Chernobyl Essay, Research Paper
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 monitor the mechanical stability of the structure and vibration of major components. All these sensors are under computer control. Systems designed to balance any changing conditions have also been activated. These include the injection of chemicals to prevent nuclear leakage and to pump excess water leaking into the sarcophagus.
An enormous effort was required to mount the clean-up operation; decontaminating ground and buildings, enclosing the damaged reactor and building the Sarcophagus was a formidable task, and it is impressive that so much was achieved so quickly. At that time the emphasis was placed on confinement as rapidly as possible. Consequently, a structure that would effectively be permanent was not built and the Sarcophagus should rather be seen as a provisional barrier until a more permanent solution for the elimination of the destroyed reactor and the safe disposal of highly radioactive materials. In these conditions, to maintain the existing structure for the next several decades pose very significant engineering problems. Studies are currently underway to solve this problem.
Nine years after its completion, the sarcophagus, although still generally sound, raises concerns for its long-term stability. Some supports for the enclosure are the original Unit 4 building structures, which may be in poor condition following the explosions and fire, and their failure could cause the roof to collapse. This situation is added upon by the corrosion of internal metallic structures due to the high humidity of the Sarcophagus. This humidity was produced by the penetration of large quantities of rainwater through the numerous cracks that were present on the roof and were only recently repaired.
The structure is not designed to withstand earthquakes or tornadoes. There is also considerable uncertainty on the condition of the lower floor slab, which was damaged by the penetration of molten material during the accident. If this slab failed, it could result in the destruction of most of the building.
A number of potential situations have been considered which could lead to breaches in the Sarcophagus and the release of radiation into the environment. These include the collapse of the roof and internal structures, a possible criticality event, and the long-term migration of radionuclides into groundwater. Leaching of these radionuclides may also become more significant as time passes. The envelope is not leak-tight but that situation has been recently improved. However, there are currently over 3000 cubic meters of water in various rooms in the sarcophagus. Most of which entered through defects in the roof.
Perhaps the situation causing most concern is the effect that the collapse of the Sarcophagus might have on the reactor Unit 3. There is ever-present danger in the operation of this reactor too. Despite a government plan to shut down the entire plant, no. 3 was reactivated after officials pleaded that its energy was essential for the coming winter. Today the reactor is still producing power and is connected to the Sarcophagus through the “V” Building, which is not very stable. Like its demolished twin, reactor 3 is considered fundamentally unsafe by the International Atomic Energy Agency. The plant is even less safe now that the people who are left to run it are poorly trained, badly paid, and demoralized.
The accident recovery and clean-up operations have resulted in the production of very large quantities of radioactive wastes and contaminated equipment. Some of these radioactive wastes are buried in trenches or in containers isolated from the groundwater by clay or concrete screens within the 30-km zone. Six hundred to eight hundred waste trenches were hastily dug in the immediate vicinity of Unit 4 in the aftermath of the accident. These unlined trenches contain the radioactive fallout that had accumulated on trees, grass, and in the ground to a depth of 10-15 centimeters, which was bulldozed from over an area of roughly 8 kilometers square. There is also a large number of contaminated equipment, engines and vehicles stored in the open air. Much of this equipment has been stolen and looted. Among this contaminated equipment are the helicopters used to dump materials into the reactor well. The pilots of these aircraft have since died from such heavy radiation exposure. Despite this knowledge, at least 700 peasants have returned to the town of Chernobyl. Here these people eat contaminated animals and produce. Some say they would rather die here than live elsewhere.
Groundwater contamination is on the rise mostly due to the construction of a wall in 1986 (3.5 km long and 35 m deep) around the reactor to prevent contamination from reaching the Kiev reservoir, and the leaking of drainage connected with the construction of new buildings on the site. While studying the water contamination, it was also been discovered that 32 of 43 explored trenches are periodically or continually flooded, greatly increasing the migration of radionuclicides. The mobility of strontium-90 is especially important in that, from the closest trenches, it might reach the Pripyat River in 10 to 20 years. It is clear that that a large effort needs to be made to monitor unexplored disposal
sites and the movement of water. The problem of the potential spread of radioelements to the Pripyat River is very important because it may act as a shortcut for the dispersion of additional radioactive elements outside the 30-km exclusion zone.
In general, it has been determined that the Sarcophagus and the waste storage sites in the area are a potential source of further releases of radiation. However, any accidental releases from the Sarcophagus are expected to be very small in comparison with those from the 1986 accident and the contamination would be limited to a relatively small area around the site. On the other hand, concerns have been expressed by some experts that a more drastic release might occur if the collapse of the Sarcophagus should induce damage in the Unit 3 of the Chernobyl power plant. As for the wastes stored in the area around the site are concerned, they are will require close monitoring until a safe disposal has been made.
Actions are being taken internationally to study a solution leading to the elimination of residual contamination on the site. It has been estimated that it will take 200 years to eliminate all effects of the accident and that the final price tag on disaster will be around $400 billion. Hopefully the world has learned a great deal from this horrifying mistake. And that all needed effort will be put into effect to put things back to normal.