Oxidation Behaviour of CZ Alloys Under High Temperature Steam

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Abstract CZ Alloys, including CZ1 and CZ2, are new advanced zirconium alloys developed by China General Nuclear Power Group. This paper presents the oxidation behaviour of CZ Alloys and Zircaloy-4 in flowing steam. A SETSYS Evolution TGA (ThermoGravimetric Analyzer) is used for the high temperature testing. The weight gain of specimens was measured real time in the temperature range of 800∼1200 °C for 3000∼5000s. The hydrogen content after oxidation at 1000 °C was measured. CZ1 (Zr-Sn-Nb alloy), CZ2 (Zr-Nb alloy) and Zircaloy-4 (Zr-Sn alloy) claddings which contain different types of alloying elements have similar oxidation behaviour at above 1100°C but show significant difference at lower temperatures. The weight gain of CZ Alloys are compared with high-temperature oxidation parabolic rate laws of fuel cladding materials which have been used in many LOCA analyses, the Baker-Just equation and the Carthcart-Pawel equation. The results show that the Baker-Just equation is conservative for CZ Alloys and the Carthcart-Pawel equation is more accurate at above 1100°C. The oxidation rate constant and the rate exponent are calculated at each temperature by non-linear fittings.

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