nuclear fusion

Originally posted by FabianFnas
Then I owe sonhous an apology, he was more right than I thought. the difference between million of years and a mere 20.000 of years is not that much 🙂 (not ironic, I work with astronomy on occations)

Nothing more than heat, well yes, but you have to make the heat useful too. Our old nuclear plant in Barsebäck in southern Sweden (now obsolete) warmed u So the 20.000 year light bulb pehraps dont have to work more than a thousand years after all...

I think you are wrong about the % of heat turned to usable energy. It may be as high as 40 %. If you compare a coal fired plant, it also produces raw heat and that heat is channeled to heat water for a steam powered turbine. The fusion plant would use the same technology, just ordinary steam generator stuff, nothing fancy there. So if Matt is right, 1 Kg would power a 100 watt bulb (obviously not a 100 watt tv set🙂 for 8,000 years. To reverse it, 1 watt for 800,000 years or one megawatt for 0.8 year or one Gw for 0.0008 year or about 6 hours. Times 4 for 24 hours and we come up with 4 Kg/day/Gwhr. or about 1500 Kg/year/Gwhr.
I searched out how much energy you get from coal, one 'short ton'=2E10 joules, 1 short ton is close enough to 1000Kg for this discussion.
So 1000Kg=~20Gw/seconds. Divide by 20 gives you 50 Kg for 1Gw/second times~30E6 seconds/year =1.5 Billion Kg/year for a 1Gw plant. Hmm, lets see, which one seems better, 1,500 Kg/year or 1.5 BILLION kg/yr.(and of course when you cook that much coal, it turns into about three times that amount of CO2, so the coal plant generates about 6 billion Kg of CO2 per year per Gw.

Of course that is only for one 1GW plant. The world uses something like 10 TERAwatts per year so you would need about 10,000 of such coal plants to supply the world, or 15 TRILLION Kg of coal/year and in 100 years 1.5 Quadrillion tons. So a fusion plant would take (if our #'s are right, 15,000,000 Kg/year for 10 Terawatt/years or 1.5 billion Kg for 10 Tw for 100 years. ( that would be 10,000 such fusion plants running 1Gw each for one hundred years)

Originally posted by AThousandYoung
Fusion can be done with any element lighter than iron. You could use helium in theory, and it's not flammable. Hydrogen is the easiest one to fuse though I think.

Easiest to fuse, but also dangerously flammable. Helium would be a lot better, and if it were helium we were working with, I wouldn't be so skeptical about safety concerning fusion plants. But hydrogen powers the Sun, blew up the Hindenburg, destroyed the Bikini Atoll in the Marshall Islands, was calculated as having enough energy to destroy the world, and created the US President's "Red Button."

And it was also responsible for the San Francisco earthquakes of 1906 and 1989, the Chicago fire, the Jamestown flood, the Pearl Harbor bombing, 9/11, the 2004 South Asia tsunami, the 79 CE Vesuvius eruption that destroyed Pompeii and Herculaneum, and Richard Nixon.

Originally posted by scherzo
Easiest to fuse, but also dangerously flammable. Helium would be a lot better, and if it were helium we were working with, I wouldn't be so skeptical about safety concerning fusion plants. But hydrogen powers the Sun, blew up the Hindenburg, destroyed the Bikini Atoll in the Marshall Islands, was calculated as having enough energy to destroy the world, and c nami, the 79 CE Vesuvius eruption that destroyed Pompeii and Herculaneum, and Richard Nixon.

…Easiest to fuse, but also dangerously flammable….

Hydrogen is only inflammable in the presence of oxygen. There would be no oxygen in a fusion reactor.

…Helium would be a lot better …

Unfortunately probably not. Helium nuclei require much higher energies to get them to fuse than, say deuterium nuclei. This would make it much harder to make a practical fusion reactor that uses helium.

