[lazide]

Something like 20 tons (!) of fuel rods, almost the entire load, melted. [https://commons.m.wikimedia.org/wiki/File:Graphic_TMI-2_Core...]

It took years to find that out though.

The containment vessel held, and most of the radiation released was in the form of xenon and krypton gas vented from the reactor.

“ It was later found that about half the core had melted, and the cladding around 90% of the fuel rods had failed,[21][76] with 5 ft (1.5 m) of the core gone, and around 20 short tons (18 t) of uranium flowing to the bottom head of the pressure vessel, forming a mass of corium.[77] The reactor vessel—the second level of containment after the cladding—maintained integrity and contained the damaged fuel with nearly all of the radioactive isotopes in the core.”

Definitely not Chernobyl, but it was a significant amount of damage to the reactor. It was totaled.

[Animats]

There is a lot to be said for big, strong containment vessels. Fukishima's was too small and overpressure broke it open. Chernobyl didn't have one. Three Mile Island had a good one.

Many of the "small modular reactor" schemes say they don't need a big, strong, expensive containment vessel because, reasons. You can read those arguments for NuScale in NRC documents. The prototype was going to be built at the Idaho National Laboratory, formerly the National Reactor Testing Station, which is in outer nowhere, just in case.

[lazide]

If I remember correctly, part of the issue has been supply chain - the equipment necessary to forge the large steel parts necessary for these containment vessels are few and far between - and now all foreign.

[https://www.newequipment.com/plant-operations/article/219218...]

[jasonwatkinspdx]

Just to be fair, a big reason Nuscale went to the Idaho site is it'd streamline approval.