Editor's note: We will update our earthquake news as frequently as possible on AJW's Facebook page: http://www.facebook.com/AJW.Asahi. Please check the latest developments in this disaster. From Toshio Jo, managing editor, International Division, The Asahi Shimbun.
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Three technicians who were exposed to high levels of radiation while battling to restore electrical power to the crippled No. 3 reactor of the Fukushima nuclear power plant likely came into contact with substances resulting from damage to fuel rods in the reactor core.
Officials of the Nuclear and Industrial Safety Agency (NISA) also said Friday that similar high levels of radiation have been detected in the water-sodden floors of the turbine buildings for the No. 1 and No. 2 reactors.
The radiation found in the water has forced Tokyo Electric Power Co., the plant operator, to call a halt to efforts to install electrical cables to the reactors. That could mean further delays in restoring an outside power source to the reactors.
Two of the three workers likely were exposed to between two and six sieverts of radiation because their feet came into contact with radioactive water, according to officials at the National Institute of Radiological Sciences in Chiba, where the three workers were taken for observation Friday.
If symptoms similar to burns appear in the next 10 days or so, the workers will have to undergo specialist medical treatment, the officials said.
According to NISA and TEPCO officials, the three workers exposed to radiation were installing cables in the turbine building for the No. 3 reactor when their feet became wet. The water had radiation levels about 10,000 times higher than coolant in the reactor core.
NISA officials said there was a higher possibility that the water leaked out of the reactor core rather than the storage pool containing spent fuel rods.
The water contained traces of cesium-137. This suggests there is damage in the fuel rods.
Because the core is maintained at a higher pressure than its surroundings, there is likely no major damage to the core pressure container. NISA officials said the radioactive water likely was steam or water that leaked from damaged pipes.
Not only was the core building of the No. 3 reactor damaged during the March 11 Great East Japan Earthquake, but also by a hydrogen explosion on March 14. The force from the quake and explosion may have ruptured pipes and valves through which coolant and steam from the core pressure container have to pass.
The water that leaked from those damaged pipes and valves may have accumulated in the basement of the turbine building.
The building housing the core is situated next to the turbine building. While the basement where the three workers were exposed to radiation is not directly connected to the core building, workers can move between the two buildings from the first floor.
Puddles of water have also been found in the turbine buildings for the No. 1 and No. 2 reactors.
A water sample taken Thursday from the basement of the turbine building for the No. 1 reactor was found to have 3.8 million becquerels of radiation per cubic centimeter, about the same level as the radiation found in the No. 3 reactor turbine building.
According to officials at the National Institute of Radiological Sciences, two of the workers are not displaying any overall health problems. Even so, they will be kept under observation for changes in their white blood cell count and skin condition.
Under the Industrial Safety and Health Law, the upper limit for radiation exposure on the skin during emergency work is one sievert.
This is the first time any worker involved in the Fukushima plant accident has been exposed to more than one sievert of radiation.
According to the International Commission on Radiological Protection, hair loss results when a limited part of the human body is exposed to three sieverts of radiation. Red spots appear when the skin is exposed to six sieverts.
TEPCO officials said Friday that they had switched to pumping fresh water instead of seawater in efforts to cool the No. 1 and No. 3 reactor cores.
The decision was made to prevent salt from damaging or blocking pipes and equipment near the core.
The same strategy was used for the No. 2 reactor and fresh water was pumped in from Saturday morning.
Lights in the central control room of the No. 2 reactor were also turned on Saturday afternoon, making it the third reactor to have lights.
* * *
Three technicians who were exposed to high levels of radiation while battling to restore electrical power to the crippled No. 3 reactor of the Fukushima nuclear power plant likely came into contact with substances resulting from damage to fuel rods in the reactor core.
Officials of the Nuclear and Industrial Safety Agency (NISA) also said Friday that similar high levels of radiation have been detected in the water-sodden floors of the turbine buildings for the No. 1 and No. 2 reactors.
The radiation found in the water has forced Tokyo Electric Power Co., the plant operator, to call a halt to efforts to install electrical cables to the reactors. That could mean further delays in restoring an outside power source to the reactors.
Two of the three workers likely were exposed to between two and six sieverts of radiation because their feet came into contact with radioactive water, according to officials at the National Institute of Radiological Sciences in Chiba, where the three workers were taken for observation Friday.
If symptoms similar to burns appear in the next 10 days or so, the workers will have to undergo specialist medical treatment, the officials said.
According to NISA and TEPCO officials, the three workers exposed to radiation were installing cables in the turbine building for the No. 3 reactor when their feet became wet. The water had radiation levels about 10,000 times higher than coolant in the reactor core.
NISA officials said there was a higher possibility that the water leaked out of the reactor core rather than the storage pool containing spent fuel rods.
The water contained traces of cesium-137. This suggests there is damage in the fuel rods.
Because the core is maintained at a higher pressure than its surroundings, there is likely no major damage to the core pressure container. NISA officials said the radioactive water likely was steam or water that leaked from damaged pipes.
Not only was the core building of the No. 3 reactor damaged during the March 11 Great East Japan Earthquake, but also by a hydrogen explosion on March 14. The force from the quake and explosion may have ruptured pipes and valves through which coolant and steam from the core pressure container have to pass.
The water that leaked from those damaged pipes and valves may have accumulated in the basement of the turbine building.
The building housing the core is situated next to the turbine building. While the basement where the three workers were exposed to radiation is not directly connected to the core building, workers can move between the two buildings from the first floor.
Puddles of water have also been found in the turbine buildings for the No. 1 and No. 2 reactors.
A water sample taken Thursday from the basement of the turbine building for the No. 1 reactor was found to have 3.8 million becquerels of radiation per cubic centimeter, about the same level as the radiation found in the No. 3 reactor turbine building.
According to officials at the National Institute of Radiological Sciences, two of the workers are not displaying any overall health problems. Even so, they will be kept under observation for changes in their white blood cell count and skin condition.
Under the Industrial Safety and Health Law, the upper limit for radiation exposure on the skin during emergency work is one sievert.
This is the first time any worker involved in the Fukushima plant accident has been exposed to more than one sievert of radiation.
According to the International Commission on Radiological Protection, hair loss results when a limited part of the human body is exposed to three sieverts of radiation. Red spots appear when the skin is exposed to six sieverts.
TEPCO officials said Friday that they had switched to pumping fresh water instead of seawater in efforts to cool the No. 1 and No. 3 reactor cores.
The decision was made to prevent salt from damaging or blocking pipes and equipment near the core.
The same strategy was used for the No. 2 reactor and fresh water was pumped in from Saturday morning.
Lights in the central control room of the No. 2 reactor were also turned on Saturday afternoon, making it the third reactor to have lights.
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