The water to be released is being dumped to make storage room available for water with more dangerous levels of radiation.
Tokyo Electric Power has been pumping hundreds of tons of water into four of the six reactors at Fukushima Daiichi Nuclear Power Station to cool the nuclear fuel in the reactor core and in spent fuel storage pools. While much of that water is evaporating, a significant amount has also been discovered in various parts of the plant, which was crippled by the 9.0 magnitude earthquake and tsunami that struck northeast Japan on March 11.
Workers resorted to desperate measures including using sawdust and shredded newspaper in an effort to stem a direct leak of an estimated seven tons an hour of radioactive water escaping from a pit near the reactor.
Workers have focused especially on trying to pump out highly radioactive water flooding the turbine building of the No.
2 reactor. But a facility at the plant designed to store and treat the radioactive water has already been filled with runoff in recent days, the company said.
To free up space, about 10,000 tons of less seriously contaminated water will soon be released into the sea from the facility, said Yukio Edano, the chief cabinet secretary. Tokyo Electric said it has begun dumping water in the ocean in Japan, with a release of about 4,800 tons of water a day for two days.
An additional 1,500 tons of radioactive water will also be released from the No. 5 and No. 6 reactors, after runoff was found flooding parts of their turbine buildings. There are concerns that the water could damage the backup diesel generators for the reactors cooling systems, Mr. Edano said. Water from these reactors will be released 300 tons at a time over five days.
Unfortunately, the water contains a certain amount of radiation, Mr. Edano said. This is an unavoidable measure to prevent even higher amounts of radiation from reaching the sea.
The water that will be released contains about 100 times the legal limits of radiation, Tokyo Electric said. Consuming seafood caught in the area every day for a year would result in the intake of about 0.6 millisieverts of radiation, or about a quarter of average annual exposure to radiation in Japan, a company spokesman told a news conference. Mr. Edano said he ordered the company to monitor the effects of radioactive materials in the water on sea life.
Marine biologists, however, were not as sanguine as Tokyo Electric about the release of contaminated water into the ocean. They note that the amount of water making its way into the ocean has increased in recent days and would most likely continue for many more months. The government is also finding higher than normal levels of radioactive materials in the waters south of Fukushima.
Were seeing the levels of radioactive materials in the water increase, which means this problem is going to continue to get worse and worse, said Kenya Mizuguchi, professor emeritus at Tokyo University of Maritime Science and Technology.
The Japanese government has said it could take months to stem the release of radioactive material from the plant.
Elements like cesium 137, which has a half-life of 30 years, collect in larger fish as they consume smaller fish, which means the problem may accumulate over time. Iodine 131 and other elements that have far shorter half-lives are not as dangerous because it can take weeks for fish to make it to supermarkets and restaurants, according to Hiroki Otani, who teaches in the Health and Welfare Department at Tokyo Metropolitan University.
But Mr. Otani said that the government needed to release more data that illustrates the impact on shellfish and different types of seaweed that do not move around the ocean.
While levels of radioactive materials are much higher than normal, the mixing of radioactive water from the Fukushima plant with uncontaminated seawater can lead to a rapid decrease in radiation levels, according to an analysis by the International Atomic Energy Agency on April 1.
The IAEA, citing samples taken by Japanese authorities on March 24 and 27, said radiation levels in the water about 19 miles offshore from the nuclear plant were only about one-thousandth the level closer in, at about 360 yards from the shore. Nevertheless, the level of radiation at 19 miles offshore was still hundreds to thousands of times as high as levels sampled in the same location in 2005.
The IAEA said in a different analysis that the short-term concern from radioactive water would be iodine 131, owing to possible enrichment in the marine food chain.
Regardless of the scientific debate about the impact on marine life, businesses that make their living off of seafood are being hurt by the news about the release of contaminated water into the ocean. The price for some fish like inada, or young yellowtail, has fallen by half or more in recent days, according to Seizaburo Tsuruoka, the deputy chief of the Isumi-East Fisheries Cooperatives in Chiba Prefecture, south of Fukushima.
Mr. Tsuruoka said his fishermen test their fish and have not found that they are radioactive. He added that the ocean current is traveling from south to north this season. He worries, though, what will happen when the tide reverses in autumn.
While the government says, dont worry, the company says it will release water from the plant, he said. Im sure the general public feels very uncomfortable, and we get hurt.
Tokyo Electric Power has said it has little choice but to pump more water into the reactors at the moment, since the normal cooling systems at the plant are inoperable and extensive amounts of radioactive material would be released if the reactors melted down fully or if the rods caught fire.
Earlier, workers efforts to plug a leak of contaminated water from the nuclear plant by using sawdust, shredded newspaper and an absorbent powder appeared to be failing.
Water with high amounts of radioactive iodine has been leaking directly into the Pacific Ocean from a large crack discovered in a six-foot-deep pit next to the seawater intake pipes at the No. 2 reactor. Experts estimate that about seven tons an hour of radioactive water is escaping the pit. Safety officials have said that the water contains one million becquerels per liter of iodine 131, or about 10,000 times the levels normally found in water at a nuclear plant.
After an unsuccessful attempt to flood the pit with concrete to stop the leak, workers on Sunday turned to trying to plug the apparent source of the water an underground shaft thought to lead to the damaged reactor building with more than 120 pounds of sawdust, three garbage bags full of shredded newspaper and about nine pounds of a polymeric powder that officials said absorbed 50 times its volume of water.
To store more of the contaminated runoff, Tokyo Electric is rushing emergency tanks to the plant, though they may not arrive until mid-April, a company spokesman said. Tokyo Electric also plans to moor a giant artificial floating island off the coast to store contaminated water, though getting the island in place will take at least a week, he said.