Modelling research and performance analysis on a megawatt-level helium-xenon gas cooled small reactor based on the thermal-hydraulic constraints

A conceptual design scheme of helium-xenon gas-cooled fast reactor core consisting of hexagonal prismatic fuel assemblies with a thermal power of 6 MW was proposed. The geometric parameters of the core were determined based on the relationship between hydraulic diameter and inlet velocity of fuel elements with restrain of allowable pressure drop and maximum fuel surface temperature. Thermal performance of individual fuel elements and the cooling effect of helium-xenon channels within the reflector layer were analyzed. Channels for helium-xenon gas mixture were added to reduce the surface temperature outside the reflector layer.

The computational results indicate that the operational burnup of the reactor can reach 40.88 MW d/kg. The graphite rods added to the core collectively contribute 1404 pcm reactivity, achieving the effect of reducing fuel loading and increasing safety margins in water flooding accidents. The helium-xenon gas mixture reduces the reflector layer temperature by approximately 48.88 %.