Studies on molecular diffusion and natural convection in a multicomponent gas system

Takeda, Tetsuaki; Hishida, Makoto

doi:10.1016/0017-9310(95)00148-3

Cited by 43 publications

(32 citation statements)

References 11 publications

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“…The entire experiment was conducted at isothermal conditions at 18 C. [5] The two gases used were helium in the tube and nitrogen in the lower tank. The experimental procedures are:…”

Section: Isothermal Jaeri Experiments -Diffusion Experiments Descriptionmentioning

confidence: 99%

“…Experimental Apparatus [5] A The mole fraction of each gas species and the density of the gas mixture were measured at four sampling points shown in Figure 20.…”

Section: Benchmarking Of the Multi-component Model With Chemical Reacmentioning

confidence: 99%

“…The value of the exponential index, n, in terms of the oxygen partial pressure ranges from 0.75 to 1 for PGX 2 . For this type of graphite, the value used in this analysis is 1 following JAERI's recommendation [5].…”

Section: Chemical Reaction Rates [5]mentioning

confidence: 99%

“…The mole number for the reaction term of O 2 and for the generation term of CO and CO 2 of 12 can be obtained from the following relation, respectively [5]. …”

Section: Chemical Reaction Rates [5]mentioning

confidence: 99%

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Air ingress benchmarking with computational fluid dynamics analysis

Kadak

Zhai

2006

Nuclear Engineering and Design

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Air ingress accident is a complicated accident scenario that may limit the deployment of hightemperature gas reactors. The complexity of this accident scenario is compounded by multiple physical phenomena that are involved in the air ingress event. These include diffusion, natural circulation, and complex chemicals reaction with graphite and oxygen. In an attempt to better understand the phenomenon, the FLUENT-6 computational fluid dynamics code was used to assess two air ingress experiments. The first was the Japanese series of tests on the reference performed in the early 1990's by Takeda and Hishida. These separate effects tests were conducted to understand and model the a multi-component experiment in which all three processes were included with the introduction of air in a heated graphite column. MIT used the FLUENT code to benchmark these series of tests with quite good results. These tests are generically applicable to prismatic reactors and the lower reflector regions of pebble-bed reactors. The second series of tests were performed at the NACOK facility for pebble bed reactors as reported by M. B. Kuhlmann in 1999. This tests were aimed at understanding natural circulation of pebble bed reactors by simulating hot and cold legs of these reactors. The FLUENT code was also successfully used to simulate these tests. The results of these benchmarks and the findings will be presented.

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“…The entire experiment was conducted at isothermal conditions at 18 C. [5] The two gases used were helium in the tube and nitrogen in the lower tank. The experimental procedures are:…”

Section: Isothermal Jaeri Experiments -Diffusion Experiments Descriptionmentioning

confidence: 99%

“…Experimental Apparatus [5] A The mole fraction of each gas species and the density of the gas mixture were measured at four sampling points shown in Figure 20.…”

Section: Benchmarking Of the Multi-component Model With Chemical Reacmentioning

confidence: 99%

Section: Chemical Reaction Rates [5]mentioning

confidence: 99%

“…The mole number for the reaction term of O 2 and for the generation term of CO and CO 2 of 12 can be obtained from the following relation, respectively [5]. …”

Section: Chemical Reaction Rates [5]mentioning

confidence: 99%

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Air ingress benchmarking with computational fluid dynamics analysis

Kadak

Zhai

2006

Nuclear Engineering and Design

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“…Computational fluid dynamic calculations were recently made to mimic the LOCA between two tanks filled with helium and oxygen, respectively. The scenario postulated by is depicted in Figure 2 Earlier studies of the mechanisms leading to air ingress into the reactor vessel focused on diffusion as described by Fick's Law (Takeda 1997, Takeda and Hishida 1996) and ignored the effects of density gradients on the interactions between helium (low density) and air or helium-laced air (high density) flow.…”

Section: Introductionmentioning

confidence: 99%

FINAL REPORT on Experimental Validation of Stratified Flow Phenomena, Graphite Oxidation, and Mitigation Strategies of Air Ingress Accidents

Oh¹,

Kim²,

No³

et al. 2011

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(NGNP)/Generation IV very high temperature reactor (VHTR). Phenomena Identification and Ranking studies to date have identified the air ingress event, following on the heels of a VHTR depressurization, as being very important. Consequently, the development of advanced air ingress-related models and verification and validation are a very high priority for the NGNP Project.Following a loss of coolant and system depressurization incident, air ingress will occur through the break, leading to oxidation of the in-core graphite structure and fuel. This study indicates that depending on the location and the size of the pipe break, the air ingress phenomena are different. In an effort to estimate the proper safety margin, experimental data and tools, including accurate multidimensional thermal-hydraulic and reactor physics models, a burn-off model and a fracture model are required. It will also eventually require effective strategies to mitigate the effects of oxidation.This 3-year project (FY 2008 to FY 2010 focused on various issues related to the VHTR air-ingress accident, including (a) analytical and experimental study of air ingress caused by density-driven, stratified, countercurrent flow, (b) advanced graphite oxidation experiments, (c) experimental study of burn-off in the core bottom structures, (d) structural tests of the oxidized core bottom structures, (e) implementation of advanced models developed during the previous tasks into the GAMMA code, (f) full air ingress and oxidation mitigation analyses, (g) development of core neutronic models, (h) coupling of the core neutronic and thermal hydraulic models, and (i) verification and validation of the coupled models. E-1. RESEARCH OBJECTIVESThe main objectives of this 3-year project were to investigate air-ingress related phenomena in the VHTRs and perform modeling and experiments for better understanding on the accident consequences. The major phenomena, targeted in this study, were (1) density gradient driven stratified flow, (2) graphite oxidation and structural degradation, (3) thermal hydraulics and neutronics coupling, and (4) development of air ingress mitigation and computational fluid dynamics (CFD) calculations E-2. REPORT CONTENT AND ORGANIZATIONThis report, which highlights key accomplishments achieved from FY 2008 to FY 2010, consists of the following sections:1. Introduction: Section 1 is introductory information about this project with objectives and strategies.

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