Worst nuclear plant accident: world record set by
26] CHERNOBYL, Ukraine--The "Chernobyl disaster", reactor
accident at the Chernobyl nuclear power plant, or simply "Chernobyl",
sets the world record for worst nuclear power plant accident
in history and the only instance so far of level 7 on
the International Nuclear Event Scale, resulting in a severe
26, 1986 at 1:23:40 a.m., reactor 4 suffered a catastrophic
steam explosion resulting in a nuclear meltdown, a series
of additional explosions and a fire; the radiation was not
contained and radioactive particles were carried by wind across
international borders. (enlarge
The Chernobyl disaster occurred as the result
of an unauthorized test being conducted, in which the reactor
was run while its cooling system was inoperative. The resulting
clouds of radioactive isotopes spread all over Europe, from
Ireland to Greece.
A total of 9 tonnes/8.9 tons of radioactive material
were released into the atmosphere, 90 times the amount produced
by the Hiroshima A-bomb.
Photo: Belarusian soldiers checking for
radiation in tomatoes brought from Ukraine, near the Chernobyl
nuclear power station. AFP/Corbis (enlarge
In all, 5 million people are thought to have been exposed
to radioactivity following the blast. In Ukraine, Belarus,
and Russia more than 500,000 people were displaced from affected
towns and villages and thousands of square miles of land were
The Chernobyl power station was situated
at the settlement of Pryp'yat, 10 miles (16 km) northwest
of the city of Chernobyl (Ukrainian: Chornobyl) and 65 miles
(104 km) north of Kiev, Ukraine. The station consisted of
four reactors, each capable of producing 1,000 megawatts of
electric power; it had come on-line in 1977–83.
Photo: Red indicates the extent of the radiation
cloud on April 27, just after the accident in Chernobyl. Blue,
indicates its almost worldwide distribution until the 6th
The 2005 report prepared by the Chernobyl
Forum, led by the International Atomic Energy Agency (IAEA)
and World Health Organization (WHO), attributed 56 direct
deaths (47 accident workers, and nine children with thyroid
cancer), and estimated that there may be 4,000 extra deaths
due to cancer among the approximately 600,000 most highly
exposed and 5,000 among the 6 million living nearby.
The Chernobyl reactor is now enclosed in a large
concrete shelter which was built quickly to allow continuing
operation of the other reactors at the plant. However, the
structure is not strong or durable.
Radioactive material from the Chernobyl
reactors is expected to last for 100,000 years, and the long-term
costs in human life and health are still unknown. (enlarge
Some major work on the shelter was carried
out in 1998 and 1999. Some 200 tonnes of highly radioactive
material remains deep within it, and this poses an environmental
hazard until it is better contained.
A New Safe Confinement structure will be built
by the end of 2011, and then will be put into place on rails.
It is to be a metal arch 105 meters high and spanning 257
metres, to cover both unit 4 and the hastily-built 1986 structure.
The Chernobyl Shelter Fund, set up in 1997, has
received EUR 810 million from international donors and projects
to cover this project and previous work. It and the Nuclear
Safety Account, also applied to Chernobyl decommissioning,
are managed by the European Bank for Reconstruction and Development
This photo, taken by Knoth in Minsk, Belarus: Twin brothers
Michael and Vladimir Iariga, 16 years old. Michael, with hydrocephalus,
is five minutes older than Vladimir, who is deaf.
As of 2006, some fuel at units 1 to 3 remained
in the reactors, most is in each unit's cooling pond, and
some in a small interim spent fuel storage facility pond (ISF-1).
In January 2008 the Ukraine government
announced a 4-stage decommissioning plan which incorporates
the above waste activities and progresses towards a cleared
The Shelter Implementation Plan calls for transforming
the site into an ecologically safe condition through stabilization
of the sarcophagus, followed by construction of a New Safe
Confinement (NSC). While original cost estimate for the SIP
was US$768 million, the 2006 estimate is $1.2 billion. (enlarge
The SIP is being managed by a consortium of Bechtel,
Battelle, and Electricité de France, and conceptual design
for the NSC consists of a movable arch, constructed away from
the shelter to avoid high radiation, to be slid over the sarcophagus.
The NSC is expected to be completed in 2012, and will be the
largest movable structure ever built.
week marks the 22nd anniversary of the Chernobyl nuclear accident—the
worst nuclear accident in history—which affected millions
of people, contaminated huge tracts of farmland, cost hundreds
of billions of dollars to clean up and mitigate, and redefined
the international debate over the safety of nuclear energy.