High levels of radioactive cesium pooling at dams near Fukushima nuke plant

Once radionuclides enter the eco-system, they move around carried by wind and water. They can’t “go away.” They can’t be “decontaminated.” They can only be moved, the biggest force moving them is nature, not clean up crews.

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.

High levels of radioactive cesium pooling at dams near Fukushima nuke plant

High concentrations of radioactive cesium have been accumulating at the bottom of 10 major dams within a 50-kilometer radius from the disaster-stricken Fukushima No. 1 Nuclear Power Plant, a survey by the Environment Ministry has found.

Radioactive cesium emanating from the 2011 nuclear disaster is pooling at those dams, which are used to hold drinking water and for agricultural use, after the substances flew into there from mountains, forests and rivers. The radiation levels at the bottom of those dams top those set for designated waste at over 8,000 becquerels per kilogram.

While the Environment Ministry plans to monitor the situation without decontaminating the dams on the grounds that radiation levels in dam water is not high enough to affect human health, experts are calling for the ministry to look into measures to counter any future risks.

The ministry began a monitoring survey on those dams and rivers downstream in September 2011 to grasp the moves of radioactive substances flowing into them from mountains and forests that are not subject to decontamination work. The survey samples water at 73 dams in Tokyo, Iwate and seven other prefectures about once every several months.

Among them, there were 10 dams in Fukushima Prefecture where the average concentration of cesium in the surface layer of bottom soil measured between fiscal 2011 and 2015 topped the regulated levels for designated waste. Those dams include Ganbe Dam in the village of Iitate with 64,439 becquerels per kilogram of cesium, Yokokawa Dam in the city of Minamisoma with 27,533 becquerels, and Mano Dam in Iitate with 26,859 becquerels.

Meanwhile, the surface water at those 10 dams contained 1-2 becquerels per liter of cesium, which is below the drinking water criteria at 10 becquerels.

While the total amount of cesium deposited at the bottom of those dams is unknown from the environment ministry’s survey, a separate study conducted at Ogaki Dam in the town of Namie by the Ministry of Agriculture, Forestry and Fisheries’ Tohoku Regional Agricultural Administration Office estimated in December 2013 that there was a combined 8 trillion becquerels of cesium 134 and cesium 137 at the dam. The figure came about after estimating the amount of accumulated cesium every 10-meter-square area based on cesium levels in sedimentary soil sampled at 110 locations at the bottom of the dam, which is for agricultural use.

The National Institute for Environmental Studies in Tsukuba, Ibaraki Prefecture, will shortly begin a full-scale survey on cesium concentrations at several dams.

“At the moment, it is best to contain cesium at those dams. If we dredge it, the substance could curl up and could contaminate rivers downstream,” said an Environment Ministry official.

http://mainichi.jp/english/articles/20160926/p2a/00m/0na/007000c

Anxiety soars as cesium builds up in Fukushima dams

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, the levels of radioactive cesium detected in the dams’ waters, at 1 to 2 becquerels per liter, are 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.”

http://mainichi.jp/english/articles/20160926/p2a/00m/0na/011000c

September 26, 2016 Posted by dunrenard | Fukushima 2016 | Fukushima continuing, radiation, Radionuclides, water | Leave a comment