 |
| Japan Dumps Radioactive Water Into Ocean |
By Hiroko Tabuchi and Ken Belson, The New York Times, April 4, 2011
The Tokyo Electric Power Company began dumping more than 11,000 tons of radioactive water from the Fukushima Daiichi nuclear plant into the Pacific Ocean on Monday, mostly to make room in storage containers for increasing amounts of far more contaminated runoff.
The water, most of it to be released over two days, contains about 100 times the legal limit of radiation, Tokyo Electric said. The more contaminated water has about 10,000 times the legal limit.
The effort would help workers clearing radioactive water from the turbine buildings at the damaged reactors, making it less dangerous to reach some of the most crucial controls for their cooling systems, which were knocked out by the 9.0-magnitude earthquake and tsunami that struck northeast Japan on March 11. The hopes are that the cooling systems can be revived and bring the plant back under control.
But the pumping effort is not expected to halt, or even alter, a gushing leak from a large crack in a six-foot-deep pit next to the seawater intake pipes near the No. 2 reactor. The leak, discovered Saturday, has been spewing an estimated seven tons of highly radioactive water an hour directly into the ocean; attempts to trace and plug it have so far failed.
Tokyo Electric, the plant’s operator, has been pumping hundreds of tons of water into four of the plant’s six reactors to cool nuclear fuel in the cores of three and in spent-fuel storage pools at those three and a fourth.
But leaks whose source is unclear — from the reactor containment units themselves or from pipes, valves or other connected units — have flooded areas of the plant, creating new complications in the effort to stave off full meltdowns of the fuel.
Workers have been pumping the runoff into storage tanks, most urgently the highly radioactive water flooding the turbine building of the No. 2 reactor. But the storage system is now full, and adding capacity will take time.
Tokyo Electric is rushing tanks to the plant, though they may not arrive until mid-April, a company spokesman said. The company also plans to moor a giant artificial island off the coast to store contaminated water, though getting the island in place will take at least a week, he said.
Tokyo Electric said it would dump about 4,800 tons of water a day for two days. An additional 1,500 tons will also be released from the No. 5 and No. 6 reactors, after runoff was found flooding parts of their turbine buildings.
The concern there is that the water could damage the backup diesel generators for the reactors’ cooling systems, said Yukio Edano, the chief cabinet secretary. That water 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.”
Mr. Edano said he had ordered the company to monitor the effects of radioactive materials in the water on sea life. 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 the average annual exposure to radiation in Japan, a company spokesman said at a news conference.
But the Japanese government has said it could take months to stem the release of radioactive material from the plant, and marine biologists expressed concern.
“We’re 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, emeritus professor of maritime science and technology at Tokyo University.
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 grow 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 the government needed to share more data on the impact on shellfish and different types of seaweed that do not move around the ocean.
Mixing radioactive water with uncontaminated seawater can lead to a rapid decrease in radiation levels, according to an analysis by the International Atomic Energy Agency on Friday.
The agency, citing samples taken by the 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 site in 2005.
The agency 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.”
Seafood businesses are being hurt. The price for some fish like inada, or young yellowtail, has fallen by half or more in recent days, according to Seizaburo Tsuruoka, deputy chief of the Isumi-East Fisheries Cooperatives in Chiba Prefecture, south of Fukushima.
Mr. Tsuruoka said his fishermen tested their fish and had not found that they were radioactive. He added that the ocean current was traveling from south to north this season. He worries, though, what will happen when the tide reverses in autumn.
“While the government says, ‘Don’t worry,’ the company says it will release water from the plant,” Mr. Tsuruoka said. “I’m sure the general public feels very uncomfortable, and we get hurt.”
To try to prevent radioactive silt from drifting deeper into the ocean, Tokyo Electric intends to drape a curtain in the waters off the plant, Reuters reported, quoting Hidehiko Nishiyama, deputy director general of Japan’s Nuclear and Industrial Safety Agency.
In Vienna on Monday, Japan’s crisis was a major focus as the International Atomic Energy Agency began a 10-day gathering of representatives of dozens of countries on nuclear safety.
No comments:
Post a Comment