Radioactively-hot particles detected in dusts and soils from Northern Japan by combination of gamma spectrometry, autoradiography, and SEM/EDS analysis — Marco Kaltofen, Arnie Gundersen, ScienceDirect

“Abstract

After the March 11, 2011, nuclear reactor meltdowns at Fukushima Dai-ichi, 180 samples of Japanese particulate matter (dusts and surface soils) and 235 similar U.S. and Canadian samples were collected and analyzed sequentially by gamma spectrometry, autoradiography, and scanning electron microscopy with energy dispersive X-ray analysis. Samples were collected and analyzed over a five-year period, from 2011 to 2016. Detectable levels of 134Cs and 137Cs were found in 142 of 180 (80%) Japanese particulate matter samples. The median radio-cesium specific activity of Japanese particulate samples was 3.2 kBq kg− 1 ± 1.8 kBq kg− 1, and the mean was 25.7 kBq kg− 1(σ = 72 kBq kg− 1). The U.S. and Canadian mean and median radio‑cesium activity levels were < 0.03 kBq kg− 1. U.S. and Canadian samples had detectable 134Cs and 137Cs in one dust sample out of 32 collected, and four soils out of 74. The maximum US/Canada radio-cesium particulate matter activity was 0.30 ± 0.10 kBq kg− 1. The mean in Japan was skewed upward due to nine of the 180 (5%) samples with activities > 250 kBq kg− 1. This skewness was present in both the 2011 and 2016 sample sets.

300 individual radioactively-hot particles were identified in samples from Japan; composed of 1% or more of the elements cesium, americium, radium, polonium, thorium, tellurium, or strontium. Some particles reached specific activities in the MBq μg− 1 level and higher. No cesium-containing hot particles were found in the U.S. sample set. Only naturally-occurring radionuclides were found in particles from the U.S. background samples. Some of the hot particles detected in this study could cause significant radiation exposures to individuals if inhaled. Exposure models ignoring these isolated hot particles would potentially understate human radiation dose. ”

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Greenpeace reports jump in radioactive contamination in Fukushima waterways — The Japan Times

” Greenpeace Japan on Thursday said it has discovered radioactive contamination in Fukushima’s riverbanks, estuaries and coastal waters at a scale hundreds of times higher than pre-2011 levels.

One sample of sediment taken along the Niida River, less than 30 km northwest of the crippled Fukushima No. 1 power plant, revealed the presence of cesium-134 and cesium-137 at levels of 29,800 becquerels per kilogram.

That was just one of 19 samples of dried sediment and soil the environmental activist group took and analyzed from the banks of the Abukuma, Niida, and Ota rivers. The samples were collected by Greenpeace in February and March.

All of the samples but one exhibited more than 1,000 Bq/kg of radioactive material. The lowest level, 309 Bq/kg, was logged at a spot along the Abukuma River.

Cesium-134 has a half-life of about two years, but cesium-137 has a half-life of 30 years and is considered particularly hazardous. The standard limits set for radioactive cesium in Japan are 100 Bq/kg for general foods and 10 Bq/kg for drinking water.

“The radiological impacts of the Fukushima nuclear disaster on the marine environment, with consequences for both human and nonhuman health, are not only the first years. They are both ongoing and future threats, principally the continued releases from the Fukushima No. 1 plant itself and translocation of land-based contamination throughout Fukushima Prefecture, including upland forests, rivers, lakes and coastal estuaries,” the report said.

Greenpeace Japan also published the results of tests on dried marine sediment samples collected at 25 points off the Fukushima coastal area, including three river estuaries, during this same period, at depths of between 7.4 and 30.6 meters. The results showed that the highest level of cesium was 144 Bq/kg taken from a sample collected off the coast from the Fukushima power plant, while the lowest total cesium figure was 6.5 Bq/kg off Nakanosaku, well to the south of the plant.

In addition to Fukushima, Greenpeace Japan took dried sediment samples from Lake Biwa at three locations near the shore. The results showed cesium levels to be between 7.1 Bq/kg and 13 Bq/kg at two locations, and negligible at the other two.

The safety of Lake Biwa, which provides drinking water for about 14 million people in the Kansai region, has become a major bone of contention between Kansai Electric Power Co., which wants to restart reactors in neighboring Fukui Prefecture, and residents in and around Lake Biwa who are fighting to keep them shut down. ”

by Eric Johnston

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30 groups show radioactive soil levels to address Fukushima fears — The Asahi Shimbun

” A coalition of 30 private groups is digging deeper into radiation contamination from the 2011 Fukushima nuclear disaster to address persistent concerns from the public around Japan.

