24 K. HASEGAWA
operation for regular maintenance at the time of the earthquake. Units
1–3 automatically shut down at the onset of the earthquake, but the
external power supplies and almost all in-house AC power supplies were
lost due to the earthquake and the tsunami. Reactors and spent-fuel pools
lost their cooling capabilities as a result. Explosions of the reactor buildings occurred at Units 1, 3, and 4, which were caused by the hydrogen
released from the damaged core and that filled the reactor buildings. The
reactor core of Unit 2 also seems to have been seriously damaged. A
large amount of radioactive materials has been released and spread from
this accident.
The severity of the Chernobyl and the Fukushima accidents was
rated seven on the International Nuclear Event Scale. The Fukushima
nuclear accident has several historical “firsts.” It is the first severe accident of a nuclear power station; the complex disaster being triggered by
a large earthquake and tsunami. It is the first example of “Quake and
Nuclear Disaster Complex” or “complex disaster” which a seismologist,
Dr. Ishibashi Katsuhiko, has warned of since 1997. Second, four reactors
were simultaneously endangered for the first time. In the midst of the
accident, on March 15, only about 50 workers, the smallest number of
workers needed to operate the plant, a group that has since come to be
known as the “Fukushima 50” (the subject of a recent movie in Japan)
had to operate under strong radiation and very unstable conditions, in
darkness due to the loss of AC power and numerous after-shocks. Third,
the stable cooling function started only after 4 months from the accident
and the uncontrolled situation of the reactor meltdown continued for
more than 9 months. The crisis of the Three Mile Island (TMI) nuclear
accident in the USA in 1978 passed after the first 6 days. Even in case of
the Chernobyl accident, a large amount of radiation was halted after the
first 10 days. Fourth, it is the first severe accident of a nuclear power plant
on the coast. The TMI and the Chernobyl stations were located inland. In
Japan, all nuclear reactors are located on the coast so that cooling water
can be sourced from the sea and heated effluent after cooling can be
discharged into it. Contaminated water overflows into the ocean sometimes even still now when heavy rainfalls by typhoon or other kind of
storms. Scientists are worried about serious contamination of seawater
and damages to the ecosystem as the long-term effect.
The most tragic and painful cases are the 160,000 evacuees, the peak
number that was registered in June 2012. These evacuees had been living
near the melted-down nuclear plant. A zone of up to 20 km from the
operation for regular maintenance at the time of the earthquake. Units
1–3 automatically shut down at the onset of the earthquake, but the
external power supplies and almost all in-house AC power supplies were
lost due to the earthquake and the tsunami. Reactors and spent-fuel pools
lost their cooling capabilities as a result. Explosions of the reactor buildings occurred at Units 1, 3, and 4, which were caused by the hydrogen
released from the damaged core and that filled the reactor buildings. The
reactor core of Unit 2 also seems to have been seriously damaged. A
large amount of radioactive materials has been released and spread from
this accident.
The severity of the Chernobyl and the Fukushima accidents was
rated seven on the International Nuclear Event Scale. The Fukushima
nuclear accident has several historical “firsts.” It is the first severe accident of a nuclear power station; the complex disaster being triggered by
a large earthquake and tsunami. It is the first example of “Quake and
Nuclear Disaster Complex” or “complex disaster” which a seismologist,
Dr. Ishibashi Katsuhiko, has warned of since 1997. Second, four reactors
were simultaneously endangered for the first time. In the midst of the
accident, on March 15, only about 50 workers, the smallest number of
workers needed to operate the plant, a group that has since come to be
known as the “Fukushima 50” (the subject of a recent movie in Japan)
had to operate under strong radiation and very unstable conditions, in
darkness due to the loss of AC power and numerous after-shocks. Third,
the stable cooling function started only after 4 months from the accident
and the uncontrolled situation of the reactor meltdown continued for
more than 9 months. The crisis of the Three Mile Island (TMI) nuclear
accident in the USA in 1978 passed after the first 6 days. Even in case of
the Chernobyl accident, a large amount of radiation was halted after the
first 10 days. Fourth, it is the first severe accident of a nuclear power plant
on the coast. The TMI and the Chernobyl stations were located inland. In
Japan, all nuclear reactors are located on the coast so that cooling water
can be sourced from the sea and heated effluent after cooling can be
discharged into it. Contaminated water overflows into the ocean sometimes even still now when heavy rainfalls by typhoon or other kind of
storms. Scientists are worried about serious contamination of seawater
and damages to the ecosystem as the long-term effect.
The most tragic and painful cases are the 160,000 evacuees, the peak
number that was registered in June 2012. These evacuees had been living
near the melted-down nuclear plant. A zone of up to 20 km from the