The horrific disaster of 1986, known as the Chernobyl nuclear disaster, took place in Ukraine on April 25th.
The power plant exploded and lead to the deaths of approximately 30 people. The explosions resulted in hundreds of thousands of people having to evacuate from their homes in the surrounding of Ukraine. The wildlife in the area was also harmed by the huge amounts of radiation propelled into the atmosphere. As a result of this accident, research needs to be done in order to determine the real effects to date of this disaster. This nuclear catastrophe has been the worst nuclear disaster in the history of the human race and deserves an explanation and possible ways to avoid another disaster like its kind.
“The Chernobyl Power Complex” was a nuclear power plant in Ukraine located one hundred and thirty kilometers north of Kiev, Ukraine and about twenty kilometers south of the border of Belarus. The power complex consisted of four nuclear reactors, the reactors used at this power complex were models RBMK-1000. They were pressurized water-cooled reactors with individual fuel channels that used graphite as its moderator. The reactors were used for plutonium and power production not just plutonium production like other reactors were. The reactors worked how most coal or gas fired power stations did. The design of the RBMK-1000 reactors was very poorly made and unusual which most likely is a leading cause to the accident. The control rod design was unsafe as well as the positive void coefficient.
The Chernobyl Power Complex was created for a clean and efficient way to boil water to produce steam that drove turbine generators to create power. The four reactors each had their own unit. Unit one and two which each contained the corresponding reactor one and two were constructed between 1970 and 1977, and unit three and four contained the corresponding reactor three and four that were constructed in 1983 with the same design as all the other reactors. Two more reactors were in the process of being constructed in 1986 at the time of the disaster but were never completed due to disaster. Located southeast of the power plant an artificial lake twenty two square kilometers was constructed to provide cooling water for the reactors. Within a thirty kilometer radius of the powerplant the total population was approximately one hundred and fifteen thousand to one hundred and thirty five thousand at the time of the accident, who were all impacted by this disaster. The accident itself, happened on April 25th 1986 after a routine shutdown. The reactor crew at unit four where reactor four was located began preparing for a test that would determine how long the turbines would spin and supply power for in a loss of main electrical power.
Basically they were trying to determine how long the reactor would produce power for in an emergency situation that resulted in a power outage. The same test occured the year prior but the time that the power was supplied for without a main electrical source ran to quick. They had made changes to try and fix the problem and were running the test again to see if what they had tried worked.
An operator action took place and the automatic shutdown mechanism was disabled prior to this test. During the test very hot fuel came into contact with the cooling water and led to a fuel fragmentation along with rapid steam production and an increase in pressure damaging multiple assemblies within the reactor. The design of these reactors were made so that if there was damage to three or four assemblies it would result in destruction of the reactor which is what happened. The increases pressure cause the cover plate of the reactor to detach and ruptured several fuel channels and jammed the control rods. As a result intense steam generation accumulated and spread throughout the whole core causing the steam explosion releasing fission products into the atmosphere.
Two to three seconds after the explosion a second explosion three fragments from fuel channels and hot graphite into the air. The graphite is estimated to have been ejected air borne and led to fuel spewing out all over the place starting a number of fires within the plant. This caused the main release of radioactivity into the atmosphere.
Two hundred to three hundred tonnes of water was poured per hour following immediately after the explosion but was halted after half a day with fears of flooding the other reactors in the other units. Unfortunately two workers died during these explosions. The 1991 report by state committee on the supervision of safety in industry and nuclear power looked into the accident and noted that operators had placed their reactor in a dangerously unstable condition.
