Simulation of Proposed Heat Treatment Methods for the Sister Rods

摘要

The simulation results indicate that heat applied through the exterior of the pipe can be effective in delivering the necessary supplementary heat to achieve the targeted peak temperature in the lab. Natural convection, in combination with external heat, can produce the desired temperatures. However, fine control of the temperature is not possible when relying solely on natural convection. Through the use of forced convection, the temperature of the fuel rod can more readily be adjusted by varying the flow velocity and inlet temperature. Although the addition of forced convection is expected to be more expensive and difficult to implement in the hot cell, it is recommended as a means for fine control of the rod temperature. It should be recognized, however, that the system temperature must be monitored using thermocouples at the grid/rod interface as opposed to the guide tube thermocouple due to the differential induced by the mechanical flow. It should be noted that the same temperature profile can be achieved by adding heating zones to the heater rod array (simulation C). Although the array of cylindrical heaters most closely replicates the in-cask environment and has been demonstrated as capable of delivering the necessary heat with very good control and response capability, it is also the most complex and expensive concept for fabrication and maintenance and is therefore not recommended.