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