My understanding is that these reactors are designed to have a lot of passive safety features (e.g. if all operators walk away the reactor will cool itself and go sub-critical), so quite the opposite of what you are claiming.
Those safety systems don’t exist in a shipping container sized nuclear reactor. One method that I think you’re talking about is when the temperature of the molten salts goes beyond a certain safety threshold then a heat sensitive plug is disintegrated and the Milton salts are drained into a safe underground reservoir for them to cool. (This is my recollection from that why thorium is the future video that went viral years ago) Can’t do that in a shipping container.
I was thinking of Copenhagen Atomics' Waste Burner design where they describe their passive walk-away safety features as "Prime minister safety" [1].
> The CA Waste Burner has a set of systems governed by the laws of physics that cannot be overruled by humans, and which will cause the reactor to shut down safely if something goes wrong...This means that operators are not required to watch for alarms and act in accordance. The CA Waste Burner must be able to automatically shut down before any human can react to an alarm and choose what to do. If human action were ever required for operation, other than during startup procedures, then we would consider it a design failure...
> The CA Waste Burner has a set of systems governed by the laws of physics that cannot be overruled by humans, and which will cause the reactor to shut down safely if something goes wrong.
This is really good, but humans have an amazing knack for messing stuff up and I really hope corners aren’t cut building and maintaining it.
What comes to mind is the situation in Japan where workers inadvertently had some material go critical, and while this was being investigated it was found that they were carrying waste uranium and nitric acid around by hand in buckets.
