Earlier quoted context omitted.
You can say that about anything humans have ever built.
Exactly, so how is everyone so sure that "modern nuclear reactors" will encounter no problems?
Something bad (earthquake, tsunami, etc) could still happen that causes a plant shutdown. But there's no pressure vessel (other than regular steam on the generating side) to worry about breaching. And unlike current generation reactors, where even a full scram of control rods still requires some hours of active cooling to prevent core meltdown, if the liquid-type loses power, the core drains, and that's the end of it in terms of potential radiological release. That doesn't mean it isn't a complex, difficult system to design and operate. But it's a much, much safer design by its very nature.