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Comment by arethuza | Hacker News Reader

ITER seems to be addressing the "capture the energy" part?

https://www.iter.org/sci/MakingitWork

"The neutrons will be absorbed by the surrounding walls of the tokamak, where their kinetic energy will be transferred to the walls as heat. In ITER, this heat will be captured by cooling water circulating in the vessel walls and eventually dispersed through cooling towers. In the type of fusion power plant envisaged for the second half of this century, the heat will be used to produce steam and—by way of turbines and alternators—electricity."

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And without breeding blankets, yes you can capture the heat, but you rapidly run out of tritium. ITER will only be operate on DT for a few weeks, total over its lifetime, before the available tritium supply is exhausted (and its materials reach their neutron limits).

A "real" reactor will need to have tritium breeding blankets to regenerate the tritium. Otherwise, the cost of tritium alone, if made in fission reactors, for a 1 GW(e) DT fusion reactor would be $15B/year.

Isn't testing that approach of breeding tritium explicitly part of what ITER is trying to do with its TBM programme?

ITER has a few places where test blanket modules can be installed. ITER will not be able to simulate the neutronic environment of a full reactor (and so will not be able to confirm adequate breeding), nor subject the modules to the cumulative neutron loading they will have to withstand.

For this reason, a Fusion Nuclear Science Facility has long been proposed as something that will be needed before DEMO is built. This could be a small, Q < 1 DT fusion device, as the goal would not be plasma physics related. It itself will need to breed its own tritium to operate long enough, so there's a circular dependency in the development.

There are many such technology advances needed for fusion power to work. This is why spending $22 billion on ITER is a very inefficient use of money for research. Maybe as a diplomatic effort of having all the world's major powers [] (China, the European Union, India, Japan, Korea, Russia and the United States) work together it is worth it. Sort of like the space station. Big symbol and cost but little scientific value per dollar.

Unfortunately the budget for ITER comes out of the US science budget instead of the State Department. Most US fusion funding only goes to ITER at this point.

Fusion blankets are not just needed for fusion to work, they are needed for the next fusion reactor experiment (the one that has a burning plasma) to run. This is not a technology that we'll need some day for commercialization; it's a requirement for DT fusion to progress at all.

That's not capturing in a utility sense, it's merely preventing system failure from overheat (edit: autocorrect was turning this into "merrily preventing" which was kind of fitting as well). The result is a high volume, low delta-T coolant cycle and those are notoriously difficult (read: impossible) to capture meaningful amounts of electricity from, it will actually consume a lot. That quote is just a slightly more elaborate way of saying: no, we'll definitely not do any utilizeable capture.

How is what they just said any different than a standard nuclear reactor that just heats up water to produce steam into electricity?

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