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Is nuclear fission safe?

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ThePaladin
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23 Jul 2013, 9:04 am

ruveyn wrote:
eric76 wrote:

My question was about the use of the laser to induce fission in a thorium reactor where there is no chain reaction as in conventional fission reactors.

From the article I linked earlier:
Quote:
Professor Robert Cywinksi from Huddersfield University said thorium must be bombarded with neutrons to drive the fission process. “There is no chain reaction. Fission dies the moment you switch off the photon beam. There are not enough neutrons for it continue of its own accord,” he said.


Speaking of fusion, I've stood within four or five feet of a small tokamak while it was being used to create a fusion reaction. It was quite noisy. After the first one, I kept a greater distance from the others during the demonstrations. That was in 1971. Do they still use tokamaks?


Lasers are capable of getting a small amount of hydrogen to fuse. The problem is deriving enough energy to keep the laser fusing more hydrogen. So far no one has been able to do this.

As I said, nuclear fusion has been accomplished by hot plasma and by lasers but the problem of sustaining the reaction is still unsolved.

ruveyn


Not quite right. The problem with inertial confinement fusion is not deriving the energy from the laser - we already have lasers intense enough to do the job. You direct a laser beam into a cavity called a hohlraum which results in a universal microbombardment of microwaves reemitted from the hohlraum.

ICF is restricted, in fact, by our lack of understanding of the fluid dynamics within the contracting capsule. ICF relies on a number of processes involving the creation of a hot spot in the centre of the deuterium fluid capsule, but that hotspot has to be created at the right time. Otherwise what happens is the capsule expands outward again against the laser and for lack of a better term, starts to wriggle about under the pressure. The hotspot then spreads into a star or a cross shaped formation and then collapses and explodes.

Instead, what we need is a collapse which is suddenly accelerated at which point the hot spot heats to full on fusion and the capsule is violently and virtually instantaneously consumed from the inside out in a fusion reaction.



ThePaladin
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23 Jul 2013, 9:05 am

ruveyn wrote:
eric76 wrote:

I thought the problem was in trying to contain the plasma so that they could maintain fusion.

.


Tokomags have contained plasma. But the plasma cools down after fusion so more energy is needed to sustain it. Magnetic confinement cannot be maintained with current technology.

ruvein


It's instabilities within the plasma that cause this effect. You find the plasma starts to oscillate within the containment as it heats up and more particles undergo fusion. ITER will maintain a plasma environment capable of running a fusion reaction with little difficulty.

eric76 wrote:

By the way, I asked one solid state physicist in the late 1970s about nuclear fusion. He responded that there were much more interesting problems that actually had a chance of being solved in our lifetime. He didn't think that controlled fusion is going to be viable for a very long time. I'm starting to think that he was correct. In 1971 they were saying it was thirty years away. Forty two years later, it's still thirty years away.


Solid state physicists just say that to get more funding.



ruveyn
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23 Jul 2013, 4:29 pm

ThePaladin wrote:

Instead, what we need is a collapse which is suddenly accelerated at which point the hot spot heats to full on fusion and the capsule is violently and virtually instantaneously consumed from the inside out in a fusion reaction.


Thirty years from now the problem will still be solvable thirty years in the future.

If a person held his breath until we finally got sustained controlled nuclear fusion here on Earth he would turn blue and die.

ruveyn



ThePaladin
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29 Jul 2013, 4:41 am

ruveyn wrote:
ThePaladin wrote:

Instead, what we need is a collapse which is suddenly accelerated at which point the hot spot heats to full on fusion and the capsule is violently and virtually instantaneously consumed from the inside out in a fusion reaction.


Thirty years from now the problem will still be solvable thirty years in the future.

If a person held his breath until we finally got sustained controlled nuclear fusion here on Earth he would turn blue and die.

ruveyn


ITER will achieve ignition in its first year. NIF within five years.

After that it's just a matter of scale.



ruveyn
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29 Jul 2013, 10:01 am

ThePaladin wrote:
ruveyn wrote:
ThePaladin wrote:

Instead, what we need is a collapse which is suddenly accelerated at which point the hot spot heats to full on fusion and the capsule is violently and virtually instantaneously consumed from the inside out in a fusion reaction.


Thirty years from now the problem will still be solvable thirty years in the future.

If a person held his breath until we finally got sustained controlled nuclear fusion here on Earth he would turn blue and die.

ruveyn


ITER will achieve ignition in its first year. NIF within five years.

After that it's just a matter of scale.


Yeah. Maybe 30 years from now. So far ITER has produced bupkis.

Believed when seen and not a second before.

ruveyn



eric76
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28 Jan 2015, 2:53 am

ruveyn wrote:
Question14 wrote:
Don't really know as much as i would like about fusion.
What are the results of a fusion reactor? in other words is there any waste?


No waste. But no one has ever produced a controlled fusion reaction with net power output.

Fusion has been predicted 30 years in the future for the last 55 years. A hundred years from now it will still be 30 years in the future.

ruveyn


A few months ago, Lockheed was claiming that they expect to have a working prototype within something like one to five years.

It makes me wonder if they really have the expertise that they need to tackle the job. I'll believe their claims when they have it working, not before then.