Then the plymouth reactors don’t have backup diesel/ natural gas generators on site? They get auxiliary power only from off site? Sounds odd.
The diesel generators are for emergency use. The idea is to not get in a situation where you need them, in case THEY fail or you run out of fuel, etc. If you have no grid power and then your diesel generators quit for whatever reason you are screwed.
Look at what happened in Japan when they lost the generators.
The safety protocol says if you lose grid power you shut down in an orderly and safe fashion.
It is sort of like having a UPS for your computer: if the power goes out you use the power from the UPS to shut down your computer in an orderly fashion so as not to lose data. You don’t continue merrily along until the battery dies.
Same idea with a nuke.
Not everything is a conspiracy.