Is My Idea Valid? Nuclear Fusion Power

[Teen4Ideas]

So as we all know (or at least I assume) Global Warming is real and happening, I am a teen, 17, and not trying to get answers for homework or anything like that.

I just want to know, is it possible to create fusion using the temperature found at active Geo-thermal sites to reach the temp needed for nuclear fusion, combined with proton-proton fusion process(or Similar) to create a viable fusion reactor?

I know the temp needed for fusion is 400 degrees Celsius, such a temp is found at actives sites from what I've read, and I've read that the Tokamak Nuclear Test Reactor has achieved both the density and temp need for fusion but is unable to do both at the same time, would this fix this problem? And is this too wordy? Is this a dumb idea?

 

[jedishrfu]

I think your temperature is a bit off from this chart its in the millions of degrees celsius.

http://www.uni.edu/morgans/astro/course/Notes/section2/fusion.html

 

[Teen4Ideas]

you are correct let me check back to revise my figures

 

[Teen4Ideas]

You know the first time I saw the figures it seemed to make sense, seriously it did, and now I feel kind of silly, I must have miscalculated somewhere and added a zero or something similar...darn...

 

[Teen4Ideas]

if its not possible to reach the temp needed for fusion, then perhaps I can figure a way to reach the pressure needed

 

[jedishrfu]

I don't think that's what happened. I was looking at some charts on Wikipedia and they implied the same thing until I read the legend and its said measurement in millions of degrees.

Its always good to keep track of where you gather your info for times like this.

Don't feel foolish either, you need to make mistakes and do dumb things to appreciate the true experience of being right.

 

[Teen4Ideas]

Okay, where mind I find resources to help me with this stuff, it would be pretty cool to solve energy problems and eliminate need for fossil fuels use

 

[Teen4Ideas]

where might I find*

 

[Teen4Ideas]

"Its always good to keep track of where you gather your info for times like this.

Don't feel foolish either, you need to make mistakes and do dumb things to appreciate the true experience of being right."

Thanks, I got most of my info here:
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fusion.html#c1
I believe this is reputable?

 

[Drakkith]

Thanks, I got most of my info here:
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fusion.html#c1
I believe this is reputable?

Yes, hyperphysics is reputable. I enjoy the site quite a bit.

 

[Drakkith]

Okay, where mind I find resources to help me with this stuff, it would be pretty cool to solve energy problems and eliminate need for fossil fuels use

There are plenty of places online, such as wikipedia, hyperphysics, etc. Just watch out for those sites that claim to have invented some device to generate power that's cheaper, easier, or safer than current technology, but that its being repressed or covered up by mainstream science/government/whoever. Also, if it sounds too good to be true, it probably isn't true. There is a LOT of misinformation out there.

 

[rootone]

You won't be able to achieve fusion with typical stuff found in hardware stores and assembled in your garage.
You'd need to build an apparatus capable of producing temperatures and pressures similar to those in the core of the Sun,
(and having a way to contain it)
Working fusion reactor designs do exist, but they require more energy to get them started than the energy they produce.
The latest attempt to produce a fusion reactor which could be economically feasible is this:
http://en.wikipedia.org/wiki/ITER

That is an international collaboration currently estimated to amount to a cost of €16billion, and it won't be ready even for trial testing until at least 2019.

 

[mfb]

Reaching 400°C is very easy, by the way. Every wood fire achieves that, steel production routinely uses temperatures above 1000°C. There is no need to use geothermal energy for those low temperatures.

Actually, reaching the necessary temperature is not the main issue for fusion. It has been achieved - getting fusion reactions can be done with existing machines. Keeping the plasma confined well and long enough to get more energy out than you put in is the hard part.

 

[Teen4Ideas]

I accidentally misquoted the degrees needed, its not 400 degrees Celsius, its 15-40 million degrees, I am aware of the sites that are test reactors, as well as various ways to contain the energy, magnetic, etc... I was pointing out how one test reactor, mentioned above, managed to get very close to Lawson criterion, I thought if the temp problem was solved with no artificial help, then focus could shift to solving density problem, instead of trying to do both, I did not get the figures right. I apologize.

 

[Teen4Ideas]

Would heavy water, which contains tritium, be a viable substitute for breeding tritium from lithium? And could a laser combined with magnetic containment-using heavy water be better than lithium, I can't find which one slows neutrons more, heavy water or lithium, I would think heavy water would be better, as it could serve a similar function as if it were in a fission reaction. Or am I completely off track?

