The aftermath of the Chernobyl disaster, which occurred on 26 April 1986, caused panic around the world after a safety test at the Cherniox Nuclear Power Plant in Ukraine went horribly wrong during a test to simulate an accidental loss of power, causing a thermal reaction when the cooling system was offline and a reactor meltdown. The resulting explosions and resulting radioactive cloud were particularly felt in the area around Chernobyl, particularly in the "model city" of Pripyat. The Soviet Union's civil defence network was mobilized to deal with the disaster, bringing in 500,000 military and civilian personnel to clean up the radioactive aftermath. The clean-up took many months and the vehicles themselves became a toxic problem with no quick fix due to the radiation they were too dangerous to return to service out of the zone. The vehicles were left to rusting in the open air for at least 100 years until radiation levels fell to normal levels. The area became a tourist attraction when the area became one of Ukraine's unlikely tourist attractions in the late 1990s and early 2000s.