Mechanical Performance Assessment of Independently-Developed Zirconium Alloy Under RIA Condition

Reactivity-initiated accident (RIA) is postulated design-basis accidents (DBAs) in light-water reactor (LWR). Moreover, Pellet-cladding mechanical interaction (PCMI) can cause a failure of the cladding in the early transient. In recent RIA regulatory guide released by NRC which points out that PCMI failure threshold depends on total hydrogen content in cladding during RIA. In order to evaluate the performance of independently-developed zirconium alloy under RIA conditions, the mechanical behavior and the fracture of 2 different cladding tubes (CZ, and SR (Stress Relief) Zr-4) with different hydrogen contents are investigated under thermal-mechanical loading conditions representative of PCMI during RIAs. Ring tensile tests are performed at room temperature, 350 °C on 2 different materials containing various hydrogen concentrations up to 1000 wt. ppm. Test results indicate that the ductility of the material decreases with increasing hydrogen content at room temperature due to damage nucleation by hydride cracking, the ductility and strength results of SR Zr-4 have a good agreement with reference paper, confirming the rationality of experimental method applied and reliability of test facilities. According to the results of Zr-4 and CZ, a conclusion can be made is that the ductility of independently-developed zirconium alloy (CZ) is better than Zr-4, which can provide the technical support when licensing.