Viewing a single comment thread. View all comments

ivonshnitzel t1_j18rrka wrote

Short answer is that there are ways to make neutrons produce more than one triton. Neutrons can react with lithium-7 to produce tritium + a neutron (which can then go on to react with another lithium-6 or lithium-7 nucleus to produce more tritium). Neutron multipliers such as beryllium that react with neutrons to produce two neutrons can also be included in the tritium bleeding blanket.

450

Splatterman27 t1_j191mii wrote

So the next challenge is capturing enough energy to power these processes, with excess going into the grid.

51

zekromNLR t1_j1b9g5z wrote

Those processes are how a D-T fusion plant would capture energy. About 80% of the energy output of D-T fusion is in the neutron, and the other 20% are probably required to keep the plasma hot anyways. As the neutrons slow down and go through nuclear reactions in the breeding blanket, they will give up their kinetic energy as heat, which can then be used to boil water and drive a steam turbine.

65

lo53n t1_j1bb1ke wrote

Its so strange, after all those years we still convert kinetic energy to electricity via steam turbine. Is there even any feasible option to phase out steam energy or use more direct conversion?

52

[deleted] t1_j1bdth3 wrote

[removed]

37

FinndBors t1_j1bq2hs wrote

You are looking for aneutronic fusion: https://en.wikipedia.org/wiki/Aneutronic_fusion

He3 is required but rare, or Boron fusion but needs a ton more input energy than D-T fusion. The sibling comments regarding Helion Energy is an attempt to do this using He3 and a way to synthesize it since it is very rare. The way they synthesize it is D-D fusion which does produce neutrons.

Regarding He3, people talk about mining this on the moon since it is less rare there, but IMO, its a stupid idea since it isn't like mining an ore where there is concentrations of it, it's weakly spread out all over the surface.

4

[deleted] t1_j1991c0 wrote

[removed]

26

graebot t1_j18ta5r wrote

Would there ever be a danger of a chain reaction with that setup?

19

[deleted] t1_j18uziv wrote

[removed]

47

RobusEtCeleritas t1_j1agk2b wrote

No, these are not like the fission chain reactions used in fission reactors. There's no way for that kind of thing to happen in this situation.

45

[deleted] t1_j1chn3p wrote

[removed]

0

RobusEtCeleritas t1_j1ctdta wrote

I don't know what you think those statements have to do with my comment. The question was whether the tritium-breeding reactions can cause a chain reaction, and the answer to that is no.

1

[deleted] t1_j1bdh3t wrote

[removed]

−2

RobusEtCeleritas t1_j1bejog wrote

RBMK fission reactors are completely different things than what we're talking about here. There's plenty of information available on what caused the Chernobyl accident, none of which is relevant to this conversation.

6

SnarfbObo t1_j1bdqqi wrote

Something goes wrong it just goes dark, the fun is in starting it up again, as i understand(not much)

5

AeternusDoleo t1_j1d635j wrote

There would be a danger of a localized kaboom, once the plasma loses containment it disperses - explosively. But I'm going to assume the amount of fuel in the reactor is going to be minimal, after all you're after a controlled fusion reaction. Once the fuel is spent or the pressure/temperature is too low to sustain fusion, the reaction ends.

2

cdstephens t1_j1bq2qw wrote

No, fusion devices cannot lead to an uncontrolled chain reaction. The reason is because the plasma needs to be confined in order to maintain the appropriate density and temperature; the Sun uses gravity to confine the plasma. In contrast, if the magnetic fields were turned off in a magnetic fusion device, the fusion plasma would just expand outwards into the wall and then cool down.

1

ClapAlongChorus t1_j19w9jp wrote

Good thing Lithium is an abundant and easily mined element and there aren't any other applications in the energy sector already pressing supply to the limit.

7

Danne660 t1_j19y40r wrote

The amount of lithium needed for this is ludicrously small compared to the other applications you are alluding to.

99

ClapAlongChorus t1_j1a7i0j wrote

oh really?? that's cool, I always assumed the Fusion revolution required a decent amount of fuel and that was never a big deal until massive batteries came along and started using lithium as fast as we could pull it out of the ground in Western Australia. Sometimes it's neat not knowing much because there are so many chances to learn

7

DontWorryImADr t1_j1agg8b wrote

So for a comparison, a single EV battery requires something on the order of 63 kg of lithium. Assuming this is even remotely true, we then have references from Youtubers like Real Engineering who estimate a commercial fusion plant would need about 600g of tritium per day.

Switching from mass to equivalent atom counts and then back to relate, 600g of tritium is just shy of 200 moles (3.016 g/mol). Multiplying this by the molar mass of lithium (6.941 g/mol) gets us ~1,382g. I couldn’t easily find an efficiency rate, so let’s assume we’re terrible at conversion and only manage 1% conversion rate: a plant would require about 138kg per day.

So while the lithium usage by a commercial power plant would be noticeable if they became super common.. it would amount to about two EV batteries per day, per plant. Considering we may need over 30 million EV batteries per year by 2030, this would be a very small impact.

Edit: month —> day Edit2: I was lame, got the molecular mass of tritium (T2) rather than atomic mass, and ran with the math. All fixed now.

58

starmartyr t1_j1awu3m wrote

Would it be possible to extract the lithium from dead batteries?

