As global energy demands continue to grow and non-renewable energy sources steadily dwindle, human beings will need to turn to new and innovative ways to quench our energy thirst. Nuclear fusion is a promising technology that is destined for the limelight with the completion of the International Thermonuclear Experimental Reactor (ITER) set for 2016. ITER is an international collaborative project which aims to demonstrate the feasibility of sustaining an energy-positive fusion reaction for the first time. The reactor at ITER will use magnetic confinement to generate a fusion reaction based on the deuterium-tritium (D-T) cycle. The fusion of deuterium, a hydrogen isotope found in seawater, and tritium, a heavier and radioactive isotope of hydrogen, is the reaction that is utilized in thermonuclear weapons. ITER is intended to produce 500 Megawatts of power for every 50MW input—a 10:1 return.
The Mark II Lunar Volatiles Miner, designed by students, faculty, and scientific staff at UW-Madison, would use solar energy to harvest helium-3 from the moon’s surface.
Photo Credit: University of Wisconsin–MadisonThere are drawbacks to the deuterium-tritium fusion reactions. Nearly 80% of the energy is released as high-energy neutrons. Neutrons are not easily captured and must be slowed by some sort of medium. They cause significant structural damage over time. Additionally, concerns of radioactive waste need to be addressed.
It is hypothesized that it would take 40 tons of Helium 3 to provide all of the electricity that will be used in the United States in 2011.
A second generation reaction based on the fusion of deuterium and helium-3 (D-3He) is an attractive alternative to the first generation D-T cycle reactions because it produces significantly fewer high-energy neutrons. Professor Gerald Kulcinksi, nuclear engineer and director of the Fusion Technology Institute at the UW-Madison, has been researching fusion reactions involving helium-3 for over thirty years. In the 1980s, Kulcinski began researching D-3He fusion. “The problem is, we didn’t have any helium-3, and the only helium-3 on earth comes from the decay of tritium,” says Kulcinski. Yet the lure of a D-He3 reaction drove Kulcinski and his colleagues to search for the elusive isotope. Kulcinski says, “Around 1985, we all sat around and looked at each other and thought about where to find large amounts of helium-3 for civilian use.” Helium-3 is ejected from the sun as charged particles in the solar wind. However, the energy is not enough to get through anywhere atmospheric, and the particles will go around anything with a magnetic field.
Kulcinski says, “So you start out at Mercury. Mercury has no atmosphere, but it has a magnetic charge, so it did not catch any. Venus has no magnetic field, but it has a heck of an atmosphere. We have both, so we didn’t get any. The only body that’s close to the sun that has neither a magnetic field nor an atmosphere is the moon—our moon. So the scientists said it has to be there.”
After going through samples of lunar rocks brought back from the Apollo program, it was confirmed that every sample contained helium-3. “Even more interesting,” says Kulcinski, “is that on several of the Apollo missions they dug into the regolith—the dark, very fine material that covers the lunar surface, and all of it contained helium-3.” While the solar wind deposits only a thin layer of helium-3 on the surface of the moon, over the course of four billion years the moon has been repeatedly struck by meteorites which have pulverized the surface. This process has gardened the material into an extremely fine dust that can be up to 20 meters thick. According to Kulcinski, “the moon is the perfect catcher’s mitt up in the sky to catch helium-3.” There is an estimated one million metric tons of helium-3 on the surface of the moon.
While the majority of the world is studying the D-T cycle for fusion power, Kulcinski and his team of graduate students are experimenting with the fusion of two helium-3 isotopes (He3-He3). The reaction does not produce high-energy neutrons or radioactivity. It creates nuclear energy without nuclear waste.
“We’re using a third kind of way to make fusion,” says Kulcinski. “Not magnetic or inertial—we’re using electrostatic. It’s not new. It was invented by Philo Farnsworth who also invented the television. He didn’t get very far, but we found his papers and saw that the way he did it was particularly suited for high energy reactions like He3-He3.”
Professor Gerald Kulcinski consults with lab director (Rich Bonomo) and one of the program’s graduate students (Gabriel Becerra), over Helios, one of three fusion devices in the UW-Madison Fusion Technology Institute.
Photo Credit: Sara KarrakerA He3-He3 reaction has been performed in the small reactor which resides in the lower level of the Engineering Research Building. “I have some really great students who have actually run this,” said Kulcinski. “However, we have not yet gotten back more energy than we have put in. Mother Nature makes it harder as you go from 1st to 2nd to 3rd generation reactions. The third generation reaction requires on the order of four to five times more energy to make the reaction run. “Our goal is to produce a system that makes nuclear power with no nuclear waste. That’s the pot of gold at the end of the rainbow. Now, I probably won’t see that, but my students might. They have been making progress.”
If the He3-He3 fusion reaction can be improved and eventually perfected, it would have massive implications on the global energy supply. It is hypothesized that it would take 40 tons of helium-3 to provide all of the electricity that will be used in the United States in 2011. A space shuttle can carry 20 tons of cargo, so eight of them could theoretically power the world for a year.
Kulcinski and his colleagues have spent considerable time designing mining rovers that would be able to extract helium-3 from the moon’s surface. The rovers would forage the top layers of regolith and extract the particles less than a millimeter in diameter with a system of sieves. The dust would then be heated with solar energy to about 700°C at which point the helium would evaporate. Helium-3 would be separated from helium-4 on site, and the purified helium-3 would be shipped back to earth. Kulcinski claimsof this program that eventually, “the energy payback for every unit of energy we put into getting the material, we will get 300 units when we burn it. That’s including the making of the rockets, the rocket fuel to get to the moon, the support of the base, and the return trip back.”
Working with NASA Administrator Mike Griffin and former NASA astronaut Harrison Schmitt, Kulcinski was part of a group that Kulcinski explained, “My reaction was not simply disappointment. We worked so hard to get a return to the moon—not just for science even though science is very important—but this is the first time we knew of anything that was valuable enough that once we got there and set up all of our stations, we’d be able to send something back to earth to pay for the program.”
The United States is no longer interested in going back to the moon, so it may leave us behind with regards to He3-He3 fusion. While it’s understandable that the U.S. would be hesitant to back a program that may not have a payoff for over thirty years, the potential consequences of letting another country dominate the helium-3 market must not be ignored. The Chinese have talked about going to the moon and harvesting helium-3. Japan, Russia, and India have also expressed interest in helium-3 fusion. Kulcinski asked about having to buy helium-3 from another country, “Now, politically you ask yourself, is that any different from buying oil from the Middle East?”
He3-He3 fusion is still a long way off from breaking even in energy conversion. When Kulcinski started doing research with helium-3, it was $1000 per gram. The last time they purchased it the cost was $7000 per gram. Within a few years, helium-3 is expected to go to $30,000 per gram. “That is going to put us at the university out of business,” said Kulcinski. However, there is still enthusiasm for the project from those in the scientific community.
The group at the UW-Madison is currently the only ones in the world doing He3-He3 reaction research. The research is paid for almost completely through private funding. Two individuals in particular, Dave Grainger and the late Wilson Greatbach, have made significant contributions. According to Kulcinski, “We couldn’t do this research if we didn’t have Dave Grainger or Wilson Greatbach. Neither of them wanted any publicity or anything back. They just wanted to support students doing far out work and stretching their minds.”