By Pat Sherman
Two weeks after the March 2011 Fukushima nuclear disaster, UC San Diego atmospheric chemists noticed an unprecedented increase in radioactive sulfur in La Jolla’s air, which they realized was coming from the damaged and leaking Japanese power plant.
However, Mark Thiemens, dean of physical sciences at UCSD, said recent reports of local kayak operators picking up radioactive residue from Fukushima on the bottoms of their boats are probably baseless — or at least not a result of the Fukushima disaster.
Even using one of the most sensitive instruments available, an accelerator mass spectrometer, would require a “gigantic water sample” to glean enough radioactivity to register, Thiemens said.
“The notion of guys going down with their Geiger counters (and detecting radiation), probably not,” Thiemens said. “I don’t see how it would happen unless there was another source … but it’s not likely coming from Japan.”
In 2011 Thiemens and a crew of UCSD atmospheric chemists reported the first quantitative measurement of the amount of radiation leaked from the damaged nuclear reactor in Fukushima, following the devastating earthquake and tsunami there.
Their estimate was based on radioactive sulfur that wafted across the Pacific Ocean after operators of the damaged reactor had to cool overheated fuel with seawater — causing a chemical reaction between byproducts of nuclear fission and chlorine ions in the saltwater.
Thiemens has, for the past several years, unsuccessfully sought to obtain grant funding to follow-up his research, first reported on Aug. 15 2011 in the online edition of the
Proceedings of the National Academy of Sciences.
However, he said neither the U.S. Nuclear Regulatory Commission, Environmental Protection Agency, California Air Resources Board or National Academy of Sciences (of which he is a member) were interested in funding additional research to measure the Fukushima fallout.
“It’s probably one of these things that just fell through the cracks,” Thiemens said. “It doesn’t quite fall under classical (research criteria).”
However, every few weeks for the past several years Thiemens’ crew has sent water samples collected off the La Jolla coast to Timothy Jull, a professor of geosciences and physics at the University of Arizona in Tucson.
Jull’s doctoral students are testing the samples for levels of iodine-129 (a naturally occurring, long-lived radioisotope of iodine which is useful in monitoring the effects of nuclear fission decay products).
“What we’ve seen so far is a slow increase directly after the Fukushima accident,” Jull said, noting that while Thiemens’ research showed radioactivity in the air took about five days to cross the Pacific Ocean, it takes about two to three years for water to cross the Pacific.
“Now we’re looking for a larger (reading), which should happen soon,” Jull said, noting that his students’ research is “all part of building a picture of the disposal of this material over time and how long it takes to get over here.
“We can then use that for modeling ocean circulation,” he said. “That would have some significance to future possible (nuclear) accidents and things like that.”
Jull said studies off the coast near Fukushima in 2011 testing for levels of iodine-129 and iodine-131 — produced when uranium or plutonium break down during the nuclear process — showed an increase of a factor of about 50.
Iodine-129 is being dumped into the Atlantic Ocean consistently by nuclear reprocessing plants in France and England, Jull said.
Asked if there is a danger of this material entering the ocean, Jull said, “I guess if we continue to dump large amounts of radioactivity into the ocean that’s not a good thing, but in the short term it’s not. People have know this for a long time and are sort of tracking it.”
Given the size of the Pacific Ocean Jull said radioactivity from Fukushima present in water reaching the West Coast of the United States is “dispersed and at a very low level.”
“In general, the public tends to overreact to radioactivity,” he said.
Yet, Thiemens believes it is important to continue monitoring radiation levels from Fukushima.
“I wouldn’t go so wholesale to say there’s nothing else coming,” he said. “Even if you’re 99 percent sure … the safest thing is just to measure.”