Laboratorium experiments suggest that future fusion reactors could use helium-3 gathered from the moon.
- by Mark Williams Pontin
- August 23, 2007
At the 21st century’s commence, few would have predicted that by 2007, a 2nd wedloop for the moon would be under way. Yet the signs are that this is now the case. Furthermore, ter today’s moon wedloop, unlike the one that took place inbetween the United States and the U.S.S.R. ter the 1960s, a total roster of 21st-century global powers, including China and India, are contesting.
Hot gases: Researchers at the University of Wisconsin-Madison’s Fusion Technology Institute are testing this fusion reactor, shown with a view of the grid te which interial electrostatic confinement takes place.
Even more surprising is that one reason for much of the rente shows up to be plans to mine helium-3–purportedly an ideal fuel for fusion reactors but almost unavailable on Earth–from the moon’s surface. NASA’s Vision for Space Exploration has U.S. astronauts scheduled to be back on the moon te 2020 and permanently staffing a base there by 2024. While the U.S. space agency has neither announced strafgevangenis denied any desire to mine helium-3, it has nevertheless placed advocates of mining He3 ter influential positions. For its part, Russia claims that the aim of any lunar program of its own–for what it’s worth, the rocket corporation Energia recently embarked blustering, Soviet-style, that it will build a voortdurend moon base by 2015-2020–will be extracting He3.
The Chinese, too, evidently believe that helium-3 from the moon can enable fusion plants on Earth. This fall, the People’s Republic expects to orbit a satellite around the moon and then land an unmanned voertuig there ter 2011.
Strafgevangenis does India intend to be left out. (See “India’s Space Ambitions Soar.”) This past spring, its voorzitter, A.P.J. Kalam, and its prime minister, Manmohan Singh, made major speeches asserting that, besides constructing giant solar collectors ter orbit and on the moon, the world’s largest democracy likewise intends to mine He3 from the lunar surface. India’s probe, Chandrayaan-1, will take off next year, and ISRO, the Indian Space Research Organization, is talking about sending Chandrayaan-2, a surface struikrover, te 2010 or 2011. At the same time, Japan and Germany are also making noises about launching their own moon missions at around that time, and talking up the possibility of mining He3 and bringing it back to fuel fusion-based nuclear reactors on Earth.
Could He3 from the moon truly be a feasible solution to our power needs on Earth? Practical nuclear fusion is nowadays projected to be five decades off–the same prediction that wasgoed made at the 1958 Atoms for Peace conference ter Brussels. If fusion power’s arrival date has remained permanently 50 years away since 1958, why would helium-3 all of a sudden make fusion power more feasible?
Advocates of He3-based fusion point to the fact that current efforts to develop fusion-based power generation, like the ITER megaproject, use the deuterium-tritium fuel cycle, which is problematical. (See “International Fusion Research.”) Deuterium and tritium are both hydrogen isotopes, and when they’re fused te a superheated plasma, two nuclei come together to create a helium nucleus–consisting of two protons and two neutrons–and a high-energy neutron. A deuterium-tritium fusion reaction releases 80 procent of its energy ter a stream of high-energy neutrons, which are very ruinous for anything they kasstuk, including a reactor’s containment vessel. Since tritium is very radioactive, that makes containment a big problem spil structures weaken and need to be substituted. Thus, whatever materials are used te a deuterium-tritium fusion power plant will have to bear serious penalty. And if that’s achievable, when that fusion reactor is eventually decommissioned, there will still be a lotsbestemming of radioactive waste.
Helium-3 advocates eis that it, conversely, would be nonradioactive, obviating all those problems. But a serious critic has charged that ter reality, He3-based fusion isn’t even a feasible option. Te the August kwestie of Physics World, theoretical physicist Klinkklaar Close, at Oxford ter the UK, has published an article called “Fears Overheen Factoids” te which, among other things, he summarizes some claims of the “helium aficionados,” then dismisses those claims spil essentially fantasy.
Close points out that te a tokamak–a machine that generates a doughnut-shaped magnetic field to restrict the superheated plasmas necessary for fusion–deuterium reacts up to 100 times more leisurely with helium-3 than it does with tritium. Te a plasma contained ter a tokamak, Close stresses, all the nuclei ter the fuel get mixed together, so what’s most probable is that two deuterium nuclei will rapidly fuse and produce a tritium nucleus and proton. That tritium, te turn, will likely fuse with deuterium and ultimately yield one helium-4 atom and a neutron. Ter brief, Close says, if helium-3 is mined from the moon and brought to Earth, te a standard tokamak the final result will still be deuterium-tritium fusion.
