Discussion
mattnunn said:
Volume for volume your compost pile puts out 50 times more energy than the Sun.
Fact.
Nuclear fission is not all that.
The Sun is a fusion reaction (Hydrogen to Helium) not a fission reaction. You might need to do your sums again - and correct for all the energy from the sun in all directions - not just the energy that hits the Earth.Fact.
Nuclear fission is not all that.
Gene Vincent said:
mattnunn said:
Volume for volume your compost pile puts out 50 times more energy than the Sun.
Yes... I think your 'compost' might.
I think next time we send a probe towards the sun, we should include a message of the sort "Can't you try a bit harder you f
kwit? You might be putting out a fair bit of warmth by fusing hydrogen atoms at your core but come on, volume for volume, using the mass-energy equation, a pile of rotting cabbage knocks your measly effort into a cocked hat". Signed mattnunn.Or not.
Edited by MiseryStreak on Monday 16th July 16:26
The power density of the sun's not all that large, of the order of a few watts per cubic meter over the full volume if I remember correctly. Something like hundreds of watts per cubic meter near the core.
What relevance that has to the viability of a totally different type of fusion, under different conditions, I'm not sure.
What relevance that has to the viability of a totally different type of fusion, under different conditions, I'm not sure.
Gene Vincent said:
mc^2 = m M u__ G / R __u
This formula, which is correct, shows the entire energy of the Cosmos is... zero, zilch, nada, sweet fk-all! Energy is natures double-entry account book, nothing more.
A moth ate words. I thought that was a marvelous fate, This formula, which is correct, shows the entire energy of the Cosmos is... zero, zilch, nada, sweet f
k-all! Energy is natures double-entry account book, nothing more.that the worm, a thief in the dark, should eat
a man's words - a brilliant statement
and its foundation is strong. Not a whit the wiser
was he for having fattened himself on those words.
Chaucer (I think)
annodomini2 said:
ITER is a waste of money, IMHO.
They've been throwing money at Tokamak for the last 66 years and they're still not even close to break even, let alone the net energy generation requirements for a Tokamak.
Due to the nature of how a Tokamak works, it will need to generate 3x out to produce any power and probably 5x to make it commercially viable.
I'm not saying it's impossible, just doesn't appear to be cost effective.
You still have radiation problems and the resultant decommissioning issues, as with existing fission plant.
The plants need to be enormous to make any power.
There is still a nuclear weapon proliferation issue.
I think laser initiated fusion will turn out to be the way to go They've been throwing money at Tokamak for the last 66 years and they're still not even close to break even, let alone the net energy generation requirements for a Tokamak.
Due to the nature of how a Tokamak works, it will need to generate 3x out to produce any power and probably 5x to make it commercially viable.
I'm not saying it's impossible, just doesn't appear to be cost effective.
You still have radiation problems and the resultant decommissioning issues, as with existing fission plant.
The plants need to be enormous to make any power.
There is still a nuclear weapon proliferation issue.
The radiation issues are far less with fusion as you don't have any spent fuel to deal with. You can also turn the plant off at the flick of a switch - no chance of a meltdown!mattnunn said:
A moth ate words. I thought that was a marvelous fate,
that the worm, a thief in the dark, should eat
a man's words - a brilliant statement
and its foundation is strong. Not a whit the wiser
was he for having fattened himself on those words.
Chaucer (I think)
Another pearl of valuable wisdom added to the topic...that the worm, a thief in the dark, should eat
a man's words - a brilliant statement
and its foundation is strong. Not a whit the wiser
was he for having fattened himself on those words.
Chaucer (I think)
AJLintern said:
think laser initiated fusion will turn out to be the way to go The radiation issues are far less with fusion as you don't have any spent fuel to deal with. You can also turn the plant off at the flick of a switch - no chance of a meltdown!
NIF is an even bigger pipe dream than Tokamak, lasers are incredibly inefficient (about 14% in-out typically). The radiation issues are far less with fusion as you don't have any spent fuel to deal with. You can also turn the plant off at the flick of a switch - no chance of a meltdown!They state themselves, the current machine has no interest in creating electrical energy.
