[Retric]

The US has 2 sunk Nuclear submarines (129 and 99 lives lost). With at least USS Thresher being related to a loss of propulsion and thus at least indirectly the reactor. Considering how few where in service and none being sunk in wartime that’s not a great safety record. https://en.m.wikipedia.org/wiki/List_of_sunken_nuclear_subma...

The cause of USS Scorpion’s sinking is unknown so it may be related to the reactor or it may not.

[manigandham]

We're discussing safety record for nuclear power specifically, not lost ships for any reason. The USN has about half of all the reactors running by the USA. How is that a "few"?

If you read the page about USS Thresher then it clearly explains it had nothing to do with the reactor and was a "high-pressure water spraying from a broken pipe joint may have shorted out one of the many electrical panels, causing a shutdown ("scram") of the reactor, which in turn caused loss of propulsion" followed by other personnel and procedure issues that led to a sinking.

[Retric]

That quote directly says the loss of reactor power was part of the chain of events leading to a sinking.

Sure it did not blow up, but that does not mean the reactor was safe to use as a critical piece of equipment. Loss of power is a huge deal and the reactor being unable to recover in that situation is a major design flaw.

[manigandham]

That's like saying a torpedo hit the sub and the reactor stopped working so it's a reactor problem. You're being disingenuous. The reactor was not the part that malfunctioned.

Again, if you read that page then you'll find several other causes like faulty ballast tanks that didn't eject, isolating the steam system too quickly and eliminating potential energy from the turbines, and inexperienced personnel not restarting the reactor after shutdown. If just the ballast tanks had worked then the sub would be safe for rescue, if the steam was used then it could continue to drive to surface.

According to an official report [1]: "U.S. Nuclear Powered Warships have safely operated for more than 50 years without experiencing any reactor accident or any release of radioactivity that hurt human health or had an adverse effect on marine life. Naval reactors have an outstanding record of over 134 million miles safely steamed on nuclear power, and they have amassed over 5700 reactor-years of safe operation." and this is from several years ago.

1. https://www.mofa.go.jp/region/n-america/us/security/fact0604...

[Retric]

Steam turbines are part of a nuclear reactor. If it had used batteries and Diesel engines there would have been no steam system to fuck up.

I absolutely agree it was not the single cause of failure, it was even recoverable in theory. But, if the reactor had continued to supply power, like large result battery systems tend to, then it would have likely made it. That directly means using a reactor was less safe to put on the sub.

If an aircraft lost all engine power over the ocean because of a defective engine design and thus crashed. Well you can bet the navy would blame the engines, but with nuclear power they care about perception. The loss of a crew is acceptable risk, the loss of nuclear reactors from a public backlash is a loss of capability.

PS: They can and do mitigate this risk by having large battery systems for redundancy, it’s only a few hours of power. But, it can run a redundant electric engine to move the sub, and that’s an important lesson learned.

[manigandham]

If it was a diesel-electric then the broken water-pipe would've shorted out the batteries and electrics, and the flooded engine room would've stopped the engines, resulting in the exact same loss of power.

The fact is that the reactor didn't fail, it worked normally. The steam system didn't "fuck up" but was used incorrectly. The part that did fail was the ballast tank safety system. Diesel-electrics aren't a magical answer and have major disadvantages (like the need for air intake in a submarine).

It seems you're arguing that nuclear-powered designs aren't good, which is an entirely different topic than the safety record of the reactors themselves. Bad design of a system is not an argument that that core principles are inherently wrong, which is exactly the same thing any nuclear expert will tell you about Chernobyl.

[Retric]

It’s very possible that a broken pipe would have shorted out all batteries on an equivalent non nuclear sub. But, that would also have been a significant design flaw.

Anyway, I think this is more a case of disagreements about what constitutes a system than about what happened. I would say if the design of a critical system lets people mess up then that’s a failure of the design and the system. Chernobyl was very much a case of operators doing a long series of dumb things as people do. Similarly, the operators caused an issue with the steam system, but that just means the system and it’s design was also faulty. (IMO, the steam system should be considered part of the nuclear power plant as civilian nuclear power plants also use a steam loop for similar reasons.)

I would rate the US Navy highly on nuclear safety operations especially over the last 50 years.