Types Of Reactors Research Articles

Research of processes of thermochemical disposal of components of the morphological composition and model analogs of MSW

The article emphasizes that processing and disposal of household waste mainly concerns large densely populated cities, where millions of cubic meters of solid household waste (MSW) are accumulated annually. It was noted that thermal methods of solid waste disposal are among the most advanced methods of their processing. The advantage of these methods is a significant reduction in the volume of processed material. When waste is burned, its weight is reduced by 85-90%. In addition to reducing the volume and mass of waste, incineration of household waste allows you to obtain additional energy resources. Indicators of the amount of heat of combustion of MSW are similar to indicators of brown coal - from 1000 to 3000 kcal/kg.
 To date, existing waste incineration plants have a number of disadvantages, the main of which is low efficiency. The rate of useful use of thermal energy does not exceed 65%, even with the use of a more advanced property.
 The combustion processes themselves, the formation and composition of ash residues are affected by a large number of factors, starting with the properties and characteristics of the fuel, the physical and chemical properties of the raw materials, the parameters of the combustion process, the dispersed size of the fuel, the type of reactor, and the level of oxygen in the working area.
 Thus, the selection of the range of temperatures and pressures, the rate of heating of the gas medium for the thermogravimetric method of disposal of carbon-containing waste plays a decisive role in overcoming the shortcomings of this method.
 The purpose of the article is the development of a thermogravitational installation for studying the peculiarities of the flow of kinetic processes during the combustion of MSW samples.
 The article presents the development of an experimental thermogravitational unit for researching processes of thermochemical processing of carbon-containing alternative fuels with wide possibilities, which allows to study the influence of technological parameters on the combustion process. A description of the main nodes and the measurement system, the methodology of the experiment and the analysis of the obtained data is given. 
 A series of experiments was conducted with all the main components of solid waste: wood, food waste (potatoes, meat), office and chart paper, leather, garden waste, tetrapak, plastic. It is shown that the nature of the mass change curves of various components practically does not depend on their chemical composition and is determined mainly by the staged course of the combustion process, and the latter, in turn, by the rate of heating of the sample, the only exception being the combustion of plastic. The oxidation time of all components, except plastic, after reaching the temperature of the beginning of combustion (~ 200-250, sometimes 300 °С) is from 5-7 to 40-50 minutes, while the intensive combustion of plastic ends in 1 minute. 
 It was determined that the composition and thermophysical properties of ash play an important role in the processes of thermochemical disposal of MSW, affecting the value of the specific calorific value of MSW as a fuel and the value of the adiabatic temperature of the gaseous products of the process.

Estimation of the effective length of microcracks occurring in the water-steam pipeline at cyclic operation mode of NPP steam generator

During operation of water-water reactors including KLT-40 type reactors widely used nowadays on icebreakers and floating power units (FPU), the issue of the duration of safe operation of steam generators is acute. The problem is connected with the formation of microcracks in the steam generator water and steam piping during normal operation at power, through which radioactive nitrogen 16N7 enters the steam piping, the content of which in the steam is just a sign of leakage failure of the steam generator second circuit water and steam piping. This effect, further named "leaks", was considered earlier in a number of works of the authors under conditions of cyclic operation of the steam generator water-steam mode. In the present work the main attention is paid to mathematical and physical analysis of the mechanisms causing the formation of microcracks in the steam pipeline of a steam generator arising in the steam pipeline region in which water and steam pressures are balanced, and their effective length is estimated. Calculations of temperature distribution along the steam-pipe thickness in the steam-water transition region at periodic "slamming" of this region with water are carried out. It is shown that depending on the time period of steam-water oscillations, the radial temperature distribution along the tube thickness shows a significant difference in the distribution at a constant temperature on the outer surface of the tube, and the maximum temperature difference is observed in the area of the inner surface of the tube. The distribution of mechanical stresses arising in the tube metal is characterized by a linear dependence of stresses on temperature, the maximum value of which corresponds to the maximum temperature difference characteristic of the area of the inner surface of the tube. This allows us to state that the formation of cracks starts exactly from the area of the inner surface of the tube of the steam generator in the specified transitional area of the tube.

