Tokyo (CNN) -- Spent fuel rods containing radioactive material may have burned in Tuesday's fire at the Fukushima Daiichi nuclear plant -- causing a spike in radiation levels, the plant's owner said.
The blaze started Tuesday morning but was later extinguished, Tokyo Electric Power Company said. It was unclear how much radioactive material may have been emitted, or what kind of health threat that could pose.
Chief Cabinet Secretary Yukio Edano said Tuesday afternoon that radiation readings at the plant's front gate had returned to a level that would not cause "harm to human health."
Japanese officials earlier told the International Atomic Energy Agency that radioactivity was "being released directly into the atmosphere" during the fire, according to a statement from the UN watchdog organization.
High temperatures inside the building that houses the plant's No. 4 reactor may have caused fuel rods sitting in a pool to ignite or explode, the plant's owner said.
By Tuesday afternoon, Edano said radiation readings -- which had reached dangerously high levels at the plant earlier -- had decreased.
"We have to monitor the situation closely, but the high concentration of radioactive material is not emitting constantly from the No. 4 reactor right now," he said.
Edano said readings at the gate at 3:30 p.m. Tuesday (2:30 am. ET) were 596.4 microsieverts per hour -- compared to a high reading of 11,930 microsieverts per hour at 9 a.m (8 p.m. ET Monday).
Analysts also have their eyes on reactors No. 5 and 6 at the plant, Edano said, where cooling systems were "not functioning well" and the temperature had dropped slightly Tuesday.
Earlier Tuesday, for the first time since Friday's quake crippled cooling systems at three of the plant's reactors, Edano said radiation levels at the plant had increased to "levels that can impact human health."
The plant's owners evacuated all but about 50 workers from the facility. Anyone within 30 kilometers (18.6 miles) of the plant were urged to remain indoors.
And the government imposed a no-fly zone over the 30-kilometer radius "because of detected radiation after explosions" there, the country's transportation ministry said.
Edano said levels at the plant were between 100 and 400 millisieverts, or as much as 160 times higher than the average dose of radiation a typical person receives from natural sources in a year. A microsievert is an internationally recognized unit measuring radiation dosage, with people typically exposed during an entire year to a total of about 1,000 microsieverts.
"Radiation has come out from these reactors and the reading of the levels seems very high. There is still a very high risk of further radioactive material coming out," Prime Minister Naoto Kan said, asking people to remain calm.
The officials briefed reporters several hours after an explosion at the No. 2 reactor -- the third blast at the plant in four days. As they spoke, firefighters were battling the blaze at the No. 4 reactor.
The extent of damage at the troubled plant remained unclear.
The announcement from officials Tuesday "points to something different, something more serious" after the explosion at the No. 2 reactor, CNN analyst James Walsh said. "But we don't have the definitive evidence yet."
Edano said earlier that he could not rule out the possibility of a meltdown at all three troubled reactors at the plant.
If fuel rods inside the reactors are melting, Walsh said a key detail is whether the melted material stays inside the reactor.
"The Japanese plants and all modern plants have a containment vessel. Essentially the reactor is inside of a vault. And that vault is made of thick concrete and steel," Walsh said. "The million-dollar question is whether that melting will be contained... We'll know within 24 hours. That's the key thing people should be paying attention to."
There are six reactors at Fukushima Daiichi, located in northeastern Japan about 40 miles (65 kilometers) south of Sendai, one of the areas worst hit by Friday's 9.0-magnitude earthquake and the resulting tsunami.
Workers have been scrambling to stave off a meltdown as a series of significant problems popped up at the plant since Friday:
-- The earthquake and tsunami Friday knocked out regular and backup cooling systems at the plant's No. 1 and No. 3 reactors. Workers began injecting seawater and boron into the reactors in what experts have called a last-ditch attempt to prevent a meltdown after the cooling systems failed.
