If you believe a lot of data on social media, you would think that the nuclear disaster at Fukushima has turned the entire Pacific Ocean into a dead zone. The review of the collected evidence presents a more rosy picture, but only as long as you stay away from Fukushima Harbor.
Fukushima disaster
After the tsunami hit Japan in March 2011, large amounts of radioactive material from the Fukushima nuclear reactors were released into the environment. It is estimated that 80% ended up in the Pacific Ocean, and the material that made it onto land was subsequently washed into the sea during floods. In addition, direct emissions from the plant to the ocean added another third of the original amount.
Radiation source
Promotional video:
The main source of radiation that Fukushima has released is cesium-137. Other radioactive isotopes are extremely rare to be perceived as a serious threat. Iodine-131 also got into the sea, but its half-life is so short that it is no longer a problem. According to data published in the annual review of marine sciences, the amount of radioactive material from Fukushima was equivalent to that released into the environment after the accident at Sellafield in the UK. Therefore, it would be strange if this had an apocalyptic impact on a planetary scale.
All studies agree that the released cesium-137 is between 15 and 25 * 1015 Becquerels. This figure indicates that the radiation cannot be limited to only a small region. Nevertheless, the Pacific Ocean is so vast that even if more radiation is concentrated in the region of Japan, it is highly diluted.
Measurements taken on the high seas from April to June 2011 show a 50% decrease in the amount of cesium-137 every seven days. Since cesium-137 has a 30-year half-life, this reduction suggests that the radioactive atoms are drowning rather than decaying.