If you are citizen of an European Union member nation, you may not use this service unless you are at least 16 years old.
You already know Dokkio is an AI-powered assistant to organize & manage your digital files & messages. Very soon, Dokkio will support Outlook as well as One Drive. Check it out today!

the problem with D-T

Page history last edited by Andrew Alder 3 years, 3 months ago

A page of energy issues and probably an unpopular essay

This page is largely but not entirely obsoleted by myths of fusion

Why D+T is popular
Why D+T should not be popular
The spin
The solution

Why D+T is popular

All serious fusion power projects are focussed on using the Deuterium-Tritium_fusion reaction, also known as D+T or (confusingly) D-T. (I called this page D-T because of the software limitations of the excellent freemium service I'm using.)

And there are good reasons for this.

Of all known nuclear_fusion_reactions it is the easiest to produce in the laboratory.
It is well understood, as the reaction that powers thermonuclear_weapons.
It is far, far faster then the P+P_reaction that powers the Sun.

Why D+T should not be popular

Unfortunately, 80% of the energy released by D+T is in the speed of a very, very fast neutron.

It's not obvious how to harness this energy. To say the least.

Neutron radiation is biologically the deadliest form of nuclear radiation. That is the principle of the neutron_bomb. But that is the least of the problems.

Neutrons are so very penetrating because they are light and uncharged. They don't tend to react with the materials through which they pass. But even when they do it's not really what we want them to do.

Perhaps it's easiest to contrast their behaviour to that of the fission products whose speed is the major energy release for nuclear fission. This is readily converted into heat, because they are relatively heavy and are strongly positively charged. So they soon give up this energy to their surroundings, heating them up. And this heat can then be used in a nuclear (fission) power station to generate electricity.

Not so with fast neutrons. When they hit another nucleus, one of two things happens.

They can bounce off. But because they are so light compared to this other nucleus, little energy is transferred.
They can be absorbed. Their energy is wholly absorbed by this nucleus, which becomes highly radioactive.

There is no third possibility.

So the neutrons do eventually give up this energy. But it's still not in a very convenient form for generating electricity!

In fact it is a menace. The near-vacuum inside a fusion chamber is completely transparent to neutrons. The intense magnetic fields in a tokamak or stellarator are similarly transparent. So these neutrons end up striking the plasma-facing_material, transmuting its elements and making it weaker, and radioactive.

And what is even more important, for no useful purpose.

The spin

China claims its https://en.wikipedia.org/wiki/HL-2M uses the reaction that makes the Sun hot, and that it is similar "calibre" to ITER. Wrong on both counts. See

and note for example the size of the machine in the photos.