Here is a riddle for you: It’s splitting Africa into two parts; could cause a crisis in diagnostic medicine; enlivens parties in the western world; and is a creative prop for cartoonists. Hint: The substance I’m referring to is produced in the Sun and other stars, as well as in Earth’s interior. Geologically, it is associated with natural gas, but costs 40 times more commercially. The answer, if you haven’t guessed, is “helium”—family-head of the noble gasses, among which are also neon, krypton, argon, xenon and radon. Despite its distinguished chemical lineage though, “helium” is hardly a household word. Poets and lyricists have left it for columns like this one. Nor are the ins-and-outs of “He-3” or “He-4” debated in pubs, or other public places. But helium’s profile, in international discourse, is rising: Due in no small way, to a deepening production crisis, a spiraling political and economic conundrum that is ensnaring policy makers in both industrialized and developing nations. Increasingly, this unsung industrial resource is inducing anxiety, because some scientists believe planetary reserves will have exhausted in 25 to 30 years—disrupting helium-dependent industries and professions, such as space, medicine, metallurgy, health and lighter-than-air flight. A countervailing contention though, is that Earth’s reserves are quite adequate, if only world helium policy was more rational. Exponents point to large deposits of helium-rich natural gas in Russia, Poland, China, the Middle East, Africa and North America. The conundrum stems partly from contrasting cosmic and terrestrial abundances. Helium is at once the second most plentiful element in the universe, after hydrogen—and one of the scarcest material substances on Earth. Cosmically, helium makes up 23 to 25 percent of normal matter. All but a tiny portion of this is primordial, having been synthesized during the first few minutes after the Big Bang conflagration, 13.8 billion year ago. The rest (one per cent or so) is the result of nuclear fusion in main sequence stars, like our Sun. Stars generate the energy our eyes sense as “light,” by combining four hydrogen nuclei into a nucleus of helium—two protons and two neutrons. Earth contains no cosmic helium. Over the past 4.6 billion years, all has drifted off into space. Helium being “2” on the periodic table, only one substance is lighter—hydrogen. Helium thus finds it easy, to escape Earth’s gravity. What is more, the element’s two protons and two neutrons actually occupy less space than a normal hydrogen atom—which has only one proton and an electron. Consequently, helium atoms can squeeze through openings in rocks that are too tight, even for hydrogen! So they seep to the surface and rise. Where, then, does the helium associated with natural gas come from? Geologists and geochemists believe present terrestrial stocks formed over many millions of years, deep in Earth’s mantle, through a process called radioactive decay. “Radioactive decay” occurs when an isotope (neutron configuration) of a particular element, has an unstable nucleus. Such nuclei seek stability by spontaneously transforming themselves. In this case, thorium-232 and uranium-238 (primarily) radiate “alpha particles”—another name for helium nuclei. “Most of the helium that is removed from natural gas,” writes Hobart King, in Geology.Com, “is thought to form from the radioactive decay of uranium and thorium in granitoid rocks of Earth’s continental crust. As a very light gas it is buoyant and seeks to move upward as soon as it forms. “When it… starts moving upward,” King continues, “it can fit through very small pore spaces within the rocks. Halite and anhydrite are the only sedimentary rocks that can block the upward migration of helium atoms. Shales [are]… a less effective barrier”. Investigators have identified three conditions, geologically, for the formation of exploitable helium reserves. First, the basement rock must be rich in uranium and/or thorium (whose decay creates helium nuclei). Secondly, the rock has to be faulted and fractured, so that the fissures function as flow channels. But the most important factor, says the Inter-American Corporation, which specializes in helium exploration and production, “is the presence of a cap rock or seal that is impermeable enough to withstand helium leakage. This is the primary reason why we do not see more helium fields…” Helium is being created continually beneath Earth’s surface. But, as King writes, in Geology.Com “its rate of natural production and accumulation is so slow that it must be considered a nonrenewable resource”. Actually, most of the world’s helium is not underground, but rather, wafting through the atmosphere—in a one-to-two million year escape gambit. The American Physical Society (APS) advises though, that the 700,000 billion cubic feet (BCF) of valuable space-bound fluid is too rarefied to exploit economically. Concurringly, Paul Lafleur, president of Canada’s Petro-Find Ltd, notes that “It is too expensive to separate helium from ambient air, because it contains only 5.4 ppm helium…” Even to tap terrestrial sources, he adds, is costly and technically taxing: “The high price of helium, which is about 40 times that of natural gas, relates to the expensive separation and purification processes required to achieve the desired high grades”. Helium is intermixed with methane (the most abundant natural gas) and other associated fluids—from which it needs to be separated. These include nitrogen, hydrogen, neon and argon. Each gas has a characteristic “boiling point,” below which it becomes a liquid. Separation entails progressively reducing the temperature, until only helium (which has the lowest boiling point of any element) remains gaseous. “There are two stages in isolation of helium from natural gas,” explains an Internet posting from Gazprom VNIIGAZ, Russia’s natural gas behemoth. “At stage one, the process of low-temperature condensation produces helium concentrate. The volume share of the target substance [i.e., helium] is at least 80 per cent in the product. Further on, helium concentrate gets cleaned from impurities – methane, nitrogen, hydrogen, neon and argon”. Helium’s rising strategic profile stems from its light weight, low boiling point (4 K, compared with hydrogen-20 K; nitrogen-77 K and oxygen-90 K) and legendary chemical stability. It’s the most unreactive of all the noble (inert) gases, except neon—and more widely used, commercially and industrially. “Helium is absolutely essential,” asserts APS, “to achieving the extremely cold temperatures required by many current and emerging technologies…”Currently, the greatest use of helium, is for cooling the superconducting magnets of hospital magnetic resonance imagers (MRI scanners)—which are gaining importance, as diagnostic tools. It also prevents magnets in particle accelerators, such as CERN’s Large Hadron Collider, from overheating. In fact, APS projects a future role for helium in rail transport systems, where high-speed magnetic levitation (MAGLEV) trains are already being introduced. These vehicles attain speeds of 500 km per hour, using superconducting magnets to rise off the track and eliminate friction. But this noble gas has mundane applications as well. Helium helps divers to breathe. Inert and lighter than air, it is also employed for atmospheric lifting: Whether it is raising party balloons to the ceiling, buoying up weather and research craft or floating giant cargo-carrying airships. Because of its chemical stability and extreme cryogenic properties, space agencies use helium to purge hydrogen, oxygen and other gases from the fuel tanks of their rockets. During the Space Shuttle era, Karen H. Kaplan wrote in PhysicsToday.Org, that NASA used a million cubic feet for every launch.
