The SCIENCE & TECHNOLOGY News Thread

[Dhomochevsky]

There is a star right up there, that works well with solar panels and wont turn off anytime soon.

A fusion plant on earth would be nothing like star.
For one thing, it would be much hotter, less dense, and would stop the moment anything goes even slightly wrong.
Usually the fusion chamber is mostly a vacuum and heavily shielded, so whatever light is produced in there, won't get out to any solar panels.

What we can get out of it is heat and fast moving particles.
The particles are more of a problem, they tend to grind down our carefully built fusion structures over time.
We can use the heat to make electricity, the same way we always have.

[Dr. Casey]

Originally Posted by Hasumi-chan the Genius

Stars are giant Nuclear Fusion Plants.

Nuclear Fusion on Earth would just that; an artificial star.

Thank you, I finally understand. By the time fusion comes about, solar cells will likely be much cheaper than they are at present considering the rate at which solar energy is improving. I read a few weeks back that, in the United States, solar-powered systems are being installed for homes once every four minutes, compared to once every 80 minutes in 2006 (that comes out to 18 installations per day in 2006, vs. 360 per day in 2013).

[AnimeFan188]

Originally Posted by Dr. Casey

Thank you, I finally understand. By the time fusion comes about, solar cells will likely be much cheaper than they are at present considering the rate at which solar energy is improving. I read a few weeks back that, in the United States, solar-powered systems are being installed for homes once every four minutes, compared to once every 80 minutes in 2006 (that comes out to 18 installations per day in 2006, vs. 360 per day in 2013).

By the time Fusion power is practical, I wonder if Thorium reactors will already be
in service?

[Anh_Minh]

Originally Posted by Dr. Casey

Thank you, I finally understand. By the time fusion comes about, solar cells will likely be much cheaper than they are at present considering the rate at which solar energy is improving.

Solar cells that wouldn't melt or malfunction when exposed to the kind of heat you'll get in there?

Just because it's touted as a "miniature star" doesn't mean we have to use solar cells. Just boil water.

[Dextro]

Originally Posted by Anh_Minh

Solar cells that wouldn't melt or malfunction when exposed to the kind of heat you'll get in there?

Just because it's touted as a "miniature star" doesn't mean we have to use solar cells. Just boil water.

Yhep. Boiling water on a reactor isn't particularly inefficient anyway since most of the energy is already being released as heat anyway.

Btw the difference between Fusion and Fission, if I remember my chemistry correctly is that what we have now (the latter, Fission) you break a large atom apart resulting in two smaller particles that go on to break another big particle apart and so on until there's no more collisions going on. It works but there's effectively no good way to stop it once it gets going since it's not particularly easy to catch moving atomic particles.

In Fusion on the other hand you force a collision between two atoms to generate a new, larger atom. During this collision bits of the atoms are destroyed and converted to energy. The main theoretical advantage Fusion has over Fission is the stopping process: in order to stop it all you have to do is stop feeding the system. Since the larger atoms aren't prone to colliding they'll just sit there and the reaction will end. So theoretically there's no more danger of a meltdown on a Fusion reactor.

Now the problem is, as was already mentioned, that we haven't found a way to actually get a Fusion reactor to generate more power than we introduce into the system (and I'm pretty sure I missed something in my explanation. It's already been about 10 years since I learned this stuff and I wasn't even very good at it anyway which probably means I won't be building a DeLorean any time soon ).

[Ithekro]

Standard Fusion (from my understanding) is basically what the sun does. Smash hydrogen atoms together. This releases energy and makes a helium atom unsually. Stars that run out of hydrogen try to burn helium. This is when they expand.

[Anh_Minh]

Originally Posted by Dextro

Yhep. Boiling water on a reactor isn't particularly inefficient anyway since most of the energy is already being released as heat anyway.

Btw the difference between Fusion and Fission, if I remember my chemistry correctly is that what we have now (the latter, Fission) you break a large atom apart resulting in two smaller particles that go on to break another big particle apart and so on until there's no more collisions going on. It works but there's effectively no good way to stop it once it gets going since it's not particularly easy to catch moving atomic particles.

Not quite. When the atoms split, they produce smaller atoms or ions and neutrons. (And gamma rays. And electrons and positrons.)

It's the neutrons hitting certain nuclei (uranium, mostly) that make more fission reactions... and more neutrons. But some neutrons are lost without triggering a fission. Either because they exit the reactor without hitting a nucleus on the way, or they bounce, or they are absorbed by the wrong nucleus...

