Archives for posts with tag: fusion

Fox News recently ran a story on a young boy who seems to have set up a tabletop fuser. Impressive kid. https://www.foxnews.com/science/teen-builds-working-nuclear-fusion-reactor-in-memphis-home

Here is a better article: https://www.commercialappeal.com/story/news/2019/01/28/beifuss-file-memphis-youth-jackson-oswalt-builds-home-nuclear-fusion-reactor/1977266002/

And there is this: http://discovermagazine.com/2010/extreme-universe/18-do-it-yourself-basement-fusion

If deuterium is injected into a 20k- to 50k-volt vacuum, it will ionize and some of it might fuse. If it is fusing, half will result in tritium and a proton, and half will result in helium-3 and a 2.45 MeV neutron. The D-T might fuse to helium with a 14.1 MeV neutron, and the D-He3 can fuse to helium and a proton (but it needs a much higher temperature to matter). Temperatures are near a billion degrees, so too high to imagine. Given a good vacuum, there is nothing to heat except the injected deuterium, and since there is so little of it the extremely high electrical energy input results in extremely high temperature for the very few atoms.

High enough vacuum and high enough electrical energy should make it possible, but I’m skeptical.

Bubble neutron detectors are reported as reliable for a few months after manufacture.

https://inis.iaea.org/collection/NCLCollectionStore/_Public/34/083/34083281.pdf and Youtube videos available. The neutron bubble tubes should bubble only for neutrons (and stray cosmic rays), not x-rays or other likely background radiation.

So, again, it should be doable, and fresh bubble neutron detectors should be reliable, but I remain skeptical.

The bottom line for me, putting a few thousand dollars and oodles of hours into generating a few bubbles in a dosimeter which will remain unconvincing to someone who worked in nuclear fission and fusion science, well, it just isn’t impressive as hobbies go. I do suppose there are very many options that would be more time consuming, more expensive, and less rewarding, so to each his own.

What would convince me would be regular checks of the vacuum equipment with a regular Geiger counter. Once it is reading significantly, then I’d believe you were fusing atoms and generating neutrons that activated your steel. But then, all you have to show for it is a high electric bill and the hassles of disposing of low-level radioactive waste.

Putting together a high-vacuum system is nontrivial.

Detecting protons outside the vacuum chamber is impossible because the chamber walls absorb them. X-rays are plentiful because the ionized deuterium smacking the chamber walls causes x-rays. Nothing nuclear required. So, the only evidence of fusion is neutrons. Given there are reliable ways to detect neutrons, proving fusion isn’t terribly hard, but neutrons with megaelectronvolts energy are true nanocanons. Most of the neutrons produced will be absorbed by the vacuum chamber walls, but many will get through, especially through a viewport. MeV neutrons do extensive damage (on a nanoscale) to anything they hit, including you. Working with the fusion device will give the user significant radiation dose. So, knowledge of useful safety precautions is advised.

Back to the kid who prompted my thinking, his setup is impressive. I’ve worked with such vacuum systems, and the challenges are daunting. A turbopump is a difficult and finicky machine. (It is an electric jet engine working opposite as one does on an aircraft; it sucks instead of pushes.) I know what would be involved with the electrical system, but I’ve never worked with that level of voltage. The young man’s accomplishments are significant. I suspect he has a solid radiation-safety knowledge, too. (And his parents probably did their homework, too.) All in all, good stuff.

Will amateur accomplishments in fusion, in combining deuterium into tritium and helium isotopes, lead to breakthroughs in energy production? I can’t imagine how. It might lead to some technically skilled and ambitious people who do other good things. I’ll stay hopeful.

I’ve seen more news on fusion power generation lately. Among the various claims, a company in Britain seems to think they can run D-T fusion in a tokamak as small as 1.5 meters.

I doubt it. I really doubt it.

D-T is almost certainly what we will use on earth and, perhaps, the moon, and D-T produces material-damaging 14 MeV neutrons. The neutrons also activate the materials, meaning the entire power unit becomes radioactive waste.

A sufficiently small D-T unit may be able to run longer because it will have low structural requirements, but the neutrons embrittle the materials such that the steel (or other material) walls become easy to break, like glass. At some point, the power unit is not structurally sound. It becomes unsafe and must be decommissioned, dismantled, and disposed of as radioactive waste–all of it.

Fusion power of some sort will be the only significant source of power at some point in humanity’s future, but it is not clean and not limitless. That mostly means it will always be expensive with high engineering requirements. It has very significant engineering and safety challenges, including environmental impacts. Granted, most of these challenges are likely to be easier to deal with than other power options, but it is simply false and misleading to suggest that fusion will be clean and inexhaustible.

We will burn fossil fuels for the foreseeable future. (The alternative is mass murder on the order of a billion people.) Nuclear fission will dominate in coming decades, for decades, perhaps for a century or two, then fusion. Once fusion is working, and we overcome the startup and growing pains, then it will be the only significant source of our energy needs for as long as humans do what humans do. I just happen to think generations of us will pass from this earth before the first gigawatt-hour of consumer-electricity is generated by fusion power reactors.

“obtain the holy grail of everlasting green power generation: self-sustaining fusion.”

 makes that whopper quoted above at http://www.extremetech.com/extreme/181298-the-uk-will-be-the-first-to-break-even-with-fusion-power-leading-us-towards-a-future-of-clean-infinite-energy

ExtremeTech doesn’t strike me as a first-rate news source, but I’m sure they try.

Regardless, even in the article, they are talking years away. The article practically admits that fusion is still 20 years away, as it has been for about 70 years now.

Fusion is not a pipe dream. It will power our lives eventually, but it is still likely to not happen within the lives of our children, even grandchildren.

