Tokyo. March 22, 2011. Abnormally high levels of radioactive substances have been detected in seawater near the quake-crippled nuclear power plant in Japan, its operator said early Tuesday, cited by AFP. Five kinds of radioactive materials, including iodine-131, cesium-134 and cobalt, released by damaged fuel rods, were detected in the sea.
Tokyo Electric Power Co. (TEPCO) said the level of iodine-131 was 126.7 times higher and cesium-134 was 24.8 times higher than government-set standards. Cesium-137 was 16.5 times higher
The government limit is based on the amount of radioactive material that can be consumed by a person for a year, which is 1 millisievert. Although iodine-131 has a radioactive half-life of eight days, cesium-137's half-life is about 30 years.
At 2:30 p.m. Monday, TEPCO collected 500 milliliters of seawater at a point 100 meters south of the outlet, from which waste liquid is drained into the sea.
A total of 5.066 becquerel of iodine-131 per milliliter was detected, a level 126.7 times more than the yearly limit a person can safely ingest as set by the Nuclear Reactor Regulation Law.
If a person ingested two liters of water at this level of contamination over a three-day period, it would be equivalent to being exposed to an annual dose of radiation according to government-set safety standards, the Nuclear and Industrial Safety Agency said.
According to TEPCO, the operator of the crippled nuclear plant, there are two possible causes of the seawater contamination.
One is that the radioactive materials, blasted into the air after explosions at buildings housing the plant's Nos. 1 and 3 reactors, spread toward the Pacific and entered the sea when it rained. The other possible cause is that the water sprayed onto the Nos. 3 and 4 reactors washed the radioactive materials into the sea.
In a phenomenon called biological concentration, radioactive materials in seawater will become more concentrated in fish and marine plants.
The substances were detected in seawater which was sampled Monday about 100 kilometres (60 miles) south of the Fukushima No.1 plant. The radiation has spread to a wider area in the ocean beyond the immediate zone of the power plant raising alarm over impact on seafood.
However officials say it is too early to assess the radiation's impact on sea products.
Nevertheless seafood imports from Japan have dropped with some Korean retailers blocking sales altogether.
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