Corrosion and dimensional behavior of Zr-Sn-Nb-FeCrV alloys with varying conditions and compositions having been tested out-of-pile and after irradiation in “hot” PWRs for long exposure times (up to 9 annual cycles) and very high burnups (98 MWd/kgU). The exploratory program for alternative zirconium-based alloys performed on fuel rod cladding and corrosion coupons allowed an understanding of the separate effects of composition and fabrication and yielded Zr alloys appropriate for high-burnup, high-fuel-duty application.

In the alloy system Zr-Sn-FeCrV, the corrosion rate decreases with decreasing Sn and increasing Fe+Cr+V content, much more pronounced in-PWR than out-of-pile. The addition of Nb exhibits a similar effect as Fe+Cr+V, but increases corrosion in general if Sn > 0.4%. Zr-Sn-FeCr alloys are sensitive to the thermal treatment during fabrication and therefore have to be fabricated according to a well-defined A-parameter to achieve high corrosion resistance. Nb and V containing Zr-Sn-Fe alloys allow fabrication in a larger A-parameter range. The beneficial effect of high cold work and a low degree of recrystallization on corrosion is significantly reduced if the Sn content is low.

At high fluences, some alloys exhibit an increase in the corrosion rate. With decreasing Sn content, the onset of the acceleration is shifted towards higher fluences and its extent is reduced. Alloys containing Sn < 0.2% do not exhibit increased corrosion induced by high fluences, at least up to 1.6E22 cm^-2, E > 1 MeV.

Irradiation induced and thermal creep depend on the content of Sn, Nb, and O in solid solution, on the grain size, and on the degree of recrystallization.

Growth of stress-relieved and partially recrystallized fuel rod claddings strongly depends on the Sn content: it is low if Sn < 0.5%. In addition, the C content and the grain size affect growth of fuel rods.