How nuclear fusion (maybe) works (4) - reactor practicalities

Discussion of practical elements of any future nuclear fusion power plant.
This video is released under a Creative Commons licence.
Contents
00:00 - Introduction
00:26 - Maintaining a vacuum
05:23 - Introduction
06:55 - Getting energy out
10:06 - Neutrons
13:51 - Neutron activation
19:00 - Tritium breeding
21:31 - Fission-fusion hybrid
22:12 - Neutron damage
27:43 - Long-term prospects
29:01 - Summary
References
[1] Welcome to Planet ITER: a technical tour of the worksite by iterorganization
• Welcome to Planet ITER...
[2] M. Reinhart et al., “Latest results of Eurofusion plasma-facing components research in the areas of power loading, material erosion and fuel retention”, Nuclear Fusion 62, 042013 (2022).
[3] ITER Cryopump www.iter.org/newsline/-/2721
[4] The first high-speed colour video from the COMPASS tokamak
• The first high-speed c...
[5] Aerial photo of Culham Science Centre, UK Atomic Energy Authority,
ccfe.ukaea.uk/about-ccfe/hist...
[6] ITER view, ITER Organization/EJF Riche
www.iter.org/org/ITERinFrance
[7] National Ignition Facility's target chamber
commons.wikimedia.org/wiki/Fi...
[8] S. Das, “Recent advances in characterising irradiation damage in tungsten for fusion power” SN Applied Sciences 1, 1614 (2019).
[9] K. Niu, “Nuclear Fusion”, (CUP 1989). ISBN: 978-0-521-11354-0
[10] B. Labit et al., “Experimental studies of the snowflake divertor in TCV” Nuclear Materials and Energy 12, 1015 (2017).
[11] Nuclear power plant in Cattenom, France (User: Stefan Kühn)
commons.wikimedia.org/wiki/Fi...
[12] Advanced Test Reactor by Argonne National Laboratory,
commons.wikimedia.org/wiki/Fi...
[13] J. E. Menard et al. “Fusion nuclear science facilities and pilot plants based on the spherical tokamak”, Nuclear Fusion 56, 106023 (2016).
[14] Carbon fiber laminated sheet (User: Racingjeff)
commons.wikimedia.org/wiki/Fi...
[15] Raíl de ferrocarril en Roma, Gotland (User: Bene Riobó)
commons.wikimedia.org/wiki/Fi...
[16] S. M. Gonzalez de Vicente et al., “Overview on the management of radioactive waste from fusion facilities: ITER, demonstration machines and power plants” Nuclear Fusion 62, 085001 (2022).
[17] Core of the BR2 reactor by Dmitry Terentyev (SCK CEN: Belgian Nuclear Research Centre)
www.iaea.org/newscenter/news/...
[18] ITER Assembly - In-Vessel components by iterorganization
• ITER Assembly - In-Ves...
[19] Remote handling work inside the JET Tokamak by EUROfusion
[20] X. Hu et al., “Transmutation-induced Precipitation in Tungsten Irradiated with A Mixed Energy Neutron Spectrum” Acta Materialia 165, 51 (2019).
[21] M. Rubel et al., “Application of Ion Beam Analysis in Studies of First Wall Materials in Controlled Fusion Devices” Physics 4, 37 (2022).
[22] Side view of a rack of billiards balls being broken (User: MarkBuckawicki)
commons.wikimedia.org/wiki/Fi...
[23] L. L Snead et al., “Irradiation Effects on Dielectric Mirrors in Inertial Fusion Power Reactor Application”, Fusion Science and Technology, 56, 1069 (2009).
[24] B. I. Khripunov et al., “Thermonuclear Fusion Reactor Plasma-Facing Materials under Conditions of Ion Irradiation and Plasma Flux”, Symmetry 13, 2081 (2021).
[25] J. Chen et al., “Study on microstructural evolution and constitutive modeling for hot deformation behavior of a low-carbon RAFM steel”, Journal of the Material Research Society 32, 1376 (2017).
[26] Roman Husák et al., “ODS EUROFER Steel Strengthened by Y-(Ce, Hf, La, Sc, and Zr) Complex Oxides”, Metals 9, 1148 (2019).
[27] IFMIF/EVEDA Website, www.ifmif.org/gallery/
[28] www.statista.com/
[29] Physics of Uranium and Nuclear Energy,
world-nuclear.org/information...

[@ImprobableMatter]

This is the last video in this series. A version without backing music is available here: www.dailymotion.com/video/x8kzsg2 The educational videos like this one are now under the Creative Commons licence for anyone that might appreciate this.

[@johncarr5442]

I have just recently discovered your series of videos on Fusion. I find them exceedingly clear and useful, I am dismayed that this is the last, there seems to be a lot more to say. The current situation with fusion seems to be changing fast; there are large numbers of private start-ups as well as public projects in the UK in particular, all with non-mainstream technologies. It looks like ITER is heading for enormous delays at best and disaster at worst. You obviously are able to make detailed assessment of all this mess, why not do so with more videos?

