STEVE INSKEEP, Host:
As NPR's Richard Harris reports, the material came from the reactors themselves, not from the pools of used fuel that had been a major source of concern.
RICHARD HARRIS: Per Peterson, chairman of the nuclear engineering department at the University of California Berkeley, says this tells him a lot about the nature of the accident that led to those releases.
PER PETERSON: Because there's iodine, this certainly was material that had come out of the reactors, not the spent fuel pools, because in those cases, the iodine-131 is pretty much completely gone.
HARRIS: Peterson says closer study of the isotopes will also help engineers figure out exactly what went wrong inside the reactors - for example, the temperature there at the time of the releases.
PETERSON: Of course, we can't go in and look at it inside the reactors, and so we need to gather as much evidence as possible, because this will aid in the subsequent cleanup effort as we move into that phase of this accident.
HARRIS: It's also good news for people who live within 100 miles of the plant. They have been exposed to higher doses of radiation since the accident. The amounts vary a lot, depending upon location. But Gerhard Proehl at the International Atomic Energy Agency says a wide area is now experiencing radiation that's many times higher than natural background levels.
GERHARD PROEHL: So, you may worry about that, and these levels are really are high. However, they will not remain such high.
HARRIS: Per Peterson at Berkeley says, fortunately, that's contributing just a small fraction of the radioactivity in the region.
PETERSON: We still need to see how things might change going forward. But as long as things continue on the current trajectory, we should see these radiation levels dropping off steadily over time, because they're still being dominated by the shorter-lived radioactive species.
HARRIS: Richard Harris, NPR News, Tokyo.
INSKEEP: Keeping all the news in perspective, it's MORNING EDITION, which you hear right here on NPR News.
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