Caption: Deuteron-triton nuclear fusion cartoon. The protons are orange and the neutrons are grey.

Down here on Earth, we would like to have STABLE hydrogen burning (with nuclear burning being meant by burning) or, as it is called, controlled fusion for fusion power (i.e., commercial energy from controlled fusion).

To explicate:

1. The D-T (deuterium-tritium) fuel cycle is the most promising one at the moment for controlled fusion for fusion power.

   Note the D-T (deuterium-tritium) fuel cycle is a one-step nuclear burning process. The multi-step nuclear burning processes that happen in stars (i.e., the proton-proton chain reaction and the CNO cycle) are much too complicated to implement in fusion reactors. Note also the first step of the proton-proton chain reaction (the nuclear burning of 2 hydrogens (H) to 1 deuteron (D,H-2)) is much too slow to implement just by itself in fusion reactors.

2. The heart of the D-T (deuterium-tritium) fuel cycle fuses exothermically deuterium (D, H-2) (the hydrogen isotope whose nucleus has one proton and one neutron: i.e., heavy hydrogen) and tritium (T, H-3) (the hydrogen isotope whose nucleus has one proton and two neutrons: i.e., heavier hydrogen) to helium-4 (He-4) and create electrical power (HRW-1109).

3. The reaction is NOT part of PP chain reaction that powers some stars (e.g., the Sun). There is NO abundant tritium in nature (see below).

   As noted above, the PP chain reaction is much too complex and too slow for feasible fusion reactors (see HRW-1109; nuclear_burning_pp.html).

4. Actually, there is nothing magical about how controlled fusion creates the electrical power: the controlled fusion generates heat energy which powers a heat engine which powers an electric generator which creates electrical power.

   Except for the heat energy source, everything is the same in principle as for conventional nuclear-fission nuclear power or fossil-fuel power.

5. A bit of terminology: Formally, deuterons are the nuclei of the deuterium atom; tritons are the nuclei of the tritium atom.

   In practice, one often uses the terminology loosely: e.g., deuterium for deuterons and vice versa.

6. Fusion power is great.

7. The fuel is practically limitless---or so we thought till circa 2022.

   1 in every 6700 hydrogens on Earth is a deuterium (HRW-1109) and we have a lot water (H2O).

   Collecting the deuterium is expensive, but NOT that expensive.

   Tritium is a radioactive isotope with half-life of 12.32 Julian years, and so large amounts to NOT exist in nature, but it can be bred in fission reactors (see Wikipedia: Tritium: Production) and fusion reactors themselves (see Daniel Clery, 2022, Jun23, Science, "Out of Gas: A shortage of tritium fuel may leave fusion energy with an empty tank").

   But circa 2022, it has become uncertain that fusion reactors can breed adequate tritium, and so a lot fission reactors for breeding may be needed for controlled fusion (see Daniel Clery, 2022, Jun23, Science, "Out of Gas: A shortage of tritium fuel may leave fusion energy with an empty tank"). Some wonder if this tritium problem will stop controlled fusion even if D-T (deuterium-tritium) fuel cycle is technically feasible.

   By the by, a half-life is a sort of mean lifetime of a atomic nucleus before radioactive decay. More exactly, half a sample of a radioactive isotope will decay on average after one half-life.

8. The difficulty with fusion power is that it is difficult to make plasmas hot enough (∼> 10**7 K) and control them.
   Recall, a plasma is an ionized gas.

   If such a plasma touches a wall made of a solid, it vaporizes the wall and cools.

   The main solution to the control problem has always been to contain the plasma with magnetic fields rather than solid containers.

   But magnetic containment and extraction of heat energy there from has its own difficulties.

9. The advantages of fusion power:
   1. Limitless fuel as aforesaid---as long as you have enough fission reactors and/or fusion reactors to breed tritium. Note the breeder fission reactors do NOT have to be optimized for energy generation.

      But there is the tritium problem (see above).

   2. Fusion power is inherently safe because fusion reactors have NO chance of having becoming uncontrolled. If anything goes wrong, they just stop reacting and turn off---in fact, that's the problem so far: the fusion reactors are pretty much off.

      This is unlike conventional fission reactors which are always on the verge of nuclear meltdown.

   3. Fusion reactor technology in itself is NOT necessarily a nuclear weapons proliferation concern. Fusion reactors do NOT directly connect to bomb manufacture.

      Fission reactors are always related to nuclear weapons since their fuel (uranium-235 (half-life 0.7038 Gyr) or plutonium-239 (half-life 24110 years)) can be used to make fission bombs. The breeder fission reactors for tritium can be kept in safe countries which just export tritium for fusion reactors in other countries.

      Note fusion bombs must always be ignited by fission bombs and are NOT related technologically to fusion reactors.

      By the by, if anyone knows how to ignite fusion bombs from a chemical-reaction explosion, they are keeping very quiet about it.

   4. Fusion reactors generate radioactive waste with only short half-lives???. It can just be buried in the ground and forgotten about since in a few decades it is harmless????. Let's hear it for Yucca Mountain---the Dracula of deep geological repositories for nuclear waste---it always rises from the dead.
      I think this is all true, but I need to check it sometime sine die---but maybe on the Greek kalends.

      This is unlike the radioactive waste from fission reactors which can have very long half-lives, and so requires quasi-eternal stewartship: i.e., high-level radioactive waste management including of mixed waste. Of course, the breeder fission reactors for tritium will produce long-lived radioactive waste, and so everything is NOT happy.

10. The disadvantages of fusion power:
    1. The fusion power dream has been with us since circa 1945 and seems good for another 80 plus years (see Fusion power: History of research).

       Experimentally, controlled fusion has been done, of course. But whether commercial energy generation is possible is still uncertain. It may be technologically out of reach.

    2. The breeder fission reactors for tritium are a nuclear proliferation risk and a source of radioactive waste. For breeding from fusion reactors, there is again the tritium problem.

    3. The use of fusion power may be obviated by the use of renewable energy (most importantly solar power and wind power). Say 80 plus years from now fusion power arrives, but we already have all the commercial energy we need and want from renewable energy. In this case, much of the research into fusion power would have been a waste of time and effort.

11. One can conclude that fusion power is wonderful---except for the NOT working part.

    Can it work? Maybe, but yours truly is losing faith.

    And there's an old saying: "fusion power is the energy of the future---and it always will be."

12. Circa the 2020s, the big fusion power international research project is ITER (construction 2013--2025). But experiments with the D-T (deuterium-tritium) fuel cycle are expected to start way off in 2035 (see "Fuel for world's largest fusion reactor ITER is set for test run", Elizabeth Gibney, 2021, Feb22, Nature). So don't hold your breath for abundant fusion power.

13. For further elucidation, on nuclear physics, see Nuclear physics videos below (local link / general link: nuclear_physics_videos.html):

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