Partial meltdown likely underway at reactor in Japan
Published Saturday, March 12, 2011 11:57PM EST
Last Updated Saturday, May 19, 2012 4:10AM EDT
As the cooling systems fail at three reactors within the same nuclear power complex, a top Japanese official is saying that one of those reactors could be in the midst of a partial meltdown.
Chief Cabinet Secretary Yukio Edano told reporters Sunday that operators at the Fukushima Dai-ichi nuclear plant have been trying to reduce pressure and heat inside Unit 3, but a partial meltdown in the unit is "highly possible."
"Because it's inside the reactor, we cannot directly check it, but we are taking measures on the assumption of the possible partial meltdown," he said.
Officials haven't said how high the temperature has risen inside the troubled reactor. If it reaches 4,000 degrees, the uranium fuel pellets inside the reactor's fuel rods will start to dissolve, the beginning of a meltdown.
A complete meltdown would release uranium and other toxic nuclear byproducts into the environment.
As work continues too cool down Unit 3, authorities are also trying to stop a meltdown that began a day earlier in another reactor that was the site of an explosion on Saturday. The blast destroyed the building housing the reactor, but not the actual steel envelope encasing the reactor.
Meanwhile, the cooling system at a third reactor within Fukushima Dai-ichi has also failed – raising the possibility that reactor could begin to overheat too. Three other reactors at the facility are in a safe, shut-down state.
Evacuation zone grows
Until now, Japanese officials had been downplaying the danger at Fukushima, even while they spent Saturday increasing the size of the evacuation zone around the facility.
Nearly 170,000 people within a 20-kilometre radius around Dai-ichi have been evacuated, the International Atomic Energy Agency reports. As well, another 30,000 have also been evacuated near the Fukushima Daini (or Second) plant, 11 kilometres to the south, which has also lost its cooling functions.
The IAEA reports that three reactors at that plant are experiencing increased pressure.
"Evacuations around both affected nuclear plants have begun," the atomic watchdog said in a statement. "Full evacuation measures have not been completed."
Japanese authorities say they are making preparations to distribute iodine pills to residents in the area of both plants. The pills can help protect against thyroid cancer, since they inhibit the thyroid's absorption of radioactive iodine from the atmosphere.
Damon Moglen, the Climate and Energy Project director at Friends of the Earth -- a group that opposes the use of nuclear power -- worries that the IAEA is not being fully transparent about the scope of the threat.
"Given that we are now talking about a potential meltdown, given that we've had an explosion at this reactor, given that there are real indications that there is a problem with containment, I think the IAEA is really downplaying this incident and it's far more serious than they are saying," he told CTV National News Saturday night.
'Nobody knows how to shut off radioactivity'
Gordon Edwards, with the Canadian Coalition for Nuclear Responsibility, says a meltdown is always possible when a nuclear reactor loses its cooling system.
"You cannot shut a nuclear reactor completely off. Because even when it's shut down totally, there's still 200 megawatts of heat being generated just by the radioactivity alone, and nobody knows how to shut off radioactivity," he explained to CTV News Channel Saturday evening.
"So unless you cool the core of the reactor for days after it's shut down, it's going to suffer an increase of temperature, which will cause a melting of the fuel rods at 5,000 degree Fahrenheit, which is more than twice the melting point of steel."
According to the International Nuclear and Radiological Event Scale, the incident underway at Fukushima is classified as a 4 on its 1 to 7 scale. The Chernobyl disaster was rated 7, while Three Mile Island was rated a 5.
The 4 rating means it's an accident that has "local consequences," such as severe health problems for workers.
With files from Associated Press