ID :
169525
Sun, 03/20/2011 - 18:28
Auther :
Shortlink :
https://oananews.org//node/169525
The shortlink copeid
Tension remains in Fukushima plant, electricity partially installed+
TOKYO, March 20 Kyodo -
Japan's quake-hit Fukushima Daiichi nuclear power plant saw a stable source of electricity finally reach one of its crippled nuclear reactor building Sunday, a key step to move ahead in restoring the reactors cooling functions to avoid the disaster from worsening further.
While the government said the ongoing operation to cool down the overheating spent fuel pools at the No. 3 and No. 4 reactor buildings are showing ''some progress,'' the rise in pressure in the No. 3 reactor's containment vessel at one point highlighted that authorities are walking on thin ice in dealing with the disaster.
''There would be twists and turns even if the process to maintain the status quo and to improve the situation for the better goes smoothly,'' Chief Cabinet Secretary Yukio Edano told a press conference in the afternoon, while indicating that the battered nuclear plant is doomed to be scrapped.
According to the plant operator Tokyo Electric Power Co., external power was restored at 3:46 p.m. to the No. 2 reactor's unit. The company has said it will start trying to restore the system to monitor radiation and other data, light the control room and cool down the reactor and the reactor's spent-fuel storage pool.
Along with the work to restore electricity, the Self-Defense Forces, fire fighters and others continued to engage in the imminent task of cooling the overheating spent fuel pools by throwing thousands of tons of water into the No. 3 and No. 4 reactor buildings. The operation is possible because apparent hydrogen explosions blasted the roofs and walls of the buildings.
In the morning, the Ground Self-Defense Force shot water at the No. 4 unit spent fuel pool for the first time, with the amount of water totaling about 80 tons for nearly one hour. The work resumed from 6:20 p.m., according to the Defense Ministry.
The ministry also plans to mobilize two GSDF tanks to remove the rubble at the plant, which is hampering the water-spraying efforts.
The move came after the Tokyo Fire Department shot water into a spent-fuel storage pool at the No. 3 reactor in an overnight operation that lasted more than 13 hours until 3:40 a.m.
Cooling the spent fuel tank of the No. 3 reactor building took precedence because smoke was detected from the unit Wednesday, indicating that the pool situated outside the containment vessel may be boiling.
A rise in water temperature, usually to 40 C, causes the water level to fall, thus exposing the spent nuclear fuel rods, which could then heat up further, melt and discharge highly radioactive materials in the worst-case scenario, experts say.
More than 2,000 tons of water is believed to have been put into the No. 3 reactor pool, exceeding the pool's capacity of 1,400 tons. Fuel rods used at the reactor were plutonium-uranium mixed oxide fuel, known as MOX, said to be harder to control than normal fuel rods made from uranium.
On the No. 3 reactor, the government's nuclear safety agency said the pressure in its containment vessel was found to be rising in the morning and there is a need to take steps to address the issue. But Tokyo Electric later said it would not immediately take the measure because the pressure has stabilized.
The process of reducing the pressure by releasing steam from the vessel may mean that radioactive steam could be further released outside. The measures have already been taken for some of the troubled reactors.
As of 11:00 a.m., Tokyo Electric said the radiation level about 0.5 kilometer northwest from the No. 2 reactor dropped to 2,579 microsievert per hour, compared to 3,443 microsievert per hour at 2 p.m. Saturday.
International Atomic Energy Agency chief Yukiya Amano, who returned to Vienna after a two-day visit to Japan, indicated to reporters on Saturday that it was premature to be optimistic about the future of the troubled plant.
''I hope that safety, stability will be recovered as soon as possible...But I still don't think it is time to say that I think they are going in a good direction or not,'' he said in Vienna.
The power plant which was hit hard by the March 11 magnitude 9.0 earthquake is on the Pacific coast of Fukushima Prefecture about 220 kilometers northeast of Tokyo.
The No. 1, No. 2 and No. 3 reactors, which were operating at the time of the quake, automatically halted but lost their key reactor cooling functions because the quake and the ensuing massive tsunami cut off electricity to the plant.
Their reactor cores are believed to have partially melted and sea water has been pumped into them to prevent the fuel from being exposed.
The remaining No. 4, No. 5, and No. 6 units were under maintenance at the time of the earthquake, but No. 4 is different in that all the fuel was not in the reactor core but was in the spent fuel pool.
