Updated

A former U.S. nuclear regulator says cleaning up the wrecked Fukushima plant is a bigger challenge than the work he led at Three Mile Island and that ongoing radioactive water leaks are a minor part of that task.

Lake Barrett was appointed this month by plant operator Tokyo Electric Power Co. as an outside advisor to the decades-long decommissioning process. He led the Three Mile Island accident cleanup for nearly a decade as part of the Nuclear Regulatory Commission.

He said that the meltdowns in three of the reactors, massive radiation leaks and the volume of contaminated water at the Fukushima Dai-ichi plant makes it a more complicated and challenging clean-up.