Jump to content

If We Ever Get Sustained Fusion Reactions...Then What?


Spacescifi

Recommended Posts

5 hours ago, Entropian said:

Uhhh, what?

 

don't expect direct energy conversion until we start using second and third gen fusion power reactors. i think you also need to run aneutronic fuels for direct conversion to work, anything resulting in charged particles. initial reactors are all going to be d-d or d-t, and that means a thermodynamic cycle will be required to extract the energy. it might take a further 50 years to get there.  got to walk before you can run. 

Link to comment
Share on other sites

16 hours ago, Nuke said:

fission and fusion reactors start looking more or less the same when you get into the thermodynamic loop. both are just over-glorified steam engines.  

you could also be electrolyzing with hydroelectric. at off peak hours you could be electrolyzing water rather than shutting off turbines, reservoir levels permitting. the hydro plants we have all around southeast alaska have very little to do at night, and its mostly rain forest round these parts (we make seattle look like a desert). 

Yeah fusion power reactors will definitely be similar, but it seems like they'll operate at lower temperatures in the working fluid, since the reactors need to be larger for a given power output iirc. So it seems like fission would be better suited.

The problem with hydroelectric is that there just isn't all that much capacity in it from my understanding. And you're going to need a lot of capacity to electrolyze hydrogen at the needed scales.

Link to comment
Share on other sites

On 11/14/2020 at 7:56 AM, Bill Phil said:

Electrolyzing hot water takes less electrical energy than electrolyzing room temperature water.

Like, steam vs liquid water or what ? I could see it being easier for steam, but I can't see it being easier if it's still in liquid form.

Link to comment
Share on other sites

17 hours ago, Nuke said:

don't expect direct energy conversion until we start using second and third gen fusion power reactors.

Perhaps not true direct conversion, but surely even D-T will produce plasma hot enough to use an MHD? If we managed to use them with coal or gas powerplants...

Link to comment
Share on other sites

7 hours ago, DDE said:

Perhaps not true direct conversion, but surely even D-T will produce plasma hot enough to use an MHD? If we managed to use them with coal or gas powerplants...

a lot of energy output is in the form of neutrons.  these actually have to hit one of the reactor blankets, which are likely going to have a coolant loop behind it providing the hot side of a thermodynamic cycle. i assume the alpha particles will end up in the diverter and might be subject to direct conversion . but the neutrons coming off the reaction are like 4x more energetic. you need both for an efficient power plant. 

aneutronic fuels, and i think the most practical is the p-b11 reaction because of its abundance on earth. we need about another order of magnitude more performance out of our current fusion reactors to get to scientific breakeven, perhaps 2 for engineering breakeven. aneutronic fuels will require a couple orders of magnitude on top of that to be viable. 

Link to comment
Share on other sites

15 hours ago, YNM said:

Like, steam vs liquid water or what ? I could see it being easier for steam, but I can't see it being easier if it's still in liquid form.

Probably steam, I'm not too aware of how pressure or state affects electrolysis.

Edited by Bill Phil
Link to comment
Share on other sites

On 11/16/2020 at 9:39 AM, Bill Phil said:

I'm not too aware of how pressure or state affects electrolysis.

In a gasseous state there's a lot more surface of the molecule for reaction to happen, or something along those lines I suppose.

Link to comment
Share on other sites

On 11/12/2020 at 3:55 AM, Nuke said:

no but hydrolox  is a renewable when you have a power plant that runs practically for free. 

Fuel to the reactors is limited. If we put our hands on resource it is depleted quite fast. Already there are more rectors under construction that we can supply with fuel. It is for free but it is not unlimited. It is why fussion plants are developed - they using another resource but also limited. over a hundred years ago whales were hunted for fuel and tehere were plenty of them, but this mine also get depleted. We mine fast, we gonna faster.

Link to comment
Share on other sites

6 hours ago, kerbiloid said:

Deuterium is practically unlimited (1/6000 of the terrestrial hydrogen, iirc) and is available almost on any celestial body having some form of hydrogen.

Tritium is the problem in this case. We need to develop DT reactors and then figure out DD.

Link to comment
Share on other sites

13 hours ago, kerbiloid said:

Tritium is oceanic lithium with radiation sickness.

Helium-3 as well.

Yeah, sure, it can be bred. But that then requires separating the isotopes.

A quick cost comparison should sum it up pretty well:

Deuterium: ~13400 USD per kg

Tritium: ~30000 USK per g, or around 30 million USD per kg

Tritium is more than 2000x more expensive than deuterium. Once we get DT to work, we need to get DD to work. As it stands, the cost of the tritium is too high to really be economical, though maybe cost be lowered with the right industry and technology. However, it'd be a lot nicer if we could get DD. Then we don't have to worry about producing tritium.

Link to comment
Share on other sites

22 minutes ago, Bill Phil said:

But that then requires separating the isotopes.

With atomic mass 6 and 7 rather than 235 and 238, even nothing to compare

22 minutes ago, Bill Phil said:

Deuterium: ~13400 USD per kg

While it's a luxury. When it becomes a fuel, prices will be near the floor. Isotope mass 1:2.