…But hydrogen powers the Sun, ……. destroyed the Bikini Atoll in the Marshall Islands, was calculated as having enough energy to destroy the world, and created the US President's "Red Button." …

All these things have runaway nuclear chain reactions that fuse a large amount of hydrogen all at once. There would be only a small amount of hydrogen in a fusion reactor at any one time -too small an amount to cause this kind of runaway fusion reaction.

Also, the pressures inside the fusion reactor would probably be far to low to allow such a thing because, remember, the ionised hydrogen has to be confined in a vacuum using magnetic fields.

If, somehow, too much hydrogen was let in the fusion reactor all in one go by accident, the magnetic fields wouldn’t be able to contain all that hydrogen to stop the hydrogen nuclei colliding with the inner surface of the fusion reactor’s walls and this would slow down the nuclei thus preventing them having sufficient kinetic energy to fuse. This will simply stop the fusion reaction. There would be no credible chance that the fusion reactor could blow up by “going nuclear”.

…And it was also responsible for the San Francisco earthquakes of 1906 and 1989, the Chicago fire, the Jamestown flood, the Pearl Harbor bombing, 9/11, the 2004 South Asia tsunami, the 79 CE Vesuvius eruption that destroyed Pompeii and Herculaneum, and Richard Nixon….

How was hydrogen responsible for all these events?

Slight aside... Hydrogen gets very bad press as being exceedingly flammable and explosive, with regards to being used as a fuel (for green cars/aeroplanes ect). And this is to some extent true, Hydrogen does react exceedingly exothermically with oxygen, but so does petrol. and unlike petrol which when it leaks pools on the ground whilst it's heavier than air fumes refuse to blow away, hydrogen goes up and defuses rapidly. this means that on the whole it is no more dangerous than petrol, and in some circumstances less so.

Now in the context of nuclear fusion, as has been stated the amounts of hydrogen used are pretty small, (as a comparison a chem' teacher I had would often fill balloons with hydrogen and then get us to explode them with a burning splint on a stick, now banned by health and safety, and in a lesson we could easily get through more hydrogen than would be in the reactor at anyone time,) the fact that to get fusion to work the hydrogen needs to be heated to several million kelvin, MUCH hotter than you could possibly make it with chemical reactions (say a couple of thousand kelvin) and you see that using hydrogen as a nuclear fuel is not dangerous (at least not from any chemical reaction involving the hydrogen). In fact as (basically) the energy required to initiate fusion increases as you increase the proton number (element size) you have to make anything bigger than hydrogen much hotter to get it to fuse (whilst getting less energy back out) making hydrogen isotopes the safest (as well as most practical and efficient) nuclei to fuse.

It should also be stated that there are several different methods of initiating fusion, (two main ones, magnetic confinement and pulse laser compression) with different energy requirements/efficiencies and power outputs.

Originally posted by Andrew Hamilton
[b]…Easiest to fuse, but also dangerously flammable….

Hydrogen is only inflammable in the presence of oxygen. There would be no oxygen in a fusion reactor.

…Helium would be a lot better …

Unfortunately probably not. Helium nuclei require much higher energies to get them to fuse than, say deuterium nuclei. This would make it much h ...[text shortened]... nd Herculaneum, and Richard Nixon….[/b]

How was hydrogen responsible for all these events?[/b]

Hydrogen is only inflammable in the presence of oxygen. There would be no oxygen in a fusion reactor.

All reactors have trace elements. I think Chernobyl and Three-Mile Island were vacuums as well.

Unfortunately probably not. Helium nuclei require much higher energies to get them to fuse than, say deuterium nuclei. This would make it much harder to make a practical fusion reactor that uses helium.

I apologize. I should have specified more. I was referring to safety, not convenience.

All these things have runaway nuclear chain reactions that fuse a large amount of hydrogen all at once. There would be only a small amount of hydrogen in a fusion reactor at any one time -too small an amount to cause this kind of runaway fusion reaction.