-- A blast caused by hydrogen buildup Saturday blew the roof off the No. 1 reactor's containment structure and injured four workers.
-- An explosion Monday caused by hydrogen buildup blew away the roof and walls of the building housing the plant's No. 3 reactor and injured 11 people. The plant's No. 2 reactor lost its cooling capabilities Monday afternoon after the explosion, and workers began injecting seawater and boron into that reactor.
-- An explosion hit the No. 2 reactor Tuesday morning. Readings indicate some damage to the No. 2 reactor's suppression pool, a donut-shaped reservoir at the base of the reactor's containment vessel.
-- A fire ignited in the No. 4 reactor building later Tuesday.
The government has evacuated more than 200,000 residents from homes within a 20-kilometer (12.4-mile) radius of the plant and tested 160 people for radiation exposure, authorities said Sunday.
If the effort to cool the nuclear fuel inside the reactor fails completely -- a scenario that experts who have spoken to CNN say is unlikely -- the resulting release of radiation could cause enormous damage to the plant, and possibly release radiation into the atmosphere or water. That could lead to widespread cancer and other health problems, experts say.
Concerns about the risk of radiation release spread as the situation at the plant appeared to worsen Tuesday.
U.S. Navy personnel began limiting outdoor activities and securing external ventilation systems after instruments aboard an aircraft carrier docked in Japan detected low levels of radioactivity from the Fukushima Daiichi nuclear plant, the Navy said.
The USS George Washington was docked for maintenance in Yokosuka, about 175 miles (280 kilometers) from the plant, when instruments detected the radiation at 7 a.m. Tuesday (6 p.m. ET Monday), the Navy said in a statement.
"These measures are strictly precautionary in nature. We do not expect that any United States federal radiation exposure limits will be exceeded even if no precautionary measures are taken," the Navy said.
Radiation levels in Tokyo were twice the usual level on Tuesday but was too negligible to pose a health threat -- 0.809 microsieverts per hour, the Tokyo Metropolitan Government said.
http://edition.cnn.com/2011/WORLD/asiapcf/03/15/japan.nuclear.reactors/index.html
The blaze started Tuesday morning but was later extinguished, Tokyo Electric Power Company said. It was unclear how much radioactive material may have been emitted, or what kind of health threat that could pose.
Chief Cabinet Secretary Yukio Edano said Tuesday afternoon that radiation readings at the plant's front gate had returned to a level that would not cause "harm to human health."
Japanese officials earlier told the International Atomic Energy Agency that radioactivity was "being released directly into the atmosphere" during the fire, according to a statement from the UN watchdog organization.
High temperatures inside the building that houses the plant's No. 4 reactor may have caused fuel rods sitting in a pool to ignite or explode, the plant's owner said.
By Tuesday afternoon, Edano said radiation readings -- which had reached dangerously high levels at the plant earlier -- had decreased.
"We have to monitor the situation closely, but the high concentration of radioactive material is not emitting constantly from the No. 4 reactor right now," he said.
Edano said readings at the gate at 3:30 p.m. Tuesday (2:30 am. ET) were 596.4 microsieverts per hour -- compared to a high reading of 11,930 microsieverts per hour at 9 a.m (8 p.m. ET Monday).
Analysts also have their eyes on reactors No. 5 and 6 at the plant, Edano said, where cooling systems were "not functioning well" and the temperature had dropped slightly Tuesday.
Earlier Tuesday, for the first time since Friday's quake crippled cooling systems at three of the plant's reactors, Edano said radiation levels at the plant had increased to "levels that can impact human health."
The plant's owners evacuated all but about 50 workers from the facility. Anyone within 30 kilometers (18.6 miles) of the plant were urged to remain indoors.
And the government imposed a no-fly zone over the 30-kilometer radius "because of detected radiation after explosions" there, the country's transportation ministry said.
