxygen concentrations for the regions of the loop with Тmin and Тmax, i.e., the so-called oxygen ‘non-isoconcentration’ is observed along the loop. In deoxidation mode during hydrogen ejection into the coolant, the oxidation potential in the loop changes in a complex way, and it makes no sense to talk about the oxygen concentration. It is concluded that in long-life facilities, the coolant parameters for oxygen must be controlled not by the calculated oxygen activity or concentration but by the oxidation potential in the maximum temperature region. To obtain the correct values of the oxidation potential, measurements should be carried out in temperature-stable modes of throughout the facility.

Effects of Doping on the Electrochemical and Electrical Properties of Poly(2,5-di(2-thienyl)pyrrole)

1999 ◽  
Vol 64 (8) ◽  
pp. 1357-1368 ◽  
Author(s):  
Enric Brillas ◽  
José Carrasco ◽  
Ramon Oliver ◽  
Francesc Estrany ◽  
Víctor Ruiz
Keyword(s):  
Mass Spectrometry ◽  
Fast Atom Bombardment ◽  
Oxidation Potential ◽  
Ethanolic Solution ◽  
Pt Electrode ◽  
Reversible Process ◽  
Oxidation Potentials ◽  
Lower Productivity ◽  
Polymeric Chains ◽  
Linear Molecules

The electropolymerization of 2,5-di(2-(thienyl)pyrrole) (SNS) on a Pt electrode from ethanolic solution with LiClO4 or LiCl as electrolyte has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). In both media, a quasi-reversible process has been indicated by CV, reversing the scan at low oxidation potentials. Under these conditions, reducible positive charges formed in both oxidized polymers are compensated by the entrance of anions from solution. Elemental analysis reveals that polymers generated at a low oxidation potential by CA contain a 21.03% (w/w) of ClO4- or a 9.56% (w/w) of Cl-. The poly(SNS) doped with Cl- presents higher proportion of reducible positive charges, higher polymerization charge and lower productivity. A much higher electrical conductivity, however, has been found for the poly(SNS) doped with ClO4-. Both polymers are soluble in DMSO, acetone and methanol. The dimer, trimer, tetramer and pentamer have been detected as soluble and neutral linear oligomers by mass spectrometry-fast atom bombardment. The analysis of polymers by infrared spectroscopy confirms the predominant formation of linear molecules with α-α linkages between monomeric units. A condensation mechanism involving one-electron oxidation of all electrogenerated linear and neutral polymeric chains is proposed to explain the SNS electropolymerization.

An Assessment of the Performance of Closed Cycles With and Without Heat Rejection at Cryogenic Temperatures

1996 ◽  
Author(s):  
A. Agazzani ◽  
A. F. Massardo ◽  
T. Korakianitis
Keyword(s):  
Heat Exchangers ◽  
Power Plants ◽  
Cycle Performance ◽  
Maximum Temperature ◽  
Specific Work ◽  
Cryogenic Temperatures ◽  
Temperature Minimum ◽  
Thermodynamic Performance ◽  
Cycle Systems ◽  
Near Term

This paper presents optimized cycle performance that can be obtained with systems including a Closed Cycle Gas Turbine (CCGT). The influence of maximum temperature, minimum temperature and recuperator effectiveness on cycle performance is illustrated. Several power-plant arrangements are analyzed and compared based on: thermodynamic performance (thermal efficiency and specific work); enabling technologies (available at present); and developing technologies (available in the near term or future). The work includes the effects of utilization of high temperature ceramic heat exchangers and of coupling of CCGT systems with plants vaporizing Liquid Hydrogen (LH2) or Liquefied Natural Gas (LNG). Given the versatility of energy addition and rejection sources that can be utilized in closed gas-cycle systems, the thermodynamic performance of power plants shown in this paper indicate the remarkable capabilities and possibilities for closed gas-cycle systems.

scholarly journals Temperature conditions in the RBMK spent fuel pool in the event of disturbances in its cooling mode

