http://news.businessweek.com/article.asp?documentKey=1376-LU10Q56KLVS101-25B42PBBAAGTL9H5JPAVA41NPT
Tepco Detects Nuclear Fission at Fukushima Station
By Tsuyoshi Inajima and Yuji Okada
November 02, 2011 4:38 AM EDT
<http://twitter.com/share?text=Tepco+Detects+Nuclear+Fission+at+Fukushima+Station+-+Bloomberg+via+%40BloombergNow&url=http://bloom.bg/sSC6aS>
<http://mobile.bloomberg.com/photo/2011-11-01/tepco-says-nuclear-fission-possible-at-fukushima-plant-2->
(Corrects result of reactor fission in fourth paragraph.)
Tokyo <http://mobile.bloomberg.com/topics/tokyo/> Electric Power Co.
detected signs of nuclear fission at its crippled Fukushima atomic power
plant, raising the risk of increased radiation emissions. No increase in
radiation was found at the site and the situation is under control,
officials said.
The company, known as Tepco, began spraying boric acid on the No. 2
reactor at 2:48 a.m. Japan
<http://mobile.bloomberg.com/topics/japan/> time to prevent accidental
chain reactions. Tepco said it may have found xenon, which is associated
with nuclear fission, while examining gases taken from the reactor,
according to an e-mailed statement today.
“Given the signs, it’s certain that fission is occurring,” Junichi
Matsumoto, a general manager at Tepco who regularly talks to the media,
told reporters in Tokyo today. There’s been no large-scale or sustained
criticality and no increase in radiation, he said.
Fission taking place in the reactor can lead to increases in radiation
emissions and raises concerns about further leaks after another
radioactive hot spot was discovered in Tokyo on Oct. 29. It’s possible
there are similar reactions occurring in the No. 1 and No. 3 reactors,
the other cores damaged at the station, Matsumoto said.
“Melted fuel in the No. 2 reactor may have undergone a sustained process
of nuclear fission or re-criticality,” Tetsuo Ito, the head of Kinki
University’s Atomic Energy Research Institute, said by phone. “The
nuclear fission should be containable by injecting boron into the
reactor to absorb neutrons.”
Loss of Cooling
Shares of Tepco declined 2.6 percent to close at 302 yen on the Tokyo
Stock Exchange. They’ve fallen 86 percent since the disaster. The
benchmark Nikkei 225 Stock Average was down 2.2 percent.
Eight months after the March 11 earthquake and tsunami wrecked the
Fukushima Dai-Ichi plant, causing a loss of cooling and the meltdowns of
three reactors, Tepco is trying to prevent further leakage of radiation
that has spread across the world.
The incident, the worst atomic disaster since Chernobyl in 1986, was
responsible for the biggest discharge of radioactive material into the
ocean in history, according to a study from a French nuclear safety
institute.
“We are evaluating whether there are many reactions or not or whether
its stopped, Matsumoto said. The incident won’t affect its schedule of
bringing the plant under control by the end of this year, Matsumoto said.
Yasuhiro Sonoda, a member of the ruling Democratic Party
<http://mobile.bloomberg.com/topics/democratic-party/> of Japan, on Oct.
31 drank a glass of filtered water from the Fukushima plant to
demonstrate the situation is being brought under control.
Publicity Stunt
Sonoda denied reporters’ claims it was a publicity stunt. ‘‘I drank it
because there shouldn’t be any concerns about the water,” he said. “I
didn’t intend to say it’s completely safe by drinking it.”
No significant changes in temperatures and pressures of the reactor and
radiation levels at the site have been detected, said Hiroyuki Usami, a
spokesman for Tepco.
The temperature of the bottom of the No. 2 reactor pressure vessel was
76 degrees Celsius (167 Fahrenheit) at 5 a.m. today, compared with 77.4
degrees a day earlier and 77.5 degrees two days ago, according to
Tepco’s data. Radiation levels taken near the west gate of the plant
have been stable at about 11 microsieverts per hour for the past few
days, the data shows.
Splitting Atoms
Should fissioning have occurred the injection of boron will have stopped
it, said Tadashi Narabayashi, a former reactor safety researcher at
Toshiba Corp. (6502)
<http://mobile.bloomberg.com/apps/quote?ticker=6502:JP> and now a
nuclear engineering professor at Hokkaido University
<http://mobile.bloomberg.com/topics/hokkaido-university/>.
Fissioning involves the splitting of atoms, which, in the case of
certain uranium isotopes, can lead to an uncontrolled reaction and
emittance of radiation.
Tepco and the government have said they are on track to bring the
damaged reactors into a safe state known as cold shutdown by the end of
the year.
Tepco and the Japan Atomic Energy Agency are reexamining the gases, said
Toshiyuki Koganeya, a spokesman for the Nuclear and Industrial Safety
Agency, the government regulator.
Even if Tepco’s analysis is correct, nuclear fission would be taking
place in a “very restricted part” of the reactor, said Koganeya. The
regulator believes fuel accumulated at the bottom of the pressure vessel
and containment vessel is unlikely to start melting again, he said.
Damaged Reactors
Fukushima sustained major damage at four of its six reactor buildings at
the Dai-Ichi plant, including the three core meltdowns and possible
damage to a spent fuel pool.
The radioactive cesium that flowed into the sea from the plant was 20
times the amount estimated by Tepco, according to the Institute for
Radiological Protection and Nuclear Safety, which is funded by the
French government.
The oceanic study estimates 27,000 terabecquerels of radioactive cesium
137 leaked into the sea from the plant. The
Fukushima station may have emitted more than twice the amount of
radiation than estimated by the Japanese government at the height of the
Fukushima accident, according to another study by the Atmospheric
Chemistry and Physics journal.
Tepco has declined to comment on both studies.
To contact the reporters on this story: Tsuyoshi Inajima in Tokyo at
[email protected] <mailto:[email protected]>; Yuji Okada in
Tokyo [email protected] <mailto:[email protected]>
To contact the editor responsible for this story: Teo Chian Wei at
[email protected] <mailto:[email protected]>
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