Showing posts with label Meltdown threat rises at Japanese nuclear plant. Show all posts
Showing posts with label Meltdown threat rises at Japanese nuclear plant. Show all posts

Tuesday, March 15, 2011

Radiation level soars after Japan nuke plant fire

SOMA, Japan (AP) — Dangerous levels of radiation leaking from a crippled nuclear plant forced Japan to order 140,000 people to seal themselves indoors Tuesday after an explosion and a fire dramatically escalated the crisis spawned by a deadly tsunami.
In a nationally televised statement, Prime Minister Naoto Kan said radiation had spread from the four stricken reactors of the Fukushima Dai-ichi nuclear plant along Japan's northeastern coast. The region was shattered by Friday's 9.0-magnitude earthquake and the ensuing tsunami that is believed to have killed more than 10,000 people, plunged millions into misery and pummeled the world's third-largest economy.
Japanese officials told the International Atomic Energy Agency that the reactor fire was in a fuel storage pond — an area where used nuclear fuel is kept cool — and that "radioactivity is being released directly into the atmosphere." Long after the fire was extinguished, a Japanese official said the pool might still be boiling, though the reported levels of radiation had dropped dramatically by the end of the day.
Women wail together after hearing the death of family members at an evacuation center in Kesennuma in Miyagi prefecture (state) Tuesday, March 15, 2011, after Friday's massive earthquake and tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO LICENSING IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
That reactor, Unit 4, had been shut down before the quake for maintenance.
If the water boils, it could evaporate, exposing the rods. The fuel rods are encased in safety containers meant to prevent them from resuming nuclear reactions, nuclear officials said. But they acknowledged that there could have been damage to the containers. They also confirmed that the walls of the storage pool building were damaged.
Experts noted that much of the leaking radiation was apparently in steam from boiling water. It had not been emitted directly by fuel rods, which would be far more virulent, they said.
"It's not good, but I don't think it's a disaster," said Steve Crossley, an Australia-based radiation physicist.
Even the highest detected rates were not automatically harmful for brief periods, he said.
"If you were to spend a significant amount of time — in the order of hours — that could be significant," Crossley said.
Less clear were the results of the blast in Unit 2, near a suppression pool, which removes heat under a reactor vessel, said plant owner Tokyo Electric Power Co. The nuclear core was not damaged but the bottom of the surrounding container may have been, said Shigekazu Omukai, a spokesman for Japan's nuclear safety agency.
Though Kan and other officials urged calm, Tuesday's developments fueled a growing panic in Japan and around the world amid widespread uncertainty over what would happen next. In the worst case scenario, one or more of the reactor cores would completely melt down, a disaster that could spew large amounts of radioactivity into the atmosphere.
"I worry a lot about fallout," said Yuta Tadano, a 20-year-old pump technician at the Fukushima plant, who said he was in the complex when the quake hit.
"If we could see it, we could escape, but we can't," he said, cradling his 4-month-old baby, Shoma, at an evacuation center.
The radiation fears added to the catastrophe that has been unfolding in Japan, where at least 10,000 people are believed to have been killed and millions of people were facing a fifth night with little food, water or heating in near-freezing temperatures and snow as they dealt with the loss of homes and loved ones. Up to 450,000 people are in temporary shelters.
Officials have only been able to confirm a far lower toll — about 3,300 killed — but those who were involved in the 2004 Asian tsunami said there was no question more people died and warned that, like the earlier disaster, many thousands may never be found.
Asia's richest country hasn't seen such hardship since World War II. The stock market plunged for a second day and a spate of panic buying saw stores running out of necessities, raising government fears that hoarding may hurt the delivery of emergency food aid to those who really need it.
In a rare bit of good news, rescuers found two survivors Tuesday in the rubble left by the tsunami that hit the northeast, including a 70-year-old woman whose house was tossed off its foundation.
The Fukushima Dai-ichi nuclear complex, along that battered coastline, has been the focus of the worries. Workers there have been desperately trying to use seawater to cool the fuel rods in the complex's three reactors, all of which lost their cooling ability after Friday's quake and tsunami.
On Tuesday, the complex was hit by its third explosion since Friday, and then a fire in a separate reactor.
Afterward, officials in Ibaraki, a neighboring prefecture just south of the area, said up to 100 times the normal levels of radiation were detected Tuesday. While those figures are worrying if there is prolonged exposure, they are far from fatal.
Tokyo reported slightly elevated radiation levels, but officials said the increase was too small to threaten the 39 million people in and around the capital, about 170 miles (270 kilometers) away. Closer to the stricken nuclear complex, the streets in the coastal city of Soma were empty as the few residents who remained there heeded the government's warning to stay indoors.
Kan and other officials warned there is a danger of more leaks and told people living within 19 miles (30 kilometers) of the Fukushima Dai-ichi complex to stay indoors to avoid exposure that could make people sick.
"Please do not go outside. Please stay indoors. Please close windows and make your homes airtight," Chief Cabinet Secretary Yukio Edano told residents in the danger zone.
"These are figures that potentially affect health. There is no mistake about that," he said.
Weather forecasts for Fukushima were for snow and wind Tuesday evening, blowing southwest toward Tokyo, then shifting and blowing east out to sea. That's important because it shows which direction a possible nuclear cloud might blow.
Some 70,000 people had already been evacuated from a 12-mile (20-kilometer) radius from the Dai-ichi complex. About 140,000 remain in the new danger zone.
Officials said 70 workers were at the complex, struggling with its myriad problems. The workers, all of them wearing protective gear, are being rotated in and out of the danger zone quickly to reduce their radiation exposure.
Another 800 staff were evacuated. The fires and explosions at the reactors have injured 15 workers and military personnel and exposed up to 190 people to elevated radiation.
Temperatures in at least two of the complex's reactors, units 5 and 6, were also slightly elevated, Edano said.
"The power for cooling is not working well and the temperature is gradually rising, so it is necessary to control it," he said.
Fourteen pumps have been brought in to get seawater into the other reactors. They are not yet pumping water into Unit 4 but are trying to figure out how to do that.
In Tokyo, slightly higher-than-normal radiation levels were detected Tuesday but officials insisted there are no health dangers.
"The amount is extremely small, and it does not raise health concerns. It will not affect us," Takayuki Fujiki, a Tokyo government official said.
Edano said the radiation readings had fallen significantly by the evening.
Japanese government officials are being rightly cautious, said Donald Olander, professor emeritus of nuclear engineering at University of California at Berkeley. He believed even the heavily elevated levels of radiation around Dai-ichi are "not a health hazard." But without knowing specific dose levels, he said it was hard to make judgments.
"Right now it's worse than Three Mile Island," Olander said. But it's nowhere near the levels released during Chernobyl.
On Three Mile Island, the radiation leak was held inside the containment shell — thick concrete armor around the reactor. The Chernobyl reactor had no shell and was also operational when the disaster struck. The Japanese reactors automatically shut down when the quake hit and are encased in containment shells.
Rescuers were heartened Tuesday to find two survivors.
Seventy-year-old Sai Abe was pulled from her toppled home in the port town of Otsuchi. She was suffering from hypothermia but appeared to have no life-threatening injuries, rescue official Yuko Kotani said.
Another survivor, described as being in his 20s, was shown on television being pulled from a building further down the coast in the city of Ishimaki after rescue workers heard him calling for help.
The impact of the earthquake and tsunami dragged down stock markets. The benchmark Nikkei 225 stock average plunged for a second day Tuesday, nose-diving more than 10 percent to close at 8,605.15 while the broader Topix lost more than 8 percent.
To lessen the damage, Japan's central bank made two cash injections totaling 8 trillion yen ($98 billion) Tuesday into the money markets after pumping in $184 billion on Monday.
Initial estimates put repair costs in the tens of billions of dollars, costs that would likely add to a massive public debt that, at 200 percent of gross domestic product, is the biggest among industrialized nations.
The Dai-ichi plant is the most severely affected of three nuclear complexes that were declared emergencies after suffering damage in Friday's quake and tsunami, raising questions about the safety of such plants in coastal areas near fault lines and adding to global jitters over the industry.

