Nuclear fission based reactors should be left for beyond Earth's orbit; for space exploration, space mining, etc.
On earth, it's more of a liability with multiple security/safety concerns that engineers, architects, scientists and risk management specialists have to contend with, thus making any project exponentially and unnecessarily more expensive. 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.
However, we live in an imperfect world where important things gets postponed, rescheduled, ignored out of inconvenience, forgotten due to changing priorities or changes in personnel/chain of command, or mismanaged simply due to political interference/apathy/nepotism/ignorance. All this is internal to its regular operation.
Externally, we have to constantly/actively monitor and react to natural disasters, accidents, terrorism, climate change (e.g. input water temperature), etc. So as to ensure operational integrity at all time.
In contrast, nuclear fusion based reactors have the potential to solve alone all our energy needs for the foreseeable future in a carbon neutral (even carbon negative) manner. However, the resources assigned to make a scientific breakthrough in that field is largely insufficient if not scrawny/famished. It is indeed several magnitudes more expensive, supply chain constrained (special custom equipments and parts), rife with delays, constantly over budget all while still trying to understand the fundamental science with experiments and scientists spread throughout the four corners of the planet.
We could accelerate the progress towards nuclear fusion power plants similarly to how we accelerated COVID-19 vaccine research & production, but it will require several times more financing into each potential fusion reactors designs and each of their successive prototypes (tokamak, stellarator, spherical tokamak, inertial confinement, liquid metal mediated magnetized target fusion, magneto-inertial fusion, etc…)
Can't say I agree with this at all. The thing about fission that people regularly mistaken about is how much actual waste there is, and how little of a deal it is. Not to mention that all the safety processes and security issues that you mentioned had been solved since the 70s or so. I mean, there's never been an incident in the entire world regarding nuclear fuel or waste being stolen. Only nations have ever produced a nuclear weapon, dirty or atomic.
And in regards to waste, the amount of high level nuclear waste that's been produced world wide is only a few dozen tons, all of which can be recycled and reused, cutting down the half-life from millions of years down to only a bit above 200 years, and reducing the total quantity of waste to only a fraction of the original amount. I mean, when people throw around all the nuclear waste numbers, they include low level waste as well, which include things like the radiation suits the workers wear while working near the reactor. Waste that become non-nuclear waste after a holding time of two months and are generally tossed with the trash like normal.
In addition, the worry about natural disasters is entirely a red herring for most nations that build nuclear reactors in the first place. The containment building of a nuclear reactor is designed to survive an actual missile strike. You could have a 747 dive bomb the nuclear plant, and it wont' crack the containment building. Nothing short of something on the level of a US bomber squadron dropping an entire flight of bombs, or a conventional nuclear weapon, directly on the plant will crack that thing. No natural disaster short of a magnitude 10.0 earthquake or a volcano sprouting underneath the plant will cause any decent nuclear plant to leak radiation.
And if you're going to mention Fukushima as a counter example, then let me remind you, that it took a direct hit from both an earthquake and a tsunami to disable the plant (the containment building didn't even crack from that), and the backup generator room drowning for a good 2 weeks without a single nuclear technician not being able to enter the entire city for that duration before the critical explosion happening. The damn reactor, a design that was considered flawed due to putting the generator room underneath the plant instead of above it like the original recommendations to lower the risk of terrorists that the US was worried about in the 70s in a nation without a history of terrorism before the 90s, managed to survive without power for its cooling systems nor any technicians to repair anything for 2 weeks. And to make matters worse, the Fukushima plant was actually slated to be retired a decade before it due to being too old, but was pushed to stay online until a newer plant could be built, so it was even way past its decommission date on top of every other factor going against it. And the worst that happened was a slight elevation of radiation for that one year, and the current discharge of tritium that is magnitudes lower than the amount that pretty much any nuclear plant discharges during normal operations. Far lower than the amount that anyone who sources water from Lake Ontario or the St Lawrence drinks on a regular basis, for example.
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.
The thing is that people have a terrible level of patience in regards to long term benefits. For example, people constantly advocate for wind and solar, yet both only last ten years before having to be replaced. And as an alternative, natural gas is often proffered and employed, yet they only last about 20 years before being replaced. Nuclear fission plants have a typical lifespan of 60 years, with even existing plants having a theoretical lifespan of over 100 if the will to continuously refurbishing them exists. As things stand, we actually don't have a single source of energy as cost efficient as nuclear fission as things stand aside from hydro. It's just that it also has the single greatest initial investment cost as well, and won't be paid back during the term of any administration that commissions it, as even in the best case scenario, they take 6 years to build, and can often take more than 10.
I do agree that SMRs are a great next step for nuclear as well as power generation in general, but they are also only a stepping stone. They only last 5 years or so before having to be replaced (as they generally cannot be refueled). But at the same time, we can survive using only stepping stones for the next few decades until a better alternative (aside from full scale fission) rounds the corner. I do hope fusion ends up being that power source, but traditional fission (as well as the newer advances in fission) are still one of the most cost effective, efficient, reliable, and safe. They just have a high political hurdle to face, as people fear what they don't understand and there is no power source right now that people understand less than nuclear.