Polonium-210 (Po-210) is a specialized, artificially produced isotope used in technology and industry. This radioactive element has an extremely short half-life of approximately 138 days, meaning its radioactivity decreases by half in just over four and a half months. Po-210 is a virtually pure alpha emitter, releasing energetic alpha particles as it decays to stable lead-206. This intense decay rate generates a massive amount of heat; one gram of Po-210 produces about 140 watts of thermal power. This unique combination of intense alpha emission and high power density makes polonium-210 useful for specific applications.
Powering Remote Devices
The ability of polonium-210 to produce significant thermal energy from a small mass makes it a suitable heat source for powering remote systems. This application is realized through a device called a Radioisotope Thermoelectric Generator, or RTG. In an RTG, the heat generated by the isotope’s decay is converted directly into electrical power using an array of thermocouples, which exploit the Seebeck effect.
Polonium-210 possesses a specific power of 144 watts per gram, significantly greater than the approximately 0.56 watts per gram generated by Plutonium-238, the standard RTG fuel. This high power density means a polonium-fueled generator can be significantly lighter and more compact than one using other isotopes for the same power output. The isotope was historically used for short-duration space missions and specialized terrestrial equipment where minimizing mass was a top priority.
A notable historical use was in the Soviet Union’s Lunokhod lunar rovers, which utilized Po-210 heat sources to keep internal components warm during the frigid lunar nights. Its short half-life makes polonium-210 unsuitable for long-term missions, such as deep-space probes that require decades of operation. Consequently, its use in space-based RTGs has been largely phased out in favor of longer-lived isotopes.
Controlling Static Electricity in Industry
Polonium-210 leverages its alpha-particle emission to neutralize unwanted electrical charges. In industrial processes, static electricity can be a serious problem, causing materials to cling together, attracting dust, or creating sparks that pose a fire hazard. Polonium sources are incorporated into devices known as static eliminators to mitigate these effects.
The alpha particles emitted by the polonium source travel a short distance through the air, colliding with and stripping electrons from the air molecules. This process, called ionization, creates a localized cloud of both positive and negative ions. These ions are then naturally attracted to and neutralize any static charge present on nearby surfaces, such as films, plastics, or textiles.
This system is effective because the polonium source requires no external power to function. It provides a constant stream of ionizing particles for neutralization in sensitive environments, such as those involved in the manufacture of photographic film, plastic sheeting, and synthetic fibers.
Smaller, consumer-grade versions are also used in brushes to eliminate static and remove dust from camera lenses or photographic negatives. Static eliminators typically contain a small, sealed amount of polonium-210, often electroplated onto a foil, which must be replaced periodically due to the isotope’s short half-life.
Role in Research and Neutron Sources
Polonium-210 is used to create compact, transportable neutron sources for various scientific and industrial purposes. This application involves mixing the alpha-emitting polonium with a light element, most commonly beryllium, to create a Po-Be source. When the energetic alpha particles strike the beryllium nuclei, they induce a nuclear reaction that results in the emission of neutrons.
This is known as an alpha-neutron reaction, which provides a reliable and continuous source of neutrons without the need for a nuclear reactor or a particle accelerator. The resulting neutron sources are compact and highly useful for the calibration of radiation detection instruments in laboratories and industrial settings. Historically, these sources were used as initiators, or “triggers,” in certain nuclear weapons to guarantee the start of a fission chain reaction.
Beyond neutron generation, polonium-210 serves a function in biological and environmental research as a tracer. Its pure alpha signature makes it highly detectable in very small quantities, allowing scientists to track its distribution and behavior in natural systems. This capability aids in understanding the movement of polonium, such as its presence in the natural decay chain of uranium and its concentration in environmental pathways.