Performance of FeCrAl for accident-tolerant fuel cladding in high-temperature steam

Abstract

AbstractThe very high temperature (≥1400°C) steam oxidation resistance of thin-walled FeCrAl tubes is being investigated as an alternative to Zr-based alloys for enhanced accident-tolerant light water reactor fuel cladding. Initial work examined commercial FeCrAl with ~20% Cr in ramp testing with 1 min hold times at temperatures up to 1700°C. At 1400–1500°C, excellent oxidation resistance was observed with thin external alumina scales formed in contrast to the thick oxides formed on Zircaloy-4 under similar conditions. For an optimized FeCrAl with 13% Cr, one batch of tubing performed poorly at 1400°C, while the second batch formed a protective scale at 1400°C but was fully oxidized at 1500°C. Differences in performance between two test rigs suggest a role of gas velocity, and initial work on bulk alumina specimens has quantified an evaporation rate. However, some results suggest that melting is occurring well below 1500°C. This behavior is still being investigated.