New 'Stellarator' Design for Fusion Reactors

eldavojohn writes "The holy grail of fusion reactors has always seemed 'just a few years off' for many decades. But a recent design enhancement termed a 'Stellarator' may change all that. The point at which a fusion reactor crashes is when particles begin escaping due to disruptions in the plasma. A NYU team has discovered that coiling specific wires to form a magnetic field may contain the plasma. This may be a a viable way to create a plasma body with axial symmetry, and a far better chance of remaining stable. Like other forms of containment this does require energy itself, but could bring us closer to a stable fusion reactor. It may not be cold fusion or 'table top' fusion but it certainly is a step forward. The paper is up for peer review in the Proceedings of the National Academy of Sciences."

Comments

Princeton 1951 called...

[Anonymous Coward]

...they want credit.

If they used...

[jd]

...Axl symmetry, they could produce something that was violently unstable but produced vast amounts of marketable energy and money.

Re:If they used...

[Anonymous Coward]

The whole thing is a huge CON and a case of lifetime 'jobs for the boys' - a bunch of overblown assholes who aren't remotely interested in finding a CHEAP energy source - they want a CENTRALISED energy source that a government can completely control.

We already can get ALL the energy we need from renewable sources - ITER and its ilk are just money pits, and guess who pays for this bullshit? The PUBLIC.

It's always "It'll be ready in 50 years' time". i.e. in 50 years' time, they'll STILL be saying "It'll be ready in 50 years' time".

Re:If they used...

[heinousjay]

I hope you're serious, I take great solace in knowing the world is full of crazy people.

Re:If they used...

[jd]

I don't - they keep getting elected. What we don't need right now is more crazies in power. What we need is someone so totally and utterly insane, they'll spend two or three trillion dollars a year on getting a full-scale fusion reactor built and operational before they get kicked out of office or shot. Yes, there are many unsolved problems, but we're running a little low on time and researchers are too busy on corner cases that might never happen in a real reactor under normal conditions. Building a live system and requiring the scientists to live within blast radius would likely get faster results and just as much reliability.

Re:If they used...

[Dachannien]

If they used Axel symmetry, it would fight crime, too.

Re:If they used...

[The_Wilschon]

Blast radius my foot. A fusion reactor is immensely safer than a fission reactor. Furthermore, fission reactors are really very safe (far safer than, say, oil refineries). Even Chernobyl was primarily a /chemical/ explosion (although caused by problems with the reactor), which happened to scatter radioactive debris over half the globe. A chemical explosion at a fusion plant would scatter hydrogen. Oh boy. Even the unstable isotopes of hydrogen are still light enough that they would float to the top of the atmosphere and escape into space in very little time. A fusion reactor is not a controlled H-bomb. Unlike a fission reactor, which requires a carefully tuned reaction to walk the knife's edge between dying out and going critical, the hard part with fusion is keeping it going. Fusion is very fussy. If the density, and the temperature, and the composition of the plasma are not just exactly right, then reaction dies out in a fraction of a second, the time it takes to exhaust the really tiny amount of fuel that is available to it at any given time. To keep it going, you have to keep feeding it more fuel, as well as carefully tuning things. If there were even a very very tiny explosion, the worst it would do is damage the devices tuning the plasma's parameters, and then the reaction would die out. Even if the fuel feeders went crazy and started flooding hydrogen in as fast as they could, it would still just die out. There is no way that the reactor, even in an undamaged state, could bring enough hydrogen to the needed density and temperature quickly enough to cause a thermonuclear explosion even on the scale of a pipe bomb. So, I say, blast radius my foot, unless you want to compress the researchers down very very small and put them inside the plasma itself.

Researchers are not involved in corner cases that might never happen. Nor are they worried about reliability yet (in the sense of preventing another Chernobyl, as opposed to the sense of very little downtime). They are just trying to get the blamed thing to produce enough energy to sustain itself, with some left over. (Although, if you're feeling pessimistic enough, you might call that a corner case that might never happen!)

I agree that we need to get a lot of funding to fusion research, but throwing money at the problem won't necessarily solve it. It is a very hard problem. Furthermore, we'd need not just one crazy (I presume you refer to the office of the President), but a whole bunch of crazies (half of Congress), because Congress makes the budget.

Re:If they used...

[joto]

We already can get ALL the energy we need from renewable sources

That might be so, but it certainly isn't economical, otherwise we would already have all our energy from renewable sources. Furthermore, very few renewable sources of energy shows any sign of promise in the short term, although solar certainly seems interesting once someone comes up with a "breakthrough". Oh, and we could build more dams, they can certainly be profitable, but often takes a huge toll on mother nature.

a bunch of overblown assholes who aren't remotely interested in finding a CHEAP energy source - they want a CENTRALISED energy source that a government can completely control.

Actually, centralized makes a lot of economic sense. There is only one way of generating power that is at least potentially profitable at a small scale, and that is solar cells. But even here, you get economic benefits by simply aggregating them in a small area, which simplifies maintenance and infrastructure. Nuclear just doesn't scale down at all, and everything else, is simply more efficient at a larger scale, whether it's wind-turbines, dams, wave-turbines, geothermal, waste energy from industry, burning of garbage or methane from a landfill, or even gas, diesel, or coal. If you don't believe me, try putting up a small propeller in your backyard, and compare the $/watt of this to a typical 100 meter wind turbine, or to a huge turbine farm with 100 meter turbines. Or compare the $/watt of a small waterwheel to the Hoover Dam. Or compare the efficiency of a diesel-generator you can afford, to one that you can only afford to rent, or to one that is able to power a whole city. These things might scale down, but certainly not in an economical way.

It's always "It'll be ready in 50 years' time". i.e. in 50 years' time, they'll STILL be saying "It'll be ready in 50 years' time".

This is certainly a valid criticism for fusion power research. But I hope you don't seriously believe that just because you can't have it today, we should stop researching it. The benefits of such a technology would be incredible, and the money we spend on it is not that much. Still, one can debate whether pouring money into tokamak research is justified given its track record so far, This, however, is not a tokamak, and as such is a potential theoretical breakthrough, even if it might be an unlikely one (I'm not qualified to judge that).

Re:If they used...

[tyrione]

What he's pointing out is that the Power Industry model driven by minimal players and large profits is crippling innovation and progress in countless other fields. Some fields should be an Investment to the rest of the Commercial/Consumer landscape.

Re:If they used...

[The_Wilschon]

Quenches of superconducting magnets are certainly problems. However, at least based on my experience at accelerator experiments, quenches usually do nothing more than vaporize a whole lot of liquid helium. Perhaps there are a couple orders of magnitude more energy stored in the magnetic fields for tokamaks than for HEP detector solenoids, but I'm a little bit skeptical that that is the case.

Stellarators aren't new

[Anonymous Coward]

The summary makes it sound like stellarators are something novel, which they are not. Research has been going on for decades, most notably with the German Wendelstein experimental reactors.

Re:Stellarators aren't new

[iamlucky13]

In fact, the stellarator design is almost as old as the Tokamak design. The first one was built in 1951.

Somebody over at physorg got a little too excited about a fairly low-impact paper from NYU. If you read the abstract, you'll see that the paper just deals with the design of the coils for a stellarator.

Most likely, this is for the National Compact Stellarator Experiment (NCSX) being built at nearby Princeton, which will be the first stellarator designed with a computer optimized plasma geometry. I think it will also be the largest stellarator to date, with 12 MW of heating capacity. In contrast, the JET Tokamak has 37 MW and the ITER Tokamak will have 110 MW of heating. Unlike ITER, NCSX will not be capable of break-even operation.

Stellarators often get mentioned in fusion power discussions because they provide a more stable containment design, whereas a Tokamak needs one extra set of electromagnets to deal with the fact that the magnetic field is weaker at the outside of a torus of magnets than at the inside. Although a stellarator is therefore a little simpler in that regard, the geometry and plasma modelling is much more complex, and this in turn creates problems for designing the coils and the exhaust diverter. Because of this, most of the funding and research effort has gone to the Tokamaks.

A little more info here: http://en.wikipedia.org/wiki/Stellarator

Anybody care to bet on whether this shows up on CNN's tech page in a day or two as some major "recent design enhancement?"

Re:Stellarators aren't new

[Shag]

Princeton? I'm sure you know (as do I - I grew up not far from there and a friend of the family worked at PPPL) that they already did quite a lot of experimentation with the Tokomak design, and held the world record for fusion back in the 90s. In fact, the Stellerator is sort of an optimized Tokomak; the overall shape of the plasma is still a torus (Mmmm, donuts!) but it's "twisted" so it's not the same cross-section in all spots.

I haven't read enough to really grasp why that's better, but 12MW is going to be a bit more powerful than the TFTR was.

Re:Stellarators aren't new

[owndao]

I see what you mean with the resemblance to a Tokamak. This reminds me of a harmonics-optimised nightmare out of my college magentic machinery course. BTW how do you feed one of these. Do we have pellets with lots of pulsed energy beam equipment as in inertial confinement? Just curious.

Re:Stellarators aren't new

[Talinom]

Although a stellarator is therefore a little simpler in that regard, the geometry and plasma modelling is much more complex, and this in turn creates problems for designing the coils and the exhaust diverter.

That's a relief. Now we know for certain that the exhaust ports are a weakness we can exploit when the government builds their Death Star.

input-output

[polar red]

Like other forms of containment this does require energy itself I find it weird that the amount of energy needed to contain, is less than the energy contained in the plasma. Can anyone explain this ?

Re:input-output

[Paul Pierce]

Like other forms of containment this does require energy itself I find it weird that the amount of energy needed to contain, is less than the energy contained in the plasma. Can anyone explain this ?
Picture Chinese handcuffs

Re:input-output

[feepness]

Picture Chinese handcuffs Great now I can't let go of that image.

Re:input-output

[thanatos_x]

It's intrinsically harder to do useful work that raw work, just like it's easier to destroy than create....

It could also be that it's a brute force attempt to force cohesion, and since force must be met with equal force it's very difficult. That also assumes it could concentrate the exact amount of energy at exactly the right point. Just imagine trying to not only stop a terrorist attack, but subdue them without lethal force. They need one leak to win. You need a perfect record.

Re:input-output

[iamlucky13]

Well, I'm not a plasma physicist, so I'm not intimately familiar with all the details, but one thing that jumps out at me right away is the distinction between energy and power.

Energy is the ability to do work. Power is the rate at which work is done or energy is extracted.

The plasma contains a great amount of thermal energy with a tendency to do work (by difussing to the reactor walls), so you have to set up a barrier to accomplishing that work. This is analogous to a dam holding back water. The water, due to it's elevation, has a lot of potential energy, but no power is required to hold it back. Power is extracted as it's let through the turbines.

It's a little more complicated for a plasma. A charged particle moving through a varying magnetic field (like that surrounding the reactor) does work and thereby loses energy. As a result, there is a tendency, although less definite than with a dam and water, for the hydrogen ions to only move around in the reactor along lines of constant magnetic field strength.

