At least 2 trillion becquerels’ worth of radioactive material flowed from the crippled Fukushima Daiichi nuclear power plant into the Pacific Ocean between August 2013 and May 2014, plant operator Tokyo Electric Power Company (TEPCO) has admitted. The rate of release was 10 times higher than TEPCO’s pre-meltdown threshold for radioactive material.
A becquerel is a unit for measuring radioactive material that corresponds to one unit of radioactive decay per second. It is a way of describing how much radiation is being emitted by radioactive material, in contrast to measuring the mass or volume of the material itself, the energy carried by the radiation or the biological impact of exposure.
Radioactive sludge accumulating in bay
In March 2011, the Fukushima plant suffered multiple meltdowns triggered by a massive earthquake and tsunami. Since then, TEPCO has struggled to contain the flow of radioactive water away from the plant. Currently, radioactive water is known to be leaking out of reactor buildings and downstream into the ocean. It is also suspected to be leaking into the ground from the plant, and flowing underground to the ocean from there.
TEPCO estimates that this water has been carrying 4.8 billion becquerels of strontium-90 and 2 billion becquerels of cesium-137 every day, based on measurements taken near the water intakes for reactors 1 through 4. This means that in the 10 months from August to May, the plant emitted 1.46 trillion becquerels’ worth of strontium-90 and 610 billion becquerels of cesium-137, totaling 2.07 trillion becquerels of radioactivity released into the ocean.