SPECIFIC ZIRCONIUM ALLOY DESIGN PROGRAM. Quarterly Progress Report Nos. 18 and 19.

Abstract

A Zr + 2. 0 at.% Cr + 0. 16 at.% Fe alloy (Zr-Cr) is being evaluated as nuclear fuel cladding. Zr-Cr alloy-clad fuel rods are being irradiated in the Consumers Big Rock Point\reactor to a target exposure of 15, 000 to 20,000 MWd/T. The rate of fuel burnup has been approximately •aoo MWd/TU (average) per month of full-power operation. The Zr-Cr alloy-clad fuel rods have accumulated a totnl of approximately 6 000 MWd/TU avP.rage exposure. as of January 31, 1968. This corresponds to about 5100 hours of high-tem;Jeraturc, full-power, reactor operation. The long-term, out-of-pile, loop corrosion tests are continuing satisfactorily. Zr-Cr alloy samples are being tested in the loop under heat transfer conditions, and have accumulated about• 3800 hours exposure as of January.17, 1968. Mechanical test results, burst and tensile tests, indicate that the fine-grain Zr-Cr tube material is stronger an:d less rluctile than the usual Zircaloy-2 tubing; however, the hightemperature stress rupture performance of the fine-grain size Zr-Cr is poorer than that of the Zircaloy-2 materials. vi ..