Today I want to show you an element that made the use of radium 226 in paint absolute! Let’s take a closer look at Hydrogen 3 or better known as Tritium!
Tritium is a radioactive isotope of Hydrogen with 2 neutrons which makes it unstable and thus radioactive. It was first discovered in 1934 by a group of three scientists, Ernest Rutherford, Mark Oliphant and Paul Harteck who have bombarded deuterium with high-energy deuterons which resulted in the creation of Tritium.
Today, Tritium is most often produced in nuclear reactors by neutron activation of Lithium-6. As a result, Lithium turns into Helium and Tritium
Tritium has a half-life of 12.32 years and it decays by beta radiation (5.7keV) and in the process, it also releases a gamma-ray (18.6keV). Since the energy of both beta and gamma radiation is so low, tritium can be safely used in consumer products.
Radiation coming from the Tritium marker isn’t directly caused by the Tritium itself. The beta particles don’t have enough energy to pass through the plastic and are stoped by it. This however causes Bremsstrahlung (X-Rays) which is then detected by the Geiger counter.
Until the 1960s, many watch manufactures used Radium paint in order to make the dials glow in the dark. However, Radium 226 is very dangerous and because of this it was banned and was replaced by Tritium which has similar radio-luminescence properties but is much safer to use.
The most common use for Tritium is in the production of radio-luminescent markers that are used in watches, gun sights. and emergency exit signs. The radio-luminescence is achieved by coating the Tritium vial with a layer of phosphor from the inside. When beta particles hit phosphor, they cause it to fluoresce releasing visible light.
Since Tritium has a half-life of 12.32 years, these markers will remain glowing for over 10 years depending on how much tritium there is in them.
Tritium can also be used as a nuclear battery generating electricity by converting energy from beta radiation. Many scientists claim that this technology is the future for deep space exploration where sunlight is too weak to generate enough electricity to power a spacecraft.
The MARS 2020 Perseverance rover already runs on a similar kind of battery which uses Plutonium 238 and I am sure that we will see more nuclear batteries in the future!