In this presentation, I will focus on the principles of nuclear power with thorium as a starting material instead of uranium. Thorium itself is not fissile and cannot directly be used as a reactor fuel, but it can during irradiation be converted to one of the best reactor fuels we know, namely Uranium-233. For this to happen in a self-sustaining way we need a special reactor working with a fluid fuel instead of a solid one as is being applied in current day nuclear power plants. In my presentation I will explain the principles of the Molten Salt Reactor working with a fluoride fuel salt and that of the thorium fuel cycle, and will explain the differences with current day technology in the fields of nuclear safety, waste generation, fuel cycle issues and others. I will also identify the fields we work on at TU Delft.