Now, reactors have control rods. Those rods are full of "wrong nuclei" which can take an additional neutron or more without splitting. By inserting more or less of the control rods, you control what proportion of the neutrons are lost (and where, but let's say it doesn't matter here). Ideally, you lose as many neutrons as you make, and everything's stable. But if you want to stop the reaction, you just drop all the rods into the reactor, you lose a lot more neutrons than you make, which results in fewer fission reactions, which results in fewer neutrons, and so on, until all you have to worry about are the fissions that are made by material just sitting around (the radioactive decay).

In Fusion on the other hand you force a collision between two atoms to generate a new, larger atom. During this collision bits of the atoms are destroyed and converted to energy. The main theoretical advantage Fusion has over Fission is the stopping process: in order to stop it all you have to do is stop feeding the system. Since the larger atoms aren't prone to colliding they'll just sit there and the reaction will end. So theoretically there's no more danger of a meltdown on a Fusion reactor.

I'm not so convinced. I mean, we're talking about safety because we're afraid something will go wrong. So what we should worry about is "what will happen to the super-hot plasma that'll already be there when and if the reactor experiences a failure of some kind?"

[Dextro]

Originally Posted by Anh_Minh

Not quite. When the atoms split, they produce smaller atoms or ions and neutrons. (And gamma rays. And electrons and positrons.)

It's the neutrons hitting certain nuclei (uranium, mostly) that make more fission reactions... and more neutrons. But some neutrons are lost without triggering a fission. Either because they exit the reactor without hitting a nucleus on the way, or they bounce, or they are absorbed by the wrong nucleus...

Now, reactors have control rods. Those rods are full of "wrong nuclei" which can take an additional neutron or more without splitting. By inserting more or less of the control rods, you control what proportion of the neutrons are lost (and where, but let's say it doesn't matter here). Ideally, you lose as many neutrons as you make, and everything's stable. But if you want to stop the reaction, you just drop all the rods into the reactor, you lose a lot more neutrons than you make, which results in fewer fission reactions, which results in fewer neutrons, and so on, until all you have to worry about are the fissions that are made by material just sitting around (the radioactive decay).

Like I said, I'm super rusty at this. Thanks for the correction

Originally Posted by Anh_Minh

I'm not so convinced. I mean, we're talking about safety because we're afraid something will go wrong. So what we should worry about is "what will happen to the super-hot plasma that'll already be there when and if the reactor experiences a failure of some kind?"

Is that really a problem thought? Won't it just begin cooling down and do no damage as long as we keep a nice safe and clean area around the reactor?

[Jinto]

I just want to post a few wiki pages on the topic of fusion, because what I read here is rather uhm... ah well...

http://en.wikipedia.org/wiki/Silicon-burning_process
http://en.wikipedia.org/wiki/Nuclear_fusion

and please compare those two:
http://en.wikipedia.org/wiki/ITER
http://en.wikipedia.org/wiki/National_Ignition_Facility

I just want to mention here, that both designs have not yet produced the amount of energy that is actually needed to sustain a fusion reaction in them.

For instance in the case of NIF the current goal is this:

Generating as much energy as the laser beams provide in operation.

Now what that really means is:

1) only the nominal output (power) of the lasers is taken into account. That you actually need a lot more energy to get that nominal output is simply neglected. (these lasers' degree of efficiency is far from 100%)

2) The energy that is generated in the process of fusion can be any form of radiation. And in fact when they calculate the output of the fusion reactor they count any form of radiation. There are two problems with this however, a) not every form of radiation is actually beneficial - some is just slowly destroying the reactor... and b) even if all the remaining radiation is transformed to heat (a useable form of radiation) it cannot be converted 1:1 into electrical energy which is the only useful type of energy to power those lasers (I doubt they work with heat).

So yeah, thats just my take on where this tehnology is actually standing now. I doubt I see commercially viable fusion reactor in my lifetime.

[Anh_Minh]

Originally Posted by Dextro

Is that really a problem thought? Won't it just begin cooling down and do no damage as long as we keep a nice safe and clean area around the reactor?

With the caveat that I actually know very little about nuclear reactors and that, as Jinto said, industrial applications are still the realm of Science Fiction anyway...

We use magnetic fields to contain the plasma. So what if something goes wrong and those fields fail? I don't know how much energy will be involved, but since we're talking about a power plant used to power our cities, it won't be small.

