Promethium is a chemical element with the symbol Pm and atomic number 61.
- Most promethium is used only for research purposes, except for promethium-147, which can be found outside laboratories. It is obtained as the oxide or chloride, in milligram quantities.This isotope does not emit gamma rays, and its radiation has a relatively small penetration depth in matter and a relatively long half-life.
Some signal lights use a luminous paint, containing a phosphor that absorbs the beta radiation emitted by promethium-147 and emits light. This isotope does not cause aging of the phosphor, as alpha emitters do, and therefore the light emission is stable for a few years. Originally, radium-226 was used for the purpose, but it was later replaced by promethium-147 and tritium (hydrogen-3). Promethium may be favored over tritium for nuclear safety reasons.
In atomic batteries, the beta particles emitted by promethium-147 are converted into electric current by sandwiching a small promethium source between two semiconductor plates. These batteries have a useful lifetime of about five years. The first promethium-based battery was assembled in 1964 and generated “a few milliwatts of power from a volume of about 2 cubic inches, including shielding”.
Promethium is also used to measure the thickness of materials by evaluating the amount of radiation from a promethium source that passes through the sample. It has possible future uses in portable X-ray sources, and as auxiliary heat or power sources for space probes and satellites(although the alpha emitter plutonium-238 has become standard for most space-exploration-related uses)
- The element, like other lanthanides, has no biological role. Promethium-147 can emit X-rays during its beta decay, which are dangerous for all lifeforms. Interactions with tiny quantities of promethium-147 are not hazardous if certain precautions are observed. In general, gloves, footwear covers, safety glasses, and an outer layer of easily removed protective clothing should be used.
It is not known what human organs are affected by interaction with promethium; a possible candidate is the bone tissues. Sealed promethium-147 is not dangerous. However, if the packaging is damaged, then promethium becomes dangerous to the environment and humans. If radioactive contamination is found, the contaminated area should be washed with water and soap, but, even though promethium mainly affects the skin, the skin should not be abraded. If a promethium leak is found, the area should be identified as hazardous and evacuated, and emergency services must be contacted. No dangers from promethium aside from the radioactivity are known.
Source: Wikipedia, https://en.wikipedia.org/wiki/Promethium#Applications