MIT Club of Northern California
11 HN recommenders · recommended in 18 months, 2016–2024
1:38:49 · 1.1M views · Feb 25, 2016
MIT's Prof. Dennis Whyte explains the ARC/SPARC compact tokamak approach, in which new high-temperature superconducting magnets allow smaller and cheaper fusion reactors. He covers fusion physics, performance trends and the engineering path to net energy.
HN points to it as the grounded, approachable explanation of why REBCO magnets changed the outlook for fusion.
20 comments from Hacker News
> “People say nuclear is expensive in the West, but they forget to say it’s expensive because of interest rates,” Morin said. It's still a valid criticism if: - They could get those high interest rates from the return on other capital projects (nuclear less return than something else) - All externalities are included in costs We only have so much labor/material/energy available, and we do have to have some way of allocating them to the things with the most return. The big issue, obviously, is that tons and tons of negative externalities aren't priced in to most economic endeavors, that might make fission look a lot better. It might make it look a lot worse. Personally I'm hoping Elon/Mackenzie/Gates/Buffet/etc decide to throw a few dozen billion at fusion. I think its time truly is nigh. If you haven't watched this yet, it's definitely worth your time. Rather than being a super opinionated think-piece, it instead does a fantastic job walking the viewer through: - high level nuclear fusion engineering performance curves / the engineering design contraint space - the current state of nuclear fusion research (as of 5 years ago) and - breaks down why some new smaller reactors will likely begin construction soon and counter-intuitively, the most recently started ones may be completed before a fusion reactor that first broke ground 25 years ago and is still very much being actively built this video Also worth noting that interesting things happen when you assume you can have "large" a
Watch Robert Whyte's presentation. this video The basic problems have all been solved, the science has been solved too. Tokamaks have already made net fusion power. The only difference between JET, which already succeeded, and ARC, is using Magnets with 2.6x the field strength. The B^4 power scaling, gives you about 50x the power, so ARC will generate 500 MW of power whereas JET (remember, already proven engineering), generated 10MW. So without a doubt, this is just an engineering problem at this point. A prototype device that didn't have to be maintained, could be built exactly like any other Tokamak, just with REBCO magnets, and you'd have the required fusion power. To get the required electric power, and add in maintenance, you need to at the FliBe liquid blanket, replacable toroid sections, and a heat exchanger, but again, these are known engineering problems with known solutions, akin to knowing that landing a rocket is possible, but figuring out the grid fins, heat shield, landing legs, and guidance software. Fusion devices on a small scale have been proving the plasma physics since the 90s. We don't have fusion yet simply because of people being conservative and sticking with traditional "known to work" magnets, which is why ITER is a huge, hulking monstrosity. As Dr Whyte says, cost scales by R, R can be reduced by a factor of 10 from ITER simply by using different magnets, so ARC will produce the same power as ITER, but significantly smaller and cheaper. The basic paper
Commonwealth Fusion Systems has addressed all of those issues: 1. The higher field strength from the new HTS magnets eliminates turbulence. 2. The ARC reactor will use a FLiBe molten salt blanket to capture energy from neutrons and breed tritium to be used in the fusion reaction. 3. The ARC reactor is designed to have a swappable 2cm thick vacuum chamber, which is the component subjected to the most neutron radiation (everything else is shielded by the molten salt blanket). These chambers are expected to last a year, and while they are moderately radioactive waste, the amount of material is relatively small and they should become safe in the order of a decade. I highly recommend watching Dr. Whyte's talks on YouTube, he discusses the challenges, design, and performance in an approachable way. There's a timestamp index in the comments on this video: this video
In total a land area about the quarter of the size of California was contaminated with over 37 becquerel of radiation due to Chernobyl, including 10,000 farms in the UK alone. The solitary story was to get people to read the book. The debate is if fission is sustainable for the environment. I talked about contaminated agriculture and how much that was covered up and missing in the statistics — people still living in contaminated land and eating contaminated food today. “The huge numbers of people” is what I’m concerned about and why I advocate for wind and solar. I’m not in favor of the fossil fuel status quo. The radiation and pollution from coal ash and effects of global warming on agriculture are massive. But that’s not an argument for “fission is ecologically sustainable”, that’s an argument for “even though it’s not, we should still build dams and fission power plants anyways”. Which is a fine argument. It’s just a different one. A fission disaster or attack on a fission plant can take half of Californias agriculture out of the picture over night. You can’t say fission and wind have similar risk at the tail ends. Yeah, statistically it hasn’t happened, but the risk exists. Besides, new fission plants will take 20 years to build and by then we'll have actually clean baseload energy from fusion reactors. This video[0] is from 7 years ago, but it provides an amazing breakdown of the physics of fusion energy. The timeline and physics predicted in the lecture have come to pas
I’ve been following them since they were giving promising lectures at MIT and I absolutely think they have the most solid approach! Tokamaks are well understood, they supposedly have the same plasma physics as ITER which has been heavily scrutinized and supported by work at JET, and their concept is simple - Tokamak but with very high field superconducting magnets using technology that wasn’t available when ITER was conceived, and apparently higher field strengths mean a smaller reactor for the same power gains. As a lay person the story is simple and that’s good! Then they demonstrated their magnets and got $2B in funding and now they’re deep in the construction phase for SPARC. I encourage anyone curious to look up videos on SPARC on YouTube. It’s very encouraging! It seems honestly very reasonable that they will see sustained net energy gain for their entire power plant before 2030 (tho SPARC is still a demonstrator not designed for continuous service, so “sustained” means like one minute). Here’s some videos: 8 years ago: this video 2 years ago: this video Latest update posted yesterday: [LINK]