5 ms·

Note: they did not achieve "commercial fusion" (Q-total > 1), they set a temperature record among commercial fusion companies. (Still cool though!)

by ed 5y ago

ReptileMan 5y ago
The opposite of cool. Literally
deutschew 5y ago
damn...got all excited
dang 5y ago
OK, we've put that phrase in the title above. Thanks!
omgJustTest 5y ago
Tokamaks, while cool (or hot!), are ultimately limited by materials that we know about. There are IAEA reports for fusion calling for materials that survive >100 displacements-per-atom (DPA) and > 1000deg C[1]. Additionally you might also need highly controllable super-conducting magnets as well as advanced sensing of the instabilities of the fusion plasma to ensure they are well confined (a chief requirement for fusion). There are other problems, but these are typical issues with tokamak-based fusion devices. Chiefly most tokamaks around the world do not operate in "continuous mode", ie they operate on "shot mode" or short duration experiments to attempt to ignite the plasma to fusion conditions. Achieving high-duty cycle operation with a ignited plasma is its own hurdle. Making hot plasmas is interesting, but if your technology requires the above, you are looking at around 4-5 once-per-decade material science results. Every national lab in the US is saying we are out of time, we need existing energy solutions to avoid the worst of climate change. Source: I am a nuclear engineer. [1] https://www.sciencedirect.com/science/article/pii/S1369702109702949#fig4 https://www.sciencedirect.com/science/article/pii/S136970210...
- deleted 5y ago
  [deleted]
- DennisP 5y ago
  CFS has demonstrated magnets that seem to be up to the job, using REBCO tape. They'll replace the inner wall annually, so it doesn't need to be as durable. MIT already demonstrated practical joints in the tape. We certainly need to decarbonize as fast as we can without waiting for fusion, but if we're lucky then fusion might make things easier down the road.
  - omgJustTest 5y ago
    These are certainly superb scientific results. The problem is that even 1 DPA is significant for structural materials, and is basically a nightmare for electrically or mechanically sensitive ones. For example light-water fission reactors achieve about 50 DPA to their reactor pressure vessels over their 40-50 year lifetime. Its hard to imagine that anything called a super-conductor could maintain Cooper-pairs after getting the average atom displaced from its original position. Additionally CFS ran at 20 Kelvin... which again is hard to imagine happening at scales other than CERN-like efforts (ie one-of-a-kind installs): "In September 2021 Commonwealth Fusion Systems (CFS) created a test magnet with ReBCO wires in which flowed a current of 40,000 amperes, with a magnetic field of 20 tesla at 20 K." [1] Edit: Also magnets have 1/R^3 field die-away, in direct competition with 1/R^2 particle dispersion die-away.... meaning your magnets control better as you make cavities smaller, however it also means the magnets get much more DPA :(. [1] https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide
    - pfdietz 5y ago
      Magnets are highly shielded from neutrons in a fusion reactor. The real problem is the first wall, which necessarily is not shielded. Materials are an ongoing problem, and it's not just dpa. Abdou at UCLA pretty convincingly argues that increasing dpa of wall materials isn't even the most pressing problem; reliability of the wall/blanket is. http://www.fusion.ucla.edu/abdou/abdou%20presentations/2018/Abdou%20CFETR%20Presentation%2011-27-2018%20Final%20V50.pdf http://www.fusion.ucla.edu/abdou/abdou%20presentations/2018/... I should add that fusion neutrons add a problem beyond that experienced in fission reactors: the neutrons are sufficiently energetic that production of helium by (n,alpha) reactions in materials is a serious issue. The helium migrates to small very high pressure bubbles that break materials from the inside.
greggsy 5y ago
Every time a fusion story makes the headline, the first comment always reminds me that the story is wrong
- aero-glide2 5y ago
  How is the story wrong?
  - 1_player 5y ago
    Apparently the original title was more clickbaity and it's been changed to a more objective one.
jve 5y ago
When they don't mention Q in article, I always assume it is <1. If they do, well, then no need to assume. When Q>1 times come, we will then have to assume Qtotal < 1 until explicitly mentioned. As there are losses along the way and heat must be converted to electricity.
- baggiponte 5y ago
  What is Q?
  - detaro 5y ago
    ratio of energy_out/energy_in

Note: they did not achieve "commercial fusion" (Q-total > 1), they set a temperature record among commercial fusion companies. (Still cool though!)

by ed 5y ago

Note: they did not achieve "commercial fusion" (Q-total > 1), they set a temperature record among commercial fusion companies. (Still cool though!)

