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FAQ - Deuterium - our fuel.. where does it come from and other questions

Posted: Thu Apr 23, 2020 7:10 am
by Richard Hull
Deuterium is very important to us as it is the very stuff, the only stuff, that we are allowed, as amateurs to acquire that will fuse at voltages within our reach. It is the only legal source of neutrons for research at the amateur level. We all know that it is obtained solely from the isotopic separation from regular water where it exists as .0156% of all the hydrogen atoms in the water. Through a number of varied and involved isotopic separations that require varying amounts of energy, the ratio can be boosted or "enriched" within water to a level of about 99.97 percent D20 purity. This water is called "heavy water". By comparison, the separation of the lower Z isotopes are relatively easy. However all isotopic separations require complex systems and usually a tremendous amount of energy per unit mass enrichment. Some early processes were incredibly energy hungry. This was the case for heavy water and remains the number one consideration in more modern processes that have greatly reduced the energy needs and costs, yet remain complex. Still, considering all the modern methods and energy consumption, the cost per gram of 99% or greater enriched heavy water costs about 50 cents at retail in quantities over 100 grams.

The pure gas is easily obtained via a moderately involved, but manageable process via electrolysis of pure heavy water. At retail, this dry gas and its associated, non-refillable tank with shipping runs about $300 per 50 liter STP bottle. While rather expensive in high purity, dry, gaseous form, tanked gas is by far the easiest form to use in a fusor system scenario.

Some few fusors have been successfully powered via careful electrolysis of heavy water and gas drying efforts. This typically involves the reversed use of a small "fuel cell" that will hopefully be a one time expense beyond the heavy water feed stock costs. When properly applied in a manner that really functions well, one might expect a reduction in costs for deuterium, so obtained, by a factor of a full order of magnitude or better, when compared with the bottled, dry deuterium gas!

One of the big touts of fusion and its "green" supply source in that the fuel supply is virtually inexhaustible, (planetary water). In addition, the waste product from deuterium production is very pure water. The statement inexhaustible is one of planetary-wide volumetrics as opposed to its truly exhaustible nature. This is all very true related to deuterium only and would be fine in a pure D-D fusion reactor, as we all know. However, the world is not working on D-D fusion power reactors. A working D-T fusion reactor would still need constant attention and remote replacement of internal, highly radioactive components, create very high levels of radiation and also produce huge levels of short lived deadly radioactive debris. However, back to deuterium issues that interest we D-D fusioneers....

The above might lead us to the question, where did the deuterium in water originally come from and why is the hydrogen to deuterium ratio what it is?

Just as we can never produce industrial quantities of helium from scratch by any process beyond the strictly limited earthly supply found in gas and oil deposits, so we cannot produce, on earth, new industrial sources of deuterium outside of our boundless supply of sea water. Like helium, we just harvest deuterium! Were it not for our oceans, there would be no usable source of deuterium on earth! Deuterium is primordial in nature! It is here due to the big bang. Novas and super novas can't produce it! They consume it, just as new born and burning stars do. Deuterium can only be produced via P-P fusion!!! P-P fusion, and thus, deuterium production can only be done in quantity, at the current temperature of the universe, within the cores of stars. Once produced in stellar fusion, the average deuterium nucleus is nearly instantly, (within 6 seconds), fused with another proton to 3He and the process moves on with the helium 3 nucleus fusing on average with another 3He nucleus or another proton or deuteron. Thus, newly formed, stellar deuterium never escapes from its star, it is far too easily fused in a sea of protons within a star's core.

What deuterium there is in the universe is remnant deuterium from the "Big Flash", about 20 minutes after the big bang when the limited, thermally P-P fused deuterons stopped being able to fuse due to the reduced universal temperature. All "first fusion" ceased at this point. Neutrons which earlier were on a par with protons started to decay increasing the number of protons and electrons. This left the universe with only photons, neutrinos, hydrogen nuclei, helium nuclei and what little deuterium that was not fused earlier. Both deuterium and hydrogen with some helium spread throughout the expanding volume of the cooling cosmos until about 500,000 years later when true electron encircled atoms could form neutral hydrogen, helium and deuterium. Over a much longer period this neutral matter would ultimately coalesce into gravitationally assembled groups to form proto-galaxies and the first fast burning stars. In theory, the universal H to D ratio is rather fixed, save for perhaps, very isolated pockets around the universe. With each earth bound fusion our truly exhaustible supply of deuterium is diminished.

Interestingly, after about .01 seconds following the big bang, most all quarks were gone and the universe was filled with equal numbers of electrons, positrons, neutrinos, photons and a very tiny amount of protons and neutrons. Thus, charge and mass were real for the first time in the universe. Fusion came and went in the still blisteringly hot universe. Newly formed fused nuclei were pretty much instantly destroyed by photons and neutrinos. At .1 second after the big bang it is believed that due to the difference in mass of the protons and neutrons, proton formation proceeded a bit faster and that the universe would consist of about 62% protons and 38% neutrons, when formal nucleon creation ended. As the universal temperature fell to equal about 1meV, electron and positron annihilation proceeded rapidly. At about 30 minutes into the big bang, a lot of neutrons had decayed re-seeding the universe with electrons and more protons. Fusion occurred due to there still being enough energy to fuse hydrogen to deuterium which quickly became helium. Some tiny amount of slightly higher Z elements were also formed. Ultimately, in a few thousand years, the universe had expanded to the point of not only reduced collisions, but also to the point that "first fusion" all but ceased. This left the universe filled with hydrogen and a bit of helium and very little remnant deuterium. It would take hundreds of millions of years before the cooling and expansion could allow electrons to link up to form stable hydrogen, helium and deuterium atoms. Much earlier, the neutrinos could no longer interact with matter and by this late time, the photons were degraded to the point that they could no longer even break electronic bonds on a universal scale. Charge and gravity would come to rule the universe and create what light, motion, magnetism and fusion on an isolated, macroscopic basis as currently seen across the universe.

In a book I am now reading I found a profound statement that the author put in a mere footnote while discussing the physics of renewable energy sources.
... "In a wider context, all energy currently originates from gravitational collapse, annihilation, (charge driven), fusion reactions, (gravitational driven) or mass loss into black holes (gravitational driven) and its sources are never renewable." (or recoverable)
... Note: all parenthesis are mine to remind you of the two ruling potential energies contained solely within matter, driving all known real energy production in the current universe. Once you pull the potential energy trigger, the entire energy available over the entire universe is forever diminished in a death spiral. Entropy... what was once given by the big bang, is now taken away.

Based on when the big bang happened relative to today, all of the above nuclear and even early chemical processes occurred like a flashbulb going off compared to the current age of the universe. Gravity and charge were slow acting, thank goodness. (Making the universe long lived) Fusion is only possible again in the universe due to local gravity and charge exchange reactions within stars, again, thank goodness. (Long stellar life times) Photonic radiation is also limited to localized matter and kinematic charge exchange reactions. (Heat and just enough light to see by here on earth)

The tale is told, and you now know a good deal about deuterium, the nuclear fusion fuel found and harvested on earth to be burned in your fusor. Oh, and try not to gobble up so much of the Earth's deuterium. Don't be a pig!

Richard Hull