Characterization of the conductivity of metal-oxide interface of zirconium based fuel cladding at low and high burnups

In this study the conductivity/resistivity of oxide formed on Zircaloy-2 nuclear fuel cladding is measured. The same cladding grade (LK3/L) is used to compare the oxide formed after short and long residence times, respectively 3 and 9 cycles, in a Boiling Water Reactor (BWR). The oxide in the vicinity of the metal-oxide interface is studied. The measurements were carried out using a novel technique developed at PSI, using micromanipulators (micromanipulator) inside a FIB/SEM to probe different thicknesses of oxide and hence directly measure the resistance and calculate the resistivity of that thickness of oxide. The results from the 3 and 9 cycle oxides are compared. It is demonstrated that the resistivity of the oxide in the vicinity of the interface of the 9-cycle cladding increases with distance from the interface, much faster than that of 3-cycle cladding to a maximum level. The study is correlated to previous work, performed at PSI, characterizing these 2 materials by EPMA and other techniques.