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Asshole
Administrator
Location: Chicago
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Just in case you aren't freaked out enough about the nuclear crisis, here's another little ditty:
Quote:
In Stricken Fuel-Cooling Pools, a Danger for the Longer Term
Even as workers race to prevent the radioactive cores of the damaged nuclear reactors in Japan from melting down, concerns were growing that nearby pools holding spent fuel rods could pose an even greater danger.
The pools, which sit on the top level of the reactor buildings and keep spent fuel submerged in water, have lost their cooling systems and the Japanese have been unable to take emergency steps because of the multiplying crises.
The threat is that the hot fuel will boil away the cooling water and catch fire, spreading radioactive materials far and wide in dangerous clouds.
The good news is that the Japanese have a relatively long time to deal with the problem. Nuclear experts estimate the timeline for serious problems that could lead to a reactor meltdown as minutes to hours, and put the comparable time for cooling pools at days to weeks.
The bad news is that if efforts to deal with the emergency fail, the results could be worse.
The pools are a worry at the stricken reactors at the Fukushima Daiichi plant because at least two of the three have lost their roofs in explosions, exposing the spent fuel pools to the atmosphere. By contrast, reactors have strong containment vessels that stand a better chance of bottling up radiation from a meltdown of the fuel in the reactor core.
Were the spent fuel rods in the pools to catch fire, nuclear experts say, the high heat would loft the radiation in clouds that would spread the radioactivity.
Its worse than a meltdown, said David A. Lochbaum, a nuclear engineer at the Union of Concerned Scientists who worked as an instructor on the kinds of General Electric reactors used in Japan. The reactor is inside thick walls, and the spent fuel of Reactors 1 and 3 is out in the open.
A spokesman for the Japanese company that runs the stricken reactors said in an interview on Monday that the spent fuel at the Fukushima Daiichi and Daini plants had been left uncooled since shortly after the quake.
The company, Tokyo Electric, has not been able to cool the spent fuel pools because power has been knocked out, said Johei Shiomi, the spokesman. There may be some heating up, he said.
Some scientists said that a worst-case outcome was unlikely and that the Japanese would probably have enough time to act before too much water boiled away. Firefighters with hoses can pour in water, they said, or helicopters could drop tons of water.
Im still hopeful that they can contain all this, Thomas B. Cochran, a senior scientist in the nuclear program of the Natural Resources Defense Council , a private group in Washington, said in an interview. Youve got time to put fire hoses up there and get it filled if its not leaking, he said of the pool.
A 1997 study by the Brookhaven National Laboratory on Long Island described a worst-case disaster from uncovered spent fuel in a reactor cooling pool. It estimated 100 quick deaths would occur within a range of 500 miles and 138,000 eventual deaths.
The study also found that land over 2,170 miles would be contaminated and damages would hit $546 billion.
That section of the Brookhaven study focused on boiling water reactors the kind at the heart of the Japanese crisis.
The threat is considered so severe that at the start of the crisis Friday, immediately after the shattering earthquake, Fukushima plant officials focused their attention on a damaged storage pool for spent nuclear fuel at the No. 2 reactor at Daiichi, said a nuclear executive who requested anonymity because his company is not involved in the emergency response at the reactors and is wary of antagonizing other companies in the industry.
The damage prompted the plants management to divert much of the attention and pumping capacity to that pool, the executive added. The shutdown of the other reactors then proceeded badly, and problems began to cascade.
Mr. Shiomi of Tokyo Electric said that in addition to the power and cooling failures, some water had spilled from the pools.
But he said that the company thought there was relatively little danger that temperatures would rise.
If you compare this to everything thats been going on, Mr. Shiomi said, its not serious.
Each of the crippled reactors in Japan has one cooling pool sitting atop the main concrete structure. Thin roofs and metal walls usually surround the pools.
In a reactor pool, the time it takes uncooled fuel to begin boiling the surrounding water depends on how much fuel is present and how old it is. Fresh fuel is hotter in terms of radiation than old fuel is.
Mr. Lochbaum, who formerly taught reactor operation for the Nuclear Regulatory Commission , said the pools measured about 40 feet long, 40 feet wide and 45 feet deep. The spent fuel, he added, rested at the pools bottom and rose no higher than 15 feet from the bottom.
That means that in normal operations, the spent fuel is covered by about 30 feet of cooling water.
Depending on the freshness of the spent fuel, Mr. Lochbaum said, the water in an uncooled pool would start to boil in anywhere from days to a week. The water would boil off to a dangerous level in another week or two.
Once most of the fuel is exposed, he said, it can catch fire.
If the spent fuel is a few months old, most of the iodine 131 one of the most dangerous radioactive byproducts in spent fuel will have decayed into harmless forms.
But the cesium 137 in the spent fuel has a half-life of 30 years, meaning it would take about two centuries to diminish its levels of radioactivity down to 1 percent.
It is cesium 137 that still contaminates much land in Ukraine around the Chernobyl reactor, which suffered a meltdown in 1986.
I assume they are doing triage, Mr. Lochbaum said of the Japanese, with emergency personnel first trying to avoid core meltdowns and then turning their attention to the cooling pools.
He added that the explosions at the reactors at Daiichi could complicate efforts to try to reach the cooling pools and keep them filled with water.
Theres no telling whats up there, he said.
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---------- Post added at 08:47 AM ---------- Previous post was at 08:02 AM ----------
Apparently, the worst case is happening and I was reading an article that was written before the event started:
Quote:
SOMA, Japan – 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.
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.
[Related: What is acute radiation syndrome?]
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.
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Radiation level soars after Japan nuke plant fire - Yahoo! News
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