[@ImprobableMatter]

@@johncarr5442 I will make more specific videos, but that is all for this general fusion series.

[@AndrewMellor-darkphoton]

Dang it no more physicists rambling

[@timboatfield]

_Those that say something can't be done, shouldn't interrupt those who are doing it._

[@fburton8]

This is the opposite of dumbing down. I love it!

[@gustavchambert7072]

Agreed. We definitely need more "smartening up"-type content when it comes to science.

[@monkeshdevekar6670]

Yes smart-up videos should rule.

[@Splarkszter]

The key of making the world a better place is education and not holding back information. We need to make sure education like this becomes even more and more accesible!

[@slightlytwistedagain]

Your approach to teaching fusion technology through the hurdles it is currently facing as well as the proposed problem solving has been far more entertaining and dare I say it, educational than any science class I've taken.

[@kieranhosty]

Thank you so much for making these videos. A lot of youtube content is understandably vague about nuclear fusion due to inexperience of the creator or simplification to tired explanations of the basic physics for new audiences, but this content really helps explain the reality behind so many articles and videos. This is valuable work, thank you making this and going to extra mile to clearly communicate where so many others have failed.

[@whatelseison8970]

So true. I find fusion extremely fascinating but I'm growing very weary of the stale, recycled, surface level factoids that make up the vast majority of videos related to the topic. This series has been a breath of fresh air by comparison, even with all the bubble-bursting honesty.

[@johnarnold893]

Understandably vague because nobody and I mean nobody knows how to make it work. So far it's all just sci-fi and will likely stay that way. If humanity had invested the same amount of money into MSR's we would have had cheap safe nuclear power decades ago.

[@Optable]

That's because nobody actually reads research papers, where so much beautiful content lies in wait... waiting to be plagiarized for the greater good

[@berndgrabitz]

This shows clearly why we need to work on solutions which will at least reduce emissions today. Fusion may be working further on, but just sitting and waiting is not an option. Remember folks even the most pessimistic predictions may be fare to optimistic, we just don't know.

[@vipondiu]

Another excellent explanation. I always redirect people to your channel whenever someone talks or discusses fusion, for a realistic overview. Your 3h video is the most condensed course on the topic I've ever listened to, and I recommend it to everyone that wants to understand the current state of fusion and its challenges

[@ImprobableMatter]

Thanks!

[@fnorgen]

This is without a doubt one of the best series on youtube!

[@Airwave2k2]

God damn you could read me a telephone book for lullaby. But seriously the effort you put in this and to make the points very good to follow and holding off with conclusions for the audience to make is outstanding.

[@harmenkoster7451]

Great video, just want to point out that at 22:00, while a fission reaction would certainly stop at that point, that does not neccesarily make it better than conventional fission power plants. Fission power plants are already designed to be subcritical and rely on decay neutrons to keep the reaction going. A reactor that has an accident will almost instantly kill any chain reaction. However, it's not the chain reaction directly that's dangerous with a fission power plant disaster. It's all the decay products. Those decay products are chock full of low lifetime radioactive junk which puts out a ton of heat as it decays. Sure, its not as much as the main reaction, but plenty to melt the entire reactor into slag if the coolant systems fail. A combined fusion fission reactor would have the same issue. The neutron source would stop, but the decay products would remain and if this scheme was intended to produce any power, the decay products would be plenty to melt your entire reactor into the ground.

[@ImprobableMatter]

Great point.

[@Airwave2k2]

Melt down, in the moment what temperatures are we talking about? Like enough to make those products into vapor? A slug, like the foot in Chernobyl is less of an issue - just a localized problem. Having radioactive material vaporized and dispersed in the atmosphere would come down to a big problem.

[@harmenkoster7451]

@@Airwave2k2 It depends on the exact geometry and the size of the molten down core slag. If it ends up like a blob surrounded by insulating materials it'll get way way hotter than if it spreads out into a thin layer of rubble. The decay products toss out a constant power output regardless of the state of the meltdown, which means that its equilibrium temperature depends entirely on the heat rejection capacity of the core. But, since plenty of those reaction products are gasses, or else have very low boiling temperatures, they would easily escape and contaminate the atmosphere. Iodine 131 would boil out of the melted down core as a vapor at only about 180 degrees. Caesium would follow at about 700 degrees etc. So a meltdown is gonna spew radioactive junk everywhere almost regardless of temperature.

[@Airwave2k2]

@@harmenkoster7451 I guess now when you mention it I could have looked up vaporization temperature of common fission products like those you mentioned. Thanks for writing out the obvious I wasn't able to see.

[@dsdy1205]

I'd like to correct your terminology if you don't mind - subcritical means that even with decay neutrons, the neutron balance per reaction is less than 1. What you are mentioning is simply called "critical", where the neutron balance including subsequent decay neutrons is greater than 1, but the prompt neutron balance, which only considers neutrons from fission reactions, is below 1. There's a step above that which is prompt criticality, where the neutron balance of the fission reactions alone is greater than 1. At this point your nuclear reactor graduates into a nuclear bomb.

