The mass concrete, characterized by dimensions necessitating measures to manage heat generation from cement hydration and associated volume changes to minimize cracking, is crucial in hydropower plants enduring a constant flow of fresh water. Ensuring restricted crack width control in the reinforced concrete structures within hydropower plants is essential for both performance and durability over the designated design life. Furthermore, massive reinforced concrete (MRC) structures may experience delayed ettringite formation (DEF) if the peak temperature during cement hydration exceeds 80 ℃, emphasizing the need for thermal modelling and thermal crack analysis during the design stage. This study employs numerical simulation, specifically using the b4cast software, to analyze a substantial MRC structure in a hydropower plant regarding the heat of cement hydration. The results obtained from b4cast are validated against CIRIA C766. The thermal modelling is fine-tuned with hotbox tests of 1m3, designed for the MRC structure’s mix. Thermal crack analysis for MRC considers the structure’s geometry, restraint conditions, and ground conditions using both b4cast and CIRIA C766. The study aims to establish a method statement for thermal modelling and crack analysis applicable to MRC structures in hydropower plants.