Once a magnetic field is established, it ideally takes no energy to maintain, except as charged particles move through it. So power only has to be supplied to the electromagnets to account for their inefficiency (0 under ideal conditions in a superconducting Tokamak) or as work is done on the field by charged particles escaping. Since most of the energy from the reactions is carried away by neutrons, which have no electric charge and therefore don't affect the field, the containment power is sufficiently smaller than the reaction power that this is theoretically feasible as a power plant.

Actually, the biggest power demand in a Tokamak as I understand is for heating the plasma to a temperature where fusion will take place. The hotter it gets, the faster fusion occurs, eventually reaching a breakeven point energy is released by fusion faster than it is carried away by escaping neutrons and gamma rays. Then the plasma can sustain itself. We haven't gotten there yet.

Sorry, the dam analogy isn't great and talking about charged particles in a magnetic field is a little abstract. Hope this helps.

Re:input-output

[counterfriction]

"Energy" in the context of containing a plasma is actually work. They have the same units, so they're like exchangeable currencies (i.e. some energy will buy you work, and some negative work will buy you energy)
The energy that a plasma intrinsically has (like kinetic energy) is just that; energy.

Here's a related (but certainly not airtight) analogy: A brick can have some gravitational potential energy relative to the earth's surface. If you're standing on the ground, that brick will have some nominal gravitational potential energy. If you lift that brick 1 meter, you'll do some amount of work. If you're hanging over the edge of a helicopter at a couple hundred meters, that brick has substantially higher gravitational potential energy. However, if you lift the brick a distance of 1 meter, you'll still do the same amount of work.

So, what's going on here is that a plasma can indeed have a lot of energy (relative to the earth's environment). However, the "energy" we're putting in is actually work to contain that plasma.

Re:input-output

[Anonymous Coward]

just like it's easier to destroy than create...

Actually, at a fundamental physical level, that's untrue. The only thing that costs energy is erasure of information.

Re:input-output

[mako1138]

Actually, the biggest power demand in a Tokamak as I understand is for heating the plasma to a temperature where fusion will take place. The hotter it gets, the faster fusion occurs, eventually reaching a breakeven point energy is released by fusion faster than it is carried away by escaping neutrons and gamma rays. Then the plasma can sustain itself. We haven't gotten there yet. Some subtleties:

Fusion reaction rates are proportional to temperature, but only up to a certain point. The trend is roughly parabolic.

'Breakeven' is usually calculated on the assumption that energy leaving the plasma is reinjected with a certain efficiency, typically 1/3. 'Ignition' is when the fusion reaction can go on without any external power input.

Also, I realize it's a rough analogy, but the dam picture is inadequate. My professor described fusion confinement as "trying to hold jell-o with string".

Re:input-output

[Gryle]

Surely Red China can't be that upset with GP asking questions.

Re:input-output

[kravlor]

There are two aspects to answer your question properly:

• In a fusion reaction, you are invoking a nuclear process. Think E=mc^2; the E is resulting from the change in mass following the fusion of hydrogen (or strictly, its isotopes deuterium and tritium) to helium and a neutron. It can also be thought as a change in effective binding energy per nucleon (proton/neutron) in the nucleus of the resulting atom. So, even though you've got lots of mechanical (thermal) energy in the plasma which is actually causing the fusion reactions to take place, after the nuclear reaction kicks in the energy "balance" rapidly gets skewed.
• The fusion reaction for the first generation of practical fusion reactors is going to be D-T; ie D + T --> 4He + n + ~18 MeV, of which 14 MeV goes to the neutron. Neutrons don't feel the confining effects of the magnetic field, as they're not electrically charged; they fly out of the plasma, strike the first wall surface, and rattle around in the shield until they give up their kinetic energy to heat. If the blanket's made correctly (ie with Lithium too) it will also breed more T fuel to boot. The remaining ~4 MeV in the helium "ash" goes back into sustaining the plasma heating.

And yes, I am a plasma physicist. :)

Huh...

[Greyfox]

SCO Loses and they figure out fusion* on the same day. Coincidence? I think NOT!

* Sure it doesn't say they figured it out in TFA but humanity will point to this day and say 'That is the day SCO lost and they figured out fusion.'

Re:Huh...

[ascendant]

Too much tinfoil in your hat interfering with the brainwaves?

to clarify

[spune]

It is the improved stellarator design that is new; stellarators have been around for decades.

Thorium reactors

[Bombula]

I was reading about thorium reactors recently. Seems like that's much closer to being rolled out, and its developers are claiming it solves a lot of the problems with existing reactors: it's more stable because thorium reactions don't chain the same way, it doesn't produce waste or plutonium, it can actually burn up other waste - including plutonium, and it can be used in some types of existing reactors (there are trials in Russian reactors right now).

Does anyone know any more about this?

Re:Thorium reactors

[meringuoid]

Thorium good, but if possible, fusion even better.

If you want to see thorium-fuelled fission reactors in operation, you'll probably want to go to India. They're sitting on about a quarter of the world's thorium supply, and quite reasonably think that they ought to get some use out of the stuff.

Re:Thorium reactors

[Bombula]

Thorium good, but if possible, fusion even better.

It's important to define 'better' here. Cost would seem to be an important consideration, for example. I don't know what the price tag of fusion is so far, but it's awfully, awfully high already and without a great deal to show for it. If we've already got a pretty good thing in thorium, and we already have the reactors, and there's enough thorium and uranium to keep us in electricity at present consumption rates for thousands of years, and it's non-polluting and all the rest, then how is fusion - a hugely expensive, so far unproductive technology - 'even better'. I'm not quibbling or trying to be antagonistic here - it's a serious question, and it needs a serious answer considering what's at stake: we need clean, non-polluting power that doesn't ultimately come from politically volatile parts of the world.

Re:Thorium reactors

[mdsolar]

You want to be careful with that stuff. There was a boy who built a breeder in his mother's shed in the ninties using thorium. He was arrested again at the beginning of this month for stealing smoke detectors. He does not look so healthy in his mugshot: http://freep.com/apps/pbcs.dll/article?AID=/200708 03/NEWS04/70803062. Sad story. There just isn't any such thing as clean fission. It makes a mess every time.
--
Get clean energy: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html

Re:Thorium reactors

[Hoi Polloi]

Yow, what happened to his face? I think he should be stealing chemotherapy drugs instead of smoke detectors. I guess once you've made one reactor you just can't quit.

Re:Thorium reactors

[mdsolar]

That seems to be our problem right now: http://mdsolar.blogspot.com/2007/08/cliffhanger.ht ml and http://mdsolar.blogspot.com/2007/07/new-mexicans-c onspire.html. That last one is meant partly in fun. The Sierra Club likes Bill Richardson's energy policy.

Re:Thorium reactors

[mdsolar]

Solar and wind power fit the bill of being clean and local. A lot of our nuclear fuel these days comes from Russian weapons stockpiles. But the process of diluting it back down from weapons grade to fuel grade is not going all that well. In an accident in Tennessee last year that was covered up until congress stepped in, the plant managers thought that a big spill of highly enriched uranium soulution, enough to cause the kind of accident that killed 2 people in Japan 1999, was natural uranium. There were two places where the spill might have accumulated and cause criticality. That is pretty poor materials control if you don't know what it is that you are working with.

Uranium reserves are estimated to be about 85 years at present use. Plans to extend the life of nuclear power all pretty much include breeder reactors (such as thorium reactors) and have unresolved fuel cycle problems. Fast breeder reactors are also illegal in the US owing to proliferation concerns. Their prototypes have also tended to melt down.

The new reactor being planned for Calvert Cliffs has an estimated price tag of $2.50/Watt for construction alone, though with federal loan guarranties included in the Senate Energy Bill, this price will likely rise substantially. The price compares poorly with wind and solar, both at about $1.30/watt to build, but with much less in the way of operating costs, and obviously no fuel or long term waste disposal costs.

The level of effort put into fusion has not really been that large. You hear about it, but compared to the Manhatten Project, out of which nuclear power came, it gets much less in the way of GDP. Renewables get even less than that. This was deliberate. The idea was to give it enough effort so that it would be ready when oil and coal ran out. The problem is that at the time, the growth in the use of coal and oil was not foreseen. So, fusion is actually right about on schedule. When it is here, there may be some trouble siting it since nuclear power plants squat on some of the better cooling resources and our storage in place policy for nuclear waste may keep these prime resources tied up for hundreds of years. But, wind was 20% of new generation in 2006 and is growing at 50% per year, while solar is growing at 30% per year and this should accelerate as the silicon purification bottleneck clears. So, fusion may enter a market that is already dominated by clean inexpensive power and thus find only niche applications in any case.
--
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Re:Thorium reactors

[quanticle]

The problem with thorium, as with all nuclear fission, is that eventually you'll still get waste that's unusable for energy production, but still emitting enough radiation to be dangerous. As the waste sits in this phase for quite a time (I've heard spans on the order of centuries) you have to find landfill locations that are stable enough to hold spent fuel for extremely long spans of time. Its the lack of space to store waste, rather than lack of fuel that's the limiting factor with nuclear fission.

With fusion, though, all outputs are stable; therefore waste isn't a concern.

Re:Thorium reactors

[barawn]

That's not exactly true. The ideal output of most fusion cycles is stable. You get side production of tritium and a few other radioactive isotopes, though.

But fusion does, however, produce a large amount of radioactive waste. Not through the products of the reaction. Through the byproducts of the high level of irradiation.

The difference is that fission radioactive byproducts are long lived. Fusion radioactive byproducts are extremely radioactive, but very short lived, and therefore easier to deal with

Re:Thorium reactors

[Your.Master]

Advantages of Fusion:

* Fuel for fusion can be extracted from water, including non-potable water. Fission requires Uranium & Thorium to be mined and transported, and your country might not have it. By the time the fuel runs out, our sun will be a red giant, so we should worry about escaping the solar system before doing any better than that.
* No weapons material generation (Thorium is in some respects similar here).
* Radioactive waste: there's a lot less of the stuff sticking around, and really no high-level waste at all. This can save a lot of money with disposal and some with safety equipment, not to mention avoiding the headaches of dealing with people who believe that radioactive waste should not be produced at any cost. Note that this is actually partly a problem, since many nuclear "waste" materials have important industrial and medical uses, so we will likely continue to run some of these fission reactors anyway (or perhaps figure out ways to produce these radioactive isotopes more directly).
* Although fission plants are perfectly safe, there are a lot of people who still fear them for a variety of reasons, mentioning any of which is likely to lead to a fruitless and flame filled side-discussion if anybody reads my post at all. Fusion power is inherently even safer, which might satisfy a few of these people.

Re:Thorium reactors

[rossifer]

Almost all of the waste from a molten salt Thorium fuel cycle reactor has a half life of 30 years or less (total storage of 300 years and it's as clean as the thorium ore it came from). Also, the mass/volume of the waste to be stored is substantially lower than a light water reactor because you can continuously mechanically and chemically extract the waste from the liquid fuel. With a solid fuel reactor, the waste is physically tied to 90% of the still-good U235 and the now damaged ceramic that makes up the rest of the pellet. You have to sequester all of that unfissioned U235 along with the pellet body which amounts to about 200x more waste to deal with.

