CFD design and mock up test for heat removal using cylindrical rods mounted on a vertical plate - Presentation

The increasing of burn up spent fuel leads to substantial residual power. To maintain a reasonable cooling time before transport, casks with high dissipative capacity need to be developed. In order to achieve thermal dissipation of about 70 kW in a 12 PWR fuel cask, the outer surface of the cask must be equipped with high efficiency fins. In general, heat removal from nuclear casks at high heat load is achieved using various types of fins working in natural convection. The fins shapes are usually limited by manufacturing considerations. The improvement of automation associated with the electric capacity discharge process for welding pin cylinders led us to examine the thermal performance of using long copper cylindrical rods to make a large exchange area at the outer surface of the cask. The main technical interest is that it offers good thermal performance regardless of the general orientation of the cask, which is an important point to be addressed after an accidental drop and a question generally raised by safety authorities. In order to get a quick preliminary design of a rod’s density and arrangement to reach a target value of global heat exchange performance, model and tests were conducted with horizontal cylindrical rods welded on flat vertical surfaces. Computational Fluid Dynamic preliminary design was a good aid for matching both vertical and horizontal orientation constraints, as well as assessing relatively good predicted values of global heat coefficient.