> in addition to the grid connection, there are four twelve megawatt diesel generator stations spaced around each corner of the plant -- each with two generators, any one of which is able to provide operating power to keep the reactor's safety systems working.
Unfortunately for Fukushima, all generators were flooded by a single Tsunami. What are the odds of an unknown event that will affect all generators? Think of EMP, contaminated fuel, a large cloud of C)2 suffocating the engines... All seem highly unlikely, but how do you plan for the unknown unknowns?
The most likely (and I think underestimated) risk for Nuclear plants is a systemic change due to a large (climate?) crisis and/or war. Think of the collapse of the Soviet Union, that definitely increased risk and reduced maintenance budget for a few Nuclear plants. Any significant sea level rise, drought or flood could very well trigger such events (even if the reactor is not affected directly, the society around it will be). That is why I think nuclear is a risky option to reach net-zero; every plant you build is a bet on the future stability of society for at least 75 years (time until the plant will be safely decommissioned by future generations). I would feel much safer in a world covered in solar panels, wind turbines and transmission lines (and highly variable spot pricing) than in one with nuclear plants that require constant care by experts and that even in the best case incur a huge cost on society to safely decommission.
> In 2016 the European Commission assessed that European Union's nuclear decommissioning liabilities were seriously underfunded by about 118 billion euros, with only 150 billion euros of earmarked assets to cover 268 billion euros of expected decommissioning costs covering both dismantling of nuclear plants and storage of radioactive parts and waste. France had the largest shortfall with only 23 billion euros of earmarked assets to cover 74 billion euros of expected costs [1]