April 25, 2024

You are here: Home / Archives for reactors

300 Tons of Contaminated Water Leak From Japanese Nuclear Plant

August 20, 2013 by

Workers raced to place sandbags around the leak at the site to stem the spread of the water, a task made more urgent by a forecast of heavy rain for the Fukushima region later in the day. A spokesman at Tokyo Electric Power, the plant’s operator, acknowledged that much of the contaminated water had seeped into the soil and could eventually reach the ocean, adding to the tons of radioactive fluids that have already leaked into the sea from the troubled plant.

The leaked water contains levels of radioactive cesium and strontium many hundreds of times higher than legal safety limits, Tokyo Electric said. Exposure to either element is known to increase the risk of cancer.

The company said it had not determined the source of the leak.

“We must prevent the contaminated water from dispersing further due to rain and are piling up more sandbags,” said Masayuki Ono, a spokesman for the operator, also known as Tepco. But he also said much of the water has been absorbed into the soil, and workers would need to try to remove some of the soil using shovel cars and other heavy machinery.

Tepco has acknowledged in recent weeks that leaks of radioactive runoff at the site, about 150 miles north of Tokyo, are at crisis levels. The runoff comes from cooling water that workers are pumping into the damaged cores of the site’s three most damaged reactors, as well as from groundwater pouring into the breached basements of those reactors.

Some of that runoff has been seeping into the ocean since the accident at the site in 2011, triggered by a powerful earthquake and a 14-meter tsunami. To reduce the leaks, Tepco has started pumping out some of the contaminated water and storing it in almost 1,000 large tanks it has built on the debris-strewn site.

Tepco hopes to start cleansing the water using an elaborate filtering system and start releasing low-level contaminated water into the ocean. Those plans have been delayed by technical problems and protests from local fishermen.

Desperate for options, Japan’s nuclear regulator has suggested surrounding the plant with a huge underground ice wall to stem any leaks. That plan has its own drawbacks, however, and would require huge amounts of electricity almost indefinitely.

The latest leak comes from one of the site’s 1,000 tanks, about 500 yards inland, Tepco said. Workers discovered puddles of radioactive water near the tank on Monday. Further checks revealed that the 1,000-ton capacity vessel, thought to be nearly full, only contained 700 tons, with the remainder having almost certainly leaked out.

There had been concerns raised among some experts over the durability of the tanks. Mr. Ono said that Tepco had assumed the tanks would last at least five years, but the latest leak comes less than two years after the company started installing the storage vessels at the site to deal with the growing amounts of runoff.

“It is going to be very difficult and dangerous for Tepco to keep on storing all this water,” said Hiroshi Miyano, an expert in nuclear system design at Hosei University in Tokyo. He said, for example, that another strong earthquake or tsunami could destroy the tanks and lead to a huge spill.

At some point, Tepco will have no choice but to start releasing some of the water into the ocean after cleaning it, Dr. Miyano said. The continued mishaps at the site have heightened public scrutiny of Tepco and made it more difficult to build public consensus around any release of water, he said.

“That just makes the problem worse, with no viable solution,” he said.

The Nuclear Regulation Authority described the leak as a Level 1 incident, the lowest level, on a global scale that rates radiological releases. This was the first time that Japan had declared a radiological event since earthquake and tsunami in March 2011, which was rated at Level 7, the highest on that scale and on par with the 1986 accident at Chernobyl.

In a statement, the regulator ordered Tepco to do its utmost to identify the exact source of the leak, to step up radiation monitoring at the site and to remove contaminated soil. Tepco said it would do its best to comply.

Makiko Inoue contributed reporting from Tokyo.

Article source: http://www.nytimes.com/2013/08/21/world/asia/300-tons-of-contaminated-water-leak-from-japanese-nuclear-plant.html?partner=rss&emc=rss

Filed Under: Global Business Tagged With: , ,

Report Assails Japan Response to Fukushima Daiichi Nuclear Accident

December 27, 2011 by Leave a Comment

The failures, which the panel said worsened the extent of the disaster, were outlined in a 500-page interim report detailing Japan’s response to the calamitous events that unfolded at the Fukushima plant after the March 11 earthquake and tsunami knocked out all of the site’s power.

Three of the plant’s six reactors overheated and their fuel melted down, and hydrogen explosions blew the tops off three reactor buildings, leading to a major leak of radiation at levels not seen since Chernobyl in 1986.

The panel attacked the use of the term “soteigai,” or “unforeseen,” that plant and government officials used both to describe the unprecedented scale of the disaster and to explain why they were unable to stop it. Running a nuclear power plant inherently required officials to foresee the unforeseen, said the panel’s chairman, Yotaro Hatamura, a professor emeritus in engineering at the University of Tokyo.

“There was a lot of talk of soteigai, but that only bred perceptions among the public that officials were shirking their responsibilities,” Mr. Hatamura said.

According to the report, a final version of which is due by mid-2012, the authorities grossly underestimated the risks tsunamis posed to the plant. The charges echoed previous criticism made by nuclear critics and acknowledged by the operator of the plant, Tokyo Electric Power.

