Simulation Research of Combustion Characteristics of Mixed Sodium Fire in a Columnar Flow

2021 ◽  
Author(s):  
Yao-long Ma ◽  
Zhi-gang Zhang ◽  
Qi Wu ◽  
Fang Wang
Keyword(s):  
Oxygen Concentration ◽  
Fast Reactor ◽  
Early Stage ◽  
Chemical Kinetic ◽  
Liquid Sodium ◽  
Chamber Pressure ◽  
Prevention Measures ◽  
Discrete Phase Model ◽  
Pipe System ◽  
Spatial Temperature

Abstract Sodium fire accident which was caused by the leakage of liquid sodium is the design basis accidents of sodium-cooled fast reactor. The column flow is a more realistic form of liquid sodium leakage due to the pipe system insulation structure and lower pressure in the sodium-cooled fast reactor. The leaked liquid sodium would combust in the form of columnar fire in the space and pool fire on the ground at the same time to form a mixed sodium fire in a columnar flow. In this paper, a numerical calculation model is established to simulate mixed sodium combustion in a columnar flow. This model is based on the turbulence model, discrete phase model and finite-rate model in Fluent software, and combined with chemical kinetic of sodium combustion. Several variables like spatial temperature, oxygen concentration and pressure during combustion of mixed sodium fire are calculated, and validated with experimental data collected in previous mixed sodium combustion experiment. Besides, the oxygen concentration and the temperature field are calculated for further study of the experiment. The result shows that the spatial temperature calculated by the code coincides well with the experiment, but the chamber pressure cannot be predicted precisely. The oxygen concentration in the center of the sodium flow would decline rapidly in the early stage, then remains at around 5%, but the oxygen concentration in the distance is relatively high. This study could provide reference for evaluation and prevention measures of sodium fire.

Theoretical Study on Chemical-Kinetic Characteristics of Oxy-Coal Mild Combustion

2016 ◽  
Author(s):  
Ruochen Liu ◽  
Enke An ◽  
Kun Wu
Keyword(s):  
Activation Energy ◽  
Oxygen Concentration ◽  
Reaction Pathway ◽  
Chemical Kinetic ◽  
State Theory ◽  
Kinetic Characteristics ◽  
Low Oxygen ◽  
Elementary Reactions ◽  
Mild Combustion ◽  
Low Oxygen Concentration

The chemical-kinetic characteristics of oxy-coal MILD combustion under different initial temperature and oxygen concentration were studied numerically. Aromatic benzene was considered representative for coal molecule. A unique reaction pathway under low oxygen concentration was obtained, the activation energy and reaction rate constant of involved elementary reactions were calculated through classic transition state theory (TST). The results show that low oxygen concentration and high temperature is advantageous for thickening flame front as well as slowing down flame propagation; as oxygen concentration and temperature increase, the global activation energy increases with greater slope; the decomposition of C5H5 dominates under high oxygen concentration, while the decomposition and oxidation of C5H5 become equally important as oxygen concentration decreases, leading to a new pathway that the complexity of overall chemical reactions develops; the radical CH2CHO is easily trigged under low oxygen concentration, its decomposition reaction dominates in the unique pathway C5H5→C5H4O→c-C4H5CH2CHO→CH3 due to larger activation energy, where more CO escapes. The simulation results have theoretical referencing value, laying foundations for the further practical work.

scholarly journals Protecting Healthcare Professionals during the COVID-19 Pandemic

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Baiwen Qi ◽  
Haiheng Peng ◽  
Kangquan Shou ◽  
Zhengyu Pan ◽  
Min Zhou ◽  
...  
Keyword(s):  
Nosocomial Infection ◽  
Late Stage ◽  
Healthcare Professionals ◽  
Clinical Investigation ◽  
Early Stage ◽  
Close Contact ◽  
Antiviral Treatment ◽  
Direct Care ◽  
Effective Control ◽  
Prevention Measures

Objective. To understand how to implement proactive prevention measures among healthcare professionals for preventing potential nosocomial infection. Methods. 91 healthcare professionals confirmed with the COVID-19 infection were collected, and clinical characteristics and epidemiological data were evaluated. Results. Among the cases, 77 cases (84.6%) were confirmed by the viral nucleic acid test, and the other 14 cases were diagnosed by the clinical investigation. Ground glass opacity and bilateral shadows distribution were observed in 78 cases (85.6%). 56 cases (61.5%) were admitted into Zhongnan Hospital and subjected to antiviral treatment. 73 of a total of 91 cases (80.2%) with a median incubation period of 3 days (IQR, 2 to 6) reported close contact history with patients with the COVID-19 infection. The most common symptoms at the onset of illness were fever (66 cases, 72.5%) and cough (54 cases, 59.3%). The initial positive rate of the CT scan and RT-PCR assay were 84.6% and 48.4%, respectively (P<0.01). There were 50 cases occurred during the early stage (before Jan 20, 2020), whereas 41 cases occurred at a late stage (after Jan 20, 2020). In the early stage, the most common route of exposure to COVID-19 was via direct care in the absence of any invasive procedure. By contrast, 37 healthcare professionals infected with COVID-19 in the late stage were confirmed to have been exposed via aerosol-generating procedures. Conclusion. Identification of the asymptomatic individuals in healthcare settings and prompt response when a suspicious case is considered may render effective control of the nosocomial infection during this pandemic.

