Why is nuclear fusion so hard? • Hacker News Board

Re: Why is nuclear fusion so hard?

#41

Post by mannykannot » Sun, Dec 09, 2018, 4:27 PM UTC

This is somewhat tangential to the specific issue here, but I was surprised by this:

At the center of the Sun, fusion power is estimated by models to be about 276.5 watts/m3. Despite its intense temperature, the peak power generating density of the core overall is similar to an active compost heap, and is lower than the power density produced by the metabolism of an adult human.[1]

So practical fusion power requires producing much higher power densities than are found in the Sun.

[1] https://en.wikipedia.org/wiki/Solar_core#Energy_conversion

Re: Why is nuclear fusion so hard?

#42

Post by thoughtstheseus » Sun, Dec 09, 2018, 4:32 PM UTC

candiodari wrote: post #38

martythemaniak wrote: post #22

Earlier quoted context omitted.

I don't think you're fully aware of the facts (not "propaganda") of nuclear. Old fission reactors are the silent workhorses of our civilization and without them we'd be a much much deeper trouble than we already are. Had previous administrations invested more in fission, climate change would be a much smaller and more manageable problem today. Nuclear has other advantages over solar as well, such as not requiring the…

Yeah this is something people keep forgetting. The reason fossil fuels have such an impact is because the industry is happening at such a scale. Solar and wind are working at miniscule size ... and ... "no" impact (well, wind clearly has impact already, but ... let's forget that). Well actually, solar does have an impact. In Spain there's a couple large wind farms I visited and ... not that it should surprise anyone…

Regarding solar placement, we can place panels on housing and commercial buildings and parking spaces. Check out canopy style parking covers(sun protection)in the southern US.

Re: Why is nuclear fusion so hard?

#43

Post by Creatccount » Sun, Dec 09, 2018, 4:33 PM UTC

Would zero gravity be helpful in order to make it easier to get fusion working?

Re: Why is nuclear fusion so hard?

#44

Post by hwillis » Sun, Dec 09, 2018, 4:48 PM UTC

FlyMoreRockets wrote: post #31

Retric wrote: post #19

Earlier quoted context omitted.

Base load power is not a useful feature. To follow the demand curve you generally what to turn massive amounts of production off at specific points in the day, base load is simply what you keep running during those periods. Nuclear power plants for example where known to be hard to throttle which was a significant design issue. Historically, the tradeoff is worth it as the cost per kWh was less, but again not a usefu…

I used to be a reactor operator and never saw any evidence they were hard to throttle. That's why they are used for warship propulsion: loads in battle are not predictable by their nature, what with changes in course, catapult launches, etc.

You're both right- technically, nuclear reactors are on of the fastest-ramping sources available. A reactor in SCRAM can drop down to However, zero reactors are capable of doing so economically. The cost of a nuclear plant is in its construction, upkeep, and staff. Those costs are the same at 110% and 30% output, but revenue isnt. In order to turn a profit a nuclear plant needs to be running at 80%+, 24/7.

Ultimately that means nuclear needs batteries almost as much as solar and wind, since only ~30% of grid energy is constant 24/7. This should be no surprise- all three technologies have nearly no reliance on fuel, and are funded pretty much upfront. If you have no marginal costs then your only rational option is 100% output.

Re: Why is nuclear fusion so hard?

#45

Post by martythemaniak » Sun, Dec 09, 2018, 4:52 PM UTC

thoughtstheseus wrote: post #42

candiodari wrote: post #38

Earlier quoted context omitted.

Yeah this is something people keep forgetting. The reason fossil fuels have such an impact is because the industry is happening at such a scale. Solar and wind are working at miniscule size ... and ... "no" impact (well, wind clearly has impact already, but ... let's forget that). Well actually, solar does have an impact. In Spain there's a couple large wind farms I visited and ... not that it should surprise anyone…

Regarding solar placement, we can place panels on housing and commercial buildings and parking spaces. Check out canopy style parking covers(sun protection)in the southern US.

I once did my own calculation to answer the question: "How much land do you have to cover with solar panels to meet Toronto's electricity needs". The answer: about 3.5x the size of the city. Covering every square inch of the city is not sufficient, you need a lot more land.

You can double-check my calculations: take the output of largest solar farm installations, note their land area, adjust for solar radiation at your chosen location/latitude, then use the target city's electricity consumption to see how many of these solar installations will be required. Note, I'm talking solely about land-use requirements here, not cost/battery requirements etc.

So covering cities in solar would work great if the overall electricity mix was 50% nuclear for base load, 50% solar/wind/hydro for peak times, but relying heavily on solar will bring its own issues.

Re: Why is nuclear fusion so hard?

#46

Post by mikeash » Sun, Dec 09, 2018, 4:54 PM UTC

mannykannot wrote: post #41

This is somewhat tangential to the specific issue here, but I was surprised by this: At the center of the Sun, fusion power is estimated by models to be about 276.5 watts/m3. Despite its intense temperature, the peak power generating density of the core overall is similar to an active compost heap, and is lower than the power density produced by the metabolism of an adult human.[1] So practical fusion power requires…

That also shows why fusion power always centers around exotic isotopes like deuterium and tritium rather than plain hydrogen. The reaction paths needed to fuse plain hydrogen are so improbable that they don’t happen fast enough to be useful.

Re: Why is nuclear fusion so hard?