Tokyo Electric had assumed that no wave would reach more than about 20 feet. The tsunami hit at more than twice that height.

Officials of Japan’s nuclear regulator present at the plant during the quake quickly left the site, and when ordered to return by the government, they proved of little help to workers racing to restore power and find water to cool temperatures at the plant, the report said.

Also, the workers left at Fukushima Daiichi had not been trained to handle multiple failures, and lacked a clear manual to follow, the report said. A communications breakdown meant that workers at the plant had no clear sense of what was happening.

In particular, an erroneous assumption that an emergency cooling system was working led to hours of delay in finding alternative ways to draw cooling water to the plant, the report said. All the while, the system was not working, and the uranium fuel rods at the cores were starting to melt.

And devastatingly, the government failed to make use of data on the radioactive plumes released from the plant to warn local towns and direct evacuations, the report said. The failure allowed entire communities to be exposed to harmful radiation, the report said.

“Authorities failed to think of the disaster response from the perspective of victims,” Mr. Hatamura said.

But the interim report seems to leave ultimate responsibility for the disaster ambiguous. Even if workers had realized that the emergency cooling system was not working, they might not have been able to prevent the meltdowns.

The panel limited itself to suggesting that a quicker response might have mitigated the core damage and lessened the release of radiation into the environment.

“The aim of this panel is not to demand responsibility,” Mr. Hatamura said. He also said the panel’s findings should not affect debate on the safety of Japan’s four dozen other nuclear reactors.

Taro Umemura contributed reporting.

Article source: http://www.nytimes.com/2011/12/27/world/asia/report-condemns-japans-response-to-nuclear-accident.html?partner=rss&emc=rss

Filed Under: Global Business Tagged With: , ,

Hidden Dangers: In Japan Reactor Failings, Danger Signs for the U.S.

May 18, 2011 by Leave a Comment

The failure of the vents calls into question the safety of similar nuclear power plants in the United States and Japan. After the venting failed at the Fukushima plant, the hydrogen gas fueled explosions that spewed radioactive materials into the atmosphere, reaching levels about 10 percent of estimated emissions at Chernobyl, according to Japan’s nuclear regulatory agency.

Venting was critical to relieving pressure that was building up inside several reactors after the March 11 tsunami knocked out the plant’s crucial cooling systems. Without flowing water to cool the reactors’ cores, they had begun to dangerously overheat.

American officials had said early on that reactors in the United States would be safe from such disasters because they were equipped with new, stronger venting systems. But Tokyo Electric Power Company, which runs the plant, now says that Fukushima Daiichi had installed the same vents years ago.

Government officials have also suggested that one of the primary causes of the explosions was a several-hour delay in a decision to use the vents, as Tokyo Electric managers agonized over whether to resort to emergency measures that would allow a substantial amount of radioactive materials to escape into the air.

But the release this week of company documents and interviews with experts provides the most comprehensive evidence yet that mechanical failures and design flaws in the venting system also contributed to delays. The documents paint a picture of increasing desperation at the plant in the early hours of the disaster, as workers who had finally gotten the go-ahead to vent realized that the system would not respond to their commands.

While venting would have allowed some radioactive materials to escape, analysts say that those releases would have been far smaller than those that followed the explosions at three of the plant’s reactors, which blew open containment buildings meant to serve as a first line of defense against catastrophe. The blasts may also have been responsible for breaches in containment vessels that have complicated efforts to cool the fuel rods and contain radioactive leaks from the site.

One reason the venting system at the plant, which was built by General Electric, did not work is that it relied on the same sources of electricity as the rest of the plant: backup generators that were in basements at the plant and vulnerable to tsunamis. But the earthquake may also have damaged the valves that are part of the venting system, preventing them from working even when operators tried to manually open them, Tokyo Electric officials said.

In either case, regulators in the United States and Japan will now need to determine if such systems at similar plants designed by G.E. need to undergo expensive and time-consuming retrofitting or redesign to allow them to function even in severe accidents.

“Japan is going to teach us lessons,” said David Lochbaum at the Union of Concerned Scientists. “If we’re in a situation where we can’t vent where we need to, we need to fix that.”

Officials from General Electric did not comment on Tuesday.

The seriousness of the crisis at the Fukushima plant became evident within hours of the quake and the tsunami that rushed over the plant’s sea wall.

Just 12 hours after the quake, the pressure inside Reactor No. 1 had reached roughly twice the maximum pressure the unit had been designed to withstand, raising fears that the vessels that house fuel rods would rupture, setting a possible meltdown in motion. With the pressure high, pumping in additional cooling water also was not possible.

Hiroko Tabuchi reported from Tokyo, Keith Bradsher from Hong Kong, and Matthew L. Wald from Washington.

Article source: http://feeds.nytimes.com/click.phdo?i=ed48bce5135c87a7bcaf267e300186c9

Filed Under: Business News Tagged With: , ,