Abstract

The Tokyo Electric Power Company Fukushima Dai-ichi nuclear power plant in Fukushima-Ken (Prefecture), Japan, was destroyed in March 2011 due to a massive earthquake (magnitude 9) centred offshore to the northeast of Honshu Island and the subsequent historic tsunami on 11 March 2011. Due to nuclear meltdown, damage to the buildings housing the reactors by hydrogen explosions, and the contamination of cooling water from the reactor cores, huge quantities of radioisotopes were emitted to the atmosphere and to the adjacent seawater. Fishing is currently prohibited off the coast of Fukushima-Ken because intermittent surveys have found that the majority of fishery products still contain radioisotope levels exceeding the Japanese Standard Value. However, the total amount of caesium radioisotopes in fish biomass in the Fukushima-Ken Exclusive Economic Zone (EEZ) has not yet been reported. The Tokyo University of Marine Science and Technology has measured radioisotope levels in fishery species off Iwaki-Shi (City), Fukushima-Ken (located south of the destroyed nuclear power plant), and these data can be used to estimate the total fish biomass and the quantity of caesium radioisotopes in fish in the Fukushima-Ken EEZ. On 22 to 23 November 2012, the estimated total fish biomass in the Fukushima-Ken EEZ was 91,150,218.79 kg and the estimated total quantities of Cs-134 and Cs-137 in fish were 4,879,259,657 Bq and 8,381,002,727 Bq, respectively.

Key words: Nuclear power plant, Exclusive Economic Zone (EEZ), radioisotope.