scholarly journals Splashing Simulation of Liquid Steel Drops during the Ruhrstahl Heraeus Vacuum Process

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1070
Author(s):  
Zhi-jian Zhao ◽  
Min Wang ◽  
Lei Song ◽  
Yan-ping Bao
Keyword(s):  
Pressure Drop ◽  
Liquid Steel ◽  
Industrial Production ◽  
Vacuum Chamber ◽  
Early Stage ◽  
Vacuum Treatment ◽  
Coupling Model ◽  
Liquid Level ◽  
Vacuum Pressure ◽  
Discrete Phase Model

In view of the serious splashing problem in the 120 ton Ruhrstahl Heraeus (RH) refining process of a special steel company, a coupling model of volume of fluid + discrete phase model was established to study the influence of the vacuum pressure drop mode on the RH vacuum splashing. Three different pressure drop modes were simulated, and the splash situation was described by the fluctuation of the liquid level and the velocity field in the vacuum chamber in this model. The model predicted that the most serious splashing situation of liquid drops would happen at the early stage of vacuum treatment, which was consistent with that found in industrial production. The liquid level in the vacuum chamber maintained a low fluctuation at the late stage of the RH vacuum process. The vacuum pressure drop mode was closely relevant with the splashing situation. The splashing of liquid steel can be effectively improved by controlling the vacuum pressure drop mode, and it can be used in the industrial production situation.

Structural integrity of fast reactor components

1990 ◽  
Vol 331 (1619) ◽  
pp. 419-434 ◽  
Keyword(s):  
Fast Reactor ◽  
Structural Integrity ◽  
Ambient Pressure ◽  
Failure Process ◽  
Liquid Sodium ◽  
Secondary Circuit ◽  
Deformation And Failure ◽  
Integrity Assessment ◽  
High Boiling Point ◽  
Materials Used

The paper focuses on the generic aspects of the main structural integrity issues in the liquid-sodium-cooled fast reactor. The choice of sodium as a coolant has important consequences for the deformation and failure process in the materials used for the main plant components. For example, its high boiling point means that the prim ary and secondary circuit containment operates at ambient pressure and the system loading is dominated by thermal stress. The resultant low primary stresses make leak-before-break a viable integrity criterion for all sodium boundary components. Sodium coolant operates at comparatively high temperatures and this, together with the good heat-transfer properties, means that thermal fatigue and creep are of concern, particularly in the hotter parts of the plant. A third factor concerns the steam generators, where the integrity of the sodium—water boundary is particularly important. The paper will consider the failure processes that must be addressed in relation to these conditions and the development of the integrity assessment arguments.

Experimental Study on Sodium Column Fire of Sodium-Cooled Fast Reactor

2013 ◽  
Author(s):  
Kang-wei Peng ◽  
Zhi-gang Zhang ◽  
Ming Guo ◽  
Chao Wang ◽  
Shu-bin Sun
Keyword(s):  
High Temperature ◽  
Fast Reactor ◽  
Difficult Problem ◽  
Temperature Fields ◽  
Practical Significance ◽  
Liquid Sodium ◽  
Insulation Material ◽  
Reactor Accident ◽  
Temperature Liquid ◽  
Operation Pressure

In the operation of sodium-cooled fast reactor, accident caused by the leakage and combustion of liquid sodium is common, and it is a pivotal and difficult problem in research, construction and operation of sodium-cooled fast reactor internationally. In actual operation of sodium-cooled fast reactor, liquid sodium in sodium fire accident is difficult to form fog but mainly in columnar flow form due to low operation pressure and thermal insulation material wrapping the pipe, so experimental research about columnar fire is of much more practical significance. This paper focuses on combustion property on sodium column fire in the sodium-cooled fast reactor. Liquid sodium with high temperature will be poured into the combustion room via pouring high pressure nitrogen into sodium storage tank when solid sodium has been heated to enactment temperature; liquid sodium with high temperature will burn at combustion room with air forming sodium column fire. Initial temperature of sodium jet is about 200°C in experiment and spurt pressure is 0.2MPa, spurt flow is about 0.4–0.6m3 each hour. Temperature fields in combustion tank space and the catch plate in the bottom are measured through dozens of thermocouple distributed in combustion tank. No atomization phenomenon would exist in the pure sodium columnar fire in the space, the atomized fire triggered by splashed sodium from sodium stream striking the admittance plat and generate more than the high temperature of 900°C.

