| dc.description.abstract | A computational fluid dynamics investigation was conducted to evaluate the thermal-hydraulic behavior within a molten salt nuclear core for a given heat generation profile. The entry length behavior, maximum temperature, and radial temperature gradient are investigated to provide insight as to the effective heat removal capabilities for two domains. The first flow geometry evaluated was a fully developed, 1D laminar flow in a cylindrical flow channel within a hexagonal graphite unit cell with internal heat generation in both the fluid and solid domains. This flow geometry had adiabatic boundary conditions imposed upon the outer wall of the graphite, and entry length behavior of the fluid was investigated to provide insight to the value of the effective heat transfer coefficient for a given coolant channel within a molten salt reactor core, as well as characterizing it as a function of height. An array of the hexagonal unit cell organized into a 60-degree wedge which represent a simplified molten salt reactor core region was next evaluated. The aim of this evaluation was that for a given heat generation profile, which was axially and radially dependent, by controlling the mass flow rate through each channel the radial temperature gradient and maximum temperature can be minimized, thus minimizing the thermal stresses. This minimization of the radial temperature gradient is also beneficial for neutronic evaluation, as the radial density distribution of the fuel salt is temperature dependent. Furthermore, the minimization of the maximum temperature in the reactor core is desired for both structural and neutronic purposes, as a significantly large thermal maximum could induce structural failure or a local perturbation of the neutron flux in that region due to temperature feedback effects and local density variation. It was found that due to the internal heat generation in the solid graphite domain, the maximum temperature was located in the graphite and the fuel salt acted as a coolant, rather than depositing heat into the graphite. The ideal mass flow rate distribution was found, and the combined entry length behavior of a channel in that case was evaluated. Application of this methodology provides key insight into the design specifications needed for a flow distributor which could be present in the lower plenum region. | |
