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Chinese Tokamak reaches over 100M degrees

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Re: Chinese Tokamak reaches over 100M degrees

#231

Post by pfdietz »

quotemstr wrote: post #203
dmos62 wrote: post #90

Can someone comment on what kind of economic effect that working fusion reactor technology would have? I hear sometimes contradictory hear-say on the lines of "unlimited energy", "reactor would have to be fed constantly".

I'm not sure that it would have a profound effect at all. Fission is very power dense as well and fission fuel cost is not the primary driver of overall costs in existing nuclear designs. Fusion might end up looking a lot like fission, but hopefully with a lower perceived safety risk and thus more public acceptance. Granted, modern fission designs aren't actually unsafe, but that doesn't matter for PR purposes.

Fusion is going to look a lot like fission, only much more expensive and much less reliable.

Re: Chinese Tokamak reaches over 100M degrees

#232

Post by pfdietz »

jeffreyrogers wrote: post #191
dbingham wrote: post #186

Earlier quoted context omitted.

I dunno, my buddy who just got a degree in high energy plasma physics working on fusion reactors might disagree with you. And really, you just sound like every crank ever who thought X technology was totally unfeasible and always would be -- until it wasn't. So currently attempts haven't found a solution to the reaction vessel destruction problem. That does not mean someone in the future couldn't figure that one out.

OP at least gave a reason: neutron radiation destroys the reaction vessel. No one who's responded has given any evidence for why this is false.

Neutron radiation, plus the unfortunate geometric fact that the surface area/volume ratio of a fusion reactor will be low, compared to the fuel rod surface area/volume ratio in a fission reactor.

What this does is ensure that even operating right at the limits of neutron damage to the wall materials, the volumetric power density of a DT fusion reactor will suck. And that will destroy the economics.

Re: Chinese Tokamak reaches over 100M degrees

#233

Post by pfdietz »

DennisP wrote: post #202
w323898 wrote: post #182

Fusion was, and for the foreseeable future will be, a boondoggle. In the US it was a cold-war-era arms race program intended to scare the USSR and have them overextend, and now the Chinese are using it for propaganda and scientific Keyensianism. The fact is, fusion generates neutron radiation that destroys the reaction vessel, making it an unviable technology. Nobody takes it seriously as a source of energy, aside fr…

In MIT's ARC design, the reactor is designed so you can easily open it up and replace the inner vessel. The vessel is 3D-printed and replaced once a year. Surrounding the inner vessel is a molten salt mixture which breeds more fuel from lithium but is otherwise unaffected by neutron radiation. This is a regular tokamak design, with a high chance of success since we understand tokamaks very well at this point. Various…

A single ARC reactor will use 40% of the world's annual production of beryllium.

The power density of an ARC reactor will be around 0.5 MW/m^3. In comparison, the power density of a PWR reactor vessel is 20 MW/m^3.

Replacing the entire inner vessel once a year would be an operational nightmare. For one thing, it ensures the building the reactor is in will have to be very large, with very large secondary bays where the intensely radioactive material of a spent reactor vessel can be moved and disassembled (generating radioactive fragments and dust).

Re: Chinese Tokamak reaches over 100M degrees

#234

Post by pfdietz »

voxl wrote: post #184
w323898 wrote: post #182

Fusion was, and for the foreseeable future will be, a boondoggle. In the US it was a cold-war-era arms race program intended to scare the USSR and have them overextend, and now the Chinese are using it for propaganda and scientific Keyensianism. The fact is, fusion generates neutron radiation that destroys the reaction vessel, making it an unviable technology. Nobody takes it seriously as a source of energy, aside fr…

Oh sorry, we didn't realize that you completely understand all of physics and can qualify, without any possibility of error, that any configuration, period, that utilizes fusion will necessarily be impossible because of this physical restriction.

For DT fusion, that's been known for 35 years. It's not just materials, it's power density.

http://www.askmar.com/Robert%20Bussard/The%20Trouble%20With%...

Re: Chinese Tokamak reaches over 100M degrees

#235

Post by exikyut »

basil-rash wrote: post #183
marcosdumay wrote: post #98

Earlier quoted context omitted.

Well, there is almost certainly somebody that read the number and thought about Fahrenheit.

Or read it and think it's some very prolific Chinese university. Not that I'd be that stupid. No way.

Of course I wouldn't be that stupid either.

Re: Chinese Tokamak reaches over 100M degrees

#236

Post by pfdietz »

glbrew wrote: post #109
maaaats wrote: post #95

Earlier quoted context omitted.

