Radiation effects in ferritic steels

Ferritic steels were studied in Mol (Belgium) for fast reactor core material applications. For canning material application, dispersion strengthened ferritic steels were developed. Irradiations were conducted from room temperature to 7000C in the material testing reactor BR2 to investigate the high temperature irradiation embrittlement. In all cases, the ferritic steels were more resistant than the austenitic ones, the difference being very large when the tensile tests were conducted above 5500C. Most of the high fluence fast reactor irradiations are still running. In the few available samples, the density change is small and no single void in the ferritic phase has been detected by transmission electron microscopy. Fuel pins canned with dispersion strengthened ferritic steels were irradiated in the BR2. A burn-up of 120.000 MWd/t was reached in the oxide pins before a failure occurred despite a very high smeared density (90%), a high temperature (6700C) and a high linear power (560 W/cm). This very encouraging result led to the decision of irradiating ferritic steel canned fuel pins in a fast reactor in realistic conditions