Chernobyl, Ukraine was once home to four Soviet nuclear reactors. The key word here is “was.” In the early morning of April 26th, 1986 there was an explosion inside the fourth reactor that led to massive amounts of radiation being released into the atmosphere. To this day there is an “exclusion zone” in Chernobyl that is off limits to the public.
The explosion occurred due to both human error and design flaws. There was a power surge that ruptured a few pressure tubes which contained uranium dioxide fuel. When the tubes ruptured the hot fuel mixed with water and caused a steam explosion. This explosion lifted the 1,000-metric-ton (2,204,622lb) cover off the reactor which ruptured the remaining pressure tubes and caused a second explosion. After the second explosion the core of the reactor was exposed to the environment. 
For 10 days a fire burned at the site and it is estimated that up to 30 percent of the 190-metric-tons (4,188,781lbs) of uranium dioxide fuel was released into the atmosphere. 335,000 people had to be relocated from Chernobyl after the disaster.  Thirty-eight people died immediately in the explosion and it is believed that up to 100,000 people died from radiation exposure in the aftermath.  This does not include the number of deformities in children born after the disaster and the environmental mutations around the site.
Mikhail Gorbachev, the leader of the Soviet Union at the time, suffered severe consequences as a result of the disaster. His first problem was that he failed to address the nation until three weeks after the explosion. While his administration made comments about it within the following days they lacked details.  They downplayed the incident as well. On May 1st the Council of Ministers claimed that only two people had died and that the situation was being dealt with. They even blamed “certain Western press agencies” for making the incident out to be worse than it really was.  The poor reporting by the government “unleashed” the Soviet media’s investigative reporting. The press began not only reporting on the environmental consequences of the explosion but on other accidents within the Soviet Union as well. The disaster was also a huge economic toll on the Soviet Union between controlling the radiation and relocating the victims. Gorbachev had no choice but to welcome international help. Furthermore, it led the citizens of the Ukraine to resent the central authorities in Moscow. 
In 2006 Gorbachev recalled the impact that the Chernobyl disaster had on the breakup of the Soviet Union. He said “the nuclear meltdown at Chernobyl 20 years ago this month, even more than my launch of perestroika, was perhaps the real cause of the collapse of the Soviet Union five years later.” With the unleashing of the press, the disaster proved to him that his policy of glasnost, freedom of expression, must be continued. He acknowledged that the disaster ended the arms race because he couldn’t pay for both a building up of arms and a clean up of Chernobyl. Furthermore, after seeing the impact of the disaster on human lives Gorbachev took a stand against anyone having nuclear arms. 
The Chernobyl disaster led to the press revealing all of the Soviet Unions flaws. It bankrupt the country as well which forced the Soviet Union to work with the international community. It also led to the smaller countries within the Soviet Union to resent the central powers. This all led to the events of 1991 which saw the collapse of the Soviet Union.