Containment building | EPFL Graph Search

A containment building is a reinforced steel, concrete or lead structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radioactive steam or gas to a maximum pressure in the range of . The containment is the fourth and final barrier to radioactive release (part of a nuclear reactor's defence in depth strategy), the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system. Each nuclear plant in the United States is designed to withstand certain conditions which are spelled out as "Design Basis Accidents" in the Final Safety Analysis Report (FSAR). The FSAR is available for public viewing, usually at a public library near the nuclear plant. The containment building itself is typically an airtight steel structure enclosing the reactor normally sealed off from the outside atmosphere. The steel is either free-standing or attached to the concrete missile shield. I

Large eddy simulation of particulate flow inside a differentially heated cavity

Christoph Bosshard, Abdelouahab Dehbi, Michel Deville, Emmanuel Leriche, Alfredo Soldati

In nuclear safety, some severe accident scenarios lead to the presence of fission products in aerosol form in the closed containment atmosphere. It is important to understand the particle depletion process to estimate the risk of a release of radioactivity to the environment should a containment break occur. As a model for the containment, we use the three-dimensional differentially heated cavity problem. The differentially heated cavity is a cubical box with a hot wall and a cold wall on vertical opposite sides. On the other walls of the cube we have adiabatic boundary conditions. For the velocity field the no-slip boundary condition is applied. The flow of the air in the cavity is described by the Boussinesq equations. The method used to simulate the turbulent flow is the large eddy simulation (LES) where the dynamics of the large eddies is resolved by the computational grid and the small eddies are modelled by the introduction of subgrid scale quantities using a filter function. Particle trajectories are computed using the Lagrangian particle tracking method, including the relevant forces (drag, gravity, thermophoresis). Four different sets with each set containing one million particles and diameters of 10 mu m, 15 mu m, 25 mu m and 35 mu m are simulated. Simulation results for the flow field and particle sizes from 15 mu m to 35 mu m are compared to previous results from direct numerical simulation (DNS). The integration time of the LES is three times longer and the smallest particles have been simulated only in the LES. Particle statistics in the LES and the DNS were similar and the settling rates were practically identical. It was found that for this type of flow no model was necessary for the influence of the unresolved flow scales on the particle motions. This can be explained by the dominant nature of gravity settling compared to turbophoresis which is negligible for the particle sizes of the present study. (C) 2013 Elsevier B.V. All rights reserved.

Elsevier2014

Large eddy simulation of particulate flow inside a differentially heated cavity

Christoph Bosshard, Abdelouahab Dehbi, Michel Deville, Emmanuel Leriche, Alfredo Soldati

Elsevier2014