2021 ◽  
Vol 7 (1) ◽  
pp. 9-13
Author(s):  
David A. Hakobyan ◽  
Victor I. Slobodchuk
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Spent Nuclear Fuel ◽  
Maximum Temperature ◽  
Spent Fuel ◽  
Cooling Mode ◽  
Temperature Conditions ◽  
Fuel Assemblies ◽  
Spent Fuel Pool

The problems of reprocessing and long-term storage of spent nuclear fuel (SNF) at nuclear power plants with RBMK reactors have not been fully resolved so far. For this reason, nuclear power plants are forced to search for new options for the disposal of spent fuel, which can provide at least temporary SNF storage. One of the possible solutions to this problem is to switch to compacted SNF storage in reactor spent fuel pools (SFPs). As the number of spent fuel assemblies (SFAs) in SFPs increases, a greater amount of heat is released. In addition, no less important is the fact that a place for emergency FA discharging should be provided in SFPs. The paper presents the results of a numerical simulation of the temperature conditions in SFPs both for compacted SNF storage and for emergency FA discharging. Several types of disturbances in normal SFP cooling mode are considered, including partial loss of cooling water and exposure of SFAs. The simulation was performed using the ANSYS CFX software tool. Estimates were made of the time for heating water to the boiling point, as well as the time for heating the cladding of the fuel elements to a temperature of 650 °С. The most critical conditions are observed in the emergency FA discharging compartment. The results obtained make it possible to estimate the time that the personnel have to restore normal cooling mode of the spent fuel pool until the maximum temperature for water and spent fuel assemblies is reached.

Dynamics of the transient species generated upon photolysis of diarylmethanes within zeolites — Deprotonation and oxidation reactions

2005 ◽  
Vol 83 (9) ◽  
pp. 1637-1648 ◽  
Author(s):  
Suzanne Shea ◽  
Norman P Schepp ◽  
Amy E Keirstead ◽  
Frances L Cozens
Keyword(s):  
Radical Cation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Cations ◽  
Laser Flash ◽  
Oxidation Potential ◽  
Oxidation Reactions ◽  
Oxidation Potentials ◽  
Multistep Process ◽  
Acid Zeolites

The oxidation of diarylmethanes is a multistep process involving initial formation of a radical cation, deprotonation of the radical cation to the radical, and oxidation of the radical to the carbocation. The dynamics and efficiency of the last two steps in this process, namely deprotonation and oxidation, in acidic zeolites and non-acid zeolites are examined in the present work as a function of the acidity of the diarylmethane radical cations and the oxidation potential of the diarylmethyl radicals. Our results indicate that rate constants for deprotonation strongly depend on the acidity of the radical cations, but not on the composition of the zeolites. In addition, oxidation of the radicals to the diarylmethyl cations is strongly dependent on both the oxidation potential of the radicals and the oxidizing ability of the zeolite. This dependence allows oxidation potentials of the zeolites to be estimated.Key words: radical cations, carbocations, zeolites, laser flash photolysis.

scholarly journals Uncertainty Analysis of Method-Based Operating Event Groups Ranking

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Zdenko Šimić ◽  
Benoit Zerger ◽  
Reni Banov
Keyword(s):  
Analytical Hierarchy Process ◽  
Nuclear Power ◽  
Power Plants ◽  
Technology Development ◽  
Uncertainty Assessment ◽  
Operational Experience ◽  
Safe Operation ◽  
Industrial Facilities ◽  
Long Life ◽  
Hierarchy Process

Safe operation and industrial improvements are coming from the technology development and operational experience (OE) feedback. A long life span for many industrial facilities makes OE very important. Proper assessment and understanding of OE remains a challenge because of organization system relations, complexity, and number of OE events acquired. One way to improve OE events understanding is to focus their investigation and analyze in detail the most important. The OE ranking method is developed to select the most important events based on the basic event parameters and the analytical hierarchy process applied at the level of event groups. This paper investigates further how uncertainty in the model affects ranking results. An analysis was performed on the set of the two databases from the 20 years of nuclear power plants in France and Germany. From all uncertainties the presented analysis selected ranking indexes as the most relevant for consideration. Here the presented analysis of uncertainty clearly shows that considering uncertainty is important for all results, especially for event groups ranked closely and next to the most important one. Together with the previously performed sensitivity analysis, uncertainty assessment provides additional insights and a better judgment of the event groups’ importance in further detailed investigation.

