• In PWRs it is found the Zircaloy-4 no longer meets corrosion and hydriding needs; therefore virtually all current PWR cladding use a zirconium alloy containing niobium. Table 4.11 lists materials currently being explored for use as cladding and structural materials, with the most widely used to date in the West, in addition to Zircaloy-4, being M5 and ZIRLO.

• For BWRs, Zircaloy-2 cladding, with various heat treatments to optimize the second phase precipitate size and distribution, remains the standard for BWR components. However, new channel materials are currently being explored to meet the challenges of channel bowing (described in the next chapter and in Garzarolli et al., 2011a). Table 4.12 lists some of those materials and heat treatments currently under development and early usage.

• Other trends and needs are given in the appropriate section of the next chapter.