ID :
176281
Mon, 04/18/2011 - 19:33
Auther :
Shortlink :
https://oananews.org//node/176281
The shortlink copeid
UPDATE1: Radiation inside Nos. 1, 3 reactor buildings up to 57 millisieverts
TOKYO, April 19 Kyodo -
(EDS: ADDING INFO IN LAST SEVEN GRAFS)
The radiation levels inside the Nos. 1 and 3 reactor buildings at the crippled Fukushima Daiichi nuclear power plant were up to about 57 millisieverts per hour as of Sunday, the government's nuclear safety agency said Monday, acknowledging that such a level imposes time constraints on restoration work that must be conducted there.
The Nuclear and Industrial Safety Agency also said it has found that the No. 4 reactor building has been flooded with water 5 meters high, besides around 60,000 tons of contaminated water already found to be filling up the Nos. 1 to 3 reactor turbine buildings and nearby areas.
Many of the pools of water containing radioactive substances are believed to be a side effect of an emergency measure of pouring massive amounts of water into the reactors and their spent nuclear fuel pools from outside to keep them cool, given that they have lost their key cooling functions following the March 11 earthquake and tsunami.
Hidehiko Nishiyama, the agency's spokesman, said that the priority level of dealing with the water at the No. 4 reactor building is low because the No. 4 unit has all its fuel stored in the spent fuel pool and workers must first try to stabilize the situation at the crippled Nos. 1 to 3 reactors.
As part of efforts to cool the three reactors stably, plant operator Tokyo Electric Power Co. said Sunday in its restoration road map that it plans to pour water into their primary reactor containment vessels within roughly three months.
Nishiyama said that the installation of an air-cooling device to take the heat from the water circulating around the reactor is under consideration for the Nos. 1 and 3 reactors.
But work to restore the cooling functions does not appear to be easy.
According to the data obtained by remote-controlled robots and made available Monday, the radiation level at the No. 1 reactor building was between about 10 and 49 millisieverts per hour, while at the No. 3 reactor building it was between 28 and 57 millisieverts per hour.
If workers were to remain in the 57-millisievert-environment for four and a half hours, they would be exposed to more than the permissible level of 250 millisieverts in dealing with the ongoing crisis, the worst Japan has seen.
Tokyo Electric said that usually the radiation level inside reactor buildings is 0.01 millisievert per hour under normal conditions.
Nishiyama told a press conference in the morning that the level made it ''tough'' for workers to engage in restoration for prolonged periods, and the agency was seeking ways to mitigate radiation exposure.
On Sunday, two remote-controlled robots provided by U.S. company iRobot Corp. opened the double doors leading into the reactor buildings and measured radiation levels, temperatures and other data to check whether workers could safely engage in restoration work there.
As for the radiation level measured by workers on Saturday prior to the readings by the robots, up to 270 millisieverts per hour was detected near the door to the No. 1 reactor building.
Nishiyama said that the areas the robots and the workers checked were different.
The robots, called PackBot, also checked the No. 2 reactor building Monday, where highly radioactive water was found to be flooding the adjacent No. 2 reactor turbine building and an underground tunnel-like trench connected to it.
The water in and around the No. 2 reactor turbine building is believed to contain higher concentrations of radioactive substances than other contaminated water found at the site, and is believed to originate from the No. 2 reactor's core, where fuel rods have partially melted.
Tokyo Electric announced Monday that it had detected a high level of radioactive substances in water that has spilled out from the No. 2 unit's spent nuclear fuel pool.
The utility firm said that there is a possibility that the spent fuel rods may have been damaged. Officials of the nuclear agency said they could not deny such a possibility, but noted that it is more likely to be linked to the damaged No. 2 reactor core.
According to TEPCO, cesium-134 at a concentration level of 160,000 becquerels per cubic centimeter, cesium-137 at a level of 150,000 becquerels and iodine-131 at a level of 4,100 becquerels were detected from the water sample taken Saturday.
Usually such radioactive substances are hardly detected in such spilled water, which flows into separate tanks located near the spent fuel pool.
Meanwhile, the nuclear safety agency acknowledged in a report to a government panel that ''fuel pellets'' in the Nos. 1 to 3 reactors have melted, although it cannot tell to what extent.
The agency has already acknowledged that nuclear fuel has been damaged, but it is the first time it has referred to the details.