 

[Teen4Ideas]

What makes a d-t reaction better than a d-d reaction cycle? I would be most appreciative if anyone could suggest a resource with these figures and arguments...

 

[the_wolfman]

What makes a d-t reaction better than a d-d reaction cycle? I would be most appreciative if anyone could suggest a resource with these figures and arguments...

D-T has the lowest break-even temperature of any of the fusion reaction. It is the easiest fuel to ignite.

Some of the other fuels have advantageous features, and they are worth considering for 2nd or later generation reactors. But the first generation reactors will likely use D-T simply because it is the easiest.

Normal heavy water contains deuterium not tritium. Deuterium has a relatively low neutron capture cross-section, and it isn't efficient at producing tritium. Li is chosen as breeder material because is has a relatively high probability of absorbing neutrons and producing tritium.

 

[mfb]

There are a few tritium atoms in water (and heavy water can be extracted by isotope separation of hydrogen from regular water), but the amount is way too small to be useful.

Fission reactors use water as moderator - atoms that slow down neutrons without absorbing them. For fusion, you want that absorption to produce tritium, so you have completely different goals.
Tritium breeding has nothing to do with the magnetic confinement or lasers.

What makes a d-t reaction better than a d-d reaction cycle?

A factor ~100 higher reaction rate.

You can find answers to most of your questions at Wikipedia.

 

[Teen4Ideas]

Alright, so d-t reaction it is. Lasers or Ion beams kick start the reaction and magnets confine it, but wouldn't you still need a moderator to stop the reaction in an emergency? So the heavy water could serve a double purpose, neutrons from the reaction would create more fuel(tritium) albeit slowly, thus should the need arise you could stop the reaction with said water, correct? Do I make more sense now? No need for lithium breeder reactors...

Stronger magnets means more push to fuse right? And the lasers/Ion beams can create the heat aspect needed correct? I hope I make more sense now

 

[Teen4Ideas]

Wait just thought of something...do you need equal parts tritium and deuterium or do you need more deuterium than tritium?

 

[rootone]

If by 'an emergency', you mean there could be containment failure, the reaction immediately ceases anyway, but I'm sure escaping plasma would do considerable damage to the very immediate area, by which i mean around .5 km perhaps.1km
Unlike a fission reactor meltdown, you would not have the problem of large amounts of heavy radioactive elements polluting the environment and widely dispersing.

 

[Teen4Ideas]

Right, the reaction would stop immediately but all those neutrons would need to be stopped right? and as for the plasma, what material can absorb those ions or absorb most of the force in the event of an explosion?

 

[the_wolfman]

Alright, so d-t reaction it is. Lasers or Ion beams kick start the reaction and magnets confine it, but wouldn't you still need a moderator to stop the reaction in an emergency? So the heavy water could serve a double purpose, neutrons from the reaction would create more fuel(tritium) albeit slowly, thus should the need arise you could stop the reaction with said water, correct? Do I make more sense now? No need for lithium breeder reactors...

Stronger magnets means more push to fuse right? And the lasers/Ion beams can create the heat aspect needed correct? I hope I make more sense now

Neutrons play no role is the sustainment of a fusion reaction. You can not use a (neutron) moderator to control the fusion reaction. If you want to slow a fusion reaction you need to decrease the density and/or decrease the temperature. Both of these things happen naturally when you lose magnetic confinement. This is one of the appealing aspects to nuclear fusion. In the event of an accident, there is no risk of a sustained uncontrolled reaction.

Tritium does not appear in nature. We have to manufacture it and Deuterium simply does not have a sufficiently large cross section to breed sufficient amounts of tritium. In-order to sustain a D-T reaction we have to breed tritium as quickly as we burn it. Each D-T reaction produces 1 neutron. And then we have to use that neutron to produce 1 new tritium atom. This is a critical balance that we have to maintain. If we don't produce enough neutron, then we will quickly use up our supply of tritium. On there other hand, there are serious weapon proliferation issues if make to much tritium. Li is nice because it has the a high reaction cross-section. There are also two different isotope of Li that have different reactions that produce tritium. We can adjust the ratio of the two isotopes to control the rate of tritium production.

The fusion reaction rate increases with the pressure (density times temperature). Stronger magnets allow you to operate at higher pressure, but the strength of the magnetic field does not directly heat the plasma.