Studies on the Thermochemical Conversion of Waste Tyre Rubber—A Review

Waste from scrap tyres, due to its high volume (17 million Mg per year) and durability resulting from the physical and chemical properties, requires innovative approaches for efficient and environmentally friendly management. In many countries, the landfilling of waste tyres is banned (e.g., EU, USA, UK); however, waste tyres can be a source of valuable materials such as carbon black, pyrolysis oil, hydrogen-rich syngas, tyre char, as well as energy. The purpose of this article is to provide a synthesis of the state of knowledge regarding the thermal conversion of waste tyres by pyrolysis and gasification, taking into account the use of different measurement techniques and reactor types. These technologies are forward-looking and have a high degree of flexibility in terms of product sourcing, depending on the process conditions. The properties of waste from used tyres were analysed, i.e., the composition of the content of individual components and the main chemical substances. The results encompassed ultimate and proximate analyses of rubber from tyres, as well as the physical and chemical parameters of the tyre char obtained through pyrolysis. This article compiles available literature data regarding the impact of process and raw material parameters, such as temperature and time conditions, pressure, particle size, and catalyst addition on the pyrolysis and gasification processes. It also explores the influence of these factors on the yield and properties of the products, including pyrolysis oil, gas, synthesis gas, and tyre char.

Biooxidation of refractory silver minerals as pretreatment for silver recovery

The worldwide demand for silver is increasing due to the technological development in different areas, especially for the requirements in the production of renewable energies; therefore, for the treatment of refractory minerals by conventional processes, it is necessary to study mechanisms to identify the viability of their processing and the feasibility of their recovery, ensuring profitability. Gold and silver present in the matrix of sulfide-based ores are not affordably recovered by the conventional method involving leaching in sodium cyanide solution. Therefore, it must be subjected to oxidation pretreatment or conversion of the sulfides to simple compounds that allow recovery of the precious metals. The methods of oxidation of minerals considered refractory are carried out by hydro and pyrometallurgical methods, seeking the dissolution of sulfur, iron, arsenic and other elements present. It is important to identify and consider the mineralogical structure, microbiological variety, physicochemical characteristics, types of reactors, bacterial interactions, among other factors. The choice of biooxidation as the preferred process in projects for the recovery of gold, silver, copper or other metals, in most cases is based on the economic advantage, compared to the conventional processes of roasting, chemical leaching and pressurized leaching. The biooxidation of refractory argentiferous ores has been extensively studied in recent years, concluding that its application is feasible, mainly because it is environmentally friendly.

Low-Density Polyethylene – New insights into an old material under comparative studies using SEC-MALS, AF4-MALS, HT-HPLC and 2D-LC

LDPE can be produced by different types of autoclave or tubular reactors, which can also be cascaded. An important effort is to obtain materials with autoclave-process equivalent properties from tubular technology due to economic reasons. In this way, the molecular understanding of the materials attains a key role. Five LDPE materials were characterized, covering three applications (extrusion coating, blow molding, and film blowing) as well as three reactor technologies (type I autoclave, tubular type, and type II autoclave). SEC-MALS, SEC-IR, AF4-MALS, HPLC, and 2D-LC allowed a detailed characterization of the samples’ molar mass and branching structure while providing a unique opportunity for technique comparison. This allowed for an unprecedented understanding of the differences in molecular structure and the influence of application vs. reactor technology driven differences.Overall, SEC-IR-MALS was found to provide the most versatile information, making it an excellent choice for an initial characterization. Furthermore, the results indicate that the intended application (and thus property profile) influences LDPE structure much more than reactor technology. All five studied samples exhibit differences in molar mass distribution, short-chain as well as long-chain branching. Yet, the three extrusion coating samples (each derived from a different reactor type) appeared notably similar to each other with regard to each parameter.

