Diffusion Between Zr–(Cr, Nb, Ta, Mo) and Cr–(Nb, Mo, Ta) Binary Systems for Accurate Lifetime Prediction of ATF

One of the very promising accident-tolerant fuel (ATF) claddings for light-water reactors (LWRs) consists of Zircaloy coated with chromium (Cr). The diffusion coefficients – both impurity (dilute) diffusion coefficients and interdiffusion coefficients – between Zr and Cr are essential for modeling the behavior of ATFs under operating and accident conditions as well as for accurate ATF lifetime prediction. A diffusion barrier interlayer of Mo, Nb, or Ta is also being explored to prevent accelerated diffusion/reaction between Cr and Zircaloy under accident conditions. This talk will show the results of a systematic diffusion studies of the Zr–(Cr, Nb, Ta, Mo) as well as the Cr–(Nb, Ta, Mo) binary systems at several temperatures ranging from 300 °C to 1200 °C to establish a reliable diffusion database for these binary systems to fill a knowledge gap that current exists due to insufficient data. The resultant diffusion coefficients to allow engineers and researchers to simulate the diffusion between Zircaloy and Cr with capabilities to include various thickness of interlayer (Mo, Nb or Ta) under various operating and accident conditions without or with neutron irradiation. Both the systematic dataset and the python code can be used to simulate various accident scenarios and operating conditions, thus optimize the design (interlayer selection and thickness as well as Cr coating thickness) and increase the robustness of Cr-coated ATFs against accidents.