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I always wondered why the navy didn't push for thorium reactors. It was my understanding that they would not need the water pumps that current sub reactors nee

I always wondered why the navy didn't push for thorium reactors. It was my understanding that they would not need the water pumps that current sub reactors need thus being quieter.

hwillis 6y ago
1. Thorium reactors are almost identical to uranium reactors and it is a recent but common misconception that they are so fundamentally different. The whole point of thorium is that it turns into uranium. The only real difference is that there are many fewer excess neutrons around, because they're used to convert thorium to uranium. To convert a uranium reactor to thorium you basically only need to change the fuel. The reasons to do that are scalability (thorium is more abundant than U-235) and the fact that fewer neutrons means less plutonium. Molten salt reactors such as LFTR and molten metal reactors are not exclusive to thorium. You can even have a liquid flourine uranium salt reactor. Any submarine would be highly unlikely to use thorium due to it's much lower power density compared to highly enriched uranium. Thorium basically has to enrich itself over time, so you need a lot of it to get to a given power level. 2. The US is the only country that exclusively (except for one sub) uses pressurized water reactors. Russia uses liquid salt or metal mostly. Liquid salt reactors -like the ones most commonly proposed with thorium- still need conventional centrifugal pumps to operate. It's only certain liquid metal reactors that can use electromagnetic pumps, and I'm pretty sure they still need pumps for the secondary water loop. 3. The whole "nuclear water pumps are loud" thing is pretty much a myth anyway as far as I understand. Pound-for-pound, nuclear subs are much quieter than diesel, but the quietest submarines are obviously very small. Nuclear submarines are obviously very large, and so are loud simply by nature. That led to speculation that being nuclear meant submarines were louder, which led to people talking about pumps and turbines and whatnot being loud.

I always wondered why the navy didn't push for thorium reactors. It was my understanding that they would not need the water pumps that current sub reactors need thus being quieter.

hwillis 6y ago

1. Thorium reactors are almost identical to uranium reactors and it is a recent but common misconception that they are so fundamentally different. The whole point of thorium is that it turns into uranium. The only real difference is that there are many fewer excess neutrons around, because they're used to convert thorium to uranium. To convert a uranium reactor to thorium you basically only need to change the fuel. The reasons to do that are scalability (thorium is more abundant than U-235) and the fact that fewer neutrons means less plutonium. Molten salt reactors such as LFTR and molten metal reactors are not exclusive to thorium. You can even have a liquid flourine uranium salt reactor. Any submarine would be highly unlikely to use thorium due to it's much lower power density compared to highly enriched uranium. Thorium basically has to enrich itself over time, so you need a lot of it to get to a given power level. 2. The US is the only country that exclusively (except for one sub) uses pressurized water reactors. Russia uses liquid salt or metal mostly. Liquid salt reactors -like the ones most commonly proposed with thorium- still need conventional centrifugal pumps to operate. It's only certain liquid metal reactors that can use electromagnetic pumps, and I'm pretty sure they still need pumps for the secondary water loop. 3. The whole "nuclear water pumps are loud" thing is pretty much a myth anyway as far as I understand. Pound-for-pound, nuclear subs are much quieter than diesel, but the quietest submarines are obviously very small. Nuclear submarines are obviously very large, and so are loud simply by nature. That led to speculation that being nuclear meant submarines were louder, which led to people talking about pumps and turbines and whatnot being loud.