In Spider-Man 2, Dr. Otto Octavius builds a fusion reactor that runs on tritium fuel, hoping to provide a source of renewable energy. The tritium in the reactor can only be handled with artificially intelligent robotic arms, which Otto claims he has complete control over. Of course, since it’s a Marvel movie, something goes wrong, the reactor gets out of control, and Dr. Octavius ends up becoming the villain Doc Ock. (Seriously, what is with science and safety protocols in the Marvel Universe?)
Unlike other Marvel substances such as vibranium and adamantium, tritium is found here in the real world. Tritium is just another name for hydrogen-3 (also written as 3H or T) a radioactive isotope of hydrogen. It contains one proton and two neutrons and has a half-life of 12.33 years, undergoing beta decay to turn into helium-3. Only trace amounts of tritium are found in nature. In fact, 99.9885% of natural hydrogen is made up of protium (hydrogen-1, or 1H), which has a single proton and no neutrons. The remaining 0.0115% of natural hydrogen is made of deuterium (hydrogen-2, also written as 2H or D), which has one proton and one neutron. Both protium and deuterium are considered stable. The amount of tritium in nature is so small that it doesn’t even register in the typical abundance charts.
Natural tritium is produced by the interaction of atmospheric particles with cosmic rays, high energy particles that come from space. A cosmic-ray neutron hitting nitrogen-14 in the atmosphere can create tritium and carbon-12. A cosmic-ray deuterium and another deuterium give protium and tritium.
Tritium is also produced in several “man-made” methods, particularly with nuclear reactors. Typical nuclear power today relies on the splitting of uranium-235. When hit with a neutron, the uranium-235 fissions or splits into fragments and particles, releasing energy. Neutrons produced from this fission can go on to hit other uranium-235 nuclei, causing them to split and sustaining the chain reaction to generate power.
While the actual splitting of uranium-235 can release tritium, the neutrons released may interact with other reactor system parts to create tritium. Coolants, used to remove heat from the reactor core, contain components than may absorb neutrons. For example, lithium is sometimes used in coolant. Lithium-6, which makes up about 7.6% of the natural lithium used in coolant, can absorb a lower energy neutron and break into helium-4 and tritium. Lithium-7, with 92.4% abundance, can absorb a higher energy neutron and break into tritium, helium-4, and a lower energy neutron. Another coolant used is heavy water, which is composed of deuterium instead of protium (D2O instead of H2O). As the heavy water is bombarded with neutrons, the deuterium sometimes picks up an extra neutron, creating tritiated or super-heavy water (T2O). Boron, a good neutron absorber, is used as a coolant or in control rods to help control the chain reaction in the fission process. Boron-10 can absorb a neutron and split into two helium-4 and one tritium.
Basically, there are lots of methods to make tritium. But how much tritium is there? According to Dr. Octavius, tritium is incredibly rare. “There’s only 25 pounds of it on the whole planet,” he claims. Is this true?
The short answer is “no.” Let’s ignore tritium found in the environment and focus on tritium produced by reactors or in the lab. In 2003, Dr. Scott Willms, from Los Alamos National Laboratory and the Tritium Plant Section Leader at ITER Organization, stated that there was approximately 18.5 kilograms of tritium “on hand” from the Darlington Tritium Removal Facility, which separates tritium out from heavy water coolant. That 18.5 kilograms of tritium translates just over 40 pounds- more than the 25 pounds of tritium Dr. Octavius claims. Spider-Man 2 came out in 2004, only one year after Dr. Willms report. Even if we account for one year of decay and assume that no more tritium was recovered, that would still leave us with about 38.5 pounds of tritium in 2004.
In 1996, a report from the Institute of Energy and Environmental Research estimated that a total of 225 kilograms (496 pounds) was produced in the U.S. from 1955 up until that point, and approximately 75 kilograms (165 pounds) remained. Once again, even with taking into account the decay of this tritium, they would have been left with about 105 pounds of tritium in 2004 (or almost 54 pounds of tritium in 2016).
And remember, these numbers represent only some of the man-mad tritium on Earth. There are other man-made sources and facilities, plus the natural tritium found on land and in the ocean and atmosphere.
Still, tritium is pretty expensive, costing around $30,000 per gram, or $850,000 per ounce. It’s not surprising that Dr. Octavius needed Oscorp Industries to fund his project. Despite the high cost, tritium is used for monitoring biological processes through radiolabeling, boosting the efficiency of nuclear weapons, and illuminating watch dials, emergency exit signs, and gun sights.
Oh, and if anyone was curious, researchers are already looking into using deuterium-tritium fuel for future fusion reactors. No word yet on whether artificially intelligent robotic arms will be required.
Keep calm and science on.