Performance evaluation of sodium resistant mortars as sacrificial layer in fast breeder reactors

In fast breeder nuclear reactors, sodium is used as a coolant. Accidental spillage of sodium at 550°C and above can cause damage to the structural concrete. For this reason, a sacrificial layer of limestone aggregate concrete is provided over the conventional siliceous aggregate concrete. In spite of extensive understanding of the chemistry of interactions, limited information is available on the microstructural description of deterioration, including creation of mineralogical polymorphs and growth of microcracks. To study and improve the performance of the sacrificial layer in the presence of hot liquid sodium, a research project is taken up at llT Madras. This paper presents overview of the state of the art, research needs and motivations supplemented by results and analysis of first phase of work performed at IIT Madras, which includes thermal performance evaluation of limestone mortars. This study will be followed by an evaluation of sodium attacked mortars.