Category Archives: Fukushima

IAEA Affirms Japan’s Fukushima-Related Radioactivity Monitoring

by Tim Hornyak
11 October 2017
Originally published by Eos, a periodical of the American Geophysical Union

Laboratories outside Japan have validated the results. Marine radioactivity levels from the nuclear disaster have fallen, but questions remain years after the meltdown. Continue reading IAEA Affirms Japan’s Fukushima-Related Radioactivity Monitoring

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Scientists Find New Source of Radioactivity from Fukushima Disaster

by WHOI Media Relations
Published 2 October 2017

Scientists have found a previously unsuspected place where radioactive material from the Fukushima Dai-ichi nuclear power plant disaster has accumulated—in sands and brackish groundwater beneath beaches up to 60 miles away. The sands took up and retained radioactive cesium originating from the disaster in 2011 and have been slowly releasing it back to the ocean.

“No one is either exposed to, or drinks, these waters, and thus public health is not of primary concern here,” the scientists said in a study published October 2 in the Proceedings of the National Academy of Sciences. But “this new and unanticipated pathway for the storage and release of radionuclides to the ocean should be taken into account in the management of coastal areas where nuclear power plants are situated.”

The research team—Virginie Sanial, Ken Buesseler, and Matthew Charette of Woods Hole Oceanographic Institution and Seiya Nagao of Kanazawa University—hypothesize that high levels of radioactive cesium-137 released in 2011 were transported along the coast by ocean currents. Days and weeks after the accident, waves and tides brought the cesium in these highly contaminated waters onto the coast, where cesium became “stuck” to the surfaces of sand grains. Cesium-enriched sand resided on the beaches and in the brackish, slightly salty mixture of fresh water and salt water beneath the beaches.

WHOI Oct17 FukushimaCsFigure1280_472593
The new study revealed a previously unsuspected pathway for radioactive material to be transported, stored for years, and subsequently released far from the site where it was initially discharged.
Illustration by Natalie Renier, Woods Hole Oceanographic Institution

But in salt water, cesium no longer “sticks” to the sand. So when more recent waves and tides brought in salty seawater from the ocean, the brackish water underneath the beaches became salty enough to release the cesium from the sand, and it was carried back into the ocean.

“No one expected that the highest levels of cesium in ocean water today would be found not in the harbor of the Fukushima Dai-ichi nuclear power plant, but in the groundwater many miles away below the beach sands,” said Sanial.

The scientists estimated that the amount of contaminated water flowing into the ocean from this brackish groundwater source below the sandy beaches is as large as the input from two other known sources: ongoing releases and runoff from the nuclear power plant site itself, and outflow from rivers that continue to carry cesium from the fallout on land in 2011 to the ocean on river-borne particles. All three of these ongoing sources are thousands of times smaller today compared with the days immediately after the disaster in 2011.

The team sampled eight beaches within 60 miles of the crippled Fukushima Dai-ichi Nuclear Power Plant between 2013 and 2016. They plunged 3- to 7-foot-long tubes into the sand, pumped up underlying groundwater, and analyzed its cesium-137 content. The cesium levels in the groundwater were up to 10 times higher than the levels found in seawater within the harbor of the nuclear power plant itself. In addition, the total amount of cesium retained more than 3 feet deep in the sands is higher than what is found in sediments on the seafloor offshore of the beaches.

Cesium has a long half-life and persists in the environment. In their analyses of the beaches, the scientists detected not only cesium-137, which may have come from the Dai-ichi plant or from nuclear weapons tested in the 1950s and1960s, but also cesium-134, a radioactive form of cesium that can only come only from the 2011 Fukushima accident.

The researchers also conducted experiments on Japanese beach samples in the lab to demonstrate that cesium did indeed “stick” to sand grains and then lost their “stickiness” when they were flushed with salt water.

“It is as if the sands acted as a ‘sponge’ that was contaminated in 2011 and is only slowly being depleted,” said Buesseler.

“Only time will slowly remove the cesium from the sands as it naturally decays away and is washed out by seawater,” said Sanial.

“There are 440 operational nuclear reactors in the world, with approximately one-half situated along the coastline,” the study’s authors wrote. So this previously unknown, ongoing, and persistent source of contamination to coastal oceans “needs to be considered in nuclear power plant monitoring and scenarios involving future accidents.”

Possible Melted Fuel Seen for First Time at Fukushima Plant

by Mari Yamaguchi
July 21, 2017
Originally published by the Associated Press

TOKYO (AP) — An underwater robot captured images of solidified lava-like rocks Friday inside a damaged reactor at Japan’s crippled Fukushima nuclear plant, spotting for the first time what is believed to be nuclear fuel that melted six years ago. Continue reading Possible Melted Fuel Seen for First Time at Fukushima Plant

Swimming robot probes Fukushima reactor to find melted fuel

by Mari Yamaguchi
July 19, 2017
Originally published by the Associated Press

TOKYO (AP) — An underwater robot entered a badly damaged reactor at Japan’s crippled Fukushima nuclear plant Wednesday, capturing images of the harsh impact of its meltdown, including key structures that were torn and knocked out of place. Continue reading Swimming robot probes Fukushima reactor to find melted fuel

The fate of atmospheric Fukushima radiation

Did you enjoy your trip? If you were alive during the Fukushima meltdown in 2011, you received an extra dose of radiation equal to that received on a roundtrip flight from Vancouver to Tokyo. This is the result according to research presented by Nikolaos Evangeliou of the Norwegian Institute for Air Research at the annual meeting of the European Geophysical Union earlier this year.

Continue reading The fate of atmospheric Fukushima radiation