The Three_Mile_Island_accident in 1979 could have been so much worse.
https://www.nrc.gov/info-finder/decommissioning/power-reactor/three-mile-island-unit-2.html
https://en.wikipedia.org/wiki/Three_Mile_Island_Nuclear_Generating_Station#Seismic_risk
https://www.nbcnews.com/id/wbna42103936
https://en.wikipedia.org/wiki/Three_Mile_Island_Nuclear_Generating_Station#Three_Mile_Island_Unit_2
https://en.wikipedia.org/wiki/Nuclear_meltdown#Causes