The Yomiuri Shimbun
Tokyo Electric Power Co. said Tuesday seawater near an outlet at the quake-hit Fukushima No. 1 nuclear power plant had a concentration of radioactive iodine-131 that was 127 times higher than can be safely ingested by a person continuously for one year, according to government standards.
In a phenomenon called biological concentration, radioactive materials in seawater will become more concentrated in fish and marine plants.
It marked the first time for an analysis of radioactive materials in seawater to be made public since the struggle to contain a meltdown at the nuclear plant began.
As concern mounts over the possible impact on human health and on fishery products if the contamination continues for some time, the government will expand its survey area to get a clearer picture of the radioactive contamination in seawater.
"There should be no impact [on human health] if water of that [level of radioactive contamination] is consumed every day for one year," Chief Cabinet Secretary Yukio Edano said Tuesday. "Yet if the situation continues over time, there may be an adverse impact. We decided to increase our efforts in analyzing it."
He said it was too early to evaluate the impact of the contaminated seawater on fishery products. When asked whether restrictions on shipments would be imposed on marine products, like those taken on some farm products, Edano said it was possible, but it is not yet the time to do so.
Meanwhile, Economy, Trade and Industry Minister Banri Kaieda said, "We have to conduct [water quality] analyses in areas 10 kilometers and 20 kilometers [from the plant] soon."
Kaieda, who doubles as an assistant chief for a headquarters dealing with problems at the nuclear power plant, said the headquarters will send a survey vessel to take seawater samples in these areas.
The Hakoho Maru, a research vessel of the Japan Agency for Marine-Earth Science and Technology, will collect the samples Wednesday, with results of the analysis expected to be announced the following day.
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.
The seawater sample also had a level of cesium-134 that was 24.8 times more than the safety limit, while cesium-137 was 16.5 times above the safety limit.
According to TEPCO, 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.
"These aren't levels of contamination that pose an immediate impact," said Junko Matsubara, former professor at Yokohama City University. "Should the current level of concentration continue, however, consuming contaminated marine products could have an impact on the health."
(Mar. 23, 2011)
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