Corrosion Properties of Plasma Oxidized Titanium Nitride for Biomedical Applications

2015 ◽  
Vol 227 ◽  
pp. 471-474 ◽  
Author(s):  
Jerzy Robert Sobiecki ◽  
Agnieszka Brojanowska ◽  
Konrad Kowalczyk
Keyword(s):  
Titanium Nitride ◽  
Calcium Ions ◽  
Biomedical Applications ◽  
Oxidation Potential ◽  
Plasma Oxidation ◽  
Corrosion Properties ◽  
Oxide Layers ◽  
Oxidation Processes ◽  
Oxidation Potentials ◽  
Electrolytic Plasma Oxidation

The article compares the corrosion properties of oxide layers formed on titanium nitride (obtained in glow-discharge nitriding) using electrolytic plasma oxidation. The corrosion properties are analysed in correlation with the surface morphology, microstructure and chemical composition of the layers. The oxidation processes were carried out in 10% and 25% phosphoric acid (V) solutions containing Ca2+ calcium ions. In each of these environments, oxide layers were formed using three oxidation potentials: 200V, 400V and 600 V. The oxidation potential and the concentration of acid and calcium ions in the oxidation solution was shown to affect the morphology of the surface and the corrosion properties of the oxide layers obtained.

scholarly journals CFD Analysis of the Cool Down Behaviour of Molten Salt Thermal Storage Systems

2008 ◽  
Author(s):  
Jan Schulte-Fischedick ◽  
Rainer Tamme ◽  
Ulf Herrmann
Keyword(s):  
Molten Salt ◽  
Power Plants ◽  
Thermal Power ◽  
Side Wall ◽  
Heat Losses ◽  
Maximum Temperature ◽  
Bottom Plate ◽  
Computational Fluid Mechanics ◽  
Cfd Analysis ◽  
Maximum Temperature Difference

CFD analysis has been conducted to obtain information on heat losses, velocity and temperature distribution of large molten salt Thermal Energy Storage (TES) systems. A two-tank 880 MWh storage system was modeled according to the molten salt TES containment design proposed for the 50 MWel commercial parabolic trough solar thermal power plants in Spain. Heat losses were established using the Finite Element Method (FEM), and used to determine the boundary conditions for the subsequent two- and three-dimensional Computational Fluid Mechanics (CFD) calculations. The investigations reveal that a high heat loss flux occurs at the lower edges of the salt storage tanks (between side wall and bottom plate). Thus the maximum temperature difference can be found at this location, resulting in the onset of local solidification within 3.25 days in the case of the empty cool tank. As a consequence, the detailed design of the lower edge has a large impact on both the overall heat losses and the period until the onset of local solidification.

scholarly journals Experimental Study on NOx Reduction in Oxy-fuel Combustion Using Synthetic Coals with Pyridinic or Pyrrolic Nitrogen

2018 ◽  
Vol 8 (12) ◽  
pp. 2499 ◽  
Author(s):  
Chang’an Wang ◽  
Pengqian Wang ◽  
Lin Zhao ◽  
Yongbo Du ◽  
Defu Che
Keyword(s):  
Oxygen Content ◽  
Power Plants ◽  
Large Scale ◽  
Nox Reduction ◽  
Fuel Combustion ◽  
Combustion Technology ◽  
Carbon Dioxide Co2 ◽  
No2 Formation ◽  
The Impact ◽  
Pyridinic Nitrogen

