Station Discharged More Radiation Than Estimated Fukushima
October 27, 2011, 4:45 AM EDT
By Tsuyoshi Inajima
(Updates with NISA comment in fifth paragraph.)
Oct. 27 (Bloomberg) -- The wrecked
Tokyo Electric Power Co.’s
The amount is about 42 percent of that released at
“This early onset of emissions is interesting and may indicate some structural damage to the reactor units during the earthquake,” according to the report.
NISA and Tepco blame the tsunami, which swamped backup generators, causing a loss of cooling and the meltdowns of the three reactors operating at the time of the disaster. Explosions at the plant sent radiation into the atmosphere.
Cesium 137 is a source of concern for public health because the radioactive isotope has a half-life of 30 years.
A becquerel represents one radioactive decay per second and involves the release of atomic energy, which can damage human cells and DNA. Prolonged exposure to radiation can cause leukemia and other forms of cancer, according to the World Nuclear Association. A terabecquerel is one million times one million becquerels.
Almost a fifth of the cesium 137 fallout fell on
Areas around the Fukushima Dai-Ichi plant, which is still emitting radioactive materials, may be uninhabitable for at least two decades, according to a government estimate in August.
The study led by Andreas Stohl, an atmospheric scientist at the Norwegian Institute for Air Research, was released on the website of Atmospheric Chemistry and Physics Discussions. The authors used readings from stations around the world to assess the amount of radiation release.
Japanese government officials and the utility known as Tepco haven’t updated figures on radiation from the Fukushima Dai-Ichi station. Tepco said last week the amount of radiation being released has fallen to about 8 million times less than at the height of the disaster.
“We don’t need to add much to what was emitted in the early days,” Yasuo Kosaku, an official in NISA’s nuclear emergency division, said by phone today. Still, “the June estimate may have to be revised.”
The government plans to update the estimate, Goshi Hosono, the minister in charge of responding to the disaster, said in August.
The scientists provided other analysis that questions official assessments.
The levels of cesium 137 emissions “suddenly dropped” after Tepco started spraying water on the spent fuel pool of the No. 4 reactor, they said. Reactor 4 was idle before the quake and the fuel assemblies in the core had been placed in the spent fuel pool of the unit.
“This indicates that emissions were not only coming from the damaged reactor cores, but also from the spent fuel pool of unit 4,” the report said.
The government estimated in June 11 million terabecquerels of the radioactive particle was released from the plant.
Xenon 133 has a half life of 5.2 days and is relatively harmless, Tetsuo Ito, the head of Kinki University’s Atomic Energy Research Institute, said by phone.
--With assistance from Makoto Miyazaki in
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