Page "Three Mile Island accident" Paragraph 29

According to the official figures, as compiled by the 1979 Kemeny Commission from Metropolitan Edison and NRC data, a maximum of 480 petabecquerels ( 13 million curies ) of radioactive noble gases ( primarily xenon ) were released by the event.

However, these noble gases were considered relatively harmless, and only 481 – 629 GBq ( 13 – 17 curies ) of thyroid cancer-causing iodine-131 were released.

Total releases according to these figures were a relatively small proportion of the estimated 370 E Bq ( 10 billion curies ) in the reactor.

It was later found that about ½ the core had melted, and the cladding around 90 % of the fuel rods had failed, with of the core gone, and around of uranium flowing to the bottom head of the pressure vessel, forming a mass of corium.

The reactor vessel — the second level of containment after the cladding — maintained integrity and contained the damaged fuel with nearly all of the radioactive isotopes in the core.