There are any number of speculative designs that are naturally fail-safe, but none of them in operation (outside of test facilities). I'm not a betting man, bu

There are any number of speculative designs that are naturally fail-safe, but none of them in operation (outside of test facilities). I'm not a betting man, but I would wager a significant amount of money that by the time IMSR becomes widespread and approved it will require a large number of active failure measures to be considered "safe". > If a nation seriously decided to invest in next generation nuclear, and were willing to put real money behind these designs, they could build them within a couple of years. Sure -- they could do that with existing designs as well. But these things have a great deal of natural complexity, and once again, I would practically guarantee that whatever designs they choose will have active fail-safes, even if the concept does not require it in theory.