Back in April, I expressed concern about levels of radioactive caesuim-137 that were released during the Fukushima disaster following the earthquake and tsunami that hit Japan’s east coast in March of this year. Caesium-137 has a half life of thirty years, meaning that it takes thirty years to become half as radioactive.
Now, research published in the Proceedings of the National Academy of Sciences has found caesium-137 in the soil in areas around Fukushima at levels that are higher than the maximum permitted by the Japanese government for the growing of rice. The two research projects used different methods to obtain their results. In one, computer modelling was used to estimate how much caesium would have found its way into the soil across a wide area of Japan, taking into account wind speed and direction, rainfall etc. in the days following the disaster. In the other, a team took soil samples from 108 locations around Fukushima, though they were not allowed within the 20km exclusion zone that is still in force around the damaged power plant.
Radioactivity levels of up to 5,000 becquerels per kilogram (Bq/kg) of soil are allowed by the Japanese government for the growing of rice. Close to the plant itself, the researchers estimate that levels of radioactive caesium-137 were at around eight times this limit (though they weren’t allowed into the 20km exclusion zone to confirm this).
In addition the research found that “The east Fukushima prefecture exceeded [the 5,000 Bq/ kg limit] and some neighbouring prefectures such as Miyagi, Tochigi and Ibaraki are partially close to the limit under our upper-bound estimate”.
Much of the research is based on estimates and more work will need to be done to get a true picture of how far the caesium-137 has travelled and at what levels of concentration. It’s clear that the people living around the Fukushima plant are going to need answers as to whether it’s safe or not to carry on living there long-term.
Once bound into soil, caesium-137′s uptake by plants is restricted, which might make it less of a problem more quickly, but it does seem that some of the land around Fukushima will be unusable for farming for decades to come.
In a bid to cut global CO2 emissions, it looks like there will be many more nuclear power plants built around the world in the coming years, including here in the UK. We can’t afford to have disasters like the one at Fukushima repeated anywhere, so safety is going to have to be the top priority across the world.
And as I keep saying, we have to invest more in renewable energy. Small scale, local energy generation using renewable energy sources is what we need to aim for.