The Chernobyl disaster on April 26, 1986 is described as one of the most
frightening environmental disasters in the world. The plant was made up of four
graphite reactors, which were the most modern Soviet reactors of the RBMK-type.

Two more of these reactors were still under construction at the station.

Chernobyl was an obscure town in north central Ukraine (former Soviet Union) on
the Pripyiat River near the Belarus border. Immediately its name was joined to
the Nuclear Power Plant located twenty-five kilometers upstream. The plant is
actually located fifteen kilometers northwest of the city. It is not only the
radioactive mess left that strikes fear. Nineteen similar stations are still
running, because neither the former Soviet Union nor its republics can afford to
shut them down. The world first learned of this accident from Sweden, where
unusually high radiation levels were noticed at one of their own nuclear
facilities. At 1:23 am technicians at the Chernobyl Plant took some erroneous
actions that will impact the course of Soviet events without exaggeration. Human
error is what basically caused the disaster. These operators of the fourth unit
slowly allowed power in the reactor to fall to low levels as part of a
controlled experiment gone wrong. The purpose of the test was to observe the
dynamics of the RMBK reactor with limited power flow. Twelve hours after power
reduction was initiated, power reached 50 percent. Only one turbine was needed
to take in the decreased amount of steam, so no. 2 was turned off. Power was
then reduced to 30 percent. One of the operators made a mistake. Instead of
keeping power at 30 percent, he forgot to reset a controller, which caused the
power to plummet to 1 percent. Now water was filling the core, and xenon (a
neutron absorbing gas) built up in the reactor. The power was too low for the
test. The water added to the reactor is heated by the nuclear reaction and
turned into steam to turn the turbines of the generator. The operator forced the
reactor up to 7% power by removing all but 6 of the control rods. This was a
violation of procedure and the reactor was never built to operate at such low
power. This type of reactor is very unstable when filled with water. The
operator was not successful in getting the flow of water corrected and the
reactor was getting increasingly unstable. The operator disabled emergency
shutdown procedures because a shutdown would abort the test. By 01:22 AM, when
the operators thought they had stable conditions, they decided to start the
test. The operator blocked automatic shutdown because of a fear that a shutdown
would abort the test and they would have to repeat it. The test began and the
remaining turbine was shut down. Power in the reactor began to gradually rise
because of the reduction in water flow caused by the turbine shutdown, which
lead to an increase in boiling. The operator initiated manual shut down, which
lead to a quick power increase due to the control rod design. The reactor
reached 120 times its full power. All the radioactive fuel disintegrated, and
pressure from all excess steam broke every one of the pressure tubes and blew
the entire top shield of the reactor. All of these factors including serious
violations of safety operations, dangerous design flaws, and imperfect control
systems is what led to the virtually instantaneous catastrophic increase of
thermal power which led to core meltdown. The steam explosion also destroyed
part of the building. Radioactive material was then thrown out into the
atmosphere for over 10 days. Multiple fires were formed both inside and out of
the reactor. By five o'clock the firemen had smothered the flames. In later
days, about 5000 tons of materials were thrown into the reactor well from
helicopters of the air force to extinguish burning graphite and suppress
radiation release. The flow of different substances continued until the
beginning of June 1986. It is still not clear if the dumping of these materials
actually achieved their goal. Recent data has shown only a small part of the
materials actually got into the well. Due to the accident, the people of

Chernobyl were exposed to radioactivity 100 times greater than the Hiroshima
bomb. The people of the world and Northern Europe were greeted with clouds of
radioactive material being blown northward through the sky. Seventy percent of
the radiation is estimated to have fallen on Belarus and 10 years later babies
are sill being born with no arms, no eyes, or only stumps for limbs. No one can
predict the exact number of human victims. It is estimated that over 15 million
people have been victimized by the disaster in some way. It has also estimated
that ultimately the accident will claim more victims than World War II. It will
cost over 60 Billion dollars to make these people healthy. Thirty-one lives were
lost immediately, and more than 600,000 people were involved with the cleanup.

Many are now dead or sick. Hundreds of thousands had to abandon entire cities
and settlements within the thirty-kilometer zone of highest contamination.

Possibly as many as three million still live in contaminated areas. Ten thousand
of these are still living in the city of Chernobyl today. Huge sums of many have
been spent, and will continue to be spent to relocate settlements and
decontaminate the once rich farmlands. Chernobyl has developed as an icon for
the terror of uncontrolled nuclear power and abilities, and for Soviet deception
and inability to provide safe conditions for workers and basic services such as
transportation and health care, especially in times of greatest need. The
catastrophe also halted a highly potential nuclear program. The impact of the

Chernobyl Accident on a Nuclear Energy Policy is tremendous. Some countries
stopped national nuclear energy programs. Construction of new plants in the

Soviet republics were frozen. Public opinion was directed against nuclear power
plants. Some plants were even shut down, but have now been reactivated. The
accident has also initiated an international activity in the area of nuclear
safety and nuclear emergency planning. Many countries started a development of
decision support systems for nuclear accident cases. The way in which Soviet
leaders have dealt with the situation is very unsettling. In the aftermath of
the catastrophe several designs to encase the damaged reactor were reviewed. The
option that was selected included the construction of a massive structure in
concrete and steel that used what remained of the reactor walls as support. Its
construction is considered one of the most complicated building works in the
world. In charge of building the tomb was Construction Department No. 605. They
ran into many problems while constructing the massive concrete and steel shell.

Concrete blocks for the tomb were pieced together far from the reactor itself,
and the roads entering the facilities were not accommodated for such loads,
which made it difficult for the drivers. Once the blocks were delivered, the
workers needed to put them in place. Each weighed several dozen tons so
eventually crane operators had to perform this task. This outer protective wall,

28 stories high, is placed around the perimeter and other walls connected to the

Unit 3 reactor. A steel roof then completed the structure. The destroyed reactor
was entombed in a 300,000-ton concrete structure known as the
"shelter" or "envelope." In conditions of high radioactivity
the mammoth task was completed in seven months, in November 1986. The site
around the plant had then been announced safe for about the next thirty years.

However today the sarcophagus is cracked and crumbling. Some of these cracks are
as large as a garage door. Multiple sensors were placed to monitor levels of
gamma radiation, neutron flux, temperature, heat flux, as well as the
concentrations of hydrogen, carbon monoxide and water vapor in the air. Other
sensors monl On the whole, there are some different points and aspects from the
authors to explain the effects of immigration on labor market. They are the
demand and supply, investment, expenditure form government, skilled immigrants,
mobility and the empirical findings. Although there are both advantages and
disadvantages from immigration, most authors believed that there is no causal
link between immigration and unemployment. However, it is possible that they
emphasized the benefits and gave insufficient attention to the costs of
immigration on the labor market. In my view, government should consider more
aspects from the effect of immigration on labor market for making the policy
well. Also, government should not put most responsibilities of unemployment on
immigration in order to escape the blame from high unemployment because it is
not fair to the contribution from immigration and make an unreal image of
immigration to society.