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Kai Vetter (left), a professor in the department of nuclear engineering, inspects a radiation monitor on the roof of Etcheverry Hall with Scott Werwath and Zirui Jiang at UC Berkeley on Friday, March 4, 2016.[url=]... more[/url]
In the half decade since a nuclear power plant in Fukushima, Japan, melted down, scientists have found no levels of nuclear radiation along the California coast that would be harmful to humans.
Kai Vetter, a UC Berkeley professor of nuclear engineering, assembled a team of students and colleagues soon after a 9.0 earthquake and tsunami five years ago Friday heavily damaged the Fukushima Daiichi nuclear power station on Japan’s Pacific coast, allowing radiation to seep into the atmosphere. Their mission was to test for the presence of harmful radiation that might find its way to California.
“When it became clear that there were major releases of radiation there, we became very serious about what the effects could be here,” Vetter said. “We started to set up tools and instruments here to see the radiation coming across the Pacific.”
Over time, his team found nothing alarming, Vetter said.
“Most people who make cross-country flights choose to be exposed to a larger amount of radiation than what they’d be exposed to from Fukushima’s effects here,” he said.
Initially, Vetter and several students laid out a tarp and buckets on the roof of UC Berkeley’s Etcheverry Hall to test rain samples for radiation.
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In the following weeks, spanning into the following years, Vetter’s team tested everything from rainwater — in increasingly formal ways — to local cow’s milk, fish from nearby markets and kelp populations.
Trace amounts of the radiation from
the Fukushima catastrophecontinue to linger, especially along the coast, but even at their peak, the radiation levels in the Bay Area never presented any immediate harm. The levels of radiation were so low that they weren’t significantly different from the natural radiation people are exposed to from drinking a glass of milk or living in a brick building, Vetter said.
Separate study
As Vetter and his group were doing their work, Ken Buesseler, a radiochemist with Woods Hole Oceanographic Institution, went to sea to track the radiation released into the ocean from the Fukushima accident.
He collected water from the Pacific near Japan and at various points along the way as the radiation made its way to the West Coast. At a dock next to Fukushima at the peak of the release in April 2011, Buesseler found levels of radioactive cesium in the range of 50 million becquerels per cubic meter.
“Release in the 50 million range is unprecedented,” Buesseler said. “We’ve never seen an event put so much cesium in the ocean. Thankfully, that did not continue … and levels are lower on our side of the ocean.”
Along the California coast, he recorded levels of radiation from the disabled power plant in the range of 2 to 10 becquerels per cubic meter, slightly higher than the amount found naturally in the ocean before the event. There has been no evidence of significant impact, he said, on marine life or humans from that radiation.
“Like putting a drop of dye in your bathtub,” Buesseler said, the dangerous levels of radiation from Fukushima dissipated as they fanned across the ocean, absorbed by a combination of air, water and other matter.
Some types of radiation from Fukushima decayed along the way because they had shorter half-lives, scientists said. And, Buesseler said, it took about four years for the radiation to travel the nearly 5,000 miles across the ocean to the West Coast.
Lessons of Fukushima
Vetter and Buesseler said they learned things from the meltdown that opened their eyes. Vetter pointed to a lack of information that should have been available to the public about the radiation that was making its way to the West Coast. To make up for it, he and his research team developed
RadWatch, which posts all of its data online for the public to view, with contextual comparisons to allow the levels to be better understood.
Both scientists said more data are needed, but Vetter said, “Just providing information is not sufficient. … You have to make sure the people can use the information to make developed and informed decisions.”
They also learned that the general public has a basic misunderstanding of radiation. Vetter said, for example, people may not realize that they are exposed to radiation constantly and that levels of leftover nuclear radiation, such as that which leaked from the Fukushima plant, may be lower than naturally occurring levels in everyday life.
“We are living in a world full of radioactivity,” Vetter said. “People believe that a no-radioactivity world is possible, and in our universe there is not a single place with no radioactivity.”
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发表于 2016-6-27 18:21:47
