It sounds ridiculous to think that something used everyday in birthday parties is in a serious shortage, but helium, an element used in applications ranging from balloons to MRI scanners, is now getting very difficult to find. That means that very soon, your cousin may have a very disappointing birthday party. Yet that is the least of our problems.
The most surprising thing about this shortage is that helium is the second most abundant element in our universe. However, most of this helium is, practically speaking, way out of our reach. Let’s embark on an exploration of helium to see why it is so hard to find, what Helium does for us, and what we can do in the future to make the search for it a little easier.
The main trouble that arises when trying to obtain helium is that it’s less dense than air. This means that any helium trapped under the Earth’s surface eventually diffuses into the atmosphere. Once it’s in the air, it’s out of reach; we have yet to create a feasible means of collecting all of this diffused helium. Currently, a huge build-up of Helium-4 (He-4) is being released in Yellowstone and about 60 tons of helium are released every year. Some of this helium is diluted into the atmosphere, but the rest of it escapes the atmosphere into space. Although it seems like we are letting this helium go to waste, there is just simply no viable way to collect it.
Yellowstone National Park
Yet there are other factors that contribute to Helium’s shortage. For one, the production of Helium as a by-product of nuclear decay is not a heavily invested means of production. This is largely because it is not an economically viable option (along with capturing the diffused Helium in the air as mentioned before); however as we will see, the value of Helium just may be priceless. Another factor contributing to the shortage is the fact that in the past few decades, the demand and use of Helium has skyrocketed, largely ascribed to our squandering ways. With a limited amount, prices of Helium have soared as well.
So why exactly is helium important anyway? Helium has a multitude of applications, but its main application is its use to cool superconducting magnets in MRI (magnetic resonance imaging) scanners. Superconducting magnets are magnets that can produce immense magnetic fields, which MRI scanners require to operate and use to construct images of the body. MRIs use superconducting magnets because below a certain temperature, known as a critical temperature, a metal loses its resistance (The reason this happens at low temperatures is because there are lower energy and less frequent atomic collisions). This temperature needed for superconductivity requires cryogenic temperatures. That’s where helium comes in. Liquid helium, due to its extremely low (4.2 K) boiling point and high thermal conductivity, is very efficient at capturing heat and is the only medium that can induce superconductivity in metal alloys. In MRI scanners, the wires are bathed in liquid helium at -269.1 °C to capture heat and remove it from the system. This effectively removes the wires’ resistance and allows them to become superconductors. However, a normal MRI scanner uses 1,700 liters of helium which periodically has to be changed. This is a huge amount of helium, especially with the impending shortage. A new method of superconductor cooling was recently developed by a company known as Cryogenic. This method uses a significantly lower amount of helium and may soon significantly reduce the amounts of helium that we waste.
Another important application of helium is its use in oxygen tanks for underwater diving. Normally air is comprised of approximately 20% oxygen gas and 80% nitrogen gas. Nitrogen gas is a lot more soluble than Helium, and is especially soluble at high pressures – which essentially keeps the gases in solution. The difference in solubility between the two plays a key role in why Helium is used, and is due to their difference in size. In order to dissolve any substance into a solvent, the solute and solvent must have interactions with one another. For non-polar gases like N2 and He, it becomes difficult to create the interactions with polar water molecules. To actually bring one of these gases into solution, an induced dipole must be created in the gas. An induced dipole becomes increasingly easier as the molar mass of the substance increases. This is because there are then more electrons to shift between the atoms thereby creating a strong bond between the solute and solvent. Between N2 and He, nitrogen gas clearly dominates in molar mass and strength of LDF forces. So at these high pressures below the water, the nitrogen gas becomes highly soluble in the bloodstream inducing nitrogen narcosis, a state with similar effects to those of alcohol. Furthermore, as divers begin to rise from the water, the solubility of nitrogen decreases and begin to bubble out of solution (the blood). This is extremely dangerous as it can create bubbles in the bloodstream which wouldn’t be able to pass through fine capillaries in the body. The condition, called the Bends, is life threatening. To prevent this from happening, Helium is used. As stated previously, Helium is less soluble than Nitrogen, so less Helium would get into the bloodstream. Furthermore, Helium is an inert gas, so its narcotic properties are negligible and do not pose any problems of toxicity like Nitrogen does. Helium continues to be the most ideal gas for diving tanks, and the shortage poses a serious threat to the maritime industries.
With such versatility it seems more likely that the United States will take on currently, non-viable means to produce Helium rather than drastically cut down on usage. There will likely be 3 primary sources that will serve the United States in the future as a source of Helium. As stated before the first source would be through nuclear reactions. One reaction that results in a formation of a helium atom is plutonium decomposition (Pu-239). A plutonium nucleus decays into an alpha particle and a uranium nucleus. The alpha particle immediately captures 2 electrons from the nearby plutonium metal and becomes a helium atom in the midst of a plutonium lattice. There are 2 main problems with this method of producing helium. Firstly, this process has a half-life of 24,100 years. Using the half-life formula for first-order reactions, one could calculate k to be (ln2)/t1/2 = (ln2)/24,100= 2.88 x 10-5. Using the first-order integrated rate law, one could determine that in a year, 10,000 g of plutonium will decompose to 10,000 x e-2.88×10^-5 = 9,999.71 g. Therefore, in a year, 10,000 g of plutonium will only decompose to 0.29 g of decay. That’s a measly 0.0029% decay after an entire year. This makes generating a profitable amount of helium unfeasible to say the least. The second problem with this method is that once the helium is produced, it is stuck in the plutonium lattice. This makes it become very difficult to isolate and extract
The second source is actually through natural gas. Some natural gas contains amounts of Helium that can be extracted through a complicated process. The reason it is not widely used today is because the extraction process requires strict criteria and many samples of natural gas only contain about 0.3-1.9 percent Helium by volume. Furthermore, there are many economic considerations before uptaking such a project as the extraction process requires facilities. However, in essence there are 3 steps to the extraction process. The first step is to remove the impurities from the natural gas such as water, carbon dioxide and hydrogen sulfide through means such as amine and glycol adsorption. The second step is to extract the high molecular-weight hydrocarbons. Finally, through cryogenic processing the remaining methane gas is extracted. This works because Helium has the lowest freezing point of any element. So as the temperature is sufficiently reduced, all other substances will freeze and can be filtered out. What’s left is crude Helium, containing approximately 50-70% Helium and the rest is Nitrogen gas and other traces of gases. To further purify the Helium to approximately 99.99% purity, Pressure-Swing Adsorption (PSA) is used. PSA separates different gases from each other based on the premise that each gas has a different affinity for different adsorbent materials, and have different vapor pressures. Due to the varying vapor pressures, one gas can be completely transformed into the gas phase at one temperature and pressure and then extracted, while the other gas would remain largely as a liquid.
Pressure Swing Absorption Process
The final source will actually be where Helium is most abundant: outer space. Observations from lunar missions have concluded that there are about 22 grams of helium in every cubic meter of lunar soil. In the future, if Helium were to ever run dry on Earth, this alternative would likely create a madman’s dash to the Moon in search of this precious yet scarce gas.
In essence, our lavish uses of Helium without a steady state of supply has caused a shortage that affects many scientific disciplines that rely on the unique characteristics of Helium. As a human race, we must either cut down on our uses of Helium in some shape or form, or begin taking measures to create more Helium for use in the future. Without Helium, many of the opportunities and technology today will float adrift tomorrow, just an arm’s length away from humanity’s struggling grasp for the resources we use so plentifully.