Fuel rods are zirconium metal tubes containing pellets, which serve as the actual fuel for nuclear reactors, and assemblies of fuel rods are loaded into reactor cores.
(EDS: ADDING INFO IN LAST SEVEN GRAFS)
The radiation levels inside the Nos. 1 and 3 reactor buildings at the crippled Fukushima Daiichi nuclear power plant were up to about 57 millisieverts per hour as of Sunday, the government's nuclear safety agency said Monday, acknowledging that such a level imposes time constraints on restoration work that must be conducted there.
The Nuclear and Industrial Safety Agency also said it has found that the No. 4 reactor building has been flooded with water 5 meters high, besides around 60,000 tons of contaminated water already found to be filling up the Nos. 1 to 3 reactor turbine buildings and nearby areas.
Many of the pools of water containing radioactive substances are believed to be a side effect of an emergency measure of pouring massive amounts of water into the reactors and their spent nuclear fuel pools from outside to keep them cool, given that they have lost their key cooling functions following the March 11 earthquake and tsunami.
Hidehiko Nishiyama, the agency's spokesman, said that the priority level of dealing with the water at the No. 4 reactor building is low because the No. 4 unit has all its fuel stored in the spent fuel pool and workers must first try to stabilize the situation at the crippled Nos. 1 to 3 reactors.
As part of efforts to cool the three reactors stably, plant operator Tokyo Electric Power Co. said Sunday in its restoration road map that it plans to pour water into their primary reactor containment vessels within roughly three months.
Nishiyama said that the installation of an air-cooling device to take the heat from the water circulating around the reactor is under consideration for the Nos. 1 and 3 reactors.
But work to restore the cooling functions does not appear to be easy.
According to the data obtained by remote-controlled robots and made available Monday, the radiation level at the No. 1 reactor building was between about 10 and 49 millisieverts per hour, while at the No. 3 reactor building it was between 28 and 57 millisieverts per hour.
If workers were to remain in the 57-millisievert-environment for four and a half hours, they would be exposed to more than the permissible level of 250 millisieverts in dealing with the ongoing crisis, the worst Japan has seen.
Tokyo Electric said that usually the radiation level inside reactor buildings is 0.01 millisievert per hour under normal conditions.
Nishiyama told a press conference in the morning that the level made it ''tough'' for workers to engage in restoration for prolonged periods, and the agency was seeking ways to mitigate radiation exposure.
On Sunday, two remote-controlled robots provided by U.S. company iRobot Corp. opened the double doors leading into the reactor buildings and measured radiation levels, temperatures and other data to check whether workers could safely engage in restoration work there.
As for the radiation level measured by workers on Saturday prior to the readings by the robots, up to 270 millisieverts per hour was detected near the door to the No. 1 reactor building.
Nishiyama said that the areas the robots and the workers checked were different.
The robots, called PackBot, also checked the No. 2 reactor building Monday, where highly radioactive water was found to be flooding the adjacent No. 2 reactor turbine building and an underground tunnel-like trench connected to it.
The water in and around the No. 2 reactor turbine building is believed to contain higher concentrations of radioactive substances than other contaminated water found at the site, and is believed to originate from the No. 2 reactor's core, where fuel rods have partially melted.
Tokyo Electric announced Monday that it had detected a high level of radioactive substances in water that has spilled out from the No. 2 unit's spent nuclear fuel pool.
The utility firm said that there is a possibility that the spent fuel rods may have been damaged. Officials of the nuclear agency said they could not deny such a possibility, but noted that it is more likely to be linked to the damaged No. 2 reactor core.
According to TEPCO, cesium-134 at a concentration level of 160,000 becquerels per cubic centimeter, cesium-137 at a level of 150,000 becquerels and iodine-131 at a level of 4,100 becquerels were detected from the water sample taken Saturday.
Usually such radioactive substances are hardly detected in such spilled water, which flows into separate tanks located near the spent fuel pool.
Meanwhile, the nuclear safety agency acknowledged in a report to a government panel that ''fuel pellets'' in the Nos. 1 to 3 reactors have melted, although it cannot tell to what extent.
The agency has already acknowledged that nuclear fuel has been damaged, but it is the first time it has referred to the details.
Fuel rods are zirconium metal tubes containing pellets, which serve as the actual fuel for nuclear reactors, and assemblies of fuel rods are loaded into reactor cores.
