Reactors with micro fuel particles: hydrodynamics of permeable channels of the bulk assembly

Abstract

The prospect of use of fuel in the form of micro particles (balls with a diameter about a millimeter formed by the fissile material and a protective cover to hold the radioactive fission products) in nuclear reactors is disclosed. It’s marked that flow ability, large specific surface of heat removal, extraordinary high resistance of micro fuel particles allow to design innovative safe reactors for various purpose: transportable, breeders, high-temperature, high neutron flux etc. It’s suggested to complete the active zone by bulk heat releasing assemblies. In them the advantages of spherical micro fuel particles and a coolant side supply to the bed through permeable distribution and branch channels are harmoniously combined in these assembles. It is presented the scheme of bulk assemblies and carried out the analysis of modeling of dynamics of a stream in permeable channels. It is shown that the mathematical description of liquid movement in such channels has ambiguity and discrepancy. To eliminate modeling shortcomings a new kinematic image of current in the permeable channels was offered. It was proposed instead of the existing one representing a jet to which particles of coolant were continuously joined or separated on the permeable wall. In the new interpretation the flow in the permeable channel is considered as turn of the stream at its simultaneous expansion or narrowing depending on there is outflow or inflow. On the base of this image the equation for determination of coolant pressure changing in the permeable channel is obtained; reaction of a stream for changing of flow rate increment is established, the tangent component of a velocity on a permeable wall is founded. Thereby the disadvantages of describing of coolant moving in the bulk assembles channels are eliminated. Permeable channels are used not only in nuclear reactors, but also in many other technological devices: catalytic reactors, heat exchangers, filters, collector and distributing systems. The obtained results can be used for designing other devices with permeable channels.

Investigation of heat generation in a pebble bed during induction heating

“…Fuel assemblies with microfuels, on the one hand, have inherent internal safety, and will also improve energy efficiency. In such an assembly, microfuel elements are supposed to be placed between perforated covers in the form of free pebble bed [1]. Fuel assemblies based on microfuel elements can probably find application, first of all, in low-power nuclear power plants, the interest in which is currently growing.…”