"In the immediate aftermath of the earthquake, our research team took on the vital task of detecting soil contamination to guide cleanup efforts."
The 2011 earthquake off the Pacific Coast of Japan was one of the five most powerful earthquakes in the world since modern record-keeping began in 1900. The earthquake triggered powerful tsunami waves that reached heights up to 133 feet (40.5 meters) and traveled up to 6 miles (10 km) inland. At the Fukushima Daiichi Nuclear Power Plant complex, tsunami waves washed over seawalls and destroyed diesel backup power systems, causing level 7 meltdowns at three reactors. The crisis has been ranked as the second worst nuclear accident ever, not as bad as the Chernobyl disaster, but worse than Three Mile Island. Over 200,000 residents in the area of the plant were evacuated. There was considerable controversy over government decisions to evacuate certain areas of the surrounding countryside but not others. Fukushima University felt an urgency to respond because national organizations that are primarily based in Tokyo had difficulty in reaching the affected areas.
The People Needed to Know
The project was based on the needs of local people and local governments who asked that contamination be measured in various objects including wood, household items, animals, etc. "It was very important for us to provide a good indication of where low-dose radiation areas were to assure local citizens of their safety," Yoshitaka Takagai, Associate Professor of Analytical Chemistry at Fukushima University said. "In the immediate aftermath of the earthquake, our research team took the initiative to build the first map of radioactive fallout in response to urgent local anxiety and demands for assurance, as well as taking on the additional vital task of detecting soil contamination to guide cleanup efforts." The Radioisotope Center of University of Tokyo also participated in the urgent task of determining the scope of contamination in the affected areas, as well as devising new methods for detecting radiation in soil, water, and food, to determine their safety and to guide development of decontamination methods.
Getting the Right Technology was Crucial
The environmental study of radiation was a new field to Takagai but being a licensed radiation engineer, he had a good idea of the instrument landscape. "We explained to PerkinElmer, what our needs were, what we wanted to do, and we asked for devices with the appropriate specs. If the company had not proactively contributed its instruments, we would have been delayed by the need to file grant applications with government funding agencies, a time consuming process which would have squandered the opportunity to Measure uranium and plutonium isotopes with short half-lives." PerkinElmer provided ELAN® DRC II inductively coupled plasma mass spectrometers (ICP-MS) which can detect individual uranium and plutonium isotopes. PerkinElmer also provided WIZARD2® gamma-ray counters and TriCarb® liquid scintillation counters for measuring radioactive strontium and tritium in water samples.
The Fukushima University researchers used the ICP-MS technology with a broad range of detection limits to test for metal contamination as well as the presence of uranium and plutonium in drinking water, soil, wastewater and food. Automatic gamma counter technology was used for 270 sample sequential measurements of gamma-ray nuclear species, such as radioactive cesium and iodine, to determine the scope of contamination in the affected areas. Automatic gamma counter technology was also used to devise new methods for detecting radiation in soil, water, and food, to determine their safety and to guide development of decontamination methods. Liquid scintillation counter technology was used for measurement of radioactive strontium and radioactive tritium, to locate contamination patterns and testing environmental water samples.
A survey of how radioactive uranium spreads was conducted from 7 to 80 km around the Fukushima Daiichi Nuclear Power Plant at 115 points in Fukushima prefecture. The values of the uranium isotope ratio for those soils were mostly similar to the naturally occurring levels although higher than normal concentrations of uranium were detected at several sampling points. The Fukushima University researchers determined that uranium and plutonium contamination was limited to the immediate vicinity of the reactors.
Mapping the Contamination
Mapping out the parts of Japan that were contaminated by radiation was a major concern in the weeks and months after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant Takagai and his research group, stepped in, without any official government mandate, to produce the first map of radioactive contamination shortly after the accident.
Since the tragedy, Takagai's team has continued to measure radiation before and after decontamination efforts to assess the efficacy of methods used to clean up radiation and provide an independent assessment to citizens of the region. "PerkinElmer technology was instrumental in speeding up the formerly labor-intensive radiation screening of large volumes of soil samples," Takagai said. "The sensitivity of the instruments also helped in developing protocols for removing topsoil to ensure effective decontamination of public areas such as school yards and playgrounds."