Because the waste from a liquid fueled reactor can be continuously extracted in very small quantities, it's fairly easy to make uber-safe small containment vessels and constantly courier it to your long-term storage site. (a 1GW reactor would produce less than a half liter of waste product per day so you could make each container hold 100cc of the stabilized waste products and only need a modified armored vehicle to safely transport the five uber-bottles each day) With solid fuel reactors, you have large refueling events that generate multiple tons of waste per event. The quantity that must be managed at once makes it that much more dangerous to handle and transport safely.

Another nice thing about molten salt reactors is that they can be 97% fuel efficient. Unlike our current light water reactors which only burn about 10% of the fuel before the solid fuel is too contaminated with reaction poisoning fission products to keep an efficient reaction going any more. This efficiency is mostly due to on-site constant fuel reprocessing. There's an alternative molten salt reactor approach that doesn't involve reprocessing that is about 50% fuel efficient but gives you a lot of crappy waste every 20 years. I prefer frequent small quantities myself...

Possibly the nicest thing is that if you use a dual fuel configuration (a LiF/BiF2/UF4 kernel and a LiF/BiF2/ThF4 shielding/breeding layer) the core is thermally self-limiting. As the reactor heats up, the salt mixture expands and reduces the reaction rate until the whole thing stabilizes around 1500-1900C (the final temp depends on the exact fraction of UF4 in the mixture). You don't need control rods or any of the additional equipment to maintain moving parts in the reactor. All you need are pumps to cycle the kernel fluid and the primary cooling fluid and if those shut down, there's nothing to go wrong. The whole thing heats up and sits there radiating heat. If you want to put an automatic stop to the heat, put a thermal plug in the bottom that will melt if primary cooling ever stops and drain the whole core into subcritical storage containers underneath the core.

One big problem with the molten salt reactor is that the existing nuclear equipment industry makes most of it's money from fuel manufacturing. Molten salt reactors are constantly reforming the liquid fuel on-site, which means that the existing nuclear infrastructure has to change their business model (or be supplanted) before it can possibly work.

The other huge problem is that most of the advantages of the Thorium fuel cycle come from the fact that it's a breeding/reprocessing cycle. Both of which (fuel breeding and fuel reprocessing) are currently illegal in most first world countries due to nuclear proliferation concerns. Laws can be changed, but governments would have to be reassured about the risks. The thorium fuel cycle can be spiked with U232 which will prevent the creation of nuclear bombs (because U232 decays into a hard gamma emitter that destroys nearby electronics), but wouldn't prevent the construction of radiological "dirty" bombs (basically what Korea can build right now).

Ultimately, the big advantage of newer fission reactors over fusion reactors is that we can build the fission reactors today. Further, if we decide to breed fuel, there's enough known U238 and Th232 in the upper crust to prov

Re:Thorium reactors

[ttfkam]

http://www.cosmosmagazine.com/node/348

Some of the main benefits of thorium reactors are that they vastly reduce the amount of waste, emit waste that has much shorter half-lives, and (here's the kicker) can eliminate existing stockpiles of plutonium and spent fuel.

Fusion does nothing to address the issue of existing nuclear material.

It's not an either-or deal; it's a measured "both."

Re:Thorium reactors

[adrianmonk]

we need clean, non-polluting power that doesn't ultimately come from politically volatile parts of the world.

I don't know if that will ever happen. With most sources of energy, the fuel is unevenly spread around the globe. And being some small country that has a huge reserve of some kind of fuel will tend to mess your country up in the same way that people who inherit a lot of money (and never have to work a day in their lives) get messed up.

Trade doesn't always have to create political instability, but it certainly doesn't help when you have a country that controls some resource that society must have in order to keep functioning. If someone must have something, they're willing to take it. And conversely if you have something that someone else needs, you tend to behave however you damn well please.

Re:Thorium reactors

[mdsolar]

How cowardly to make such accusations, and how inaccurate: http://en.wikipedia.org/wiki/David_Hahn. Getting a complete collection of elements requires a breeder. Nice try.
--
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Re:Thorium reactors

[Adorack]

So much work has gone into researching fusion because its fuel source--hydrogen--can be extracted from water. At least right now, water's everywhere. Uranium and thorium and any of the heavy elements for fission still have to be pulled from the ground in pretty limited areas--if those areas become politically volatile, are we any better off than using oil?

Fission reactors are better right now than burning hydrocarbons. But fusion is still worth researching.

Re:Thorium reactors

[mdsolar]

Ever the coward. Come back when you can read. He built a reactor. If he was not successful in making it go the way he wanted it to, that is a different matter. Working with thorium is obviously dangerous as this case makes clear.

Re:Thorium reactors

[mdsolar]

Are you sure?

Now 17, David hit on the idea of building a model breeder reactor, a nuclear reactor that not only generates electricity, but also produces new fuel. His model would use the actual radioactive elements and produce real reactions. His blueprint was a schematic in one of his father's textbooks.

Ignoring safety, David mixed his radium and americium with beryllium and aluminum, all of which he wrapped in aluminum foil, forming a makeshift reactor core. He surrounded this radioactive ball with a blanket of small foil-wrapped cubes of thorium ash and uranium powder, tenuously held together with duct tape.

"It was radioactive as heck," David says, "far greater than at the time of assembly." Then he began to realize that he could be putting himself and others in danger.

When David's Geiger counter began picking up radiation five doors from his mom's house, he decided that he had "too much radioactive stuff in one place" and began to disassemble the reactor. He hid some of the material in his mother's house, left some in the shed, and packed most of the rest into the trunk of his Pontiac.

http://www.dangerouslaboratories.org/radscout.html

It is wise to avoid making false accusations, and doing so anonymously is extraordinarily lacking in honor. Your lack of expertise is so glaring that this is the only excuse I can find for you: you have no education.

Re:Thorium reactors

[trewornan]

It's far from clear exactly what Hahn built - various neutron guns certainly, but his final creation involving Americium, Thorium, Radium, Uranium and Aluminium and which was (apparently) giving off more and more radiation every day, could very well have met the dictionary definition of a "nuclear reactor".

And beside that; the dictionary definition of "nuclear reactor" is out of date and is based on the science of the Thirties. A neutron gun capable of creating nuclear reactions might very well be described as a "nuclear reactor" by a more reasonable definition. Words do change their meaning over time often by changes in usage but also by changes in context.

Re:Thorium reactors

[Planesdragon]

Its the lack of space to store waste, rather than lack of fuel that's the limiting factor with nuclear fission.

No, it isn't. Or at least, not as you describe it.

Any nuclear waste that is hot enough to be dangerous to hold in your hand can still be used as an energy source. It may be impractical, but, well, if there wasn't any energy, you wouldn't be in any danger.

And most of this "hot" nuclear waste has a far shorter half-life. Every time a subatomic particle of radiation is released from a fission-reactive object, at least two (often more) atoms have changed to a lower state. Some of those will continue to decay, others are stable.

BTW, it's entirely feasible to use most of our nuclear "waste" to create elecrical power. We don't, because one of the intermediary steps between "spent uranium" and "electrictiy" is the critical components of a nuclear bomb.

Oh, great!

[Sloppy]

I just bought a fusion reactor that uses the old design!

Re:Oh, great!

[magus_melchior]

"'Best before November 1959.' Damn it, Bob, there were plenty of brand-new bombs, but you had to go for that retro 50's charm."

I'm Sorry

[JamesRose]

But Some Rapscallion has slipped an extra cyllable into the name of your system!

Stellarator? Its somehow wrong

Stellarators have been around as an idea for years

[Zarhan]

...and as prototypes too.

http://en.wikipedia.org/wiki/Stellarator

Anyway, basically what I know about this is that stellarator designs avoids lots of the problems that are present in Tokamak - namely, degrading of the reaction chamber due to escaped neutrons. A fusion reactor using stellarator instead of Tokamak would, in effect, last forever since the material does not become radioactive.

Especially the Germans have been researching this stuff a lot, however, most of the big money is currently in Tokamak designs, including ITER. Which is kinda a shame - since we're not in the Manhattan Project-type "if you have 3 designs and think one of them might work, build all three, here's the money"-situation..so these nice ideas may only be developed further if Tokamak fails to become viable..

Doh!

[the eric conspiracy]

A stellarator is not a new design. The first examples were built here in 1951.

Re:Doh!

[pontifier]

Seriously, who's never heard of a stellarator before? Certainly anyone who's truly interested in fusion power has read about them.

Re:Stellarators have been around as an idea for ye

[Grishnakh]

According to the comments at the end of the physorg article, that's not true.

Also according to those comments, the idea of fusing atoms is completely unproven.

I think I'm just going to give up on humanity.

Why reinvent the wheel?

[viking80]

Design parameters for fusion reactor:
1. Contain a plasma ball with high density for fusion reaction. Ball is much better than doughnut if you just can figure out a way to keep the plasma together.
2. Make a wall that is far enough away to not melt from this plasma ball to absorb heat/radiation to make power, and keep it close enough to get high enough energy density on its face.
3. Make the wall 1 ton/m^2 to protect the people outside
4. Use magnetic field outside plasma ball to contain radiation.

This seems like a tall order, and it is, but consider the sun/earth:
1. Gravity works great compared to magnetism.
2. Well, here on the earth, it is 1kW/m^2. That is much higher than the energy consumption in most cities. Should be good.
3. Our atmosphere stupid.
4. The earth again has a great magnetic field that protects us pretty well.

Bottom line: Why reinvent the wheel?

Re:Why reinvent the wheel?

[OeLeWaPpErKe]

4. Use magnetic field outside plasma ball to contain radiation

This seems like the exact reason why basic physics should be mandatory in schools. Dear God. How exactly would a magnetic field contain neutral photons ? They will generate zero flux and will not interact with the field at all.

Re:Why reinvent the wheel?

[Wonko the Sane]

3. Make the wall 1 ton/m^2 to protect the people outside

Houston, we have a unit problem

Re:Why reinvent the wheel?

[Jherek Carnelian]

This seems like the exact reason why basic physics should be mandatory in schools. Dear God. How exactly would a magnetic field contain neutral photons ? They will generate zero flux and will not interact with the field at all. Clearly adding a flux capacitor to the magnetic field generator is necessary to add flux to the contained photons.

Re:Why reinvent the wheel?

[lawpoop]

This seems like the exact reason why basic physics should be mandatory in schools. Okay...

Dear God. How exactly would a magnetic field contain neutral photons ? They will generate zero flux and will not interact with the field at all. Is this the kind of basic physics that the average student would understand in their mandatory class?

Re:Why reinvent the wheel?

[LinuxEagle]

Errm, point me to a working fusion generator. (other then then stars and the like)... I don't think we have yet invented the wheel in this case.

Re:Why reinvent the wheel?

[Aqua OS X]

I took physics in high school and I still have no idea what you're talking about.

Re:Why reinvent the wheel?

[qbwiz]

Not all radiation is made of photons. Specifically, alpha rays are made of helium nuclei (and are therefore positive) and beta rays are made of electrons (and are therefore negative).

