Carbon dating is unreliable for determining the age of organic material because it relies upon there being no change in the ratio of C14 to C12 over millions of years, yet today we know there are fluctuations and current formation of C14 exceeds decay by about 38%.
Three Mile Island (1979, 13 to 17 curies released) was not the first! The first US nuclear accident was the explosion of a U.S. Army experimental reactor using HEU fuel on January 3, 1961 in Idaho Falls, Indiana. Three workers died and 80 curies of radiation were released.
Tests of things like nuclear aircraft engines starting in 1945 have spewed over 1 million curies of radiation into our atmosphere. (Three Mile Island released about 15 curies).
In 1986 K-219, a Russian submarine with 16 live nuclear warheads sank and landed 18,000 feet down about 400 miles east of the island of Bermuda. Corrosion may eventually lead to a massive nuclear chain reaction.