A high performance TiO2@Ti3C2Tx MXene water vapor sensing material for diagnosing early SGTR accidents in nuclear power plants†

Abstract

The steam generator (SG) as a key piece of equipment in nuclear power plant servers for both primary and secondary systems. SG tube rupture (SGTR) events occasionally occur during pressurized water reactor operation and cannot be completely avoided. However, traditional leak monitors (such as the N-16 method) are not sensitive to small leak rate changes, and hence cannot be used for low-level leak rate detection under incipient fault conditions and are limited to post-accident analysis of significant releases. In this study, the utilization of Ti₃C₂T_x MXene for monitoring the micro rupture phenomenon of water vapor escaping from U-shaped tubes in a SG is reported for the first time. The experimental results demonstrate that the TiO₂@Ti₃C₂T_x, after undergoing partial oxidation for 2 hours, has a significantly enhanced gas sensing capability towards water vapor in an argon environment between 100 and 300 °C. In addition, its water vapor response time at as low as 100 ppm at 300 °C is less than 3 seconds and has excellent repeatability. The layered Ti₃C₂T_x MXene is beneficial for the adsorption and diffusion of water molecules, making it an excellent platform for conductive transport and carrier collection. TiO₂ nanoparticles formed by partial oxidation provide numerous gas adsorption sites, and the interlayer insertion of water molecules facilitates the interaction between water vapor and charged –OH groups in MXene. This behavior leads to a decrease in the dielectric constant and an increased electrical resistance due to an increased activation energy for electrons/holes transitioning to a free state. TiO₂@Ti₃C₂T_x nanosheets exhibit promising potential for trace water vapor detection and high-temperature environment sensing. Given the low concentration response and high safety, this type of water vapor sensor has great potential for early diagnosis of SGTR accidents.