LINDA WERTHEIMER, host:
This is MORNING EDITION, from NPR News. I'm Linda Wertheimer.
RENEE MONTAGNE, host:
And I'm Renee Montagne.
As the radiation spreads from the crippled Japanese nuclear plant, a global network of sensors is tracking it across oceans and continents. The network was originally set up to detect nuclear weapons testing. Scientists now hope it can tell them more about the accident in Japan. Geoff Brumfiel is a reporter with the scientific journal Nature. He's been covering the nuclear emergency.
Mr. GEOFF BRUMFIEL (Reporter, Nature): The Comprehensive Test Ban Treaty Organization began setting up its monitoring stations about a decade ago. The eventual goal is to enforce a worldwide ban on nuclear weapons tests. Here's spokesperson Annika Thunborg.
Dr. ANNIKA THUNBORG (Comprehensive Test Ban Treaty Organization): We have currently over 280 sensors worldwide, monitoring underground, the atmosphere, the oceans for any sign of a nuclear explosion. And we're also sniffing the air for any sign of radioactivity.
Mr. BRUMFIEL: That now includes radioactivity from the Fukushima Dai-ichi nuclear power plant. Explosions at three reactors and a fire at a spent fuel pool have released radiation into the atmosphere.
Gerhard Wotawa is with the Austrian Meteorological Service, and has been studying data coming from the monitoring stations. He says there's no doubt what they're picking up is coming from Japan.
Dr. GERHARD WOTAWA (Central Institute for Meteorology and Geodynamics, Austria): Data like that, I mean, I've never seen in my career, so it is pretty much clear where it comes from.
Mr. BRUMFIEL: The sensors are registering radioactive elements like iodine-131 and cesium-137. These are byproducts from nuclear fission inside the core of a reactor.
Wotawa has been�feeding the data into computer models�that can forecast where the radiation will go. He also uses the models to work backwards and calculate the amount of material first released. Based on those calculations, he says the accident, in some ways, is roughly the size of Chernobyl.
Dr. WOTAWA: The daily release is comparable with what is, effectively, Chernobyl. Yeah. However, the effect of the power plant accident to Japan is not comparable with the effect of the Chernobyl accident to the former Soviet Union.
Mr. BRUMFIEL: That's partly because Chernobyl was located inland, and radiation contaminated land in all directions. Fukushima is on the coast, and winds are blowing much of the material out over the Pacific.
Wotawa's calculations are just an estimate, and not everyone agrees the accident is comparable to Chernobyl.
Dr. HARRY MILEY (Nuclear Physicist, Pacific Northwest National Laboratory): If I had to guess, I would say that the release levels were more like Three Mile Island and less like Chernobyl, but we'll see as time goes forward.
Mr. BRUMFIEL: Harry Miley is a nuclear physicist at Pacific Northwest National Laboratory in Washington state. He says analyzing the types and amounts of radioactive material picked up by the sensor network will tell researchers around the world more about what happened inside the reactors of Fukushima.
Dr. MILEY: We might determine things like what was the temperature of the material when the radioactivity was emitted, which materials it was. There's three reactors, and there's spent fuel pools and so forth. They're all potential sources. And we should be able to nail down which source is which.
Mr. BRUMFIEL: For now, maybe the only way to tell what's happened. Radiation levels on the site are far too high to take a direct look. The sensors should also provide people with a sense of reassurance. Even though the radiation from the plant has been picked up across the United States, Miley says that the levels aren't dangerous.
Dr. MILEY: The highest detection that we've gotten in the U.S. has been far lower than the natural radioactivity that's normally there, so I don't think that there's any increased risk to the U.S. public.
Mr. BRUMFIEL: And there's more good news. The latest readings here in America seem to indicate that radiation from the plant is falling. Miley is hopeful that the worst of the accident may be behind us.
Geoff Brumfiel, NPR News.