Oxide Dispersion Strengthened (ODS) Steels for CANDU Supercritical Water-Cooled Reactor (SCWR) Fuel Cladding

Abstract

ODS steels incorporate nano-sized yttrium titanate particles for improved high temperature strength. It’s a unique strengthening mechanism for imparting good creep resistance to ferritic steels. Together with their low neutron absorption cross-section and good corrosion and SCC resistance, ferritic ODS steels are ideal candidates for SCWR fuel cladding material. ODS steels were prepared by mechanically alloying Fe-14Cr-Mo or W (wt. pct.) pre-alloyed steel powders with nano-sized yttria and titanium powder in a lab-sized attritor in 2-3 kg batches. The milled powders were retrieved from the attritor and placed in thick-wall containers under inert atmosphere, degassed at 400°C, sealed into composite billets, aged at 800°C and consolidated by extrusion at 900-1100°C. The resulting steel rods were characterized by advanced electron microscopy and mechanical testing. Hardness surveys conducted along the length of the rods showed high hardness (450 HV) when even dispersion strengthening was obtained; however, some rods were interspersed with transition to low hardness areas.