Re:Why reinvent the wheel?

[mdsolar]

Radiation is not just photons. There is a good point here. While there are very few nuclear reactions going on on the surface of the Sun, mainly spalations from accelerated protons, there are accelerated protons from the corona (the same) that impinge on the Earth's magnetosphere and are deflected. It is the Sun's magnetic field, rather than escaping fusion products, that are responsible for the high energy particle flux.

There are also possible photon-magnetic field interactions though with a low coupling: http://www.sciam.com/article.cfm?chanID=&articleID =0006BA85-FC58-1492-BAAC83414B7F0000.
--
Get fusion on your roof:http://mdsolar.blogspot.com/2007/01/slashdot- users-selling-solar.html

Re:Why reinvent the wheel?

[mako1138]

We're not reinventing the wheel. The sun's fusion reactions are very different from the ones envisioned for terrestrial fusion reactors.

The sun starts by fusing hydrogen. (http://www.tim-thompson.com/fusion.html)
This first step happens on a huge timescale:

p + p --> d + e+ + nu 7.9 x 10^9 years

This only works out in the sun because it's a frickin huge ball of gas.

Terrestrial reactors will use DT fusion. The time it takes for this reaction to happen is not worth talking about.

And regarding the "plasma ball with high density", consider that the typical DT fusion plasma has a density of 10^20 /m^3, which is one millionth the density of air.

In short, we can do fusion better than nature can. In 50 years (TM), that is.

Re:Why reinvent the wheel?

[hairykrishna]

Honestly, how is this insightful?

Your answer is "we should use the sun". Well done. Got any better methods than what we're using currently?

Re:Why reinvent the wheel?

[hab136]

Dear God. How exactly would a magnetic field contain neutral photons ? They will generate zero flux and will not interact with the field at all.

Is this the kind of basic physics that the average student would understand in their mandatory class?

The fact that protons are positive, electrons are negative, and neutrons are.. you know.. neutral and therefore not affected by magnetic fields.. yes, I learned that in about 6th grade.

Re:Why reinvent the wheel?

[Creepy Crawler]

If we're dealing with fusion, what are the effects of mass amounts of neutrinos going through living tissue?

You know, 1/d^2 is sort of a problem when you are d close to me. (When d is is 1/500 AU).

And yes, I do know about the super-pure H2O and Cl- deep-mine tanks that monitor for neutrinos.

Re:Why reinvent the wheel?

[rossifer]

Actually, you'd be correct if you were to say that neutrons are not affected by electric fields. But neutrons are fermions with magnetic spin and are affected by (and can be moved around with) magnetic fields, so...

Regards,
Ross

Re:Why reinvent the wheel?

[rossifer]

Terrestrial reactors will use DT fusion. The time it takes for this reaction to happen is not worth talking about.

Actually, He3-He3 fusion (the last few steps in solar fusion) is substantially safer than DT fusion due to the minimal neutron flux. See wikipedia for more information (it's the last reaction in the proton cycle where 2 He3 -> He4 + 2 H- + 12.86MeV). Not quite as much energy as D + T -> He4 + N + 17.6MeV, but still a respectable amount of energy and much less neutron damage to the reactor walls over the lifetime of the reactor.

All we need to make it work are faster ways to obtain He3 than are used by the sun. Luckily, we know of a few ways to get He3. Since Tritium will beta decay into He3 with a half-life of 12 years, all we need is enough tritium and we'll have a steady supply of He3. Tritium appears from three relatively simple nuclear reactions:

1) N + D -> T + gamma
2) N + Li6 -> He + T + gamma
3) N + Li7 -> He + T + N + gamma

Given those equations, lithium deuteride becomes an extremely interesting substance. It's a salt where every atom in the salt will form a tritium atom when it absorbs a neutron. Wrap a big mass of lithium deuteride around a neutron source and you're breeding tritium faster than you can produce neutrons (since some of the conversions will re-emit another neutron and cascade into another tritium conversion). Store the produced tritium for a decade and you'll have converted 40% of the tritium into He3. A MUCH faster process than the sun uses.

There's also the possibility that there is economically available He3 in the lunar crust or in the upper atmosphere of gas giants, assuming we decide to develop the space-based industry to go after it.

Going and finding extra-terrestrial He3 sounds farther out than making it locally.

Regards,
Ross

Re:Why reinvent the wheel?

[mako1138]

He3+He3 fusion on Earth, seriously? I don't think that's a realistic fuel; the reaction cross-section is extremely small, even at solar temperatures. Nobody talks about doing He3+He3 fusion. Are you perhaps thinking about D+He3 fusion?

D+He3 fusion (and other aneutronic fusion, like p+B11) certainly is nice, but we're not going to get there anytime soon. Why? These fuels don't "burn" easily; the cross-sections for aneutronic fuels are lower than DT's, and peak at substantially higher temperatures. I suspect we won't be able to do aneutronic fusion until we master DT fusion.

See the Fusion FAQ, question H.
http://www.faqs.org/faqs/fusion-faq/section1-physi cs/

Regarding your scheme for producing He3, DT fusion reactor designs envision a "lithium blanket" where tritium will be bred by the neutron flux. Perhaps someday DT reactors will supply the fuel for D+He3 ones.

Re:Why reinvent the wheel?

[torako]

That would probably be a bit too complicated for 6th grade. And considering that the original poster was talking about containment, I doubt that the small magnetic moment of the neutron would help in containing them using a magnetic field. dE/dx in matter is the only realistic way to shield off neutrons, as far as I know.

Magnetically confined plasma fusion reactors

[the_kanzure]

Related links: * LDX@MIT
* Physics of magnetically confined fusion [pdf]
* The main principles of magnetic fusion
* Magnetic fusion experiments at LANL
* High density magnetic fusion
* Has a good bit on magnetic confinement
* Can a magnetic field be used to contain plasma?
* International Thermonuclear Experimental Reactor
* What's happening in fusion?
* Design of magnetic fields for fusion experiments [pdf]
* Wikipedia article on the topic
* Magnetized target fusion bibliography
* Plasma physics bibliography
* Databases for plasma physics

* Plasma physics laboratories
* List of plasma physicists
* Plasma on the internet

Re:Magnetically confined plasma fusion reactors

[SchizoDuckie]

I would suggest strapping on a couple of octopus clamps to your back and controlling it by hand!
At least, that's how dr. octopus did it in spiderman :P

somewhere over the rainbow

[nuzak]

"The holy grail of fusion reactors has always seemed 'just a few years off' for many decades. But a recent design enhancement termed a 'Stellarator' may change all that.

Practical uses of Stellarator technology are projected, of course, to be "just a few years off".

Re:somewhere over the rainbow

[Anonymous Coward]

To start off, I am a plasma physicist. I have never seen any estimates coming from the plasma physics world claiming that a commercial stellarator reactor is less than 50 years off. I don't know where this "a couple of years away" keeps coming from. That isn't to say that early estimates of the difficulty of building a fusion reactor weren't wildly off. I just think that current estimates, while somewhat optimistic, are informed by a lot more science than those early estimates. We've learned a lot in the past 50 years.

Even commercial tokamaks, which have quite a head start over the stellarator, are projected to be pretty far off. If ITER's construction and initial operation is wildly successful, it won't be fully operational for 20 years, and it is expected that there will be one or two more iterations (depending on who you ask) before the first commercial tokomak is designed.

Another confounding factor in correctly estimating a date for commercial fusion power is that the funding for such projects has been somewhat irregular, and any estimate of how long it will take to develop such a reactor is, in effect, also an estimate of how much various governments will be willing to spend on that research.

The long and the short of it is that I think this characterization of fusion researchers as grossly over-promising is unfair, and untrue. Making estimates of any technologically difficult project is hard.

Re:Stellarators have been around as an idea for ye

[FleaPlus]

Right. The slashdot summary is faulty: What's new isn't the stellerator design itself, but a new coil configuration for a stellerator. The new configuration "generating an external magnetic field designed to prevent the plasma from deteriorating", although I'm not familiar enough with stellerators to know how much of a problem this was in previous designs.

Here ya go

[rrohbeck]

For Houston...

http://www.google.com/search?hl=en&q=1+ton%2Fm%5E2 +in+lbs%2Fin%5E2&btnG=Search ;)

Re:Here ya go

[westleyd]

Wait, a tic... 1 ton/m^2 =~ 1.3 lbs/in^2 --> So, you could dispurse a ton of sand over a 1 m^2 sheet of paper and it would just sit there happily? (considering the paper was adequately held at the sides OR not considering horizontal pull, and assuming a moderate 24 lbs/in^2 weight capacity sheet of paper) Hmm. sort of like a bed of nails concept.

Mmhmm

[tttonyyy]

Quasineutrality? Quasi-likely-to-work-in-the-real-world more like. :P

But Stella Kowalski Is The Old Style Stella

[NeverVotedBush]

STELLLAAAAAA!!!!!

"Stellarator"

[flickwipe]

Refrigerator full of Stella?

Re:"Stellarator"

[SpeedyGonz]

Refrigerator full of Stella?

Creepy...
You sure you're not that guy that chopped his wife to pieces and left the remains in a duct-tape sealed fridge?
I know, I know, I read too much "Reuters: Oddly Enough"

Re:"Stellarator"

[pipingguy]

Stelllaaaaaa!

Nice News for Nerds but...

[swokm]

If society won't even accept safe fission designs, what makes you think we will ever get far more powerful fusion reactors built? I think the largest problem now is the culture of misinformation and fear, not the problem of technology.

Unless I'm wrong, the production of non-military nuclear reactor designs in the US for the last 30 years have been... zero. Unless you count the Galileo, Ulysses, and Cassini space probes. Call me when we upgrade all of our reactors from 1973 designs to a much safer and cleaner Gen IV design -- like this bad boy (now with free hydrogen!) instead of taking high-level radioactives --potential fuel-- driving them recklessly around the country in truck, and shoving it into a salt mine, or some similar brilliant idea.

Besides, though I lust for the sheer coolness of magnetically confined plasma as much as any proper geek, the the simple fact is we have had the technology to use fusion for power for quite some time now(press release from 1998, although building the X-1 was promptly cancelled without reason) with Z-pinch inertial confinement on the insanely cool Z machine at Sandia.

Yawn. Wake me went the politics of our time aren't ruled by Luddites with pitchforks and torches...

Re:Nice News for Nerds but...

[mdsolar]

Gen IV does not finish design for 25 years. The new reactor that is moving forward the fastest is Calvert Cliffs 3, a run-of-the-mill light water reactor. I suspect this one will have trouble. While the nuclear power industry is talking about global warming all the time now, they seem pretty foolish to be betting on a sea level reactor as their first new project since the Three Mile Island and Chernobyl disasters made clear what a problem nuclear power is. The rise in sea level is 5 cm every 15 years and the rate is doubling every 15 years, so from its current level http://www.realclimate.org/images/sealevel_2.jpg, in 45 years you get 35 cm of sea level rise, enough to make the foundations pretty soggy. That would be about halfway through the life of the plant. 90 years out you get more than 3 meters with a doubling projection. That makes a very difficult mess to clean up. Think New Orleans Lower Ninth Ward. There is more to read about this problem here: http://mdsolar.blogspot.com/2007/08/cliffhanger.ht ml, including a link to a study on proposed sea level reactors in the UK.