I will have to look into why they’ve installed a beryllium first wall, but everyone realizes beryllium is highly toxic, right? It is extremely expensive too.

We shall see how JET completes its life, but rest assured its death will be an ordeal. The entire facility will be classified as radioactive waste. How’s that for environmentally friendly? Highly radioactive and highly toxic? Again, we shall see.

ITER may prove out, but it too will have a short life and tedious death. Materials advancements are the key, not the physics. That is just an engineering problem now. It is making the things well enough to operate safely for decades that is so impossible right now. Not to mention what do we do with a radioactive building when we are done with it.

So, fusion is inevitable, but never buy the line about “clean and inexhaustible.” Neither is true with the methods and materials we are trying so far.

 

The Guardian claims, “Nuclear Fusion – Your Time Has Come” (Jeff Forshaw), Wired claims it is, “One Step Closer to Breakeven” (attributed to ScienceNow). Well, unfortunately, “practical commercial” fusion power generation has been “perhaps as little as 20 years away” for a little over 70 years now, and that is still true, and, in my humble opinion, will still be true 40 years from now. Sooner or later, we will figure it out. It is almost certainly the primary energy source for all functions on earth and in space for our posterity. We owe it to them to work at it in good faith, but in good sense too! Fusion will not solve our current problems, nor will it help our children. We will have to work something else out for now, and perhaps our great grandchildren will see it come on line in practical ways that make societal life better. It seems to me reasonable to speculate that the first practical fusion power station will be built on the moon. I doubt anyone thinks we will have a moon base started in as little as 20 years.

The Wikipedia article covers things reasonably, but I’ll add my first hand knowledge here. My biggest gripe about fusion is all the articles perpetrate the fantasy that fusion power will be “clean and inexhaustible.” If you believe that, I have a bridge I could sell you cheap.

What is clean about a system that uses radioactive tritium? What is clean about a building, a whole freaking building, becoming radioactive? Read the wiki for the basics, but get it through your head that this ain’t clean. Safe is a relative term. I think the fusion systems I have studied should be safe enough, as long as you don’t nap in them during refurbishment cycles. Waste disposal with ITER will be a problem. JET will be a problem. They are already using remote handling for everything there. Several minutes of Google search haven’t found me any documentation, so from memory, and I’ll appreciate comments that correct me or point me to documentation, but the TFTR of Princeton Plasma Physics, while a solid overall success, ran for only several seconds of actual fusion, and when they shut it down, it was over two years before they could safely go in and decontaminate and decommission it. They ended up burying nearly the entire lab full of equipment (barge loads) in the Hanford desert. Battelle ran it if I recall, and it was done on time and under budget. Stellar for government work! (Though Battelle has a good record for such. Good on ’em.)

Now to “inexhaustible,” did I mention tritium? Oh, yes, I did. Where do we find tritium? Oh, I remember, we don’t! There isn’t any. We have to make it out of lithium via neutron radiation. So far, we do that in regular nuclear fission reactors, but it seems certain we will be able to produce it in place within the fusion reactors, well, at least notionally it will work. The engineers still have to find a way to make it practical. Since it is not hard to make tritium, no problem, right? Think again. Lithium is just a little bit rare, and we have lots of uses for it besides just burning it up in fusion reactors. So, it certainly is NOT inexhaustible. Of course, deuterium is the other fuel component, and D-D fusion is probably not much harder than D-T fusion, so maybe we can do it without the tritium, but don’t forget that deuterium is still relatively scarce, being only a tiny fraction of the hydrogen on our planet. Good thing the planet is mostly covered in water. Certainly there is plenty of deuterium, but we do have it chemically tied up in our oceans. That is an easy engineering problem, but it is still energy intensive to get it out.

My point is that fusion, like fission, like burning carbon fuels, has plenty of waste products to deal with, and it will always take lots of effort to get the active ingredients away from mother nature, and into our reactors. So, TANSTAAFL.

As to the physics, that is fairly easy. Keep experimenting, and keep the mathematicians working it, we will do it. However, then the engineers have to take over and actually design and build one of these things, and engineers go to jail when things go wrong because people die. Accordingly, engineers are predominately practical and safety minded.

First extreme engineering problem with a tokamak is extracting energy from vacuum–no, not zero point, but superheated plasma at hard-vacuum pressure levels. It will work, but it is a hard problem, which means expensive and likely requiring lots of maintenance. Second extreme problem is plasma instabilities that blast the inner walls. Same as the first problem. We will come up with good solutions with an acceptable set of compromises, but it will be costly both initially and in upkeep. The third problem is harder, and so far, intractable. We must build the system to tolerate 14 MeV neutrons. Lithium blankets may be part of the solution, as the lithium will absorb many of the neutrons and generate the tritium we need, but 14 MeV neutrons do things that seem unbelievable. The wiki article talks about it, but just know that we don’t have materials that can meet the needs of dealing with such energetic and destructive missiles. The simplified version of what happens is that in less than two years, most of your structural components will embrittle to the point that they are no safer than if they were made of plate glass. Of course, these neutrons cause the atoms to become radioactive themselves. Thus, the whole building becomes radioactive waste.

I’m getting rather rambly at this point, so I will stop. I will add that I support fusion research. We will do it some day. It will be all we do for power eventually. In the meantime, we need more fission nuclear reactors (uranium, plutonium, and thorium), and we need to keep working on our efficiencies of burning carbon fuels. Drill, dig, pipe, and burn, baby, burn.

CO2 is an essential ingredient of life. So, CO2 is a good thing. Besides, cold kills, warmer is better.

 

%d bloggers like this: