The government on Friday lowered the threshold for evacuating residents during accidents on nuclear vessels, bringing it in line with accidents at atomic power plants.
Under the new rules, residents will begin evacuating when radiation exceeds 5 microsieverts per hour in areas near nuclear-powered aircraft carriers or submarines — significantly lower than the previous 100 microsieverts per hour.
The government also revised its emergency manual to reflect the change, and local authorities will now order or advise residents to leave based on the new rules.
Cities hosting U.S. Marine Corps bases with nuclear vessels are Yokosuka, Kanagawa Prefecture, Sasebo, Nagasaki Prefecture, and Uruma, Okinawa Prefecture.
The Cabinet Office had been working to revise the standards after disaster management minister Taro Kono instructed it to do so last month.
The government is also eyeing further amendments since discrepancies between nuclear vessel accidents and nuclear plant accidents still exist.
For example, people within a 30-km radius of a nuclear plant are urged to stay indoors during an accident, while only those within a 3-km radius of a nuclear vessel accident are urged to do so.
The rules for power plant accidents were revised in the wake of the 2011 Fukushima disaster.