The nuclear power plant near Harrisburg, Pennsylvania, that became site to one of the most serious nuclear power accidents in US history. On March 1979, human errors and mechanical failures caused a partial meltdown of the nuclear core–releasing radioactive gases into the environment. Although large amounts of radiation were released, the resulting exposure of the public was relatively slight, resulting mainly from xenon-133 that was present in the gaseous plume. Despite assurances of very little public risk, the accident a Three Mile Island increased public fears about the safety of nuclear power. Public opposition has been so strong, that to-date, there have been no new construction of nuclear power plants in the US since the Three Mile Island incident.