"Assuming there are 500 reactors in use in the world, the above CDF estimates mean that, statistically, one core damage incident would be expected to occur somewhere in the world every 40 years for the 2003 European Commission estimated average accident rate or every 100 years for the 2008 Electric Power Research Institute estimated average accident rate." [1]
"5 serious accidents in 60 years represents an actual historic global annual risk of 1/12 or 8.3% per annum" [2]
"If no cooling system is working to remove the decay heat from a crippled and newly shut down reactor, the decay heat may cause the core of the reactor to reach unsafe temperatures within a few hours or days, depending upon the type of core."
"5 serious accidents in 60 years represents an actual historic global annual risk of 1/12 or 8.3% per annum" [2]
"If no cooling system is working to remove the decay heat from a crippled and newly shut down reactor, the decay heat may cause the core of the reactor to reach unsafe temperatures within a few hours or days, depending upon the type of core."
[1] https://en.wikipedia.org/wiki/Core_damage_frequency
[2] https://silo.tips/download/complexity-implies-unknowable-ris...
[3] https://en.wikipedia.org/wiki/Decay_heat