Edano said levels at the plant were between 100 and 400 millisieverts, or as much as 160 times higher than the average dose of radiation a typical person receives from natural sources in a year. A microsievert is an internationally recognized unit measuring radiation dosage, with people typically exposed during an entire year to a total of about 1,000 microsieverts.
"Radiation has come out from these reactors and the reading of the levels seems very high. There is still a very high risk of further radioactive material coming out," Prime Minister Naoto Kan said, asking people to remain calm.
The officials briefed reporters several hours after an explosion at the No. 2 reactor -- the third blast at the plant in four days. As they spoke, firefighters were battling the blaze at the No. 4 reactor.
The extent of damage at the troubled plant remained unclear.
The announcement from officials Tuesday "points to something different, something more serious" after the explosion at the No. 2 reactor, CNN analyst James Walsh said. "But we don't have the definitive evidence yet."
Edano said earlier that he could not rule out the possibility of a meltdown at all three troubled reactors at the plant.
If fuel rods inside the reactors are melting, Walsh said a key detail is whether the melted material stays inside the reactor.
"The Japanese plants and all modern plants have a containment vessel. Essentially the reactor is inside of a vault. And that vault is made of thick concrete and steel," Walsh said. "The million-dollar question is whether that melting will be contained... We'll know within 24 hours. That's the key thing people should be paying attention to."
There are six reactors at Fukushima Daiichi, located in northeastern Japan about 40 miles (65 kilometers) south of Sendai, one of the areas worst hit by Friday's 9.0-magnitude earthquake and the resulting tsunami.
Workers have been scrambling to stave off a meltdown as a series of significant problems popped up at the plant since Friday:
-- The earthquake and tsunami Friday knocked out regular and backup cooling systems at the plant's No. 1 and No. 3 reactors. Workers began injecting seawater and boron into the reactors in what experts have called a last-ditch attempt to prevent a meltdown after the cooling systems failed.
-- A blast caused by hydrogen buildup Saturday blew the roof off the No. 1 reactor's containment structure and injured four workers.
-- An explosion Monday caused by hydrogen buildup blew away the roof and walls of the building housing the plant's No. 3 reactor and injured 11 people. The plant's No. 2 reactor lost its cooling capabilities Monday afternoon after the explosion, and workers began injecting seawater and boron into that reactor.
-- An explosion hit the No. 2 reactor Tuesday morning. Readings indicate some damage to the No. 2 reactor's suppression pool, a donut-shaped reservoir at the base of the reactor's containment vessel.
-- A fire ignited in the No. 4 reactor building later Tuesday.
The government has evacuated more than 200,000 residents from homes within a 20-kilometer (12.4-mile) radius of the plant and tested 160 people for radiation exposure, authorities said Sunday.
If the effort to cool the nuclear fuel inside the reactor fails completely -- a scenario that experts who have spoken to CNN say is unlikely -- the resulting release of radiation could cause enormous damage to the plant, and possibly release radiation into the atmosphere or water. That could lead to widespread cancer and other health problems, experts say.
Concerns about the risk of radiation release spread as the situation at the plant appeared to worsen Tuesday.
U.S. Navy personnel began limiting outdoor activities and securing external ventilation systems after instruments aboard an aircraft carrier docked in Japan detected low levels of radioactivity from the Fukushima Daiichi nuclear plant, the Navy said.
The USS George Washington was docked for maintenance in Yokosuka, about 175 miles (280 kilometers) from the plant, when instruments detected the radiation at 7 a.m. Tuesday (6 p.m. ET Monday), the Navy said in a statement.
"These measures are strictly precautionary in nature. We do not expect that any United States federal radiation exposure limits will be exceeded even if no precautionary measures are taken," the Navy said.
Radiation levels in Tokyo were twice the usual level on Tuesday but was too negligible to pose a health threat -- 0.809 microsieverts per hour, the Tokyo Metropolitan Government said.
http://edition.cnn.com/2011/WORLD/asiapcf/03/15/japan.nuclear.reactors/index.html
Comments