[@entcraft44]

I am so happy to see a video like this. Not blindly following the hype, but also not overly pessimistic. In addition, well informed and touching all the most relevant points. Good job!

[@GeoffryGifari]

videos of this kind of length and detail are probably not for everyone, but its nice that they exist for those who need it

[@michaelogden5958]

I avoided this video for several days, thinking it would be another 5th grade "explanation" regarding fusion. This goes way beyond that. Thanks!

[@thesupreme7501]

So far, you are my best content creator when it comes to fusion. It's so simple to understand when you explain it and I'm hoping that you make more videos about how to solve the current problems in fusion energy especially when it comes to stability of plasma in the reactor.

[@benfowler1134]

This is rather awesome. As somebody who is feeling a little burnt out studying for a physics degree after being inspired by a visit to JET, it helped me feel excited by physics again, despite the real talk about the prospects of fusion in the near term. Thank you!!

[@michaeldepodesta001]

Thank you. Very informative, and focussed on gritty reality, your talks are the antidote to the hype of extreme "fusionistas".

[@richard0crewe]

This series of videos has been excellent. Thank you for making the technicalities accessible without leaving me with the feeling I've been watching dumbed-down content.

[@sorenstirling8795]

This is the finest presentation of nuclear physics on KZbin. Huge congratulations!All the key aspects explained in a fantastically concise manner

[@Elucidator-]

Very down to earth explanation, packed with relevant information. And moreover: free of hype. Thank you for making this!

[@antaresmc4407]

Nice, I think this may be the best video in the series so far, and not just because it alone is like 40% off the total length XD Even though it only briefly scratches the surface, it's not dumbed down or wrong "for the sake of simplification", that sort of not treating the audience like idiots is surprisingly rare in the fusion community :/ and I love how you fill that gap :)! This time (about engineering) it's more of my cup of tea, and specially with how large and dense this episode was, the thing I most missed is a good medium to discuss it (there were mentions of a Discord in the stream and a comment in the past, is that idea still a thing?)... I do have some criticisms though, mostly minor ones having to do with the specific examples and way of speaking about various issues; for example the neutron issues in a fusion reactor are not thrice as severe as those of a fission one, more like thrice in magnitude ;3 due to not only increased neutron count but reduced absorption, much higher energy, harder machinery, etc; and that reflects in how fundamentally different the engineering approach must be... Just a few nitpicks like that that I think could be better communicated, the video is excellent c: The mechanical and thermal stresses, as well as how different fusion schemes cope with the mentioned challenges is something that would have been There was one point that was worth noting as incorrect tho, subcritical reactors are not inherently safe and instantly shutting fission down is very easy, standard practice since before I was born; with most of the risk comes from decay heat of the extremely radioactive short lived fission products, which would definitely be just as much of an issue in a hybrid reactor. Furthermore, I don't think talking about it as a safety feature in the specific context of a fission blanket is fair, since that massive hole will want to plug itself if overheating or damage makes it collapse... Hybrid reactors are quite interesting, but not for that reason... Imo it's specially important because nuclear safety is a topic beat to death and still somehow always trivialized in the ways that made historical accidents happen (except for the scaremongers, which let's just ignore). "It's fine" is the mentality that caused most nuclear accidents and is disgustingly common in science commuunication, I think that as a youtuber with a reputation of not dumbing things down there should be a bit extra care in this specific topic :). Lmao I've wasted way too much time on such a few second tangent! As a last thought: the topic of running, repairing, maintaining and extracting the power from such a reactor, as well as all the associated isotopic separation, lasers (if inertial), diagnostics, etc would be a great follow up video as this one already teased it quite a bit, and to be honest the core where the blaze is contained gets too much love and the (most of the) rest of the facility barely talked about outside the dedicated papers...

[@antaresmc4407]

What a textwall lol. And it feels like nothing was said XD

[@ImprobableMatter]

I totally agree about the subcriticality part - that is definitely the biggest "dumbing down" part. To be fair, the latest fission designs are very safe.

[@antaresmc4407]

@@ImprobableMatter they are indeed! To be fairer, older ones are too. The scariest part of a nuclear power plant is her manager, neglecting or delaying upgrades, cutting corners, etc... The reactor needs to be handled very stupidly to pop, and in a gen-3 PWR you almost need evil to even put it at risk as the operator, let alone as the engineer... The politician or owner tho, that guy will pull you a Fukushima every time you let them XD Hopefully, the 4th gen will have cheaper, simpler and more modular safeties so that they are less at risk of being neglected, less thorium melt plug bullshit (not that they're bad, but so much discussion for missing the point..) and more looking at passive decay heat removal, more compact heat sinks, low pressures, underactive fuel and coolant elements... Back to the hybrid reactor concept, the first thing that comes to mind is their versatility, able to breed and burn almost anything they want... Pretty sure that'll have no proliferation issues whatsoever >:3

[@DavidBeaumont]

The material science involved in creating the containment chambers is just astonishing. Neutron irradiation and embrittlement in things like heat exchangers is a lifetime's work to solve.

