About 200 people packed into UCSB’s Kohn Hall on Wednesday night to hear brilliant minds explain the nuclear events in Japan and their implications. Hosted by the Kavli Institute for Theoretical Physics, director and Nobel Prize winner David Gross started the talk on a personal note.
Gross said he and his wife had been in Tokyo the day of the earthquake. Unlike earthquakes in Southern California that initially shake and lose power, “this one shook and got bigger,” he said, adding that the initial quake lasted six minutes.
Looking out of his hotel room when the tremor stopped, Gross said he was surprised at what he saw.
“You couldn’t see any damage at all,” he said of the city scape. “But we had no idea what was coming, and that’s why you’re all here.”
Assuring the audience that his presentation wasn’t for physicists but the general public, assistant professor of physics Ben Monreal launched into an erudite but interesting glimpse at the process of radioactivity. He began by explaining how elements become radioactive, and the basics of fission, the energy-producing process of nuclear power plants.
He said all elements want to be stable, so radioactive compounds will try to toss off extra neutrons to get back to that state. When they do, those neutrons can damage cells, such as DNA, that they come into contact with.
Monreal walked through the measurements of radiation, one of the more complex topics of the night, but perhaps the most insightful.
He explained that everyone in the room was being irradiated somehow, whether from the food they had eaten, a spare radon molecule floating through the air or from the radiation in the atmosphere, adding that the time and intensity of that exposure is what matters. Radiation is measured in units per hour called sieverts, and even smaller, millisieverts. Five sieverts per hour of radiation is lethal, he said.
Chernobyl first-responders were exposed to 10 sieverts per hour, which left 30 people dead and 200 hospitalized. Fukushima levels have been measured at 400 millisieverts per hour, which could bring about death if exposed for 12 hours.
Another insightful moment came as Monreal explained the differences among Three Mile Island, Chernobyl and Fukushima.
At Three Mile Island, he said, the container around the reactor core became full of pressure, and some of the gases were vented. Gases such as xenon, radon and krypton escaped in the steam, but no deaths or health effects resulted from the release.
Fukushima’s reactor container is leaking some of the water used to cool the core, but the real problem begins when that water mixed with fuel catches on fire and smoke is released.
“That’s the serious problem,” said Monreal, who added that because crews were able to turn off the reactor, the situation could have been much worse.
He said that with Chernobyl, the reactor was still fissioning during the explosions and smoke. There was no containment vessel around the reactor itself.
Unlike Chernobyl, the areas surrounding Fukushima have been evacuated, and people are being told to stay in their homes to avoid the radioactive soot that could result from the fires. Monreal said that with Chernobyl, residents of the town weren’t evacuated until five days after the explosion. Even after, radioactive material was exposed to more of the population when people kept drinking milk from cows that had ingested contaminated grass.
Monreal called the events of Chernobyl “an absolutely avoidable tragedy.”
The plants at Fukushima withstood the earthquakes, but because there was no electrical power to operate the coolers, an explosion occurred. Pools of spent fuel have become a problem and have been catching on fire. The area was so damaged that fire trucks couldn’t get into the area until recently, according to Theo Theofanous, a professor of nuclear engineering. He added that the plants do have power again — another plus.
During the question-and-answer session, someone asked why robots couldn’t be sent in to help clear some of the debris blocking efforts in the plant. Monreal said that the radioactivity makes it impossible for electronics to function, and that suits for workers would have to contain lead 3 inches thick to fully protect workers.
Some reflections about the future of nuclear power also were borne out of the questions. When considering the status quo of coal-based energy and its effects on the environment or nuclear power, Monreal was thoughtful.
“The question becomes, is (nuclear energy) worse than the alternative?” he posed to the audience.
Theofanous was more definitive.
“I think the whole thing needs to be rethought,” he said. “I think we have major problems in our institutions.”
As nuclear power has become politically charged and the infrastructure lacking, Theofanous was dubious about its future in America.
“I have great doubts,” he said. “It’s not a good story.”
Wednesday’s lecture was recorded and will be available on the institute’s Web site this week. Click here for Monreal’s slide show.