The utility company invested about 570 billion yen ($3.7 billion) in safety enhancements, including raising seawalls to 29 meters and reinforcing earthquake resistance measures.
The boiling water reactor, which shares the same design as the ill-fated Fukushima facility, received approval from Japan's Nuclear Regulation Authority in 2020 after meeting stringent safety requirements.
During the 2011 disaster, the plant's emergency power generators were damaged by a 13-meter tsunami, though it achieved cold shutdown through a functioning external power source.
The restart comes as Japan pushes to revive its nuclear power industry amid energy security concerns, while local communities remain divided over nuclear power generation. Tohoku Electric plans to decommission the facility's No. 1 reactor by fiscal 2053.
