Effects of Irradiation on the Tensile Properties of Nb-1 Zr

Abstract

The alloy Nb‐1 wt % Zr (Nb‐lZr) has been selected for several in‐core applications in the SP‐100 reactor. Data on the effects of fast neutron irradiation on the tensile properties of Nb‐lZr at proposed SP‐100 operating temperatures are required to make certain that irradiated components have adequate ductility to preclude brittle failure during reactor transients or overpower conditions. Subsize (SS‐1) tensile samples of Nb‐lZr with average grain sizes of 22 and 73 μm were irradiated up to end‐of‐life fluence at 1290, 1350, and 1400 K in temperature‐controlled lithium filled capsules in the Fast Flux Test Facility (FFTF). For tests at 300 K, irradiation resulted in small to modest increases in 0.2% yield strength, no change in ultimate strength, and modest decreases in uniform and total elongations. After irradiation, total elongations remained high at 16 to 25%. At 300 K, the magnitude of the changes due to irradiation increased with increasing fluence and irradiation temperature. For material irradiated at 1290,1350, and 1400 K and tested at the irradiation temperature, the changes in tensile properties were less than the changes observed at 300 K, and the strength and ductility properties were within the scatter band for unirradiated Nb‐lZr. Total elongation remained very high at 32 to 37%. At 1290 to 1400 K, the magnitude of the changes due to irradiation decreased with increased irradiation temperature. Results were the same for both grain sizes. After irradiation at SP‐100 operating temperatures, Nb‐lZr exhibited more than adequate ductility to preclude brittle failure under any anticipated SP‐100 loading conditions.