Author Topic: Fluid fuel NTR?  (Read 1407 times)

Offline constantius

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Fluid fuel NTR?
« on: 02/17/2012 10:52 pm »
I've heard of fluid fuel reactors (on earth) designed to breed U-233 from Thorium. I'd think that for long term missions (20yrs instead of 2yrs) some way to dispose of fission products would be helpful. That's very hard to do with a solid core reactor without reprocessing, but trivial with a fluid fuel core. Has there been any research on whether we could use a fluid fuel NTR as an alternative to a solid core NTR?

Offline beb

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Re: Fluid fuel NTR?
« Reply #1 on: 02/17/2012 11:07 pm »

Offline constantius

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Re: Fluid fuel NTR?
« Reply #2 on: 02/17/2012 11:38 pm »
I've heard of fluid fuel reactors (on earth) designed to breed U-233 from Thorium. I'd think that for long term missions (20yrs instead of 2yrs) some way to dispose of fission products would be helpful. That's very hard to do with a solid core reactor without reprocessing, but trivial with a fluid fuel core. Has there been any research on whether we could use a fluid fuel NTR as an alternative to a solid core NTR?

That is a gas core reactor, which has a myriad of problems. I was thinking about more of a conventional NTR with some sort of fluid carrying heat instead of a solid.

Offline randomly

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Re: Fluid fuel NTR?
« Reply #3 on: 02/18/2012 12:57 am »
You can get high burnup on a solid core reactor by using Highly Enriched Uranium and burnable poisons.
Certainly it's easier to process liquid fuel cores to remove fission products but it's not trivial at all and it adds considerable complexity and weight if you try to do more than remove the Xenon.

I don't think it would be a good solution to include fission product removal in such a reactor. Better to just use highly enriched fuel, burnable poisons, and/or some breeding to maintain reactivity over the reactor lifetime. Liquid fuel cores also have the option of injecting new fuel into the reactor to increase core reactivity.

Liquid fuel reactors do have some good potential for space reactors and I would love to see development on them, but for other reasons than reprocessing.

Offline bubbagret

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Re: Fluid fuel NTR?
« Reply #4 on: 02/18/2012 01:27 am »
Google Liquid fluoride thorium reactor...

Offline ArbitraryConstant

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Re: Fluid fuel NTR?
« Reply #5 on: 02/18/2012 06:38 am »
I've heard of fluid fuel reactors (on earth) designed to breed U-233 from Thorium. I'd think that for long term missions (20yrs instead of 2yrs) some way to dispose of fission products would be helpful.
It turns out fission product removal like that is only really necessary if you're trying to achieve a break even breeding ratio. If you just use HEU to start with you can afford to lose many more neutrons.

Breeding may be useful for civilian power because other considerations become more relevant at that scale, but for probes, manned craft, or small bases, HEU is the better choice.

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