Yasuo Onishi has been a scientist in demand since the Fukushima nuclear disaster one year ago today, offering advice in a role that gives him a firsthand look at environmental cleanup in Japan.
Cleanup of the Fukushima power plant complex could take 30 or 40 years, after a magnitude-9 earthquake was followed by a tsunami with a 50-foot-high wave that caused a full meltdown at three reactors.
But there is a more immediate need to clean up land outside the power plant complex. Many of the more than 80,000 people evacuated want to return to their homes and businesses, and people who continue to live in areas with lower radioactive contamination want to rid their communities of threats.
Onishi, a chief scientist with Pacific Northwest National Laboratory in Richland, is sharing his expertise in decontamination, some of it gained as the U.S. government environmental coordinator for water and soil after the Chernobyl disaster.
In some cases, the people of Japan are not waiting for the government to act. Locals are taking over environmental cleanup, wielding radiation detectors and cleaning up their own property and community property.
"The Japanese are very eager to make the environment clean," he said. "If they can do it themselves, they will."
Onishi, who grew up in Japan, was sent to Japan shortly after the Fukushima disaster last year when the Japanese prime minister requested help.
Other PNNL scientists and engineers worked on a crisis response team last spring in Washington, D.C., or remained at the Department of Energy lab to support the team with technical analyses.
Since his first trip to Japan after the disaster, Onishi has spent months at a time there. He now is the project manager on a PNNL contract with the Japanese government to offer advice they request on a broad range of topics based on the expertise of the Department of Energy's national laboratories.
In the days following the disaster, the questions he received were on topics related to the power plant complex, such as how to transfer contaminated water from one area to another and how to treat contaminated water.
Hose-in-hose lines such as those used at Hanford to catch any leak from the inner line now are being used in Japan's cleanup efforts, he said.
Japan also has used a method that relies on zeolite to remove radioactive cesium in water, similar to a method used at Hanford to clean contaminated water in the cooling basins attached to the K reactors.
"Now the emphasis has shifted to outside of the plant," Onishi said.
Contamination spread in a plume 30 miles inland across a largely rural area that is 70 percent forest, he said.
Some of the contamination was from iodine 131, which no longer is a concern, because half of its radioactivity decays away every eight days. There also was cesium 134, with a half life of about two years, and the more worrisome cesium 137, with a half life of about 30 years.
Fortunately, the cesium has bound tightly with the clay soils in the area, Onishi said.
Even after the rainy season, almost all of the contamination has remained in the top 2 inches of the soil rather than being spread deeper by water.
For areas such as school yards, the solution has been to "flip it," he said. The top few inches of soil are scraped off and set aside. Then the clean soil beneath it is dug up so the contaminated soil can be spread in a layer and buried beneath it.
If communities have contamination above 20 millisieverts per year of radiation on direct exposure, such as in soil and on trees and houses, the Japanese government will bring in a contractor. Those areas have been evacuated. Thirteen demonstration sites have cleanup under way, with more wide scale cleanup planned for those areas to start next month.
For lower amounts of contamination, local governments are doing cleanup themselves and billing the central government.
The goal is to reduce contamination levels to 1 millisievert a year on direct exposure, which is about half as much as the average background radiation exposure a person would receive in everyday activities.
Weeds and ground cover are being mowed to remove vegetation that may be contaminated and fallen leaves are being collected. Low hanging tree branches are being cut off and moss removed.
Onishi has been working with officials on how to clean roofs and outer walls of buildings using high-pressure water jets. The soil where the contaminated water lands can then be removed. He also has suggesting ways to pressure wash or sandblast roads.
Homeowners are using the same techniques on their property, washing their homes with high-pressure water sprays and mowing vegetation.
One day he advised as community members cleaned the contaminated water in a Fukushima City swimming pool, putting zeolite in the water to sop up cesium.
The contamination in the forests presents a more difficult problem, particularly because much of the land is steep.
One suggestion has been to put in settling ponds to collect water in the streams that run off the hillsides, Onishi said.
Many other cleanup issues remain. Onishi's photographs show tall piles of bagged contaminated waste piled along roadways as communities store the waste until there is a way to dispose of it. Soil at farms where rice is grown also must be restored before the land is taken over by trees and other vegetation.
But not all of Onishi's advice has been technical. He has seen the advantages at Hanford and elsewhere in getting the public involved in discussions of environmental cleanup issues. Knowledge can help reduce fear, he said.
"We recommend bringing in local people as early as possible," he said. "It seems like it takes longer, but in the end it is faster."
-- Annette Cary: 582-1533; firstname.lastname@example.org; more Hanford news at hanfordnews.com