Nuclear Catastrophe and Reactor Shutdown
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Remember, at the heart of every nuclear reactor is a
controlled environment of radioactivity and induced fission.
When this environment spins out of control, the results can
be catastrophic.
For many years, the Chernobyl disaster stood as a prime
worst-case example of nuclear malfunction. In 1986, the
Ukrainian nuclear reactor exploded, spewing 50 tons of
radioactive material into the surrounding area,
contaminating millions of acres of forest. The disaster
forced the evacuation of at least 30,000 people, and
eventually caused thousands to die from cancer and other
illnesses [source: History Channel].
Chernobyl was poorly designed and improperly operated. The
plant required constant human attention to keep the reactor
from malfunctioning. Meanwhile, modern plants require
constant supervision to keep from shutting down. Yet even a
well-designed nuclear power plant is susceptible to natural
disaster.
On Friday, March 11, 2011, Japan suffered the largest
earthquake in modern history. A programmed response at the
country's Fukushima-Daiichi nuclear facility immediately
descended all of the reactor's control rods, shutting down
all fission reactions within ten minutes. Unfortunately,
however, you can't shut down all radioactivity with the flip
of a switch.
As we explored on the previous page, nuclear waste continues
to generate heat years after its initial run in a power
plant. Similarly, within the first few hours after a nuclear
reactor shuts down, it continues to generate heat from the
decay process.
The March 2011 quake manifested a deadly tsunami, which
destroyed the backup diesel generators that powered the
water coolant pumps and that the facility had turned to
after it couldn't get power from Japan's grid. These pumps
circulate water through the reactor to remove decay heat.
Uncirculated, both the water temperature and water pressure
inside the reactor continued to rise. Furthermore, the
reactor radiation began to split the water into oxygen and
volatile hydrogen. The resulting hydrogen explosions
breached the reactor building's steel containment panels.
Simply put, the Fukushima-Daiichi facility had many
countermeasures in place to shut down operations in the
event of severe seismic activity. They just didn't count on
losing power to their coolant pumps.
Plants such as Japan's Fukushima-Daiichi facility, Russia's
Chernobyl and the United States' Three Mile Island remain a
black eye for the nuclear power industry, often
overshadowing some of the environmental advantages the
technology has to offer.
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