Level 7 is the highest rank on the IAEA's International Nuclear and Radiological Event Scale and equivalent to the severity recorded after the Chernobyl disaster in 1986, which is the only other nuclear accident ever to have been rated a Level 7 event.
Hydrogen explosions March 12, 14 and 15 damaged the Fukushima Daiichi nuclear plant. (Photo courtesy TEPCO)
Level 7 is a Major Accident, defined as, "A major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures."
The agency told reporters at a news conference Tuesday that large amounts of radioactive substances that could affect human health and the environment are being released across a wide area around the nuclear plant located on the Pacific Ocean, 240 km (150 miles) north of Tokyo.
But the agency said the volume of radiation from Fukushima is one-tenth that at Chernobyl.
The nuclear safety agency said its calculations show that 370-thousand terabecquerels of radioactive iodine 131 and cesium 137 have been released from the plant.
Speaking at the news conference, officials from Japan's Nuclear Safety Commission put the estimated leak at 630-thousand terabecquerels of both substances.
One terabecquerel is equivalent to one trillion becquerels. Both organizations say the leak constitutes a level 7 crisis.
Fire broke out at a sampling building near a water outlet at Fukushima Daiichi's reactor Unit 4 but was soon extinguished. April 12, 2011 (Photo courtesy TEPCO)
Nuclear safety agency official Hidehiko Nishiyama pointed out that 29 people died of acute radiation exposure at Chernobyl but there are no fatal radiation casualties at Fukushima.
At Chernobyl the nuclear reactor itself exploded, he said, but the Fukushima plant was damaged by hydrogen explosions while the reactors themselves retain their structures.
Nishiyama said the upgrade to a "temporary assessment" of level 7 does not affect the existing evacuation plan to get people away from a 30 kilometer (20 mile) radius surrounding the power plant within the next 30 days. People have already been evacuated from a 20 km (12 mile) radius.
Masataka Shimizu, president of plant operator Tokyo Electric Power Company, said today in a statement, "We sincerely recognize" the maximum severity rating of level 7. "We deeply apologize for the public's distress and inconvenience at the surrounding areas of the power station, Fukushima Prefecture, and broader society," he said.
"In order to resolve the situation as soon as possible, we will proceed to cool the reactors and to prevent the diffusion of radioactive materials. In addition, we are considering various countermeasures and their processes," Shimizu said. "Cooperatively working with the national and local governments, we will concentrate all our resources to resolve this difficult situation."
Engineers remotely control cleanup machnery at TEPCO's Fukushima Daiichi nuclear plant, April 12, 2011. (Photo courtesy TEPCO)
The nuclear safety commission says much of the radiation was released during the two days after the reactor suppression pool connected to the Unit 2 reactor, began showing problems on the morning of March 15.
The commission said that radiation is still escaping and the amount is increasing, but that the volume has dropped since the crisis began.
Industry Minister Banri Kaieda told reporters the government will do all it can to quickly bring the Fukushima Daiichi nuclear power plant under control.
Tokyo Electric Power Co, the plant's operator, this evening began work to remove highly radioactive water after a delay due to a series of strong earthquakes on Monday and Tuesday that shook the Pacific coast of Honshu island where the plant is located.
The highly radioactive wastewater is being transferred from a tunnel outside the Unit 2 reactor to a turbine condenser.
The contaminated water had been hindering work to restore cooling functions in the damaged reactors, which were lost when the March 11 magnitude 9.0 earthquake and tsunami snapped the outside power supply and swamped the emergency backup power supply to the Fukushima Daiichi facility.
Copyright Environment News Service (ENS) 2011. All rights reserved.