[@dosgos]

Great video series. Education that is a lot of fun to watch. The script and video refinement is fantastic.

[@semidemiurge]

Excellent explanation and at a perfect level of technical/scientific detail. Thank you

[@busyonthefarm]

That does it. I'm now entirely convinced a matter/antimatter reactor a la warp core is easier than a fusion reactor. Now I've got to retool everything!

[@mikegofton1]

Simply outstanding content, the best source I’ve found on YT for nuclear power.

[@zzasdfwas]

Wow, someone producing videos about fusion who actually knows what they are talking about. It's clear that you are an expert. It's impressive that you are able to see the big picture while knowing a lot of details and even recent advances in the field.

[@NOBOX7]

fantastic work sir , i watched it all and even went back to listen again to interesting parts

[@websterl.william106]

Val You made my fucking day. I am the reason your fusion playlist has more vies in the last few months I love your shit thank you.

[@ImprobableMatter]

Thanks a lot.

[@JoeOvercoat]

@@ImprobableMatter Webster’s enthusiasm is palpable. 👍

[@Xylos144]

Excellent video as always. A very tiny nitpick is, when suggesting fission/fusion hybrid plants, the suggested safety advantage came from the fission v target being subcritical and in need of additional neutrons. But I'd contest that that's how (most) fission plants are already built today. The fuel assemblies are subcritical and require the neutrons to be moderated to achieve criticality. When you make the moderator the same material as the coolant (water) that not only gives the primary feedback mechanism that supplies the power control, but it renders continued fission impossible under any adverse event that can cause a loss of coolant. The remaining danger, as it is, to both fission and fission/fusion hybrids is the removal of ongoing decay heat from the fission daughter products rather than any persistent fissioning. To solve that problem, passive coolant loops would be needed for both scenarios. (or in my opinion, a reversal to liquid fuel/coolant combos, allowing the fuel to be translocated to more favorable storage or heat-rejection vessels) are necessary.

[@ImprobableMatter]

Yes, I totally agree and have had several comments pointing this out. I definitely think that a proper 3rd or 4th gen fission plant is very safe.

[@Xylos144]

@Improbable Matter ah, my apologies then for the redundancy. Thanks again for adding to this video series. While the simplified 'science communicator' videos have their place, the real potential of the internet is giving a platform where experts can actually provide details, explanations, and context beyond simple popsci awareness.

[@JoeOvercoat]

If we’re lucky Tom Cruise will make an action movie that revolves around a nuke plant operating on that principle, so that it will be more widely recognized.

[@guytech7310]

Pointless as the world is running out of economically recoverable Uranium. There is only sufficient economically uranium to get to about 2050 at current consumption. Plus most of the Worlds uranium comes from Russia & with the luke warm NATO-Russia war there is no way Russia is going to be source for Uranium fuel. Second Utilities aren't interested in building new nuclear power plants including fission. Most utilties already know about the pending Uranium shortages coming. Plus it take about 20 years in planning, construction, and testing for new plants, and very few nations even have any long term storage. most of the Spent fuel remains on site at the plant, even after the plant has been fully decommissioned.

[@droach3183]

oh my i am first love your stuff btw as far as i am aware this is the best stuff i found on yoututube for an honest and accurate explination of fusinon its problems and how it might be solved

[@artherladett442]

So much more complicated than I thought. I want to study this for sure

[@ciCCapROSTi]

This is so informative while being approachable, without the popsci pitfalls that usually accompany such videos. Even has some humor. Great stuff, m8!

[@Growlizing]

Thank you for making such a great video. You are very good at explaining this at a level I can mostly understand with high school chemistry and physics.

[@adriaancanter4573]

Thank you very much for investing your time and energy to educate people on this subject. I had no idea that fusion would produce so much radioactive waste in practice, with maybe different but headaches on par with fission. I know several people who think fusion is right around the corner now. I'll point them to your channel. It never occurred to me that water *itself* could be made radioactive by manufacturing it with tritium. That made the hair stand up on the back of my neck. Thanks again!

[@ImprobableMatter]

At the JET experiment, there are boxes in the bathrooms to collect urine samples from some of the engineers. These would be tested for Tritium (in the water). A future power plant would likely have to have a similar arrangement.

[@JoeOvercoat]

@@ImprobableMatter Your reply made me feel a little sick to my stomach. Yikes!

[@Bruh-vp6qf]

It's a safety measure, people have such a phobia around radioactivity

[@erikh8685]

Amazing. I can't believe this kind of information is free. Thanks for sharing!

[@DocSineBell]

Thanks for making this. I love it. I always wondered what are the engineering problems surrounding fusion, and now I'm starting get a glimpse of it.

