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First off, I'm probably missing an important part of the argument regarding nuclear fusion.

What I think I know about it;

Nuclear fusion (using heat instead of gravity) is taking Deuterium and Tritium(sp?) and heating them until they fuse. This causes a release of energy that is used to generate heat for the mundane use of steam power generation.

My issues; I know that deuterium is a very rare isotope of hydrogen. However class one stars aren't made from deuterium. That means it's possible; however unlikely, that should fusion power become feasible that hydrogen-0 will eventually be fusible.

Water is made from hydrogen and oxygen. Fusion turns hydrogen into helium. Using helium for fusion is infinitely more difficult than using hydrogen. If we start start harvesting hydrogen from water then more oxygen would be release into atmosphere which would drive world temperatures down, but not as fast as water removal would lead to super heating in the thinner crust of the ocean; see Venus. Losing the oceans are a consequence all their own and I don't feel the need to go into detail of how bad a 1% oceanic loss would be on ecological systems as well as future habitation of the Human home world.

I haven't seen any argument against nuclear fusion outside of conspiracy theory regarding aliens and some god awful eldritch abominations. Read as, no one seems concerned about this.

I'm assuming that my thought process on this subject must be flawed since I would assume the end of the world would be higher on the priority list than clean energy. Yes there is a lot of water on Earth, but at one point crude oil was though inexhaustible. Better refinement processes and higher demand proved that statement wrong.

Why are my thoughts regarding this wrong, or am I right and why isn't anyone concerned.

P.S. I considered putting this on World Building but it feels more legitimate than it should be.

Kayot
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    The gist is that it is possible to fuse deuterium. However the reactors presently don't generate as much power as they consume to create the fusion reaction. If/when scientists do get a fusion reactor working that creates a net surplus of energy then it will be a remarkable source of clean energy. – MaxW Sep 16 '18 at 02:09
  • Solar and wind energy with a peak battery storage facility can replace power plants and they are completely renewable. Fusion power isn't renewable as it destroys the hydrogen atom. However this is off question. I'm wanting to know what I'm missing that makes destroying hydrogen+1 (deuterium) and eventually hydrogen a good idea. It seems like a bad plan in the long run. Maybe this is the wrong stack for this question? – Kayot Sep 16 '18 at 03:33
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    @Kayot Yes, this is definitely a physics question. The answer is that we could power the world from deuterium and tritium (which is made from lithium, actually) for thousands of years without making a noticeable dent in the supplies available on earth ($5x10^{13}$ tons of deuterium in the worlds oceans $2x10^{11}$ tons of Li). – Karl Sep 16 '18 at 12:18
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    Nothing "wrong" with using solar and wind. There is a humongous amount of water on the planet. Using a tiny fraction of it would not be a problem for a long time. Whether we have enough water to provide power till the sun novas and destroys the planet in 5 billion years is another matter. – MaxW Sep 16 '18 at 15:27
  • So it's not that this isn't an issue, more that it's like, "It won't be a problem in my life time so why care?" scenario? – Kayot Sep 16 '18 at 16:00

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The energy released by a the fusion reaction is exorbitantly higher than that of chemical reactions, according to

https://www.iter.org/sci/FusionFuels

four million times more energetic (per mass) than burning conventional chemical fuel. If the plan would be to get the deuterium by elektrolysis from ocean water the normal hydrogen would not be used. Arguments against nuclear fusion that I have heard of are:

-can create radioactive products (if I remember correctely it has something to do with the generated neutrons)

-big initial starting energy requiered (how do you get them back running in case of an blackout)

-expensive costruction which needs to be able to withstand high temperatures

and this list is by no means conclusive...

Beny Benz
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  • You forgot the one about a massive nuclear explosion because of reasons. I had a thirty minute discussion with a friend explaining that it would only slag the reactor. – Kayot Sep 16 '18 at 03:27
  • @Kayot A fusion reactor just cannot explode. Fission reactors explode if they are built and run by idiots who refuse to understand that a molten reactor core produces hydrogen gas from the coolant water. – Karl Sep 16 '18 at 12:11
  • Or if your reactor gets hit by a tsunami and all of your emergency systems fail. Whereas the fusion reactor's plasma would expand if the magnets holding it in place would fail and cooles which stops the fusion. There are other types of fission reactors with heavy water as moderator (to slow down the neutrons) which are said to be saver because the fission stops if the heavy water would be replaced with water or removed... – Beny Benz Sep 16 '18 at 13:48
  • That's what I said. I had to explain that in a worse case scenario it would slag the reactor. That means it would simply melt the inside and then cool off. – Kayot Sep 16 '18 at 15:58
  • @BenyBenz Which happens if you first deny the danger of tsunamis at the japanese coast, and then when the inevitable has happened don't fly in emergency pumps and power generators. And still then the reactors wouldn't have exploded if they had had the catalytic converters for hydrogen which were installed in e.g. german reactors (enforced by law) thirty years ago. (Heavy water reactor cores also melt if they are inadequately cooled.) – Karl Sep 18 '18 at 04:37