Yes it was only $100/L a few years ago, but new uses (not fusion) have been found for it. See especially 2nd paragraph of my reply to quotes (2)&(3) near end of this post.
Popular Mechanics says: “…Substituting helium-3 for tritium allows the use of electrostatic confinement, …” From: Mining The Moon - Rare Minerals - Helium 3 - Popular Mechanics
BT comments: I am not up to date on recent developments, but think this is misleading, if not completely wrong. First generation D+T fusion (still far from any demonstration of economic viability after nearly 40 years of effort) is much easier to achieve than D+He3 reaction as with twice the Coulomb repulsion much higher temperatures (and pressure at same density) are required. Also, I´m almost sure the reaction rate is significantly lower than for D+T, which means that even at the same plasma density the reaction chamber must be much larger (more costly) to produce the same output energy.
Offsetting these disadvantages is fact that all the D+He3 fusion energy is in charged particles, not the bulk of it in a 17.6 Mev neutron of the D+T reaction, which is thermalized at high temperature to make heat for conventional steam turbine. I.e. only ~40% of the D+T fusion energy ends up as electrical energy. The energy released in D+He3 is kinetic but random in direction. Its motion must be made unidirectional for climbing up a retarding electric field. As it slows down, its energy loss is given to the field. Normally a “magnetic mirror” would be used as charged particle can “leak” out of it along the axis and only those with velocity along the axis field lines do so.
There are many, seldom discussed, problems: Such as the positive charged particles carry almost all of the energy, but with each there is an electron tagging along. More magnetic field structure is required to separate them as if there is only one “retarding field” it is an accelerating filed for the electrons. Also in the steady state as energy is removed from the ions neutral atoms will form and diffuse back towards the reaction volume stealing energy from it (by frequent radiation, until the neutral is fully ionized)
Part I summary: It is extremely unlikely that a D+He3 reactor with electro-static energy recovery can even be made, and nearly certain it would not be economically competitive with simple natural gas / steam turbine power generation. Hell, there are no creditable arguments that even first generation D+T fusion will be economically feasible, that I know of, but at least after three decades of expensive effort, ITER has briefly achieved "break even" (Fusion energy released equal the energy being consumed at that instant). Has that hot plasma been confined as long as one second yet?
Following is from your Wiki link (http://en.wikipedia.org/wiki/Helium-3). Initial numbers tie quotes to my later comments.
1) “… helium-3 was found to be about 10,000 times more rare with respect to helium-4 in helium from wells”
2) “… Tritium, with a roughly 12-year half-life, decays into helium-3, which can be recovered. Irradiation of lithium in a nuclear reactor can also produce tritium, and thus (after decay) helium-3. …”
3) “…Current US industrial consumption of Helium-3 is approximately 60,000 liters per year; cost at auction has typically been approximately $100/liter although increasing demand has raised prices to as much as $2,000/liter in recent years. …virtually all helium-3 used in industry is manufactured. Helium-3 is a product of tritium decay, and tritium can be produced through neutron bombardment of deuterium, lithium, boron, or nitrogen targets. … Production of tritium in significant quantities requires the high neutron flux of a nuclear reactor; … the US Department of Energy recently began producing it by the lithium irradiation method at the Tennessee Valley Authority's Watts Bar reactor. Substantial quantities of tritium could also be extracted from the heavy water moderator in CANDU nuclear reactors. …”
4) “…Helium is also present as up to 7% of some natural gas sources, … the US 2002 stockpile of 1 billion normal m3 {of helium} would have contained about 10 to 100 kilograms of helium-3.” …”
5) “…Anderson's estimate of another 1200 metric tonnes in interplanetary dust particles on the ocean floors.[37] In the 1994 study, extracting helium-3 from these sources consumes more energy than fusion would release.[ …”
6) “ … The amount of fuel needed for large-scale applications can also be put in terms of total consumption: … Electricity consumption by 107 million U.S. households in 2001 totaled 1,140 billion kW•h" Again assuming 100% conversion efficiency, 6.7 tonnes of helium-3 would be required for that segment of the energy demand of the United States, 15 to 20 tonnes given a more realistic end-to-end conversion efficiency …”
Billy T´s comments by number:
(1)&(4) US already separates helium form the natural gas at least one well (in Texas, I think). Very little cost, compared to moon mining to also separate the He3 from the more dominate He4.
(2)&(3) Canada has several CANDU reactors, and I think more will be built in other countries too, if not already operating there. (Name is from Canada & DeUterium in the heavy water moderator). IMHO the CANDU reactor, which is economically competitive, should be the only design mankind uses for electric power as it runs on natural uranium. US and USSR were needing enrichment plants to make atomic bombs – that is why many other types of reactors exist. For example, if Iran wants nuclear power, let them build CANDU reactors. The heavy water they require is not “used up” – It is a one time capital cost, much less than the centrifuges etc. of a U235 enrichment plant.
AFAIK, they don´t bother to collect and store the Tritium a CANDU reactor produces to get He3 as the T decays. Probably as the value of He3 was only $100/L, (less than 10% of the cost of most brand name perfumes!). If world closed most enrichment plants, and ran more CANDU reactors its needs of He3 could easily be supplied at cost of < $100/L.
(5) It makes more sense to robotically collect He3 in “cosmic dust” from the ocean floor than the moon, but it is not worth it (net negative energy yield even if D+He3 fusion were economical) All the technology needed has already been developed by oil companies. Compared to robots that can fill ocean floor well casings with cement, etc. scooping up “cosmic dust” from the floor is child´s play.
I think the reason is that the He3 is NOT just a surface 2D liquid adsorbed on specks of cosmic dust, (easily driven off at less than 100C heat) but embedded in their interiors. To drive it out, requires heating to red hot temperatures, if not actually melting of the dust. This is the same problem with He3 imbedded in crystalline rocks on the moon. Even if the moon He3 concentration were 100ppb (0.000,000,01) to get a gram of He3 would require heating 1,000 Kg of the crystals with He3 to at least red hot conditions.
The idea that there is He3 in ice crystals seems to be wishful thinking. Here from ref 41 of your Wiki link (the only factual data with analysis is from this Russian study) is where the He3 (that does not boil off in sunlight) is:
“…The probable reserves of implanted 3He in lunar
regolith in the area of high titanium basalt occurrence
concern to the highest category I and are estimated as
53000 tons on the Moon Near Side. As a whole on all
Moon surface the probable reserves of this category
are estimated as 61000 tons.
The probable 3He reserves of category II concern
to areas of occurrence of sea basalts with moderate
TiO2 abundance (3-5 %) and are estimated as 109000
tons on the Near Side. It is twice more on reserves,
than in category I, but it is almost in 4 times more on
the occupied area.
The areas with probable reserves of a category III
are characterized by low titanium mare basalts occurrences
with the lowered abundance of 3He in regolith.
The probable reserves of this category are estimated
as 143000 tons on the Moon Near Side. Reserves
of this category settle down approximately on
the same areas, as well as stocks categories II, but are
characterized almost by the twice greater thickness of
regolith.
In the sum probable reserves of first three
categories are estimated in 306000 tons on Moon Near
Side and occur on the 12 % of all area of a hemisphere.
Practically the reserves of first three categories
occur in the lunar mares territory. The area of mare
geological complexes is estimated approximately as
13 % of all Near Side area. …”
Note the He3 collected by US astronauts was from soil currently in the solar wind. Surely, there is an dynamic equilibrium concentration of the surface adsorbed He3 as solar wind adds and solar heating boils off He3. Perhaps that is the concentration (15ppb max) they observed.
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