Assessment of the Dynamic Loads Applied to the RBMK-1000 Subreactor Room Walls and Slab during Vapor Explosion

One of the conditions for the safe operation of a nuclear power plant (NPP) unit is a comprehensive design and experimental justification of its failure-free operation in all operating modes and limitation of accident radiation consequences, including those in the case of severe beyond design basis accidents. According to the nuclear power industry development plans in Russia, new NPPs equipped with RBMK-1000 reactors are not supposed to be constructed in the future. Although the assigned service life of RBMK-1000 based power units that remain in operation is close to expiration, these power units account for most of the electricity generation in the total amount of nuclear power capacities in Russia (about 40%); therefore, the relevant industry organizations have decided to extend their operation. This article analyzes the severe accident evolvement scenario at an RBMK-based NPP during the stage of severe core damage, in the course of which fuel-containing masses collapse into the subreactor space filled with water. Once fuel-containing masses emerge in the sub-reactor room, they come in interaction with the reactor base concrete. There is a potential danger of the concrete floor slab melting and the corium collapsing into the bubbler pool water. The main strategy foreseen for keeping the molten core within the reactor space boundaries involves decay heat removal from the reactor and cooling of the support metal structures by supplying water. However, the filling of the subreactor space with liquid may give rise to conditions under which vapor explosion can occur. The maximum dynamic impact applied to the RBMK-1000 subreactor room walls in the event of possible interaction between the molten corium and water during a severe beyond design basis accident is estimated. It is shown that when the corium melt interacts with a large amount of water in the subreactor room, the kinetic energy of the resulting water vapor is sufficient to cause significant destruction of the power unit building. When the water level in the subreactor room falls below one meter, the destruction hazard becomes less probable. The mass of hydrogen released as a result of the interaction is also estimated.

The mechanism of forming carbon nanostructures by electric arc-method

The regularities of the formation of nanostructures during the evaporation of graphite by the electric ARC – method are studied. Described physicochemical processes in the synthesis reactor . At plasma temperatures taking into account the behavior of particles in electromagnetic fields with extreme temperature and pressure grants. A sequence of organization of matter in the process of forming a structure according to nano-dimensional characteristics is proposed. The self-organization of systems during electric arc evaporation of graphite or graphite-containing electrodes has been studied. The mechanisms of formation of soluble (fullerenes and fullerene-like structures) and insoluble (nanocomposites, CNTs, graphenes) carbon nanostructures are considered. The processes occurring in the electric arc synthesis reactor are analyzed: the process of distribution of charged particles in an electric arc at different times; processes taking place at the anode; the mechanism of carbon vapor formation during graphite evaporation; processes in the gas phase and on the walls of the reactor under the conditions of an electric arc discharge; model of the reactor space zones; formation of carbon nanostructures in the gas phase and on the inner surface of the reactor. use of doped electrodes and metal inserts (sleeves) as catalysts for the synthesis of carbon nanostructures. The sequence of processes in the formation of spherical carbon molecules is studied, and the processes and structural transformations are considered. In the research work, the products (fullerenes and fullerene-like structures, nanocomposites, VNT, graphenes) of electric arc synthesis are presented, and modern methods of analysis are used for their fixation and identification.

Comparison ability of algae and nanoparticles on nitrate and phosphate removal from aquaculture wastewater

Background: Aquaculture wastewater contains high levels of phosphate and nitrate. The reuse of this water requires standards beyond the secondary standards to eliminate more organic pollutants from aquaculture effluents. In this research, the removal of these pollutants from wastewater using Chlorella vulgaris and Fe3 O4 nanoparticles in the reactor space was investigated. Methods: This study was conducted on fish farms effluent in the laboratory system. For this purpose, a 5-L semi-industrial reactor with a mixer blade, porous plate, and a compressor was designed. Chlorella vulgaris samples were collected from the natural environment and cultured in the laboratory environment. Also, Fe3 O4 nanoparticles were prepared from Iranian Nano Pishgaman Company to make the desired solution. During the experiment (3 weeks), samples were taken weekly (in one phase) from the effluent. Dissolved oxygen (DO), pH, nitrate (NO3 ), and phosphate (PO4 ) factors from the influent and effluent of the farms were measured. The statistical data were analyzed using SPSS version 21 and Excel 2013. Results: The amounts of nitrate and phosphate were decreased by about 80.76 and 80.55% in the biological reactor, whereas these amounts were 70.52 and 70.48% in the nanoparticle reactor, respectively. Also, there were significant differences in the amounts of NO3 and PO4 between the control treatment and weekly treatment (P<0.05). Conclusion: Based on the results, both reactors were able to reduce nitrate and phosphate from aquaculture wastewater, but the efficiency of the biological reactor was higher than that of the nanoparticle reactor.

Lanthanum Effect on Ni/Al2O3 as a Catalyst Applied in Steam Reforming of Glycerol for Hydrogen Production

Nowadays, the massive production of biodiesel leads to a surplus of glycerol. Thus, new applications of this by-product are being developed. In this study, glycerol steam reforming was carried out with Ni catalysts supported on Al2O3 rings and La-modified Al2O3. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and thermogravimetry. Both catalysts were effective in glycerol steam reforming. However, Ni/Al2O3 activity decreased over reaction time. Ni/La2O3/Al2O3 showed the best stability during the reaction. In addition, the activity of the modified support, La2O3/Al2O3, was evaluated. The modification of the support lent catalytic properties to the solid. Some conditions such as catalyst arrangement (catalyst in the first or second reactor), space velocity, and reaction temperature were studied. The highest hydrogen production was obtained when half the amount of the catalyst was located in both reactors. Glycerol conversion into gases was similar, regardless the space velocity, although higher amounts of H2 were obtained when this variable decreased. Complete glycerol conversion into gases was obtained at 900 and 1000 °C, and hydrogen production reached a H2/glycerol molar ratio of 5.6. Finally, the presence of the catalyst and the optimization of these conditions increased the energy capacity of the produced stream.

