What I don’t understand about Nuclear Fusion

[ChrisGreaves]

CNN>>>For the first time ever, US scientists at the National Ignition Facility at the Lawrence Livermore National Laboratory in California successfully produced a nuclear fusion reaction resulting in a net energy gain, a source familiar with the project confirmed to CNN.

I feel that I have been reading about nuclear fusion breakthroughs for the past twenty years – am I alone in feeling this?

CNN>>>Scientists across the globe have been inching toward the breakthrough; in February, UK scientists announced they had more than doubled the previous record for generating and sustaining nuclear fusion.

This paragraph – “doubled” – suggest twice the previous instance, so this is not the first occurrence, No?

I have read:-

CNN>>>The result of the experiment is a massive step in a decades long quest to unleash an infinite source of clean energy that could help end dependence on fossil fuels. Researchers have for decades attempted to recreate nuclear fusion – replicating the fusion that powers the sun.

It seems to me that “an infinite source of clean energy” poses just as great a threat as does fossil-fuel burning. In other words, what we really need is a reduction in our appetite for energy, not a new way to grow “fat” by consuming free energy.

The bottom line is that regardless of the source of energy, it all resolves into heat energy.
Entropy! Looking forward to meeting you even sooner than we had first thought.

(signed) “Puzzled” of Bonavista

[HansV]

I feel that I have been reading about nuclear fusion breakthroughs for the past twenty years – am I alone in feeling this?

Only twenty years? We've been on the brink of a breakthrough in nuclear fusion for sixty or seventy years! Commercial application is always ten years away...

[John Gray]

I think the real problem with nuclear fusion is that it is quite difficult to achieve, unless you have a spare sun lying about...

[ChrisGreaves]

... We've been on the brink of a breakthrough in nuclear fusion for sixty or seventy years! Commercial application is always ten years away...

Thanks Hans. I was not keeping abreast of nuclear physics in my childhood years, probably not until the mid-1970s, if then. But I do have the feeling that it all gets revved-up every decade or so.
Cheers, Chris

[ChrisGreaves]

I think the real problem with nuclear fusion is that it is quite difficult to achieve, unless you have a spare sun lying about...

I am inclined to agree. That said, today on a daily basis we use technology that was not even a dream "Back then".
I have confidence in technology and can believe that, one day, we will have radiation-free nuclear technology.

For the present I would be happy to have a mode of living that was fuelled by electricity, then the true source of energy could be adapted without changing individual households or industries.
Cheers, Chris

[macropod]

Nuclear physicists working in the field have been claiming they're almost there for 50 years now... I knew such a one way back then.

[Jay Freedman]

I think the real problem with nuclear fusion is that it is quite difficult to achieve, unless you have a spare sun lying about...

Precisely.

The sun (and every star) manages to sustain the conditions necessary for fusion by the gravity provided by its mass. Gravity keeps the hydrogen/helium plasma contained, and the resulting density raises the temperature above the threshold needed to initialize fusion.

Lacking that mass by a small margin physicists attempt to contain and heat plasma in extremely strong magnetic fields. That works, but so far only for a fraction of a second at a time. It takes so much energy to heat the plasma and to create the magnetic containment that the net energy output has been negative until now.

The mention of "doubling" the previous record probably refers to the length of time that fusion could be sustained, not the amount of energy it produced.

[StuartR]

When I was at school in the 1960s, fusion reactors were 10 to 15 years away. We hear the same claims every few years, and they are still 10 to 15 years away now.

[BobH]

CNN>>>For the first time ever, US scientists at the National Ignition Facility at the Lawrence Livermore National Laboratory in California successfully produced a nuclear fusion reaction resulting in a net energy gain, a source familiar with the project confirmed to CNN.
. . .

IIRC the little I learned in high school physics class in the 1950s, the law of conservation of energy states that energy can neither be created nor be destroyed. Although, it may be transformed from one form to another. If my recall is right, I need an explanation of how the reaction created a net energy gain.

[HansV]

In nuclear fusion, two nuclei merge to form a larger nucleus. But the mass of the new nucleus is less than the sum of the masses of the individual nuclei. The difference in mass is converted into energy.

[GeoffW]

The problem with nuclear fusion isn't achieving it. That part's easy, hence the hydrogen bomb.

The difficult part is controlling and harnessing it.

[John Gray]

Err, surely the hydrogen bomb is an example of nuclear fission, not fusion?

[HansV]

Err, no. Uranium / plutonium bombs use nuclear fission. Hydrogen bombs use nuclear fusion - see Thermonuclear weapon.

[StuartR]

Err, surely the hydrogen bomb is an example of nuclear fission, not fusion?

Hydrogen is the smallest nucleus. Fission is a large nucleus splitting to make smaller ones. Like when uranium breaks down in an atom bomb. A hydrogen bomb fuses nuclei to make bigger ones.

[GeoffW]

As distinct from nuclear phission, which is where somebody tries to get into your nucleus to get passwords of your bank account.

[stuck]

When I was at school in the 1960s, fusion reactors were 10 to 15 years away. We hear the same claims every few years, and they are still 10 to 15 years away now.

When I was at school in the 1970s, fusion reactors were 10 to 15 years away. We hear the same claims every few years, and they are still 10 to 15 years away now.

Ken

[StuartR]

[ChrisGreaves]

... the law of conservation of energy states that energy can neither be created nor be destroyed. Although, it may be transformed from one form to another.

Speaking as one classical physicist to another: Spot On! This teaching was given to all of us who studied Newtonian Mechanics in high school, and the viewpoint still serves us well today for those things which we see and use as humans. Only as we delve deeper into the strange worlds that we cannot see (with the unaided eye) do we need to know about what goes on under-the-hood with atoms.

I think the recent Artemis fly-by could have been controlled solely with Newtons laws, but too I understand that GPS positioning data needs to take into account Quantum-wossit so that it can achieve accuracy to within a few feet.

If my recall is right, I need an explanation of how the reaction created a net energy gain.

I usually explain this away by asking "What is your system?"
If I consider my body as a System, then eating a chunk of cheese makes for a net energy gain, but if I consider the isle of Newfoundland to be the System, then there is no change in energy (as far as me eating a chunk of cheese goes). So a "net energy gain" in the report will be "net" to whatever the scientists regard as their "System"; and that, I suspect, is dependant on the reporter who has a B.A. but not a B.Sc.

Cheers, Chris

[ChrisGreaves]

Nuclear physicists working in the field have been claiming they're almost there for 50 years now... I knew such a one way back then.

So in reality it's a race between Nuclear Physicists and the Voice Recognition guys?
Cheers, Chris

[ChrisGreaves]

The mention of "doubling" the previous record probably refers to the length of time that fusion could be sustained, not the amount of energy it produced.

Hi Jay; I may have tripped myself up here, but wouldn't an increase in the period of fusion lead directly (although maybe not in a linear fashion) to an increase in the amount of energy produced? I am thinking along the lines of "increase the period from five seconds to ten seconds and you have approximately doubled the amount of energy produced"?
Cheers, Chris