There are many ways to heat a plasma. Magnetically confined plasmas are typically heated using a combination of ohmic heating, neutral beam heating, and rf heating. Inertial confinement, which is a very different concept, uses lasers and ion beams.

 

[the_wolfman]

If by 'an emergency', you mean there could be containment failure, the reaction immediately ceases anyway, but I'm sure escaping plasma would do considerable damage to the very immediate area, by which i mean around .5 km perhaps.1km
Unlike a fission reactor meltdown, you would not have the problem of large amounts of heavy radioactive elements polluting the environment and widely dispersing.

Not really. While a magnetically confined plasma is really hot, it has a really low density. The total energy stored in a magnetically confined plasma is relatively small. An uncontrolled accident will likely damage the confinement device, but it will not cause damage surrounding vicinity.

The biggest concern is that the accident will bore a hole through the confinement vessel and tritium will escape to the environment. There are a number of safety systems in place to prevent the tritium for escaping. There are also a number of regulation which limit the amount of tritium inventory in or aground the reactor.

 

[rootone]

I was thinking more of acoustic shockwaves than damage directly from plasma, but maybe even that would be very localised. 0.5km was I admit purely a hand-wavey guess.

 

[Teen4Ideas]

If you want to slow a fusion reaction you need to decrease the density and/or decrease the temperature. Both of these things happen naturally when you lose magnetic confinement.

We have to manufacture it and Deuterium simply does not have a sufficiently large cross section to breed sufficient amounts of tritium. In-order to sustain a D-T reaction we have to breed tritium as quickly as we burn it. Each D-T reaction produces 1 neutron. And then we have to use that neutron to produce 1 new tritium atom. This is a critical balance that we have to maintain. If we don't produce enough neutron, then we will quickly use up our supply of tritium. Li is nice because it has the a high reaction cross-section. There are also two different isotope of Li that have different reactions that produce tritium.

The fusion reaction rate increases with the pressure (density times temperature). Stronger magnets allow you to operate at higher pressure, but the strength of the magnetic field does not directly heat the plasma.

There are many ways to heat a plasma. Magnetically confined plasmas are typically heated using a combination of ohmic heating, neutral beam heating, and rf heating. Inertial confinement, which is a very different concept, uses lasers and ion beams.

Note-I'm 17, just bouncing ideas, so I don't know how effective the heavy water would be at producing tritium, however, there must be concerns about producing breeder reactors... so assuming the pellet is used to start reaction why can't heavy water be used to sustain it?
What is the probability of producing tritium with heavy water vs lithium? I would think that all that plasma being contained at such high pressures would obliterate the plant and and any unabsorbed neutrons would be released.So is the tritium as pointed out above, so still my point remains, why shouldn't heavy water be used at least as a way to reduce need for lithium breeding? And why can't concepts from Inertial and Magnetic confinements be used?

http://en.wikipedia.org/wiki/Magneto-inertial_fusion I don't understand what the liner is but I assume it is like a moderator?

 

[Teen4Ideas]

Oh, wait now I know, you want the neutrons to heat the wall, so forget the heavy water as a moderator, but as a remedial source of tritium is it viable? and could a d-t reaction provide the necessary temp for a d-d reaction?

 

[the_wolfman]

Note-I'm 17, just bouncing ideas, so I don't know how effective the heavy water would be at producing tritium, however, there must be concerns about producing breeder reactors... so assuming the pellet is used to start reaction why can't heavy water be used to sustain it? What is the probability of producing tritium with heavy water vs lithium? I would think that all that plasma being contained at such high pressures would obliterate the plant and and any unabsorbed neutrons would be released and so is the tritium as pointed out above, so still my point remains, why shouldn't heavy water be used? And why can't concepts from Inertial and Magnetic confinements be used? http://en.wikipedia.org/wiki/Magneto-inertial_fusion I don't understand what the liner is but I assume it is like a moderator?

Its healthy for a 17 year to be asking questions. You have a few misconceptions as to how a fusion reactor works, and I'm trying to correct them as I see them. But please don't get the wrong impression. I like your curiosity.

Why do you think we should use heavy water in a fusion reactor. What use will it play? How does heavy water help one sustain a fusion reaction?