Also, the pressures inside the fusion reactor would probably be far to low to allow such a thing because, remember, the ionised hydrogen has to be confined in a vacuum using magnetic fields.

Again, see other nuclear incidents in the past.

How was hydrogen responsible for all these events?

It wasn't. I was over-exaggerating the properties of dangerous nuclear reactions.

Oh, and also the Spanish Inquisition. And the Holocaust.

Originally posted by scherzo
[b]Hydrogen is only inflammable in the presence of oxygen. There would be no oxygen in a fusion reactor.

All reactors have trace elements. I think Chernobyl and Three-Mile Island were vacuums as well.

Unfortunately probably not. Helium nuclei require much higher energies to get them to fuse than, say deuterium nuclei. This would make it much har ...[text shortened]... ies of dangerous nuclear reactions.

Oh, and also the Spanish Inquisition. And the Holocaust.

Dude. Runaway reactions are impossible in fusion reactors for one simple reason: In fission reactors, ALL the fuel to run is inside the machine at the same time. So we have Chernoble, 2 1/2 mile island🙂 and such.
In a fusion reactor, for instance, the inertial confinement reactor with super powerful laser beams coming down hard at the exact same place hits a target the size of a nickle. So suppose a future reactor actually is built that generates 20 times the energy it takes to initiate fusion that way. It is all a carefully orchestrated series of events that end up with one blast after another but each one does not have the power to blow ANYTHING up. To generate usable energy, the reactor has to have many of these pellets zapped every minute, so suppose something like a hundred such pellets fall into the firing zone at once, only one can ignite but they cannot ignite the others, there is not enough energy in that one blast to do that so there can be no runaway reaction, at worse it just shuts down.

Take magnetic confinement, there is also only a tiny amount of fusable material in the reactor at any one time, WAY less than the total energy available in a fission reactor because like I said, ALL the fuel for years of operation is inside the beast. Not even close with fusion, if something happens, a bomb, whatever, the delicate conditions required to initiate fusion is interrupted and it just shuts down. That is not to say their won't be radioactive material left but what radioactivity coming from a fusion reactor has a half life of 12 years at most, a few days usually. There are no long term radioactives like a fission reactor with all the heavy elements which can stay radioactive for thousands of years. All in all the fusion reactor is a million times more environmentally friendly than any fission reactor.

Originally posted by scherzo
Hydrogen is only inflammable in the presence of oxygen. There would be no oxygen in a fusion reactor.

All reactors have trace elements. I think Chernobyl and Three-Mile Island were vacuums as well.

Unfortunately probably not. Helium nuclei require much higher energies to get them to fuse than, say deuterium nuclei. This would make it much har ies of dangerous nuclear reactions.

Oh, and also the Spanish Inquisition. And the Holocaust.

scherzo is only joking. This is not about nuclear plants, nor fission vs fuson reactors and their function.

'Scherzo' is italian for 'Joker'. And this is what the postings of his are all about.

Originally posted by FabianFnas
scherzo is only joking. This is not about nuclear plants, nor fission vs fuson reactors and their function.

'Scherzo' is italian for 'Joker'. And this is what the postings of his are all about.

First of all, "scherzo" is Italian for "joke," not "joker." I chose it for its musical affiliation.

Fusion plants are nuclear plants with potentially fatal flaws. Most of what I say has basis in fact, at least in the Debates forum.

Originally posted by scherzo
[b]Hydrogen is only inflammable in the presence of oxygen. There would be no oxygen in a fusion reactor.

All reactors have trace elements. I think Chernobyl and Three-Mile Island were vacuums as well.

Unfortunately probably not. Helium nuclei require much higher energies to get them to fuse than, say deuterium nuclei. This would make it much har ...[text shortened]... of dangerous nuclear reactions.

Oh, and also the Spanish Inquisition. And the Holocaust.[/b]

…All reactors have trace elements….

