Nuclear news from Japan

Worth noting is a news story in this week’s edition of Nature which looks at radioactive contamination of the local environment following a series of equipment failures, partial nuclear fuel meltdowns and reactor explosions which occurred earlier this year at the Fukushima Daiichi power plant. The nuclear emergency was a result of the Tōhoku earthquake and tsunami, which led to the deaths of tens of thousands, and laid waste to many towns and villages in the area.

Nature’s Tokyo correspondent David Cyranoski reports on a study led by Tokyo University plant physiologist Tomoko Nakanishi, who next month will publish his team’s findings in the Japanese journal Radioisotopes.

Looking at the impact of the Fukushima radiation release on plants, animals, fisheries and forests, Nakanishi and his colleagues found only low levels of radioactivity in crops harvested during May, and that the contamination is of a type which can be washed off. The radioactive particles had settled on the plant leaves, and were not absorbed through the soil in significant amounts. As for the amount of radiation involved, around nine becquerels per kilogramme of wet plant mass were detected, which is less than one-fiftieth of the accepted safety limit for human consumption.

In practical terms, what this means is that the current harvest will have to be discarded, but the soil will be safe for replanting once a thin surface layer is removed. That will be a costly task, but it is a long way from the worst-case scenario painted by many following the disaster.

On a less positive note, a separate study from a group led by Tomoya Yamauchi at Kobe University found a number of radiation hotspots in Fukushima city, some 60 kilometres from the power plant, where radiation levels of up to 47,000 becquerels per kilogramme were measured. These sites should be evacuated immediately, as the radiation there greatly exceeds the 10,000 becquerel exposure limit set by the Japanese government.