The big concern in sustaining a fusion reaction is energy confinement. A fusion reactor has to produce energy as fast as it losses energy. I don't see how heavy water can positively effect this energy balance. At fusion relevant temperature. The heavy water will ionize and breakup into deuterium and oxygen ions. The deuterium is fuel, but the oxygen plays no role is fusion. Oxygen rapidly radiates energy, cooling the plasma. Instead of injecting heavy water into a reactor, its much better to inject pure deuterium. There is no reason to inject oxygen.

The second concern is breeding tritium. But this happens outside of the plasma inside the walls of the device. There is some concern about breeding too much tritium. But honestly the bigger issue right now is not being able to breed enough tritium. Lithium has a much greater probability of producing tritium than heavy water. I don't know the number off the top of my head. If we are struggling to produce enough tritium, then using a worse tritium source is not the answer.

Magnetically confined plasmas are high temperature but very low density. The pressure of the confined plasma is small as a result of the low density. Magnetically confined plasmas operate at pressure less than atmosphere. If they lose confinement, they will not obliterate the plant. Furthermore there is a thick biological shield that surrounds the reactor, protecting the plant operators and the general public from radiation (neutrons, gammas, etc).

My above comments are specially for magnetically confined plasmas, but most of them apply equally to hybrid magneto-inertial concepts. The liner is not a moderator. It is a metallic conducting shell that "traps" the magnetic filed. Compressing the liner compresses the magnetic field, which in turn compresses the plasma.

 

[mfb]

Lasers or Ion beams kick start the reaction

You need some heating, but no "kick start".

but wouldn't you still need a moderator to stop the reaction in an emergency?

Just relax the magnetic fields, the plasma spreads out, cools and fusion will stop immediately.

So the heavy water could serve a double purpose, neutrons from the reaction would create more fuel(tritium) albeit slowly

They would not produce more tritium compared to lithium. You need (on average) a bit more than one tritium produced per neutron due to losses in the system.

thus should the need arise you could stop the reaction with said water, correct?

That does not make sense.

Stronger magnets mean you can reach a higher density and/or higher temperature.
The fusion reaction is 1:1, slight differences might be interesting if tritium is rare for example, but in general you want a ratio close to 1:1.

If by 'an emergency', you mean there could be containment failure, the reaction immediately ceases anyway, but I'm sure escaping plasma would do considerable damage to the very immediate area, by which i mean around .5 km perhaps.1km
Unlike a fission reactor meltdown, you would not have the problem of large amounts of heavy radioactive elements polluting the environment and widely dispersing.

The energy in the fusion plasma is surprisingly small - it is sufficient to melt parts of the wall, but it won't damage anything beyond that.

 

[Teen4Ideas]

The big concern in sustaining a fusion reaction is energy confinement. A fusion reactor has to produce energy as fast as it losses energy.
The second concern is breeding tritium. But this happens outside of the plasma inside the walls of the device. There is some concern about breeding too much tritium. But honestly the bigger issue right now is not being able to breed enough tritium.

Magnetically confined plasmas are high temperature but very low density. The pressure of the confined plasma is small as a result of the low density. Magnetically confined plasmas operate at pressure less than atmosphere. If they lose confinement, they will not obliterate the plant. Furthermore there is a thick biological shield that surrounds the reactor, protecting the plant operators and the general public from radiation (neutrons, gammas, etc).

My above comments are specially for magnetically confined plasmas, but most of them apply equally to hybrid magneto-inertial concepts. It is a metallic conducting shell that "traps" the magnetic filed. Compressing the liner compresses the magnetic field, which in turn compresses the plasma.

First of all, thank you, thank you for being patient with me and explaining this stuff to me

Now, I thought you need both high density and high temp, of course, higher pressure means higher temp(sort of) like a pressure cooker, as for a liner would iron or gold be a good example of this? And what is a biological shield? Surely we don't have a web of ivy to absorb the radiation? And I still don't understand why ion beams/lasers/xrays can't be used to heat the pellet to critical temperature and then magnetic fields to contain it...Lasers have reached the necessary temp for d-t reaction just not density

 

[the_wolfman]

I honestly don't know what metals they use for liners. It has to be highly conducting, but ideally you want it to be cheap. A guess is that they use copper. But there may reasons for using other metals too.

The biological shield is just what we call the shielding that surrounds the reactor protecting humans (and other biological organisms) from the radiation.

You can't heat a magnetically confined plasma with an ion beam because the magnetic field will deflect the ions.

