Corrosion study of the BR1 fuel in highly alkaline conditions

This doctoral thesis focuses from a scientific viewpoint on the first route to be launched in regards to the disposal of the BR1 fuel because other routes involving the pre-treatments of BR1 fuel are commercially unbeneficial. This study firstly aims at finding a solution for the corrosion problem of the aluminium cladding of BR1 fuel in geological disposal. Because of the high corrosion rate of aluminium in the highly alkaline cementitious environment, this thesis revolves around the investigation of lithium salts for inhibiting the corrosion of aluminium in Portland cement (OPC) pastes (see Chapter 2). The corresponding objectives are defined as follows: 1. The corrosion inhibition effect of LiNO3 and Li2CO3 on AA1100 embedded in OPC pastes will be investigated to evaluate whether they can effectively retard the high corrosion rate. This corrosion rate study needs to be accomplished by different techniques in order to examine the validity of the results. 2. The corrosion inhibition mechanisms of LiNO3 and Li2CO3 need to be fully understood. Consequently, the corrosion process of aluminium embedded in Portland cement pastes with/without lithium addition needs to be known. 3. The advantages and disadvantages of using LiNO3 and Li2CO3 inhibitors need to be compared and the better option for the engineering application of geological disposal needs to be determined. 4. The influences of different experimental curing conditions and cell configurations on the corrosion process need to be understood. Besides, because of the significant impact of the capillary pores on the mechanical and transport properties of cement paste, the porosity evolution of cement pastes during the hydration and corrosion process needs to be investigated (see Chapter 5). The aims of the porosity study are identified as follows: 5. To innovatively combine General Effective Media (GEM) theory and Electrochemical impedance spectroscopy (EIS), in order to characterize the cement paste porosity. Mercury Intrusion Porosimetry (MIP) measurements will be performed to examine the reliability of this new combined methodology. 6. To the determine the relationship between the porosity variation of cement paste and the corrosion evolution of aluminium need to be understood.