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Continuous leaking of radioactive strontium and cesium from Fukushima to the ocean

By BS MediaTwitter Profile | Published: Wednesday, 09 March 2016
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Scientists from the Universitat Autònoma de Barcelona (UAB) investigated the levels of hot Sr and caesium in the coast off Japan in September 2013. hot levels in saltwater were 10 to 100 times higher than before the nuclear accident, particularly near the facility, suggesting that water containing Sr and caesium isotopes was still leaking into the Pacific Ocean.

March 11 will be the 5th day of remembrance since the nuclear accident in Fukushima, Japan. The Tohoku earthquake and the series of tsunamis damaged the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) causation a massive release of radiation into the atmosphere and the Pacific Ocean. Since then, the Tokyo Electric Power Company (TEPCO) and the Japanese government have focused on dominant the water flowing in and out of the FDNPP and on decontaminating the extremely hot water used as fluid for the damaged reactors (about 300 m3 a day, three-dimensional meter = 1000 L). This cooling water is then stored in tanks and, to some extent, being decontaminated.

A new study recently published in Environmental Science and Technology, uses information on the concentrations of 90Sr and 134,137Cs in the coast off Japan from the moment of the accident until September 2013, and puts it into a longer-time perspective including published information and TEPCO's observation information available until June 2015. This study continues the work initiated after the accident in 2011 by some of the authors. These and other partners from Belgium and Japan are presently involved in the European FRAME project lead by Dr. Pere masquerade that aims at perusal the impact of recent releases from the Fukushima nuclear accident on the marine environment. FRAME is encompassed inside the European extraterrestrial object project.

saltwater collected from the sea surface down to 500 m between 1 and 110 km off the FDNPP showed concentrations up to 9, 124 and 54 Bq·m-3 for 90Sr, 137Cs and 134Cs, severally . The highest concentrations, found inside 6 km off the FDNPP, were about 9, 100 and 50 times higher, severally , than pre-Fukushima levels. Before the accident, the main source of these radionuclides was atmospherical deposition due to nuclear bomb testing performed in the fifties and sixties. The presence of 134Cs (undetectable before the accident) and the distinct relationship between 90Sr and 137Cs in the samples recommended that FDNPP was leaking 90Sr at a rate of 2,3 - 8,5 GBq d-1 (giga-Becquerel per day) into the Pacific Ocean in September 2013. so much a leak would be 100-1000 times bigger than the amount of 90Sr transported by rivers from land to ocean. extra risk is related to the large amounts of water stored in tanks that have often leaked in the past. These results are in agreement with TEPCO's observation information which show levels of 90Sr and 137Cs up to 10 and 1000 times higher than pre-Fukushima near the discharge transmission of the FDNPP until June 2015 (most recent information enclosed in the study). The presence of 90Sr and 134,137Cs in significant amounts until 2015 suggests the need of a continuous observation of artificial radionuclides in the Pacific Ocean.

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