Interestingly hunterston - a nuclear power station on the west coast of Scotland - had a failure of its backup diesel generators. Wikipedia describes it as:
> In December 1998, an INES Level 2 incident occurred after severe winds and sea spray disabled all four power lines to the site during the Boxing Day Storm of 1998. After multiple grid failures in a short period of time, emergency diesel generators failed to start. Normally, in the absence of power for the reactor cooling pumps, the reactor would be passively cooled. However, the emergency control system which would have initiated passive cooling failed to act, as it had not been reset. Reactor cooling was reinstated after four hours.
It seems the safety margin was twenty hours of no reactor cooling.
Well, "passive cooling" means that it requires no external power to cool. Doesn't necessarily mean it's normally plumbed into the circuit. Most probably it would not normally be, as the passive cooling would definitely decrease the power output (it is, after all, what it is designed to do).
So there was probably one or more valves that did not get switched, as the system somehow didn't think they needed to, due to something not being configured as they should.
> In December 1998, an INES Level 2 incident occurred after severe winds and sea spray disabled all four power lines to the site during the Boxing Day Storm of 1998. After multiple grid failures in a short period of time, emergency diesel generators failed to start. Normally, in the absence of power for the reactor cooling pumps, the reactor would be passively cooled. However, the emergency control system which would have initiated passive cooling failed to act, as it had not been reset. Reactor cooling was reinstated after four hours.
It seems the safety margin was twenty hours of no reactor cooling.
Wikipedia: https://en.wikipedia.org/wiki/Hunterston_B_nuclear_power_sta...