Preliminary analysis of the irradiation deformation of a typical molten salt reactor graphite component

Nuclear graphite commonly serves as the moderator and constructs the coolant flowing channel in liquid fuel molten salt reactors. Under irradiation and high temperature, graphite components will experience obvious deformation due to irradiation creep, thermal expansion, dimensional change, elastic deformation, and thermo-mechanical properties change. The lifespan of graphite components is a limiting parameter of liquid fuel molten salt reactors, determining by the deformation of the graphite components. An improved approach based on the finite element method for graphite deformation analysis was proposed in this paper. Then this method was utilized to analyze a 10-year deformation history of a typical graphite component. The findings show that the stress-strain field of the graphite component significantly varies with the increasing irradiated neutron fluence. The dimensional change plays a primary role in influencing the deformation of the graphite components, determining the overall deformation trend. The irradiation creep plays a secondary role in influencing the deformation, alleviating the deformation of the graphite components to prolong the graphite lifespan. The improved method, which considers various factors like irradiation creep, thermal expansion, dimensional change, and elastic deformation, tends to provide more accurate results compared to the traditional method that focuses solely on the dimensional changes. Over 10 years, the contraction deformation of graphite components results in a reduction in graphite volume of up to 3.87%. The space for graphite contraction is filled with molten salt, resulting in a maximum increase of 22.49% in fuel volume. The alteration in volume of both graphite and fuel leads to a reduction in reactivity of up to 840 pcm.

Development of supporting platform for the fine flow characteristics of reactor core

This study presents the Supporting platform for reactor fine flow characteristics calculation and analysis (Cilian platform), a user-friendly tool that supports the analysis and optimization of pressurized water reactor (PWR) cores with mixing vanes using computational fluid dynamics (CFD) computing. The Cilian platform allows for easy creation and optimization of PWR's main CFD calculation schemes and autonomously manages CFD calculation and analysis of PWR cores, reducing the need for human and computational resources. The platform's key features enable efficient simulation, rapid solution design, automatic calculation of core scheme options, and streamlined data extraction and processing techniques. The Cilian platform's capability to call external CFD software reduces the development time and cost while improving the accuracy and reliability of the results. In conclusion, the Cilian platform exemplifies an innovative solution for efficient computational fluid dynamics analysis of pressurized water reactor (PWR) cores. It holds great promise for driving advancements in nuclear power technology, enhancing the safety, efficiency, and cost-effectiveness of nuclear reactors. The platform adopts a modular design methodology, enabling the swift and accurate computation and analysis of diverse flow regions within core components. This design approach facilitates the seamless integration of multiple computational modules across various reactor types, providing a high degree of flexibility and reusability.

Analytical dependence of burnup on enrichment of prospective fuel and parameters of reactors fuel campaign

The paper is devoted to the definition of an analytical expression for estimating the burnup depth of nuclear fuel depending on its enrichment level, the periodicity of refueling, thermal stressthermal stress and the duration of the time period between refueling (reactor campaign) in a wide range of changes in key parameters for different types of thermal neutron reactors. The analytical expressions obtained in the work for the burnup depth are compared with numerous neutron physics calculations and experimental data from different authors for uranium fuel enrichment up to 9%. Calculations of the fuel share of the cost of electricity of nuclear power plants with PWR type reactors were performed and its sensitivity to changes in burnup depth and enrichment of fuel, the refueling periodicity, as well as to market prices for natural uranium, conversion, enrichment, fabrication of fuel assemblies and SNF handling were determined.

Self-inducing Reactors for Bioengineering.

Packed tower reactors, mechanically stirred reactors, airlift reactors, and gas-self-inducing reactors are frequently utilized among the various types of reactors. Self-inducing reactors exhibit notable advantages owing to their simple structure, effective gas-liquid intermixing, and low energy requirements, rendering them highly suitable for bioengineering endeavors. The purpose of this analysis is to shed light on the use of self-inducing reactors in bioengineering by examining the following five parameters: critical speed, suction rate, volumetric mass transfer coefficient, power characteristics, and gas hold-up. Through a comprehensive analysis of the advancements achieved in these domains, it is possible to determine the challenges and opportunities that lie ahead in the realm of bioengineering.

Accelerated Formation of Oxide Layers on Zircaloy-4 Utilizing Air Oxidation and Comparison with Water-Corroded Oxide Layers.

