Lets just get the facts straight, using this data that 200GJ of energy is required for a melt through we can then calculate using the formulas provided that the time for melt through is using Po=1380MW
0 minutes after shut down - 4hours
01 hours after shut down - 5 hours
02 days after shut down - 11 hours
30 days after shut down - 26 hours
60 days after shut down - 36 hours

It's pointed out that that is time for fuel melt rather than melt of core through the bottom

Any idiot can face a crisis - it's day to day living that wears you out.