“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 people affected were located in areas of Ukraine, Belarus, Russia and to some extent over Scandinavia and Europe. The radioactive material spread by dust and wind. 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.