For the dry storage of Canada Deuterium Uranium (CANDU) spent nuclear fuels, the integrity of Zircaloy-4 fuel cladding has to be verified. However, the formation of ~10 µm-thick oxide layers in typical CANDU reactor operating conditions takes several years, which makes sample preparation a slow process. To overcome such limitations, in this study, an accelerated formation of an oxide layer on Zircaloy-4 cladding tube was developed with a combination of high-temperature water corrosion (HT-WC) and air oxidation (AO). First, Zircaloy-4 tubes were corroded in oxygenated (2 ppm dissolved oxygen) high-temperature water (360 °C/19.5 MPa) for 500 h. Then, the tubes were air-oxidized at 500 °C for 30 h. Finally, the tubes were corroded again in HT-WC for 500 h to produce ~10 µm-thick oxide layers. The morphology and characteristics of the oxide layer in each step were analyzed using X-ray diffraction, scanning and transmission electron microscopy. The results showed that the oxide layer formed in the accelerated method was comparable to that formed in HT-WC in terms of morphology and oxide phases. Thus, the accelerated oxide formation method can be used to prepare an oxidized Zircaloy-4 cladding tube for CANDU fuel integrity analysis.

The role of risk-informed approaches for advanced reactors in Korea

Currently, various types of advanced reactors are being developed in the Republic of Korea, including (1) advanced large power reactors, (2) light water–based small and modular reactors, and (3) Generation IV reactors. While Probabilistic Safety Assessments (PSAs) have been performed for these advanced reactors in Korea, the PSAs were not conducted in detail since they were not regulatory requirements in many cases. However, the role of PSA is changing in Korea nowadays, and qualified PSA models have recently become an essential element in the licensing of operating and new reactors. In addition, PSAs for advanced reactors are essential not only to meet regulatory requirements but also to improve the safety and performance of advanced reactors. It can be said that the success of advanced reactors depends on how their safety and economics can be secured effectively and efficiently. The PSA will play an essential role in this aspect. Various risk-informed approaches (RIAs) based on PSAs are used in many countries worldwide for this purpose. A few issues remain to be resolved for the success of PSAs and RIAs for advanced reactors, such as the development of licensing frameworks for advanced reactors, the reliability assessments of passive safety systems, and so on. In this paper, we introduce the current status of PSAs and RIAs for advanced reactors, including descriptions regarding the characteristics of advanced reactors currently being developed in Korea. We also discuss some important issues to be resolved for the success of RIAs for advanced reactors. We also briefly introduce some research performed to resolve those issues.

Biowaste valorization on pharmaceuticals and pesticides abatement in aqueous environments

This study focuses on the abatement of pharmaceuticals and pesticides in water using sustainable biosorbents. Adsorption kinetics and equilibrium measurements were performed to characterize the adsorption of fluoxetine hydrochloride (FLX), carbamazepine (CRB) and atrazine (ATZ) by raw pine bark. The amount of adsorbed pollutants by mass of adsorbent followed the order: FLX (0.652 mg/g) > ATZ (0.522 mg/g) > CRB (0.144 mg/g), explained by the different interactions between the untreated pine surface and the target pollutants, according to the adsorption mechanism proposed. The evaluation of chemically and thermically modified pine was also assessed. In terms of the overall entrapment capability, pine bark modified with HNO3 was shown to be the best biosorbent (1.95 mg/g). The economic feasibility of the biosorbents was evaluated through a detailed cost analysis. Among the performed modifications, the one with H2O2 was the most expensive procedure, 23.7 €/mmol (pollutants mixture) being the hydrochar production the less expensive, 1.1 €/mmol. Through desorption assays it was found that 100% of FLX, 98% of CRB and 30% of ATZ, respectively, can be recovered from raw pine, using 50% (v/v) acetonitrile solution. The recyclability of the natural biosorbent was evaluated by adsorption-desorption cycles. Pine bark can be regenerated and reused at least for two times, without losing its adsorption efficiency. A pre-pilot air-lift type reactor was investigated as an effective rehabilitation approach to treat contaminated water, for up-scale purpose. Using biowastes for emerging pollutants entrapment can be considered a sustainable water rehabilitation pathway, promoting a circular bioeconomy and environmental protection.

A comparative numerical investigation of the thermal-fluid phenomena between helium and nitrogen cooled pebble bed reactors

The study assesses the thermal-hydraulic performance of a pebble bed type nuclear reactor using nitrogen and helium as coolants. The analysis is done in two separate parts using CFD. First, a segment of the pebbles is modeled and later the whole reactor core. The study assesses the core performance under normal and after reactor shutdown conditions using these two different coolants. The assessment concludes that nitrogen as a coolant candidate for PBR behaves in an acceptable manner in both conditions at a cost of increased pumping power consumption. It is found that under steady state conditions, the heat stored in the pebbles (both for the segment and the whole core) is more in the case of the nitrogen cooled bed compared to the helium cooled bed.

