Radioactive waste from the Fukushima Daiichi nuclear power plant in Japan flowed into Tokyo Bay for five years after the 2011 disaster, according to a new study.

Hideo Yamazaki, a former professor of environmental analysis at Kindai University told The Asahi Shimbun that 20,100 becquerels of cesium per square meter were found in the mud of the Kyu-Edogawa river five years after a tsunami caused the meltdown of the plant. 

Cesium-137 is a dangerous fission product that is a radioactive isotope found in nuclear reactors and nuclear weapons. The waste in the river was emptied into the Tokyo Bay. 

Yamazaki’s team measured a maximum of 104,000 becquerels of cesium per square meter from the mud he and his study team collected in July 2016 in the same area of the bay. The cesium that was released at the beginning of the Fukushima plant meltdown was located upstream in the river in Chiba prefecture. The substances eventually moved downstream into the Tokyo Bay and seeped into the mud, Yamazaki told the publication. A becquerel is the International System of Units (SI) used to measure radioactivity. 

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Study: Cesium from Fukushima flowed to Tokyo Bay for 5 years [asahi.com]