thulium-170

chemical isotope

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 19, 2026

Quick Summary

Thulium-170 is a radioactive isotope of thulium, a rare-earth metal. Natural thulium consists of the stable isotope thulium-169. When bombarded with neutrons, thulium becomes radioactive thulium-170, which emits soft gamma radiation. This property makes thulium-170 useful in small, portable X-ray sources for medical imaging and for non-destructive evaluation of thin-walled structures. Thulium itself is a silvery-white metal, stable in air but soluble in diluted acids. It was discovered in 1879 and is found in small amounts in rare-earth minerals. Thulium is one of the rarest rare-earth elements.1

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

thulium
…neutrons, natural thulium becomes radioactive thulium-170 (128.6-day half-life), which ejects soft gamma radiation with wavelength commensurate with laboratory hard X-ray sources. Only one allotropic (structural) form is known for thulium. The element adopts a close-packed hexagonal structure with a = 3.5375 Å and c = 5.5540 Å at room temperature.
Read More
…neutrons, natural thulium becomes radioactive thulium-170 (128.6-day half-life), which ejects soft gamma radiation with wavelength commensurate with laboratory hard X-ray sources. Only one allotropic (structural) form is known for thulium. The element adopts a close-packed hexagonal structure with a = 3.5375 Å and c = 5.5540 Å at room temperature.
Read More