TOKYO, April 1, Kyodo — More signs of serious radiation contamination in and near the Fukushima Daiichi nuclear power plant were detected Thursday, with the latest data finding groundwater containing radioactive iodine 10,000 times the legal threshold and the concentration of radioactive iodine-131 in nearby seawater rising to the highest level yet.
Radioactive material was confirmed from groundwater for the first time since the March 11 quake and tsunami hit the nuclear power plant on the Pacific coast, knocking out the reactors’ key cooling functions. An official of the plant operator Tokyo Electric Power Co. said, ”We’re aware this is an extremely high figure.”
The contaminated groundwater was found from around the No. 1 reactor’s turbine building, although the radiation level of groundwater is usually so low that it cannot be measured.
Japanese authorities were also urged to consider taking action over radioactive contamination outside the 20-kilometer evacuation zone around the plant, as the International Atomic Energy Agency said readings from soil samples collected in the village of Iitate, about 40 km from the plant, exceeded its criteria for evacuation.
The authorities denied that the seawater and soil contamination posed an immediate threat to human health, but the government said it plans to enhance radiation data monitoring around the plant on the Pacific coast, about 220 km northeast of Tokyo.
According to the government’s nuclear safety agency, the radioactive iodine-131 at a concentration of 4,385 times the maximum level permitted under law has been detected in a seawater sample collected Wednesday afternoon near the plant, exceeding the previous high recorded the day before.
In Tuesday’s sample, the concentration level was 3,355 times the maximum legal limit.
Hidehiko Nishiyama, a spokesman for the Nuclear and Industrial Safety Agency, acknowledged there is a possibility that radiation is continuing to leak into the sea, adding, ”We must check that (possibility) well.”
He reiterated that there are no immediate health concerns as fishing is not being conducted in the designated evacuation zone stretching 20 km from the plant and radioactive materials will be diluted by the time seafood is consumed by people.
Still, the nuclear regulatory body said it has decided to add another three areas located 15 km offshore for monitoring.
Tokyo Electric said it is likely that the high level of contamination in seawater has been caused by water that has been in contact with nuclear fuel or reactors, but how it flowed to the sea remains unknown.
The No. 1, No. 2 and No. 3 reactors at the plant are believed to have suffered damage to their cores, possibly releasing radioactive substances, while the fuel rods of the No. 4 reactor kept in a spent fuel pool are also believed to have been exposed at one point, as the reactors lost cooling functions after the March 11 quake and tsunami.
In Vienna on Wednesday, Denis Flory, IAEA deputy director general and head of the agency’s nuclear safety and security department, said readings from soil samples collected in Iitate between March 18 and March 26 ”indicate that one of the IAEA operational criteria for evacuation is exceeded (there).”
In response to the IAEA, Japan’s Chief Cabinet Secretary Yukio Edano said Thursday the government may implement measures, if necessary, such as urging people living in the area to evacuate, if it is found that the contaminated soil will have a long-term effect on human health.
Nishiyama said at a press conference in the afternoon that the agency’s rough estimates have shown there is no need for people in Iitate to evacuate immediately under criteria set by the Nuclear Safety Commission of Japan.
”The radiation dose of a person who was indoors for 16 hours and outdoors for eight hours (and continued such a lifestyle) would be about 25 millisieverts, which is about half the level which requires evacuation based on the commission’s criteria,” he said.
The commission explained that domestic criteria are based on measurements at radiation in the air, and not the soil.
In another effort to prevent radioactive dust from being dispersed from the plant, where masses of debris are strewn as a result of explosions, Tokyo Electric initially planned to conduct a test spraying of a water-soluble resin on Thursday, but postponed the plan due to rain.
An official said rain would have slowed down the work and made it difficult to gauge the effects of the resin spraying.
The utility firm known as TEPCO is considering when to conduct the work, at the south and west sides of the No. 4 reactor. A total of 60,000 liters will be sprayed over a period of two weeks.
TEPCO also tried to remove contaminated water filling up some of the reactors’ turbine buildings and tunnel-like trenches connected to them. But given the large amount of water, authorities are having difficulty finding places to store it.
TEPCO has been pouring massive amounts of water into the reactors and spent nuclear fuel pools at the plant as a stopgap measure to cool them down, because serious damage to fuel rods from overheating could lead to the release of enormous amounts of radioactive materials into the environment.
However, the measure is believed to be linked to the possible leak of radiation-contaminated water from the reactors, where fuel rods have partially melted.
Removal of the water at the turbine buildings is believed to be essential to restoring the vital functions to stably cool down the reactors and the spent nuclear fuel pools.
On Thursday afternoon, a ship provided by U.S. forces carrying fresh water to cool down the reactors docked on the coast of the plant site to help the mission of water injection.