ReptileMan 5y ago

The opposite of cool. Literally

deutschew 5y ago

damn...got all excited

dang 5y ago

OK, we've put that phrase in the title above. Thanks!

omgJustTest 5y ago

Tokamaks, while cool (or hot!), are ultimately limited by materials that we know about. There are IAEA reports for fusion calling for materials that survive >100 displacements-per-atom (DPA) and > 1000deg C[1]. Additionally you might also need highly controllable super-conducting magnets as well as advanced sensing of the instabilities of the fusion plasma to ensure they are well confined (a chief requirement for fusion). There are other problems, but these are typical issues with tokamak-based fusion devices. Chiefly most tokamaks around the world do not operate in "continuous mode", ie they operate on "shot mode" or short duration experiments to attempt to ignite the plasma to fusion conditions. Achieving high-duty cycle operation with a ignited plasma is its own hurdle. Making hot plasmas is interesting, but if your technology requires the above, you are looking at around 4-5 once-per-decade material science results. Every national lab in the US is saying we are out of time, we need existing energy solutions to avoid the worst of climate change. Source: I am a nuclear engineer. [1] https://www.sciencedirect.com/science/article/pii/S1369702109702949#fig4 https://www.sciencedirect.com/science/article/pii/S136970210...

deleted 5y ago
[deleted]
DennisP 5y ago
CFS has demonstrated magnets that seem to be up to the job, using REBCO tape. They'll replace the inner wall annually, so it doesn't need to be as durable. MIT already demonstrated practical joints in the tape. We certainly need to decarbonize as fast as we can without waiting for fusion, but if we're lucky then fusion might make things easier down the road.
- omgJustTest 5y ago
  These are certainly superb scientific results. The problem is that even 1 DPA is significant for structural materials, and is basically a nightmare for electrically or mechanically sensitive ones. For example light-water fission reactors achieve about 50 DPA to their reactor pressure vessels over their 40-50 year lifetime. Its hard to imagine that anything called a super-conductor could maintain Cooper-pairs after getting the average atom displaced from its original position. Additionally CFS ran at 20 Kelvin... which again is hard to imagine happening at scales other than CERN-like efforts (ie one-of-a-kind installs): "In September 2021 Commonwealth Fusion Systems (CFS) created a test magnet with ReBCO wires in which flowed a current of 40,000 amperes, with a magnetic field of 20 tesla at 20 K." [1] Edit: Also magnets have 1/R^3 field die-away, in direct competition with 1/R^2 particle dispersion die-away.... meaning your magnets control better as you make cavities smaller, however it also means the magnets get much more DPA :(. [1] https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide
  - pfdietz 5y ago
    Magnets are highly shielded from neutrons in a fusion reactor. The real problem is the first wall, which necessarily is not shielded. Materials are an ongoing problem, and it's not just dpa. Abdou at UCLA pretty convincingly argues that increasing dpa of wall materials isn't even the most pressing problem; reliability of the wall/blanket is. http://www.fusion.ucla.edu/abdou/abdou%20presentations/2018/Abdou%20CFETR%20Presentation%2011-27-2018%20Final%20V50.pdf http://www.fusion.ucla.edu/abdou/abdou%20presentations/2018/... I should add that fusion neutrons add a problem beyond that experienced in fission reactors: the neutrons are sufficiently energetic that production of helium by (n,alpha) reactions in materials is a serious issue. The helium migrates to small very high pressure bubbles that break materials from the inside.

greggsy 5y ago

Every time a fusion story makes the headline, the first comment always reminds me that the story is wrong

aero-glide2 5y ago
How is the story wrong?
- 1_player 5y ago
  Apparently the original title was more clickbaity and it's been changed to a more objective one.

jve 5y ago

When they don't mention Q in article, I always assume it is <1. If they do, well, then no need to assume. When Q>1 times come, we will then have to assume Qtotal < 1 until explicitly mentioned. As there are losses along the way and heat must be converted to electricity.

baggiponte 5y ago
What is Q?
- detaro 5y ago
  ratio of energy_out/energy_in