A Thermal Analysis of Hot Spots on Fast-Reactor Fuel Cladding Due to Deposition of Low-Conductivity Materials

The formation of hot spots in fuel cladding due to the deposition of a low-conductivity heat-generating fuel or due to fission-gas-jet impingement is a very credible event and can significantly influence the probability for slow fuel-failure propagation in a subassembly of a liquid-metal fast breeder reactor. By assuming steady-state conditions, a general expression is obtained for the temperature distribution in these hot spots. As special cases, expressions are obtained for temperature distributions in hot spots caused by fission-gas-jet impingement and partial or total channel blockages by fuel debris. A partial verification of the model for thermal analysis is provided by comparing predictions for the temperature distribution in the gas-jet impingement region to the available experimental data.