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Helium Crisis Approaching
vrmlguy writes "Within nine years the National Helium Reserve will be depleted, according to an article in Science Daily. It quotes Dr. Lee Sobotka, of Washington University in St. Louis: 'Helium is non-renewable and irreplaceable. Its properties are unique and unlike hydrocarbon fuels (natural gas or oil), there are no biosynthetic ways to make an alternative to helium. All should make better efforts to recycle it.' (The St. Louis Post-Dispatch has a local article with quotes from Dr. Sobotka and representatives of the balloon industry.) On Earth, Helium is found mixed with natural gas, but few producers capture it. Extracting it from the atmosphere is not cost-effective. The US created a stockpile, the National Helium Reserve, in 1925 for use by military dirigibles, but stopped stockpiling it in 1995 as a cost-saving measure."
What exactly uses Helium that is all that important?
According to wikipedia the applications of helium
* Because it is lighter than air, airships and balloons are inflated with helium for lift. In airships, helium is preferred over hydrogen because it is not flammable and has 92.64% of the buoyancy (or lifting power) of the alternative hydrogen (see calculation.)
* For its low solubility in water, the major part of human blood, air mixtures of helium with oxygen and nitrogen (Trimix), with oxygen only (Heliox), with common air (heliair), and with hydrogen and oxygen (hydreliox), are used in deep-sea breathing systems to reduce the high-pressure risk of nitrogen narcosis, decompression sickness, and oxygen toxicity.
* At extremely low temperatures, liquid helium is used to cool certain metals to produce superconductivity, such as in superconducting magnets used in magnetic resonance imaging. Helium at low temperatures is also used in cryogenics.
* For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a coolant in some nuclear reactors, such as pebble-bed reactors.
* Helium is used as a shielding gas in arc welding processes on materials that are contaminated easily by air. It is especially useful in overhead welding, because it is lighter than air and thus floats, whereas other shielding gases sink.
* Because it is inert, helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, in gas chromatography, and as an atmosphere for protecting historical documents. This property also makes it useful in supersonic wind tunnels.
* In rocketry, helium is used as an ullage medium to displace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to make rocket fuel. It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles. For example, the Saturn V booster used in the Apollo program needed about 13 million cubic feet (370,000 m) of helium to launch.[2]
* The gain medium of the helium-neon laser is a mixture of helium and neon.
* Because it diffuses through solids at a rate three times that of air, helium is used as a tracer gas to detect leaks in high-vacuum equipment and high-pressure containers, as well as in other applications with less stringent requirements such as heat exchangers, valves, gas panels, etc.
* Because of its extremely low index of refraction, the use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes.
* The age of rocks and minerals that contain uranium and thorium, radioactive elements that emit helium nuclei called alpha particles, can be discovered by measuring the level of helium with a process known as helium dating.
* The high thermal conductivity and sound velocity of helium is also desirable in thermoacoustic refrigeration. The inertness of helium adds to the environmental advantage of this technology over conventional refrigeration systems which may contribute to ozone depleting and global warming effects.
* Because helium alone is less dense than atmospheric air, it will change the timbre (not pitch[12]) of a person's voice when inhaled. However, inhaling it from a typical commercial source, such as that used to fill balloons, can be dangerous due to the risk of asphyxiation from lack of oxygen, and the number of contaminants that may be present. These could include trace amounts of other gases, in addition to aerosolized lubricating oil.
Maybe I'm missing the usefulness of some of those but it doesn't seem like a big deal.
One cannot "mine" helium. It comes dominantly from radioactive decay in the earth of Uranium and its decay products. But because it is so light, it generally leaks out of the ground, and escapes. Also because it is so light, it is not retained in the earth's atmosphere at all, and leaks into space (at which point it is irretrievable). Our supply right now comes from radioactive decay (over the last 5 billion years) which produced helium that accidentally got trapped in the earth (mostly in the same underground reservoirs as oil -- it is mixed in with natural gas). The half-life of Uranium is about 4.5 billion years, so the Helium is produced very slowly.
The problem is that it has widespread industrial and scientific uses, and its loss will have a severe impact on our science and industry. In particular it is used as a coolant (gets down to about 4K, and is the best way to get things to that temperature). Also it is used in any application requiring high field superconducting magnets. The fancy new High-T_c magnets generally cannot support large fields, so in fields like particle physics which require big magnets, they generally use simpler materials (e.g. Niobium-Titanium for the main LHC magnets) that only superconduct at temperatures much lower than the liquid Nitrogen boiling point.
-- Bob
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
Basically, whereas helium is less dense than air and thus raises your voice pitch, sulfur hexafluoride is more dense than air and thus lowers your voice pitch.
Wikipedia
Omnes stulti sunt.
That's not really practical. Let's assume, for the sake of argument, that a fusion reactor can convert 10% of the power from its reaction to electricity.
The most promising reaction, according to Wikipedia, is that of:
First of all, there is the Deuterium. This is harvested from Heavy Water, water that has one or two deuterium atoms instead of normal hydrogen atoms. This heavy water costs approximately US$300/kg[2] for consumers, and the deuterium produced approximately US$1/L[3]. This is a lot. Deuterium has a molar mass of approximately two g/mol, with one mole of a gas taking up one cubic metre at standard temperature/pressure. At US$1/L, this deuterium costs US$1000/m^3, or US$500/g (I'm assuming that gases volumes refer to STP. If I'm wrong, feel free to point this out---I've never dealt with bottled gas).
Next is tritium. At US$30000/g[4], it's hardly cheap. For the reaction to take place, you need the two isotopes to react stoichiometrically (in the proper ratio). IOW, for each mole of tritium, you need a mole of deuterium. Converted to masses (tritium's molar mass is approximately three), this means that you need a ratio of 3g tritium : 2g deuterium. For each mole of Tritium, you will get a mole of helium. Because we're dealing with helium-4, the molar mass is ~4g/mol. The rest of the mass is made up by the neutron; this doesn't matter to us. Therefore, to make four grams of helium, we need three grams of tritium, and two grams of deuterium. At the prices given, this is US$91000 per four grams of helium, which, because it is one mole, is one cubic metre at STP. Helium, as of 1986 (yeah, yeah, I know) cost US$37.50/1000f^3. This is about US$1.30/m^3. Think about those prices. 9.1 x 10^4 US$/m^3, vs 1.3 x 10^0 US$/m^3. That's almost five orders of magnitude. There would have to be be a bloody good reason to be using helium at those prices.
In conclusion:
Helium-4 produced by fusion will cost five orders of magnitude more than current prices
References:
Yes, nuclear fusion produces helium.
The fusion of 1kg of deuterium produces near enough 1kg of helium, and, umm, 2.7MeV per fusion * 6*10^23 atoms per mole * 500 moles of D atoms per kilogram / 2 deuteriums per fusion * 1.6e-19 joules per eV = 64.8 terajoules of energy.
So, a one-gigawatt fusion power plant would produce a kilo of helium every eighteen days; if the current electricity use of France were provided entirely by fusion plants, you'd get thirty tons a year. The large hadron collider uses 120 tons of helium, but efficiently; present planetary helium use is about seventy-five tons a day.
For comparison, the US produces from natural gas about 76 million cubic metres of helium a year; a cubic metre of helium weighs 1000/22.4*4 grams, so 76 million cubic metres weigh about fifteen thousand tons.