Real-Time Nanogravimetric Monitoring of Corrosion in Radioactive Decontamination Systems

Abstract

Monitoring and understanding of corrosion on nuclear sites is key to safe asset management (predicting plant life, assessing efficacy of corrosion inhibitors for plant lifetime extension) and supporting informed choice of decontamination methods for steels due for decommissioning. Recent advances in Quartz Crystal Nanobalance (QCN) technology offer a means to monitor corrosion in-situ in radiologically harsh environments, in real time and with high sensitivity.Oxalic acid has been widely used in nuclear facilities as a corrosion inhibitor for carbon steels and as a decontamination cleaning agent due to its ability to remove rust from the surface of ferritic metals and alloys. As an exemplar system for decontamination, the corrosion behavior of pure iron samples in 1 wt% oxalic acid solution has, for the first time, been measured in simulated radioactive environments in real time, in situ using the QCN. Results show that the QCN is a promising tool for studying the efficacy of oxalic acid decontamination agent formulations with the sensor providing useful mechanistic information regarding decontaminating agent mode-of-action derived from the mass change (gain or loss) in real time when a quartz crystal is immersed in oxalic acid solution in simulated and non–simulated radioactive environments.

Real-Time Nanogravimetric Monitoring of Corrosion in Radioactive Environments

“…To this end, the oxalic acid concentration being used has been reduced to 1 wt% from the 4-8 wt% range typically used during decontamination campaigns hitherto [42]. Using QCN, the rates of corrosion of mild carbon steel surrogates have been measured in the presence of these oxalic acid-based decontamination solutions and both the removal of iron oxide corrosion product and the formation of a protective layer of ferrous oxalate at the metal surface have been observed [91], [107]. Studies have been extended to newer decontamination solution formulations including alkaline and acid permanganate solutions and oxalic acid / nitric acid blends.…”

Development of Cleaning Evaluation Application Using Hue Change as a Parameter

“…In the removal of iron rust on industrial surfaces, immersion removal using acid agents is commonly used (Daurelio et al, 1997;Lee et al, 2007). Among them, oxalic acid is widely used (Tzagkaroulakis et al, 2017) and is expected to provide a high cleaning rate at low concentrations.…”