A “trace” of oxygen in a fusion reactor would not allow enough energy release to cause an explosion because it would be just a “trace”. Remember that the amount of energy released from the combustion of a fuel depends not only on the amount of fuel but the available quantity of oxygen. If there is only a “trace” of oxygen then that “trace” of oxygen can only oxidise a “trace” of the hydrogen fuel thus only a tiny amount of the hydrogen fuel will be combusted and thus only a tiny amount of energy through combustion would be released.

…I think Chernobyl and Three-Mile Island were vacuums as well. ….

I don’t think so. Those reactors were fission and not fusion reactors. A vacuum wouldn’t be necessary to run a fission nuclear reactor.

…Again, see other nuclear incidents in the past. ….

But all those accidents involve fission nuclear reactors and not fusion nuclear reactors. A fission nuclear reactor works in a very different way from a fusion nuclear reactor with vastly more potential for a serious accident because there is normally more than enough nuclear fuel in its core to cause a meltdown or a big explosion if for some reason the temperature control malfunctioned as it did in Chernobyl. This is not the case for a fusion nuclear reactor as there wouldn’t be enough nuclear fuel in its core at any one time. Also, a fission nuclear reactor produces radioactive waste which could potentially leak out and cause an accident while a fusion nuclear reactor would produce virtually no radioactive waste.

I don’t think safety is the main problem with fusion power; it is its practical development. It is really just a mater of how expensive and how long would it take to fully developed practical and economic fusion power and would we be better off, at least in the short term, to concentrate only on fully developing practical and economic solar and wind power first which I suspect would be cheaper and quicker to develop?
-but I am not completely certain of this because I do not know how to calculate this to make a rational comparison.

Originally posted by scherzo
Fusion plants are nuclear plants with potentially fatal flaws. Most of what I say has basis in fact, at least in the Debates forum.

But you are just guessing around, you don't have any solid facts. This is science, and science is based upon facts, you know.

Originally posted by FabianFnas
But you are just guessing around, you don't have any solid facts. This is science, and science is based upon facts, you know.

Of course I know. Do you think I just randomly insert whatever I like into forums? That's for the Creationists. And I'm no Creationist.

Fusion destroyed the Marshall Islands and powers the Sun. That's pretty formidable energy right there. How can anything that gives us our livelihood on Earth not be powerful? No, of course I'm not talking about some God, I'm talking about fusion and the Sun.

Originally posted by scherzo
Of course I know. Do you think I just randomly insert whatever I like into forums? That's for the Creationists. And I'm no Creationist.

Fusion destroyed the Marshall Islands and powers the Sun. That's pretty formidable energy right there. How can anything that gives us our livelihood on Earth not be powerful? No, of course I'm not talking about some God, I'm talking about fusion and the Sun.

So why trying to tell anyone that fusion is an unstable process, when you obviously don't know much about the subject? Why scherz around?

Originally posted by scherzo
Of course I know. Do you think I just randomly insert whatever I like into forums? That's for the Creationists. And I'm no Creationist.

Fusion destroyed the Marshall Islands and powers the Sun. That's pretty formidable energy right there. How can anything that gives us our livelihood on Earth not be powerful? No, of course I'm not talking about some God, I'm talking about fusion and the Sun.

You seem not to be able to grasp the concept of the difference between hydrogen bombs as uncontrolled reactions and the highly controlled reactions involving minute amounts of deuterium in any one experiment or when it finally bears fruit in a real reactor. There is no comparison, a working reactor CANNOT blow up, a fission reactor CAN and HAS blown up because, and please read this line carefully: a fission reactor has ALL its fuel inside for the whole run of the reactor, years of energy in one place.
You should be directing your tirades against this known threat, as the whole world saw in 2 1/2 mile island and Chernoble. NOTHING like that could EVER happen with fusion reactors for the simple reason that only a tiny amount of fuel is present at one time. PLEASE try to understand that concept. Direct your angst at fission, it's the real threat.

Fusion Reactors are safe, as opposed to fission reactors, which are inherently unstable, and are thus only mostly safe, when built right, and well maintained. Let me explain why...


