During severe accident in the nuclear power plant, a considerable amount of hydrogen can be generated by an active reaction of the fuel-cladding with steam within the pressure vessel which may be released into the containment of nuclear power plant. Hydrogen combustion may occur where there is sufficient oxygen, and the hydrogen release rates exceed 10% of the containment. During hydrogen combustion, detonation force and short term pressure may be produced. The production of these gas species can be detrimental to the structural integrity of the safety systems of the reactor and the containment. In 1979, the Three Mile Island (1979) accident occurred. This accident compelled experts and researchers to focus on the study of distribution of hydrogen inside the containment of nuclear power plant. However after the Fukushima Dai-ichi nuclear power plant accident (2011), the modeling of the gas behavior became important topic for scientists. For the stable and normal operation of the containment, it is essential to understand the behavior of hydrogen inside the containment of nuclear power plant in order to mitigate the occurrence of these types of accidents in the future. For this purpose, it is important to identify how burnable hydrogen clouds are produced in the containment of nuclear power plant. The combustion of hydrogen may occur in different modes based on geometrical complexity and gas composition. Reliable turbulence models must be used in order to obtain an accurate estimation of the concentration distribution as a function of time and other physical phenomena of the gas mixture. In this study, a small scale hydrogen-dispersion case is selected as a benchmark to address turbulence models. The computations are performed using HYDRAGON code developed by Department of Engineering Physics, Tsinghua University, China. HYDRAGON code is a three dimensional thermal-hydraulics analysis code. The purpose of this code is to predict the behavior of hydrogen gas and multiple gas species inside the containment of nuclear power plant during severe accident. This code mainly adopts CFD models and structural correlations used for wall flow resistance instead of using boundary layer at a wall. HYDROGAN code analyzes many processes such as hydrogen diffusion condensation, combustion, gas stratification, evaporation, mixing process. The main purpose of this research is to study the influence of turbulence models to the concentration distribution and to demonstrate the code thermal-hydraulic simulation capability during nuclear power plant accident. The calculated results of various turbulence models have different prediction values in different compartments. The results of k–ε turbulence model are in reasonable agreement as compared to the benchmark experimental data.
During a severe nuclear power plant (NPP) accident, large amounts of hydrogen and steam can be produced in nuclear reactor containment. In the case of hydrogen combustion, there is a possibility of producing short term pressure or detonation force. Therefore, these gas species’ production could threaten containment integrity. For instance, in the past, two gas explosion accidents occurred: In 1979 Three Mile Island and in 2011 Fukushima. After these accidents, modeling the gas behavior became an important topic in nuclear safety analyses. In order to predict hydrogen behavior and other gas species transport, mixing and combustion, reliable turbulence models need to be applied. In this work, standard k–ε, k–ω, RNG k–ε, Realizable k–ε and SST k–ω turbulence models are addressed. The computations are performed with HYDRAGON code. HYDRAGON code is a three-dimensional thermal-hydraulic code, developed to solve low-speed gas flow of compressible Navier-Stokes equations in cartesian or cylindrical coordinates or a mixture of the two coordinates. The goal of this work is to test the performance of these models by comparing the results to the benchmark. The code aims to predict containment thermal-hydraulic conditions during NPP accident.
Catalysts Specifications DOC Ф10.5"x6" 400 cpsi/4 mil CDPF Ф10.5"x11" 200 cpsi/12 mil Circumferential Uniformity Test 24 thermocouples were inserted into the DPF channels to measure the inner temperature of the filter. The temperature circumferential uniformity of three different sections at the DPF length direction was analyzed.
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