WASHINGTON — Two years after the Fukushima nuclear accident in northern Japan, the United States government is using lessons from that disaster to rewrite its plans for responding to radiation contamination, focusing on long-term cleanup instead of emergency response. But the proposals have set off vehement opposition from critics of nuclear power.

On Monday, the Environmental Protection Agency expects to publish in the Federal Register a draft document that would change its long-standing advice to state and local governments about how to limit long-term exposure to radiation after a reactor accident or a “dirty bomb” attack. By reducing the projections for how much radiation exposure is likely in the years after such an episode, the proposal could also reduce the amount of contaminated land that would have to be abandoned.

A federally chartered research group will close its comment period on Monday on a draft report that it has prepared for the Department of Homeland Security and that lays out long-term cleanup standards.

In March 2011, a large earthquake and tsunami damaged the Fukushima nuclear plant, causing fuel at three of its reactors to melt and forcing the evacuation of 160,000 people from their homes. The Japanese are still debating how much cleanup is needed and when the level of radiation will drop enough for people to return.