Radioactive Traces Are Miniscule, Team Finds

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Correction Appended

A brand-new red vacuum cleaner sits on the floor. Filter cartridges possessing samples of the air line the counter beside plastic water bottles filled with rainwater.

In the laboratory of Kai Vetter, a UC Berkeley associate professor-in-residence of nuclear engineering, graduate students are analyzing the samples gathered by these tools, purchased from Home Depot, as part of a search for traces of radiation in California following the nuclear crisis in Japan.

Five days after the magnitude-9.0 earthquake that struck Japan on March 11 and set off a chain of events including a tsunami, floods and a nuclear crisis, a team of UC Berkeley nuclear engineers set to work in the basement and on the roof of Etcheverry Hall to measure the radiation that was released from the four damaged nuclear plants in Japan.

The records have so far shown miniscule amounts of radiation in Berkeley's air, milk and water supply, despite the public worry that the West Coast would suffer radiation contamination.

"You have to drink about 500 to 600 liters of fresh rainwater to get the same dose (of radiation) as a transcontinental flight," said Vetter, who is also a staff scientist at Lawrence Berkeley National Laboratory.

The team collects the rainwater using a tarp, samples the air using a vacuum cleaner set up on the roof of Etcheverry and tests both water flowing through Strawberry Creek and tap water.

The radiation, spread to the United States' coast by wind and rain, follows a natural pathway from the rain to creeks to larger reservoirs, such as the San Francisco Bay. This phenomenon is one that the researchers hope to study further in coming weeks by tracing the radiation's route, explained nuclear engineering graduate student Brian Plimley.

On Wednesday, the team announced that they had found traces of radiation in tap water and locally bought milk, though it was only detected because of the sensitivity of the equipment, not because the radiation was a significant amount. Fears about contaminated food and water are unnecessary, Vetter said, and are exactly what he and his team are trying to put to rest by sharing with the public their raw data and analysis of water and air samples.

In the two weeks since they converted a laboratory in the basement of Etcheverry into a full-time radiation-testing center, the team has found within their samples the isotopes of iodine-131, tellurium-132, cesium-134 and cesium-137 - the same isotopes released from Japan's nuclear plants. Both iodine-131 and tellurium-132 have very short half-lives, meaning they fully decay and disappear in a matter of days.

Though both cesium-134 and cesium-137 levels increased slightly in recent days, their concentrations are low enough so as not to be a concern, Vetter said. Their half-lives, however, are significantly longer at two years and 30 years, respectively.

Still, the levels of radiation are too low even to be detected by conventional tools like a Geiger counter.

"People come in with Geiger counters to look at our samples, and we have to tell them you will not see any difference," Vetter said. "The only thing you will see is a variation of background radiation because we are living in a world that is radioactive. Everything is radioactive. If you don't like it, you have to go to another universe."

Because of this, the team has to use highly sensitive equipment that blocks out existing radiation to detect the radiation that comes specifically from Japan.

In coming weeks, the researchers will continue to take measurements and post them on their website, both to assuage the concerns of the public and to further explore the nature of radiation.

The researchers said they have received some positive feedback because of their work. One man called the lab, asking what he could do to help and ended up buying the team a pizza.

"A lot of people are saying 'thanks for doing this,'" said Mark Bandstra, a nuclear engineering postdoctoral researcher on the team. "Some government agencies were just saying it's safe, but they weren't giving any real numbers."


Correction: Monday, April 4, 2011
A previous version of this article incorrectly referred to the nuclear leak as a nuclear meltdown.

The Daily Californian regrets the error.

Claire Perlman is the lead research and ideas reporter. Contact her at [email protected]

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