It also intends to operate with D-T fuel, which it's reaction produces huge number of Neutrons.
This is where the decommissioning and proliferation issues come from:
A: The reactor, building and site remain radioactive for many years after the system is rendered inactive, yes there is no Plutonium and other nasties with huge half lives.
B: The high energy Neutrons can be used to create fissile material. It's not a simple process, but it can be done.
Well NIF is a proof of principle machine (along with doing stuff for nuke testing... no problem with funding there then!) The lasers it uses are old tech flash tube amplified systems. Any laser fusion power plant would have to be powered by high rep rate diode systems - currently in development...
The energetic neutrons are where you get your power from - they are absorbed by the surrounding lithium blanket (some of which is converted into tritium for more fuel) which is then pumped through a heat exchanger to produce steam to drive turbines etc.
The LHC will contain lots of hot, irradiated material - so not much different when it comes to decommissioning.
The energetic neutrons are where you get your power from - they are absorbed by the surrounding lithium blanket (some of which is converted into tritium for more fuel) which is then pumped through a heat exchanger to produce steam to drive turbines etc.
The LHC will contain lots of hot, irradiated material - so not much different when it comes to decommissioning.
What do you envisage as the main issues preventing it from being a practical proposition? The basic physics or the technical challenges? I think the major one which I can't get my head round is: how do you fire a 2mm cryogenically frozen fuel pellet into a reactor chamber and target it accurately enough to zap it with multiple lasers... and do that 10 times per second?! 
I don't think the practical physics are a problem. There's a long way to go with the laser efficiency and recharge rates though. Plus, like you say, rapidly positioning lots of pellets very accurately in a fairly harsh environment isn't exactly trivial. The big issues with radiation damage from the fast neuts are also there, just like in the tokamaks, once you start hitting decent sustained power outputs as well.
hairykrishna said:
I don't think the practical physics are a problem. There's a long way to go with the laser efficiency and recharge rates though. Plus, like you say, rapidly positioning lots of pellets very accurately in a fairly harsh environment isn't exactly trivial. The big issues with radiation damage from the fast neuts are also there, just like in the tokamaks, once you start hitting decent sustained power outputs as well.
So, compost pile reactors it is then?The greens were right all along...
How apt:
http://www.theregister.co.uk/2012/07/16/nif_passes...
Or if you can bear it:
http://www.dailymail.co.uk/sciencetech/article-217...
What were you saying Hairy?
http://www.theregister.co.uk/2012/07/16/nif_passes...
Or if you can bear it:
http://www.dailymail.co.uk/sciencetech/article-217...
What were you saying Hairy?
MiseryStreak said:
How apt:
http://www.theregister.co.uk/2012/07/16/nif_passes...
Or if you can bear it:
http://www.dailymail.co.uk/sciencetech/article-217...
What were you saying Hairy?
Laser people always love to bandy around enormous power figures because they look great to people who haven't thought about how power is calculated - like the Mail. I've seen a smallish (i.e. smaller than a car) laser which could output a petawatt, roughly a thousand times that. Their pulse energy is 1.85MJ or about a third of a kWh. Spectacular that they can deliver that in a tiny time interval but I bet the recharge time is rubbish. Power output and density calculations aren't always that useful on their own, as the compost vs the sun example shows.http://www.theregister.co.uk/2012/07/16/nif_passes...
Or if you can bear it:
http://www.dailymail.co.uk/sciencetech/article-217...
What were you saying Hairy?
ICF has lots of fun physics but I just don't see it as a future power generation technology. Tokamaks, for all their flaws, just seem more likely to me. Somewhat out of my field though so it's a gut feeling more than mega informed comment. Maybe lasers have leaped forward in development since I last had a good look at it.
hairykrishna said:
I've seen a smallish (i.e. smaller than a car) laser which could output a petawatt, roughly a thousand times that.
What are you talking about? The article I linked to says it's the most powerful laser ever tested, setting a new record and it's power output is 500 Terawatts, half a Petawatt.What is your sub car sized laser that is twice as powerful (not quite 'roughly a thousand times that' by any stretch) as the NIF one?
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