What: The U.S. Nuclear Regulatory Commission approved the reopening of a nuclear power plant near Toledo, Ohio, even before completion of an investigation of mysterious cracks in the concrete protecting its reactor.

Why: The commission said the plant’s owner gave them “reasonable assurance” that the cracks don’t pose a danger. Meanwhile, the owners have until the end of February to find out what caused the sudden cracks.

Who: The Union of Concerned Scientists, a watchdog group, questioned whether the walls were built to be strong enough. U.S. Rep. Dennis Kucinich, D-Cleveland, said there were still too many unanswered questions.