Mg–Zr alloy behavior in basic solutions and immobilization in Portland cement and Na-geopolymer with sodium fluoride inhibitor

The dismantling of uranium natural graphite gas nuclear reactor generates a large volume of fuel cladding. The fuel cladding materials are based on Mg–Zr alloy for UNGG. The dismantling strategy could be to encapsulate these wastes into an ordinary Portland cement (OPC) or Na-geopolymer (alumino-silicate material) in a form suitable for storage. Corrosion behavior of Mg–Zr in OPC interstitial solution and activating solution of Na-geopolymer has been studied in the presence and absence of sodium fluoride as corrosion inhibitor. Electrochemical methods have been used to determine the corrosion densities. Results show that the corrosion densities of Mg–Zr alloy in OPC solution are one order of magnitude more important than in activating solution of Na-geopolymer and sodium fluoride addition decreases corrosion densities in OPC interstitial solution. Hydrogen evolution of encapsulated Mg–Zr alloy has also been measured in both OPC and Na-geopolymer and results show that Na-geopolymer matrix appears to be an attractive binder in term of corrosion performance.