1986 : NUCLEAR DISASTER AT CHERNOBYL:
On April 26, 1986, the world's worst nuclear power plant accident
occurs at the Chernobyl nuclear power station in the Soviet Union.
Thirty-two people died and dozens more suffered radiation burns in the
opening days of the crisis, but only after Swedish authorities
reported the fallout did Soviet authorities reluctantly admit that an
accident had occurred.
The Chernobyl station was situated at the settlement of Pripyat, about
65 miles north of Kiev in the Ukraine. Built in the late 1970s on the
banks of the Pripyat River, Chernobyl had four reactors, each capable
of producing 1,000 megawatts of electric power. On the evening of
April 25, 1986, a group of engineers began an electrical-engineering
experiment on the Number 4 reactor. The engineers, who had little
knowledge of reactor physics, wanted to see if the reactor's turbine
could run emergency water pumps on inertial power.
As part of their poorly designed experiment, the engineers
disconnected the reactor's emergency safety systems and its
power-regulating system. Next, they compounded this recklessness with
a series of mistakes: They ran the reactor at a power level so low
that the reaction became unstable, and then removed too many of the
reactor's control rods in an attempt to power it up again. The
reactor's output rose to more than 200 megawatts but was proving
increasingly difficult to control. Nevertheless, at 1:23 a.m. on April
26, the engineers continued with their experiment and shut down the
turbine engine to see if its inertial spinning would power the
reactor's water pumps. In fact, it did not adequately power the water
pumps, and without cooling water the power level in the reactor
surged.
To prevent meltdown, the operators reinserted all the 200-some control
rods into the reactor at once. The control rods were meant to reduce
the reaction but had a design flaw: graphite tips. So, before the
control rod's five meters of absorbent material could penetrate the
core, 200 graphite tips simultaneously entered, thus facilitating the
reaction and causing an explosion that blew off the heavy steel and
concrete lid of the reactor. It was not a nuclear explosion, as
nuclear power plants are incapable of producing such a reaction, but
was chemical, driven by the ignition of gases and steam that were
generated by the runaway reaction. In the explosion and ensuing fire,
more than 50 tons of radioactive material were released into the
atmosphere, where it was carried by air currents.
On April 27, Soviet authorities began an evacuation of the 30,000
inhabitants of Pripyat. A cover-up was attempted, but on April 28
Swedish radiation monitoring stations, more than 800 miles to the
northwest of Chernobyl, reported radiation levels 40 percent higher
than normal. Later that day, the Soviet news agency acknowledged that
a major nuclear accident had occurred at Chernobyl.
In the opening days of the crisis, 32 people died at Chernobyl and
dozens more suffered radiation burns. The radiation that escaped into
the atmosphere, which was several times that produced by the atomic
bombs dropped on Hiroshima and Nagasaki, was spread by the wind over
Northern and Eastern Europe, contaminating millions of acres of forest
and farmland. An estimated 5,000 Soviet citizens eventually died from
cancer and other radiation-induced illnesses caused by their exposure
to the Chernobyl radiation, and millions more had their health
adversely affected. In 2000, the last working reactors at Chernobyl
were shut down and the plant was officially closed.
occurs at the Chernobyl nuclear power station in the Soviet Union.
Thirty-two people died and dozens more suffered radiation burns in the
opening days of the crisis, but only after Swedish authorities
reported the fallout did Soviet authorities reluctantly admit that an
accident had occurred.
The Chernobyl station was situated at the settlement of Pripyat, about
65 miles north of Kiev in the Ukraine. Built in the late 1970s on the
banks of the Pripyat River, Chernobyl had four reactors, each capable
of producing 1,000 megawatts of electric power. On the evening of
April 25, 1986, a group of engineers began an electrical-engineering
experiment on the Number 4 reactor. The engineers, who had little
knowledge of reactor physics, wanted to see if the reactor's turbine
could run emergency water pumps on inertial power.
As part of their poorly designed experiment, the engineers
disconnected the reactor's emergency safety systems and its
power-regulating system. Next, they compounded this recklessness with
a series of mistakes: They ran the reactor at a power level so low
that the reaction became unstable, and then removed too many of the
reactor's control rods in an attempt to power it up again. The
reactor's output rose to more than 200 megawatts but was proving
increasingly difficult to control. Nevertheless, at 1:23 a.m. on April
26, the engineers continued with their experiment and shut down the
turbine engine to see if its inertial spinning would power the
reactor's water pumps. In fact, it did not adequately power the water
pumps, and without cooling water the power level in the reactor
surged.
To prevent meltdown, the operators reinserted all the 200-some control
rods into the reactor at once. The control rods were meant to reduce
the reaction but had a design flaw: graphite tips. So, before the
control rod's five meters of absorbent material could penetrate the
core, 200 graphite tips simultaneously entered, thus facilitating the
reaction and causing an explosion that blew off the heavy steel and
concrete lid of the reactor. It was not a nuclear explosion, as
nuclear power plants are incapable of producing such a reaction, but
was chemical, driven by the ignition of gases and steam that were
generated by the runaway reaction. In the explosion and ensuing fire,
more than 50 tons of radioactive material were released into the
atmosphere, where it was carried by air currents.
On April 27, Soviet authorities began an evacuation of the 30,000
inhabitants of Pripyat. A cover-up was attempted, but on April 28
Swedish radiation monitoring stations, more than 800 miles to the
northwest of Chernobyl, reported radiation levels 40 percent higher
than normal. Later that day, the Soviet news agency acknowledged that
a major nuclear accident had occurred at Chernobyl.
In the opening days of the crisis, 32 people died at Chernobyl and
dozens more suffered radiation burns. The radiation that escaped into
the atmosphere, which was several times that produced by the atomic
bombs dropped on Hiroshima and Nagasaki, was spread by the wind over
Northern and Eastern Europe, contaminating millions of acres of forest
and farmland. An estimated 5,000 Soviet citizens eventually died from
cancer and other radiation-induced illnesses caused by their exposure
to the Chernobyl radiation, and millions more had their health
adversely affected. In 2000, the last working reactors at Chernobyl
were shut down and the plant was officially closed.
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