Some of it is old from previous nuclear testing and some of it is new. I'm not sure either is very comforting at this point. MSNBC.com:
Experts had expected traces would be detected once crews began searching for it, because plutonium is present in the production of nuclear energy.
Plant operator Tokyo Electric Power Co. said the amounts found at five sites during testing last week were very small and were not a risk to public health.
TEPCO official Jun Tsuruoka said only two of the plutonium samples were believed to be from a leaking reactor. The other three samples were from earlier nuclear tests, he said. Years of weapons testing in the atmosphere have left trace amounts of plutonium in many places around the world.
