exploring contingent insights predicting predictive understanding exploring precise forecasts assembling precise predictions computing definitive estimations mapping the future mapping calibrated estimations predicting definitive futures modeling probable contingencies mapping precise predictions computing intelligent insights delivering critical futures forecasting contingent predictions generating contingent contingencies

Question

Metaculus Help: Spread the word

If you like Metaculus, tell your friends! Share this question via Facebook, Twitter, or Reddit.

When will a fusion reactor reach ignition?

Context

Nuclear fusion would give us cheap and abundant energy. Energy is a $8.5 trillion energy industry. It also doesn't emit greenhouse gases (once built), and its residue has a half-life of a few hundred years (much less than nuclear fission). (source) It's also safer as it seems the fusion reactor would be incapable of generating the dangerous runaway chain reactions that lead to a meltdown (source).

On the other hand, "fusion reactors have other serious problems that also afflict today's fission reactors, including neutron radiation damage and radioactive waste, potential tritium release, the burden on coolant resources, outsize operating costs, and increased risks of nuclear weapons proliferation" (source). Also see: Pure fusion weapon — Wikipedia.

Definition

"The fusion energy gain factor, usually expressed with the symbol Q, is the ratio of fusion power produced in a nuclear fusion reactor to the power required to maintain the plasma in steady state. The condition of Q = 1, when the power being released by the fusion reactions is equal to the required heating power, is referred to as breakeven, or in some sources, scientific breakeven.

The energy given off by the fusion reactions may be captured within the fuel, leading to self-heating. Most fusion reactions release at least some of their energy in a form that cannot be captured within the plasma, so a system at Q = 1 will cool without external heating. With typical fuels, self-heating in fusion reactors is not expected to match the external sources until at least Q = 5. If Q increases past this point, increasing self-heating eventually removes the need for external heating. At this point the reaction becomes self-sustaining, a condition called ignition. Ignition corresponds to infinite Q, and is generally regarded as highly desirable for practical reactor designs."

(source: Fusion energy gain factor)

Resolution criteria

If a relevant Wikipedia page states that a fusion reactor has reached ignition, and continues to state that for at least 10 months in a 12 months period, this question gets resolved with the date mentioned on Wikipedia. If Wikipedia isn't active anymore, a paper replicating the fusion reactor ignition will confirm the resolution as the date at which the first paper reported ignition.

Related questions

{{qctrl.predictionString()}}

Metaculus help: Predicting

Predictions are the heart of Metaculus. Predicting is how you contribute to the wisdom of the crowd, and how you earn points and build up your personal Metaculus track record.

The basics of predicting are very simple: move the slider to best match the likelihood of the outcome, and click predict. You can predict as often as you want, and you're encouraged to change your mind when new information becomes available.

The displayed score is split into current points and total points. Current points show how much your prediction is worth now, whereas total points show the combined worth of all of your predictions over the lifetime of the question. The scoring details are available on the FAQ.

Note: this question resolved before its original close time. All of your predictions came after the resolution, so you did not gain (or lose) any points for it.

Note: this question resolved before its original close time. You earned points up until the question resolution, but not afterwards.

This question is not yet open for predictions.

Thanks for predicting!

Your prediction has been recorded anonymously.

Want to track your predictions, earn points, and hone your forecasting skills? Create an account today!

Track your predictions
Continue exploring the site

Community Stats

Metaculus help: Community Stats

Use the community stats to get a better sense of the community consensus (or lack thereof) for this question. Sometimes people have wildly different ideas about the likely outcomes, and sometimes people are in close agreement. There are even times when the community seems very certain of uncertainty, like when everyone agrees that event is only 50% likely to happen.

When you make a prediction, check the community stats to see where you land. If your prediction is an outlier, might there be something you're overlooking that others have seen? Or do you have special insight that others are lacking? Either way, it might be a good idea to join the discussion in the comments.