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Monday, March 14, 2011

Meltdown threat rises at Japanese nuclear plant

SOMA, Japan (AP) — Water levels dropped precipitously Monday inside a stricken Japanese nuclear reactor, twice leaving the uranium fuel rods completely exposed and raising the threat of a meltdown, hours after a hydrogen explosion tore through the building housing a different reactor.
Water levels were restored after the first decrease but the rods remained exposed late Monday night after the second episode, increasing the risk of the spread of radiation and the potential for an eventual meltdown.
The cascading troubles in the Fukushima Dai-ichi plant compounded the immense challenges faced by the Tokyo government, already struggling to send relief to hundreds of thousands of people along the country's quake- and tsunami-ravaged coast where at least 10,000 people are believed to have died.
Later, a top Japanese official said the fuel rods in all three of the most troubled nuclear reactors appeared to be melting.
Of all these troubles, the drop in water levels at Unit 2 had officials the most worried.
"Units 1 and 3 are at least somewhat stabilized for the time being," said Nuclear and Industrial Agency official Ryohei Shiomi "Unit 2 now requires all our effort and attention."
In some ways, the explosion at Unit 3 was not as dire as it might seem.
Residents evacuated from areas surrounding the Fukushima nuclear facilities damaged in Friday's massive earthquake, are checked for radiation contamination, Sunday, March 13, 2011, in Koriyama city, Fukushima prefecture, Japan. (AP Photo/Wally Santana)

