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0 pointszdragnar3y ago0 comments

Construction costs for fission are largely bloated due to safety, activist and political concerns that span the realm of pragmatic and necessary to pure fantasy as well.

Aneutronic fusion would (hopefully) bypass a lot of that.

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7 comments · 3 top-level

htag3y ago· 2 in thread

* The safety is massively different than fission because there is no 'run away' reaction. If you turn off the power, fusion will stop. Fission will keep going once started, and can be very dangerous if the cooling system fails.

* I do believe the fusion paths Helios is using emit neutrons, which is a big safety concern. Not only is neutron radiation directly deadly to humans, it's also a challenge to maintain containment. Neutrons are not magnetic, so matter must be used as a shield. Most materials that absorb a neutron will itself become radioactive. I'm unsure about the number of neutrons Helios is emitting, or will emit as they scale up.

DennisP3y ago

Their combined D-D/D-He3 reaction will emit 6% of its energy as neutron radiation, compared to 80% for D-T. Mostly they'll be lower-energy neutrons, and it's only a 50MW reactor. They don't plan to make it bigger, just to make lots of them.

They're considering doing the D-D reaction in a separate reactor to produce the He3. The D-He3 reaction is purely aneutronic, and while some D-D will still happen, they can tune it so it doesn't happen much. That would mean very little neutron radiation at the power plants.

htag3y ago

> The D-He3 reaction is purely aneutronic, and while some D-D will still happen, they can tune it so it doesn't happen much. That would mean very little neutron radiation at the power plants.

Yea. I'm just very curious as to what these numbers look like in practice. Neutrons are essentially waste emissions with their plan, but physics and engineering constrains will determine how much they can tune out D-D reactions.

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rcpt3y ago· 2 in thread

When it becomes clear that fusion can displace coal those safety, activist and political concerns will immediately pop up again

DennisP3y ago

And any country that chooses to keep using a dirty, unhealthy, more expensive, 250-year-old energy supply over helium-3 fusion will rapidly fall behind.

rcpt3y ago

Ok but that's a different story.

Just look at what's going on with solar https://twitter.com/ArmandDoma/status/1656323112349179907

Yes in theory it should be easy to shut these people up with fusion but historically it hasn't been.

DennisP3y ago

In fact, even for D-T fusion the NRC recently decided to regulate reactors like accelerators instead of like fission reactors.

Also, we never mass-produced fission reactors. Helion wants to build a factory making twenty 50MW reactors per day, shippable by rail.

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7 comments · 3 top-level

htag3y ago· 2 in thread

DennisP3y ago

htag3y ago

> The D-He3 reaction is purely aneutronic, and while some D-D will still happen, they can tune it so it doesn't happen much. That would mean very little neutron radiation at the power plants.

1 more reply

rcpt3y ago· 2 in thread

When it becomes clear that fusion can displace coal those safety, activist and political concerns will immediately pop up again

DennisP3y ago

And any country that chooses to keep using a dirty, unhealthy, more expensive, 250-year-old energy supply over helium-3 fusion will rapidly fall behind.

rcpt3y ago

Ok but that's a different story.

Just look at what's going on with solar https://twitter.com/ArmandDoma/status/1656323112349179907

Yes in theory it should be easy to shut these people up with fusion but historically it hasn't been.

DennisP3y ago

In fact, even for D-T fusion the NRC recently decided to regulate reactors like accelerators instead of like fission reactors.

Also, we never mass-produced fission reactors. Helion wants to build a factory making twenty 50MW reactors per day, shippable by rail.

j / k navigate · click thread line to collapse