So, all the plasma is released in one catastrophic release of all its energy (aka explosion...). Even if it "only" kills everyone on the plant and ruin all the investment, I don't know if it's an acceptable risk. Depends on how likely the failure I described is, I suppose. It's not like we don't already have plants that can kill all its occupants if something goes wrong.

Oh, and they can probably see to it the plasm will vent into the atmosphere (some plants are built with thin roofs and thick walls precisely to send up most of the energy of an hypothetical big boom). But will that really be an improvement? I don't know.

[Dhomochevsky]

The plasma in those reactors is very thin.
Like I said above, it's almost a vacuum. So even if it is very hot, it does not carry that much energy in total, due to the lack of mass.
The plasma is surrounded by superconducting coils, which are cooled to very low temperatures.
If the plasma cvollides with those, it may lead to them getting destroyed due to losing the superconduction. But even for that I am not sure, it would depend on the actual construction plans? It would nto lead to any catastrophic event.

On the other hand, venting the plasma into the athmosphere is not such a good idea.
We are not doing pure hydrogen fusion here. That seems to be rather difficult.
We use radioactive isotopes instead. The result of the fusion process with those seems to be radioactive too.
So it should be kept inside the plant I guess.

[Anh_Minh]

Originally Posted by Dhomochevsky

The plasma in those reactors is very thin.
Like I said above, it's almost a vacuum. So even if it is very hot, it does not carry that much energy in total, due to the lack of mass.

But isn't that just today's experimental reactors? Won't it be different for our eventual industrial energy production reactors?

[Jinto]

They rather try to scale the reactor up to make it more efficient. If you want to increase the density of the plasma you would need to create stronger magnetic fields. The problem is the stronger you make the field, the more runaway electrons (electrons with relativistic speeds, means they "carry" lots of energy) will be occassionaly generated - those have the potential to damage the reactor.
If the field is approximately 2T almost no runaway electrons are generated. But over 2T the rate will increase exponentially to the growth of the field strength (doubling the field strength increases runaway electron generation by two orders of magnitudes).

So under low pressure conditions, it is not easy to increase the density of the plasma using stronger magnetic fields without causing side effects concerning the "stability" of the plasma.

This is only one of many problems. But lets not go too much into details, lets just say the subatomar "mechanics" are not so simple that you can simply scale the design by boosting the field strength. Of course they try to find corrective means to that behaviour, working with electromagnetic waves that harmonize the plasma. But again not going too much into details, thats a lot more complicated then controlling fission (where you simply use control rods).

Anyway, in contrast to fission reactors, the actual fuel inside a fusion reactor is always just enough to keep the fusion process running with the desired energy output. If you had more fuel inside the reactor it would cause the plasma to destabilize, which in turn makes the fusion process stop immediatly (its not like in fission reactors, where the fuel needs to "cool down" - also you will have the fuel for several month or years stored inside a fission reactor - and whats actually critical.. this fuel does not necessarily need a functioning reactor to sustain fission, that is why the reactor in Fukushima is still releasing lots of radioactive isotopes and must be cooled).

However, even when the plasma cannot cause structural damage to the reactor it can still render it useless in a case of malfunctioning. The tokamak reactors need to be extremely "clean". If plasma would react with the reactor casing it would basically contaminate the whole torus and the resulting mess would not allow for a restart of the reactor unless the contaminated parts are replaced (this could proof to be quite expensive). However, from a security point of view, thats the good thing about these reactors, they are inherently fail safe (means safe for the environment in a case of failure).

A fusion reactor is not a hydrogen bomb. The bomb requires an incredibly strong implosion, that causes a very high pressure and temperature to make the fusion sustain long enough to build up the energy that is released then. It would be neigh impossible to create reactor based on that principle of fusion.

[monsta666]

If you want to learn more about fusion energy and why it is unlikely to become commercially viable then read the article I have linked to below. It is written by the very person who wrote the fusion energy page on Wikipedia:

Why fusion will never happen

Originally Posted by Maury Markowitz

Nuclear reactions are pretty similar in the basic concept to chemical reactions, but this time you’re considering the nucleus of the atoms rather than their electrons. These are held together much more strongly than the electrons, so the energy scales are way higher. That means we need more energy to start a reaction, and get a lot more out when it's done.

In the case of a conventional nuclear plant we use atoms that are inherently unstable – if coal is somewhat unstable, uranium is downright crazy. Left to its own devices, uranium will periodically "decay" into other atoms, those will then also decay, and this continues until you end up with lead. When this happens it gives off lots of heat, although it's spread out over many, many years.