The blast actually lessened pressure building inside the troubled reactor, and officials said the all-important containment shell — thick concrete armor around the reactor — had not been damaged. In addition, officials said radiation levels remained within legal limits, though anyone left within 12 miles (20 kilometers) of the scene was ordered to remain indoors.
"We have no evidence of harmful radiation exposure," deputy Cabinet secretary Noriyuki Shikata told reporters.
On Saturday, a similar hydrogen blast destroyed the housing around the complex's Unit 1 reactor, leaving the shell intact but resulting in the mass evacuation of more than 185,000 people from the area.
So the worst case scenario still hung over the complex, and officials were clearly struggling to keep ahead of the crisis.
Late Monday, the chief government spokesman said there were signs that the fuel rods were melting in all three reactors, all of which had lost their cooling systems in the wake of Friday's massive earthquake and tsunami
"Although we cannot directly check it, it's highly likely happening," Chief Cabinet Secretary Yukio Edano told reporters.
Some experts would consider that a partial meltdown. Others, though, reserve that term for times when nuclear fuel melts through a reactor's innermost chamber but not through the outer containment shell.
By contrast, a complete reactor meltdown, where the uranium core melts through the containment shell, would release a wave of radiation and result in major, widespread health problems.
The Monday morning explosion at the Fukushima Dai-ichi plant's Unit 3 injured 11 workers and came as authorities were trying to use sea water to cool the complex's three reactors.
While four Japanese nuclear complexes were damaged in the wake of Friday's twin disasters, the Dai-ichi complex, which sits just off the Pacific coast and was badly hammered by the tsunami, has been the focus of most of the worries over Japan's deepening nuclear crisis. All three of the operational reactors at the complex now have faced severe troubles.
Operators knew the sea water flooding would cause a pressure buildup in the reactor containment vessels — and potentially lead to an explosion — but felt they had no choice if they wanted to avoid complete meltdowns. Eventually, hydrogen in the released steam mixed with oxygen in the atmosphere and set off the two blasts.
Japan's meteorological agency did report one good sign. It said the prevailing wind in the area of the stricken plant was heading east into the Pacific, which experts said would help carry away any radiation.
Across the region, though, many residents expressed fear over the situation.
People in the port town of Soma had rushed to higher ground after a tsunami warning Monday — a warning that turned out to be false alarm — and then felt the earth shake from the explosion at the Fukushima reactor 25 miles (40 kilometers) away. Authorities there ordered everyone to go indoors to guard against possible radiation contamination.
"It's like a horror movie," said 49-year-old Kyoko Nambu as she stood on a hillside overlooking her ruined hometown. "Our house is gone and now they are telling us to stay indoors.
"We can see the damage to our houses, but radiation? ... We have no idea what is happening. I am so scared."
Meanwhile, 17 U.S. military personnel involved in helicopter relief missions were found to have been exposed to low levels of radiation after the flew back from the devastated coast to the USS Ronald Reagan, an aircraft carrier about 100 miles (160 kilometers) offshore.
U.S. officials said the exposure level was roughly equal to one month's normal exposure to natural background radiation, and the 17 were declared contamination-free after scrubbing with soap and water.
As a precaution, the U.S. said the carrier and other 7th Fleet ships involved in relief efforts had shifted to another area.
While Japan has aggressively prepared for years for major earthquakes, reinforcing buildings and running drills, the impact of the tsunami — which came so quickly that not many people managed to flee to higher ground — was immense.
By Monday, officials were overwhelmed by the scale of the crisis, with millions of people facing a fourth night without electricity, water, food or heat in near-freezing temperatures.
International scientists say there are serious dangers but little risk of a catastrophe like the 1986 blast in Chernobyl, where there was no containment shells.
And, some analysts noted, the length of time since the nuclear crisis began indicates that the chemical reactions inside the reactor were not moving quickly toward a complete meltdown.
"We're now into the fourth day. Whatever is happening in that core is taking a long time to unfold," said Mark Hibbs, a senior associate at the nuclear policy program for the Carnegie Endowment for International Peace. "They've succeeded in prolonging the timeline of the accident sequence."
He noted, though, that Japanese officials appeared unable to figure out what was going on deep inside the reactor. In part, that was probably because of the damage done to the facility by the tsunami.
"The real question mark is what's going on inside the core," he said.
Overall, more than 1,500 people had been scanned for radiation exposure in the area, officials said.

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.