What were the effects of the nuclear power plant accidents at Three Mile Island in Pennsylvania, Chernobyl in Ukraine, and Fukushima Daiichi in Japan?

• The 1986 accident at the Chernobyl nuclear power plant in Ukraine, then part of the former Soviet Union, is the only accident in the history of commercial nuclear power to cause fatalities from radiation. It was the product of a severely flawed Soviet-era reactor design, combined with human error. Much of the underlying circumstances were particular to the Chernobyl reactor and the Soviet government’s response.
• Key differences in U.S. reactor design, regulation and emergency preparedness mean that an accident like the one that took place at Chernobyl could not occur in the United States.
• The reactor built at Chernobyl is a RBMK reactor, which was never built by any country outside the USSR because it had characteristics that were rejected everywhere outside the Soviet Union. Chief among these was its inherent instability, especially on startup and shutdown. Because of the way the reactor used graphite where American reactors use water, when Soviet operators tried to reduce power the RBMK had a tendency to sharply increase power production instead. As overheating became more severe, power increased even more.
• Thirty-one people died within a few weeks of the accident from the initial steam explosion, exposure to radiation and thermal burns, and one due to cardiac arrest. 
• In 2018, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported that the accident also was responsible for nearly 20,000 documented cases of thyroid cancer among individuals who were under 18 years of age at the time of the accident in the three affected countries including Belarus, Ukraine and the Russian Federation. This was due to the high levels of radioactive iodine released from the Chernobyl reactor in the early days after the accident. Radioactive iodine was deposited in pastures eaten by cows who then concentrated it in their milk which was subsequently ingested by children. This was further exacerbated by a general iodine deficiency in the local diet causing more of the radioactive iodine to be accumulated in the thyroid. 
• Both the IAEA and UNSCEAR report that health studies of cleanup workers fail to provide a direct correlation between radiation exposure and an increase of any other forms of cancer attributable to radiation exposures. However, the psychological effects of Chernobyl remain widespread and profound resulting in suicides, alcohol abuse and apathy.
• Most emergency workers and people living in contaminated areas received relatively low whole-body radiation doses, according to a United Nations study published in 2008. The study found no evidence of increases in solid cancers, decreased fertility or congenital malformations. However, there is “some evidence of a detectable increase” in leukemia and cataract risk among workers who received higher radiation doses when engaged in recovery at the site. Long-term health monitoring of these workers is ongoing.

The Three Mile Island, Chernobyl, and Fukushima Daiichi nuclear power plant disasters had a tremendous impact on the environment, human health, and the future of nuclear power.

On April 26, 1986, a nuclear power plant in Pripyat, Ukraine, experienced the Chernobyl accident. It was brought on by a confluence of poor design, insufficient safety precautions, and human error. A great deal of radioactive material was spilled into the environment when the reactor detonated, starting a fire that lasted ten days. Two workers died as a direct result of the disaster, while many more died from radiation-related illnesses in the years that followed. Large tracts of land were also poisoned by the catastrophe, making them unusable for years to come. The catastrophe significantly altered public perceptions of nuclear power, and many nations reevaluated their nuclear energy strategies.

On March 28, 1979, a nuclear power plant in Middletown, Pennsylvania, experienced the Three Mile Island catastrophe. It resulted from a collision of faulty machinery, design flaws, and human error. Although the reactor did not blow up, radioactive gases and radioactive iodine were released into the environment as a result of the reactor core's partial meltdown. Although there were no immediate fatalities or injuries, the accident seriously damaged the plant and eroded public faith in nuclear power. As a result, the United States did not build any new nuclear power plants for decades.

On March 11, 2011, a nuclear power plant in Fukushima, Japan, experienced an accident known as the Fukushima Daiichi. The reactor's cooling system was harmed by a significant earthquake and associated tsunami, which caused three nuclear meltdowns and the release of radioactive material into the environment. Although there were no immediate fatalities or injuries as a result of the disaster, over 100,000 people had to be evacuated from the area. Significant negative effects on Japan's economy, society, and politics resulted from the accident, including a rise in public distrust of nuclear energy and a move toward renewable sources of energy. In general, these mishaps have brought to light the significance of safety precautions, emergency response strategies, and effective public relations in nuclear power operations. They have also prompted tighter oversight and control of nuclear power facilities as well as a push toward renewable energy as a more environmentally friendly and secure substitute.