But another thing that happens during this reaction is that neutrons, one of the parts of the nucleus, go flying off. If one of them hits another uranium nucleus under just the right conditions, they cause that nucleus to decay right now. This is the basis of the "chain reaction" you've heard of.

Nuclear reactors are basically piles of uranium that are carefully positioned and controlled so that one of the neutrons coming out of a reaction causes another one to go. That perfect balance is called "criticality", it's the nuclear version of ignition.

Just like chemistry, nuclear reactions can also occur in "both directions", but in this case we don't produce more or less complex molecules, we produce heavier or lighter elements. I won't get into the physics here, but basically heavy elements want to break apart, and lighter elements want to clump together. It all has to do with the number of neutrons and protons in the nucleus. The breaking apart is fission, which we use all the time to generate power. The clumping together is called fusion, and that's why we're here today.

[Dhomochevsky]

The laser types are based on the hydrogen bomb concept, kinda.

The pulses are designed to cause a symetric shockwave through the target fuel ball, that causes the center to collapse under very high pressure and ignite the fusion.
So you could say every fuel capsule lighting up is a hydrogen bomb explosion (which makes sense: they built the whole Ignition facility to study bomb exlosions in the first place).

Of course these capsules are tiny and the slightest malfunction, off timing, or irregularity in the ball shape will result in nothing happening at all.
Those lasers on the other hand are scary. The amount of energy they pump into each pulse is mindboggling.

[Jinto]

Maury Markowitz is a little bit over dramatizing the lithium problem imo. Thorium reactors would use berylium and lithium as well, but as salt (lithium flouride and berylium flouride). There is no need to use pure lithium in the tokamak fusion reactor design, lithium flouride which is much more stable could be used instead.

Still, he is right with the berylium, this stuff will be nasty (and not just) in an accident.


That said, I want to add one thing about thorium reactors (fission) that I do not like. They use graphite as moderator (the stuff that made Chernobyl so much worse than Fukushima).

@Dhomochevsky,

okay admittedly this will generate similar conditions as in the case of hydrogen bombs. But its not quite the same and hard to scale. Its definitly the same in terms of how the process is designed, the conditions for fusion cannot be sustained. Repeated - like firing bullets from a gun - maybe, but it could hardly be used as a breeder then.

[Dr. Casey]

Originally Posted by monsta666

If you want to learn more about fusion energy and why it is unlikely to become commercially viable then read the article I have linked to below. It is written by the very person who wrote the fusion energy page on Wikipedia:

Why fusion will never happen

I tend to take people suggesting that something is impossible and will never happen with a grain of salt. "Such and such is impossible" essentially boils down to "I can't think of a way that this could ever be possible." That can be a disheartening testimony depending upon who gives it, and the points that are made are often very valid ones that accurately describe the problems which separate Point A from Point B, but there's seven billion people on this planet and no concrete time limit on figuring these things out. All that really matters is that one of them can figure out the solution.

These are the kinds of weeds that I try to stay away from, really. I'm sure technology will continue to increase quality of life for the human race just as it's always done up to this point, and that there's many great and wonderful things waiting for us in the future; whatever form the future will take and whatever speed it will arrive at, I'm content to just wait for it and believe in it without handwringing over the details concerning the 'how' or the 'when' too much.

[ganbaru]

UK plans new cyber force to boost strike ability
http://hosted.ap.org/dynamic/stories...09-29-12-57-31

NASA preparing to launch 3-D printer into space
http://hosted.ap.org/dynamic/stories...09-29-13-58-23

[AnimeFan188]

Chinese Super-Heavy Launcher Designs Exceed Saturn V:

"Chinese engineers are proposing a Moon rocket more powerful than the Saturn V
of the Apollo missions and matching the payload of NASA's planned Space Launch
System (SLS) Block 2, the unfunded launcher that would put the U.S. back into
super-heavy space lift.

Drawing up preliminary designs for the giant Long March 9 launcher, Chinese launch
vehicle builder CALT has studied configurations remarkably similar to those that
NASA considered in looking for the same capability: to lift 130 metric tons (287,000
lb.) to low Earth orbit (LEO). One of the two preferred Chinese proposals has a
similar configuration to the design finally adopted for SLS Block 2, though the takeoff
mass for both CALT concepts, 4,100-4,150 tons, is greater. On that measure, at
least, China wants to build the largest space launcher in history."

See:

http://www.aviationweek.com/Article....p22-620995.xml

[Ithekro]

But what will they launch with it? Or what won't they launch with it?