Complex sentence: Efforts have been applied to initiate usage of thorium and its radioactivity as a power source; the earliest thorium-based reactor was made in U.S: the first core at the Indian Point Energy Center in 1962.
Split into simpler sentences: Efforts have been applied to initiate usage of thorium and its radioactivity. Usage of thorium as a power source has been explored; the earliest thorium-based reactor was made in U.S.: the first core at the Indian Point Energy Center in 1962.