The coalition’s website, titled the East Japan Soil Measurement Project, shows radiation levels in soil samples taken from more than 1,900 sites in Tokyo and 16 prefectures, from northeastern Japan to the Pacific side of the central Japan.

The project was started partly because parents were concerned that local governments were using only airborne radiation levels to determine if outdoor areas were safe for children.

While radioactive contamination in the air decreases as time passes, that is not necessarily the case with radioactive substances in the ground.

The group’s survey of land contamination has found “hot spots,” where levels are significantly higher than in the surrounding neighborhoods, five years after the disaster unfolded at the Fukushima No. 1 nuclear plant.

The radiation levels in some of those areas are comparable to those at nuclear reactor buildings and medical institutions that provide radiation therapy, where public access is restricted because annual radiation doses can exceed 5 millisieverts.

Three citizens groups, including the nonprofit organization Fukushima 30-Year Project, created the website after forming an extensive network of private entities in October last year.

The groups conduct the measurements in a unified manner. About 1,000 cubic centimeters of soil samples are taken by digging 5 cm deep in the ground in the shape of a 10-cm-by-20-cm block in residential areas and districts that ordinary citizens are allowed to enter.

Extreme anomalies in the radiation measurements are not posted on the site because the purpose of the project is to show average contamination in local communities.

“We want to prevent viewers from misunderstanding the pollution level of a given community just because of isolated cases of high numbers,” said Hidetake Ishimaru, head of the coalition’s secretariat. “Viewers can get tips on how to avoid risks in daily life by comparing figures that were measured in a standardized manner.”

The highest reading so far was 135,000 becquerels of radioactive cesium detected in a forest near a home in the Hiso district of Iitate village, northwest of the embattled Fukushima No. 1 nuclear power plant.

The soil sample showed 111,028 becquerels of cesium-137 and 23,920 becquerels of cesium-134.

Radioactivity readings at many observation spots in Shizuoka Prefecture, which is far from the nuclear plant, were below the lowest detectable level.

But the survey this year still found sites in the Kanto region, south of the Tohoku region where the Fukushima plant is located, with readings exceeding 10,000 becquerels.

Save Child Iwate, a group in Iwate Prefecture, was the first of the 30 collaborating private organizations to take measurements in the soil.

Save Child Iwate started measuring radiation doses in the atmosphere and radioactivity in the soil throughout the prefecture in spring 2012. Many of the sites were at schools and parks. It has measured doses at 316 spots and publicized the results.

Kazuhiro Sugawara, a 39-year-old staff member of Save Child Iwate’s secretariat, said the group began measuring radioactivity in soil after local governments had insisted that it was safe to let children play outdoors.

Local officials cited low radiation doses in the air in their safety assurances.

But the group remained skeptical because the evacuation order for residents from the 1986 Chernobyl nuclear disaster was issued in part based on the extent of ground contamination.

Sugawara’s daughter was 10 years old and attending an elementary school in Iwate Prefecture when the disaster started at the Fukushima nuclear plant. Like other parents in the area, Sugawara was most concerned about the safety of the children.

“We cannot feel safe without data on soil contamination because children play with earth, wipe the mouths with their dirty hands and inhale dirt blown up by wind, exposing themselves to the risk of internal radiation exposure,” Sugawara said about why he undertook the project. “If local officials would not bother to measure soil contamination, we decided to do so on our own.”

The highest land contamination figure Save Child Iwate recorded came from samples from private property in Kanegasaki in the prefecture in June 2012.

At that spot, the radiation level in the air was 0.24 microsieverts per hour, while radioactivity in the soil sample exceeded 4,500 becquerels.

The coalition accepts sample soils sent by concerned citizens for free measurements using funds provided by businesses and donations from the public.

It currently lacks sufficient data from Niigata, Tochigi and Gunma prefectures.

“Part of the reason we cannot enlist cooperation from groups in the three prefectures, where agriculture is thriving, is that they fear possible negative publicity,” Ishimaru said.

The coalition plans to hold workshops for citizens around the nation on how to gather samples to broaden support for the endeavor.

Tetsuji Imanaka, a researcher with Kyoto University’s Research Reactor Institute who has been monitoring land contamination in Fukushima Prefecture and elsewhere, stressed the importance of gaining data from soil.

“Since numbers on land contamination are basic data needed to study the scope of pollution in a given region, detailed surveys are necessary,” he said. “Ideally, local officials should do the task. I am hoping that the coalition will play a significant role.” ”

by Masakazu Honda

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