In this study the hazardous potential of flammable hydrogen-air mixtures with vertical concentration gradients is investigated numerically. The computational model is based on the formulation of a reaction progress variable and accounts for both deflagrative flame propagation and autoignition. The model is able to simulate the deflagration-to-detonation transition (DDT) without resolving all microscopic details of the flow. It works on relatively coarse grids and shows good agreement with experiments. It is found that a mixture with a vertical concentration gradient can have a much higher tendency to undergo DDT than a homogeneous mixture of the same hydrogen content. In addition, the pressure loads occurring can be much higher. However, the opposite effect can also be observed, with the decisive factor being the geometric boundary conditions. The model gives insight into different modes of DDT. Detonations occurring soon after ignition do not necessarily cause the highest pressure loads. In mixtures with concentration gradient, the highest loads can occur in regions of very low hydrogen content. These new findings should be considered in future safety studies.

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Numerical Simulation of the Deflagration-to-Detonation Transition in Inhomogeneous Mixtures

Validation of a FLUENT CFD model for hydrogen distribution in a containment

A review on hydrogen generation, explosion, and mitigation during severe accidents in light water nuclear reactors

Simulation of hydrogen distribution in an Indian Nuclear Reactor Containment

Hydrogen generation during the progression of an accident in a nuclear reactor and its release into the containment comprise an important safety concern in the management of severe accidents in nuclear power plants. The distribution of hydrogen within the containment has important bearing on possibility, mode, and consequence of combustion in the containment. Hence, several small- and large-scale facilities have been built to study the distribution of released hydrogen. Further, several numerical studies and intercomparison exercises on hydrogen distribution have been carried out. The present review summarizes the experimental and numerical studies on hydrogen distribution and suggests opportunities for further studies.

Hydrogen Distribution in Nuclear Reactor Containment During Accidents and Associated Heat and Mass Transfer Issues—A Review

Experimental investigation of iodine removal and containment depressurization in containment spray system test facility of 700 MWe Indian pressurized heavy water reactors

The management of hydrogen in nuclear reactor containment after LOCA is of practical importance to preserve the structural integrity of the containment. This paper presents the results of systematic work carried out using the commercial software FLUENT to assess the concentration distribution of hydrogen in a typical Indian Nuclear Reactor Containment. Accurate turbulence modelling is important to predict the concentration distribution correctly. The turbulence models which were most commonly cited in the literature for modelling buoyancy driven flows were assessed for their suitability and it was found that the buoyancy modified Standard k-e model is adequate for the purpose by comparing with some experimental data available in the literature. Subsequently, unstructured meshes were generated to represent the containment of a typical Indian nuclear reactor. Analyses were carried out to quantify the hydrogen distribution for three cases. These were (1) Uniform injection of hydrogen for a given period of time at room temperature, (2) Time varying injection as has been computed from an accident analysis code, (3) Time varying injection (as used in case (2)) at a high temperature. A parametric exercise was also carried out in case (1) where the effect of various inlet orientations and locations on hydrogen distribution was studied. Results of all these cases have been presented in this paper.Copyright © 2008 by ASME

Nalini Mohan

Papers

Simulation of hydrogen distribution in an Indian Nuclear Reactor Containment

Experimental investigation of iodine removal and containment depressurization in containment spray system test facility of 700 MWe Indian pressurized heavy water reactors

Hydrogen Distribution in a Nuclear Reactor Containment