Irradiation creep behavior of V–4Cr–4Ti alloys irradiated in a liquid sodium environment at the JOYO fast reactor

2013 ◽  
Vol 437 (1-3) ◽  
pp. 341-349 ◽  
Author(s):  
Ken-ichi Fukumoto ◽  
Hideki Matsui ◽  
Minoru Narui ◽  
Masanori Yamazaki
Keyword(s):  
Creep Behavior ◽  
Fast Reactor ◽  
Liquid Sodium ◽  
Irradiation Creep

scholarly journals Numerical Investigation of Corium Coolability in Core Catcher: Sensitivity to Modeling Parameters

2018 ◽  
Author(s):  
Liancheng Guo ◽  
Andrei Rineiski
Keyword(s):  
Fast Reactor ◽  
Large Scale ◽  
Mass Transfer Process ◽  
Severe Accident ◽  
Liquid Sodium ◽  
Numerical Experience ◽  
The Core ◽  
Sodium Fast Reactor ◽  
Core Catcher ◽  
Fuel Pin

To avoid settling of molten materials directly on the vessel wall in severe accident sequences, the implementation of a ‘core catcher’ device in the lower plenum of sodium fast reactor designs is considered. The device is to collect, retain and cool the debris, created when the corium falls down and accumulates in the core catcher, while interacting with surrounding coolant. This Fuel-Coolant Interaction (FCI) leads to a potentially energetic heat and mass transfer process which may threaten the vessel integrity. For simulations of severe accidents, including FCI, the SIMMER code family is employed at KIT. SIMMER-III and SIMMER-IV are advanced tools for the core disruptive accidents (CDA) analysis of liquid-metal fast reactors (LMFRs) and other GEN-IV systems. They are 2D/3D multi-velocity-field, multiphase, multicomponent, Eulerian, fluid dynamics codes coupled with a fuel-pin model and a space- and energy-dependent neutron kinetics model. However, the experience of SIMMER application to simulation of corium relocation and related FCI is limited. It should be mentioned that the SIMMER code was not firstly developed for the FCI simulation. However, the related models show its basic capability in such complicate multiphase phenomena. The objective of the study was to preliminarily apply this code in a large-scale simulation. An in-vessel model based on European Sodium Fast Reactor (ESFR) was established and calculated by the SIMMER code. In addition, a sensitivity analysis on some modeling parameters is also conducted to examine their impacts. The characteristics of the debris in the core catcher region, such as debris mass and composition are compared. Besides that, the pressure history in this region, the mass of generated sodium vapor and average temperature of liquid sodium, which can be considered as FCI quantitative parameters, are also discussed. It is expected that the present study can provide some numerical experience of the SIMMER code in plant-scale corium relocation and related FCI simulation.

Investigation of Chemical Kinetic Model for Hypergolic Propellant of Monomethylhydrazine and Nitrogen Tetroxide

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hu Hong-bo ◽  
Chen Hong-yu ◽  
Yan Yu ◽  
Zhang Feng ◽  
Yin Ji-Hui ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Flame Temperature ◽  
Chemical Kinetic ◽  
Chemical Mechanism ◽  
Chamber Pressure ◽  
Nitrogen Tetroxide ◽  
Combustion Flame ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Calculation Results

Abstract Hypergolic bipropellant of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) is extensively used in spacecraft propulsion applications and rocket engines. But studies on the chemical kinetic mechanism of MMH/NTO are limited. So, in this study by integrating the submechanisms of MMH decomposition, NTO thermal decomposition, MMH/NTO and intermediates, and small hydrocarbons, the comprehensive chemical mechanism of MMH/NTO bipropellant is proposed. The present chemical mechanism consists of 72 species and 406 elementary reactions. In two respects of ignition delay times and combustion flame temperatures, the present model has been validated against the theoretical calculation results and also compared with other kinetic models in the literature. The validations show that the predicted ignition delay times by the present kinetic model are highly consistent with the theoretical data and well describe the pressure-dependent characteristic. For combustion flame temperature, the present model also exhibits better predictions to the theoretical calculation results, which are also the same as the predictions by the MMH-RFNA model. Furthermore, the influences of initial temperature, chamber pressure, and NTO/HHM mass ratio (O/F) on the ignition delay time and combustion flame temperature are investigated. The auto-ignition behavior of MMH/NTO propellant is sensitive to initial temperature and chamber pressure, and the combustion flame temperature is more sensitive to the O/F. This study provides a detail chemical kinetics model for further mechanism simplification and combustion numerical simulation.

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