There have been very few nuclear disasters, but the consequences are so massive that it outweighs the benefits. Both Chernobyl and Three Mile Island, two of the most infamous nuclear accidents, were caused by human error. Even if the safety procedures and equipment are perfect, there is no guarantee that a human operator will not make a mistake.
In the case of the Chernobyl disaster, the reactor released 400 times the amount of radioactive material as the atomic bomb dropped on Hiroshima during World War II.
This release was then carried across Europe and created hazardous health risks to the surrounding area. The radiation released affected an indeterminable number of people in the surrounding area, likely increasing their risk of cancer and other diseases.
Undeniably, nuclear energy has benefits. But the safety risks, no matter how small, of reactor failure, outweigh those benefits. Its time to leave nuclear power in the past.