22 minutes ago, Bill Phil said:

Tritium: ~30000 USK per g, or around 30 million USD per kg

Required only in the very first reactors. D-D catalyzed with He-3 (from Li) would need it only for ignition, in trace amounts.

D-D reactor gives a lot of neutrons, so the irradiated Li will get many times cheaper. So T and He-3 as well.

Edited by kerbiloid
Link to comment
Share on other sites

1 minute ago, kerbiloid said:

With atomic mass 6 and 7 rather than 235 and 238, even nothing to compare

While it's a luxury. When it becomes a fuel, prices will be near the floor.

Required only in the very first reactors. D-D catalyzed with He-3 (from Li) would need it only for ignition, in trace amounts.

D-D reactor gives a lot of neutrons, so the irradiated Li will get many times cheaper.

Eh, separation is still tough because the tritium will likely be in a chemical compound or some complex mixture.

Deuterium isn't a luxury, it's used in heavy water as a moderator. It may get cheaper, but my point was that it was still vastly cheaper than tritium.

You're better off sourcing tritium from fission reactors.

I think that we'd be better off not having to use something to ignite D-D reactions. If we do though, then a small chunk of D-T fuel in a pellet would probably suffice. And you can get tritium from fission reactors as is. By the time fusion reactors are widespread enough to produce appreciable amounts of tritium, they would probably (or at least hopefully) not need it.

 

Link to comment
Share on other sites

20 minutes ago, Bill Phil said:

Eh, separation is still tough because the tritium will likely be in a chemical compound or some complex mixture.

Separation of what? Separate lithium isotopes, irradiate Li-6 (probably in form of, say, oxide), exttract and collect tritium (or wait until it decays in He-3 which is inert and escapes itself).
No other hydrogen isotopes are involved.

20 minutes ago, Bill Phil said:

Deuterium isn't a luxury, it's used in heavy water as a moderator.

It's used in much smaller amounts than should be in case of deuterium energetics, when BP, Shell, and others will start refining it as future oil.
So, it will be cheaper by order(s) of magnitude.

20 minutes ago, Bill Phil said:

You're better off sourcing tritium from fission reactors.

Fission reactors need limited fission fuel.
Though, of course D-D reactors can use depleted uranium and thorium pellets in additional induced reaction zone. 

20 minutes ago, Bill Phil said:

I think that we'd be better off not having to use something to ignite D-D reactions. If we do though, then a small chunk of D-T fuel in a pellet would probably suffice.

D-D needs to be much hotter to ignite. Some catalyzer in minor amounts may be or may be not useful to reduce the required temperature by local early ignition. T and He-3 are just the most obvious ones.

Edited by kerbiloid
Link to comment
Share on other sites

13 hours ago, kerbiloid said:

Separation of what? Separate lithium isotopes, irradiate Li-6 (probably in form of, say, oxide), exttract and collect tritium (or wait until it decays in He-3 which is inert and escapes itself).
No other hydrogen isotopes are involved.

Chemical and physical separation of the tritium from everything else. There's also He4 in there, too. Separating it is entirely possible, but I don't think it's desirable for fusion power reactors. Using a much more common naturally occurring fuel is preferred.

13 hours ago, kerbiloid said:

It's used in much smaller amounts than should be in case of deuterium energetics, when BP, Shell, and others will start refining it as future oil.
So, it will be cheaper by order(s) of magnitude.

Yes, it will be cheaper. But the cost of deuterium isn't the problem here.

13 hours ago, kerbiloid said:

Fission reactors need limited fission fuel.
Though, of course D-D reactors can use depleted uranium and thorium pellets in additional induced reaction zone. 

Extracting and processing large amounts of uranium is a mature industry. Seawater extraction is also approaching reasonable costs, and may get there relatively soon. Tritium production won't need to be too large anyways for our energy use, and tritium extraction from fission reactors is already done.

13 hours ago, kerbiloid said:

D-D needs to be much hotter to ignite. Some catalyzer in minor amounts may be or may be not useful to reduce the required temperature by local early ignition. T and He-3 are just the most obvious ones.

Yes, I'm aware that D-D needs to be hotter than D-T. The issue is, D-He3 is harder than D-D, and requires He3. A pure D-D setup is preferable, with a D-T ignited D-D setup being acceptable. D-He3 ignited D-D is not desirable since you're trying to ignite a hard D-D reaction with a harder D-He3 reaction.

Link to comment
Share on other sites

On 11/16/2020 at 3:39 AM, Bill Phil said:

Probably steam, I'm not too aware of how pressure or state affects electrolysis.

If you use hot and dry steam you have an risk of splitting water into oxygen and hydrogen. 
Well then it mixes and explodes. This caused exlosions at Fukushima reactor as they had no way to cool the water it started splitting. 
Its also known in steam engines on warships during battles. 
So doing elextrolyze on steam might be an option, its interesting for an nuclear plant as you want to run it at base load all the time as fuel cost is an tiny part of the operational cost. 

