Six years ago, the northeastern region of Japan was forever changed when it was struck by the Higashi-Nihon earthquake, otherwise known as the Great East Japan earthquake. A major tsunami ensued, triggering the meltdown of three reactors at the Fukushima Daiichi Nuclear Power Plant, which resulted in the release of radioactive materials.
It was one of the worst nuclear disasters in history.
In the days that followed, an evacuation order was issued for people living near the plant, resulting in tens of thousands of people fleeing their homes.
Radioactive materials – especially radio-cesium – began migrating to agricultural fields, forests, fish and animals from soil and water. Rivers, irrigation water, paddy water, lakes, groundwater and reservoirs were all affected.
Shortly after the meltdown, Hiroaki and his 3M Japan team began visiting research institutes and universities who were studying the effects of radioactive leakage in the environment. The team was hoping to gain a better understanding of radio-cesium concentration and the dynamics of its migration into the environment.
They quickly began working on developing a more efficient and simplified method to measure leaked radioactive materials.
Photo: Seiichi Ota, 3M Purification specialist, prepares to capture water samples from a radio-contaminated rice field.
At the time of the disaster, the traditional method used for measuring radio-cesium levels in water was to pour the water into a two-liter plastic container and put it in a radio-cesium detector. However, as research in the affected areas progressed, scientists found that plants were absorbing the dissolved radio-cesium that was in the water. It made it difficult to effectively measure concentration levels.
They now had to separate and condense the radio-cesium into both dissolved and turbid – or suspended solid – components and measure both, which took even more time.
“Radio-cesium dissolved in water would need to be heated for many hours – and even up to a few days – until it completely evaporated,” Hiroaki explains, “leaving only the radio-cesium to be measured.”
Knowing that time was of the essence, the 3M Japan team used the 3M Empore RAD Disk technology to develop a unique method that would allow scientists and researchers to separate and condense both components simultaneously.
The 3M Empore RAD Disk is thin and only 47 millimeters in diameter. It is composed of very small sorbent particles that are held together within a matrix of polytetrafluoroethylene, or PTFE. The disks act as a filtration and separation system, selectively separating and retaining dissolved substances to be analyzed.
To help researchers in the field measure radio-cesium levels in a more rapid and simplified way, Hiroaki and his team developed a special “RAD Disk Pack,” which consists of three pre-filters and the 3M Empore RAD Disk-Cesium. The team also created pressure filtration equipment called the “RAD Disk Sampler,” which helped speed up processing time.
When the two systems are used together, researchers are able to separate and condense radio-cesium in water into dissolved and turbid components more easily. This allows them to measure overall radio-cesium levels faster than the traditional separation method.
“It is known that the dissolved radio-cesium in irrigation water increases the radio-cesium concentration in rice plants,” says Hirofumi Tsukada, professor, Fukushima University. “Radio-cesium dissolved in irrigation water is efficiently condensed using the system by 3M.”
Japan’s National Institute of Advanced Industrial Science and Technology has endorsed the 3M Empore RAD Disks-Cesium as an accurate method to measure radio-cesium levels in the environment.
“By measuring a very small concentration of radio-cesium in water, we can investigate its effects on crops and capture the distribution of radio-cesium in the environment,” says Hiroaki, who has been named a committee member under the National Institute. “This helps us predict its effect on foods and human health, and then take preventive measures."
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