7

DontWorryImADr t1_j1b07jo wrote

It better be, considering the volume of waste if all those batteries need replacement every 10 years. That would be the order of 1.89 billion kg of lithium every battery replacement cycle based upon 2030 numbers. Considering some of the issues with lithium, that would be all sorts of bad.

I don’t know that commercial scale recycling of said batteries is truly ready, but hence why it’s a big area of examination and study when it comes to converting transportation away from fossil fuels.

16

mrwolfisolveproblems t1_j1bph0g wrote

Battery end of life with EVs is the 1000 pound gorilla in the room that no one wants to acknowledge. All these states passing laws to ban sales of ICE vehicles have put zero thought into it that’s for sure. Not to mention the huge cost to consumers of said replacements. So insane to me that these problems are not close to being solved with EVs being jammed down everyone’s throat. I guess necessity is the mother of all invention, so hopefully mass EV adoption will drive solutions to these problems. End of sidebar.

2

FRCP_12b6 t1_j1c8jic wrote

When an EV battery gets old it can still be reused as grid storage, even if the remaining capacity is low.

2

mrwolfisolveproblems t1_j1ehkcm wrote

If an EV battery is so degraded it can provide a few hours of runtime in a car what meaningful use will it have to the grid? Has anyone actually tested this at reasonable scale beyond a simple demonstration? Who is going to pay for the infrastructure to connect all these old batteries to the grid? That grid storage argument is just thrown out there for PR. It would take decades to get off the ground and we’re going to have millions of dead battery packs in 10 years.

2

FRCP_12b6 t1_j1emd2d wrote

The batteries need to be good power to weight density to be useful in a car. More weight means less range. A battery with 60% capacity is still useful on land, where weight doesn’t matter.

2

mrwolfisolveproblems t1_j1gdayr wrote

So a 100kwh pack becomes 60kwh. A thousands of them together gives you 60MW for 1 hour. Peak load demand can swing 20-40,000 MW for 10+ hours at a time. That’s just peak demand, forget about base load, and that’s just in a regional area (say Texas for example) An extra 20,000 MW for 10 hours is 200,000,000 kWh. You would need 3.33 million old battery packs all tired together and synced to the grid. Not to mention every day they will lose capacity and eventually be useless even for grid storage.

TLDR: need to find a way to recycle them into new batteries like we do for lead acid batteries.

2

Michaelmrose t1_j27glhf wrote

Recycling is complicated parties are working on it included the United States Advanced Battery Consortium—made up of General Motors, Ford, Stellantis, and the Department of Energy.

https://arstechnica.com/science/2022/04/lithium-costs-a-lot-of-money-so-why-arent-we-recycling-lithium-batteries/

2

mrwolfisolveproblems t1_j28suc0 wrote

Thank you for posting that. Doesn’t seem like it’s too promising right now, but it’s being worked on and moving in the right direction it seems. Hopefully they make some leaps forward in the next 5-7 years.

1

mrwolfisolveproblems t1_j28sxzf wrote

Thank you for posting that. Doesn’t seem like it’s too promising right now, but it’s being worked on and moving in the right direction it seems. Hopefully they make some leaps forward in the next 5-7 years.

1

ukezi t1_j1b0zth wrote

Lithium 6 absorbs a neuron and gets split into a helium and a tritium, so you need two times as much as you need tritium.

5

DontWorryImADr t1_j1dj3ra wrote

Why would you need twice as much if one lithium atom produces one tritium atom?

2

ukezi t1_j1djugo wrote

Lithium-6 weights about double of tritium (Hydrogen-3). So for 1 kg tritium you need 2 kg lithium.

2

DontWorryImADr t1_j1do3ej wrote

Yeah, that was silly. I looked up atomic masses, got the molecular mass for tritium and didn’t think twice about it in the math. Thanks for the catch!

1

adventuringraw t1_j1abuxl wrote

There's been recent advances with MOF filters that energetically favors Lithium going through, kind of like ion channels in cells. It drastically decreases time and water cost in filtering out Lithium, and I guess it's being tested at scale now. It certainly won't solve Lithium supply constraints, but stuff like that's cool to look at... advances in one area of tech research potentially facilitating progress in others. It'll be interesting to see how things change over the next decade.

10

PlayMp1 t1_j1ad2de wrote

It really helps that lithium is a relatively common element though, undoubtedly.

3

zekromNLR t1_j1ba8rm wrote

Well, you would need a quite large inventory of lithium in the reactor to capture a large fraction of the neutrons, but it would only be consumed at a slow rate. Even assuming only 20% of the fusion power comes out as net electricity output (the rest being either lost as waste heat or needed to keep the fusion going), a 1 GW D-T fusion power plant would consume only about 275 kg of tritium per year, which would correspond to a lithium consumption of about 600 kg per year, depending on the specific mix of lithium isotopes.

5

Interpole10 t1_j1bad0d wrote

I read an article a year ago or so about extracting lithium from seawater through a fairly efficient process.

It’s possible that this is the method that could be used for this in the future.

1

aragorn18 t1_j1c3qi2 wrote

Isn't there a problem with there not being enough beryllium to make more than a couple of large scale reactors?

2

Lurker_Since_Forever t1_j1d5zib wrote

This right here is why I don't know of any start ups making large tokamaks, and are instead doing something like liquid cooling with liquid zinc or direct capture with magnets.

1

StateChemist t1_j1aoiaf wrote

In short, a raise in demand for tritium will drive more production of tritium?

1