State and local emergency officials are in charge of the immediate response. The Federal Government assists with all the resources it has. The Federal, State and local responders coordinate closely. Federal Government follows existing emergency response plans for maximizing resources, coordinating across all levels of government and helping those in need. Like any other insurance, the specific amounts will be determined based on losses incurred. 

The crops will be instantly unsafe, because the air will be radioactive since a nuclear power plant meltdown happens when radiation leaks and contaminates the air in the form of gas. It can make the food unsafe to eat and crops won't be able to grow properly.