The chernobyl accident had many immediate impacts, it caused serious social and economic disruption in Ukraine. The accident caused the largest uncontrolled radioactive release into the air ever recorded with the release of radioactivity airborne ongoing for approximately ten days. All of the xenon gas in the reactor, half of the iodine, a lot of caesium and at least five percent of radioactive material were all released from unit four during the accident. The one hundred and sixteen thousand people affected were located in areas of Ukraine, Belarus, Russia and to some extent over Scandinavia and Europe, a total of twenty nine thousand and four hundred square feet was contaminated. The radioactive material spread by dust and wind. Everyone within a thirty kilometer radius were evacuated and relocated. Twenty eight people confirmed by scientific proof died due to the radioactivity although several other cases of casualties led towards causes of this disaster but no prove abides by it.
Six of whom were firefighters who attended the initial fires on the roof the of plant during the disaster. The task following the explosions was to clean up the radioactive materials on the site so that the other three units could be restarted. Two hundred thousand people from all over the soviet union were involved in the clean up over a year period. They all received high doses of radiation being right of the site only days after. Later the two hundred thousand turned into six hundred thousand but the new four hundred thousand were not exposed to as high of radiation by that time. The effects of radiation exposure fell into two main classes, one being deterministic effects, where the effect is certain to occur under given conditions (example: individuals exposed to several grays over a short period of time will definitely suffer Acute Radiation Syndrome) the second being stochastic effects, where the effect may or may not occur (example: an increase in radiation exposure may or may not induce a cancer in a particular individual but if a sufficiently large population receive a radiation exposure above a certain level, an increase in the incidence of cancer may become detectable in that population). Long term effects were also a result of the Chernobyl disaster. Studies based on over one million people who were located within the thirty kilometer radius of the accident and outside of the thirty kilometer radius occurred later on down the road.
These studies were to try to see the effects long term of the exposure to radiation during the explosion. By the year of 2000, four thousand cases of thyroid cancer exposed in children who were located within or nearby the accident accumulated but nothing could prove that the cancer led back to the radioactivity in the air. In April 2005 reports by two expert groups “Environment” from the IAEA and “Health” from the WHO were in line with earlier expert studies, notably the UNSCEAR 2000 report which stated that “apart from this thyroid cancer increase, there is no evidence of a major public health impact attributable to radiation exposure 14 years after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality or in non-malignant disorders that could be related to radiation exposure.” Although many believe that is was indeed the radioactivity that was the cause even without scientific proof. Many people believed that is was a lack of reliable public health knowledge that led to no proof. Some doctors in Ukraine and Europe advised abortions to pregnant women just in case of the radioactive materials they had inhaled and could pass on to their children.
In early 1900 around four hundred million dollars was spent on improvements to the three remaining reactors at the plant to enhance safety. But in 1991 unit 2 was shut down due to a turbine hall fire. In 1995 it was announced that the 2 remaining reactors would be shut down by the end of 2000 and a memorandum of understanding was signed. Unit 1 shut down towards the end of 1997 and uit 3 shut down in 2004 excelling the 2000 date. It took until 2004 because the generating capacity to shutdown the last rector was needed and not made accessible until 2004.
Chernobyl unit four was enclosed in a large concrete shelter which was built by October 1986 to allow continuing operation of the other reactors at the plant. But the structure was not strong or durable. Approximately 200 tonnes of highly radioactive material remained deep within the shelter and posed an environmental hazard until it was better contained. In 2017 The New Safe Confinement (NSC) structure was completed. It was built and then moved into place on rails. It had an arch one hundred and ten metres high, one hundred and sixty five metres long and spanning two hundred and sixty metres, covering both unit four and the 1986 structure priory built.
The arch frame was equipped with internal cranes. The design and construction contract was signed in 2007. The Novarka consortium and preparatory work onsite was completed in 2010. Construction started in April 2012. The NSC was and continues to be the largest moveable land based structure ever built. The sealed building allows engineers to remotely dismantle the 1986 structure that has shielded the remains of the reactor from the weather since the weeks after the accident. It enabled the eventual removal of the fuel containing materials in the bottom of the reactor building and assemble for disposal.
This task represented the most important step in eliminating nuclear hazard at the site.