The plant's operator Tokyo Electric Power Co (Tepco) said exposure to radiation levels in the No 3 reactor for four-and-a-half hours would exceed the emergency safety limit for power plant workers.
While the plant owners are responsible for managing efforts to limit the fallout of radiation leaks on site, it is FEMA that is in charge of off-site activities.
New rules imposed by the NRC require plant operators to install or improve venting systems to limit core damage in a serious accident and set up sophisticated equipment to monitor water levels in pools of spent nuclear fuel.
With questions about whether the plant can restart, mounting costs and who picks up the tab, "there is a practical limit to how much we can absorb of that risk, " Craver said.