Re:Nice News for Nerds but...

[NeverVotedBush]

Fusion reactors produce a whole lot less radioactive material as they run. Fission reactors make lots and lots of really hot stuff. Also, as people should take away from the article, fusion is really hard to keep going. If things get out of hand, it will just go out. No melted cores. No burning reactors dumping tons of highly radioactive material into the atmosphere and into the surrounding environment. And the whole process of refining reactor fuel does not create mega-tons of radioactive mine tailings, tons and tons of radioactive waste, and it doesn't have to be guarded because you cannot make a bomb out it (unless you already have a fission bomb to set it off).

Fusion reactors will be many many times safer than fission reactors. Hands down. I know the American public won't appreciate the above points, but if enough people explain this stuff to them, they might gradually get the upshot - fusion reactors are pretty damn safe.

Re:Nice News for Nerds but...

[swokm]

In a way, I think you restate my point, IMHO. You probably say it in a better way...

I'm not a nuclear engineer but the only info I find on Calvert Cliffs 3 is that it is still based on pre-1975 designs. That is not smart. I know Gen IV is not immediately available, but there is NO reason that we cannot start building reactors with passive fail safe technology that has been running in test IFRs for decatdes. There is a reason everyone is moving away from light-water designs.

Why would people build in a swamp or low shoreline? No idea, I agree it sounds stupid. Although, why not run the reactor as smaller 30 year sealed design units if this HAS to be the scenario? Those, too, have existed for years. Just pull them up, service, reseal every 30 years. Nothing is simple about nuclear power, but it is not like we are not using it (or going to use it in the future). I think we should be smarter about it and use the work of the engineers from the past several decades to make better, more informed decisions -- as in site planning as you so rightly point out.

The only thing I really disagree with is:

Chernobyl disasters made clear what a problem nuclear power is No. Chernobyl and 3Mile made clear what a problem poor design, and refusal to improve upon that design means. That is exactly where we are now, and it is why I am concerned. By sticking our heads in the sand, we are assuring that we will have a problem sooner, rather than later. Additionally, if a similarly carelessly designed and operated fusion reactor was near... say Chicago and things got out of hand there would be far more casualties, even including the lingering radioactive problems of the Ukraine.

We aren't shutting down all the nuclear reactors in the US. Period. Ain't going to happen. So why on earth aren't we doing everything we can to make them safe, or failing that rebuild them with new safer technologies ASAP? Self destructive politics. I do not think fusion will ever be a panacea for this problem.

Re:Nice News for Nerds but...

[swokm]

Actually, I think that the majority of Americans will agree with you that fusion is probably safer than fission. Especially with a good ad campaign, like they had for fission in the 1950s.

But my point is, seriously how long do you think it will take to replace all American fission and coal reactors with fusion reactors? 10 years? 20? 50? I guess 100. But nobody knows, because we don't even HAVE a single fusion reactor. Meanwhile, we refuse to upgrade our old crappy 1970 design water reactors. We sure as hell won't tear them down and rebuild a new generation instead.

Also, as people should take away from the article, fusion is really hard to keep going. If things get out of hand, it will just go out. No melted cores. We don't know that. I think you will probably end up being right, but there aren't any fusion reactors, so how do we know it will "just go out"?

We DO know that fission reactor designs with so called "passive safety features" do just go out because we have tested them decades ago. But will we update any of our designs? No. Did we share our technology with the Russians and help them update (or at least make more manageable) their terribly designed reactors? No. So Chernobyl happens. Easily preventable, yet look at all those that suffered. It is all well and good to say "radiation is bad" but that does not instantly replace all those reactors. We can't even shut them down without replacements because we need the electricity.

And the whole process of refining reactor fuel does not create mega-tons of radioactive mine tailings, tons and tons of radioactive waste, and it doesn't have to be guarded because you cannot make a bomb out it I understand you here, and used to think the same way a looong time ago. But things change. We don't even need to mine fuel for a quite a while with new reactor designs. Where is plutonium safer? All of it being burned up in a passive safe reactor for energy? Or in hundreds of thousands of nuclear warheads spread all over the world? In reality, fission reactors ARE THE ONLY WAY TO GET RID OF REFINED PLUTONIUM. That is very important. Why should we not render it safe and get energy at the same time? With new refining techniques and reactors, uranium and weapons grade plutonium go into the reactor. Only LOW-LEVEL radioactive waste comes out. It can't be used for fission (it is "used up") or even effective "dirty" bombs. This is a huge leap forward. Additionally, the refining is ONLY done inside the reactor. So the really dangerous stuff that is all around us on the open market goes in, relatively safe stuff (far, far less of it because most of the fuel is re-refined and used as fuel again -- if it is still hot, it stays in to make electricity!). This is also FAR less dangerous than the by products of all of these coal reactors spread around the world. They don't even try to contain ANY of their pollutants (where as these new fission reactors retain and properly deal with them all) they just spit them out for someone else to deal with. These pollutants ironically include naturally occurring radioactive materials in coal that WILL harm you if you suck them into your lungs. Thanks for putting that in the air, power industry.

I do take exception to one small detail though. Current uranium mining does not "create" radioactive mine tailings any more than it "creates" uranium. There is no reason that the tailings do not go right back where they came from in todays world, other than lack of enforcement by the EPA. It is no more dangerous than it was before.

I know this probably reads like I'm a fan-boy for fission; I guess maybe I am. But so very many otherwise intelligent people just hear the word "fission" and stick their fingers in their ears: "lalalalalalala... caan't hear you... no I don't use nuclear power...lalala"

Well, sorry, if you are American, you do. All of the information about IFR, new research, etc. was gone from the internet not too long ago. Thankfully, there seems to be some resurgence of at least intellectual curiosity about it. But we should at least have an open mind, and treat this rationally, not emotionally.

Re:Nice News for Nerds but...

[dakameleon]

We don't know that. I think you will probably end up being right, but there aren't any fusion reactors, so how do we know it will "just go out"?

TFA aside, even the summary mentions that's the problem they are facing at the moment - keeping the reaction contained & thus going, rather than fizzling out.

Re:Nice News for Nerds but...

[swokm]

I can appreciate what you are saying, but ignition will be a problem, until it isn't. If you know what I mean.

It can actually be kind of hard to light diesel fuel on fire with a lighter. But once it goes... So what I am saying is that its very definition, when we have a self-sustaining fusion reactor it is not "just going out" by itself, any more than all working nuclear fission reactor designs "just go out" (some do go out when you pull the plug, some melt down when you pull the plug). But whatever, we won't know until the designs are finalized and built --in like, 25 years. Maybe the method of magnetic containment will be radically different. Maybe NIF will win out and we'll be using lasers... who knows what 'race' conditions different designs that actually work may be prone to.

But they'd better dang well have passive safety features. You think we've learned our lessons by now.

Re:Nice News for Nerds but...

[mdsolar]

I see a difference in intinsic safety between fission and fusion. Both are basically limited by the capacity of the environment to carry away excess heat so that even though the energy release from fusion is much higher than for fission, we won't be building fusion reactors that are more powerful that fission reactors. Thus, working at the same scale we have, for fission, a chain reaction that is controlled by working right on the edge of runaway or, for fusion, an induced reaction working where a faster reaction rate takes more energy. Becaue of this difference, you don't get the potential for a huge spike in energy release with fusion that you have with fission and so containment only has to handle the energy release the plant is designed to produce anyway rather than a much higher energy release. This makes fusion intrinsically safe and fission intrinsically dangerous. More and more safety mechanisims for fission can help. Going to smaller reactor designs can help. Nuclear propulsion, for example, is less of a concern than commercial nuclear power.

Another big difference is that there is no need for very long term storage of the waste from fusion. But, waste aside, the big safety problem with commercial scale fission is greed. Scaling reactors back to managable energies on the safety side loses ecomonies-of-scale than make nuclear power competitive with coal. Putting short term profit ahead of public safety is encouraged by relieving the industry of liability for accidents. So, our nuclear safety problems are structural and it is not clear that a further elaboration of defence-in-depth can fully compensate for these flaws. Fisson power is a little funny in that on the better-cheaper-faster triangle you only get to choose one. With fusion we are on the better-cheaper side right now.

Re:Stellarators have been around as an idea for ye

[DerekLyons]

Anyway, basically what I know about this is that stellarator designs avoids lots of the problems that are present in Tokamak - namely, degrading of the reaction chamber due to escaped neutrons.

So, where in the stellerator design does the unobtanium shielding goes that stops the neutrons?
 
This is a serious question. If you have [hot] fusion you have neutrons, and they have to go somewhere. Magnetic fields won't stop them.

Please read post before commenting

[viking80]

4. Use magnetic field outside plasma ball to contain radiation

This seems like the exact reason why basic physics should be mandatory in schools. Dear God. How exactly would a magnetic field contain neutral photons ? They will generate zero flux and will not interact with the field at all.

Please reread parent post. Note: 1 ton/m^2 of mostly Nitrogen *and* magnetic field to protect people.
Life on earth has pretty much evolved around surviving radiation not caught by this protection. The physics is sound. 1. Atmosphere is opaque to photons with ionizing energy. 2. Neutrons are slowed down very well. 3. Charged particles are caught by magnetic field

Seems like you are flat wrong in many ways

[tryingagain]

1. The article includes atmosphere and magnetic field as a shield. 2. Photons interact with magnetic field in many ways. -a magnetic field is just photons, and if you play with magnets, you know how these photons interacts. -both have mass, and interact gravitationally -the upper atmosphere is a plasma. There is a interaction between photons and plasma(phase/group velocity, as well as plasma and magnetic fields.

Re:Seems like you are flat wrong in many ways

[ConceptJunkie]

Photons have mass? That's news to me. I need to go back to school.

Re:Seems like you are flat wrong in many ways

[viking80]

Photons have 0 "rest" mass, but remember:
E=mc^2 and for a photon, E=hc/l, 'l' is wavelenght and h is planck's constant, so
photon mass, m=h/(lc)

Re:Seems like you are flat wrong in many ways

[rossifer]

Photons have momentum, which is transferable (solar sails, etc.).

Also, a photon's energy can be converted into mass via e=mc^2 (high energy gamma rays can spontaneously form stable particle/antiparticle pairs with actual mass). That possible "mass of conversion" can be expressed as the potential mass or equivalent mass of a photon.

Regards,
Ross

Re:Seems like you are flat wrong in many ways

[reezle]

Even an easier way to remember that photons have mass:
-Gravitational_Lensing-
(Astronomers are using it all the time these days)

Re:Seems like you are flat wrong in many ways

[ConceptJunkie]

My understanding is that photons, having no mass, follow (if I'm using the term correctly, IANAP) a null geodesic through space, which when passing by a gravitational source is not a Euclidean straight line because of general relativity, causing the lensing effect. The photons are not affected by gravity but rather they follow a straight line in space that is curved around the object.