Application of Void-Free Filling Technology for Additional Safety Barriers Creation during Uranium-Graphite Reactors Decommissioning

The paper presents the results of the best material selection for additional safety barrier construction during uranium-graphite reactors decommissioning. The research findings show that the best material for safety barriers is clay-containing natural material of various types with counter-migrational and counter-filtrational qualities. We have demonstrated a technology for void-free filling of cavities in the reactor space of under-decommissioning uranium-graphite reactors on the site of JSC Pilot and Demonstration Center for Decommissioning of Uranium-Graphite Nuclear Reactors (PDC UGR). This will make it possible to construct reliable man-made geo-barriers and prevent the release of radionuclides from the repository into the environment for thousands of years.

Immobilization of aPleurotus ostreatusLaccase Mixture on Perlite and Its Application to Dye Decolourisation

In the present study, a crude laccase preparation fromPleurotus ostreatuswas successfully immobilized on perlite, a cheap porous silica material, and tested for Remazol Brilliant Blue R (RBBR) decolourisation in a fluidized bed recycle reactor. Results showed that RBBR decolourisation is mainly due to enzyme action despite the occurrence of dye adsorption-related enzyme inhibition. Fine tuning of immobilization conditions allowed balancing the immobilization yield and the resulting rate of decolourisation, with the adsorption capacity of the solid biocatalyst. In the continuous lab scale reactor, a maximum conversion degree of 56.1% was achieved at reactor space-time of 4.2 h. Stability and catalytic parameters of the immobilized laccases were also assessed in comparison with the soluble counterparts, revealing an increase in stability, despite a reduction of the catalytic performances. Both effects are most likely ascribable to the occurrence of multipoint attachment phenomena.

Power Response of a Muscle Actuator Driven by a Regenerative, Enzymatic Pressurization Mechanism

Inspired by the characteristics of biological muscles, rubber muscle actuators (RMAs) are lightweight and compliant structures that deliver high power/weight ratios and are currently under investigation for use in soft robotics, prosthetics, and specialized aircraft. RMA actuation is accomplished by inflating the structure’s air bladder, which results in the contraction of the muscle. In this proceedings paper, we describe the use of gaseous products from enzymatically-catalyzed reactions to pressurize and drive the motion of RMAs. Specifically, this paper details the power envelope of RMAs driven by the urease-catalyzed production of CO2, under dynamic loading conditions. The use of enzymatically catalyzed, gas-producing reactions is advantageous for powering RMAs, as these systems may be self-regulating and self-regenerating. Reaction design parameters for sizing the gas source to RMA power requirements and power envelope results are reported for gas-powered actuator dynamics tested on a linear motion test assembly. The power response to increasing loads reflects the partial pressure over the reaction slurry; therefore, the chemistry and reactor scale affect the entire structure’s efficiency. We outline the reactor space-time design constraints that facilitate a tailored power response for urease catalyzed gas generation sources.

Experimental Determination of Energy Demand and Spatio-Temporal Course of Pyrolysis for Various Materials

The article presents a detailed analysis of brown coal, rubber and polyethylene pyrolysis in a horizontal reactor of a thermic facility. It is a facility continuously processing entry materials flowing in the amount of up to 150 Kg.h -1 and with the total maximum heaters’ output of 200 kW. The attention has been paid to the thermal input of the pyrolysis process and to the description of physical-chemical processes in time and the reactor space. The objective has been to find out the best combination of entry material and process conditions from the point of view of pyrolysis energy intensity. The article specifics are based on the fact that the mentioned processes have been analysed in a large facility having the semi-production characteristics, not within a laboratory system used usually in this kind of research (DSC).

CANDU Reactor Space-Time Kinetic Model for Load Following Studies

This paper presents the development of a three-dimensional space-time neutronic kinetic model of a Canadian deuterium uranium (CANDU) reactor using a modal method. In this method, the reactor space-time neutron flux is synthesized by a time-weighted series of precalculated neutron flux modes. The modes are eigenfunctions of the governing neutron diffusion equation during reference steady-state operation. The xenon effect has also been considered. The reactor model is then implemented within a simulation platform of a CANDU6 reactor regulating system in MATLAB/SIMULINK. A nondimensionalized SIMULINK representation of the reactor kinetic model is established. The behavior of the reactor during load following transients has been simulated using the developed reactor-modeling module. The simulation results prove the efficiency of the model. A three-dimensional neutron flux distribution during transients is represented.

CANDU Reactor Space-Time Kinetic Modeling for Load Following Control

This paper presents the development of a three-dimensional space-time neutronic kinetic modeling of a CANadian Deuterium Uranium (CANDU) reactor for control system design and research, using a modal method. In this method, the reactor space-time neutron flux is synthesized by a time-weighted series of pre-calculated neutron flux modes. The modes are eigenfunctions of the governing neutron diffusion equation during reference steady-state operation. The Xenon effect has also been considered. The reactor model is then implemented within a simulation platform of CANDU6 reactor regulating system (RRS), in MATLAB/SIMULINK. Non-dimensionalized SIMULINK representation of the reactor kinetic modeling is established. Behavior of the reactor during a load following transient has been simulated using the developed reactor-modeling module. The simulation results prove the efficiency of the reactor modeling. Real-time three-dimensional neutron flux distribution during the transient analysis is represented.