THERMALHYDRAULICS ANALYSIS OF FIXED BED NUCLEAR REACTOR IN SOME DIFFERENT CONFIGURATION

Abstract

The Fixed Bed Nuclear Reactor (FBNR) is a small module reactor using the spherical fuel elements. It has a simple
design, inherent safety features, passive cooling for some situations, and reduced environmental impacts. The key
to the safety characteristic of FBNR is simply that the core will be become empty of fuel elements, and nuclear
criticality situation will be stopped when any undesired situation occurs. Any signal from any of the numerous
detectors, due to any accident event, will cut-off power to the pump, causing the fuel elements to fall back into the
fuel chamber where they remain in a highly subcritical and passively cooled conditions. This mechanism helps the
reactor has a very high passive safety. Therefore, FBNR is one kind of IV generation according to the International
Atomic Energy Agency (IAEA) defines. However, it also makes difficulties for analytical methods to understand
clearly about thermalhydraulics processes in the active core. In the paper, the authors used the Computational Fluid
Dynamics (CFD) method to analyze the basic thermalhydraulics parameters of FBNR such as temperature
distribution of spherical fuels, and temperature, pressure and velocity of the coolant in some different
configurations. The results are highly accurate and visual, helping us to evaluate more exactly about the processes
of heat generation, thermal conductivity and heat exchange between fuel elements and coolant water. Finally, we
can choose the best configuration of FBNR.