Source: The Wall Street Journal
Author: Phred Dvorak, Juro Osawa and Yuka Hayashi
The Japanese government raised its assessment of the monthlong crisis at its Fukushima Daiichi nuclear power plant to the highest severity level by international standards—a rating only conferred so far upon the Chernobyl accident.
Japan's nuclear regulators said the plant has likely released so much radiation into the environment that it must boost the accident's severity rating on the International Nuclear Event scale to a 7 from 5 currently. That is the same level reached by the Chernobyl nuclear disaster in the former Soviet Union, which struck almost exactly 25 years ago, on April 26, 1986.
"Based on the cumulative data we've gathered, we can finally give an estimate of total radioactive materials emitted,'' Hidehiko Nishiyama, spokesman for Japan's Nuclear and Industrial Safety Agency, said at a press conference Tuesday.
Even as they upgraded their assessment of the situation, Japanese officials went to lengths to say that the problem they are struggling to contain isn't anywhere near the disaster of Chernobyl.
"It is quite different from Chernobyl," said Mr. Nishiyama. "First, the amount of released radiation is about a tenth of Chernobyl," he said, adding that while there were 29 deaths resulting from short-term exposure to high doses of radiation at Chernobyl, there were no such deaths at Fukushima.
"At Chernobyl, the nuclear reactor itself exploded," he said, adding that at the Fukushima plant, the pressure vessel and the containment vessel were largely intact.
Still, Fukushima Daiichi operator Tokyo Electric Power Co. warned Tuesday that since the Fukushima Daiichi plant is still releasing radioactive materials, the total level of radiation released could eventually exceed that of Chernobyl, a spokesman said.
The new assessment comes as Japan admits that the effects of the Fukushima Daiichi nuclear accident—which has already caused the evacuation of tens of thousands of people and spread radiation through groundwater and farms over a broad section of eastern Japan—are likely to be long-lasting and grave. The accident was precipitated by the massive March 11 earthquake and tsunami, which knocked out Fukushima Daiichi's power and cooling systems, causing several of the reactors to overheat.
The International Nuclear Event scale, whose development is coordinated by the International Atomic Energy Agency, measures the severity of accidents based on how much radiation is released, the degree of damage to the nuclear cores and how widespread and long-lasting the effects are likely to be.
Level 5—the previous level given the Fukushima Daiichi accident—indicates a "limited release'' of radioactive materials requiring "some planned countermeasures.'' The 1979 Three Mile Island accident in Pennsylvania was rated a 5.
Level 7 labels this "a major accident," the most serious on the international scale. It means high levels of radiation have been released, and that the amount of time needed to bring the plant under control will require an extended period. But not all "major accidents" are equal in severity.
The decision to upgrade formally the severity of the accident came a day after Japan broadened the 12-mile nuclear evacuation zone around the plant to include all or part of five towns and villages that housed tens of thousands of people before the disaster, a sign that officials now see the long-term risks as far higher than originally estimated.
And the crisis appears far from over, with constant reminders that efforts to bring the crippled reactors under control are far from complete. Operator Tepco scrambled to keep reactors stable in the wake of another big earthquake Monday and a battery fire Tuesday morning, signs of how vulnerable the plant remains a month after the quake.
Experts have predicted it could take months for Tepco to bring Fukushima Daiichi's reactors truly under control, and years to clean up the plant itself.
Japanese nuclear regulators determined that after the accident, the plant has likely released tens of thousands of terabecquerels—or a mind-boggling tens of thousands of trillions of becquerels—of radiation in the immediate area. That's a level that's been recorded only during the Chernobyl accident.
While the new assessment puts Fukushima on a par with Chernobyl, there are key differences between the two, suggesting the Ukraine disaster was still far more serious.
In the case of Chernobyl, a graphite fire burned uncontrolled for days, spewing out radioactive smoke that spread around the world. Fukushima, unlike Chernobyl, has a containment structure, which, even if damaged, has meant that the Japanese accident has shown "much, much, much lower'' traces of far-flung radiation, Wolfgang Weiss, chair of the United Nations Scientific Committee on the Effects of Atomic Radiation, said in Vienna last week.
The release from Fukushima of tens of thousands of terabecquerels of iodine-131, while huge, appears to be smaller than the 5.2 million terabecquerels released from Chernobyl. Japanese government officials said the radiation release was between 370,000 and 630,000 terabecquerels so far from Fukushima. The permissible level of iodine-131 for vegetables and fish is 2,000 becquerels per kilogram, or just a tiny fraction of what has been released.
A 2005 United Nations study said up to 4,000 people could eventually die from radiation exposure to Chernobyl.
In Japan, so far, a handful of workers have been hospitalized, but they were released a few days later, and regulators said they showed no signs of lasting injury.
There are, however, regular reports in the Japanese press of elevated radiation exposure for the workers trying to contain Fukushima, and it could be months, or years, before the real impact is known. The same is true for the population in and around the plant.
Officials said they expanded the original evacuation zone because the accident had lasted longer than expected.
"Japan has been doing drills for possible nuclear accidents, but they assumed that the accidents would be resolved in about 10 days," said Mr. Nishiyama, the spokesman. "We are now dealing with a crisis of a historic proportion. This has necessitated different kinds of responses than initially planned."
Even in announcing the expanded evacuation zone, Japanese officials said residents of the affected areas weren't in danger of surpassing government exposure limits anytime soon and that they have about a month to move.
Testing by Japanese, U.S. and IAEA officials shows that the radioactive contamination is spreading unevenly from the plant, creating what are known as hot spots due to wind, topography and other natural conditions that show a higher density of radioactive material compared with some areas closer to the plant.
The move will present major logistical hurdles for communities already battered by the March 11 earthquake and tsunami that damaged the plant as well as much of the surrounding countryside. The area includes towns and villages with a population totaling about 115,000 people before the crisis, though the number of people affected is likely to be far less because the government's order applies only to particular hot spots believed to have higher radiation levels, not a set radius from the plant.
Meanwhile, efforts to stabilize reactors at Fukushima Daiichi continue to be dogged by setbacks and scares, in a sign of how fragile the situation on the ground remains. On Tuesday morning, Tepco said there was a small fire at a battery unit outside reactor No. 4, which was put out shortly after being reported.
On Monday, a 7.1 magnitude quake centered in coastal Fukushima temporarily shut down power supply and makeshift cooling systems to three reactors at the plant, causing the evacuation of workers to the compound's command center. The systems remained down for nearly an hour while the evacuation remained in effect, keeping workers from switching to emergency power generators.
Tepco said the suspension didn't appear to have caused significant safety issues. But the scramble to restore power served as a reminder of how aftershocks and the risk of tsunami could upset the delicate efforts to stabilize the problems at the plant.