#47

Post by vegetablepotpie » Sun, Dec 09, 2018, 4:54 PM UTC

candiodari wrote: post #38

martythemaniak wrote: post #22

Earlier quoted context omitted.

I don't think you're fully aware of the facts (not "propaganda") of nuclear. Old fission reactors are the silent workhorses of our civilization and without them we'd be a much much deeper trouble than we already are. Had previous administrations invested more in fission, climate change would be a much smaller and more manageable problem today. Nuclear has other advantages over solar as well, such as not requiring the…

Yeah this is something people keep forgetting. The reason fossil fuels have such an impact is because the industry is happening at such a scale. Solar and wind are working at miniscule size ... and ... "no" impact (well, wind clearly has impact already, but ... let's forget that). Well actually, solar does have an impact. In Spain there's a couple large wind farms I visited and ... not that it should surprise anyone…

I think Fission would be great if we had somewhere to put the waste, if it didn't cost $10 billion dollars to set up a plant and people weren't phobic of it. Overall Nuclear makes more sense than coal and arguably more sense than wind and solar. But then there's the risk of the meltdown. No politician, no utility CEO, no corporation commission is going to take the risk of a meltdown when the political cost of pumping just a little more CO2 into the air is very small.

Re: Why is nuclear fusion so hard?

#48

Post by stareatgoats » Sun, Dec 09, 2018, 4:57 PM UTC

shawnz wrote: post #14

stareatgoats wrote: post #11

Earlier quoted context omitted.

> nuclear fission could be safer per kWh than wind and solar. Sounds completely improbable. Care to provide some reference to back that statement up?

Some examples of research that has reached this conclusion: https://www.iaea.org/sites/default/files/publications/magazi... https://www.nextbigfuture.com/2011/03/deaths-per-twh-by-ener... It might sound improbable if you are comparing from a purely technological point of view. But the reality is that the energy output of nuclear is so much higher than other technologies, it easily makes up for any increase in risk by…

You fail to mention that Herbert Inhaber's article was published in the International Atomic Energy Agency (IAEA) Bulletin in 1979 [1] (before Three Man Island), drawing from his study published the same year which was heavily criticized even at the time [2] and does not take the problem of nuclear waste into account at all, and otherwise dis-ingeniously cherry-picked number of deaths associated with each energy source up to that point.

The second article you quote is just a blog, and the conclusions are just as dubious, for example trying to weigh falls during roof construction into the risks of solar etc.

edit: removed confusing statement about fission/fusion

[1] https://www.iaea.org/publications/magazines/bulletin/21-1

[2] "Perhaps the most damaging criticism was that the study was inconsistent in applying the methodology to the various energy technologies. For example, while Inhaber considered materials acquisition, component fabrication, and plant construction in his analysis of unconventional energy sources and for hydro power, critics have claimed that he did not follow the same approach for coal, nuclear power, oil, and gas. Furthermore, critics claimed that the labor figures for coal, oil, gas, and nuclear power included only on-site construction, while those for the renewable energy sources included on-site construction, materials acquisition, component manufacture."

https://www.researchgate.net/publication/267817006, page 31.

Re: Why is nuclear fusion so hard?

#49

Post by TheOtherHobbes » Sun, Dec 09, 2018, 4:58 PM UTC

candiodari wrote: post #38

martythemaniak wrote: post #22

Earlier quoted context omitted.

I don't think you're fully aware of the facts (not "propaganda") of nuclear. Old fission reactors are the silent workhorses of our civilization and without them we'd be a much much deeper trouble than we already are. Had previous administrations invested more in fission, climate change would be a much smaller and more manageable problem today. Nuclear has other advantages over solar as well, such as not requiring the…

Yeah this is something people keep forgetting. The reason fossil fuels have such an impact is because the industry is happening at such a scale. Solar and wind are working at miniscule size ... and ... "no" impact (well, wind clearly has impact already, but ... let's forget that). Well actually, solar does have an impact. In Spain there's a couple large wind farms I visited and ... not that it should surprise anyone…

Your facts appear incorrect.

Renewables consistently produce more than 60% of Portugal's energy needs, and have topped 100% on occasion. The figure for Spain is more than 35%, and more than 35% of electricity consumption in Germany.

I'm not sure how you get from 60% to "no impact". It's really quite a puzzling statement.

As is the suggestion that windfarms cause some kind of ecological blight to farmland. Not only is there no scientific basis for that claim, but if it were true, anti-wind propagandists would surely have jumped on it and made sure they mentioned it at every possible opportunity.

Perhaps you have some independent evidence to back you beyond the "couple large wind farms in Spain" you visited?

Re: Why is nuclear fusion so hard?

#50

Post by kingkongjaffa » Sun, Dec 09, 2018, 4:59 PM UTC

kjar wrote: post #3

For most of my life fusion has been teased but not delivered. fission has been pimped for decades yet cannot get private funding, or build reactors in a decade, or provide solutions for the waste. Yet still the industries persist with their propaganda while renewables beat them in cost and time to operation. If I managed the funds I'd cut nuclear and redirect to wind and solar immediately.

Wow this is an insane view point, I actually thought you were going to suggest the opposite...

Frankly the potential capability of nuclear far outweighs anything else.

If the gen public were more on board with it, nuclear could be rolled out and be the main source of power in the world in 30-40 years, removing the need for fossil fuels for power generation.

Even building them in remote locations and taking the transmission losses would be better than diving head first into wind and solar, do you have any idea how destructive the mining is to get the elements required for some of the solar and wind solutions?