DEVELOPMENT OF IMPROVED ZIRCONIUM ALLOYS FOR USE IN SUPERHEATED WATER AND STEAM

A zirconium-base alloy with corrosion resistance and strength superior to zircaloy-2 in 680 deg F water and 750 to 900 deg F steam is being sought in a development program. Approximately 100 binary compositions were screened by corrosion testing in 680 deg F water and 750 deg F steam; selected compositions were exposed to 900 deg F steam. Data obtained from these studies indicated a number of highly promising bases for ternary alloy investigation. On the basis of 4800-hr tests, a number of ternary materials were found to satisfy the program objective for the 680 deg F water environment. The compositions are based on Zr- 1 Sb, Zr-1 Cr, Zr--0.5 Nb, and Zr-0.5 Sn with small additions of Te, Ge, Cr, or Fe. Further, the hydrogen pickup characteristics of these alloys were improved over zircaloy-2, but acceptability on this basis remains to be demonstrated by mechanical property evaluation. For 3000-hr tests in 750 deg F steam, the ailoys Zr--3Cr-1Fe, Zr-3Cr--0.25Te, and Zr--1V--1Fe were superior to zircaloy-2 on the basis of corrosion resistance and strength; however, hydrogen pickup properties were about the same as Zircaloy-2, which is considered excessively high. In 900 deg F steam, a few materials were greatly superiormore » to Zircaloy-2 but weight gains were very high. (auth)« less