Verification of the from model for zircaloy oxidation during high temperature transients

As the sheath of nuclear fuel elements in a water cooled reactor is one of the principal barriers against the release of fission products into the primary heat transport system, the modelling of the different phenomena that influence the sheath integrity is important. The computer subroutine FROM was developed to model Zircaloy-4 oxidation during an arbitrary high temperature transient. The Zircaloy thickness can contain up to three regions separated by diffusion controlled moving boundaries. Interface oxygen concentrations are not necessarily maintained at equilibrium values. The comparison of FROM predictions of layer thickness with a large number of experimental results from Kermforschungszentrum Karlsruhe (KFK), Oak Ridge (ORNL) and Chalk River (CRNL), showed very good agreement. The model is also successful in prediction of oxygen concentration distributions.