Canada

You may have misunderstood my focus, I agree that current nuclear reactors are designed with utmost safety and redundancy on top of redundancy. However, all those safety measures multiply feasibility, development and operating costs while also increasing the surface area of things that may be mismanaged/ignored/forgotten and not be immediately detected by external auditor/inspector if there is any at all.

As I have written previously:

Theorically, we all know and understand that following all the baseline protocols and maintenance schedules rigorously will keep a nuclear fission power plant working without environmental/health/safety issues for its entire entended life cycle.

Obviously, I absolutly hope and want nuclear technology to develop further. However, I do not think currently available options are cost effective and durably suitable for a world of increasing climate change perturbations. Governments, institutions and organizations will be stretched thin and thinner by multiple factors while increasing demands and sequences of societal and climatic events will test their ever changing priorities.

Nevertheless, one fission technology that may show promise in an increasingly turbulent world are small self-contained reactors. From my understanding, they are deployed in situ and buried providing energy to a nearby facility until its fuel has reached a predetermined end-of-life cycle. The self-contained reactor is then dug out and replaced by a new one while the EOL reactor is returned to be "recycled" and redeployed elsewhere. It seems simpler, hopefully also cost effective and a smaller safety concern overall.

As you have also pointed out with Fukushima having been slated to be decommissioned, political prerogative pushes thing far beyond what was intended. Be it old bridges collapsing way beyond their lifespan, or old submarines killing their crew from a fire onboard, or old fleet of gas guzzling trucks still belching a mix of burnt and unburned fuel particles, the list goes on forever. Even if we built the safest, most redundant, almost completely automated nuclear power plant that could last a hundred or two hundred years, how future governments deals with the decommission is entirety subject to their whims and changing political context.

And we can already witness hiccups of various degrees in every single countries since even before the pandemic, with changing political situation due to several interconnected factors in which climate change is a threat multiplier.