As a contrast, I will tell you how a Fission reactor basicaly works.
certain isotopes of certain elements are naturally unstable, each atom can at any given moment spontainiously disintegrate into a set of smaller components, releasing energy. A nuclear battery (as found on certain spacecraft) simply capturs this energy (from a tiny radioactive source, usually Plutonium). However it was discovered around the begining of the last century that you can induce an unstable atom to disintigrate (decay) if you bombard it with a specific type of radiation, and that further some unstable atoms emit when they decay just the kind of radiation to make other atoms of the same type decay as well, emitting more of this radiation which induces more atoms to decay, emitting more radiation..... et all, you have a nuclear 'Chain reaction'.
(For uranium isotope 235 the radiation is Neutron radiation)
Now this is where the critical mass bit comes in....
Nuclei of atoms (the core of the atom where neutrons and protons, known collectively as nucleons live) are really small, even compared to the size of atoms, if the nuclei were the size of a football and you held it up in the middle of a airport, the outer electrons would be wizzing round the perimiter fence. This means that a neutral particle like a neutron can wizz through the empty space inside atoms without hitting anything, which is why you can find uranium in the ground at all, and why it didn't just all decay in a huge bang shortly after being created. The critical mass is thus simply the amount needed in one place so that slightly more neutrons colide with other uranium 235 nuclei than leave the reaction (and hit the radiation sheilding).

The reactor then works something like this:
you build a pile of uranium 235 (enriched uranium) inside a containment vessel, and with controll rods (which absorb neutrons) fully lowered into the pile. then some coolant is added, (this is what extracts the heat which is used to turn terbines and make electricity)
Then you pull out the controll rods, this increses the number of neutrons inside the reactor, wich increases the reaction rate, further increasing the neutron number. The reactor heats up, as the reactor reaches the desired temperature the controll rods are partially lowered back in, and a balancing act ensues to keep the reaction rate constant at the desiered level.
Catostrophic falior can occur because the reaction is self sustaining, if you pull your controll rods out to far and cant put them back in (chernoble) then the reaction runs away, and the whole thing catches fire (and caused a GAS/STEAM explosion, which threw radioactive waste all over the place, NOT a nuclear explosion in the way a nuclear bomb works).

However, A fusion reactor is different:
The fuel for a fusion reactor is mostly non radioactive (and in reactors that use tritium, a radioactive isotope of hydrogen it us usually manufactured inside the reactor core as it has a short half life, and thus can't be stored very long).
To make it fuse together requires lots of energy and i mean LOTS. In the sun it takes the entire mass of the sun crushing down on its core to sustain the fusion rate. The temperature required in a tokomak reactor (the most common/sucessfull to date design of reactor) is in the millions of kelvin. to make if fuse giant electromagnets and microwave generators blast the plasma till it raches the desired temp and pressure at wich point it starts fusing, if at any point any of the aperatus fails, you seace to compress/heat the plasma, you loose containment, and the fusion stops... instantly. The worst you can do is dmg the iner coating of your reactor needing shutdown and repairs.

However if you insist on imagining doom where none is possible... the ractor has very little radioactive material in it (radioactive as ordinaery matter can become radioactive after prolonged radiation bombardment) and what radioactive material there is has a short halflife, meaning that any radioactive release would be very much shorter lived, and there is much less cleanup needed after reactor decomission. So even if you were to blow the thing up (you would need your own explosives) there wouldn't be any seriouse contamination, all of which would be cleaned up in pretty short order.
It is in other words safe. and if you persist on worrying about hydrogen, go see how much your local highschool chem or physics lab has sotored in gas canistors lying about the place, I can pretty much garentee that any school worht it's salt will have more lying around than you would have inside the reactor.

Oh and sidenote, no fission reactor has an internal vacuum. It would overheat and explode, it requires coolant at all times, most reactor faliors have in fact been coollant faliors.