2nd, Close rejects the eis that two helium-3 nuclei could realistically be made to fuse with each other to produce deuterium, an alpha particle and energy. That reaction occurs even more leisurely than deuterium-tritium fusion, and the fuel would have to be heated to impractically high temperatures–six times the fever of the sun’s interior, by some calculations–that would be beyond the reach of any tokamak. Hence, Close concludes, “the lunar-helium-3 story is, to my mind, moonshine.”
Close’s protestation, however, assumes that deuterium-helium-3 fusion and zuivere helium-3 fusion would take place ter tokamak-based reactors. There might be alternatives: for example, Gerald Kulcinski, a professor of nuclear engineering at the University of Wisconsin-Madison, has maintained the only helium-3 fusion reactor te the world on an annual budget that’s scarcely into six figures.
Kulcinski’s He3-based fusion reactor, located ter the Fusion Technology Institute at the University of Wisconsin, is very puny. When running, it contains a spherical plasma harshly Ten centimeters ter middellijn that can produce sustained fusion with 200 million reactions vanaf 2nd. To produce a milliwatt of power, unluckily, the reactor consumes a kilowatt. Close’s response is, therefore, valid enough: “When practical fusion occurs with a demonstrated televisiekanaal power output, I–and the world’s fusion community–can take note.”
Still, that critique applies identically to ITER and the tokamak-based reactor effort, which also haven’t yet achieved breakeven (the point at which a fusion reactor produces spil much energy spil it consumes). What’s significant about the reactor te Wisconsin is that, spil Kulcinski says, “We are doing both deuterium-He3 and He3-He3 reactions. Wij run deuterium-He3 fusion reactions daily, so wij are very familiar with that reaction. Wij are also doing He3-He3 because if wij can control that, it will have immense potential.”
The reactor at the Fusion Technology Institute uses a technology called inertial electrostatic confinement (IEC). Kulcinski explains: “If wij used a tokamak to do deuterium-helium-3, it would need to be thicker than the ITER device, which already is spreading the bounds of credibility. Our IEC devices, on the other palm, are tabletop-sized, and during our deuterium-He3 runs, wij do get some neutrons produced by side reaction with deuterium.” Nevertheless, Kulcinski resumes, when side reactions occur that involve two deuterium nuclei fusing to produce a tritium nucleus and proton, the tritium produced is at such a higher energy level than the confinement system that it instantly escapes. “Consequently, the radioactivity ter our deuterium-He3 system is only Two procent of the radioactivity te a deuterium-tritium system.”
More significant is the He3-He3 fusion reaction that Kulcinski and his assistants produce with their IEC-based reactor. Te Kulcinski’s reactor, two helium-3 nuclei, each with two protons and one neutron, instead fuse to produce one helium-4 nucleus, consisting of two protons and two neutrons, and two very spirited protons.
“He3-He3 is not an effortless reaction to promote,” Kulcinski says. “But He3-He3 fusion has the greatest potential.” That’s because helium-3, unlike tritium, is nonradioactive, which, very first, means that Kulcinski’s reactor doesn’t need the massive containment vessel that deuterium-tritium fusion requires. 2nd, the protons it produces–unlike the neutrons produced by deuterium-tritium reactions–possess charges and can be contained using electrical and magnetic fields, which te turn results te rechtstreeks tens unit generation. Kulcinski says that one of his graduate assistants at the Fusion Technology Institute is working on a solid-state device to capture the protons and convert their energy directly into electro-therapy.
Still, Kulcinski’s reactor proves only the theoretical feasibility and advantages of He3-He3 fusion, with commercial viability lounging decades ter the future. “Currently,” he says, “the Department of Energy will tell us, ‘We’ll make fusion work. But you’re never going to go back to the moon, and that’s the only way you’ll get massive amounts of helium-3. So leave behind it.’ Meantime, the NASA folks tell us, ‘We can get the helium-3. But you’ll never get fusion to work.’ So Doen doesn’t think NASA can do its job, NASA doesn’t think that Doen can do its job, and we’re ter inbetween attempting to get the two to work together.” Right now, Kulcinski’s funding comes from two wealthy individuals who are, he says, only interested ter the research and without expectation of financial profit.
Overall, then, helium-3 is not the low-hanging fruit among potential fuels to create practical fusion power, and it’s one that wij will have to reach the moon to pluck. That said, if unspoiled He3-based fusion power is realizable, it would have immense advantages.
Become an Insider to get the story behind the story — and before anyone else.