That's my understanding, but if that is shown to be incorrect, I'll be the first to admit I don't know what I'm talking about.

Magnetic fields do no work

[supergumby]

While a varying magnetic field can do work on a charged particle, magnetic confinement fusion systems use static magnetic fields. A static magnetic field does not do work on a charged particle.

Also, the particles move to the position of lowest potential energy, not necessarily along lines of constant field strength.

Good summary otherwise.

Re:Magnetic fields do no work

[kravlor]

For the most part it is true that static fields are employed. Indeed, this is the goal of the stellarator, where we get the field configuration perfect through exquisite design and manufacturing! In tokamaks, anyway, control of plasma shape, position, and stabilization of vertical instability are all done with slight perturbations to the applied magnetic field. On all modern tokamaks, they do in fact vary -- just very slightly.

You also have attempts to impose magnetic field variations due to the existence of a 'resistive wall mode' to which the typically spinning plasma can 'mode lock,' effectively applying the brakes to the plasma and causing disruption; the perturbations would make the resistive wall look like an infinitely conducting wall. (This has been done!)

Question for physicists who work on plasma

[zymano]

Why not just a sphere ????

Re:Question for physicists who work on plasma

[DancesWithBlowTorch]

Because it's horribly complicated to create a spherical magnetic field to contain Plasma in it. You probably had Maxwell's equations in college? The divergence of the magnetic field is zero, thus magnetic field lines always have to be closed. It's topologically really hard to build a spherical field out of that.

Re:Question for physicists who work on plasma

[kravlor]

Short answer: because it's been proven to be physically impossible in any topology which can be mapped to a shpere since the 50's, at least if you're confining with magnetic fields. It has to do with their structure.

That's why all devices are topologically similar to that of a donut, be it like an inner-tube shape (tokamak), cored apple (spherical tokamak), or funny twisted kinky looking (stellarator).

The main difference between the tokamak and stellarator is where to supply the confining magnetic field. You need two components: toroidal (around the donut the long way) and poloidal (the short way); tokamaks provide toroidal field and a weak poloidal field, but pass current through the plasma to self-generate the rest. Stellarators have horrendously complex coil structure to have, in principle, all the field structure worked out; you just switch it on, and don't have to pass currents through the plasma to contain it. (The motivation is that plasma current can drive instabilities. Stellarators are also intrinsically steady-state devices.)

Because tokamaks are much easier to build, they have done better historically; given the newfound computational tools today, stellarators are still playing catch-up. Specifically, plasma confinement still stinks, but hey -- they're making up for lost time at a great pace. Although I'm more of a tokamak enthusiast, I look forward to seeing what WS-AX in Germany and NCSX in PPPL can do in the next few years!

And yes, I am a plasma physicist.

Re:Question for physicists who work on plasma

[zymano]

thanks.

Re:Question for physicists who work on plasma

[Liquid Len]

Because you can't comb a sphere... In other words, because Maxwell's equations require any magnetic field to have zero divergence, which is not possible on a sphere.

Re:Question for physicists who work on plasma

[zymano]

Would mod up if i had mod points. Thanks for the explanation!

Re:Ummm... yes?

[Tmack]

We covered that at the high school level (neutrons = no charge). What did your physics class cover?

And neutrons != photons....Though it wasnt until college Emag (Phys5 or 6 I think) that I learned all the math behind the em wave functions (yes, light IS an electro-MAGNETIC field/wave) that make all this stuff happen.

tm

Re:Stellarators have been around as an idea for ye

[sanman2]

NEUTRons may be NEUTRal in terms of ELECTRIC CHARGE, but as fermions they do have magnetic spin, which means they are NOT IMMUNE to the effects of a magnetic field.

Drop the illusions...

[woolio]

Doesn't the Z machine require vast amounts of electricity just to "fire" once? They only fire it once or twice a day at MOST and it fires for only billionths of a second. It's not a continually running thing. It also produces a shockwave something like a mini-earthquake when it fires.

Also look at this link: http://www.sandia.gov/media/z290.htm

"Stockpile stewardship" is not about solving our energy problems... Well, at least not peacefully... It's all about ensuring that the aging nukes will perform as expected on demand. A large part of Sandia is dedicated to this mission.

I believe all sorts of radiation is released when they vaporize things in the Z machine... THAT's why its useful for stockpile stewardship.

At one time, I was stupid enough to think that The Department of Energy was concerned with producing/supplying energy for the nation. Despite appearances, they seem more concerned with finding new ways of quickly releasing energy upon other nations.

Re:Drop the illusions...

[swokm]

Doesn't the Z machine require vast amounts of electricity just to "fire" once? They only fire it once or twice a day at MOST and it fires for only billionths of a second. It's not a continually running thing. It also produces a shockwave something like a mini-earthquake when it fires. Yes. Perhaps you missed it, but that is why I posted the link to wikipedia for Pulsed Power. This means a power cycle, much like the combustion engine in your car, where there is compression, explosion, and expansion. It is this process that eventually translates into power, by turning your car axle. This process is a little different on a large scale, but basically the same. It doesn't really matter it takes a while to charge up the capacitors for the initial fire. The only question is: 'do we capture much more power from the compression/fusion that we put into the charge?' In this case the answer is a resounding YES! We are all fortunate. I understand that you can hear it fire, again like your car engine. Is this a problem? FWIW, steam turbine generators are VERY loud, although more constant.

"Stockpile stewardship" is not about solving our energy problems... Well, at least not peacefully... It's all about ensuring that the aging nukes will perform as expected on demand. A large part of Sandia is dedicated to this mission. Yes... I'm not sure I follow you here. It sounds like you are saying that because Sandia was originally commissioned to do testing so that the US would not have to explode live nuclear bombs on the earth's surface to see how radiation effects aging nuclear warheads, that they then are NOT allow to take use of discoveries that could use fusion to safely and peaceably generate power. Right here, right now. Sadly, this is a misunderstanding that the US government also shared, thereby canceling the new X-1 fusion power test reactor without any reason. This is a very strange and arbitrary viewpoint. Incidentally, this benefitted the existing petroleum industry that was lobbying against this reactor. I think we see how that has turned out, but I'll leave it to you to decide how much "tinfoil" is in that line of reasoning.

I believe all sorts of radiation is released when they vaporize things in the Z machine... THAT's why its useful for stockpile stewardship. Yes... again I am confused. The only way we traditionally generate power on a large scale is harnessing SOME type of radiation, right? "Radiation" is neither BAD nor GOOD. It is like metal. It is all around us, and can be used for good or bad. It can even poison us, just like heavy metals. But really, "radiation" is just another word for power. I don't know about "all sorts" of radiation for the Z machine, but its primary purpose is to generate X-Rays, like the doctors office. Only at a much, much higher temperature. This radiation does not travel outside the building, nor is it "contagious". You don't want to sunbathe in 3 million degrees C, however.

At one time, I was stupid enough to think that The Department of Energy was concerned with producing/supplying energy for the nation. Despite appearances, they seem more concerned with finding new ways of quickly releasing energy upon other nations. Hurray! We agree completely (see tinfoil above). This is in part why we don't want ANYBODY to build, or re-build, old dangerous FISSION reactors. If the US requires the rest of the world to only use FUSION, and we are the only country that makes FUSION reactors... well, there we are. Incidentally, if fusion ever does become practical in the US, I think all those pushing for coal, oil, and gas will suddenly sing a different tune, and wag their fingers at China, Africa, etc. "But here," they say, "I have just the thing to sell you to help you out..."

Ah, my fellow Americans... always anxious to corner the market (before there is even a market).

From the chasing your own tail dept.

[Lord Balto]

For the $1,000,000,000,000 Monkey Boy will spend in Iraq we could have put solar collectors on every home in America for free. So they finally figure out how to make fusion work. Energy will still be monopolized by the power companies and you'll still be paying through the nose. And if you try to do anything about it they'll call you an enemy combatant and send you to Guantanamo. There is no technological fix. There is only a political fix.

Re:From the chasing your own tail dept.

[westleyd]

Teehee! look at the monkey :)

Re:From the chasing your own tail dept.

[Thundersnatch]

Solar cells will only offset a small portion of our (mostly coal-based) electricity generation. Our main problems are with energy storage and transport, not generation. This is why we need liquid fuels, like oil.
Unless you've figured out some radical, new, clean, dense, and lightweight battery source that you're not telling anyone about...

Re:wow ...

[DragonTHC]

Star Trek is REAL!

I'm gonna be Captain Kirk!

Still concave toward the plasma.

[Ungrounded Lightning]

I seem to recall one of Bussard's points in his talk Should Google Go Nuclear? was that plasma confinement by magnetic fields is inherently unstable when the confinement is concave toward the plasma, no matter how you twist them. Thus Stellarators, Tokamaks, etc. are (in his opinion) doomed. (And that's why his design is conVEX toward the plasma.)

(My take on that has been that even if passive geometries are unstable, if you can get it stable enough that instability growth occurs at no more than an HF rate you might be able to use an active system to finish the job of stabilizing the confinement. But that's a separate issue.)

This sounds familiar

[thatskinnyguy]

It seems that what they are trying to do is create an antimatter containment field to contain the matter/antimatter reaction. Bravo! We'll be going at warp speed in no time!

Re:This sounds familiar

[tazsl]

ANTI-MATTER. If you dont mind, it doesnt matter!

Power Drain Power Gain?

[Ztringz]

you've got a self-contained energy source that takes power to start, power to maintain, and the net energy gain is...? Make it dense enough, maybe we can produce antimatter

Re:wow ...

[toddhisattva]

"and to eliminate extraneous harmonics that may cause the magnetic surfaces in the plasma to deteriorate"

...overheard at a jam near Austin....

In Soviet Fusion lab...

[aqk]

Tokamak YOU!

Solar and wind?

[ttfkam]

Here we go again. The vast conspiracy against solar and wind by those evil baddies. Please.

Why not solar? The Solar Constant, that's why. 1.367kW/m^2. Typical yield is closer to 1kW/m^2. Then some genius suggests that we cover an area roughly the size of Arizona with solar cells to generate all of the power. Riiiiiiiiight. "Just cover all of the roofs, and we'll be set!" Riiiiiiiiiight.

http://apod.nasa.gov/apod/ap970830.html

Those are the roofs. Added up, they might add up to Arizona. Not likely though. Now imagine that you wanted to cover up Arizona with big pieces of paper, the whole state. I want you to imagine the scale of a project like that with just paper. Now I want you to reflect on the difficulty inherent with replacing all of that paper with silicon semiconductors that currently require clean rooms for manufacture.

Nevermind that we can't get 50% cells to last more than a couple months let alone ten years, and that's the expensive, lab-grown variety. But people still hold out hope for "printable" solar panels that get 50% efficiency and last fifty years.

Stirling engines? Sure, cover Arizona with Stirling engines. That's feasible. Riiiiiiight.

