Claiming it is safe and clean when it requires demonstrably superhuman effort to keep it both safe and clean is a weird argument IMO.
So to throw out the entire nuclear industry just because seems like a weird argument IMO.
Three Mile Island was a relatively safe reactor with a (partial) meltdown, which didn't cost that much, and is going to go back into production decades later. Fukushima, too, was a relatively safe reactor that caused a (partial) meltdown, but a massive financial burden.
It's debatable how much of that cost is truly necessary.
If this would've happened in the fossil fuel world, the cleanup would've been in the low billions instead of >$100B.
I would argue deep horizon was ecological a disaster several orders of magnitude worse than Fukushima, yet it cost several orders of magnitude less in cleanup.
It's almost as if we apply different scales to different energy sectors.
The first one was built in 2021 and went into commercial operation in 2023: https://www.ans.org/news/article-6241/china-pebblebed-reacto...
It was conceptualized in the 50s: https://en.wikipedia.org/wiki/Pebble-bed_reactor
But there were a number of limiting factors that led to people building reactors that could meltdown, but were incredibly unlikely - see Fukushima - it didn't technically meltdown - even in a VERY bad scenario with a good bit of human error.
Meltdowns are also not the only risk. That Wikipedia article says the PBR concept was used in the AVR reactor and still resulted in a non-meltdown accident that contaminated the groundwater with radioactive substances. Again they couldn't attribute deaths to it, but the main article https://en.wikipedia.org/wiki/AVR_reactor makes it look like an expensive mess with many accidents and protocol breaches. 1966 though; hopefully they've learned.
They don't need fanatical attention to active cooling, but they do instead need fanatical control of the atmosphere near the reactor to prevent fires, for example.
The first prototype was built in Germany in the 60s. It was closed in 1988, had to be bailed out by the German government in 2003 and has of course been a continuous money drain on German taxpayers ever since.
Nice summary here: https://en.wikipedia.org/wiki/AVR_reactor
From basic principles one might consider that anything that generates enormous amounts of power in a concentrated area can never be truly safe. All that energy is always a potential disaster.
Power plants that generate less power but are cheaper to make and can be distributed over a large area to ensure redundancy is a better strategy for both safety and reliability.