[@sonkefh]

It is an absolute miracle what humanity has discovered to date. We live in an incredible age. Humanity will progress further if the complex problems of this time are distributed among many brains. You have done a great job for a better future. Thank you very much.

[@xgozulx]

This was such a great explanation and summary of the problems of this technology, I loved it, thank you so much for making these videos:D

[@torinor6703]

Clicking on one of your videos is like rewatching a good movie, it never fails to amaze me. Fusion is so much more complicated than what people think of. Im in my 3rd year of electronics engineering, and Im looking into a plasma physics masters for some time in the future. Aneutronic fusion would solve so many of the issues caused by neutron emission if it were an achievable thing. Hopefully it becomes a thing in the near future.

[@zzasdfwas]

Yeah, but aneutronic fusion has its own issues. Bremsstrahlung is too high, so magnets alone won't provide enough energy confinement. I dunno if it's possible to build an super reflective box around the plasma, or make the plasma big enough to be optically thick.

[@Bruh-vp6qf]

Let's deal with 100 million degrees first before we go above a billion!

[@malayrojak]

Gotta say I love the name of the channel. Very cleverly chosen name. Thanks for posting the video - very informative and still accessible information despite being a very niche subject.

[@twpayne]

Thank you so much for your expert insight and fantastic presentation.

[@collemwillst1810]

Great information and presentation, thank you!

[@jorehir]

Superb video. Packed with clear infos.

[@marcovillalobos5177]

Thank you so much for giving this cristal clear explanations of the fusion technology situation

[@Rockefeller.69]

One of the best science channels on YT. I’d say top 3, top 5 100%

[@kitsvn]

Thank you for making this video!

[@kirkhamandy]

Thanks, this video explains why, for all my (long) life, Fusion Power has always been 20 years away.

[@JoeOvercoat]

Right? It’s always been, “The sun runs on fusion!” …while glossing over how very large the sun is, and how rare the fusion events are in that context.

[@robindumpleton3742]

Just a shame Tritium is Unobtanium

[@vitorbortolin6810]

I love your idea of a mix fusion-fission power plant! Can you make a future video on this topic?

[@ImprobableMatter]

Certainly not my idea! Edward Teller, the "father of the hydrogen bomb" thought it was worth pursuing.

[@eckligt]

It's also very similar to accelerator-driven fission reactors. In a sense it's one type of accelerator-driven reactor, except that it has a very exotic accelerator. The "traditional" accelerator-driven reactors use a particle accelerator to bombard a so-called spallation target with protons, which reacts by giving off neutrons (since neutrons are difficult to accelerate in their own right, being neutral). The spallation target is then surrounded by fissile material. The fissile assembly never reaches criticality, so the energy production can be stopped instantaneously by stopping the accelerator. The energy for the accelerator is taken from the electricity produced by the power plant itself.

[@zzasdfwas]

A fusion plant can be used to destroy the long-lived isotopes from fission nuclear waste. And the fusion plant doesn't need to produce energy, because fission reactors already produce the energy. You still have to deal with radioactivity, but "only" for hundreds of years or so.

[@KevinBalch-dt8ot]

@@zzasdfwas - Fission reactors can be designed to do the same and we know they work.

[@Tympan]

“…intense opinions about public health care”…! Love it!

[@lilyp4369]

new improbable matter video, i'm so hyped

[@SplendidKunoichi]

i really do appreciate the background music in these

[@veritypickle8471]

Good lord I forget how much I enjoy these videos

[@michaelcorlet2998]

Finally a reality based presentation with all the grissley bits. Top presentation.

[@kristofferbouchard8395]

Great video series, ive actually watched all 4 a couple times to come to grips with the material as i dont work in this field. Side pt you have a good narration voice youd do a great job narrating documentaries etc.

[@user-nj3jg6if5i]

Yet another excellent video; your videos are by far the most comprehensible explanations of this stuff for laymen like myself that I've found. At some risk of wasting your time, I was left with a few questions: As you mentioned, the irradiation of the tokamak itself means that it will require periodic replacement. If fusion really is the final frontier of energy, then someone managing a plant will eventually neglect it for too long. What happens in that scenario? Also, what sort of timescale would these replacements need to happen on? (As in: years? decades? centuries? Given that new materials are in development, a precise answer doesn't exist yet, but approximately how long do you think it'll end up being?) You mentioned in passing that Tokamak-style fusion was ultimately the way to go, but what do you think about First Light Fusion's projectile approach? If you've even read this far; thank you. I recognize that I'm asking for an expert's opinions to be given for free

[@ImprobableMatter]

Economics dictate that replacement of parts of the fusion reactor (doesn't have to be a tokamak) should be no more frequent than perhaps every few years. If the reactor is having a full shutdown every month... forget it. Once the activated components are removed and maybe processed a little, they can be left to sit "hands off" in a safe location (maybe post some guards). If everything is designed well, they will decay to background levels in 100 years. My criticisms of First Light Fusion are: (1) Instabilities will make energy gain difficult, just as it did for the overconfident Inertial Fusion crowd. (2) Their design will struggle to get a good repetition rate going. They would need to fire in pellets at a rate of at least 1 per second, which with their setup will be tough. (3) The comment at the end "despite the cowboy attitudes of certain startups" is about their CEO. On Twitter, he told me that Tritium breeding is essentially a solved problem. If that is his attitude, then his company - already delayed from their own stated schedule - is in for a rude awakening.

