So don’t tell anyone, lest terrorists get ideas. Pity about the ordinary souls who breath it in without knowing.
Around August 2011 Japan for the first time admitted Fukushima reactor signature plutonium being found many kms off site. By September all such official plutonium reporting had ceased and in fact the full fission and fuel dispersal data remains incomplete. More data can be gleaned from European governmental agencies than can be gleaned from Japanese sources. The atmospheric transport of the radionuclides measured at a distance is a poor substitute for full disclosure of the inventory in the close in areas.
It smacks of Cold War secrecy lest the enemy (or host nation) learn of the actual radio poisons actually unleashed on the motherland.
Nuclear authorities have clearly learned from history. Which is precisely why the ordinary innocent of the world are doomed to repeat it.