And wind? Yeah, let's hear it for the 5 or 6MW wind generators! Well, until you see the stats on land area they use up. Feel free to look up pictures of how big 6MW wind generators actually are. However, most generators aren't anywhere near that big. In fact most wind farms (collections of generators) tend to add up to that 5 or 6MW range all together. There just isn't enough wind. You can't produce energy out of nothing. It has to come from something. If the wind isn't blowing hard enough, no amount of money and research is going to extract thousands of megawatts out of it.

What? Offshore wind generators? Uh hunh, no maintenance involved in keeping mechanical devices with large moving parts in working order in the middle of those salt water oceans. No sir! We could just turn them on and walk away. Let's not even think about those big power cables headed for shore. Nope, those aren't a target for mischief.

Kites? Sure, as long as we ignore the fact that no one has actually been successful at getting 100 kilowatts-hours out of that even for a single hour. I haven't yet heard of a meager first step yet let alone something approaching a working prototype.

Or traffic wind generators? That one takes the cake. If someone can't grasp why traffic wind generators are a moronic idea, that person can't handle the real world. Transferring energy from wind to turn generators will slow the air. If the air is slowed, it makes the cars work harder to maintain speed. If the cars are working harder, they burn more fuel. See where this is headed?

Diablo Canyon and San Onofre, the two nuclear plants in California, each have two working nuclear reactors on site. Each one produces more than 1,000MW. Hmmm... let's figure out how many 5MW wind generators it takes to add up to just one nuclear reactor. Be sure to keep that picture of the 5MW variety of wind generator around for reference.

Then there's the issue of how much wind you can get in most areas.
Added to the fact that nuclear reactors and coal plants don't depend on (in)consistent wind patterns, daylight hours, or weather conditions.

How much does wind blow? http://windeis.anl.gov/guide/maps/images/wherewind 800.gif

Be sure to focus on the amount of area that rates above "good." Notice how some states are COMPLETELY screwed with regard to wind power. What? Have some states sell their power to the other states, the completely energy dependent ones? Look up how well that worked when Enron, a Texas company, held sway over the energy supply of a different state, California. Now imagine that happening to a state with less clout than California.

Solar and wind are not going to save us. They are excel

Re:Solar and wind?

[Ed Avis]

Why not? There is a lot of empty space in Arizona.

Re:Solar and wind?

[mdsolar]

That is kind of a neat way of estimating the roofs. You can find a caluculation that takes a different approach here: http://mdsolar.blogspot.com/2007/08/roof-pitch.htm l. You'll see that you are incorrect is saying that the area needed is the size of Arizona. An area that is 80 by 80 miles will do it.

You are also incorrect on the durability of solar panels. They last 25 years at better than 80% rated capacity and will likely last 100 years at better than 40%.

On wind, current capacity is 74 thousand MW, so your contention that thousands of megawatts can't be generated seems a little strange given that it is already happening: http://en.wikipedia.org/wiki/Wind_power.

Nuclear power is a little bit inflexible. Choosing plants that are on the seacoast may not be the best example of a reliable energy source: http://mdsolar.blogspot.com/2007/08/cliffhanger.ht ml.

Once you see the problem with your calcualtions, I think you'll be much more optimistic about the renewable energy future.
--
Save money with solar power: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html

Re:Solar and wind?

[ttfkam]

Go back and read my post again. Please.

I was not commenting on their percentage output based on longevity. No solar panel has ever been 80% efficient as a percentage of the Solar Constant . No panel will EVER get 100% of the Solar Constant. No energy transfer mechanism in the real world will ever be 100% efficient.

Nevada has regions that get 9 kWh per square meter of sunlight per day on average over a year, or 375 Watts per square meter of average power. At 20% efficiency you get 75 of those. So we just divide the 1.2 TW of energy we use that we calculated earlier by 75 W per square meter to get the number of square meters we need. Divided again by a million gives 16000 square kilometers. The square root of this, 126 km, gives the length of the edge of the square which is about 80 miles.

Okay, let's take a closer look together. You see that 20% reference? That does NOT mean the solar cells working at 20% of their capacity; that means that the solar panels are working at 20% of what nature allows. Big, big difference.

It was nice of them to average out between day and night, which is where they got their 75W/m^2 average (after 20% factor). The sun shines between six and eight hours for solar panels in the best case. Yes, there is some light near sunrise and sunset, but the real power doesn't start coming in until the middle six to eight hours of the day. Which means you have to store that power. That means batteries. Ever feel the battery on a laptop while it's in use or charging? It's warm, isn't it?

That heat means loss, a non-trivial amount in fact. Nevertheless, 75W/m^2 means that for every square meter, you can run a single 75W lightbulb all day long. One. Just one. Modern gaming computers have 500W power supplies and more. Simple math really. Now let's talk about washing machines, dryers, refrigerators, freezers, dishwashers, etc. Washers and dryers use a lot of power, but they are only on for short periods of the day. Refrigerators on the other hand...

So now you're trying to convince me that 6,400 square miles (square of 80 miles on each side) will solve all of our problems. Sure, that's a far smaller number than the 113,635 square miles in Arizona.

BUT!

You've provided for Nevada, one of the states with the lowest population density and consistent sun. What about Washington State? Just run a 1,000-mile power cable? I can guarantee that you won't get 75W except in the height of summer in Washington State.

AND!

Your source neglects to mention that solar panels become less efficient when they become very hot. The baking deserts of Nevada and Arizona are not optimum locations for efficiency unless they are high deserts.

AND!

You have to manufacture 6,400 square miles of semiconductors. You can't reduce the cost substantially unless you stop needing a clean room. No, economy of scale doesn't work as well as you'd think. Why not? That computer you're typing on uses a massive amount of semiconductors. They have a massive amount of R&D invested in them. Are there any fast computers boards printed with an inkjet? No. That single innovation would reduce the cost of computers dramatically, but we're not there yet. There is absolutely no reason to believe that cheap, printable solar panels are just around the corner either, even with substantial monetary investment.

-------

Now on to wind. Once again, re-read my post and pay attention this time. I did not say that all wind power together could not add up to thousands of megawatts. I never said that. I said that individual wind generators and most wind farms cannot. My issue is with energy density: the energy density of wind and solar is not high enough. The question -- this is important -- is not nor has it ever been "can it produce power." The question is "can it produce enough power consistently 24/7/365.

Folks in Montana don't suddenly stop needing power in winter when t

Re:Solar and wind?

[mdsolar]

20% effciency means 20% of what the Sun provides. If you look a little deeper, the solar number is for a concentrator and such thermal plants are being built with thermal storage. No batteries, just dispatchable solar power with a good match to changes in seasonal demand. And, that 80 by 80 miles covers the whole energy use of the entire country, not just Nevada and not just electric generation. It is just an example. Other places will use panels, that is kind of the point of looking at what roof space is available. As pointed out, the batteries to make panels work 24/7 come basically as a freebee from transportation.

Nuclear power has economic, environmental, safety, proliferation and sustainablility issues that are intelocking and have not been adequately addressed. In my opinion, the economic issues, together with operational costraints http://mdsolar.blogspot.com/2007/01/why-renewables -displace-nukes-first.html will lead to much less nuclear power in the future. It will be displaced by renewable energy. Take a look at the numbers again. Remember that wind is cheaper than nuclear power by a lot and solar will be even cheaper than wind shortly. Thin film solar is already on the market and growing rapidly. One more pass, and I think you'll be persuaded. I don't have a crystal ball, but when money is involved, you can usually tell which way things will go.
--
Get going with solar: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html

Re:Solar and wind?

[ttfkam]

First, your links:

Nuclear power plants are not either 100% on or completely off. The reaction can be moderated to many shades of gray, just as the comments on your own blog mention. You are presenting a straw man: not accurately representing how the opposition works and then taking them to task using your own sketchy characterization.

Your second link deals with the benefits of decentralization. Once again, I have no argument with that. I am not against wind and solar use.

If you look a little deeper, the solar number is for a concentrator and such thermal plants are being built with thermal storage. No batteries, just dispatchable solar power with a good match to changes in seasonal demand.

Link, please. And yes, they are indeed batteries; they are simply not chemical batteries.

And, that 80 by 80 miles covers the whole energy use of the entire country, not just Nevada and not just electric generation.

You haven't addressed how to get that power from Nevada to the rest of the country without huge losses. Those numbers you gave only work for the 80x80 square in Nevada. This is like when the Catholic Church asserted that the Earth could support 12 billion people because a quarter of Iowa could produce x-amount of food, but completely skipping over the fact that most places on Earth aren't like that quarter of Iowa -- including other parts of Iowa!

Other places will use panels, that is kind of the point of looking at what roof space is available. As pointed out, the batteries to make panels work 24/7 come basically as a freebee from transportation.

A freebie? Now I'm worried. NOTHING is free. Are you suggesting shipping charged batteries on a truck or rail line from state to state and then returning them discharged? Please tell me you're not. Then again, even if you were, what is moving the trucks and the rail lines? Oil? Electricity? Please give more info.

Nuclear power has economic, environmental, safety, proliferation and sustainablility issues that are intelocking and have not been adequately addressed.

You're sidestepping my question. If you look back to read again, I specifically stated that nuclear's problems were not solved yet. I was asking a very pointed hypothetical: if we could address the waste issue, which to be honest is the linchpin to your other issues, would you still be against nuclear?

If the waste were minute in volume and had a short-lived hazard duration (for example, 100 years). If by using more of the fuel and leaving less waste, it was made more economically viable. If the waste had no vector for water/ground contamination. If there was no plutonium produced after the fuel was used. If the fuel source could last tens of thousands of years.

If all of those were true, would you be willing to support nuclear energy. It's a straightforward yes-or-no question. I'm not asking if you think these things are true today. I'm asking that if these things were true tomorrow, would your objection to it be diminished or eliminated?

If the answer is yes, this means you are rational. If the answer is no, you have adopted your stance as a religious issue, not subject to rational thought.

However, since you brought up environmental impact (with regard to nuclear), I might ask what the impact of all of those semiconductor photoelectric cells has on the environment during their manufacture. I know for computers, things can get fairly nasty. So tell me, what is the overall environmental impact of manufacturing 6,400 square miles of semiconductors?

Take a look at the numbers again. Remember that wind is cheaper than nuclear power by a lot and solar will be even cheaper than wind shortly. Thin film solar is already on the market and growing rapidly.

Yes, growing rapidly at 20% efficiency. Look, I'm not arguing with you that we sho

Re:Solar and wind?

[spectecjr]

You really don't want to do it this way anyway:
Those are the roofs. Added up, they might add up to Arizona. Not likely though. Now imagine that you wanted to cover up Arizona with big pieces of paper, the whole state. I want you to imagine the scale of a project like that with just paper. Now I want you to reflect on the difficulty inherent with replacing all of that paper with silicon semiconductors that currently require clean rooms for manufacture.

Much better solutions are coming online. Like hydrogen-producing algae beds. Which solves half of the problem - how to produce a basic energy source. It's distributable too - plants are much better at this whole photosynthesis thing than any solar cell we've come up with, and it'd work in some pretty dark and gloomy conditions (Washington state).