[@user-nj3jg6if5i]

@@ImprobableMatter Thank you! Completely missed that little jab at the end.

[@Bruh-vp6qf]

Haha "solved issue". That's a good one. Even if he has solved the breeding he'll have a hell of a time extracting it efficiently.

[@Yezpahr]

6:38 This joke, with a straight face, earned you an automatic subscribe/like/comment.

[@Edwinthebreadwin]

Thank you for your video, it raises a lot of points I was not aware of. I would be interested to see a video not on just the challenges we face currently but perhaps the challenges of the past and how modern designs have solved these problems. This might provide a way to respect the difficulty of the problem whilst at the same time show optimistically progress is being made.

[@VEC7ORlt]

Solving fusion feels like going to school uphill, in a blizzard, both ways. So so many prerequisites, exotic materials, etc. At this point makes me wonder if we even need it, as an engineer all this just seems impractical, I'd rather apply myself improving energy storage for solar/wind/geo/hydro. Liquid lithium wall reactor? Like what kind of a fever dream is that?

[@sbzguadafoc]

Great video. Thanks for sharing!

[@hedgehog3180]

13:49 I guess it's also nice that those elements happen to be some of the most common or most important in life. If iron was unstable in this situation it could impede the functioning of hemoglobin for example.

[@pizzacrusher4632]

Hooray!! another IM video! Ive been eagerly awaiting it.

[@robertbelcher5068]

Fantastic video. Much appreciated.

[@williamvaughan1218]

Science is awesome as it consistently and endlessly provides more wonderful questions to answer!

[@Dexerinos]

Nice, just found this channel today with this vid and watched everything, YT algo still works at least once a month :) Cant wait to go thru the related channels here and cant wait for more videos from IM!

[@frezzingaces]

Banger series watched the whole lot in one sitting.

[@Lichalfred]

Just a comment - FIrst Wall in not a vacuum vessel, it just prevents plasma to contact other in-vacuum parts. It is IVC (Inner Vacuum Chamber) that ensures vacuum inside

[@ImprobableMatter]

Yes, very good point for e.g. ITER. Some of the proposals and experiments I have to talk about are basically in a single vacuum vessel, so the two are one and the same.

[@gashery]

@06:37 Once again, the deadpan delivery is the key to making me take this whole presentation very seriously.

[@MrRolnicek]

All of this just makes fusion seem like a red herring for any near-future power conversation. Like it's a deliberate distraction from the fact that FISSION can still give us cheap and abundant energy just like promised, we just have to not be lazy building scaled up submarine reactors with giant accumulated overhead in the design and actually roll up our sleeves and make fission a POWER generating device focused on cost, simplicity and safety (though of course simplicity gives us safety and inherent safety reduces extra costs). And I know, research is being done, materials are being tested, the last engineering challenges are all slowly getting solved to do exactly that and 4th gen reactors are expected to already fit into that role, it just feels very anemic. If there was a TRUE concerted effort, it would be done very quickly. And it SHOULD be, current events basically accelerated the timeline of the fossil fuel energy crisis. But I guess the world doesn't work that way anymore. The US doesn't just start a huge industrial effort which yields fast amazing results, that was in the times of the US being the #1 industrial power, rest of the world doesn't seem to want to mimic that either.

[@saumyacow4435]

Both fission and fusion are dead ends economically. The thing that a lot of people haven't noticed is just how fast energy storage technology is maturing. The combination of renewables with energy storage will be mature, cheap and far less risky as an investment.

[@MrRolnicek]

@@saumyacow4435 Well I agree with one thing, I haven't noticed ANY maturation in gridscale storage technologies. All I've seen are technologies that put renewables WAAAY out of economic reach and I genuinely haven't seen any serious progress in the tech. But I would LIKE to notice it, can you point me in the right direction? I've always been saying that we need actual investment in cheap fission (don't bother developing reactors if they aren't going to be cheaper than coal) AND storage to make renewables viable alongside it. I'd LOVE to be proven wrong and see that there actually is investment in half of this blanket solution.

[@ChrisCiber]

@@MrRolnicek But when you are considering if your reactor is cheaper than coal, maybe a good first step would be taxing the coal plant based on how many people it's fumes make sick and how all the productivity lost from the towns that coal mines displace.

[@MrRolnicek]

@@ChrisCiber Yea, in an ideal world maybe. Not going to happen in third world countries for sure and that's where the most demand is coming from now and for the forseeable future.

