ID :
176246
Mon, 04/18/2011 - 17:29
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https://oananews.org//node/176246
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Radiation inside Nos. 1, 3 reactor buildings up to 57 millisieverts
TOKYO, April 18 Kyodo - The radiation level inside the Nos. 1 and 3 reactor buildings at the crippled Fukushima Daiichi nuclear power plant was up to about 57 millisieverts per hour as of Sunday, the government's nuclear safety agency said Monday, acknowledging that it is a level that puts time constraints on any restoration work that must be done there.
The Nuclear and Industrial Safety Agency also said that it has found the No. 4 reactor building flooded with water 5 meters high, besides some 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 roadmap that it plans to pour water into their 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 stay 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 that it was seeking ways to mitigate radiation exposure.
On Sunday, two remote-controlled robots provided by U.S. company iRobot Corp. opened the double doors that lead 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 tests by the robots, up to 270 millisieverts per hour were detected near the door to the No. 1 reactor building.
Nishiyama said that the areas the robots and the workers checked were different areas.
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.
Meanwhile, Tokyo Electric said that ''there is a possibility that fuel rods stored in the No. 2 unit's spent fuel tank are damaged'' based on its analysis of water that has spilled out from the tank.
The Nuclear and Industrial Safety Agency also said that it has found the No. 4 reactor building flooded with water 5 meters high, besides some 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 roadmap that it plans to pour water into their 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 stay 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 that it was seeking ways to mitigate radiation exposure.
On Sunday, two remote-controlled robots provided by U.S. company iRobot Corp. opened the double doors that lead 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 tests by the robots, up to 270 millisieverts per hour were detected near the door to the No. 1 reactor building.
Nishiyama said that the areas the robots and the workers checked were different areas.
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.
Meanwhile, Tokyo Electric said that ''there is a possibility that fuel rods stored in the No. 2 unit's spent fuel tank are damaged'' based on its analysis of water that has spilled out from the tank.
