TOKYO—The Japanese government will provide new details on the deliberate discharge of 10,000 tons of low-level radioactive water from the Fukushima Daiichi nuclear power plant into the ocean in an acknowledgment of criticism both at home and abroad that it should have provided more advance notice.
View Full Image
Kyodo News/Associated Press
Workers land tuna Thursday at Shiogama port in northeast Japan's Miyagi prefecture for the first time since tsunami waves devastated the coast.
The dumping—which began April 4 and is continuing, although government officials say the flow has eased significantly—was an emergency move undertaken by plant operator Tokyo Electric Power Co. to make room at the site to store water with much-higher radiation readings. While the government approved the dumping, it was criticized by China and South Korea as well as the local fishing industry over the potential impact on the ocean.
Hidehiko Nishiyama, senior official and spokesman at the Nuclear and Industrial Safety Agency, said Thursday that Japan has a responsibility to provide additional information because "there are countries that are worried about the impact of the operation on the ocean." Japan's disclosure will include its own assessment of the dumping, including the amount of water as well as the radiation levels involved.
Mr. Nishiyama said the information would be released soon but didn't provide a specific time.
Radiation levels in the seawater near the plant have dropped significantly—now 20 to 40 times Japan's allowable limit for certain radioactive isotopes, compared with thousands of times those limits last week.
While determining the source of the lingering radiation in the water is difficult, current levels are likely from the plant's controlled discharges as well as other sources, like groundwater near the plant and particles falling from the air. Tepco workers also plugged a leak last week from reactor No. 2, which was releasing highly radioactive water into the sea.
Japan acknowledges that it made only a brief mention of its planned dumping operation in a briefing for foreign missions in Tokyo held just three hours before it began. A faxed message was sent to the foreign missions only after the operation began, Japanese media reported.
On April 4, shortly before Tepco began dumping the water, government officials said the water had radioactive iodine-131 contamination of around 100 times, but sometimes as much as 500 times, what is considered safe. It also said the water had cesium-134 and cesium-137 that was some 50-70 times above acceptably safe levels.
View Full Image
Associated Press
Japanese Emperor Akihito, left, and Empress Michiko, visit an evacuation shelter in Asahi City Thursday, during their first trip to the disaster zone since the March 11 earthquake and tsunami.
Water has been a persistent problem throughout the nuclear crisis, which began March 11 when an earthquake and tsunami knocked out power at the facility, allowing nuclear fuel to heat up. The tsunami itself left water remaining on the site, while more water was added during the weeks of water-spraying designed to prevent the plant's reactors from overheating.
According to Tepco, nearly 27,000 tons of water in total was pumped into the most heavily damaged reactors Nos. 1-3.With each reactor built to hold about 300 tons of water, the overflow has flooded into other parts of the complex or evaporated into the atmosphere.
"We wanted to avoid releasing radioactive water into the ocean. But that was an unavoidable operation," Mr. Nishiyama said. "We also failed to provide proper notice to neighboring countries."
His comments echoed remarks on April 6 by chief government spokesman Yukio Edano, who said that "we should have provided a more detailed explanation to related ministries and surrounding countries" about the release.
The dumping was part of an effort to stop highly radiated and dangerous water in a utility trench at reactor No. 2 from overflowing into the ocean. According to NISA, 660 tons of the tainted water have been pumped out of the trench by Thursday, but the level of water has fallen by only a few centimeters. NISA has previously estimated that each of the three reactors have 20,000 tons of water that needs to be safely stored.
A new concern arose late Wednesday with the discovery that the radioactivity of water in reactor No. 4's spent fuel pool was vastly higher than normal. A sample of water taken Tuesday contained 220 becquerels of iodine-131 per cubic centimeter. That compares with a level of just 0.01 becquerels or less for normal spent fuel pools. Such pools hold previously used nuclear fuel, allowing it to slowly cool down over a matter of years.
The elevated radioactivity points to either the fuel in the pool being partially or somewhat damaged or radioactive materials from other reactors having landed in the pool from one of the explosions that occurred in the first week of the crisis.
But Mr. Nishiyama said "the results indicate that the fuel is largely undamaged" and noted that the pool also has active fuel that was meant to go back into the reactor following maintenance.
Authorities also reported a sudden increase in the temperature at one of the seals in the pressure vessel of reactor No. 3, to about 250 degrees Celsius on Thursday from 170 degrees Tuesday. The temperature remained little changed in other parts of the vessel.
A Tepco spokesman said the observed increase might be due to a faulty gauge, and workers would investigate further. Reactor No. 3 has had the lowest temperatures of the three units and isn't considered to be at an immediate risk of overheating.
miyagi prefecture, nuclear power plant, kyodo news, electric power co, radioactive isotopes, northeast japan, tsunami waves, radiation levels, radioactive water, tokyo electric, fishing industry, plant operator, safety agency, fukushima, industrial safety, japanese government, new details, seawater, advance notice, south korea
沒有留言:
張貼留言