Water cannons may have had some success in cooling one reactor at Japan’s damaged Fukushima nuclear plant, while the United Nations nuclear agency said the situation remained “very serious.”
Cannons and helicopters were used to douse the plant yesterday as workers tried to stem radioactive pollution from the worst nuclear accident since Chernobyl. Some water may have reached the No. 3 reactor, a Tokyo Electric Power Co. official said. Engineers worked during the night to connect a power cable that may help get Fukushima’s cooling systems working again.
“Everything depends on the amount of water Tepco can bring to the site,” Olivier Gupta, a deputy head of the Autorite de Surete Nucleaire, France’s nuclear regulator, said yesterday in Paris. “The Japanese operator has said it is trying to bring power back to the site. It’s clearly a positive move, but the power must supply something like pumps.”
Tokyo Electric’s failure to end the threat of radiation from the six-reactor Fukushima plant has prompted the U.S. to advise its citizens to consider leaving Japan and start airlifting some out of the country, while Australia has advised against travel to Tokyo. About 2.3 trillion yen ($29 billion) has been wiped from Tepco’s market value since the March 11 earthquake, tsunami and a series of explosions devastated the 40-year-old power station that is about 135 miles (220 kilometers) north of Tokyo.
“We were able to see some steam,” Tsuyoshi Makigami, chief of nuclear facility management at Tokyo Electric, said at a briefing broadcast by NHK late yesterday. “It’s fair to say that the spraying was somewhat effective.”
The company plans to lay 1 kilometer of a new power line during the night to supply electricity to the stricken plant, a company official told the press conference. The link is intended to restore power to the plant’s cooling systems.
Engineers had finished laying the line to Unit 2 at the plant, the UN’s International Atomic Energy Agency said in a statement on its website. Power will be reconnected to that unit once the spraying of water on Unit 3 ends, the agency said.
The agency said the situation at the three loaded cores -- reactors No. 1, 2 and 3 -- has been “relatively stable” in the last 24 hours. All three units are damaged and lack cooling, Director Graham Andrew said yesterday at a briefing in Vienna. The situation remains “very serious,” he said.
The greatest risks at Fukushima may come from the spent fuel pools that sit on the top of the six reactors.
Japan’s Nuclear and Industrial Safety Agency said yesterday there is a possibility of no water at the No. 4 reactor’s spent-fuel cooling pool. If exposed to air, the fuel rods could decay, catch fire and spew radioactive materials into the air. The agency has detected no smoke or steam rising from the reactor, spokesman Hidehiko Nishiyama said.
Exposure of spent-fuel rods to air “could result in fracturing of the fuel rod cladding and escape of dangerous radioactive fission products” such as iodine-131, cesium-137 and strontium-90, said Stephen Lincoln, an environmental chemist at the University of Adelaide.
All water in the No. 4 reactor’s spent-fuel pond has drained, U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko told a congressional panel in Washington March 15. Fuel rods stored in three reactors at the Tokyo Electric plant are exposed and releasing radiation, Yukiya Amano, head of the International Atomic Energy Agency, said in Vienna before departing for Tokyo.
Helicopters are being used to determine radiation readings, water levels in the pool and damage to the reactors, Tepco spokesman Kaoru Yoshida told reporters in Tokyo yesterday. Technicians were unable to inspect the facilities because of high levels of radiation.
Jaczko has said the situation “will take some time, possibly weeks” to resolve.
More than 320 workers were at the plant site yesterday. Tokyo Electric evacuated 750 employees on March 15 when radiation levels spiked.
The recent increase in employees at the Daiichi plant could indicate that a work rotation is being implemented to minimize radiation exposure. Japan’s health ministry raised the cumulative maximum legal exposure for nuclear workers to 250 millisieverts from 100 millisieverts on March 15 to enable workers to stay longer on the site to prevent a nuclear disaster.
Radiation levels have reached 10 millisieverts per hour in some parts of the plant, said John Price, a Melbourne-based consultant on industrial accidents and former member of the safety policy unit at the National Nuclear Corporation U.K.
“That means they have an access time of 10 to 25 hours at the most,” Price said in a telephone interview yesterday. “At that rate, you are going to go through workers very fast.”
The failure of backup generators used to pump cooling water caused explosions in at least three of the structures surrounding the station’s reactors, as well as a fire in a pond containing spent fuel rods.
The NRC’s Jaczko said radiation at the Japanese site is fluctuating and at peak levels “would be lethal within a fairly short period of time.”
His information came from NRC staff who were dispatched to Japan to help with the response and have been in contact with industry officials there, he said. Jaczko’s assessment prompted the U.S. to urge American citizens to consider leaving Japan. France and Germany have already told their citizens to depart.
There have been more than 450 aftershocks since the magnitude-9 temblor left hundreds of thousands stranded and without power, with disruptions to food and water supplies. The Japanese government has dispatched 100,000 troops to the northeastern region.