The No. 5 and 6 units have been relatively less troubled than the others, and their situation appears to be improving as backup power sources were restored.
Japan's quake-hit Fukushima Daiichi nuclear power plant saw a stable source of electricity finally reach one of its crippled nuclear reactor building Sunday, a key step to move ahead in restoring the reactors cooling functions to avoid the disaster from worsening further.
While the government said the ongoing operation to cool down the overheating spent fuel pools at the No. 3 and No. 4 reactor buildings are showing ''some progress,'' the rise in pressure in the No. 3 reactor's containment vessel at one point highlighted that authorities are walking on thin ice in dealing with the disaster.
''There would be twists and turns even if the process to maintain the status quo and to improve the situation for the better goes smoothly,'' Chief Cabinet Secretary Yukio Edano told a press conference in the afternoon, while indicating that the battered nuclear plant is doomed to be scrapped.
According to the plant operator Tokyo Electric Power Co., external power was restored at 3:46 p.m. to the No. 2 reactor's unit. The company has said it will start trying to restore the system to monitor radiation and other data, light the control room and cool down the reactor and the reactor's spent-fuel storage pool.
Along with the work to restore electricity, the Self-Defense Forces, fire fighters and others continued to engage in the imminent task of cooling the overheating spent fuel pools by throwing thousands of tons of water into the No. 3 and No. 4 reactor buildings. The operation is possible because apparent hydrogen explosions blasted the roofs and walls of the buildings.
In the morning, the Ground Self-Defense Force shot water at the No. 4 unit spent fuel pool for the first time, with the amount of water totaling about 80 tons for nearly one hour. The work resumed from 6:20 p.m., according to the Defense Ministry.
The ministry also plans to mobilize two GSDF tanks to remove the rubble at the plant, which is hampering the water-spraying efforts.
The move came after the Tokyo Fire Department shot water into a spent-fuel storage pool at the No. 3 reactor in an overnight operation that lasted more than 13 hours until 3:40 a.m.
Cooling the spent fuel tank of the No. 3 reactor building took precedence because smoke was detected from the unit Wednesday, indicating that the pool situated outside the containment vessel may be boiling.
A rise in water temperature, usually to 40 C, causes the water level to fall, thus exposing the spent nuclear fuel rods, which could then heat up further, melt and discharge highly radioactive materials in the worst-case scenario, experts say.
More than 2,000 tons of water is believed to have been put into the No. 3 reactor pool, exceeding the pool's capacity of 1,400 tons. Fuel rods used at the reactor were plutonium-uranium mixed oxide fuel, known as MOX, said to be harder to control than normal fuel rods made from uranium.
On the No. 3 reactor, the government's nuclear safety agency said the pressure in its containment vessel was found to be rising in the morning and there is a need to take steps to address the issue. But Tokyo Electric later said it would not immediately take the measure because the pressure has stabilized.
The process of reducing the pressure by releasing steam from the vessel may mean that radioactive steam could be further released outside. The measures have already been taken for some of the troubled reactors.
As of 11:00 a.m., Tokyo Electric said the radiation level about 0.5 kilometer northwest from the No. 2 reactor dropped to 2,579 microsievert per hour, compared to 3,443 microsievert per hour at 2 p.m. Saturday.
International Atomic Energy Agency chief Yukiya Amano, who returned to Vienna after a two-day visit to Japan, indicated to reporters on Saturday that it was premature to be optimistic about the future of the troubled plant.
''I hope that safety, stability will be recovered as soon as possible...But I still don't think it is time to say that I think they are going in a good direction or not,'' he said in Vienna.
The power plant which was hit hard by the March 11 magnitude 9.0 earthquake is on the Pacific coast of Fukushima Prefecture about 220 kilometers northeast of Tokyo.
The No. 1, No. 2 and No. 3 reactors, which were operating at the time of the quake, automatically halted but lost their key reactor cooling functions because the quake and the ensuing massive tsunami cut off electricity to the plant.
Their reactor cores are believed to have partially melted and sea water has been pumped into them to prevent the fuel from being exposed.
The remaining No. 4, No. 5, and No. 6 units were under maintenance at the time of the earthquake, but No. 4 is different in that all the fuel was not in the reactor core but was in the spent fuel pool.
The No. 5 and 6 units have been relatively less troubled than the others, and their situation appears to be improving as backup power sources were restored.
