The steel container protecting a nuclear reactor at a plant facing a possible meltdown was not damaged in an explosion that injured four workers and destroyed the exterior walls of the plant, a Japanese government spokesman said today.
The blast at the Fukushima Daiichi plant occurred outside the containment vessel and did not damage the nuclear reactor itself, which would cause radioactive material to leak out, a government spokesman Yukio Edano said.
Contrary to initial reports of radiation levels rising around the Fukushima Daiichi plant after the blast, Edano said that radiation is decreasing and that the pressure inside the reactor is also dropping.
"Based on this situation, we are concerned about the nuclear reactor and have decided to fill the reactor with sea water" to further decrease pressure and cool down the reactor, Edano said.
Flooding the containment vessel with sea water mixed with boron instead of fresh water is an unusual measure, according to Robert Alvarez, a senior scholar at the Institute for Policy Studies, who described it as a "Hail Mary pass" but a necessary step to keep the reactor core covered and the containment vessel cool. The restoration of power to the plant remains critical to prevent against the possibility of an outright meltdown.
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After assurances from Japanese officials about the situation, a top U.S. scientist said Japan must come to terms with the severity of the nuclear accident it is facing and work to immediately protect its most vulnerable residents from the damage of radiation exposure -- particularly protecting children against exposure to radioactive iodine.
"Any attempt to make it seem that this is not the worst case imaginable is foolhardy," said Edwin Lyman, a senior scientist with the Union of Concerned Scientists.
An estimated 170,000 people surrounding the Fukushima Daiichi plant have been evacuated, according to the International Atomic Energy Agency. Three evacuees have been exposed to radiation, but have not shown signs of illness, a Fukushima prefectural disaster official confirmed to the Associated Press.
Japanese authorities told the International Atomic Energy Agency that they are preparing to distribute potassium iodide to residents in the area around both the Fukushima Daiichi and nearby Fukushima Daini plants. The U.S. and France have plans in place to distribute doses of potassium iodide to children who live in the vicinity of the plant in the event of a catastrophic radiation release.
If the reactor core melts through the steel vessel that is housing it, Lyman said, the risk Japan faces is a radioactive plume that could disperse tens or even hundreds of miles. "You could have large swaths of areas that will need severe remediation. And a lot of people exposed to radioactivity who will have an increased chance of cancer."
After the nuclear accident at Chernobyl, Lyman said there were over 6,000 cases of childhood thyroid cancers, and it was later determined if the children had taken potassium iodide a few hours before being exposed to the radiation it would block the intake of the radioactive material in the thyroid. "That has been shown to reduce exposure significantly," he said.