We can heat the plasma using radio-frequency (rf) sources. However, we use frequencies that are absorbed by the plasma.
Most laser light and x-rays are the wrong frequency, and they will pass through the plasma. Instead we often use mircowave sources.

And I still don't understand why ion beams/lasers/xrays can't be used to heat the pellet to critical temperature and then magnetic fields to contain it

It sounds like you're thinking of a hybrid-method that uses inertia confinement to compress a pellet, and then magnetic fields to confined the compressed pellet? This won't work because the magnetic fields needed to keep the pellet compressed are huge. We simply don't have the technology necessary to create the necessary magnetic fields.

 

[dvp2015]

you are correct let me check back to revise my figures

google for ITER or JET, JET actually achieved positive output of energy. Is it "viable" depends on point of view. The profitable energy production looks possible, but we need years of hard work to achieve this. Anyway to ignite burning one need to provide the input power of gigawatt level (the production will gain dozens gigawatts). You can retrieve some energy from hot water sources, as from any other one, but for gigawatt level you need too many sources of that power density around.

 

[Mark Harder]

Okay, where mind I find resources to help me with this stuff, it would be pretty cool to solve energy problems and eliminate need for fossil fuels use

I'm not saying you're doing this, but I want to point out that people seem to have a tendency to look for 'the' solution to the energy problem. Don't get me wrong. Fusion is a fascinating topic and fusion may be such a powerful technology that it will take over the world, but it's probably a long way in the future. There are articles in Scientific American and American Scientist about fusion issues and developments. A lot of attention in the popular press focuses on the technological issues you mention, but some think solving the temperature + pressure problem may be easy compared to the challenges in engineering the materials used in a reactor (as we presently conceive of such) and obtaining and managing the fuel used. Then there are the folks who propose mining the Helium-3 isotope on the moon, since, they say, it's relatively plentiful there and it would be a better fuel than radioactive hydrogen-3. Another fascinating possibility is the Liquid Salt Thorium Reactor. India and China are sinking a lot of resources into engineering one of these. The idea has been kicked around since the '50s, and it may come to fruition a lot sooner than fusion and especially mining the moon. It has some important advantages over uranium-plutonium power, among them the difficulty of using it to create weapons-grade material, and a bountiful supply of thorium minerals around the world. India has the stuff lying around some of their beaches. Thorium reactors may become a way for poorer nations to supply themselves with electric power without creating fuel for bombs. There was an article about the thorium fuel cycle in American Scientist a few years ago. In the meanwhile, my guess is that we'll have to make do with several cleaner sources than fossil fuels, with no one of these dominating the field. And don't forget the best solution to energy problems is not using the energy in the first place! Conserving energy and reducing consumption of goods that require energy to make will go a long way toward reducing fuel use and greenhouse gas emissions. That's not a popular idea in some quarters. It may require some sacrifice on the part of consumers. If you're interested in solving energy problems technologically, you could research the efforts put into more efficient and less polluting technologies, and don't neglect the social and economic issues such solutions create.

 

[mfb]

google for ITER or JET, JET actually achieved positive output of energy.

Positive in the way that they got fusion power - yes. But no fusion without continuous heating, and fusion power was lower than this heating power. With more than 50% conversion of thermal power to electricity this could be used to generate electricity, but that is questionable (getting more than 50% conversion is tricky), and it is certainly not enough power for a power plant.

Anyway to ignite burning one need to provide the input power of gigawatt level (the production will gain dozens gigawatts).

No current or planned reactor is designed for dozens of gigawatts. The plan is always to get a few GW thermal power, for something like 1 GW electric power - similar to fission power plants.

 

[Teen4Ideas]

We can heat the plasma using radio-frequency (rf) sources. However, we use frequencies that are absorbed by the plasma.
Most laser light and x-rays are the wrong frequency, and they will pass through the plasma. Instead we often use microwave sources.


It sounds like you're thinking of a hybrid-method that uses inertia confinement to compress a pellet, and then magnetic fields to confined the compressed pellet? This won't work because the magnetic fields needed to keep the pellet compressed are huge. We simply don't have the technology necessary to create the necessary magnetic fields.

Instead of containing all that force, why can't you just redirect it? Like in a torus? Have an inflow valve from the initial reaction chamber into the torus, then just loop the plasma right? Are you getting tired of this conversation yet?