Japan’s nuclear crisis intensified yesterday as authorities raced to combat the threat of multiple reactor meltdowns and more than 170,000 people evacuated the quake and tsunami-savaged northeastern coast where fears spread over possible radioactive contamination.
Nuclear plant operators were frantically trying to keep temperatures down in a series of nuclear reactors — including one where officials feared a partial meltdown could be happening yesterday — to prevent the situation from deteriorating.
Japanese Chief Cabinet Secretary Yukio Edano said yesterday that a hydrogen explosion could occur at Unit 3 of the Fukushima Dai-ichi nuclear complex, the latest reactor to face a possible meltdown.
That follows a blast the day before in the power plant’s Unit 1.
“At the risk of raising further public concern, we cannot rule out the possibility of an explosion,” Edano said. “If there is an explosion, however, there would be no significant impact on human health.”
Edano said the radioactivity released into the environment so far was so small it posed no health threat.
He said none of the Fukushima Dai-ichi reactors was near the point of complete meltdown and he was confident of escaping the worst scenarios.
A complete meltdown — the collapse of a power plant’s ability to keep temperatures under control — could release uranium and dangerous contaminants into the environment and pose major, widespread health risks.
WAITING
Up to 160 people, including 60 elderly patients and medical staff who had been waiting for evacuation in the nearby town of Futabe, and 100 others evacuating by bus, might have been exposed to radiation, said Ryo Miyake, a spokesman from Japan’s nuclear agency.
The severity of their exposure, or if it had reached dangerous levels, was not clear. They were being taken to hospitals.
Edano said operators were trying to cool and decrease the pressure in the Unit 3 reactor, just as they had the day before at Unit 1.
Japan struggled with the nuclear crisis as it tried to determine the scale of the Friday disasters, when the most powerful quake in the country’s recorded history was followed by a tsunami.
More than 1,400 people were killed and hundreds more were missing, according to officials, but police in one of the worst-hit areas estimated the toll there alone could eventually top 10,000.
The scale of the disasters seemed to be outpacing the efforts of Japanese authorities to bring the situation under control.
Rescue teams were struggling to search hundreds of kilometers of devastated coastline and hundreds of thousands of hungry survivors huddled in darkened emergency centers cut off from rescuers and aid. At least 1.4 million households had gone without water since the quake, and food and gasoline were quickly running out across the region. Large areas of the countryside were surrounded by water and unreachable. About 2 million households were without electricity.
POWER OUTAGE
Unit 3 at the Fukushima plant is one of three reactors there that had automatically shut down and lost cooling functions necessary to keep fuel rods working properly because of a power outage from the quake. The facility’s Unit 1 is also in trouble, but Unit 2 is less affected.
On Saturday, an explosion destroyed the walls of Unit 1 as operators tried to prevent it from overheating and melting down.
Without power and with its valves and pumps damaged by the tsunami, authorities resorted to drawing sea water mixed with boron in an attempt to cool the unit’s overheated uranium fuel rods. Boron disrupts nuclear chain reactions.
The move likely renders the 40-year-old reactor unusable, said a foreign ministry official briefing reporters. Officials said the sea water will remain inside the unit, possibly for several months.
Robert Alvarez, senior scholar at the Institute for Policy Studies and former senior policy adviser to the US secretary of energy, told reporters that the sea water was a desperate measure.
“It’s a Hail Mary pass,” he said.
He said that the success of using sea water and boron to cool the reactor will depend on the volume and rate of their distribution.
Another key, he said, was the restoration of electrical power, so that normal cooling systems can operate.
Edano said the cooling operation at Unit 1 was going smoothly after the sea water was pumped in.
Operators released slightly radioactive air from Unit 3 yesterday, while injecting water into it hoping to reduce pressure and temperature to prevent a possible meltdown, Edano said.
He said radiation levels just outside the plant briefly rose above legal limits, but since had declined significantly. Also, fuel rods were exposed briefly, he said, indicating that coolant water didn’t cover the rods for some time. That would have contributed further to raising the temperature in the reactor vessel.
At an evacuation center in Koriyama, about 60km from the troubled reactors and 190km north of Tokyo, medical experts had checked about 1,500 people for radiation exposure in an emergency testing center, an official said.
steady flow
Yesterday, a steady flow of people arrived at the center, where they were checked by officials.
Officials placed five reactors, including Units 1 and 3 at Dai-ichi, under states of emergency on Friday after operators lost the ability to cool the reactors using usual procedures.
An additional reactor was added to the list early yesterday, for a total of six — three at the Dai-ichi complex and three at another nearby complex. Local evacuations have been ordered at each location. Japan has 55 reactors spread across 17 complexes nationwide.
Officials began venting radioactive steam at Fukushima Dai-ichi’s Unit 1 to relieve pressure inside the reactor vessel, which houses the overheated uranium fuel.
Concerns escalated dramatically on Saturday when that unit’s containment building exploded.
Officials were aware that the steam contained hydrogen and were risking an explosion by venting it, acknowledged Shinji Kinjo, spokesman for the government’s Nuclear and Industrial Safety Agency, but chose to do so because they needed to keep circulating cool water on the fuel rods to prevent a meltdown.
Officials insisted there was no significant radioactive leak after the explosion.
Source: Taipei Times - 2011/03/14
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