Measurement of leakage neutron flux from reactor tank surface of AHWR-critical facility

AHWR - Critical Facility (AHWR - CF) is a “zero power” reactor designed to carry out various reactor physics experiments for validation of AHWR physics design. AHWR-CF is a vertical tank type reactor. This paper describes the experiments carried out for neutron flux measurements on the reactor tank surface of AHWR-CF. A number of bare Au and cadmium covered Ni foils were used to measure thermal and fast neutron flux at the outer surface of the reactor tank. One cadmium covered Au foil was also irradiated at one of the locations on the tank surface, to estimate the epithermal component of neutron flux. Westcott thermal flux on the tank surface (at an elevation of 120 cm from tank bottom) was found to be (5.48 ± 0.57)E+6 n cm−2 s−1 on one of the sides of the reactor tank. Cadmium ratio for Au for this location was 40.28, indicating a highly thermalized neutron spectrum. No statistically significant activity was found in the irradiated Ni foils, indicating the absence of fast neutron flux above the measurable threshold. Low value of flux on the reactor tank surface implies that any irradiation damage in the AHWR-CF reactor tank material will be insignificant over its period of operation.

Exploring a novel tubular-type modular reactor for solar-driven thermochemical energy storage

Thermochemical energy storage (TCES) has gained extensive attention as a potential solution to address the mismatch between solar thermal energy production and demand. In this study, a novel tubular-type modular TCES reactor is introduced. COMSOL modelling of the system is developed and experimentally validated using a laboratory-scale TCES system. Both types of reactors show similar temperature increases, intensifying with higher inlet relative humidity. Their maximum temperature lifts exceeding 26 °C at 90 % RH. Tubular designs offer better axial flexural strength and dispersion of TCES composite materials compared to plate structures. This property of tubular structures beneficial reducing bed thickness and pressure drop and enhancing equivalent thermal efficiency. Simulations show tubular-type modular reactors reduce pressure drop by 4–5 times compared to plate-type modular reactors, increasing equivalent thermal efficiency by nearly 7% points. Increasing the number of reactor beds and inner tube radius improves equivalent thermal efficiency due to reduced bed thickness and pressure drop. As the number of matrix rows and columns in the reactor bed increases from 2 to 10, bed thickness decreases from 0.058 m to 0.012 m, reducing pressure drop from 845.53 Pa to 38 Pa and increasing equivalent thermal efficiency from 78.82 % to 96.61 %.

Advancements in CO2 methanation: A comprehensive review of catalysis, reactor design and process optimization

Renewable electricity, production/storage and distribution of green hydrogen and carbon dioxide emission reduction are just three of the practices needed for a net zero-emission world. The increasing amount of renewable energy produced requires the development of versatile technologies capable to store the excess renewable electricity produced. Hydrogen production through electrolysis, despite not being still economically viable, can be considered a mature technology. Different strategies to convert H2 into more volumetric dense fuel are under development through Power-to-Chemicals (PtC) process. Among these, CO2 methanation offers the advantage of a wide infrastructure available for the distribution and use of methane as chemical and fuel for both heat and power generation. The latter approach is also called Power-to-Gas (PtG) process. These technologies in the last year have been the focus of research, both public and private. In particular, direct methanation of biogas obtained from anaerobic digestors represents a challenge and an interesting opportunity due to the possibility to avoid the CO2 separation step at the moment needed for biogas purification to biomethane. Since CO2 separation is an additional cost, this route can be the key for economic sustainability of the process. In this review we focus on the main aspects involved in the design of a methanation plant, with a particular focus on the biogas methanation, starting from the reaction thermodynamics and kinetics. Afterwards, light is shed on the most interesting catalysts reported in the literature, with a focus on Ni-based catalysts and considering the support role in the reaction. Different kinetic approaches currently available and promising reactor types, including different simulation models, which are becoming increasingly fundamental in the reactor design and scale-up phase, are reported. Finally, the last chapter contains the most interesting and industrially relevant ongoing projects on direct biogas methanation.

