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Anxiety soars as cesium builds up in Fukushima dams

Ogaki Dam in Namie, Fukushima Prefecture, as seen from a Mainichi Shimbun helicopter in July 2016, contains high concentrations of radioactive cesium exceeding the limit set for designated waste. (Mainichi)

Dams surrounding the stricken Fukushima No. 1 Nuclear Power Plant operated by Tokyo Electric Power Co. (TEPCO) have become de facto storage facilities for high concentrations of radioactive cesium as the element continues to accumulate.

With no effective countermeasures in sight, the government insists that water from the dams is safe, but to local residents, the government's stance comes across as the shelving of a crucial problem.

"It's best to leave it as it is," an official from the Ministry of the Environment says, with the knowledge that in 10 dams in Fukushima Prefecture, there is soil containing concentrations of cesium over the limit set for designated waste -- or over 8,000 becquerels per kilogram.

According to monitoring procedures carried out by the ministry, no significant levels of radioactive cesium were detected in the dams' waters, meaning the levels were well below the maximum amount permitted in drinking water, which is 10 becquerels per liter. The air radiation doses in the dams' surrounding areas are at a maximum 2 microsieverts per hour, which the ministry says "does not immediately affect humans, if they avoid going near the dams." This information is the main basis behind the central government's wait-and-see stance. For the time being, the cesium appears to have attached itself to soil and is collected at the bottom of the dams, with the water above it blocking radiation from reaching and affecting the surrounding areas.

In a basic policy based on a special law, passed in August 2011, on measures for dealing with radioactive material following the onset of the Fukushima nuclear disaster, the Environment Ministry stipulates the decontamination of areas necessary from "the standpoint of protecting human health." The ministry argues that as long as high concentrations of cesium at the bottom of multiple dams in Fukushima Prefecture do not pose imminent danger to human health, there are no legal problems in the ministry refraining from taking action.

"If the dams dry up due to water shortages, we just have to keep people from getting close to them," the aforementioned ministry official says. "If we were to try to decontaminate the dams, how would we secure water sources while the work is in progress? The impact of trying to decontaminate the dams under the current state of affairs would be greater than not doing anything."

This stance taken by the central government has drawn protests from local residents.

"The Environment Ministry only says that it will monitor the dams' water and the surrounding areas. They say, 'We'll deal with anything that comes up,' but when asked what they plan to do if the dams break, they have no answers. It's painful to us that we can only give town residents the answers that the Environment Ministry gives us," says an official with the revitalization division of the Namie Municipal Government. The central government is set to lift evacuation orders for a part of the Fukushima Prefecture town of Namie in spring of 2017.

According to a Ministry of Agriculture, Forestry and Fisheries survey, Ogaki Dam, an agricultural dam in Namie, was estimated to have sediment totaling approximately 8 trillion becquerels of cesium as of December 2013. The agriculture ministry plans to re-survey the dam's accumulated cesium amounts and water safety before the water is used for agricultural purposes. Agricultural and fishery products from Fukushima Prefecture are tested to ensure that radioactive substances that they contain are below the maximum permissible amounts stipulated by law before they are shipped for distribution.

Still, one town official worries how revelations of high levels of radioactive material in local dams will affect consumers. "No matter how much they are told that the water is safe, will consumers buy agricultural products from Namie, knowing that there is cesium at the bottom of local dams?"

A 57-year-old vegetable farmer from Namie who has been evacuated to the Fukushima Prefecture city of Iwaki says, "The central government keeps on emphasizing that the dams are safe, but doesn't seem to be considering any fundamental solutions to the problem. If this state of affairs persists, we won't be able to return to Namie with peace of mind, nor will it be easy to resume farming."

Correction:

A previous version of this article incorrectly stated the levels of radioactive cesium in water in dams around the Fukushima No. 1 Nuclear Power Plant stood at one to two becquerels per liter. This has been corrected to state that no significant levels of radioactive cesium were detected in the dams' waters.

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