Nuclear radiation health experts from Oregon State University say the debris from the March 2011 earthquake and tsunami in Japan that may begin to wash up on U.S. shores this year will not pose a radiation risk.
The researchers who have looked at the issue of the meltdown of the Fukushima Dai-ichi nuclear plant say the minor amounts of deposition on the debris field scattered in the ocean will have long since dissipated, decayed or been washed away by months of pounding in ocean waves.
However, that’s not to say that all of the debris that reaches Pacific Coast shores in the United States and Canada will be harmless.
“The tsunami impacted several industrial areas and no doubt swept out to sea many things like bottled chemicals or other compounds that could be toxic,” said Kathryn Higley, professor and head of the Department of Nuclear Engineering and Radiation Health Physics at OSU.
“If you see something on the beach that looks like it may have come from this accident, you shouldn’t assume that it’s safe,” Higley said. “People should treat these debris with common sense; there could be some things mixed in there that are dangerous. But it will have nothing to do with radioactive contamination.”
Higley and other OSU experts have been active in studying the Fukushima accident since it occurred, and are now doing research to help scientists in Japan better understand such issues as uptake of radioactive contamination by plants growing near the site of the accident. They also studied marine and fishery impacts near Japan soon after the incident.
“In the city and fields near Fukushima, there are still areas with substantial contamination, and it may be a few years before all of this is dealt with,” Higley said. “But researchers from all over the world are contributing information on innovative ways to help this area recover, including some lessons learned from the much more serious Chernobyl accident in 1986 in the Ukraine.”
Some of the technology to deal with this is complex. Other approaches, she said, can be fairly low-tech – removal of leaf litter, washing, plowing the ground, collecting and concentrating water runoff.
The repercussions of the event in the ocean, however, and implications for distant shores are much more subdued. Most of the discharge that was of concern was radionuclides of iodine and cesium, which were deposited on widely dispersed, floating marine debris days after the tsunami. Most of the iodine by now will have disappeared due to radioactive decay, and the cesium washed off and diluted in the ocean.
“There are a lot of misconceptions about radioactivity,” Higley said. “Many people believe that if it can be measured, it’s harmful. But we live in a world of radiation coming to us from the sun, or naturally present in the earth, or even from our own bodies.
“There are higher natural levels of radiation found all around the Rocky Mountains, for instance,” she said. “And we can still measure radioactive contaminants in nature from old atmospheric nuclear weapons tests more than 50 years ago.”
Like most of those other forms of radiation, Higley said, any measurable radioactivity found on debris from Fukushima should be at very low levels and of no health concern – much less, for instance, than a person might receive in a single X-ray.
Debris from Japan should start to arrive in the United States and Canada late this year or in 2013 following normal ocean currents, say other OSU experts who are studying this issue. When they do, some aspects of them might be dangerous – a half-filled, floating, sealed bottle of a toxic chemical, for instance.
Meanwhile, an expedition based in Hawaii was launched to track the drift of tsunami debris is using remote sensing to compare the actual event to computer predictions of the trajectory while improving officials ability to warn residents about impending landfall.
The tsunami that followed on the heels of the March 11, 2011, earthquake in northern Japan produced as much as 25 million tons of debris. Much of the debris was swept into the ocean.
What stayed afloat drifted apart under the influence of winds and currents, most of it traveling eastward.
The debris’ composition and how much is still floating on the surface are largely unknown.
One thing is certain, University of Hawaii researchers say: the debris is hazardous to navigation, marine life and, when washed ashore, to coastlines.
To track where this debris is headed and provide appropriate warnings, a team of scientists and conservationists from the University of Hawaii’s Manoa and Hilo campuses, Scripps Institution of Oceanography and the Ocean Recovery Alliance quickly created a plan to survey the debris field and mark it with satellite-tracked drifting buoys.
The team launched an expedition at the end of November 2011 from Honolulu to Midway Atoll and beyond.
Armed with equipment shipped from California by Horizon Lines, navigational software provided by Nobeltec, a computer model of probable trajectories and observations of actual debris by Russian training ship crew, the team surveyed the probable pathways of tsunami debris moving toward the Northwest Hawaiian Islands.
The expedition deployed 11 drifting buoys, designed to simulate the motion of different types of debris, in a line between Midway and the leading edge of the tsunami debris field. Data from these satellite-tracked drifters, used in conjunction with computer models, allow remote monitoring of the movement of the debris field, giving scientists and operational agencies a better awareness of the status of the debris field and of the region’s current system.
Four hundred numbered wooden blocks were also deployed along the route, often near floating objects. Boaters, fishermen and beach-goers who find the blocks and contact the scientists as instructed on the blocks will help increase understanding of the motion of debris and currents in this remote region.
Among the most important results of the expedition to date is the recognition that tsunami debris has recently not advanced towards Midway, but instead has been flowing eastward well to the north of the atolls. Analysis of the ocean-current field shows why. In recent weeks, the general flow around all Hawaiian Islands has been from the southwest, producing a front located 300–400 miles northwest of the Midway. This front and associated northeastward jet keeps the tsunami debris north of the islands…at least for the time being.
Although this flow has prevented tsunami debris from approaching the islands, it carries a lot of “ordinary” debris (mainly old plastic) from the oceanic garbage patch located between Hawaii and California. The expedition documented 175 such objects, many photographed and collected for more thorough laboratory examination.
The sightings of non-tsunami debris match reports at Kure and Midway Islands of items washing up on the southern beaches of the atolls. Some of the items could be tracked to the main Hawaiian Islands. Systematic examination of the samples (including water samples) has not revealed any significant radiation.
To see the projected drift of tsunami debris based on computer model of surface currents go to http://www.hawaii.edu/news/2012/02/08/tsunami-debris-expedition/