Acoustic Mismatch Theory for Heat Flow Across Fuel-Cladding Interfaces in Fast Reactors

A simple acoustic mismatch model can predict heat flow across solid/fluid interfaces at high temperatures in terms of known physical properties of the system. Using this model, the thermal boundary conductances of the various interfaces involved in heat transfer from the fuel pellet to the cladding of fast reactor fuel rods are estimated. The typical values of fuel-cladding gap conductance of helium-bonded fast reactor fuel rods quoted in the literature are in reasonable agreement with estimates obtained from this model. In addition to its striking simplicity, an interesting and novel feature of this fundamental approach is the prediction of a marginally high gap conductance for a helium-bonded oxide fuel rod over its carbide counterpart.