OK.

So ... WHY are there so many regulations and safety procedures? Is this political fluff? Pure overhead? I don't think so. It is inherent to the nature of a solid fuel rod reactor, the incidence (and fear) of meltdowns, and the fear of nuclear waste.

What is a nuclear meltdown. In solid fuel reactors a nuclear chain reaction is induced, so an atom of nuclear fuel splits from an incoming neutron, and in the process releases more-than-one neutron which then can trigger more fission events in nearby atoms. Of course you don't want all the fuel chain reacting in a geometrically expanding rate. That's a runaway reaction.

If intended, it can be a bomb. In a power reactor, a runaway reaction heats the solid fuel to such a degree that it melts anything around it, and gravity pulls it downward and it melts its way through ... anything. Eventually you hope the solid fuel expends enough of the fuel that it stops doing this, but by then the reactor is ruined and the national news cycle has hit.

So how does a solid fuel reactor stop runaway chain reactors? Moderator rods/systems and cooling. Perhaps you've seen some cartoon anime of an overloading reactor where the operators desperately inject rods into something. That is a moderator rod, trying to absorb and reduce the number of neutrons flying around and slow down the reaction. And there is good old cooling too.

But, like Fukushima showed, control systems are vulnerable to failure. Think you've designed enough failsafes? Nature will hit you with a bigger tsunami or a bigger hurricane or a bigger earthquake. Or.... humans over time will get lazy.

Solid fuel produces waste. As solid fuel is used, and the atoms either split in fission reactions, or absorb neutrons transmuting to other elements (some with bad half-lifes, more aggressive gamma emissions, etc). YOU CAN'T REMOVE THIS WASTE while the fuel is being used. So once enough of the solid fuel rod is used, it won't sustain a fission reaction anymore, it is then full of a ton of waste and crap.

So you have to transport it either to Yucca for long term storage, or maybe you truck it to someplace that will "reprocess it".

So solid fuel, NO MATTER WHAT, will involve active control systems and waste transport.

This is what the public is afraid of, and what nuclear meltdowns have shown can happen.

Thus every design needs to be carefully reviewed, approved, reapproved, and since there are so many actively managed safety systems with the threat of horrid meltdown, procedures and inspections and the like.

Well, what if there was a nuclear reactor design that:

1) CANNOT MELT DOWN (no disasterous runaway scenarios)

2) uses all its fuel (no waste)

So no transport of evil radioactive waste or dirty bomb material through your neighborhoods. No explosions (Chernobyl) or permanently hot cordoned off slag heaps of steel and concrete (Fukushima). No Yucca mountain.

Here's more advantages:

- scalable to small sizes, so no massive behemoth concrete towers and the like.

- doesn't even use uranium (and a rare isotope of uranium at that), it can breed fuel from thorium which is much more stable and non-radioactive.

- proliferation resistance aka can't make bombs from it (allegedly)

- possibly can "burn" nuclear waste from solid fuel reactors

It is a Molten Salt Reactor, or Liquid Fluorine Thorium Reactor. The fuel is liquid. There is a lot of stuff on the internet about it from enthusiasts. You can actively reprocess the fuel as the reactor is generating power (because you pipe it out). Because it is a breeder reactor, you can breed transuranic waste with neutrons into usable isotopes. You can extract "fission products" (the non-fissile elements resulting from atom splits or radioactive decay) from the liquid using chemical processing. In the process of "online processing" the liquid fuel, you constantly pipe the usable part back to the reactor. So the reactor uses ALL the fuel.

The liquid nature of the fuel expands and contracts with the heat of the liquid, reducing criticality. IF you get overheated, a "plug" melts that drains the liquid fuel into a cooling pan that separates the liquid into a state where it is non-critical (won't sustain a chain reaction). IF the containment reactor "sprang a leak",well, the liquid would spill into a shape that was non-critical. It can't melt down. Even if every safety system fails, it can't melt down.

The problem is a commercial design doesn't exist. At some point in the early 1970s the development was axed by the Nixon Administration (and political backstabbing if you listen to the proponents) in favor of solid fuel rod reactors.

The ENTIRE nuclear power industry is built around solid fuel. Its all they can conceive of. But as I described, solid fuel is fatally flawed from a political perspective. Large scale solid fuel reactors will never be on time and under budget in the USA.

China is actively working on LFTR/MSR/liquid fuel reactors. Coincidentally (not) there are several research reactors appearing in some US research universities and national labs. And LFTR/MSR has some real challenges in materials engineering (molten salts are hard), and of course the liquid fuel reprocessing is complicated, not as hand-wavy as I may have made it seem.

But IMO the fundamental advantages of the approach are the only known viable path to a nuclear reactor that is economical and politically palatable in the USA. A fundamentally safe practically waste-free reactor.

The you wouldn't need so many white gloves, inspectors, etc. Scalability means you can build them in a factory, and if one of 20-100 reactors fail (can't melt down, remember), well, you drain the (liquid, remember) fuel and cart it away and replace it with a new one and pipe the fuel back into the new one.

Now to emphasize THERE ISN'T A VIABLE COMMERCIAL DESIGN YET. Maybe it's impossible. And the vast majority of the nuclear industry (solid rod reprocessing, waste transport, reactor vendors) doesn't even want a liquid reactor, because they can't profit off of it. They have no interest in its development because it is a massive risk, they are desperately trying to eke a profit out of current nuclear plants, which are fundamentally noncompetitive on LCOE economics. Really, the government has to do it.