Assessing the impact of irradiation-induced defects on the hardening of reactor pressure vessel materials for sustainable development of nuclear energy

The operational longevity of a nuclear power plant, specifically of the light water reactor type, hinges on the assessment of component degradation, with a particular focus on the reactor pressure vessel (RPV) materials. Among the most prevalent defects responsible for irradiation-induced hardening in RPV materials are point defects (PDs) and dislocation loops (DLs). However, their respective contributions to the overall hardening of RPV materials have not been clearly determined. To address this issue, this study was conducted using iron alloys with equivalent Mn and Ni content to those used in nuclear RPV in Japan. The study employed transmission electron microscopy (TEM), atom probe tomography (APT), and nanoindentation to assess the roles of PDs and DLs in contributing to the hardening behaviour of RPV materials. The results indicated that both solute clusters (SCs), which are formed by the aggregation of PDs, and DLs play equally important roles in the hardening behaviour of RPV materials. However, an in-depth analysis of three-dimensional images using the APT method revealed that there may have been errors in evaluating SCs and DLs, leading to double counting when assessing the impact of irradiation-induced defects on the hardening behaviour of RPV materials. These findings highlight the need for improved accuracy in evaluating these defects to better understand the behaviour of RPV materials under irradiation.

Relationship between organic removal and power production in a dual-chamber microbial fuel cell with intermittent mode

Unoptimised simultaneous performance in microbial fuel cell (MFC) is still a big concern due to a lack of information on the correlation between organic removal and power production. Its correlation becomes more substantial owing to the main factors which affect a concurrent condition. To contribute new insight, this study aimed to analyze the relationship between the main factors for determining the optimal condition of MFC performance. Dual-chamber MFC (DCMFC) was designed by modifying the anode chamber into two compartments, namely double anode chamber DCMFC (DAC-DCMFC), operated within 8 days running with intermittent mode. The differences of organic loading rate (OLR), 0.4; 1.0; 2.5 kg.m−3.d−1 represented low to high organic loadings and electrode material-based reactor types, were used to assign the optimal concomitant performance in DCMFC. A closed circuit voltage (CCV) wiring system plugged onto the data logger within running time was employed to evaluate the synchronous achievement. This study result was medium OLR 1.0 kg.m−3.d−1, and GNPs anode-PTFE cathode attained optimally in the performance. In addition, higher OLR does not indicate higher organic removal correlating linearly with power production. This finding contributes to the limitation of organic loading that biological role capabilities can use.

The UO2 Power-to-Melt Experiment Performed in the High Burnup Chemistry International Program

In this work, a detailed reevaluation of a past power-to-melt experiment performed within the so-called High Burnup Chemistry project is provided. A pressurized water reactor–type UO2 fuel rod was base irradiated in Belgian Reactor 3 up to a peak pellet burnup of 60 MWd/kgU. After base irradiation, the rod experienced a power ramp experiment in Belgian Reactor 2, reaching a ramp terminal level of 70 kW/m (later adjusted to 66 kW/m). Extensive post-irradiation examination was performed after both the base irradiation and the power ramp experiment. After the power ramp experiment, rod cladding failure and local fuel melting were observed. Fuel melting was observed in an 85-mm region around the peak power pellet with a normalized molten fuel radius in the range r/r0 = 0.20 to 0.27. The threshold power for melting derived from this experiment was 63.0 ± 4.4 kW/m.

Advanced Electroanalysis for Electrosynthesis.

Electrosynthesis is a popular, environmentally friendly substitute for conventional organic methods. It involves using charge transfer to stimulate chemical reactions through the application of a potential or current between two electrodes. In addition to electrode materials and the type of reactor employed, the strategies for controlling potential and current have an impact on the yields, product distribution, and reaction mechanism. In this Review, recent advances related to electroanalysis applied in electrosynthesis were discussed. The first part of this study acts as a guide that emphasizes the foundations of electrosynthesis. These essentials include instrumentation, electrode selection, cell design, and electrosynthesis methodologies. Then, advances in electroanalytical techniques applied in organic, enzymatic, and microbial electrosynthesis are illustrated with specific cases studied in recent literature. To conclude, a discussion of future possibilities that intend to advance the academic and industrial areas is presented.