The other half of the problem is how to move energy around without it being wasted so much, and how to store it. Electricity is the obvious mechanism for moving it around - we've got the infrastructure there. But how to store it?

Carbon nanotube batteries/ultra capacitors are the way to go here. If the technology comes along as expected, it could mean a revolution in the way we use energy. Forget generators, or gas tanks, or anything like that - just put these puppies everywhere. In cars. In your house. Your car needs filling up? Go to the "gas" station and charge it up right there in seconds. Or have a mechanical arm that just swaps the battery out for a fresh one.

The reason I like this plan?

The algae beds are a great way to produce hydrogen. Which is a great way to fuel fusion reactors or other kinds of engines. You don't need to ship the hydrogen anywhere to use it - you can produce it at the site it's going to be used. You don't need to worry about making vehicles that burn the hydrogen as fuels or the safety concerns related to that - all of your energy gets stored in the carbon nanotube batteries.

If I had a big chunk o' money to bet with, I'd be putting all my money on this right now as being the most likely eventual energy solution.

Or traffic wind generators? That one takes the cake. If someone can't grasp why traffic wind generators are a moronic idea, that person can't handle the real world. Transferring energy from wind to turn generators will slow the air. If the air is slowed, it makes the cars work harder to maintain speed. If the cars are working harder, they burn more fuel. See where this is headed?

Traffic wind generators aren't a bad idea. The vehicles are going to displace air anyway - whether you're taking energy from it or not. If the generators are far enough away from the vehicles, the vehicles are still doing as much work as they were before, but the disturbance they're creating won't just bleed off - it'll be usable.

My hunch would be (I've not done the math, and frankly fluid dynamics gives me the heebie jeebies - damn you, Navier Stokes) that if a lane of traffic is 4m wide, a 16m wide semicircular "capture" zone of fans will grab the wind without affecting the pressure that the vehicle in the middle is working against too much. It'll be like a soliton wave around the car.

An alternative, probably better idea though, is to use something similar to supercavitation on the vehicles to minimize their drag instead of trying to reclaim the energy from it. I can't remember the name used to describe the process in air, but it involves creating vortices at the leading edge of the vehicle to reduce the drag on it. Some experiments on semi trucks and planes were showing great promise at one point, but I can't dig up any references right now.

Re:Solar and wind?

[mdsolar]

Nuclear power plants can be moderated, but they are designed to run at nameplate capacity. Attempting to use them as dispatchable sources takes extra engineering. You might do the engineering, but this also raises operating costs.

I hesitate to call thermal storage a battery just as I would a dam. But, here is a link describing Solar One in Nevada: http://en.wikipedia.org/wiki/Nevada_Solar_One. You may want to follow some of the links there. As you'll see, the intent is to supply California, not the whole nation. As Washington supplies Southern California, this not at all usual: http://mdsolar.blogspot.com/2007/03/coast-to-coast .html. Again, the 80 by 80 miles thing is an example to get people to understand that energy density is not a problem for renewable energy. No one is proposing carrying it out this way. Roofs on homes can provide 46% of all the generation we use now, and more than 100% of the residential electricity use. That is for 17% efficient systems. In this case there is no need for new transmission capacity. I don't think you are quite understanding that the number used for the roof calculation was taken from the center of the country and was appropriate to panels. There is no Iowa thing going on. Please read more carefully. This is all explained.

With regard to the freebee, that is also explained. Many people point to the storage in plugin hybrids as being enough for most commutes plus night time use of electricity. On the other hand, this is not all that smart. Transportation grade batteries are pretty special and using them for household storage is not a great use of their specialization. But, what PG&E is positioning itself to take advantage of it that degraded transportation grade batteries are still better than most batteries so they'll use the batteries coming out of cars for stationary storage. This is also explained. Yes, nothing is free, but both the cost for transportation and the cost for stationary use is reduced owing to the extended use of the batteries. Moving the electricity around is done with wires, something PG&E has experience with. Now, here is the importance of distinguishing thermal storage from batteries: Thermal storage stores energy well with a high energy density, at least with the molten salts used at Solar One. But, it only makes sense if you store it this way prior to conversion to electricity. You are going from high entropy to low and so lose about two thirds of the energy in the conversion. (All thermal generation is like this including coal and nuclear.) Light, like electricity is low entropy, so if you are using quantum mechanical means to convert light to electricity you do not suffer the entropy problems that thermal systems have. Your digital camera, for example, has about 80% conversion efficiency though this is effected using a bias voltage so you can't turn a detector into an energy device. But, PV cells do do this using the doping gradient though they are bandwidth limited owing to the energy bandgap. Laboratory cells already manage greater than 40% efficiency owing to careful matching of bandgaps to the incident light energy quanta. They'll surpass 50% in a couple of years. So, you do not want to lose this efficiency gain by converting to thermal energy and then back to electricity. Batteries do a much better job at preserving the low entropy of electricity because they try to work with a single degree of freedom, a chemical latch. Some lithium batteries are 99% efficient http://en.wikipedia.org/wiki/Battery_(electricity) #Conversion_to_energy. You can get better than 90% transmission efficiency over 2000 miles with high voltage DC http://www.abbaustralia.com.au/c

Re:Solar and wind?

[mdsolar]

Actually, solar cells are more efficient than plants but in fact, lab cells have greater than 40% efficiency, and in practice, algae based fuel production only reaches about 15% efficiency which is lower than commercial solar panels (19% efficiency). There could be lower costs in using ponds and such, but it is not a more efficient use of surface area. So far, accelerated algae growth is dependent on a concentrated source of CO2, a coal or gas fired power plant at commercial scale: http://mdsolar.blogspot.com/2007/02/photosynthesis .html.

The amount of fuel needed for fusion is tiny but it will likely be deuterium so producing hydrogen does not get you far.

Re:Solar and wind?

[ttfkam]

You make some great points, thank you. You also avoid answering my question yet again.

Call me an optimist, but 300 generations should be enough to make fusion viable.

Which raises another question: if fusion technology became viable (a big if, I know), would you have any major objections? After all, it would produce a very large amount of energy using a very small yet abundant fuel source, generate no long-term waste, no appreciable environmental impact, and will be around for as long as heavy hydrogen exists in the universe, i.e., longer than the human species.

Don't get me wrong, you made some great points other than the 40-50% lab cells. Those lab-grown cells have typical lifespans measured in weeks or months. They are far cries from usable tech let alone mass production.

But once again, you made great points. All I ask is that you answer my two questions. That's all, and I'll concede the point.

Re:Solar and wind?

[mdsolar]

The two main objections I see to fusion right now are 1) too little too late and 2) thermal pollution. Both might be dealt with, the second more easily.

Renewables turn out to be very inexpensive. There is an energy plan going around call Energize America http://www.dailykos.com/story/2006/5/18/62733/6577 that includes a chart that takes selectively from this link: http://www.crest.org/repp_pubs/pdf/subsidies.pdf. So, the big dramatic number which shows up in the chart is that the subsidy for nuclear power in its first 15 years of development was $15/kWh generated, which is comapred to wind at $0.46/kWh generated. There are problems with making such comparisons because some problems are harder than others and take more time to develop. But there is some validity too. From the pdf, the number for solar is about $7/kWh generated. Nuclear power converges towards a subsidy of $0.012/kWh which can't reduce much further owing to the the arrangements on liability and waste that fusion, solar and wind will not face so they can tend to zero. Note that this subsidy makes the actual cost of nuclear power higher than for coal. So, now that wind is cheaper than both coal and nuclear power and solar is headed towards an even lower price, where will fusion fit in? It's first 15 years, subsidy per kWh generated is infinite; again we see the problem of picking a fixed span. But, can it beat solar on price? Most plans have a replacement of the lithium blanket every couple of years so you have to work in a very hot environment and do precision machine work. This kind of effort is going to be similar to refueling in a nuclear plant. I think this alone makes the lowest possible cost for (big) fusion about $0.04/kWh. But it looks good for solar to get to 0.007/kWh. So, even if you have to pay for storage, the base cost of the power generation is going to be hard to beat. Another thing about renewable energy is that once it is in place, there won't be much reason to change. Thus, the market for fusion would only be for new generation. But, new generation may not be much needed when fusion is ready because the world population is projected to stabilize about then so energy markets may not be experiencing much growth.

The problem of thermal pollution is perhaps not so hard. This one is easily handled with dilution. But, you do need a place to dilute and that usually means a river. Just as we have run out of rivers to dam, a large deployment of fusion may run out of rivers to warm. This already happens for nuclear power in Europe in the summer time.

I usually find a way to celebrate when fusion reaches a mile stone. But I think we'll end up using it in niche applications like propulsion and dark outposts, perhaps in the oceans and space. The power-to-weight ratio should make it attractive for the outer solar system for example. The power-to-weight ratio for those lab-grown cells that you dislike is the main reason solar power is chosen for work in the inner solar system. 17% efficient silicon is about 200 times better than coal on the surface of the earth. On orbit the 30% efficeint cells are about 3000 times better than coal given the better sunlight and lack oxygen. Durable 50% efficient cells will be here before fusion I think. The article I cited has commercialization in three years. These are intended for soldiers in the field.

Spherical Stellarator

[amchugh]

Spherical Stellarator

Re:Stellarators have been around as an idea for ye

[DerekLyons]

No, they are not immune to the effects of a magnetic field. Nor however are they easily effected by them. But that has nothing to do with my point - the fusion inside a Stellarator *is* going to generate neutrons, and those neutrons have to go somewhere. They can't simply be trapped forever.

Re:Stellarators have been around as an idea for ye

[kravlor]

Sorry, but fusion works. It is completely proven as a physical mechanism -- look at the Sun! Look at the fusion reactors in which we've generated hundreds of megawatts of fusion power (not breakeven conditions); look at particle accelerators...

So, keep your faith in humanity; just because some ignorant asshat wants to blurt blatantly incorrect things like "water isn't wet" or "gravity doesn't work" doesn't mean it's true.

Re:what took so long?

[The_Wilschon]

These are very very different problems. Furthermore, the idea of using magnetic fields to confine plasma for fusion is not a new one at all. (Actually, the stellarator is not even a new design for a magnetic confinement reactor, so, without RTFA, I'm not sure why we have a /. story about it.)

Re:Stellarators have been around as an idea for ye

[Grishnakh]

Yes, I know fusion is proven, that was my point.

But it doesn't seem like it's just a few ignorant asshats blurting blantantly incorrect things, it seems like it's most people. After all, look how many people go around saying evolution is false and the earth is 6000 years old. Even here on Slashdot, a geek haven, there's tons of them. No one understands, or even wants to understand basic science any more. I think we're headed into another Dark Ages.

Re:STELLLLAAAAA!

[Wolfrider]

+1 Insightful; espec. if Stella is a Nuclear Reactor op.

--Anyhow -- Star Trek knew about the whole "magnetic bottle" thing back in the 60's. They were talking about "dilithium crystals", but the concept evidently carries over IRL.

It's published, not "up for peer review"...

[posterlogo]

PNAS does not post papers in review on its web site. This paper was PUBLISHED online on July 17th.