17 March 2011

Japan Tsunami + Earthquake : NUCLEAR ALERT !!!!

Nuclear crisis deepens 
2nd reactor ruptures; radiation level spikes

TOKYO—Japan’s nuclear crisis intensified dramatically on Wednesday after authorities announced that a second reactor unit at the stricken Fukushima Dai-ichi Nuclear Power Station in northeastern Japan may have ruptured and appeared to be releasing radioactive steam.
The spike in radiation level above the nuclear plant prompted the defense ministry to put off a highly unusual plan to dump water from military helicopters to lower temperatures in an overheating pool containing spent fuel rods.
The vessel that possibly ruptured had been seen as the last fully intact line of defense against large-scale releases of radioactive material from one of the stricken reactors, but it was not clear how serious the possible breach might be.
The implications of overheating in the fuel rod pool at Dai-ichi’s No. 3 reactor also seemed perilous.
The developments were the latest in Japan’s swirling tragedy since an earthquake and tsunami struck the country with unbridled ferocity on Friday, leaving more than 11,000 people officially listed as dead or missing. Up to 450,000 people are staying in temporary shelters.
In a token of the mood of profound apprehension, Emperor Akihito told the nation on Wednesday: “We don’t know the number of victims, but I pray that every single person can be saved.”

Helicopter arrives
The plan to dump water from big, twin-rotor CH-47 helicopters—a tactic normally employed to combat forest fires—came after the company operating the reactors withdrew most of its workers from the plant on Tuesday, leaving only a skeleton crew of 50 struggling to lower temperatures.
When those workers were forced to suspend cooling operations, the spent fuel rod pool began heating up dangerously.
A helicopter was seen in television footage circling the plant, but then dumped its water some way off. Earlier, Japanese broadcasters showed live footage of thick plumes of steam rising above the nuclear plant.
Chief Cabinet Secretary Yukio Edano said the government believed the steam was coming from the No. 3 reactor where an explosion on Monday blew out part of the building surrounding the containment vessel.
The reactor has three layers of protection—the building; containment vessel, and metal cladding around fuel rods, which are inside the reactor. Those rods at the No. 3 reactor were likely already damaged.
A surge in radiation levels at the plant as the steam was rising forced some of the relatively few workers left at the plant to retreat indoors, suspending some critical efforts to pump water into several reactors to keep them cool.

Confusing reports
Earlier on Wednesday morning, Tokyo Electric Power Co. that runs the plant reported that a fire was burning at a different reactor, just hours after officials said flames that erupted on Tuesday had been doused.
A government official at Japan’s nuclear regulatory agency soon after said that flames and smoke were no longer visible, but he cautioned that it was unclear if the fire, at the building housing the No. 4 reactor, had died out. He also was not clear if it was a new fire or if the fire on Tuesday had never gone out.
There are a total of six reactors at the plant.
The developments are troubling reminders of the difficulties that Tokyo Electric is having in bringing under control the nuclear plant, which has suffered multiple explosions since Saturday.
And the confusion is emblematic of days of often contradictory reports about what is happening at the plant.
Tokyo Electric says it cannot know for sure what is happening in many cases because it is too dangerous for workers to get close to some reactors.
The situation became especially dire on Tuesday, when releases of radiation led the company to pull most of its workers from the plant.

Pools of spent rods
Among the main concerns of authorities are pools for spent fuel rods at several reactors at the plant, including the No. 4 reactor, where the pool has lost some of the water needed to keep the fuel rods stable. The rods are still radioactive and potentially as hot and dangerous as the fuel rods inside the reactors.
Tuesday’s explosion was caused by hydrogen gas bubbling up from chemical reactions set off by the fuel rods in the pool, Japanese officials said. Inspectors from the US Nuclear Regulatory Commission said they had been told by Japanese authorities that what was burning was lubricating oil from machinery near the pool.
Concern remained high about the storage pools at the No. 5 and No. 6 reactors. None of those three reactors at the plant, 220 kilometers northeast of Tokyo, were operating on Friday afternoon when an offshore earthquake with a magnitude now estimated at 9.0 shook the site. A tsunami rolled into the northeast Japanese coastline minutes later, swamping the plant.
At least 750 workers were evacuated on Tuesday morning after a separate explosion ruptured the inner containment building at the No. 2 reactor of the Dai-ichi plant, which was crippled by Friday’s earthquake and tsunami.

Surge of radiation
The closely spaced but apparently coincidental explosions at the No. 2 and No. 4 reactors together released a surge of radiation 800 times as intense as the recommended hourly exposure limit in Japan.
But 50 workers stayed behind. Taking shelter when possible in the reactor’s control room, which is heavily shielded from radiation, they struggled through the morning and afternoon to keep hundreds of gallons of seawater a minute flowing through temporary fire pumps into the stricken No. 1, No. 2 and No. 3 reactors, where overheated fuel rods continued to boil away the water at a brisk pace.
By early afternoon radiation levels had plunged. Workers were able to release surges of radiation each time they bled radioactive steam from the troubled reactors in an attempt to manage the pressure inside them, but the reactors were not yet releasing high levels of radiation on a sustained basis.
Late Tuesday morning, Prime Minister Naoto Kan warned in a nationally televised address of rising radiation. The government urged people living within 30 kilometers of the Dai-ichi plant to take precautions.
The sudden turn of events, after Monday’s explosion at one reactor and then Tuesday morning’s explosion on at yet another reactor—the third in four days at the plant—had already made the crisis at the Dai-ichi plant the worst nuclear accident since the 1986 Chernobyl disaster.
It had become impossible for workers to remain at many areas within the nuclear power plant for extended periods.

Alarming explosion
The explosion at the No. 2 reactor on Tuesday morning alarmed Japanese officials and nuclear power experts around the world because it was the first detonation at the plant that appeared to occur inside one of the primary containment vessels.
Those buildings are fortress-like structures of steel and reinforced concrete, designed to absorb the impact of a plane crash and minimize radiation leaks.
After a series of conflicting reports about how much damage the reactor had sustained after that blast, Edano acknowledged there was “a very high probability that a portion of the containment vessel was damaged.”
Japanese officials subsequently said that the explosion had damaged a doughnut-shaped steel container of water that surrounds the base of the reactor vessel inside the primary containment building. Reports from New York Times News Service and Associated Press