Oxy-fuel combustion technology can capture carbon dioxide (CO2) in the large-scale and greatly lower nitrogen oxides (NOx) emission in coal-fired power plants. However, the influence of inherent minerals on NOx reduction still remains unclear and the impact of oxy-fuel combustion on the transformation of different nitrogen functional groups has yet to be fully understood. The present work aims to obtain a further understanding of the NOx reduction during oxy-fuel combustion using synthetic coals with pyrrolic or pyridinic nitrogen. Compared to pyridinic nitrogen, more of the pyrrolic nitrogen in synthetic coal was converted to NOx. The conversion ratio of nitric oxide (NO) first increased significantly with the rising oxygen content and then trended to an asymptotically constant as the oxygen (O2) content varied between 10–50%. The nitrogen dioxide (NO2) formation was roughly proportional to the oxygen content. The NO2 conversion was increased with particle size but the case of NO showed a non-monotonic variation. The catalytic effects of sodium carbonate (Na2CO3), calcium carbonate (CaCO3), and ferric oxide (Fe2O3) on the transformation of pyridinic nitrogen to NO were independent of the combustion atmosphere, while the alteration from air to the oxy-fuel combustion led to a change of mineral catalytic effect on the oxidation of pyrrolic nitrogen within the coal matrix.

scholarly journals Numerical Study of the Axial Gap and Hot Streak Effects on Thermal and Flow Characteristics in Two-Stage High Pressure Gas Turbine

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2654 ◽  
Author(s):  
Myung Gon Choi ◽  
Jaiyoung Ryu
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Suction Side ◽  
Combined Cycle ◽  
Maximum Temperature ◽  
Two Stage ◽  
Second Stage

Combined cycle power plants (CCPPs) are becoming more important as the global demand for electrical power increases. The power and efficiency of CCPPs are directly affected by the performance and thermal efficiency of the gas turbines. This study is the first unsteady numerical study that comprehensively considers axial gap (AG) in the first-stage stator and first-stage rotor (R1) and hot streaks in the combustor outlet throughout an entire two-stage turbine, as these factors affect the aerodynamic performance of the turbine. To resolve the three-dimensional unsteady-state compressible flow, an unsteady Reynolds-averaged Navier–Stokes (RANS) equation was used to calculate a k-ω SST γ turbulence model. The AG distance d was set as 80% (case 1) and 120% (case 3) for the design value case 2 (13 mm or d/Cs1 = 0.307) in a GE-E3 gas turbine model. Changes in the AG affect the overall flow field characteristics and efficiency. If AG decreases, the time-averaged maximum temperature and pressure of R1 exhibit differences of approximately 3 K and 400 Pa, respectively. In addition, the low-temperature zone around the hub and tip regions of R1 and second-stage rotor (R2) on the suction side becomes smaller owing to a secondary flow and the area-averaged surface temperature increases. The area-averaged heat flux of the blade surface increases by a maximum of 10.6% at the second-stage stator and 2.8% at R2 as the AG decreases. The total-to-total efficiencies of the overall turbine increase by 0.306% and 0.295% when the AG decreases.

Corrosion Properties of Oxide Layers Produced on Titanium Nitride by Means of Plasma Electrolytic Oxidation of Various Duration

2015 ◽  
Vol 227 ◽  
pp. 475-478 ◽  
Author(s):  
Konrad Kowalczyk ◽  
Agnieszka Brojanowska ◽  
Jerzy Robert Sobiecki
Keyword(s):  
Titanium Nitride ◽  
Oxidation Potential ◽  
Process Time ◽  
Plasma Oxidation ◽  
Corrosion Properties ◽  
Oxide Layers ◽  
Oxidation Potentials ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
The Impact

The corrosion resistance of oxide layers produced on titanium nitride (obtained in glow-discharge nitriding) by means of electrolytic oxidation at different potentials and durations is presented in the paper. The oxidation processes were carried out in phosphoric acid (V) (25wt.%) containing Ca2+ calcium ions. Two plasma oxidation potentials of 40 V and 100 V were applied. Treatment was carried out at two different process durations, i.e. 30 minutes and 120 minutes. The impact of oxidation potential and process time on the morphology of the surface and corrosion properties of the oxide layers obtained was examined.

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