Link to comment
Share on other sites

8 hours ago, magnemoe said:

If you use hot and dry steam you have an risk of splitting water into oxygen and hydrogen. 
Well then it mixes and explodes. This caused exlosions at Fukushima reactor as they had no way to cool the water it started splitting. 
Its also known in steam engines on warships during battles. 
So doing elextrolyze on steam might be an option, its interesting for an nuclear plant as you want to run it at base load all the time as fuel cost is an tiny part of the operational cost. 

Yeah it's something that you have to be careful with.

Link to comment
Share on other sites

9 hours ago, Bill Phil said:

Chemical and physical separation of the tritium from everything else. There's also He4 in there, too. Separating it is entirely possible, but I don't think it's desirable for fusion power reactors. Using a much more common naturally occurring fuel is preferred.

I would remind about the uranium separation process. It's much more complicated, but they do it.
Also the natural oil and gas refining.

9 hours ago, Bill Phil said:

Extracting and processing large amounts of uranium is a mature industry.

This doesn't make the uranium itself endless. Deuterium is by orders of magnitude more available.

9 hours ago, Bill Phil said:

Seawater extraction is also approaching reasonable costs, and may get there relatively soon.

Yes, and I mean it as a natural part of the deuterium powerplant.
It should be placed on the oceanic coast, and refine seawater, extracting D, Li, U, and using in-situ.

9 hours ago, Bill Phil said:

Tritium production won't need to be too large anyways for our energy use, and tritium extraction from fission reactors is already done.

Certainly, we want all tritium we get. From U, Li, and whatever else.
Actually, it's a a powerplant fueled with seawater.
But possible also on any other celestial body with available hydrogen.

9 hours ago, Bill Phil said:

Yes, I'm aware that D-D needs to be hotter than D-T. The issue is, D-He3 is harder than D-D, and requires He3. A pure D-D setup is preferable, with a D-T ignited D-D setup being acceptable. D-He3 ignited D-D is not desirable since you're trying to ignite a hard D-D reaction with a harder D-He3 reaction.

No problem, the Li-produced He-3 is just a depleted T. So, if we don't need He-3, we just skip the exposition phase.

(He-3 is just from the lunar helium discussions, I'm all for T.
The only advantage of He-3 is aneutronic fusion, but this is irrelevant for D-D reactor, and helium is hard to store on ships, so I was never a fan of it, and always mention only to show that mining it on the Moon makes no ssense when we can get it from ocean..)

Edited by kerbiloid
Link to comment
Share on other sites

There's a company in Canada called General Fusion which is developing a very practical-sounding Magnetic Targeted Fusion design.

1024px-General_Fusion_Reactor.svg.png

The fusion reaction is driven by literally pounding a pressure vessel with synchronized high-powered pistons. Heat is extracted by surrounding the reaction in a bubble of liquid lead-lithium  (orange, in the diagram). The liquid is suspended against the walls by using a round cage-like agitator (not shown) which stirs the liquid and keeps it rotating at speed. The liquid metal is also vented  out of the pressure vessel and used as the heat-transfer medium for extracting energy. Because it's lead, it's great at absorbing neutron radiation. Because it's pumped liquid, it's easy to replace and refresh. They market themselves to investments and research as "the fastest and most practical method" for commercial fusion power. They're currently in the process of designing a demonstration plant.

maxresdefault.jpg

Though not unlike most of its competitors, it's a pretty large reactor. In the picture here, you can see how big these pistons are.

General-Fussion.jpg

 

Edited by starcaptain
Link to comment
Share on other sites

8 hours ago, starcaptain said:

There's a company in Canada called General Fusion which is developing a very practical-sounding Magnetic Targeted Fusion design.

1024px-General_Fusion_Reactor.svg.png

The fusion reaction is driven by literally pounding a pressure vessel with synchronized high-powered pistons. Heat is extracted by surrounding the reaction in a bubble of liquid lead-lithium  (orange, in the diagram). The liquid is suspended against the walls by using a round cage-like agitator (not shown) which stirs the liquid and keeps it rotating at speed. The liquid metal is also vented  out of the pressure vessel and used as the heat-transfer medium for extracting energy. Because it's lead, it's great at absorbing neutron radiation. Because it's pumped liquid, it's easy to replace and refresh. They market themselves to investments and research as "the fastest and most practical method" for commercial fusion power. They're currently in the process of designing a demonstration plant.

maxresdefault.jpg

Though not unlike most of its competitors, it's a pretty large reactor. In the picture here, you can see how big these pistons are.

General-Fussion.jpg

 

the gf reactor is tiny compared to iter. 

Link to comment
Share on other sites

10 hours ago, Entropian said:

>Practical

As every company calls their fusion devices.

gottem

...wait

2 hours ago, Nuke said:

the gf reactor is tiny compared to iter. 

For a second I thought you were talking about girlfriends.

I would think that a smaller reactor uses less material to build and thus costs less. But then again I'm not even an armchair layperson when it comes to fusion power. I'm like a know-nothing schlub when it comes to fusion power.

Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...