TRANSIENT THERMAL PERFORMANCE OF A RADIALLY DILUTED AND CENTRALLY COOLED NUCLEAR FUEL CELL

Steady and unsteady heat transfer in a radially diluted and centrally cooled nuclear fuel rod are investigated numerically. The nuclear fuel cell is radially diluted by the addition of a non-heat-generating material of high melting point, high specific heat, and high resistance to oxidation and ignition, with the intention of increasing its time delay before melting, when convection is totally lost. Results show a great reduction in the maximum wall temperature under steady operation and a substantial increase in the time delay under transient conditions, with its value increasing with increasing the amount of added diluent. Moreover, results indicate the presence of an optimum value of the ratio of inner to outer channel flow rates for which the maximum inner and outer wall temperatures are minimum. Finally, the distribution of the added diluent is shown to mildly affect the steady and unsteady performance of the reactor.