[@JonMartinYXD]

Let me put on my conspiracy hat for a moment. Fusion is being pushed by fossil fuel companies who are afraid of the new generation of modular fission reactors. The average person thinks fission equals Chernobyl and Fukushima, and fusion equals limitless free clean energy. The fossil fuel companies know that fusion is a long way off, so if they can convince the public to reject fission now and hold out for perpetually just around the corner fusion, large amounts of fossil fuels will still be needed for a long time.

[@mrtspence]

Been waiting for this!

[@CasparGroenen]

Thanks!,for your video (s).

[@luiscecilio8807]

very very good lectures on nuclear fusion. thank you

[@floriankrause7203]

There are some pictures of wrench sockets that have puffed up by multiple millimeters because of neutron swell, the mirror example is good too but seeing metal parts puff up like a pastry really drives home how much of a problem neutron "bombardment" is.

[@langohr9613ify]

As an engineer myself I love this video. For me it seems really hard, because fusion adds a layor of problems, on top on allready hard problems. E.g. the Neutron bombardment limits your choice of materials. So I imagine every component, any bolt, cable, seal, pump, sensor, etc. has to be designed for that.

[@user-lb4yp4sl4y]

I am sixty five. As a young man, I remember a prediction we would have commercially viable fusion power plants by 2000. Based upon this knowledgeable narration I assume I will have long since become dust and bones before it comes on line.

[@pockpock6382]

Very informative and well conveyed. Are you employed in some educational context? You're incredibly good at it.

[@optimist_hr]

great series

[@whynotmike]

At least two companies (general and zap) are pursuing a liquid metal cavity instead of a solid metal reactor wall. On paper this strategy mitigates/solves a lot of the issues you talked about here. You briefly talked about a thin layer of liquid lithium , but I want to know your thoughts on using a thick liquid metal cavity. From this video and your previous ones, it seems like pursuing a reactor design that accomodates a liquid cavity (i.e. not tokamaks) could take 10 yrs off the commercial development timeline.

[@__Dude_]

Yes, it could. And at the same time add 10+ years to harness the technology.

[@Bultish]

Oh Glorious day, greetings from Norway!

[@samuelkurz5814]

I loved the series. Sad to read that this is the last video in the series. But maybe there will be more content about fusion research 🤞

[@eckligt]

Very enlightening! The research must continue, but for the coming century I think nuclear fission is the better bet for energy generation.

[@oneman7094]

We want more!

[@arnecl9566]

I can really appreciate the reference list.

[@B1G_Dave]

I love how you show the difference between science and engineering. All these startups "know" the science, but to actually build a working reactor, that's going to take good old trial and error engineering.

[@Grapheneolic]

very solid video

[@robertfraser9551]

Fabulous ! Obviously a very large number of material advances are required. This has got to require decades of effort yet !!

[@andyherle]

yesssssss i’m looking forwards to this one

[@NoNo-fb7ue]

Will you do a detail video on a fission - fusion hybrid? As it does seem allot more feasible with nuclear waste as a potential fuel at 21:30. Thank you for this fantastic video, it really highlights the problems with building a fusion reactor. Br.

[@QuickM8tey]

I really appreciate your videos man, they help to thoroughly convey the serious challenges behind unlocking fusion energy. In some sense I now feel it's worthy of considering as a "final boss" of energy production. I can't imagine how Helion Energy will supply Microsoft with any meaningful amount of power so quickly. Considering Helion's close affiliation with OpenAI's CEO, Sam Altman, I can only assume that one or both parties believe rapid advancements in AI will be able to solve the many substantial problems that lie ahead. Their expectations can only be described as tremendous and almost utopian given that DeepMind already applied Deep Learning / ML approaches to some problems in the field and from interviews I've seen of Demis Hassabis he spoke as if there were some problems current AI tech was unsuited for.

[@adamludwick9931]

25:56 -- rip stop steel, how cool is that?

[@makeyia100]

Thanks!

[@Japidoff1911]

Bedankt

[@dylanevans1635]

Very good video, I’ve enjoyed the entire fusion series. Having just written an essay on the prospects of future energy production through nuclear fusion, I agree that there doesn’t seem to be a definitive way of generating enough tritium to supply enough fusion reactors to power the world. I believe we should invest more research and development into deuterium-helium 3 fusion

[@Bruh-vp6qf]

If you are concerned about tritium supply wait until you hear about how He-3 is made!

[@Profesor449]

The engineering concepts and challenges of this process are perhaps the most interesting to me. Sure, future can't be predicted, but do you see fusion being viable for power production even a hundred years from now (or any remotely forseeable future)? I feel like the research aspects in the materials and plasma physics are missed by popular depictions of fusion - do any other fields benefit from research of fusion?

[@ImprobableMatter]

There are definitely spinoffs from fusion. More resistant materials, robotics for challenging environments, fundamental plasma physics (which already has industrial applications).

[@vernonbrechin4207]

Many technologically oriented people find justifications for all forms of experimentation, including that involving weapons of mass destruction (MAD), since they all produce numerous spin-off products.

