Actually there is one, the molten salt reactor. If the containment vessel is compromised the molten salt runs out and hardens and immediately stops fissioning. Oak Ridge experimented with Thorium which is many times more plentiful that Uranium. It wasn’t commercialized because Thorium reactors can’t produce Plutonium.
Fortunately, there are many companies that are currently working to commercialize the MSR. You want a green solution? This is it. Even existing stocks of nuclear waste can be burned in one of these beauties.
I hope it’s time will soon come.
A very interesting video. It's too bad that the US didn't have the foresight to develop this technology further.