Oxidation of Advanced Zirconium Alloys in Oxygen in the Temperature Range 600-1600°C

Abstract

The oxidation kinetics of the classic pressurized water reactors (PWR) cladding alloy Zircaloy-4 has been extensively investigated over a wide temperature range. In recent years, new cladding alloys optimized for longer operation and higher burn-up are being increasingly used in Western light water reactors (LWR). These alloys were naturally optimized regarding their corrosion behavior for operational conditions. The publicly available data on high temperature oxidation of the various cladding materials are very scarce. Therefore, at FZK an experimental program on the high-temperature behavior of different cladding alloys presently used has been started. This paper presents the results of a first test series with Zircaloy-4 as reference material, Framatome Duplex cladding, Framatome M5 and the Russian E110 alloy. The first two are Zr-Sn, the latter two Zr-Nb alloys. All materials were investigated in isothermal and transient tests in a thermal balance under argon-oxygen atmosphere. Strong and varying differences (up to 500%) of oxidation kinetics between the alloys were found till 1000 °C, where the breakaway effect plays a role. Smaller but still significant differences (20–30%) were observed at higher temperatures. Generally one can say that the advanced cladding alloys here studied show also a favorable behavior at high temperatures during accident scenarios.