The Yomiuri Shimbun
Radioactive iodine-131 at a concentration about 1,250 times the legal limit was detected in seawater collected Friday morning about 330 meters south of drain outlets for the troubled reactors at the Fukushima No. 1 nuclear plant, the government said Saturday.
The government's Nuclear and Industrial Safety Agency said the level of iodine-131 was 50 becquerels per 1 milliliter, 1,250 times the limit under the Law on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors.
It was about 10 times the level of iodine-131 sampled Monday at the same point, the agency said.
If a person drank 500 milliliters of water with the Friday morning level of idodine-131, he or she would be exposed to 1 millisievert of radiation, the annual total permissible for an average person.
Plant operator Tokyo Electric Power Co. said it is highly likely contaminated water was discharged directly into the sea from reactor pipes or other locations, as the radiation level in the air was not increasing and it had not rained for several days.
"The amount poses no immediate risk to nearby residents. The contaminated water will diffuse in the sea and dilute," said Hidehiko Nishiyama, a high ranking official of the agency under the Economy, Trade and Industry Ministry.
According to the agency, the sampling point was about 330 meters south of the drain outlets of the Nos. 1 to 4 reactors. The outlets are about 200 meters away from the No. 4 reactor.
The level of iodine-131 in the seawater taken at the same sampling point Monday afternoon was 5.1 becquerels per 1 milliliter, 127 times the safety limit. The concentration of the same substance in water sampled Thursday morning was 104 times the safety limit, according to the agency.
The levels of other radioactive substances in the sampled water were also high, the agency said.
The level of cesium-134 was 117 times more than the safety limit, while cesium-137 was 80 times the standard, according to the agency.
In the seawater sample taken Friday near TEPCO's Fukushima No. 2 nuclear power station, located about 16 kilometers from the No. 1 plant, the concentration level of iodine-131 was 9.2 times the safety limit, the agency said. The levels of cesium-134 and 137 were within safety limits, it said.
"The connection with the water contaminated by highly radioactive substances in the basements of the turbine buildings of the Nos. 1 to 3 reactors can't be denied," a TEPCO official said. Seawater will be sampled and checked more frequently, according to TEPCO.
"Currently, no fishermen are operating within a 20-kilometer radius of the plant, as the area is subject to evacuation. Therefore, it will pose no immediate health risk to local residents," Nishiyama said.
Investigation of seawater by a ship belonging to the Education, Culture, Sports, Science and Technology Ministry showed no major changes in radioactive substances about 30 kilometers off the coast where the plant is located, he added.
"People won't directly consume seawater containing such high levels of radioactive substances. There's no need to worry about health risks, even if you ate fish exposed to the radiation for a short period of time," said Atsushi Kasai, former laboratory head of the Japan Atomic Energy Research Institute, now the Japan Atomic Energy Agency.
"However, radioactive iodine accumulates easily in seaweed. Some measures should be taken to prevent groundless rumors from harming the fishery and marine products industries."
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More dangerous puddles found
TEPCO said Saturday high levels of radiation were also detected in puddles at the No. 2 reactor of the Fukushima No. 1 nuclear power plant. Water in the puddles apparently leaked from the reactor, the company said.
Three workers were exposed to a high level of radiation Thursday while working in water at the No. 3 reactor. Water contaminated with radiation was found at the No. 1 reactor, too.
As at the Nos. 1 and 3 reactors, puddles were found on the basement floor of the No. 2 reactor. The puddles' likeliest source is leakage from pipes and pumps connected to the nuclear reactor, the utility company said.
TEPCO also said restoration work was falling behind schedule because water contaminated with radiation was found where power cables must be laid to reactivate the cooling system of the reactor.
The company said that it detected radiation of 300 milisieverts per hour on the surface of water found at the first basement level of the No. 2 reactor's turbine building.
TEPCO said that it would continue to analyze the water because it was suspected to have leaked from the reactor.
(Mar. 27, 2011)
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