The cooling requirements of CAND reactors after the reactors are shut down are as follows:
Cooling systems need electricity to operate. Under normal operation, they get their electricity from the same power grid as the rest of us.
Nuclear power plants in Canada are also equipped with multiple sources of backup power if they get disconnected from the grid.
Sources of backup power include onsite power - that is, the power produced by the plant itself. [This is not allowed by safety regulations in most countries [i.e. USA] when a loss of offsite power (LOOP) occurs]
In addition, the following are available:
Two or three standby power generators [non-safety related]
Two or three emergency power generators [safety related]
Emergency batteries [sized for only 4-8 hours without charging]
[These diesel generators require diesel fuel and cooling water]
You can learn more by watching what would happen in the very unlikely event of a total station blackout – the situation that led to the Fukushima accident following the large tsunami that destroyed all available power sources onsite.
http://nuclearsafety.gc.ca/eng/reactors/power-plants/nuclear…
Jaak