> "100M degrees" (Kelvin) Off topic, but this distinction made me laugh. Like the difference between Kelvin and Celsius would throw everything off.

In his defense he was commenting on the difference between Kelvin and KeV.

The latter was named after Lord KeVin.

Re: Chinese Tokamak reaches over 100M degrees

#237

Post by DennisP »

pfdietz wrote: post #233
DennisP wrote: post #202

Earlier quoted context omitted.

In MIT's ARC design, the reactor is designed so you can easily open it up and replace the inner vessel. The vessel is 3D-printed and replaced once a year. Surrounding the inner vessel is a molten salt mixture which breeds more fuel from lithium but is otherwise unaffected by neutron radiation. This is a regular tokamak design, with a high chance of success since we understand tokamaks very well at this point. Various…

A single ARC reactor will use 40% of the world's annual production of beryllium. The power density of an ARC reactor will be around 0.5 MW/m^3. In comparison, the power density of a PWR reactor vessel is 20 MW/m^3. Replacing the entire inner vessel once a year would be an operational nightmare. For one thing, it ensures the building the reactor is in will have to be very large, with very large secondary bays where th…

We don't produce much beryllium because we use need much. It's about a fourth as prevalent in the Earth's crust as boron, for example.

http://periodictable.com/Properties/A/CrustAbundance.al.html

Re: Chinese Tokamak reaches over 100M degrees

#238

Post by pfdietz »

DennisP wrote: post #237
pfdietz wrote: post #233

Earlier quoted context omitted.

A single ARC reactor will use 40% of the world's annual production of beryllium. The power density of an ARC reactor will be around 0.5 MW/m^3. In comparison, the power density of a PWR reactor vessel is 20 MW/m^3. Replacing the entire inner vessel once a year would be an operational nightmare. For one thing, it ensures the building the reactor is in will have to be very large, with very large secondary bays where th…

We don't produce much beryllium because we use need much. It's about a fourth as prevalent in the Earth's crust as boron, for example. http://periodictable.com/Properties/A/CrustAbundance.al.html

Boron, however, is more easily concentrated (in evaporites). Beryllium is found in pegmatites, which are less common. The estimated resource (not reserve) of Be is 100,000 tons (USGS). This would be enough for ARC reactors supplying just 1% of current world primary energy demand. The estimated world resource of boron is in excess of 1 billion tons.

https://minerals.usgs.gov/minerals/pubs/commodity/beryllium/... https://minerals.usgs.gov/minerals/pubs/commodity/boron/mcs-...

Re: Chinese Tokamak reaches over 100M degrees

#239

Post by pfdietz »

pfdietz wrote: post #238
DennisP wrote: post #237

Earlier quoted context omitted.

We don't produce much beryllium because we use need much. It's about a fourth as prevalent in the Earth's crust as boron, for example. http://periodictable.com/Properties/A/CrustAbundance.al.html

Boron, however, is more easily concentrated (in evaporites). Beryllium is found in pegmatites, which are less common. The estimated resource (not reserve) of Be is 100,000 tons (USGS). This would be enough for ARC reactors supplying just 1% of current world primary energy demand. The estimated world resource of boron is in excess of 1 billion tons. https://minerals.usgs.gov/minerals/pubs/commodity/beryllium/... https…

Correction: the deposits are mostly volcanogenic, not pegmatitic. However, they still aren't very common.

Re: Chinese Tokamak reaches over 100M degrees

#240

Post by frob »

quotemstr wrote: post #204
Cthulhu_ wrote: post #48

Earlier quoted context omitted.

I read in another thread that the radiation in that dissipates in about 30 years, vastly preferable to the tens of thousands of years of nuclear fission waste. I don't know how strong the radiation is either, whether it's more or less dangerous than fission waste.

The way radioactivity works, the faster a substance decays, the more dangerous it is. Something being slightly radioactive for ten thousand years is much better than some searing-hot exotic isotope sitting around for 40.

Not really. The big issue is with long-term deterrence, not short-term. It is fairly easy to isolate something for 30/50/100/200 years. It is much harder to isolate something from future humanity with a high level of certainty for 200,000 years. Even things with low levels of radioactivity will kill you if ingested and do a lot of harm if kept near. The problem of communicating this to future humans is a big one. How do you keep future humans who may not have the level of technology we have from deciding that the magic, glowing, heating stone is a source of healing and prosperity instead of something to be avoided?
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