[@JoeOvercoat]

@@vernonbrechin4207 I suggest fusion research greatest profit is going to be in more predictable nuclear weapons. Engineering can’t do anything about making people more predictable, but at least we’ll have a better idea what exactly is going to happen when we attempt to activate a weapon of mass destruction of the nuke variety.

[@vernonbrechin4207]

@@JoeOvercoat - Your perspective applies to the people in many countries who have exercised their special skills in providing those countries with nuclear weapons. It includes nine countries now, including those we regard as our enemies. I'm certain that many technical spin-offs came from just the U.S. development of nuclear weapons. Our use in war resulted in between 110,000 and 210,000 deaths of mostly civilians. Generally techies don't let such thoughts interfere with their highly rewarding work. The U.S. conducted 1,054 critical mass nuclear explosive tests in the quest to create our nuclear arsenal which now numbers over 10,000 nuclear weapons. Most of them now are thermonuclear explosives (H-bombs) that have energy yields in the range of ten times that of the atomic bombs dropped on the cities of Hiroshima and Nagasaki. There are managers who continue to advocate for the resumption of our nuclear testing program. The weapons in our arsenal are very predictable in their operation and energy yield. It varies by less than plus/minus 20%. In exchange for ending our underground test program at the Nevada Test Site (NTS) the Lawrence Livermore National Laboratory (LLNL) got funding for the National Ignition Facility (NIF). It was finished much later than expected and way over budget. It was expected to achieve its primary goal of a break even fusion energy experiment by 2012. It failed by a factor of more than ten to reach that goal. It took another decade of twiking to achieve its original goal. It is estimated that the project has now cost tax payers approximately $11 billion. There is no indication that those failures had any effect upon the performance and reliability of the nation's nuclear stockpile. I find it to be amazing the lengths that technical people go to justify the work that has brought them so much joy. You might be interested in searching for the following article. Counting the dead at Hiroshima and Nagasaki (The Bulletin of the Atomic Scientists)

[@JoeOvercoat]

@@vernonbrechin4207 I suggest that you look into the history of the Japanese government in between the two bombings. Once you understand that I suggest you look into the history of Okinawa, when it was invaded by the Americans.

[@phasorthunder1157]

Thank you for these videos that highlight the challenges of Fusion energy. I will mention that Tritium is produced in CANDU fission reactors as a waste product, so it is currently being sold and there are plans to sell it to those conducting fusion energy research.

[@phasorthunder1157]

Although, it is likely that the quantity is produced is not sufficient for commercial fusion energy production.

[@combrade-t]

Love this, doesn't simplify and explores the problems it faces whilst still being approachable and understandable to someone with base level understanding of the theories behind it. The Many references are also nice, a lot of more widespread videos about fusion are not nearly as academically rigorous.

[@Mrcometo]

8:58 As far I know, this is not form 70´s. At the end of 50´s and in the 60´s some people wondered about direct energy conversion. For example, Richard F. Post at the Lawrence Livermore National Laboratory does some approach at he begining of the 60´s, at least as a way to extract part of the fusion energy. Edit: I forget to congratulate you for your great job. Many thanks

[@guytech7310]

There isn't any real cost effective options for D-T as about half of the energy produced is in the form of fast neutrons. He3 can partially do direct power conversion via alpha emissions, but it would not be efficient. Most of the power generated would still come from heat. However this is all pointless since the cost of a fusion power plant would be at least 50 times that of fission which is already way too expensive.

[@asbjo]

i would love to hear about the engineering, science and viability of MSR reactors. I find the thermal neutron breeding idea to be fascinating, along with the continual operation made possible by the liquid fuel medium.

[@Rhannmah]

21:54 i've always wondered if it would be possible to have a fertile thorium reactor that is kept active by a neutron source such as a fusor or another high efficiency neutron source. Amazing video!

[@JonMartinYXD]

Regarding neutron damage, there is also the Wigner effect to consider. If the reactor is running at a temperature below the annealing temperature of one of the materials suffering atom displacements due to neutron impacts (Frenkel defects), the number of displacements builds up over time. Each Frenkel defect has potential energy, and if there are enough of them, just one atom dropping back into the lattice can release enough energy to trigger more displaced atoms to do the same, and you get a runaway rearrangement of atoms that can release enough energy to make the material explode.

[@josephpiskac2781]

Great science though it appears to have little hope for a useful future technology.

[@Takyodor2]

The more I learn, the better the idea of a fusion/fission hybrid design sounds to me. Wouldn't it make for a safer, cleaner and more efficient design compared to current fission reactors, while making many of the pure fusion reactor issues go away? Great video!

[@craq47]

The general consensus is that it combines the worst of both worlds, unfortunately. You still have long-lived radioisotopes which are a challenge to store after decommissioning. The fissile material is a weapons proliferation risk. The fusion plant still has most of the complications of a pure fusion plant (tritium management, first wall damage... and all the other things this video did a great job of listing).