FILE - In this March 23, 2016, photo, a worker checks the radiation level on barrels in a storage of nuclear waste taken from the 4th unit destroyed by explosion at the Chernobyl nuclear power plant, Chernobyl, Ukraine. Among the most worrying developments on an already shocking day, as Russia invaded Ukraine on Thursday, was warfare at the Chernobyl nuclear plant, where radioactivity is still leaking from history's worst nuclear disaster 36 years ago.(AP Photo/Efrem Lukatsky, File)